Continental Shelves during the Last Glacial Cycle: Knowledge and Applications
Fourth IGCP 464 Annual Conference
28/8 - 3/9 2004 Roma and Ponza Island, Italy
| DAY ONE, Saturday 28
Museum of Mineralogy, Università "La Sapienza", P. Aldo Moro 5
| DAY TWO, Sunday 29 August 2004,
Rome - La Sapienza Conference Hall
09.30 Welcome to delegates; official opening of the annual IGCP464 meeting.
SESSION 1 Shelf response to climatic eustatic oceanographic changes during last glacial cycle.
Chairman: Allan Chivas - Un. of Wollongong, Australia
Sea level changes in the Maldives with respect to multiple interacting parameters.®
Multiproxy evidence of late glacial to Holocene and of Sangamonian millenial-to seasonal-scale climatic oscillations in the St.
Lawrence estuary, eastern Canada. ®
St-Onge G., de Vernal A., Hillaire-Marcel C., Long B., Duchesne M
|10.50||Pearl river estuary related sediments as response to Holocene climate change and anthropogenic impact – project pecai. ®|
|Zhou D., Harff J|
SESSION 1 (continuation)
Chairman: Natalia Patyk-Kara Russian Academy of Sciences
|11.30||The role of the meandering of Brazil current in the sedimentation of the outer shelf-upper slope off southeastern Brazil under|
|different climatic conditions: sedimentological data and a numerical modelling approach. ®|
|De Mahiques M. M., Calado L., Almeida da Silveira I. C., França Lima A.|
|11.50||The Holocene highstand systems tract in the gulf of Cadiz shelf, NE Atlantic ocean: a record of oceanographic forcing and|
|recent environmental changes. ®|
|Lobo F. J., Fernández-Salas L. M:, Hernández-Molina F. J., González R., Dias J. M., Díaz del Río V.|
|12.10||Session 1 Discussion|
SESSION 2 Record of environmental changes on the shelves of the world since LGM .
Chairman: Gilles Lericolais, IFREMER, France
|14:10||Geographic change in Atlantic Canada from L.G.M. to the Present. ®|
|14.30||Geomorphological, deposition and foraminiferal indicators of late Quaternary tectonic uplift in Iskenderun Bay, Turkey. ®|
|Yanko-Hombach V., Koral H., Av_ar N., Motnenko I., McGann M|
|14.50||Coastal-marine processes and sediment supply during the post-LGM transgression in the northern part of the Argentine|
|Continental Shelf. ®|
|Violante R. A.|
|15.10||Mineral resources of the Russian Arctic shelf under last glacial maximum conditions. ®|
|Alekseev M. N., Patyk-Kara N. G., Drouchits V. A.|
|15.30||Mineral resources of the Russian Arctic shelf under last glacial maximum conditions. ®|
|Alekseev M. N., Patyk-Kara N. G., Drouchits V. A.|
SESSION 2 (continuation)
Chairman: Renèe Hetherington Un. Of Victoria, Canada
|16.30||Effect of different delta types on shelf, continental slope and deep-sea sedimentary architecture genesis in a relative-sea-level|
|fall/lowstand context: examples from the Manicougan deltaic prism, Canada. ®|
|Duchesne M. J., Long B. F.|
|16.50||Ground-truthing of boomer seismic profiles in Tai o Bay, Hong Kong SAR, China. ®|
|Yim S. W. W., Wong H. K., Chan L. S., Lüdmann, Ridley Thomas W. N.|
|17.10||Carbonate sediments and coral reefs of Australia's Western Margin. ®|
|17.30||Session 2 Discussion|
|19.00||Conference dinner and concert. Cloister of S.Clemente al Celio (12th cent.), Via dei Querceti, Rome|
|DAY THREE Monday 30 August 2004, Rome - La Sapienza
3 Shelf evolution since LGM and its influence on human cultures.
Chairman: Lindsay Collins, Curtin University, Perth, Australia
09.30 Preservation of coastal landscapes during the Holocene transgression, Bras D' Or Lakes, Nova Scotia. ®
Shaw J., Taylor R.B
Climate of the Last Glacial Cycle and
the Peopling of the Americas. ®
Hetherington R., Montenegro Neto A., Weaver A., Eby M., Wiebe E.
Continental shelf evolution
during the last glacial cycle-influence on human culture. ®
Was the last rapid sea change in the
Black Sea linked to a catastrophic event 7500 years ago? ®
Lericolais G., Popescu I., Panin N., Guichard F., Popescu S
The Black Sea flood controversy
in light of the Late Quaternary history of the Black Sea. ®
Session 3 Discussion
SESSION 4 Geology of Western Pontine Islands.
Chairman: Wyss Yim University of Hong Kong, China
Palmarola: Prehistoic obsidian
Volcanic activity and geodynamic setting
of the western Pontine Islands. ®
Conte A.M., Dolfi D.
5 Geology of W Pontine Continental Shelf.
Chairman: Francesco L. Chiocci, Un. of Rome , Italy
Geological characters and evolution
since LGM of Western Pontine continental shelf (Tyrrhenian Sea).®
Martorelli E., Altobelli C., Chiocci F. L., D’Angelo S.
Temperate carbonate sedimentation
of Pontine Islands continental shelf (Central Tyrrhenian
Sea, Italy) in comparison with W Australia
Altobelli C., Collins L.
14.30 The carbonate sedimentation in the Pontine shelf: facies, controlling factors and record of the events. ®
Brandano M., Civitelli G., Veneziano P.
The "Atlas of Submerged Depositional
Terraces along the Italian coasts". ®
Chiocci F.L., D'Angelo S., Romagnoli C.
Posters on Geology
of W Pontine Continental Shelf (5 minutes presentation)
15.50 Session 4 and 5 Discussion
Final business meeting
|DAY FOUR, Tuesday 31 August 2004
Transfer from Rome to Ponza Island
Free afternoon in Ponza.
|DAY FIVE, Wednesday 1 September 2004,
Group 1 start fieldtrip on small
Group 2 start fieldtrip on oceanographic vessel (R/V Universitatis)
Fieldtrip dinner Frontone Beach
|DAY SIX, Thursday 2 September 2004,
Group 2 start fieldtrip
on small boat
Group 1 start fieldtrip on oceanographic vessel (R/V Universitatis)
|DAY SEVEN, Friday 3 September 2004
Morning: transfer from Ponza Island to Rome
end of fieldtrip at Termini train station in Rome
LIST OF POSTER PAPERS
Minutes and notes of the FOURTH Annual IGCP-464 Meeting.
Three business meetings were held during the 4th annual conference; the first two in Rome (on the afternoon of Aug.29 and on the late afternoon of Aug.30) and the final one on the evening of Sept. 1 in Ponza.
The main topics discusses are the followings:
|The offer to
held the final annual conference in St. Petersbusrg made by Natalia
Patyk.Cara was accepted. The annual conference will be held jointly
with a conference on mineral resources of the shelves. There will be
dedicated session to general subjects dealing with continental shelves
and two field trips.
A IGCP464 session has been organized by R.Violante within the Argentina National geological Congress in Sept.05; a workshop in Visakhapatnam (India) will be organized by M. Faruque (India Geological Survey); Prof. Wyss Yim will organize in May a joint INQUA, PAGES and IGCP-464 meeting with field trips entitled : Sub-aerially exposed continental shelves since the Middle Pleistocene climatic transition.
|End of project book(s)
has been deepened in all the three meetings. The idea of having two
books is always on the table, even if the time is very short to have
the books ready by the end of the project. However an offer made by Russian
Academy of Science to massively participate to the two books let the
project to be faisible, so that the presents gave to the project leaders
the task to complete the list of contributors with specialist outside
the IGCP464 participants.
The two monographs will be on Continental Shelves of the World. Vol. 1 Data acquisition methods, interpretation and applications, and Vol. 2 Shelves of the World. These books will have multi-authored chapters (~ 20 chapters per volume) and synthesize and offer new data to form a comprehensive statement of our understanding of continental shelves. We have negotiated publication procedures with the Geological Society of London, in its role as the vehicle for IUGS publications
| Follow-up project
|The idea of having
a successor project is more and more agreed by the majority of the
participants. The reason of such a choice are: 1) to not dissipate the
community of researchers, researches, initiatives that grew-up from the
project during the years. 2) the good results achieved with meetings and
short course given during the years ; 3) the presence of very active participants
that may guarantee the vitality of a follow-up project.
The possible follow-up project could be aimed to set-up scenarios for future evolution of the shelf, to emphasize the effects of recent shelf evolution on human development, i.e. one of the most successful themes dealt by IGCP464. Titles have been proposed such as “Effects of emerging/submerging shelves on human development/risk/resource management”(Mörner), “Global changes recorded in continental shelves” (Lericolais), “Non living resources, record of climate/environmental changes, and geological risks on continental shelves” (De Maquies). The identification of possible leaders was also discussed, and it was decided that they: 1) should have been active on the past project, 2) possibly working in different scientific fields 3) be from different countries and “cultural areas” (anglosaxon, eastern, european,….) with special attention to developing countries 4) be enough free from other commitments to fulfil the successor project.
RHODOLITH FACIES DEVELOPMENT DURING THE HOLOCENE
SEA LEVEL RISE AT THE PONTIAN ISLANDS SHELFBREAK
Basso D., Corselli C., Morbioli C.
Univ. Milano-Bicocca, Dip.to Sc. Geologiche e Geotecnologie, Piazza della Scienza 4, 20126 Milano
After the Last Glacial Maximum, the Tyrrhenian sea level raised until the present position at different rates, alternating periods of fast rise and low rise or standing (Lambeck and Bard, 2000). This paper is aimed to the reconstruction of the benthic environment which existed at the Pontian Islands shelfbreak about 10 ka BP and to follow its evolution during the deepening towards the present condition.
Four gravity cores (GRC02, GRC03, GRC 04 and GRC06, Table 1) were recovered at depth ranging from 111 to 157 m of water depth, in the framework of the TSM multidisciplinary project (Taphonomy and Sedimentology on the Mediterranean shelf).
On the basis of the main changes in colour and sediment texture, several core intervals were identified. Grain size analyses were performed by wet sieving. The fossil assemblage was extracted by manual picking, after sieving each sample on 1 mm mesh. Molluscs and brachiopods were identified at species level and counted. Calcareous algae were embedded in resin for the preparation of thin sections (ground sections) and identified under optical microscope. A multivariate statistical analysis of the molluscan associations observed in the different levels of the four cores was performed with PRIMER (Plymouth Marine Laboratory).
AMS dating of biogenic remains collected at the bottom of the four cores (from 78 to 88 cm below sea-floor) provided ages ranging from 10040 to 10380 yrs BP (Conventional 14C age, ANSTO Physics Division, Menai, Australia, Table 1).
All four cores show a transition from basal, biodetritic, muddy-gravelly sand with a variable amount of rhodoliths to silty sand or sandy mud without coralline algae. The largest rhodoliths (max. diam. 8 cm) and their maximum abundance occur in the basal intervals of cores GC04 and GC06. These large rhodoliths have a boxwork internal structure and a multispecific composition (Basso, 1998). Upcore, the boxwork rhodoliths are substituted by laminar/concentric rhodoliths with few protuberances. In the most recent core intervals coralline algae occur as thin encrustation on bryozoan colonies. The molluscan fossil assemblage at the base of all cores is referable to different aspects of the Coastal Detritic Biocoenosis (DC; Pérès et Picard, 1964), with a group of Coralligenous-related species linked to the occurrence of rhodoliths. The paleobiotope deepening is well recorded in cores GC02 and GC03 by the upcore increase of bathyal, mud-related mollusks.
The observed molluscan associations and rhodolith abundance, shape and composition are ecologically compatible with the embedding sediments. They testify of the transition from the circalittoral DC Biocoenosis (rhodolith facies), dated at about 10000 yrs BP at the cores bottom, through DC-DL (Détritique du Large) Biocoenoses to the present-day biotopes, located between the lower Circalittoral and the upper Bathyal zones.
Water depth (m) Recovery (cm) Age 14C
GC02 157 m 88 cm 78 cm - 10310±40
GC03 129 m 89 cm 88 cm - 10380±50
GC04 127 m 89 cm 88 cm - 10380±50
GC06 111 m 85 cm 84 cm - 10040±50
Table 1. Water depth, recovery and AMS radiocarbon dating of the studied cores
Basso, D. (1998) Deep rhodolith distribution in the Pontian Islands, Italy: a model for the paleoecology of a temperate sea. Pal. Pal. Pal., 137: 173-187.
Lambeck, K., Bard, E. (2000) Sea-level change along the French Mediterranean coast for the past 30000 years. Earth and Plan. Sci. Lett., 175: 203-222.
Pérès, J.M., Picard, J. (1964) Nouveau manuel de bionomie benthique de la Mer Méditerranée. Rec. trav. stat. Mar. Endoume, 31 (47): 5-138.
THE CARBONATE SEDIMENTATION IN
THE PONTINIAN SHELF: FACIES, CONTROLLING FACTOR AND RECORD OF THE EVENTS
Marco Brandano, Giacomo Civitelli & Pietro Veneziano
Dipartimento di Sciernze della Terra, Università di Roma “La Sapienza”, P. A. Moro 5
In order to individuate the record of Holocenic events and the controlling factors of the present sedimentation in the Pontinian shelf, 33 selected sediment samples from the sea floor were analysed.
The samples are representative of six different sectors (Palmarola, PonzaW, PonzaNW, Ponza NE, Ponza E, Zannone) spaced on the shelf, in water depth ranging between –15 m and –250 m. The grain-size distribution indicates a dominance in the sand size range with a subordinate percentage of silt and gravel size. In the studied sectors of the shelf the grain-size distribution plotted against the bathymetry generally evidences a regular trend, nevertheless Eastward of Ponza the sediments are characterised by high percentage of silt if they are compared with samples coming from the others sectors in the same bathymetric range. Similarly the planktonic / benthonic foraminifera ratio shows a good correlation with increasing depth. A single anomaly is recorded again in the Eastward of Ponza.
The sedimentary components fall in the mixed carbonate-terrigenous hybrid sand. The range of CaCO3 content show a wide range and it was used to differentiate the biogenic and bioclastic fraction from the terrigenous one. The lowest CaCO3 content values(< 20%) are obtained for the samples collected in a water depth of less than –50 m, close the island shoreline, and subordinately (< 50%) for the samples collected from a water depth more than –100 m. The samples coming from the – 60 m and – 100 m interval show the highest CaCO3 content values (more than 80%) with the exception of samples collected Eastward of Ponza with a CaCO3 content values more than 30% in a bathymetric range of –50/-100 m.
The investigated sediments are characterized by bioerosion and glauconitic and phosphatic mineralization. The biorosion traces are related to carbonate grains, not following a bathymetric trend. On the contrary glaucony and phosphate are mainly restricted in a water depth ranging between -60 and -170 m. In particular mineralization is evident on the foraminifera belonging to the assemblages of the sea-grass meadows.
The obtained data suggest some considerations.
The carbonate factory is mainly represented by red algae, as well as in the modern Balearic platforms (Canals and Ballesteros, 1996).
The hydrodynamic condition appears to have an important role in controlling the sediment production and distribution, whose are strictly related to the productivity of carbonate factory. The evidence comes from the samples collected in the Eastern sector of Ponza representing an area characterised by lower energy, protected from the dominant winds (from W). At water depth between –50 and – 100m the sediments show high percentage of silt (more than 40%) and they are characterised by low carbonate content (less than 30%), suggesting a limited activity of the carbonate factory.
In the bathymetric interval between –50 and – 100m the coexistence of biota assemblages of the circalitoral zone, the main CaCO3 producer, and mineralised biota assemblages of infralitoral zone could represent the record of the last Holocene trasgressive event, expressed by the overlapping of circalitoral facies (Maerl) on infralitoral facies (sea-grass meadows facies).
Finally the modern sediments from Pontinian shelf are compared with similar facies characterising fossil deposits, in particular the Lower-Middle Miocene calcarenites of the Latium-Abruzzi platform (“Bryozoan and Lithothamnion Limestone” fm) and with Tortonian calcarenites of the coastal ridge of Northern Calabria.
Canals M. and Ballesteros E., 1996 – Production of carbonate particles be phytobentic communities on the Mallorca-Menorca shelf, nothrwestern Mediterranean Sea. Deep Sea Research II, Vol 44, N. 3-4, p. 611-629
THE “ATLAS OF SUBMERGED DEPOSITIONAL
TERRACES ALONG THE ITALIAN COASTS”: A CASE-HISTORY COLLECTION
F.L.Chiocci, S.D’Angelo*, C.Romagnoli
*(APAT- Italian Agency for Environment Protection and Technical Services – Department of Soil Protection)
A case-history collection was proposed some years ago within the Italian marine geology community. The features, object of the census, are sedimentary bodies outcropping on the seafloor at a shallow depth (generally within –150 metres), having a wedge-shaped geometry and a terraced morphology (thus defined “Submerged Depositional Terraces”, SDT, to differentiate them from fluvial and marine-coastal terraces). The adjective “depositional” was adopted to enhance the primary character of these bodies, originated by progradation and unmodified afterward by post-depositional erosion.
The contribution from the main Italian research groups led to the identification of depositional bodies with similar features in several margins of the Tyrrhenian Sea (mainly), Ionian Sea and Sicily Channel. The good results of the initiative and the editorial availability of the Italian Geological Survey (APAT-Italian Agency for Environment Protection and Technical Services), allowed the realisation of an “Atlas of Submerged Depositional Terraces along the Italian coasts”. This includes not only the compilation of the observed cases, but also a description and a mapping, as homogeneous as possible, of the main SDT morphologic and depositional features and a synthesis of the obtained knowledge on morphology, age and probable genesis of SDT.
The observed SDT have always been found on rather steep and narrow continental margins characterized by reduced or absent shelves (as those typical of insular, volcanic or tectonically-controlled coasts), in high-energy, wave-dominated environments. They have very similar morphologic and stratigraphic features, even if they are found in very different lithologic-physiographic contexts and tectonic settings.
As the SDT have limited extension (order of 102-103 m) and are often difficult to characterize, the comparative analysis among several case histories allowed a better comprehension of the processes causing the formation and preservation of such bodies, that are, in most cases, referable to sea-level stillstands significantly lower than at present. Moreover, this scientific topic has got potential applied aspects, such as the study of environmental changes in the recent geologic past and the use of SDT in the same way as the emerged coastal terraces are used, to underline recent crustal movements affecting a great part of the Italian coasts.
CARBONATE SEDIMENTS AND CORAL REEFS
OF AUSTRALIA’S WESTERN MARGIN
Lindsay B. Collins
Department of Applied Geology, Curtin University of Technology, Perth, WA
Australia’s western margin is narrow and wave-dominated in the south, and a wide ramp influenced by tides and cyclonic storms in the north. Coral reefs are present from latitudes 12 to 30∞S. A biotic transition zone, between the Northern Australian Tropical and Southern Australian Temperate zones, occurs at latitudes 26 to 30∞S.
The passive continental margin of southwest Australia, from Perth in the north to Cape Leeuwin in the south, has a narrow, cool-water carbonate shelf which is wave-dominated and predominantly open. The southwestern continental margin (19∞S -22∞S) is transitional between cool- and warm-water carbonate realms. It comprises the incipiently rimmed, flat topped, steep-fronted Rottnest Shelf in the south, the uniform subtropical starved Carnarvon Ramp off Shark Bay, and the Ningaloo fringing reef in the north. The margin is strongly influenced by the poleward-flowing, warm nutrient-poor Leeuwin Current, which promotes overall downwelling and strong summer equatorward-blowing winds, which generate local seasonal upwelling.
The structurally quiescent Rottnest Shelf is characterized by luxuriant stands of seagrass and macrophytes growing on coralline-encrusted hardgrounds and rooted in sediments rich in coralline algae and larger, symbiont-bearing foraminifers together with abundant cool-water elements such as bryozoans, molluscs, and small foraminifers. The incipient rim is a morphologically complex linear ridge system whose northern part is capped by the Houtman Abrolhos reefs (Collins et al 1997). Subphotic sediments on the deep, outer shelf and upper slope, affected by seasonal upwelling, are bryozoan-dominated deposits rich in small foraminifers and sponge spicules.
The inner part of the more structurally active Carnarvon Ramp (James et al, 1999) ranges from steep eolianite cliffs to hypersaline environments of Shark Bay to the Ningaloo fringing reef (Collins et al, 2002). Mid-ramp sediment, off Shark Bay, is relict or stranded and foraminifer-dominated sand with abundant Mg-calcite-cemented intraclasts. These sediments, accumulating on a relatively barren seafloor, represent attenuated carbonate production brought about by downwelling and episodic incursions of saline, Shark Bay-derived waters onto the ramp. The outer ramp is either planktic foraminiferal sand, sorted by strong bottom currents, or spiculitic mud.
The Northwest Shelf, a large carbonate ramp, has little coral growth except for isolated distal-ramp reefs, such as Scott Reef and Rowley Shoals (Collins et al, 2002). Cyclonic storms, long period swells and large internal tides result in mostly coarse-grained sediments. Circulation is dominated by the Leeuwin Current, upwelling associated with the Indian Ocean gyre, seaward-flowing saline bottom waters generated by seasonal evaporation, and flashy fluvial discharge. Sediments are palimpsest, a variable mixture of relict, stranded and Holocene grains (James et al, in press). Relict intraclasts are localised to the middle ramp, while the most conspicuous stranded particles are ooids and peloids which 14C dating shows formed 15.4-12.7 ka, during initial stages of the post-LGM sea level rise. Initiation of Leeuwin Current flow and accompanying less saline waters arrested ooid formation such that subsequent benthic Holocene sediment is skeletal and focused on the inner ramp. Here sediments reflect an oligotrophic shallow water environment (coral reefs and large benthic forams) perturbed by influx of land-derived sediments and nutrients, resulting in mesotrophic periods (macroalgae and bryozoans). Holocene middle ramp sediment is sparse, and outer ramp sediment is mainly pelagic. Phosphatic accumulations at 200 mwd indicate upwelling. Surface sediments, with large relict and stranded elements, are out of equilibrium with the present environment and are atypical for a ramp, probably due to failure of the carbonate factory to keep pace with rapid transgression.
Collins, L.B., France, R. E., Zhu, Z. R. , and Wyrwoll, K-H , 1997, Warm-water platform and cool-water shelf carbonates of the Abrolhos Shelf, southwest Australia, in N. James and J. Clarke, eds, Cool Water Carbonates, SEPM Special Publication 56,p.23-36. SEPM (Society for Sedimentary Geology).
Collins, L.B., Tertiary Foundations and Quaternary Evolution of Coral Reef Systems of Australia’s North West Shelf. In: Keep, M & Moss, S.J., (Eds) 2002. The Sedimentary Basis of Western Australia 3: Proceedings of the Petroleum Exploration Society of Australia Symposium, Perth, WA, 2002.
James, N.P., Collins, L.B., Bone, Y., and Hallock, P, 1999, Subtropical carbonates in a temperate realm: modern sediments on the southwest Australian shelf. Journal of Sedimentary Research, 69(9):1297-1321.
SEA LEVEL AND ENVIRONMENTAL
CHANGES SINCE THE LGM IN THE DE LA PLATA RIVER (ARGENTINA)
José Luis Cavallotto
Division of Marine Geology and Geophysics, Argentine Navy Hydrographic Office,
Avda. Montes de Oca 2124. C1270AVB, Buenos Aires, Argentina
The de la Plata river constitutes a fluvial-estuarine system where fluvial and tidal dynamic activelly interact. The river and adjacent coastal region constitute one of the principal areas of the entire Argentine coastal areas where most significative geomorphological changes occurred since the LGM due to interaction among sea-level changes, fluvial activity, estuarine dynamic, coastal processes, high sedimentation rates, migration of a muddy depocenter and the geometry of the pre-Holocene surface. Geometry and sea level fluctuations conditioned the distribution, extension and development of the sedimentary deposits, whereas hydrometeorological conditions determined the rate of sediment supply and transport. The most important feature of the pre-Holocene surface geometry was the ancient fluvial valley of the de la Plata river.
The evolution is summarized in three stages: estuarine, coastal plain and fluvial-estuarine deltaic, that respectively represent the processes that filled up the ancient fluvial valley, the coastal progradation and the installation of a deltaic system with the consequent environmental change from estuarine to fluvial conditions.
The processes occurred as a result of these events conduced to deposition in 5th order sequences which have been interpreted as systems tracks whose study reveals the occurrence of distinctive stages of sea-level fall and rise.
VOLCANIC ACTIVITY AND GEODYNAMIC SETTING FROM THE WESTERN PONTINE ISLANDS
Conte A.M.*, Dolfi D.**
* Istituto di Geoscienze e Georisorse - C.N.R. – Sezione di Roma c/o Dipartimento di Scienze della Terra Università “La Sapienza” – P.le A. Moro, 5 Roma
** Università di Roma 3, Largo S. Leonardo Murialdo 1 , Roma
Five major islands plus some islets and ledges are grouped in the Pontine Archipelago, facing the Gulf of Gaeta (Southern Latium). The five islands can be grouped in two clusters, on the basis of their location and lithology. Ponza, Zannone and Palmarola, which define the NW group, are located on a structural high of the continental shelf, at the border of the continental slope. They mainly consist of volcanic products outpoured during two volcanic cycles occurred in Pliocene (4-3.7 Ma) and Pleistocene ages (1.7-0.99 Ma) (Savelli, 1983, 1987; Cadoux et al. 2003).
Ventotene and S. Stefano, the SE-Pontine group, represent the upper portion of a large strato-volcano founded at some 700 m below the sea level. The age of the outcropping volcanites spans from 0.92 to 0.33 Ma (Metrich et al. 1988; Bellucci et al. 1999).
During the first volcanic cycle, submarine domes, rhyolitic in composition, were outpoured in the Ponza-Zannone area; their distribution, however, seem to be significantly wider and probably involving the whole area around the islands (including the SW sector of Palmarola), as testified by the several samples with homogeneous chemistry collected on the seafloor. Chemical characters of the emplaced rocks, strongly contrast with the basaltic composition of the almost coeval Vavilov magma (4.1-3.6 My; Sartori, 1990), and evidence a strong crustal interference either in the Sr and Nd isotopic ratios as well as in the trace elements distribution. They show chemical characters which fit both with a crustal anatectic origin and with an assimilation–fractional crystallization process from a subduction related basaltic parental. The first hypothesis seems to be strengthened by the high 87Sr/86Sr isotopic ratios.
The Pleistocene volcanic cycle started in the NW islands leading to the emplacement of rhyolitic domes in Palmarola and to subaerial trachytic volcanites in the southern part of Ponza. Rhyolites related to the new cycle show an alkaline chemical affinity, evidencing a lower temperature and a less deep origin than the previous. Major, trace elements and isotopic ratios suggest an origin by partial melting of the consolidated Pliocene magmatic intrusives. The sodic character of such magmas could be connected with the coeval Na-alkalic volcanism in Ponza (a comendite dike and Na-trachitic juvenile boulders carried in the subsequent pyroclastic flow) which marked the beginning of the subaerial activity giving rise to the potassic lava dome of Mt. Guardia. Trachytes at Mt.Guardia are the first evidence of the shoshonitic magmatism which prosecuted in the SE islands up to the most recent volcanites of Procida and Ischia, where outcropping basalts and their differentiated clearly attest the involvement of a subduction modified mantle material.
Timing and space evolution of the Pontine volcanism, combined with the chemistry of the extruded rocks suggest a location at the hinge of the northern and southern Tyrrhenian sea domains, mainly characterized by a different lithospheric thickness. The NW Pontine have been affected by a minor extension and their rocks show chemical characters akin to the ones in the N-Tyrrhenian domain, where magmatic rocks never evidence a clear involvement of mantle magma but only an enhanced heat flow and/or a probable magma underplating. The greater Tyrrhenian extension southward only slightly affected the NW archipelago, causing a light remelting of the Pliocene magmatites and a strong interference between mantle magma and confining rocks in the Southern Ponza. Such extension became evident through the rise and emission of mantle magma in Ventotene and Santo Stefano; the outpoured basalts having the same chemical affinity of the ones drilled in the Marsili basin.
Bellucci F., Lirer L., Munno R. (1999) : Geology of Ponza, Ventotene and S. Stefano Islands (with a 1:15000 scale geological map). Acta Vulcanol. 11, 197-222.
Cadoux A., Aznar C., Pinti D.L., Chiesa S., Lefevre J.C. and Gillot P.Y. (2003) : Time and geochemical distribuition of Central Italy magmatism: paleosubduction processes or crustal stretching? Geophys. Res. Abstracs, 5, 005686.
Metrich N., Santacroce R., Savelli C. (1988) : Ventotene, a potassic Quaternary volcano in Central Tyrrhenian Sea. Rend. SIMP 43, 1195-1213.
Sartori R. (1990) : The main results of ODP leg107 in the frame of Neogene to Recent geology of perityrrhenian areas. P107, 715-730
Savelli C. (1983) : Età K/Ar delle principali manifestazioni riolitiche dell’Isola di Ponza. Rend. Soc. Geol. It. 6, 39-42.
Savelli C. (1987) : K/Ar ages and chemical data of volcanism in the Western Pontine Islands (Tyrrhenian Sea). Boll. Soc. Geol. It. 106, 537-546.
THE ROLE OF THE MEANDERING
OF BRAZIL CURRENT IN THE SEDIMENTATION OF THE OUTER SHELF-UPPER SLOPE
OFF SOUTHEASTERN BRAZIL UNDER DIFFERENT CLIMATIC CONDITIONS: SEDIMENTOLOGICAL
DATA AND A NUMERICAL MODELLING APPROACH.
Michel Michaelovitch de Mahiques, Leandro Calado, Ilson Carlos Almeida da Silveira, Andréa França Lima
Institute of Oceanography, University of São Paulo, 05508-900 Praça do Oceanográfico, 191, São Paulo SP BRAZIL , E-mail: firstname.lastname@example.org
In this work we used information on magnetic susceptibility, calcium carbonate and grain size parameters in box-cores and piston-cores in order to investigate variations in the sedimentary column that can be associated to the oscilations in the intensity of the action of Brazil Current . Also, a simple numerical modelling approach was used assuming a coastline located 150 meters below the present sea-level during the Last Glacial Maximum.
It has been already verified in previous works that the meandering of the Brazil Current presents a “floor-polisher effect” over the bottom of the outer shelf and upper slope of Southeastern Brazil. As a rule the present surface is covered by a very thin (few centimeters to decimeters) bed of Holocene sandy sediments. In some areas the sandy sedimentation gives place to the establishment of a carbonatic bottom.
In order to verify the sedimentary trends associated to different climatic conditions, we used detailed data of short piston cores. In both cases the Last Glacial Maximum sediments are composed by finer sediments with a higher terrigenous contribution. It seems that during Isotope Stage 3, which position in the Southeastern Brazilian shelf is still controversial, the hydrodynamic conditions were more energetic than those of the Last Glacial Maximum but less than those of the Holocene.
Two numerical experiments using a regional implementation of the Princeton Ocean Model are conducted to evaluate the Brazil Current activity in the vicinities of the shelf break and upper slope. The first experiment aims to reproduce present sea-level conditions and, indeed, intense meandering occur near Capes São Tomé (22oS) and Frio (23oS).
These meanders occasionaly grow and clockwise rotating eddies are pinched off from the current axis. The second experiment simply considered a sea level located 150 m below the present level. The velocity structure shows that the Brazil Current core is displaced offshore and is shallower than in the previous experiment. The Brazil Current meanders as vigorously as in the first experiment. However, these preliminary results indicate that the meandering around Cape Frio is not as recurrent, and meander growth occurs not only near Cape São Tomé but also further south near Cape Santa Marta Grande (28oS).
As Cape Frio meandering weakens in the second experiment, the associated current activity south of 23oS does also. Therefore, under the conditions of lowered sea level, we might speculate that the sediment transport remobilization is attenuated as consequence, agreeing well with the sedimentological data.
Financial support by Fundação de Amparo à Pesquisa do Estado de São Paulo (Processes 01/13490-9 and 98/0572-2)
PEARL RIVER ESTUARY RELATED SEDIMENTS
AS RESPONSE TO HOLOCENG CLIMATE CHANGE AND ANTHROPOGENIC IMPACT ––
South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China
Baltic Sea Research Institute, Warnemünde, Germany
The Pearl River drainage basin, its mouth and the corresponding shelf of the South China Sea altogether compose an area characterized by large and stable sediment supply, frequent sea level and coastal line changes and related development of complicated multiphase under-water delta systems, long history and extensive records of human activities, and dramatic economic boom and associated environmental problems in recent decades. The area may serve as a global key area to study the land sea interaction including coastal processes mirroring natural and man made driving forces.
The Baltic Sea Research Institute in Warnemünde, Germany and the South China Sea Institute of Oceanology in Guangzhou, China aim to join their forces in studying sedimentary systems in coastal areas influenced by natural and man made driving forces. The partners plan to reconstruct the change of climate (precipitation, temperature, storm frequencies etc.) since the sea level high stand 7 500 y BP and anthropogenic activities during the last centennial. Future scenarios of sediment distribution and coastal processes shall be derived based on the estimation of trends stored in sedimentary archives. Generalized project results shall help in decision making in the frame of coastal zone management.
The objectives of PECAI are threefold:
(1) The facies change within sediment cores taken by the SCSIO shall be correlated with seismic profiles. Geostatistical methods will be applied to develop a space model of the sedimentary sequence within the estuary and contiguous shelf areas. 14C-age models based on selected dated samples help to transform the space-models into space/time-time models. The sedimentary facies will be recorded by physical, granulometric, mineralogical and geochemical analysis of samples from cores from the estuary. The variation of facies within dated sedimentary records will be interpreted as a result of the change of the depositional environment. Special attention will be paid anthropogenic influence due to human activities (agricultural and industrial development) within the coastal zone and the Pearl River’s drainage basin.
(2) The uppermost sediment cover within the estuary and contiguous shelf areas will be studied in detail aiming to record the facies change along transects from the river’s outlets to the shelf laterally and vertically. The analysis shall reveal the environmental change during the last century. For this reason joint expeditions are planned in order to run high resolution seismoacoustic profiles and to sample the uppermost sediment layers (50 cm) by Rumohr corers. The dating shall be based on 210Pb-age models. Sediments will be analysed by methods of MSCL core logging, organic (anthropogenic PCB, HCB, HCH, DDT, DDE, PAH and biomarker) and inorganic geochemistry.
(3) Having analyzed the long and short termed environmental change in the coastal areas of the Pearl River mouth, it is planned to derive scenarios of future coastal development based on prediction of sea level rise due to anthropogenic green house gas emissions. Applying a method developed for the Baltic Sea results from coupled atmospheric/oceanographic modeling of global warming based on IPCC scenarios of green house gas emissions the change of coast lines can be predicted including data on sea level rise and vertical crustal movement. Data on sediment accumulation received by the solution of tasks (1) and (2) shall be included.
EFFECT OF DIFFERENT DELTA TYPES
ON SHELF, CONTINENTAL SLOPE AND DEEP-SEA FAN SEDIMENTARY ARCHITECTURE GENESIS
IN A RELATIVE-SEA-LEVEL FALL/LOWSTAND CONTEXT: EXAMPLES FROM THE MANICOUGAN
DELTAIC PRISM, CANADA.
Mathieu J. Duchesne* and Bernard F. Long
INRS-ETE, Institut National de la Recherche Scientifique CP 7500 Sainte-Foy (Québec), Canada, G1V 4C7 email@example.com
The Manicouagan Peninsula corresponds to a lowstand deltaic plain lying in a pseudo-shelf-edge position along the Laurentian Channel in the St. Lawrence Estuary, Canada. The peninsula is surrounded by three main rivers which contributed to the deltaic prism construction during the last glacial retreat by supplying their own delta. This system represents a perfect analog for continental margin settings and therefore for the study of impacts of different delta types on the shelf, continental slope and deep-sea fan sedimentary architecture. Because this analogue is located in water depths averaging 350 m, the resolution of the study has been enhanced by one order of magnitude in comparison with similar systems located in deeper marine settings. Aerial photos and geophysical data show that each of the three delta displays a different construction style; i.e. wave-influenced, river-dominated and river-dominated/wave-influenced. These data also highlighted the influence of the relative-sea-level fall and the following lowstand context as well as the shelf width on the exportation nature of the deltas. The three river estuaries correspond to by-pass zones where sediments are exported on the shelf and than on the basin floor by mass wasting events or directly on the basin floor via channels which feed a submarine fan.
The results contributed 1) to document the evolution of a shelf-edge deltaic prism in a relative-sea-level fall/lowstand context, 2) to identify the different stages of construction and 3) to observe the influence of the different delta styles on channel types and submarine fans architecture. Based on comparisons on similar types and well-documented deltaic systems, like the Late Pleistocene Lagniappe Delta, the modern Nile Delta and the modern Po delta, the deltaic style does not seems to influence the genesis of the continental slope and basin floor sedimentary architecture. Moreover, sand distribution in three studied systems is driven by autocyclic processes like basin morphology, delta orientation on the shelf, distance of the delta from the shelf edge, hydrodynamic conditions of the basin and physiographic configuration of the shelf. Therefore, geometries and location of the sand bodies in the systems are controlled by autocyclic rather than allocyclic processes.
DISTRIBUTION OF RECENT FORAMINIFERAL
ASSEMBLAGES NEAR THE PONZA ISLAND (CENTRAL TYRRHENIAN SEA, LATIUM,
Frezza Virgilio, Carboni Maria Gabriella, Matteucci Ruggero
Dipartimento di Scienze della Terra, Università degli Studi di Roma “La Sapienza”
Ponza Island is located in the western sector of the Pontine volcanic Archipelago, on a structural high of the continental Tyrrhenian shelf. This preliminary study is comprised in a broad interdisciplinary project, aimed to know and describe the sea bottom of the Pontine Archipelago. On the whole, 22 grab samples, collected for micropaleontological analyses east to Ponza during the cruise of spring 2001, have been studied. Sampling stations range from 20 to 380 m water depth and are located on four transects, having the NW/SE direction. Among these, one transect comprises 12 stations, while the others are constituted by 2 to 4 stations. Samples were stored in ethanol-Rose Bengal solution to distinguish between living and dead foraminifera. The quantitative analysis was carried out on the total assemblage because the percentage of living foraminifera was very low. The total assemblage, which represents the mean environmental conditions over the year, according to Scott and Medioli (1980), was utilised for statistical data processing, while the living specimens were considered indicative of autochthonous species. All the samples were wet-sieved over 63 and 125 _m, but in this study, data from > 125 _m size fraction are used. A total of 198 species, belonging to 90 genera, have been recognized. The data set, containing relative abundance of 16 common taxa of benthic foraminifera, was used to perform the multivariate analysis (HCA and PCA). The Q-mode HCA groups samples that may be viewed as foraminiferal biofacies (Scott et al., 2001). The output of Q-mode HCA singles out three main clusters, corresponding to three distinct foraminiferal assemblages: 1) Rosalina bradyi and Asterigerinata mamilla assemblage (depth: 20-87 m), with Lobatula lobatula, Spirillina vivipara, Tretomphalus concinnus and miliolids; 2) Cassidulina carinata assemblage (depth: 79-202 m), with Bolivina difformis and Textularia bocki; 3) Uvigerina mediterranea assemblage (depth: 250-380 m), with Bulimina marginata and Cassidulina crassa. The three assemblages correspond to a bathymetric zonation: assemblage 1 corresponds to infralittoral environment and is located near Ponza, mainly in the sea grass bottom (Posidonia oceanica); assemblage 2 corresponds to circalittoral environment, while assemblage 3 corresponds to upper epibathyal environment.
Factor 1 of PCA, that explains the 30,8% of variability, shows a decreasing trend according to the increasing water-depth. It presents positive values in the infralittoral and circalittoral samples, negative values in the epibathyal ones. In addition, factor 1 shows a negative correlation with P/B ratio: negative values of factor 1 correspond with higher values of P/B ratio.
Scott D.B., Medioli F.S., (1980) Living vs. total foraminiferal populations: their relative usefulness in paleoecology, Journal of Paaleontology, 54: 814-831
Scott D.B., Medioli F.S., Schafer C.T., (2001) Monitoring of Coastal environments using Foraminifera and Thecamoebian indicators, Cambridge University Press, 176
CLIMATE OF THE LAST GLACIAL CYCLE
AND THE PEOPLING OF THE AMERICAS
Renée Hetherington1, Álvaro Montenegro Neto1, Andrew Weaver1, Michael Eby1, Ed Wiebe1
1University of Victoria, School of Earth and Ocean Sciences, Climate Modelling Group, Victoria, British Columbia, Canada
*contact author: Renée Hetherington: firstname.lastname@example.org; 250-472-4013
Archaeological theories explaining the diaspora of peoples into the Americas during the last glacial cycle (LGC) often cite climate change as a key determinant, proposing environmental conditions and resource limitation as an impetus and constraint to movement. However, supporting evidence is difficult to obtain: glaciers may have destroyed mainland archaeological sites; continental shelves are now submerged; shorelines have shifted significantly, particularly in the northern hemisphere where the effects of glacio-isostacy complicate the eustatic effects of sea-level change. Yet despite the rapid climate change experienced during the LGC and despite lacking modern economic and technological advancements, early peoples not only persisted, but migrated throughout the world.
Research is focused on the potential of a Pacific coastal migration route into the Americas subsequent to the last glacial maximum (LGM). Paleoenvironmental and paleocoastline reconstructions of the Late Quaternary Pacific margin of Canada assist in determining the feasibility of a coastal migration route into the Americas. A coastal migration route implies that early people used watercraft to successfully travel from Asia to the Americas. Using output from the UVic Earth System Climate Model and the ‘Estimating the Circulation and Climate of the Ocean’ (ECCO) project, the feasibility of both a coastal and alternative cross-oceanic routes are tested. By placing drifters along the coasts of North America, northeast Asia, and Australasia we determine if, when, and where they land. Two scenarios are examined: the first using present ocean current and wind conditions, the second using LGM conditions. Our results provide insights into the circumstances under which drifters successfully reach land, and the probability of occurrence.
CONTINENTAL SHELF EVOLUTION DURING
THE LAST GLACIAL CYCLE – INFLUENCE OF HUMAN CULTURE
University of Victoria, School of Earth and Ocean Sciences, Climate Modelling Group, Victoria, British Columbia, Canada
*contact author: Renée Hetherington: email@example.com; 250-472-4013
The fourth IGCP 464 working group “Influence on Human Culture” acknowledges that not only do humans influence continental shelf evolution – as in Hong Kong harbour (Chan & Yim 2001; Yim 2001, 2003) - but that continental shelf evolution has influenced human culture, behaviour, and migrations over the last glacial cycle (LGC). Shelf areas underwent significant changes during the LGC. Flat, lowstand coastal plains emerged that were suitable for human settlements. Rapid sea-level rise resulted in coastal retreat of more than 100 m per year, and the damming of the incised valleys by transgressive littoral barriers caused rivers to flood and coastal marshes and swamps to form.
Changes in the paleoenvironment and paleogeography of the shelf has led IGCP 464 researchers from Australia (Garcia et al. 2001, 2002, 2003; Holt et al. 2003; Reeves et al. 2003; Van Der Kaars et al. 2003), Denmark (Jensen et al. 2003), Germany (Harff et al. 2003; Lemke et al. 2003), Portugal (Dias et al. 2003), Italy (Enzo et al. 2001), Korea (Park & Kim 2003), Lithuania (Bitinas 2003; Kabailiene 2003; Mork_nait_ and Janukonis 2003), Poland (Kramarska et al. 2002, 2003; Pomian 2003; Uscinowicz and Miotk-Szpiganowicz 2001; Uscinowicz et al. 2002, 2003; Zachowicz 2001, Zachowicz et al. 2003), Russia (Spiridonov and Zhamoida 2003), South Africa (Franceschini and Compton 2001), and France, the United States, and Canada (Faure et al. 2002) and to suggest links and influences between LGC induced changes and human occupation, expansion, and regional economic and cultural development.
Researchers from Argentina (Cavallotto et al. 2002, 2004; Nami 2001; Torra 2001; Violante 2001, 2002; Aguirre & Violante 2002; Violante & Parker 2004), Brazil (Lima et al. 2002, de Mahiques et al. 2003), Canada (Hetherington et al. 2001, 2002, 2003, 2004; Josenhans 2001; Fedje 2003; Hetherington and Weaver 2003; Al-Suwaidi et al. 2003; Fladmark 2003; Jackson 2003; Ward et al. 2003; Wilson et al. 2003), and Russia (Patyk-Kara 2003), are comparing their findings in an effort to provide insights into early human habitation and peopling of the Americas.
IGCP 464 researchers from Belgium, France, Romania, and the United States are investigating how catastrophic flooding of the Black Sea 7,500 years ago may have played a role in the spread of early farming into Europe and much of Asia and influenced the deluge account in the Babylonian epic of Gilgamesh and, in turn, the story of Noah in the Book of Genesis (Lericolais et al. 2001; 2003; Ryan et al. 2003).
This presentation will briefly highlight a few IGCP464 research initiatives before providing a case study of the Late Quaternary Pacific Margin of Canada and the peopling of the Americas.
Aguirre, M. and Violante, R.A. 2002. Molluscan assemblages from the Bonaerensian nearshore and inner continental shelf (Argentina) since the late Pleistocene: palaeoenvironmental interpretation. IGCP #464 Continental Shelves During the Last Glacial Cycle, 2nd Annual Conference São Paulo, August 30 – September 3, 2002, Abstracts volume.
Al-Suwaidi, M.H., Ward, B.C., Wilson, M.C., Enkin, R.J., Nagorsen, D.W. and Wigen, R.J. 2003. Port Eliza Cave: The sedimentology, stratigraphy and palaeontology of cave deposits and their implications for a human coastal migration route. Geological Association of Canada-Mineralogical Association of Canada-Society of Economic Geologists Joint Annual Meeting, IGCP #464 Regional Conference Special Session 1: Early humans and the evolving northeastern Pacific margin, Vancouver May 25-28, 2003, Abstracts volume.
Bitinas, A. The Lithuanian coast of the Baltic Sea: natural processes and human influence. Rapid Transgressions into semi-enclosed basins, IGCP #464 Regional Conference, Gda_sk-Jastarnia, 8-10 May, 2003, Abstracts volume.
Cavallotto, J.L., Violante, R.A. and Nami, H.G. 2002. Late-Pleistocene/Holocene Paleogeography and Coastal evolution at the mouth of the Río de la Plata: implications for dispersal of Paleoindian people in South America. Current Research in the Pleistocene 19: 13-16.
Cavallotto, J.L., Violante, R.A. and Parker, G. 2004. Sea-level fluctuations during the last 8600 years in the de la Plata River (Argentina). Quaternary International 114: 155-165.
Chan, L.S. and Yim, W.W.-S. 2001. Application of magnetic properties for studying modern seabed sediments contaminated by shipping activity in Hong Kong Harbour. IGCP #464 Continental Shelves During the Last Glacial Cycle, 1st Annual Conference Hong Kong, October 25-28, 2001, Abstracts volume.
Dias, J.M.A., Gonzalez, R., Ferreira, Ò. and Boski, T. 2003. Natural versus anthropic causes in variations of sand export from river basins: an example from the Guadiana River mouth (southwestern Iberia). Rapid Transgressions into semi-enclosed basins, IGCP #464 Regional Conference, Gda_sk-Jastarnia, 8-10 May, 2003, Abstracts volume.
Enzo, F., Guiseppe, O. and Camilla, B. 2001. The influence of palaeogeography on human development in the southern Po Plain during the last 1 Ma. IGCP #464 Continental Shelves During the Last Glacial Cycle, 1st Annual Conference Hong Kong, October 25-28, 2001, Abstracts volume.
Faure, H., Walter, R.C., and Grant, D.R. 2002. The coastal oasis: ice age springs on emerged continental shelves. Global and Planetary Change 33: 47-56.
Fedje, D. 2003. Early landscapes and archaeology in Haida Gwaii on the west coast of Canada. IGCP #464 Continental Shelves During the Last Glacial Cycle, 3rd Annual Conference University of Wollongong, Australia, December 14-19, 2003, Abstracts volume.
Fladmark, K.R. 2003. None if by Land, Two if by Sea: assessing the relative feasibility of Late Pleistocene coastal vs. interior migration routes for early native Americans moving south of Beringia. Geological Association of Canada-Mineralogical Association of Canada-Society of Economic Geologists Joint Annual Meeting, IGCP #464 Regional Conference Special Session 1: Early humans and the evolving northeastern Pacific margin, Vancouver May 25-28, 2003, Abstracts volume.
Franceschini, G. and Compton, J.S. 2001. Holocene evolution of the Sixteen Mile Beach complex West Coast National Park, South Africa. IGCP #464 Continental Shelves During the Last Glacial Cycle, 1st Annual Conference Hong Kong, October 25-28, 2001, Abstracts volume.
García, A., Chivas, A.R., Reeves, J.M., Couapel, M.J.J., Van Der Kaars, S., Holt, S. and De Deckker, P. 2001. IGCP #464 Continental Shelves During the Last Glacial Cycle, 1st Annual Conference Hong Kong, October 25-28, 2001, Abstracts volume.
García, A., Chivas, A.R., Holt, S. and Reeves, J. 2002. Late Pleistocene palaeo-environmental history from the Gulf of Carpentaria, Australia: interpretation based on foraminifera, ostracoda and charales. IGCP #464 Continental Shelves During the Last Glacial Cycle, 2nd Annual Conference São Paulo, August 30 – September 3, 2002, Abstracts volume.
García, A., Chivas, A.R., Reeves, J.M., and Holt, S. 2003. Late Pleistocene palaeo-salinity history from the Gulf of Carpentaria, Australia: charophytes (Charales, algae) and other organisms. IGCP #464 Continental Shelves During the Last Glacial Cycle, 3rd Annual Conference University of Wollongong, Australia, December 14-19, 2003, Abstracts volume.
Harff, J., Lemke, W., Lampe, R., L_th, F., L_bke, H., Meyer, M. and Tauber, F. 2003. Sinking coasts: geosphere, ecosphere and anthroposphere of the Holocene southern Baltic Sea. Rapid Transgressions into semi-enclosed basins, IGCP #464 Regional Conference, Gda_sk-Jastarnia, 8-10 May, 2003, Abstracts volume.
Hetherington, R. and Weaver, A.J. 2003. Climate and human adaptation over the last glacial cycle. IGCP #464 Continental Shelves During the Last Glacial Cycle, 3rd Annual Conference University of Wollongong, Australia, December 14-19, 2003, Abstracts volume.
Hetherington, R., Barrie, J.V., Reid, R.G.B., MacLeod, R. and Kung, R. 2001. Palaeogeography and early human adaptation of the Queen Charlotte Islands, Canada: drowned landscapes, paleo-coastlines, and paleo-marine habitats. IGCP #464 Continental Shelves During the Last Glacial Cycle, 1st Annual Conference Hong Kong, October 25-28, 2001, Abstracts volume.
Hetherington, R., Barrie, J.V., Reid, R.G..B. and MacLeod, R. 2002. Paleoenvironment of the Late Quaternary Pacific margin of Canada: influence on Americas’ first humans. IGCP #464 Continental Shelves During the Last Glacial Cycle, 2nd Annual Conference São Paulo, August 30 – September 3, 2002, Abstracts volume.
Hetherington, R., Barrie, J.V., Reid, R.G.B. and MacLeod, R. 2003. The environment of late Pleistocene – early Holocene Queen Charlotte Islands archipelago, Western Canada and implications for early humans. Geological Association of Canada-Mineralogical Association of Canada-Society of Economic Geologists Joint Annual Meeting, IGCP #464 Regional Conference Special Session 1: Early humans and the evolving northeastern Pacific margin, Vancouver May 25-28, 2003, Abstracts volume.
Hetherington, Barrie, J.V., Reid, R.G.B., MacLeod, R. and Smith, D.J. 2004. Paleogeography, glacially induced crustal displacement, and Late Quaternary coastlines on the continental shelf of British Columbia, Canada. Quaternary Science Reviews 23: 295-318.
Holt, S., Chivas, A.R., and García, A. 2003. Late Quaternary foraminifers, palaeoenviroments and sea-level change in the Gulf of Carpentaria, Australia. IGCP #464 Continental Shelves During the Last Glacial Cycle, 3rd Annual Conference University of Wollongong, Australia, December 14-19, 2003, Abstracts volume.
Jackson, L.E. 2003. The timing of ice-free corridors through the Cordillera and adjacent interior plains-open and shut cases. Geological Association of Canada-Mineralogical Association of Canada-Society of Economic Geologists Joint Annual Meeting, IGCP #464 Regional Conference Special Session 1: Early humans and the evolving northeastern Pacific margin, Vancouver May 25-28, 2003, Abstracts volume.
Jensen, J.B., Lemke, W., Bennike, O., Witkowski, A. and Kuijpers, A. 2003. The late glacial and Holocene pathway to the Baltic: a sequence-stratigraphical approach. Rapid Transgressions into semi-enclosed basins, IGCP #464 Regional Conference, Gda_sk-Jastarnia, 8-10 May, 2003, Abstracts volume.
Josenhans, H. 2001. Glaciers, lowered sea levels and early humans on Canada’s continental shelves. IGCP #464 Continental Shelves During the Last Glacial Cycle, 1st Annual Conference Hong Kong, October 25-28, 2001, Abstracts volume.
Kabailiene, M. 2003. Sea level changes and history of human activity along the southeastern Baltic sea coast according to palaeoecological and geological data. Rapid Transgressions into semi-enclosed basins, IGCP #464 Regional Conference, Gda_sk-Jastarnia, 8-10 May, 2003, Abstracts volume.
Kramarska, R. 2003. Origin of sub-Quaternary relief in the Southern Baltic area. IGCP #464 Continental Shelves During the Last Glacial Cycle, 3rd Annual Conference University of Wollongong, Australia, December 14-19, 2003, Abstracts volume.
Kramarska, R., Uscinowicz, S. and Zachowicz, J. 2002. Main Stages of the Southern Baltic development. IGCP #464 Continental Shelves During the Last Glacial Cycle, 2nd Annual Conference São Paulo, August 30 – September 3, 2002, Abstracts volume.
Lemke, W., Jensen, J.B., Bennike, O., Witkowski, A., Harff, J., Endler, R., Kuijpers, A. and L_bke, H. 2003. Towards the reconstruction of the littorina transgression within the southwestern Baltic Sea. Rapid Transgressions into semi-enclosed basins, IGCP #464 Regional Conference, Gda_sk-Jastarnia, 8-10 May, 2003, Abstracts volume.
Lericolais, G., Panin, N., Guichard, F. and Major, C. 2001. A high-resolution record of the late glacial maximum event in the western Black Sea. IGCP #464 Continental Shelves During the Last Glacial Cycle, 1st Annual Conference Hong Kong, October 25-28, 2001, Abstracts volume.
Lericolais, G., Panin, N., Guichard, F., Popescu, I. and the BLASON Scientific Crew 2003. The Black Sea as a record of the Younger Dryas climate change. IGCP #464 Continental Shelves During the Last Glacial Cycle, 3rd Annual Conference University of Wollongong, Australia, December 14-19, 2003, Abstracts volume.
Lima, A.F., de Souza, L.A.P. and de Mahiques, M.M. 2002. Shallow seismic reflectors and upper Quaternary sea level changes in the northern inner shelf of the state of São Paulo, southeastern Brazil. IGCP #464 Continental Shelves During the Last Glacial Cycle, 2nd Annual Conference São Paulo, August 30 – September 3, 2002, Abstracts volume.
de Mahiques, M.M., Tessler, M.G., da Silveira, I.C.A., de Mello e Sousa, S.H., Figueira, R.L., Tassinari, C.C.G., Ciotti, A.M., Furtado, V.V. and Passos, R.F. 2003. Hydrodynamically-driven patterns of the post-LGM sedimentation in the shelf and upper slope off southeast Brazil. IGCP #464 Continental Shelves During the Last Glacial Cycle, 3rd Annual Conference University of Wollongong, Australia, December 14-19, 2003, Abstracts volume.
Mork_nait_, R. and Janukonis, Z. 2003. The impact of nature and anthrophogenic action to the coast structure and dunes in Curonian spit (Lithuania). Rapid Transgressions into semi-enclosed basins, IGCP #464 Regional Conference, Gda_sk-Jastarnia, 8-10 May, 2003, Abstracts volume.
Nami, H.G. 2001. Palaeo-Indian archaeological evidence and two cases of land bridges in southern South America. IGCP #464 Continental Shelves During the Last Glacial Cycle, 1st Annual Conference Hong Kong, October 25-28, 2001, Abstracts volume.
Park, Y.A. and Kim, S.J. 2003. Coastal Neolithic cultural site and the relative stand of middle Holocene sea level along eastern coast of Korea. IGCP #464 Continental Shelves During the Last Glacial Cycle, 3rd Annual Conference University of Wollongong, Australia, December 14-19, 2003, Abstracts volume.
Patyk-Kara, N.G. 2003. Sea/land interaction and shoreline evolution during the last glacial cycle in the Laptev and east-Siberian seas. IGCP #464 Continental Shelves During the Last Glacial Cycle, 3rd Annual Conference University of Wollongong, Australia, December 14-19, 2003, Abstracts volume.
Pomian, I. 2003. Remains of medieval harbour in Puck. Rapid Transgressions into semi-enclosed basins, IGCP #464 Regional Conference, Gda_sk-Jastarnia, 8-10 May, 2003, Abstracts volume.
Reeves, J.M., Chivas, A.R., García, A. and De Deckker, P. 2003. Palaeoenvironments of the Gulf of Carpentaria through the last glacial cycle: Ostracods and isotopes. IGCP #464 Continental Shelves During the Last Glacial Cycle, 3rd Annual Conference University of Wollongong, Australia, December 14-19, 2003, Abstracts volume.
Ryan, W.B.F., Major, C.O., Lericolais, G. and Goldstein, S.L. 2003. Catastrophic flooding of the Black Sea. Annual Reviews of Earth and Planetary Sciences 31: 525-554.
Spiridonov, M.A. and Zhamoida, V.A. 2003. The natural and anthropogenic features of the coastal zone of the eastern Gulf of Finland. Rapid Transgressions into semi-enclosed basins, IGCP #464 Regional Conference, Gda_sk-Jastarnia, 8-10 May, 2003, Abstracts volume.
Torra, R. 2001. Origin and evolution of the continental giant ‘Chacopampeno’ Shelf, Argentina: their evolution and morphology from the Miocene to the present day. IGCP #464 Continental Shelves During the Last Glacial Cycle, 1st Annual Conference Hong Kong, October 25-28, 2001, Abstracts volume.
Uscinowicz, S. and Miotk-Szpiganowicz, G. 2001. The final stage of the Holocene transgression in the Puck Lagoon area, southern Baltic Sea as observed from the Rzucewo Headland case study. IGCP #464 Continental Shelves During the Last Glacial Cycle, 1st Annual Conference Hong Kong, October 25-28, 2001, Abstracts volume.
Uscinowicz, S., Zachowicz, J. and Miotk-Szpiganowicz, G. 2002. Human activity in relation to late Holocene coastal changes of the Puck Lagoon. IGCP #464 Continental Shelves During the Last Glacial Cycle, 2nd Annual Conference São Paulo, August 30 – September 3, 2002, Abstracts volume.
Uscinowicz, S., Kramarska, R. and Zachowicz, J. 2003. The Baltic Sea floor morphology as a result of glacial erosion and marine processes. IGCP #464 Continental Shelves During the Last Glacial Cycle, 3rd Annual Conference University of Wollongong, Australia, December 14-19, 2003, Abstracts volume.
Van Der Kaars, S., Chivas, A.R. and García, A. 2003. Vegetation and landscape development in the Gulf of Carpentaria area during the last glacial cycle. IGCP #464 Continental Shelves During the Last Glacial Cycle, 3rd Annual Conference University of Wollongong, Australia, December 14-19, 2003, Abstracts volume.
Violante, R. A. 2001. Submerged features related to the LGM in the Argentine continental shelf: the present knowledge. IGCP #464 Continental Shelves During the Last Glacial Cycle, 1st Annual Conference Hong Kong, October 25-28, 2001, Abstracts volume.
Violante, R.A. 2002. The post-LGM transgressive surface in the northern region of the Argentina continental shelf. IGCP #464 Continental Shelves During the Last Glacial Cycle, 2nd Annual Conference São Paulo, August 30 – September 3, 2002, Abstracts volume.
Violante, R.A. and Parker, G. 2004. The post-last glacial maximum transgression in the de la Plata River and adjacent inner continental shelf, Argentina. Quaternary International 114: 167-181.
Ward, B., Wilson, M., Nagorsen,D., Wigen, B. and Al-Suwaidi, M. 2003. Port Eliza cave: North American west coast interstadial environment and implications for human migrations. Geological Association of Canada-Mineralogical Association of Canada-Society of Economic Geologists Joint Annual Meeting, IGCP #464 Regional Conference Special Session 1: Early humans and the evolving northeastern Pacific margin, Vancouver May 25-28, 2003, Abstracts volume.
Wilson, M.C., Hebda, R.J. and Keddie, G. 2003. Early postglacial fossil bison from Vancouver Island, British Columbia, and Orcas Island, Washington: morphology, taxonomy and paleoecological setting. Geological Association of Canada-Mineralogical Association of Canada-Society of Economic Geologists Joint Annual Meeting, IGCP #464 Regional Conference Special Session 1: Early humans and the evolving northeastern Pacific margin, Vancouver May 25-28, 2003, Abstracts volume.
Yim, W.W.-S. 2001. Recognition of postglacial and pre-postglacial sediments on continental shelves: lessons learnt from the Hong Kong SAR, China. IGCP #464 Continental Shelves During the Last Glacial Cycle, 1st Annual Conference Hong Kong, October 25-28, 2001, Abstracts volume.
Yim, W.W.-S. 2003. Anthropogenic impacts on the northern South China Sea continental shelf off Hong Kong. IGCP #464 Continental Shelves During the Last Glacial Cycle, 3rd Annual Conference University of Wollongong, Australia, December 14-19, 2003, Abstracts volume.
Zachowicz, J. 2001. Human activity of the Vistula delta plain and Vistula lagoon shoreline displacement during the Holocene. IGCP #464 Continental Shelves During the Last Glacial Cycle, 1st Annual Conference Hong Kong, October 25-28, 2001, Abstracts volume.
Zachowicz, J., Uscinowicz, S. and Miotk-Szpiganowicz, G. 2003. Geological, pollen and diatom indicators of the Holocene transgression in the southern Baltic lagoonal system. IGCP #464 Continental Shelves During the Last Glacial Cycle, 3rd Annual Conference University of Wollongong, Australia, December 14-19, 2003, Abstracts volume.
WAS THE LAST RAPID SEA CHANGE IN
THE BLACK SEA LINKED TO A CATASTROPHIC EVENT 7500 YEARS AGO ?
Gilles Lericolais1, Irina POPESCU2; Nicolae PANIN3, François Guichard4and Sperenta Popescu5
1- IFREMER, Centre de BREST, BP 70, F 29200 Plouzané cedex, FRANCE
2- RCMG - University of Ghent, Department of Geology and Soil Science - Krijgslaan 281 S8, B-9000 Gent, BELGIUM
3- GEOECOMAR, 23-25 Dimitrie Onciul Str , BP 34-51, Bucuresti, ROMANIA
4- LSCE, CNRS-CEA, Avenue de la Terrasse, BP 1, F 91198- Gif-sur-Yvette cedex, France
5-Université Claude Bernard Lyon1 - 43, bd du 11 Novembre 1918- F 69 622 Villeurbanne cedex
ID: 59648 Password: 230287
Two IFREMER oceanographic surveys carried out in the Black Sea in 1998 and 2002 in the frame of European projects complement previous seabed mapping and subsurface sampling studies realised in the Black Sea by various international expeditions. Until the Ryan and Pitman theory, it was admitted that the Black Sea was predominantly a freshwater lake interrupted by possible marine invasions coincident with high sea level during the Quaternary.
From recent surveys carried out on the north-western continental shelf of the Black Sea it comes that the Black Sea's lake level rose on the shelf to at least the isobath –40 to -30 m given by the landward limit of extend of the Dreissena layer characteristic of freshwater conditions. This rise in freshwater level could coincide with the answer of the Black Sea as an important catchment basin of the melt water drained from the melting of the ice cap ensuing the Melt Water Pulse 1A. It is possible that at that time the lake level filled by freshwater rose to the level of its outlet and spilled into the Mediterranean. However, in mid-Holocene at 7.5 ky BP the onset of salt water conditions are clearly evidenced in the Black Sea. From these observation Ryan et al. (1997) came to the conclusion that the Black Sea could have been filled by saltwater cascading from the Mediterranean. Even if this hypothesis has been discussed (Aksu et al., 1999, 2002), the recent discoveries of the excellent preservation of drowned beaches, sand dunes and soils during IFREMER surveys seem to bring arguments to the Ryan and Pitman assumption.
The multibeam echo-sounding and the seismic reflection profiles acquired during these surveys revealed wave-cut terraces at an average water depth of –100 m. More, evidence of sea water penetration is marked at the Bosphorus outlet as the recent canyon heads mapped during the last cruise in 2002 seemed to reveal. The cores recovered on the Romanian continental shelf present an erosion surface evidencing subaerial exposure well below the level of the modern Bosphorus outlet. The 14C ages documented a simultaneous colonisation of the terrestrial surface by marine molluscs at 7.1 ky BP. Last palynology analysis and studies of the dynokysts population, precise a real onset of freshwater arrival during the Younger Dryas and abrupt replacement of Black Sea dynokyst by Mediterranean population. Some preliminary results of a Marion Dufresne Campaign programmed in May 2004 will be presented.
THE HOLOCENE HIGHSTAND SYSTEMS
TRACT IN THE GULF OF CADIZ SHELF, NE ATLANTIC OCEAN: A RECORD OF OCEANOGRAPHIC
FORCING AND RECENT ENVIRONMENTAL CHANGES
F.J. Lobo(1), L.M. Fernández-Salas(2), F.J. Hernández-Molina(3), R. González(4), J.M.A. Dias(4), V. Díaz del Río(2)
(1) Instituto Andaluz de Ciencias de la Tierra, C.S.I.C.-Univ. Granada, Campus de Fuentenueva s/n, 18002 Granada, Spain
(2) Instituto Español de Oceanografía, Centro Oceanográfico de Málaga, Puerto Pesquero s/n, 29640 Fuengirola, Spain
(3) Facultad de Ciencias, Univ. Vigo, 36200 Vigo, Spain
(4) Faculdade de Ciencias Marinhas e Ambientais/CIMA, Univ. Algarve, Campus de Gambelas, 8000 Faro, Portugal
High-resolution seismic studies conducted in the Gulf of Cadiz margin were used as the basis for recognising the influence of oceanographic agents on recent sedimentation patterns (Lobo et al., 2004) and for understanding the complex internal architecture of Holocene highstand deposits and the possible influence of recent environmental cyclicities (Lobo et al., under review).
Several morpho-sedimentary units compose the Holocene highstand systems tract in the Gulf of Cadiz shelf, including infralittoral prograding wedges, poorly developed prodeltas evolving seaward to muddy belts and significant prodeltaic features linked to the main fluvial sources. A lateral transition of depositional styles results from different fluvial supplies, hydrodynamic conditions and physiographic constraints. The comparison of the stratigraphic architecture between shallow-marine deposits of the Gulf of Cadiz margin and emerged spit bars allowed defining a hierarchical pattern of high-frequency depositional sequences. Three scales of depositional sequences were related with high-frequency environmental fluctuations:
1) Major cycles: two major-scale depositional sequences are recognised in shallow-marine deposits of the Gulf of Cadiz margin and around the Iberian Peninsula.
2) Intermediate cycles: each major depositional sequence is composed by two intermediate-scale depositional sequences related with postglacial climatic shifts of ~1.500 years.
3) Minor cycles: climate variability of sub-millenial scale seems to have operated continuously during the recent Holocene highstand period.
Lobo, F.J., Sánchez, R., González, R., Dias, J.M.A., Hernández-Molina, F.J., Fernández-Salas, L.M., Díaz del Río, V., Mendes, I. (2004) Contrasting styles of the Holocene highstand sedimentation and sediment dispersal systems in the nothern shelf of the Gulf of Cadiz. Cont. Shelf Res. 24, 461-482.
Lobo, F.J., Fernández-Salas, L.M., Hernández-Molina, F.J., González, R., Dias, J.M.A., Díaz del Río, V., Somoza, L. (under review): Holocene highstand deposits in the Gulf of Cadiz, SW Iberian Peninsula: a high-resolution record of hierarchical environmental changes. Mar. Geol.
MULTIPROXY EVIDENCE OF LATE GLACIAL TO HOLOCENE
AND OF SANGAMONIAN MILLENNIAL-TO SEASONNAL-SCALE CLIMATIC OSCILLATIONS
IN THE ST. LAWRENCE ESTUARY, EASTERN CANADA
Guillaume St-Onge1, Anne de Vernal2, Claude Hillaire-Marcel2, Bernard Long1,2,*, Mathieu Duchesne1
1Institut national de la recherche scientifique - Eau, Terre et Environnement, P.O. Box 7500, Sainte-Foy, Québec, Canada, G1V 3C7
2GEOTOP-UQAM-McGill, P.O. Box 8888, Succ. Centre-Ville, Montréal, Québec, Canada, H3C 3P8
The IMAGES (International Marine Past Global Change Study) piston cores MD99-2220 (48°38.32’N/68°37.97’W, 320 m) and MD99-2221 (48o10.60’N/69o30.35’W, 212 m) raised from the Laurentian Channel in the lower estuary of the St. Lawrence provide a unique record for the reconstruction of large scale (sub-continental) hydrological changes and oceanographic variations because of its location, at the mouth of the St. Lawrence River watershed. An absolute calendar chronology spanning the last ~ 9400 years was established based on calibrated AMS-14C dates on mollusc shells and constraints from rock-magnetic and paleomagnetic secular variation data. By ~ 8.5 ka cal BP, a major change of the sedimentation rates was recorded, from > 33 m/ka to ~ 1.5 m/ka, along with a major change in the physical, sedimentological and magnetic properties of both cores, marking the drastic transition from glaciomarine to postglacial environments. Based on dinocyst transfer functions in core MD99-2220, the ~ 8.5 ka cal BP transition was followed by a drastic decrease of sea-ice cover, together with increased salinity and winter sea-surface temperatures. Millennial-scale cyclic variations of the sea-surface conditions are also highlighted.
Similarly, when the long-term influence of sediment compaction is removed from the signal, computerized axial tomography (CAT-scan) analysis of the two piston cores, with its 1 mm downcore resolution, not only reveals millennial-scale oscillations, but also higher frequency variations possibly annual to secular in origin. Furthermore, CAT-scan analysis of selected early Sangamonian (beginning of marine isotopic substage 5e, ~ 130 ka) sediments from a 150 m long core drilled on shore at Îles-aux-Coudres in the middle Estuary of the St. Lawrence likely allowed the identification of seasonal cycles, highlighting the usefulness of this method for rapid, non-destructive, ultrahigh-resolution analysis. Finally, the nature and origin of these millennial to seasonal oscillations will be discussed.
GEOLOGICAL CHARACTERS AND EVOLUTION
SINCE LGM OF WESTERN PONTINE CONTINENTAL SHELF (TYRRHENIAN SEA)
Martorelli E. *, Altobelli C.*, Chiocci F.L.*, D’Angelo S.**
*Dipartimento di Scienze della Terra, Università degli Studi di Roma “La Sapienza”, P.le A. Moro, 5, 00185, Roma, Italy
** Servizio Geologico –APAT-, Via Curtatone, 3, 00185, Roma, Italy
Western Pontine continental shelf is characterized by particular morpho-stratigraphic characters due to the geological setting. In fact, the continental shelf surrounds a volcanic archipelago located above a structural high separating two of the main intra-slope basins of the Tyrrhenian Sea (Palmarola and Ventotene Basins). During the present sea-level highstand, the islands are far from the Italian peninsula over 30 km so that terrigenous supply can not reach the continental shelf. As a consequence highstand deposits are usually thin with a scattered distribution. Furthermore, as commonly observed in the rest of the Tyrrhenian continental shelves, also transgressive deposits are absent as a result of their low potential of formation and /or preservation during the fast postglacial sea-level rise eventually associated to submarine erosion (i.e. ravinement surface). These factors cause a complex morphology of the inner and middle shelf areas characterized by a widespread occurrence of rock outcrops. The rock outcrops, that are mainly made up of volcanic rocks, became largely encrusted by coralligenous assemblage beyond 50 m w.d.
Deposits referred to the last glacial maximum (TDS deposits illustrated by Chiocci and Orlando, 1996; Martorelli et al., 2004) are only present in outer shelf areas, with thickness of some tens of meters and quite continuous distribution along the archipelago.
Despite the scattered occurrence and the scarce thickness of post-glacial deposits they provide interesting aspects linked to a complex interaction among physical and biological factors on sediments distribution. Sediment composition leads to consider the study area as a temperate carbonate shelf (Martorelli et al., 2002). In fact, post-glacial sediments are mainly made up of carbonate skeletal grains with a variable composition (mainly characterized by Forams, Bryozoa, Molluscs, Echinoderms, calcareous Red Algae –Rhodoliths-). Terrigenous sediments are usually subordinate and become prevalent only in the inner shelf where they are supplied by coastal erosion.
Sediment composition seems controlled by water depth, water transparency, hydrodynamic conditions and proximity to rock outcrops and seafloor gradient.
In particular water depth and water transparency act as general controlling factors whereas hydrodynamic conditions (e.g. currents and waves), rock outcrops and seafloor gradient represent more local factors.
CHIOCCI F.L.AND ORLANDO L. (1996) - Lowstand terraces on Tyrrhenian Sea steep continental slopes. Marine Geology 134, 127-143.
MARTORELLI E., CHIOCCI F.L., CIVITELLI G., CHIMENZ C., VENTURA G., ALTOBELLI C., BALOCCO A., BOSMAN A., CASSATA L. AND RASPAGLIOSI M. (2002) - Mid-Latitude Carbonate Sedimentation on a volcanic island shelf (Pontine Islands, Tyrrhenian Sea). Abstracts of the 2nd Annual Conference of the IGCP 464 Project (Continental shelves during the last glacial cycle), Cannenaya, Brasil, 63-64, 26/08-5/09/ 2002.
MARTORELLI E., CHIOCCI, F.L, PAZZINI A. (2004) - Lowstand depositional terraces surrounding Western Pontine Archipelago (Tyrrhenian Sea). Abstracts of the 32nd International Geological Congress, Florence, Italy, August 20-28.
THE MALDIVES PROJECT IN THE INDIAN
OCEAN MULTIPLE INTERACTING PARAMETERS
Paleoseismics & Geodynamics, Stockholm, Sweden, (firstname.lastname@example.org)
The Indian Ocean and the Maldives (our prime point of reference) are of special interest when it concerns active interaction of multiple parameters behind recorded changes in sea level, ocean circulation and climate (Mörner, 2000).
The Maldives lies in a major geoid depression of about 100 m. At the 20 ka glaciation maximum (LGM), local sea level in the Maldives seems to have been at about –150 m. We take this as a sign that the geoid relief during at LGM was significantly increased (due to rapid rate of rotation and mass redistribution). In the Maldives, there was a geoid deepening in the order of 30 m.
Subsequently, sea level rose from 20 ka to 4500 BP when the present level was reached. This rise was episodic as evidenced from submarine shorelines and submarine sea caves (recorded by diving, sampled and sometimes dated).
Most of the Maldives were previously held to be built up by Holocene catch-up reefs. According to our observations, this is only the case for minor parts, however. The vast majority of reefs are much older (of pre-LGM age). This is evidenced from deep karstification and observed shorelines and caves cut into pre-existing reefs. The Last Interglacial level seems to be at about +1.5-2.0 m.
The new sea level curve of the Maldives includes several sharp and rapid peaks in the last 4000 years. Those peaks cannot represent changes in oceanic water volume, but must refer to regional dynamic changes of decadal to centennial duration (i.e. some sort of “Super-ENSO-events”).
We have noted the E–W swings of ocean water between South America and Africa; when rising along one margin, sea fell at the other and viseversa. This is driven by changes in angular momentum. At the same time, we have noted the reversals of predominant direction of currents. This is likely to be linked to changes in the monsoonal regime. Intensive evaporation over the Indian Ocean makes the sea level depart negatively from the geoid surface by some decimetres.
At about 1970 sea level was rapidly lowered by 20-30 cm. Our observations records come from (1) multiple island morphology, (2) erosion/deposition levels, (3) lagoonal records, (4) swamp records, (5) biological information, and (6) verbal records from local fishermen. Besides, our records come from a large number of islands ranging over most of the Maldives (from latitude ~6oN to ~1oS). Therefore, we hold that our conclusions are firm, valid and solid. We interpret the fall in terms of increased evaporation and intensified NE-monsoon. This is consistent with stable isotope records from the Chagos Islands.
The coast of Bangladesh is today intermittently severely flooded. This seems not to have been the case at certain periods back in time. This may indicate the occurrence of significant changes in monsoonal regime in past millennia.
In the Maldives, condemned to become flooded in the next century, we see no traces what so ever of any on-going sea level rise; in coastal records as well in tide gauge records. All alarming talk about a strong and accelerating rise in global sea level is nothing but a myth.
Mörner, N.-A., (1995) Earth rotation, ocean circulation and paleoclimate, GeoJournal, 37, 419-430.
Mörner, N.-A., (2000) Sea level changes and coastal dynamics in the Indian Ocean, Integrated Coastal Zone Management, 1, 17-20.
Mörner, N.-A., (2003), Sea level changes in the Past, at Present and in the Near-Future. Global aspects. Observations versus Models, IGCP-437, Puglia (Italy), 2003, GI2S Coast, Research Publication, 4, 5-9.
Mörner, N.-A., (2004) Estimating future sea level changes from past records, Global Planet. Change, 40, 49-54.
Mörner, N.-A., (2004) The Maldives Project: a future free from sea-level flooding, Contemporary South Asia, 13, 149-155.
Mörner, N.-A., Laborel, J., Tooley, M., Dawson, S., Allison, W., Islam, S., Laborel, F., Collina, J. & Rufin, C., (2003) Sea level changes: the Maldives Project. Freed from condemnation to become flooded, IGCP-437, Puglia (Italy), 2003, GI2S Coast, Research Publication, 4, 175.
Mörner, N.-A., Tooley, M. & Possnert, G., (2004) New perspectives for the future of the Maldives, Global Planet. Change, 40, 177-182.
ENVIRONMENTAL IMPACT STUDY OF MARINE
SAND EXTRACTION FOR BEACH NOURISHMENT
L. Nicoletti, P. La Valle, D. Paganelli, M. Gabellini
I.C.R.A.M., via di Casalotti, 300 – 00166 Roma
Phenomena related to the recession of the coastline endanger natural “habitats”, economic activities (bathing tourism) and the security of public hard structures.
The increasing necessity to identify materials for beach nourishment poses the problem of new sources of materials. One of the possible solutions for beach nourishment, tested in many countries during the last decades and only in Italy in the last years, is the exploitation of “relict” sand. In fact, the new trend of research tends to build soft shore protection systems, able to favour the natural dynamics of beaches.
Since marine sand extraction involves important effects on marine ecosystems, dredging activities of “relict” sand must be always accompanied by specific environmental studies.
It is known that sand extraction involves physical and biological impacts. The most serious physical effects are related to substratum removal, alteration of bottom morphology and sedimentology, re-deposition of material and alterations of suspended particulate matter in the water column (De Groot, 1996; Newell et al., 1998). The most important biological impacts are related to benthic assemblages, living upon or inside the sediment (van Dalfsen et al., 2000).
In Italy, one of the first experiences of beach nourishment using “relict” sand was financed and realised in 1999 by the “Regione Lazio”. In this project, ICRAM carried out several investigations to assess environmental compatibility and environmental impact related to dredging activities for beach nourishment.
At present, there are no specific protocols and laws that regulate dredging activities for beach nourishment in Italy and in Mediterranean countries.
The aim of this paper is to propose an operative protocol, a methodology, based on the results reached through different experiences regarding the environmental study of “relict” sand extraction for beach nourishment.
De Groot, S.J., (1996) The physical impact of marine aggregate extraction in the North Sea, ICES Journal of Marine Science, 53, 1051-1053.
Newell, R.C., Seiderer, L.J., Hitchcock, D.R., (1998) The impact of dredging works in coastal waters: a review of the sensitivity to didsturbanceand subsequent recovery of biological resources on the sea bed, Oceanography and Marine Biology: an annual review, 36, 127-178.
van Dalfsen, J.A., Essink, K., Toxvig Madsen, H., Birklund, J., Romero, J., Manzanera, M. (2000) Differential response of macrozoobenthos to marine sand extraction in the North Sea and the Western Mediterranean, ICES Journal of marine Science, 57, 1439-1445.
MINERAL RESOURCES OF THE RUSSIAN ARCTIC
SHELF UNDER LAST GLACIAL MAXIMUM CONDITIONS
alekseev m.n. 1, patyk-kara n.g.2, drouchits v.a. 1
1- Geological Institute RAS, Moscow, Russia, email@example.com
2 - IGEM RAS, Moscow, Russia, firstname.lastname@example.org
Mineral resources of the Russian Arctic shelf area are very diverse. Valuable placer deposits and occurrences: of metals (gold, PGE, tin, iron, titan minerals, zircon, rare-earth, chromite), of diamonds and semiprecious stones (agate, chalcedony) rank first among mineral deposits. Practically unlimited deposits of building materials (sand, gravel, boulder-gravel mixtures, clay) rank next to them. There are also known manganese nodule accumulation and deposits of biogenic raw material: resources: shell rocks, mammoth tasks (ivory) accumulation, pearl finds [Patyk-Kara, Ivanova, 2003].
According to their minerogenetic profile determined by specialization of primary supply sources, intermediate collectors, lithogenetic conditions, some follow mineral mega-provinces and provinces may be distinguished in the Russian Arctic continental shelf [Atlas…, 2004]:
– West Arctic mega-province (White and Barents Seas): garnet and heavy minerals placer occurrences and diamond placers finds, coquina, manganese nodules, pearl finds;
– Central Arctic mega-province (eastern part of the Kara Sea – western part of the Laptev Sea): gold placers and diamond finds;
– East Arctic mega-province (eastern part of the Laptev Sea, East Siberian and Chukchi Seas): gold and tin (and rare-earth) placers), mammoth tasks (ivory) deposits.
Natural conditions of Last Glacial Maximum in the Russian Arctic are characterized by clear difference between the Western and the Eastern regions. The boundary between these regions run in the Central part of the Kara Sea, in the Yamal Peninsula area.
The shelf of the Western Arctic was of glacial type. During Last Glacial maximum the shelf glaciers had place here; sedimentation had “under ice” character and formed glacial-marine sediments. As a result, the whole area of the West Arctic mega-province has been greatly influenced by the Quaternary ice sheets; on one hand, they prevented active placer formation within the region, on the other, they controlled ways of sediment transportation at stages of glacier growth and decay. An onset of ice cover on Arctic seas was most important, as it reduced duration and intensity of wave action. That hindered separation of clastic material within littoral zone and suppressed formation of complex placers of heavy minerals.
Contrary to this area, the Eastern Arctic shelf was a vast periglacial space (“Mammoth steps” with sagebrush and cereals vegetation) where a specific ice-loam sedimentary unit “Edoma Suite” (“muck) was formed. The coastline was located to the north from Novaya Sibir’ Islands and the shelf was crossed by extended Palaeo-Lena, Palaeo-Indigirka, Palaeo-Kolyma and other drainage. Cryogenic sedimentation of ice-loam deposits abruptly reduced the area of placer formation which was restricted only by small island elevations and piedmont area. As a result, the most of ancient placers formed to this time were buried and later, according to sea expansion, were submerged.
Another group of mineral deposits of the Arctic shelf is directly related to Post-glacial marine sedimentation and lithodynamic conditions. On the one hand, it is represented by residual deposits – mammoth tusk (ivory) accumulations on tidal flats and point bars in river valleys at the “periglacial shelves” [Smirnov, 1998] and boulder and sandy-gravel deposits having glacial origin – at the “glacial shelves”. On the other hand, it includes chemogenic and biogenic deposits – manganese nodules and coquina accumulations in the superficial layer of bottom sediments (Barents and White seas) conforming to recent conditions of marine sedimentation.
Atlas ”Geology and Mineral Resources of Russian Shelves”. Moscow: Scientific World, 2004. 140 p.
Patyk-Kara N.G., Ivanova A.M., 2003. Geochemical prospecting for mineral deposits on the shelf. Moscow: Scientific World. 416 p.
Smirnov A. N., 2003. Fossil ivory. St. Petersburg: VNIIOkeangeologia. 172 p. (in Russian)
RHODOLITH FACIES DISTRIBUTION ON
THE PONTINIAN ISLANDS SHELF
Sañé Schepisi E., Abdelahad N. 1, Basso D. 2, Chiocci F.L. 3
1 Dip.to di Biol. Vegetale, Univ. di Roma “La Sapienza, Piazzale Aldo Moro 5, Roma
2 Dip.to Sc. Geologiche e Geotecnologie, Univ. Milano-Bicocca, Piazza della Scienza 4, Milano
3 Dip.to Sc. Della Terra, Univ. Di Roma “La Sapienza”, Piazzale Aldo Moro 5, Roma
This research based on the study of rhodoliths - pluricentimetric algal nodules formed by concentric crusts representing successive colonisations of non-geniculate corallinacean algae (Bosence, 1983a) - present along the continental shelf surrounding the Pontine Islands (Tyrrhenian Sea, Italy) was carried out by Side Scan Sonar data interpretation (460 kmq), ROV images observation (68 ROV films) and analysis of algal samples (49 grabs).
Such study allowed us to:
-estimate the abundance and distribution of the different rodolith growth forms
-identify the different coralline algae species.
More than 800 living rhodoliths were collected at 49 stations (on a total of 235 stations) located in a bathymetric range of 40-110 m. Rhodoliths dimensions are: 1_1.5 cm (40 % of specimens), 1.5_2 cm (33 % of specimens) or 3_3 cm (27 % of specimens). The most abundant morphological groups according to Basso (1998) classification are:
-prâlines (50 % of specimens), that is, little nodules with protuberances or short branches and a compact internal structure
-unattached branches (41 % of specimens)
Rhodoliths “boxwork” are only 9 % of specimens and are characterized by an internal structure with voids due to long periods of growth under calm conditions interrupted by episodes of overturning and/or partial covering by sediments, with evident sedimentary fillings.
In the study area prâlines and unattached branches are registered in shallower water (40-80 m of depth) than rhodoliths “boxwork” (abundant from 80 to 110 m of depth); this bathymetric distribution is related to the different hydrodynamic conditions necessary for the development of such morphological groups (Basso, 1998). Prâlines generally have a columnar structure (55 % of pralines), even if laminar (20 % of pralines) and branched (25 % of pralines) structures are present. The bathymetric distribution of these different structures is also related to hydrodynamic conditions (Basso, 1998), as follows: columnar and laminar prâlines are abundant from 40 to 70 m; branched structure prevail from 70 to 80 m.
The petrographic microscope analysis led us to identify: Lithothamnion minervae Basso, Lithothamnion valens Foslie, Spongites fruticulosus Kützing, Lithophyllum racemes (Lamarck) Foslie, Lithophyllum incrustans (Philippi) and Phymatolithon calcareum (Pallas) W. H. Adey et D. L. McKibbin.
The comparison between Side Scan Sonar data (covering the shelf area) and rhodoliths distribution highlights that rhodoliths are mostly related to the high backscatter sonar facies, and are associated to sediments mainly made up by coarse skeletal grains. As confirmed by ROV images, such areas with abundant rhodoliths are mainly distributed in the saddle connecting Ponza and Palmarola and in NW Palmarola, whilst they lack in the Eastern side of Palmarola and Ponza Islands. In some cases (saddle between Palmarola and Ponza, S part of the saddle between Ponza and Zannone) rhodoliths are associated to coarse grained sediment patches corresponding to an inhomogeneous sonar facies (succession of high and low backscatter belts).
The integration of the available data on rhodoliths (growth form, structure, dimension, species) may suggest some considerations about hydrodynamic condition in the areas characterized by their presence:
1) the saddle between Ponza and Palmarola Islands, the saddle between Ponza and Zannone and NW Palmarola should represent areas with relatively high hydrodynamism
2) NW Ponza may be considered an area with relatively low energy.
Basso, D., 1998, Deep rhodolith distribution in the Pontian Islands, Italy: a model for the paleoecology of a temperate sea. Palaeogeography, Palaeoclimatology, Palaeoecology, 137: 173-187.
Bosence, D. W. J., 1983a, Description and Classification of Rhodoliths (Rhodoids, Rhodolites). In Peryt, T. M. (ed.), Coated Grains: 218-224, Springer-Verlag, Berlin.
PRESERVATION OF COASTAL LANDSCAPES
DURING THE HOLOCENE TRANSGRESSION, BRAS D' OR LAKES, NOVA SCOTIA
John Shaw and Robert B. Taylor
Geological Survey of Canada (Atlantic), Bedford Institute of Oceanography, Dartmouth, Nova Scotia B2Y 4A2, Canada.
A number of models have been proposed to show how the coastline of Atlantic Canada responds to sea-level rise. In the drumlin-coast model (Boyd et al., 1987), it was shown that beach and estuarine deposits move landwards during the transgression, leaving little trace of their former presence on the inner shelf, except for boulder shoals (the remnants of drumlins and therefore termed 'drumlin scars') and a veneer of sand and gravel overlying estuarine deposits. However, in the Bras d' Or Lakes - a microtidal inland sea - early Holocene coastal deposits are well preserved at depths of 25 metres and shallower.
The Bras d' Or Lakes are located in Cape Breton Island, Nova Scotia, and are comprised of a northern and southern basin, separated by a narrow strait; they are connected to the Atlantic Ocean by a narrow channel with a -8 m sill depth. We demonstrate that the Bras d' Or Lakes were formerly freshwater, and became marine c. 5.5 to 6.0 ka BP (radiocarbon years) when the ocean flooded across the sill. The northern basin has few glacial deposits, and hence few well-developed coastal deposits; however, a major incised and braided river valley is well preserved. The southern basin has large numbers of drumlins that provided anchors and sources of sediment for beaches. Multibeam bathymetry reveals beaches, spits, barrier-beaches, and looped barriers at -23 to -25 m. They are composed of gravel and have a distinctive backscatter signature. Erosional coastal terraces occur in some areas. We have also mapped submerged drumlins. Unlike the flat drumlins scars on exposed coasts, the submerged drumlins in the lakes preserve much of their previous relief, and have distinctive 'tails' that point towards the modern coast.
The good preservation of ancient coastal deposits is attributed to: 1) the comparatively low wave energy of the lakes; and 2) the rapid onset of the transgression when the ocean breached the sill. The preservation of these deposits represents an important modification of earlier models of coastal evolution in this region. While estuarine deposits played an important role in the drumlin-coasts model, they are absent from the submerged coastal systems in the Bras d' Or Lakes.
The socio-economic implications of the research include: 1) improved definition of lobster habitat in the lake; and 2) recognition that the submerged coastlines may contain archaeological evidence of the aboriginal peoples who formerly lived in the region, perhaps ancestors of the Mi'Kmaq First Nation who inhabit the region today.
Boyd, R., Bowen, A.J., and Hall, R.K. 1987. An evolutionary model for transgressive sedimentation on the Eastern Shore of Nova Scotia. In: Glaciated Coasts, ed. D.M FitzGerald and P.S. Rosen. Sand Diego, Academic Press. pp. 87-114.
HOLOCENIC COASTAL EVOLUTION OF PALMAROLA
ISLAND (TYRRHENIAN SEA)
Silenzi Sergio1, Devoti Saverio1, Molinaro Antonella2 and Zarattini Annalisa3
1 ICRAM - Central Institute for Marine Research, Via Casalotti 300 - 00166 Roma, Italy (email@example.com)
2 Tethys s.r.l. – Indagini Geologiche e Ambientali, Via G. Miani 40 - 00154, Italy
3 Soprintendenza per i Beni Archeologici del Lazio, Via Pompeo Magno, 2 - 00192 Roma, Italy
A geomorphological and structural underwater survey of Palmarola Island (Southern Latium) has been performed (Fig. 1; Silenzi et al., 2004), aimed at obtaining both a geographic background information on the availability to Humans of obsidian deposits since the Neolithic Age, and a morphological pattern of the submerged portion of the Island. The survey was focused on both erosional forms (such as notches, abrasion platforms, evorsion pools, marine caves, canyon) and depositional forms (beach deposits). A compared analysis of the surveys carried out has outlined that the coastal morphology of the island has been controlled by lithologies and by tectonics; it also described the evolutionary genesis of some erosional and depositional forms.
Fossil beach deposits derive from the cementation and from the subsequent breaking up of previous emerged and submerged beach deposits; these processes occurred in various phases (polygenic conglomerates) in coastal environments which are similar to the current one. The actual deposits, too, show a polygenic origin, especially in the submerged portion; this implies that not only do they originate from the present breaking up of the coastal rocks, but also from the re-emerged cemented paleo-deposits.
The main tectonic pattern, at least in the western and northern portions of Palmarola Island is oriented N100. This is to be related to the presence of the numerous underwater canyons and marine caves found, set up on such tectonic discontinuities.
By comparing the glacio-hydro-isostatic model, elaborated for this area by Lambeck et al. (2004), with AMS dating of beach deposits, we can assume that since the last 2.5 ka BP the southern sector of Palmarola appears to be tectonically stable and therefore it has also been possible to verify the lack of uplifts in the recent Holocene; the characteristics of the paleo-beach deposits therefore match the glacio-hydro-isostatic models for this area of the Tyrrhenian Sea. The primitive features of the Island made its dockings and their use by non-technological man very difficult. The pre-historic dockings and the use of the island, thought to be in a first analysis different from what can be observed today, have instead proven to have been analogous to the current ones.
Silenzi, S., Molinaro, A., Devoti, S., Nisi, M. F., Zarattini, A., (2004) Underwater geomorphological survey of Palmarola Island (Tyrrhenian Sea, Southern Latium): Holocenic coastal evolution and neotectonic evidences, Quaternaria Nova, VIII, 23-35.
Lambeck, K., Antonioli, F., Purcel, T., Silenzi, S., (2004) Sea level change along the Italian coast for the past 10,000 yrs, Quaternary Science Reviews, 23, 1567-1598.
COASTAL-MARINE PROCESSES AND SEDIMENT
SUPPLY DURING THE POST LGM TRANSGRESSION IN THE NORTHERN PART OF THE
ARGENTINE CONTINENTAL SHELF
Roberto A. Violante
Argentine Hydrographic Survey, Department of Oceanography, Division of Marine Geology and Geophysics. Av. Montes de Oca 2124, C1270ABV, Buenos Aires, Argentina.
GM transgression had a profound effect on the northern part of the Argentine Continental Shelf as it was deeply modelled during the event by coastal and marine processes. This work includes information from Urien and Ewing (1974), Parker and Violante (1982), Cavallotto et al. (1995) and Violante and Parker (2004) and advances on their results.
The flooding of the pre-transgressive surface initially occurred at low speed, but with the progress of the transgression the rate of sea-level rise increased (27 mm/yr between 12 and 8.6 Ka BP) and then decreased again (9.4 mm/yr) before it stabilized near +4 m a.s.l. at 6 Ka BP. In this way the transgression sweept the substrate by erosional retreat of the shoreface and consequent landward migration of the shoreline. Reworking and remodelling of the present shelf surface depended on interaction among the rate of relative sea-level rise, substrate composition and topographic gradient, coastal configuration, climate, wave energy, tidal range, littoral drift, sediment availability and deposition-erosion balance, which determined the effectiveness of the ravinement process.
The main aggradation process was the formation of littoral barriers. A important aspect to consider is the sediment supply that fed the barriers. Delivery of sediments to the littoral systems comes from three sources: 1) shelf sandy reservoirs resulting from shoreface erosion (onshore-offshore transport), 2) fluvial activity and 3) northward littoral drift (longshore transport). 1 and 2 changed with time, whereas 3 is considered to have been relatively invariable. During the first stages of the transgression, when the shelf was very narrow, fluvial influence was significant as base-level was low and rivers had large capability for transporting sediments. However, the main river in the area (Río de la Plata) flowed at that time to the north and joined the sea near southern Brazil. Since prevailing regional littoral drift was to the north, fluvial sediments could not have been transported to the south, and hence the dominant sediment supply in the study area -which was responsible for barriers formation- was the northward littoral drift.
As transgression proceeded, new barriers formed on the shore while erosion of the previous barriers left a blanket of sediments that were stored on the shelf surface (progressively widened). At the same time the rise in base-level induced a decreasing in fluvial sediment transference to the sea as sediments got trapped in estuaries, which were in turn reached by the rising sea and exposed to coastal erosion so resulting in an additional provision of sediments to the shelf. As a consequence the shelf was progressively covered by a mantle of relict sediments that became with time much more important as a source of sediments to feed new barriers. Finally, relict deposits were reworked during the regressive event occurred after 6 Ka BP and adjusted to the present hydrodynamic regime.
The patterns of morphology, stratigraphy and sedimentology of the studied sector of the shelf allow to consider it, following the concepts by Swift (1976), as resulting from a "passive" regime of autochthonous sedimentation acting during post-LGM times, what means that the shelf underwent rapid transgression and shoreline retreat with sediment bypassing via shoreface erosion rather than significant fluvial sediment supply. Characteristic features are at present large constructional bodies like shoal retreat massifs overprinted by linear shoals and ridge-swale topography, molded into a surficial "relict to palimpsest" sand sheet that resulted from reworking of former transgressive barriers complexes.
Cavallotto, J.L., Parker, G. and Violante, R.A. 1995. Relative sea level changes in the Río de la Plata during the Holocene. 2nd. Annual Meeting IGCP 367: Late Quaternary coastal records of rapid change: application to present and future conditions, Antofagasta (Chile) Abstracts: 19-20.
Parker, G. and Violante, R.A. 1982. Geología del frente de costa y plataforma interior entre Pinamar y Mar de Ajó, Prov. de Buenos Aires. Acta Oceanográphica Argentina, 3 (1) : 57-91.
Swift, D. 1976. Continental shelf sedimentation. In: Marine sediment transport and environmental management, D. Stanley and D. Swift (Eds.). J.Wiley & Sons, Inc. 15: 311-350.
Urien, C.M. and Ewing, M. 1974. Recent sediments and environments of Southern Brazil, Uruguay, Buenos Aires and Río Negro Continental Shelf. In: The Geology of Continental Margins, C. Burk and Ch. Drake (Eds.). Springer-Verlag, New York: 157-177.
Violante, R.A. and Parker, G. 2004. The post-Last Glacial Maximum transgression in the de la Plata river and adjacent inner continental shelf, Argentina. Quaternary Int., 114 (1): 167-181.
GEOMORPHOLOGICAL, DEPOSITIONAL AND
FORAMINIFERAL INDICATORS OF
LATE QUATERNARY TECTONIC UPLIFT IN ISKENDERUN BAY, TURKEY
Valentina Yanko-Hombach,*, Hayrettin Koralb, Niyazi Av_arc, Irena Motnenkoa, Mary McGannd
Avalon Institute of Applied Science, Charleswood Technology Center, 3227 Roblin Blvd, Winnipeg MB R3R 0C2, Canada; bDepartment of Geology, Istanbul University, Avcilar 34850, Istanbul, Turkey; cDepartment of Geological Engineering, Çukurova University, Balcali 01330, Adana, Turkey; dU.S. Geological Survey, Menlo Park, California, USA 94025
Bay is a major shallow embayment in the eastern part of the Mediterranean
Sea, where the African and Anatolian plates converge. This tectonically
active basin was investigated for oceanographic, sedimentological, geochemical,
and foraminiferal parameters.
On the basis of data acquired, living and fossil foraminifera in 284 grab and 54 gravity-core samples were determined, basin-floor bathymetry of the bay constructed, radiocarbon ages of sediments and fossils ascertained and depositional environments reconstructed.
It is discovered that for the last 13.5 ka water masses were stratified and sedimentation was discontinuous within the basin that is characterized by irregular sea-bottom morphology. Sedimentation rate was very slow varying in time and space from 0 to 0.012 cm y-1. Foraminiferal distributions were spatially varied and discontinuous, and in the cores indicated a reversal from deep to shallow marine conditions. These irregularities were attributed to active tectonics in the bay and a major tectonic uplift of the bay since late Pleistocene.
It is suggested that Iskenderun Bay may constitute a model for other tectonically active regions where the foraminiferal data may exhibit similarly complex patterns. Lack of correlation between cores taken at similar depths, as well as in downcore profiles, may be the result of the effects of differential basinal movement, slumping, and overturning. In such cases, not only is a very precise knowledge of the foraminiferal ecology of prime importance to unravel the paleoenvironment, but also establishing a detailed lithology and radiocarbon-based chronology is indispensable.
Kronfeld, J., Yanko, V., Vogel, J.C., Avsar, N., Koral, H. 1996. Major tectonic uplift in Iskenderun Bay, easternmost Mediterranean Sea. Geol. Soc. Am., Annual Meeting, Denver, Colorado, Abstracts with Programs 28, pp. 395.
Koral, H., Kronfeld, J., Avsar, N., Yanko, V., Vogel, J.C., 2001. Major recent tectonic uplift in Iskenderun Bay, Turkey. Radiocarbon 43, 957-963.
THE BLACK SEA FLOOD CONTROVERSY
IN LIGHT OF THE LATE QUATERNARY HISTORY OF THE BLACK SEA
Institute of Applied Science, Charleswood Technology Centre, 3227 Roblin
Blvd, Winnipeg MB R3R 0C2, Canada, firstname.lastname@example.org
A prevailing Western idea about a past ancient flood in the region by Ryan et al. (1997) suggests that salty Mediterranean water catastrophically flooded the brackish Neweuxine lake about at 7.2 ka BP and links the event to the biblical story of Noah’s Flood.
In support of the Flood Hypothesis, submerged coastline (s?) dated between 15.0 and 7.9 ka BP was described on the Romanian and Turkish shelf at depth ranging from -95 m to -155 m. The uniform drape of mud overlapping coastline (s?) was dated between 7.8 and 4.0 ka BP (e.g., Ballard et al., 2000).
In contradiction to the Flood Hypothesis Görür et al. (2000) discovered that level of the Neweuxine lake was -18 m at 7.2 ka BP. Aksu et al. (2002) proposed that unabated Black Sea outflow across the Bosphorus prevented the northward advection of Mediterranean water and organisms into the Black Sea in early Holocene.
In the late 90th a large-scale marine geological survey of the Ex-USSR shelf was largely completed (Yanko, 1990). Thousands of cores and tens of thousands kilometres of high-resolution seismic profiles have been studied in a multidisciplinary effort. Palaeoclimatic, tectonic and sedimentological history of the basin was reconstructed. High-resolution Quaternary biostratigraphy supported by hundreds of radiocarbon records was established enabling high-resolution reconstruction of sea level oscillations since LGM.
At 20-15 ka BP isolated Neweuxine lake was at -100 m below present. At 12 ka BP the level reached -20 m due to discharge of melting water from the Caspian sea and major rivers. At 11-10 ka BP the level of the basin dropped to -65 m. It increased again to -35 m at 9.4 ka BP in a full tandem with global sea level change. The Black Sea was reconnected with the Sea of Marmara allowing the first wave of euryhaline (1-26‰) Mediterranean immigrants. At 8.0 ka BP the sea level reached -15 m enabling the second wave of mainly strictoeuryhaline (11-26‰) immigrants. At 7.2 ka BP the sea level rose to -10 m and the number of Mediterranean mainly polyhaline (18-26‰) species increased providing the third wave of faunal immigration.
The high-resolution geological and palaeontological records obtained directly on the Black Sea shelf contradict to both the Flood and Overflow Hypotheses. As no marine sediments younger than 7 ka BP are discovered in the Bosphorus (Kerrey et al., 2003) we are inclined to reject a cataclysmic role of the Bosphorus in early Holocene connection. An alternative route between adjacent basins should be considered.
Aksu A.E., Hiscott R.N., Kaminski M.A., Mudie P.J., Gillespie T., Abrajano T. & Ya_ar, D. 2002. Last Glacial-Holocene palaeoceanography of the Black Sea and Marmara Sea: stable isotopic, foraminiferal and cocolith evidence. Marine Geology, 190: 119-149.
Ballard, R. D., Coleman, D. F. ,G. D. Rosenberg. 2000. Further evidence of abrupt Holocene drowning of the Black Sea shelf. Marine Geology, 170 (3-4): 253-261.
Görür, N., Ça_atay, N., Emre, Ö., Alpar, B., Sakinç, M., Islamo_lu, Y., Algan, O., Erkal, T., Keçer, M., Akkök, R., Karlik, G. Is the abrupt drowning of the Black Sea shelf at 7150 yr BP a myth? Marine Geology, 176: 65-73.
Kerrey, E., Meric, E., Tuno_lu, C., Kelling, G., Brenner, R.L., Do_an, A.U. 2003. Black Sea-Marmara Sea Quaternary connections: New data from the Bosphorus, Istanbul, Turkey, Palaeogeography, Plaeoclimatology, Palaeoecology, 3256: 1-19.
Ryan W. B. F., Pitman III W. C., Major C. O., Shimkus K., Moskalenko V., Jones G. A., Dimi-trov P., Görür N., Sakınç M., Yüce, H. 1997. An abrupt drowning of the Black Sea shelf, Marine Geology 138: 119-126.
Yanko V. 1990. Stratigraphy and palaeogeography of marine Pleistocene and Holocene deposits of the southern seas of the USSR. Mem. Soc. Geol. Ital., 44: 167-187.
GROUND-TRUTHING OF BOOMER SEISMIC PROFILES
IN Tai O BAY,
HONG KONG SAR, CHINA
W.W.-S. Yim1, H.K. Wong2, A. Bahr2, L.S. Chan1, G. Huang3, T. Lüdmann2 and W.N. Ridley Thomas4
1 Department of Earth Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China
2 Institute of Biogeochemistry & Marine Chemistry, University of Hamburg, Bundesstraße 55 D-20146 Hamburg, Germany
3 Guangzhou Institute of Geography. 100 Xian Lie Road, Guangzhou 510070, China
4 EGS (Asia) Limited, 9/F, Somerset House, Taikoo Place, 979 King’s Road, Hong Kong SAR, China
High resolution boomer seismic profiles in Tai O Bay, a shallow bay located in the pro-delta region of the Pearl River Delta was ground-truthed using discontinuously sampled rotary boreholes penetrating bedrock and continuously vibrocores. Based on available information and the measurement of physical properties in cores including compressional wave velocity, water content, density and magnetic susceptibility, the following conclusions are drawn:
(1) A sedimentary sequence dominated by transgressive system tracts showing evidence for four interglacial-glacial cycles have been identified. Marine deposits are represented by Marine Isotope Stage (MIS) 1, 5, 7 and 9 while terrestrial deposits are represented by MIS 2-4, 6, 8 and 10.
(2) A total of 9 unconformity-bounded seismic units overlying weathered Jurassic tuffites divisible into 8 system tracts can be distinguished.
(3) A seismic velocity of 1.6 km/second is found to be too high for delineating the MIS 1/MIS 2 boundary. A lower value of 1.5 km/second is recommended.
(4) Palaeo-desiccated crusts/palaeosols are identified on top of MIS 5, 7 and 9 marine deposits. Their presence is attributed to acid-sulphate soil development during glacial deposits when the continental shelf was sub-aerially exposed.
(5) Compressional wave velocity, moisture content, density and magnetic susceptibility measurements are found to be useful for distinguishing between the marine and terrestrial deposits. Generally marine deposits show lower values while terrestrial deposits show higher values. Palaeo-desiccated crusts/palaeosols developed on pre-Holocene marine deposits show higher magnetic susceptibility values in comparison to their lower part.
(6) The maximum thickness of the MIS 1 marine deposits found is 21.5 m or a mean Holocene sedimentation rate of ca. 2.65 m/ka without taking into account self-weight consolidation. This is the greatest thickness found in Hong Kong.
(7) Because the MIS 1 marine deposits have never been affected by sub-aerially exposure, the marine fossils are generally well preserved. On the other hand, marine fossils in Pre-Holocene marine deposits may have been completely destroyed through post-depositional processes.
(8) Terrestrial deposits including colluvium and alluvium were deposited through colluvial-alluvial fans during glacial periods.
(9) The chronology of the sequence is supported by dating samples from other parts of Hong Kong including radiocarbon (MIS 1), uranium-thorium (MIS 5 and 9) and thermo-luminescence (MIS 8).
(10) Biogenic gas seep on the sea floor is identified south of Tai O Island. This is attributed to the bacterial decomposition of plant matter present in the underlying sediments.
PALMAROLA: PREHISTORIC OBSIDIAN TRADE
Ministero per i beni e le attività culturali,Soprintendenza per i beni archeologici del Lazio, Nucleo Operativo di Archeologia Subacquea
Via Pompeo Magno 2, 00192 Roma,Italia
Tel 06 32659640, fax 063214447
The territory of Soprintendenza Archeologica per il Lazio includes a complex and rich coastal system. Besides representing the natural line of coast, with the sequence of the Pontine plain, the plain of Fondi, the marshes, the projecting promontories, such as mt. Circeo, and landscapes of dunes or cliffs, and the Pontine Islands, it is especially marked by traces of human activity in various periods.
The Soprintendenza Archeologica per il Lazio is carrying out a project on the coast, called the “ Archaeological Sea Registration Project”. The project aims to effect a detailed census and an analysis of the state of knowledge and preservation of the main submerged coastal archaeological remains of southern Latium. It has already had important results with regard to research and protection, as it is necessary to go beyond the point of view of emergengy operation through programming operations that take account the many valences for research and control of the territory.
We have begun with the census of the known ancient port structures, fish-ponds, land deposits later submerged and ancient wrecks, considering the maritime cultural landscape as a part of an overall site rather than as separate objects from the Prehistory to the Medieval Age
of a pothole in Cala Frontone
|obsidian blocks in the coarsest hyaloclastic facies||R/V Universitatis
|hyaloclastic deposits intruded
by dykes at Cala del Core
seafloor and small rock at Cala Felce (sulfur vents)
||final discussion at Frontone Beach
Rosa stacks: submarine extension of the outer stack incised in a rhyolitic
||dinner at Frontone Beach