International Geological Correlation Program #464               home

Continental Shelves during the Last Glacial Cycle: Knowledge and Applications

T05.03 Topycal Symposium at
XXXII International Geological Congress

26 August 2004



Program

Abstracts

  ita2004


CONFERENCE PROGRAM


Thursday 26 August.
Fortezza Da Basso
, Florence

SESSION
249 Continental shelves during the last glacial cycle

Conveners and Chairpersons:
Chiocci Francesco L., Chivas Allan R.

09:00 - 09:15        THE IGCP464 PROJECT: SCIENTIFIC AND APPLICATIVE RELEVANCE OF CONTINENTAL SHELF STUDIES
                          ON DEVELOPED AND DEVELOPING COUNTRIES
®
                          Chiocci Francesco Latino *, Chivas Allan Ross

09:15 - 09:30        THE ACCUMULATION OF ORGANIC CARBON ON CONTINENTAL SHELVES ®
                          Chivas Allan Ross *, Mahiques Michel, Boski Tomasz, Shirodkar Prabhaker

09:30 - 09:45
        CONTINENTAL SHELF EVOLUTION DURING THE LAST GLACIAL CYCLE - INFLUENCE ON HUMAN CULTURE ®
                          Hetherington Renée *

09:45 - 10:00       
RAPID TRANSGRESSIONS INTO SEMI-ENCLOSED BASINS SINCE THE LAST GLACIAL MAXIMUM ®
                          Lericolais Gilles *, Chivas Allan Ross, Chiocci Francesco Latino, Uscinowicz Szymon, Bo Jensen Jorn, Lemke Wolfram, Violante Roberto                           Antonio

10:00 - 10:15
        SUB-AERIAL EXPOSURE OF CONTINENTAL SHELVES DURING GLACIAL PERIODS AND THE TERMINATION OF ICE                                       AGES ®
                          Yim Wyss Wai-Shu *

10:30 - 10:45
        CHEMISTRY OF THE RIVERS IN THE GULF OF CARPENTARIA DRAINAGE DIVISION (N-AUSTRALIA): PALAEOCLIMATIC                                   IMPLICATIONS ®
                          Cendón Dioni I. *, Chivas Allan Ross, Wyndham Timothy, García Adriana

10:45 - 11:00
        GLOBAL CHANGE AND SUBMARINE GROUNDWATER DISCHARGE ®
                          Kontar Evgeny *

11:00 - 11:15
        SHALLOW GAS IN SAN SIMON BAY (NW SPAIN) ®
                          Garcia-Gil Soledad *, Iglesias Jorge

11:15 - 11:30       
PALAEOENVIRONMENTAL EVOLUTION OF THE NORTHERN ARGENTINA CONTINENTAL SHELF DURING THE POST-LGM
                          TRANSGRESSION
®
                          Violante Roberto Antonio *

11:30 - 11:45       
LATE QUATERNARY EVOLUTION OF THE INNER SHELF OFF SÃO SEBASTIÃO, SOUTHEASTERN BRAZIL: IMPLICATIONS                               FOR THE BRAZILIAN SEA-LEVEL CURVE ®
                          De Mahiques Michel *, Klein Daniel Andreas, Rodrigues Marcelo, Furtado Valdenir Veronese


LIST OF POSTER PAPERS

POSTGLACIAL EVOLUTION OF THE WESTERN ARCTIC SHELF ENVIRONMENTS ®
Ivanova Elena V. *

FACIES SYSTEM OF THE BARENTS SEA SINCE THE LAST GLACIAL MAXIMUM TO RECENT ®
Murdmaa Ivar *

ARE EMERGED SHELVES A SOURCE FOR LOESS? ®
Smykatz-Kloss Bettina, Zoeller Ludwig R. *, Antoine Pierre 

ROCK MAGNETIC RECORDS OF THE SEDIMENTS OF THE EASTERN ARABIAN SEA: EVIDENCE FOR LATE QUATERNARY CLIMATIC CHANGE ®
Anil Kumar A., Purnachandra Rao Venigalla *, Patil S.K., Kessarkar Pratima M.,Thamban M.


CONTINENTAL SHELVES AND MODERN COASTAL ENVIRONMENTS: WHAT CAN WE EXPECT DURING LOW STANDS OF THE OCEAN? ®
García Adriana *, Chivas Allan Ross, Reeves Jessica M., Holt Sabine, Cendón Dioni, Van Der Kaars Sander

CLAY MINERALOGY OF THE KUALA TERENGGANU, MALAYSIA NEARSHORE SEDIMENTS ®
Abdullah Nor Antonina *, Mohd Shazili Nor Azhar, Darus Siti Zauyah, Mohd Husain Lokman, Ahmad Shamsuddin, Yunus Kamaruzzaman, Yaakob Rosnan

SEA- LEVEL AND ENVIRONMENTAL CHANGES SINCE THE LGM IN THE DE LA PLATA RIVER (ARGENTINA) ®
Cavallotto José Luis *

LOWSTAND DEPOSITIONAL TERRACES SURROUNDING WESTERN PONTINE ARCHIPELAGO (TYRRHENIAN SEA) ®
Martorelli Eleonora *, Chiocci Francesco Latino, Pazzini Alfredo


THE "ATLAS OF SUBMERGED DEPOSITIONAL TERRACES ALONG THE ITALIAN COASTS" ®
Chiocci Francesco Latino, D'Angelo Silvana, Romagnoli Claudia *









CONFERENCE ABSTRACTS




CLAY MINERALOGY OF THE KUALA TERENGGANU, MALAYSIA NEARSHORE SEDIMENTS

ABDULLAH NOR ANTONINA 1, MOHD SHAZILI NOR AZHAR 1, DARUS SITI ZAUYAH 2, MOHD HUSAIN LOKMAN 3, AHMAD SHAMSUDDIN 1, YUNUS KAMARUZZAMAN 1, YAAKOB ROSNAN 3

presenter's e-mail: norantonina@yahoo.com

1 - KUSTEM, KUALA TERENGGANU, MALAYSIA
2 - UPM, SERDANG, SELANGOR, MALAYSIA
3 - INOS, KUSTEM, KUALA TERENGGANU, MALAYSIA

A study was conducted to determine the clay minerals present in the Kuala Terengganu nearshore sediments. Thirty sediment samples were collected during the cruise of the UNIPERTAMA VII from the coastal areas of Kuala Terengganu. Smith McIntyre grab was used to collect the sediment sample in the area. Identification of clay minerals using XRD was applied to the determination of the clay mineralogical composition of sediments.Three (3) groups of clay minerals are dealth with such as; kaolinite, illite and smectites. Results showed that stations 18, 19 and 23 are dominant with smectite while station 2 had no trace of smectite and illite. On the other hand stations 12 and 13 had no traces of smectite and kaolinite, respectively and the rest of the stations had few amounts of smectite, illite and kaolinite.





ROCK MAGNETIC RECORDS OF THE SEDIMENTS OF THE EASTERN ARABIAN SEA: EVIDENCE FOR LATE QUATERNARY CLIMATIC CHANGE

ANIL KUMAR A. 1, PURNACHANDRA RAO VENIGALLA 1, PATIL S.K. 2, KESSARKAR PRATIMA M. 1, THAMBAN M. 1

presenter's e-mail: vprao@darya.nio.org

1 - National Institute of Oceanography, Dona Paula - 403 004, Goa, India
2 - Indian Institute of Geomagnetism, Alibagh-402 201, Maharashtra, India


Rock-magnetic measurements together with grain size, acid-insoluble residue (AIR), organic carbon (OC) and CaCO3 content of the 15 gravity cores sediments off western India indicate three types of cores. Type 1 cores are abundantly terrigenous in Holocene and lime muds in the late Pleistocene section. Calcareous mud/sand-dominated and terrigenous material-dominated sediments occur in Type 2 and Type 3 cores, respectively. The magnetic susceptibility (MS) values are highest in terrigenous-dominated material of the cores off Saurashtra-Ratnagiri, followed by Indus-Gulf of Kachchh and then Mangalore-Cape Comorin. MS values are high in terrigenous silt and, negative / slightly positive for lime mud/sand-dominated sediments.
Down core distribution of mineral magnetic parameters reveal that the glacial sediments off Indus show high AIR, low MS associated with high coercivity minerals and low OC and CaCO3, while those off SW India show low AIR, low MS associated with low coercivity minerals and high OC, CaCO3 and 18O values. The early Holocene sediments everywhere showed high MS associated with high AIR and low OC, CaCO3 and 18O values. These imply that during the LGM arid climate prevailed over the northwestern India leading to the predominant eolian sedimentation. While in the SW India the influence of hinterland flux is less evident, but convective mixing associated with the NE monsoon resulted in high productivity. During the early Holocene intense SW monsoon resulted in high precipitation on land and, consequently high AIR associated with high MS in the offshore sediments. The intense SW monsoon conditions in the Holocene prevailed until about 5 ka.
MS variations are largely controlled by the provenance, magnetizable material and grain size of the sediments. Regional climatic signals obtained through magnetic concentrations are sometimes modified by other factors. When used along with other conventional methods, rock magnetic studies serve as a potential complementary technique to understand the paleoclimate.




SEA- LEVEL AND ENVIRONMENTAL CHANGES SINCE THE LGM IN THE DE LA PLATA RIVER (ARGENTINA)


CAVALLOTTO JOSÉ LUIS 1

presenter's e-mail: jlcavallotto@hidro.gov.ar

1 - argentina hydrographic service


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.






CHEMISTRY OF THE RIVERS IN THE GULF OF CARPENTARIA DRAINAGE DIVISION (N-AUSTRALIA): PALAEOCLIMATIC IMPLICATIONS


CENDÓN DIONI I. 1, CHIVAS ALLAN ROSS 1, WYNDHAM TIMOTHY 2, GARCÍA ADRIANA 1

presenter's e-mail: dcendon@uow.edu.au

1 - School of Earth and Environmental Sciences, University of Wollongong, NSW, Australia
2 - Earth Environments, Research School of Earth Sciences, Australian National University, ACT, Australia



The rivers surrounding the Gulf of Carpentaria represent one the most important drainage systems in Australia, accounting for up to 24.7% of all runoff waters in the continent. All these rivers debouch in a particularly climatically sensitive area. There is a continuing discussion on the possible interruption or variations in the intensity of monsoonal activity in the area, linked to sea-level fluctuations. All these changes have been registered in the complete sedimentary record of the Gulf of Carpentaria spanning the Quaternary and much of the Neogene and oscillating between marine and lacustrine conditions. In the present study we establish correlations between the chemistry of modern rivers and the chemistry recorded in the fossil record during the lacustrine phase prior to the 9.7 ka marine transgression (MIS 2/1).

We assume that the regional bedrock lithologies have not significantly changed over the last 70 ka and that rivers during the latest lacustrine "Lake Carpentaria" phase would have drained terrains of a similar chemical signature to modern outcropping materials. Therefore we should be able to establish links between the chemistry of the modern rivers and the chemistry preserved in the fossil record of Lake Carpentaria.

We have sampled water from all the major rivers entering the Gulf of Carpentaria from the Jardine River (Qld) to the Roper River (NT) during both the dry and wet seasons. The general chemistry of the waters has been determined for major, trace and REE elements using ICP-MS and IC analytical techniques. The 87Sr/86Sr isotopic signatures have also be determined in all samples by MC-ICP-MS.

In a preliminary interpretation a correlation of the chemistry of the waters with the regional lithologies can be established with 4 main differentiated chemical signatures. A) Rivers from the Jardine to the Dulhunty, cutting through Middle Jurassic to Early Cretaceous marine quartzose sandstones. B) Rivers from the Wenlock south to the Gilbert, with a strong influence from igneous rocks in the Cape York Batholith. C) Rivers from the Norman to the Leichhardt draining mainly Cretaceous materials with some influence from Proterozoic metamorphics in the Mt Isa Inlier; and D) All the rivers from the Nicholson to the Roper draining areas with abundant Proterozoic metamorphic materials. The 87Sr/86Sr has allowed to calculate some basic Sr isotopes budgets in the area and extrapolate to past lake phases.





THE IGCP464 PROJECT: SCIENTIFIC AND APPLICATIVE RELEVANCE OF CONTINENTAL SHELF STUDIES ON DEVELOPED AND DEVELOPING COUNTRIES

CHIOCCI FRANCESCO LATINO 1, CHIVAS ALLAN ROSS 2

presenter's e-mail: francesco.chiocci@uniroma1.it

1 - Dipartimento di Scienze della Terra, Università "La Sapienza", Italy
2 - School of Geosciences, University of Wollongong, Australia



In the penultimate year of IGCP464 activity, a preliminary summary can be done. Beside the large number of participants (360 from 38 countries), the five international conferences held so far, the main result is the integration of researchers from (economically) developed and from developing countries
Applied aspects emerged so far include research of economic deposits, individuation of faults/slides for risk assessment (including tsunamis), discrimination between human induced and natural trend on the accumulation of pollutants, background study for living resources management, geological mapping, environmental protection.
As some of these can be easily achieved by means of low-technology prospecting (single beam bathymetry, textural analysis), developing countries researchers may fully profit of the dissemination of knowledge and contacts that is the main aim of IGCP programs.
Beside the applied aspects, more "pure" scientific themes emerged during IGCP464 activities are:
PALEOCLIMATE. For the last 20 ka, sedimentary record in well-fed pordeltas may be as complete as deep-sea cores but with a greater stratigraphic expansion. Moreover the vicinity to the continent let the record to be extremely suitable to reconstruct recent climatic changes such as occurrence and paleointensity of floods, droughts, monsoon, etc.
CARBON CYCLE. During last glacial cycle the carbon budget was affected by low latitude carisfication of exposed reefs, removal of highstand pordeltas (where a large amount of biogenic methane is trapped), changes in the productivity of carbonate factories both at low and high-latitudes, pedogenesis of exposed shelves. Some of these processes contrast the general CO2 trend as reconstructed on ice and deep-sea cores, suggesting the shelf acting as dumping factor.
APPLICATION OF SMALL-SCALE STRATIGRAPHIC MODELS. Shelf physical stratigraphy results from the interplay among sedimentary feeding, sea level changes and morphology of the basin. Thus it is an ideal field to apply sequence stratigraphic concepts and to develop model for deposition of sedimentary bodies that are below the resolution of the standard exploration seismics.
ENVIRONMENTAL CHANGES RESPECT TO EARLY HUMANS. Apart from pathways from migration of populations (as for the North Pacific), even rapid transgression in semi-enclosed basin, driven by morphology and glacio-isostasy, seem to have been able to force populations to move and to leave a strng record in the early human heritage.




THE "ATLAS OF SUBMERGED DEPOSITIONAL TERRACES ALONG THE ITALIAN COASTS"


CHIOCCI FRANCESCO LATINO 1, D'ANGELO SILVANA 2, ROMAGNOLI CLAUDIA 3

presenter's e-mail: romagnol@geomin.unibo.it

1 - Dipartimento di Scienze della Terra, Università "La Sapienza", Roma
2 - APAT- Italian Agency for Environment Protection and Technical Services, Department of Soil Protection
3 - Dipartimento di Scienze della Terra e Geologico-Ambientali, Università di Bologna




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 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.






THE ACCUMULATION OF ORGANIC CARBON ON CONTINENTAL SHELVES


CHIVAS ALLAN ROSS 1, MAHIQUES MICHEL 2, BOSKI TOMASZ 3, SHIRODKAR PRABHAKER 4

presenter's e-mail: toschi@uow.edu.au

1 - School of Earth and Environmental Sciences, University of Wollongong, NSW 2522, Australia
2 - Institute of Oceanography, University of Sao Paulo, Brasil
3 - Centro de Investigacao Marinha e Ambiental, Universidade do Algarve, Faro, Portugal
4 - Institute of Oceanography, Dona Paula, Goa, India



One of the goals of IGCP-464 Continental Shelves during the Last Glacial Cycle, has been the investigation of the accumulation and preservation of organic carbon deposited on shelf areas, and its possible later destruction during subaerial exposure.
We here compare recently collected data from key shelf areas in northern Australia, southern Iberia, southern Brazil and near the mouths of the Irrawaddy River, Myanmar (Burma). In each case, organic-carbon contents, C/N ratios and C-13/C-12 ratios of shelf sediments in well dated sediments provide accumulation rates and allow calculation of the proportions of terrestrial- and oceanic-derived carbon. For northern Australia (Gulf of Carpentaria), the sedimentary succession is located in an isolation basin, and oscillates between marine and lacustrine facies, and episodes of subaerial exposure. There is substantial fluvial input in this area, with 24% of the total run-off from the Australian continent entering the Gulf of Carpentaria. Our Myanmar shelf example exhibits an even larger input of terrestrial sediment and carbon.
The sequences showing clear evidence of subaerial exposure (pedogenesis) display sediments with lowered organic-carbon contents, C/N ratios and C-13/C-12 ratios. We explore some of the systematics of this behaviour, including in some cases, the complementary formation of soil carbonates.




CONTINENTAL SHELVES AND MODERN COASTAL ENVIRONMENTS: WHAT CAN WE EXPECT DURING LOW STANDS OF THE OCEAN?


GARCÍA ADRIANA 1, CHIVAS ALLAN ROSS 1, REEVES JESSICA M. 1, HOLT SABINE 1, CENDÓN DIONI 1, VAN DER KAARS SANDER 2

presenter's e-mail: adriana@uow.edu.au

1 - School of Earth and Environmental Sciences, University of Wollongong, NSW 2522, Australia
2 - Centre for Palynology and Palaeoecology, School of Geography and Environmental Science, Monash University, VIC 3800, Australia




Calcareous microfossils such as charophytes, ostracods and foraminifers are indicative of marine/non-marine conditions which permit the distinction of fresh water, inland saline, shallow to deep marine environments, and coastal environments.

Modern tropical environments from Australia have been explored in order to collect extant taxa and use them as analogues.

A detailed sampling around the Gulf of Carpentaria provided macrophytes, ostracods, molluscs, sediments for palynological analyses and water samples. These data will contribute substantially to the palaeoenvironmental reconstruction of the Quaternary history of the Gulf of Carpentaria, including sources of sediments, waters and pollen; biogeography and ecology of taxa present; and the understanding of routes of colonisation.

The assemblages of charophytes, ostracodes and foraminifera of the longest core collected from the Gulf of Carpentaria have been analysed. This core of ~ 15m length comprises two non-marine/marine cycles and has been dated at the base at 130 ka by OSL. Preliminary analyses of stable isotopes (d18O) and d13C) have been performed on foraminifers from both marine and lacustrine facies, and enable further distinction of several facies.






SHALLOW GAS IN SAN SIMON BAY (NW SPAIN)


GARCIA-GIL SOLEDAD 1, IGLESIAS JORGE 1

presenter's e-mail: sgil@uvigo.es

1 - UNIVERSITY OF VIGO


San Simón Bay is a small shallow basin located at the innermost part of the Ria de Vigo. It consists of an N-S elongated embayment of 10 km long and 4 km wide with a maximum depth of 10 m. Rande strait connects this bay with the rest of the Ría de Vigo which has a N45E of main axis. San Simón Bay has a clear tectonic control related to a major N-S fault.
The most significant freshwater input comes from several relatively small rivers that flow into San Simón Bay, which behaves as an estuary. The rest of the ría is under strong oceanic influence (tides and waves) and exhibits a residual circulation in two layers. Winds play an important role in the circulation causing upwelling and downwelling cycles with a strong seasonal pattern which provoke higher marine productivity in summer than during winter.
Interpretation of new high resolution seismic records (2004 survey) has allowed mapping of shallow gas accumulations and gas seeps in San Simón Bay (Ría de Vigo). X-ray photographs and voids of cores are semi-indirect evidences of gassy sediments. Furthermore, bubbles of gas coming out from the seabed of this bay have been recorded for a first time in the rain. Analyses (GC-MS) of bubble samples confirm the presence of methane.
Concerning to the generation of gas in San Simón Bay, it is suggested that there are three different sources of biogenic gas: (1) microbial methane generation from the organic matter accumulated in the subtidal sediments, (2) drainage of an ancient peat horizon located under the present intertidal sediments and (3) fluids migration throughout faults.
It is interpreted that the present location of the peat horizon and the cemented beach facies correspond to variations in the relative sea-level. These variations in San Simon Bay are due to the combination of tectonic and the global rise of sea level occurred after the last glacial episode.







  CONTINENTAL SHELF EVOLUTION DURING THE LAST GLACIAL CYCLE - INFLUENCE ON HUMAN CULTURE

HETHERINGTON RENÉE 1

presenter's e-mail: reneehet@uvic.ca

1 - University of Victoria


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; China) - 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 Italy (Enzo et al. 2001), South Africa (Franceschini & Compton 2001), France, USA, and Canada (Faure et al. 2002), Poland (Kramarska et al. 2002, 2003; Uscinowicz & Miotk-Szpiganowicz 2001; Uscinowicz et al. 2002, 2003; Zachowicz 2001, Zachowicz et al. 2003), Korea (Park & Kim 2003), and Australia (Garcia et al. 2001, 2002, 2003; Holt et al. 2003; Reeves et al. 2003; Van Der Kaars et al. 2003) to suggest links and influences between LGC induced changes and human occupation, expansion, and regional economic and cultural development. Researchers from Argentina (Cavallotti et al. 2004; Nami 2001; Torra 2001; Violante 2001, 2002; Aguirre & Violante 2002; Violante & Parker 2004), Brazil (Lima, de Souza, de Mahiques 2002, de Mahiques et al. 2003), Russia (Patyk-Kara 2003), and Canada (Hetherington et al. 2001, 2002, 2003, 2004; Josenhans 2001; Fedje 2003; Hetherington & Weaver 2003; Al-Suwaidi et al. 2003; Fladmark 2003; Jackson 2003; Ward et al. 2003; Wilson et al. 2003), are comparing their findings in an effort to provide insights into early human habitation and peopling of the Americas. IGCP 464 researchers from France, Belgium, 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.




POSTGLACIAL EVOLUTION OF THE WESTERN ARCTIC SHELF ENVIRONMENTS

IVANOVA ELENA V. 1

presenter's e-mail: eivanova@geo.sio.rssi.ru

1 - Shirshov Institute of Oceanology RAS




The high-resolution study of benthic foraminiferal assemblages in several cores from shelf depressions suggests different paleoenvironmental evolution of the glaciated Barents Sea shelf and the non-glaciated eastern Kara Sea shelf during the postglacial time. Lithostratigrafic evidence confirmed by AMS 14C datings show that the recovered time span is about 17-18 cal ka in the north-eastern Barents Sea and about 12 cal ka in the eastern Kara Sea. Generally rare foraminiferal occurrence in sediments of the Barents Sea ice sheet deglaciation points to unfavorable benthic habitat. A proximal glaciomarine environment characteristic for the early deglaciation, with almost permanent sea-ice cover throughout the newly formed marine basin, and abundant fine suspended matter delivery from melting glaciers hinted biological productivity, thus restricting the food supply for benthic communities. During the main deglaciation phase, when the ice sheet retreated above sea level, foraminiferal assemblages became more diverse, and some increase in abundance occurred at rather short intervals of enhanced bottom-water ventilation that resulted from oxygen supply by downslope brine-induced nepheloid flows. The warm and saline subsurface Atlantic water inflow into the Barents Sea via troughs and an appearance of short ice-free seasons promoted plankton bloom. In both seas, the benthic foraminiferal assemblages demonstrate high values of opportunistic species which tolerated the stressed environments. However, a significant percentage of brackish species is found in Preboreal sediments from the Kara Sea due to river run-off influence. The most dramatic change in the Barents Sea environments is fixed at Preborial to Holocene boundary when normal marine conditions established throughout the basin resulting in a strong increase in bioproductivity. The evolution of periglacial eastern Kara Sea was more gradual with an increase of marine elements percentage in foraminiferal assemblages during the Early Holocene sea-level rise, until ~ 7 cal ka. In both basins, variations in Holocene assemblages respond to climate driven changes in sea-ice conditions, food supply, bottom-water ventilation, and other paleoceanographic parameters. The variability also reflects oscillations in the Atlantic water input into the basins and in river run-off, the latter being especially pronounced in the Kara Sea affected by an increased Siberian rivers discharge during the Middle Holocene.






GLOBAL CHANGE AND SUBMARINE GROUNDWATER DISCHARGE


KONTAR EVGENY 1

presenter's e-mail: ekontar@ocean.fsu.edu

1 - P.P. Shirshov Institute of Oceanology, Russian Academy of Sciences



Global Change can refer to a number of processes. It certainly means (a) that a phenomenon is observed to be changing in many different parts of the world; and (b) that a process is linked to some large-scale phenomenon like climate. Submarine groundwater discharge (SGD) and its associated nutrient contributions to the coastal zone are closely related to both definitions. While SGD has been estimated to be a small fraction of the global freshwater flux, such inputs are estimated to be much more important in semi-enclosed and inland seas. Recent estimates, for example, attribute 50% of the total freshwater flow into some inland seas to groundwater inputs! (i.e., Aral Sea, INTAS projects 1003 & 1014). In addition, since nutrient concentrations are often much higher in groundwater than river water; net fluxes can be higher even when the flow is lower. We hypothesize that many of the water quality and associated problems effecting coastal zone environments around the world today may be related to past and on-going contamination of terrestrial groundwater because those groundwater are now encroaching upon the coastal zone. For example, chronic inputs of fertilizers and sewage on land over the past several decades has resulted in higher groundwater nitrogen concentrations which, because of slow yet persistent discharge along the shorelines, eventually results in coastal marine eutrophication. Such inputs may thus be responsible for the increased occurrences of coastal hypoxia, nuisance algal blooms, and all the associated consequences, which have direct human dimensions. We thus suggest that some of the more important "Changes in Coastal Zones and Inland Waters," a research priority, may be influenced by groundwater discharge, an invisible and overlooked pathway between land and sea. On July 20, 2001, during the 6th Scientific Assembly of the IAHS in Maastricht, the Netherlands, we had a productive meeting, discussing and organizing the IUGG Inter-Association Commission "Groundwater-Seawater Interactions" (CGSI), with representatives from the International Association for the Physical Sciences of the Ocean (IAPSO) and the International Association of Hydrological Sciences (IAHS), to help to facilitate and coordinate research in this highly interdisciplinary subject. During the IUGG Congress in Sapporo, Japan (July 2003) the CGSI was reorganized to have more than 130 members. Study of the direct discharge of groundwater into the ocean is an emerging science.








RAPID TRANSGRESSIONS INTO SEMI-ENCLOSED BASINS SINCE THE LAST GLACIAL MAXIMUM

LERICOLAIS GILLES 1, CHIVAS ALLAN ROSS 2, CHIOCCI FRANCESCO LATINO 3, USCINOWICZ SZYMON 4, BO JENSEN JORN 5, LEMKE WOLFRAM 6, VIOLANTE ROBERTO ANTONIO 7

presenter's e-mail: Gilles.lericolais@ifremer.fr

1 - IFREMER France
2 - School of Geosciences, University of Wollongong, NSW 2522, Australia
3 - Dipartimento Scienze della terra, Università di Roma "La Sapienza" P.le Aldo Moro 5, 00185, Roma, Italy
4 - Polish Geological Institute, Branch of Marine Geology Ko_cierska 5 st., 80-328 Gdansk, Poland
5 - Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark
6 - Institution: Baltic Sea Research Institute Street: Seestr. 15 Postal code: D-18119 Rostock-Warnemünde German
7 - Argentina Hydrographyc Office Av. Montes De Oca 2124, (C1270ABV) Buenos Aires, Argentina


One of the objectives of the IGCP 464 project is to compare and contrast the global development of continental shelves, particularly with respect to the Last Glacial Maximum (LGM) with a real will to complement with a high-temporal-resolution the plaeoclimate variability since the LGM. Semi-enclosed basin margins represent good candidates for preservation in their sedimentary records of abrupt changes climatically or tectonically related, often unrecorded or obliterated by global modifications. Abrupt Sea-level rises have been recorded in many different semi-enclosed basins around the world. The link to rapid transgressions is easy to do, even if the mechanisms are completely different. Large and rapid releases of freshwater from ice sheets since the LGM to sensitive areas may also arise from several mechanisms. The last deglaciation provides the level of preservation necessary to identify specific mechanisms of ice-sheet forcing and attendant climatic responses. The presentation will summarise results presented during a special session of the project which concern focussed on rapid transgressions into semi-enclosed basins since the LGM. Different examples will be discussed as the Carpentaria Basin, in northern Australia, Argentinean semi-enclosed basins, the Baltic Sea and the Black Sea. The Carpentaria Basin, in northern Australia is at low latitude, and far from the direct influence of ice sheets. Here, the critical sill depth (currently -53m wrto sea level) defines changes between marine and lacustrine sedimentation, and provides independent evidence of global sea-level changes. Evolution of the Argentinean basins was mainly conditioned by the post-LGM relative sea-level rise as well as by littoral dynamic factors that fluctuated following the succession of climatic and eustatic events. The Baltic Sea has been covered during the LGM by an ice sheet up to 3km thick, and the subsequent isostatic re-adjustment after deglaciation far outpaced the global postglacial sea-level rise. The Black Sea, a semi-enclosed basin which connections with the global ocean are restricted by the Bosphorus, Dardanelles and Gibraltar Straits, was directly supplied with the melt water of the first deglaciation event by major Eastern Europe rivers. The Black Sea has encountered complex water level fluctuations with high lake levels occurring during wet and melting period after the LGM and low lake levels occurring during drier conditions as the Younger Dryas was for this region





LATE QUATERNARY EVOLUTION OF THE INNER SHELF OFF SÃO SEBASTIÃO, SOUTHEASTERN BRAZIL: IMPLICATIONS FOR THE BRAZILIAN SEA-LEVEL CURVE


DE MAHIQUES MICHEL 1, KLEIN DANIEL ANDREAS 1, RODRIGUES MARCELO 1, FURTADO VALDENIR VERONESE 1

presenter's e-mail: mahiques@usp.br

1 - Institute of Oceanography - University of São Paulo




The Quaternary evolution of the Brazilian coast has been the object of recent evaluation mainly concerning the Holocene sea-level curve. Actually most of the data on Brazilian coastal evolution relate to the Late Holocene; very little information is available regarding the position of the sea-level prior to 7,500 years B.P. and a considerable amount of information about the position of the sea-level has been obtained by association from other areas of the world. This is particularly critical for the Isotope Stage 3, for which no reliable information about the maximum sea-level had yet been obtained.
In this study we have used three sedimentary cores as well as a beach-rock sampled in the region off São Sebastião, on the Souttheastern Brazilian shelf, to interpret the evolution of the area during the Late Quaternary giving special attention to the sea-level change curve. The cores were analysed for coarse fraction, calcium carbonate, organic carbon, total nitrogen and sulphur content and carbon isotope values. Calcium carbonate samples (foraminifer and beach rock) were used for radiocarbon datings. For samples younger than 20,000 years the ages were calibrated using the SW Atlantic reservoir correction for marine samples.
The base of one of the cores (TSSB-1), at a depth equivalent to 7 meters below the present sea-level, consisting of a dark olive gray mud with sparse carbonate fragments and containing the foraminifer Elphidium sp. and the ostracod Cyprideis, has been dated at 39,500±750 years B.P., corresponding to Isotope Stage 3. Compositional and isotopic values allow this sequence to be recognised as characteristic of a mixohaline environment. Sedimentation of this sequence continued up to ca. 10,000 years B.P. through a progressive change of the environment to fresh water conditions.
The Holocene marine ingression in the area is registered after 8,250 years B.P. when a beach rock, located 13 meters below the present sea-level was deposited. In the region of the core samplings marine conditions were established only after ca. 6,000 years B.P. as revealed by compositional and isotopic data.
Our results have enabled us to make good the lack of information as to the position of the sea-level in a relatively tectonically stable area of the SW Atlantic Ocean. They also represent the first sure indication of the maximum sea level on the Brazilian coast during Isotope Stage 3.





LOWSTAND DEPOSITIONAL TERRACES SURROUNDING WESTERN PONTINE ARCHIPELAGO (TYRRHENIAN SEA)


MARTORELLI ELEONORA 1, CHIOCCI FRANCESCO LATINO 1, PAZZINI ALFREDO 1

presenter's e-mail: eleonora.martorelli@uniroma1.it

1 - Dipartimento di Scienze della Terra, Università degli Studi di Roma "La Sapienza"



Lowstand depositional terraces (LDTs) are prograding sandy wedges, characterized by limited thickness (some tens of meters), with internal foreset dipping 5°-9° (Chiocci and Orlando, 1996). They develop parallel to the isobaths close to the shelf break and have been always recognized on steep shelves, mainly located around volcanic islands or in tectonic settings.
In volcanic island settings, LDTs represent the main, sometimes the exclusive, depositional bodies occurring over the volcanic bedrock on the shelf.
The detailed study of the LDTs give indications on 1) the depositional/climatic condition during glacial time 2) the vertical movement of the continental margin, 3) the occurrence of present or sub-present erosional conditions of canyon heads.
A detailed description of LDTs recognized in Western Pontine Archipelago has been done by Chiocci and Orlando (1996). For geological mapping purposes, new high resolution seismic data (Sparker and Chirp) have been collected and a re-interpretation of existing data have been performed. As a result a detailed map of distribution and thickness of the LDTs is now available.
In particular a LDT develops, almost continuously, around Palmarola, Ponza, Zannone islands and Botte Rocks, above an erosional unconformity clearly depicted in almost all the area.
The unconformity truncates a substratum mainly made up of volcanic rocks. However, in some areas (i.e. northern part of the archipelago and Botte Rock), below the unconformity the presence of deeper reflectors suggest the occurrence of older lowstand depositional terraces. These areas are thus believed to represent subsiding zone where older units were preserved from erosion by lowering them below the maximum depth reached by Upper Pleistocene sea level lowstands.
Last LDT (thought to be formed during last glacial maximum) reaches the maximum thickness close to the shelf break. Main depocenters are located offshore the northern part of Ponza-Zannone saddle (with thickness of about 50 m) and S-SE of Ponza Island (with thickness of about 40 m).
In some areas LDT seems to have a quite complex relation with instability processes as the terrace edge may be controlled in part by slope gradient but the post-depositional erosive activity of gullies and canyon heads may shallow it as well.

CHIOCCI F.L. and ORLANDO L. (1996). Lowstand terraces on Tyrrhenian Sea steep continental slopes. Marine Geology, 134, 127-143.






 FACIES SYSTEM OF THE BARENTS SEA SINCE THE LAST GLACIAL MAXIMUM TO RECENT


MURDMAA IVAR 1

presenter's e-mail: murdma@sio.rssi.ru

1 - P.P.Shirshov Institute of Oceanology




Late Weichselian continental moraine facies unconformably overlie the rough basement topography of the Barents Sea shelf. In shelf depressions, a blanket of proximal glaciomarine facies was deposited above the moraine during the initial deglaciation phase (ca. 16-13 ka BP) when the Barents Sea ice sheet detached from the bottom resulting in iceberg calving, and seawater first penetrated into deep troughs. The facies comprise marine moraine, diamicton composed of iceberg rafted debris (IRD) and glacier meltwater load, as well as debris flow deposits. Although very rare, but persistent foraminiferal fauna and saline pore water are evidence of a marine environment. Overlying distal glaciomarine facies represented by various laminated flow deposits are formed during the main deglaciation phase (ca. 13-10 ka BP). Absence of IRD in laminated fine-grained sediments suggests glacier front retreat above the sea level. Glacier meltwater discharge became the main sediment source. Appearance of oxidized sediments and ferruginous hardgrounds indicates ventilation of the bottom water possibly related to enhanced brines activity. The latter also induced gravity flows and transferred meltwater isotope signals from the sea surface to the bottom where they are fixed in benthic foraminiferal tests. Onset of the Holocene marine environment led to a dramatic increase in such indicators of enhanced biological productivity as organic carbon content, foraminiferal abundance and species diversity, bioturbation, and microbial sulfate reduction. Holocene sediments are represented by clay or silty clay of depression facies contrasting with wave- and current-transported sand on near-shore shoals and with thin discontinuous veneer of residual coarse-grained bank summit facies enriched in IRD and characterized by locally rich benthic fauna. Lateral near-bottom suspended matter transport by waves, bottom currents, and low-density nepheloid flows mainly controls the facies diversity and variations in thickness of the Holocene sediment cover. Maximum thicknesses (up to 20 m or more) are fixed in fjords. Holocene sections up to 3-5 m thick occur in local depressions, where they show high organic matter content and relatively rich benthic foraminiferal fauna. Facies of wide deep lowlands and gentle slopes are characterized by thin (<1 m) Holocene sediments with low organic matter content and absence of microfossils, possibly owing to their dissolution in conditions of slow sedimentation.




ARE EMERGED SHELVES A SOURCE FOR LOESS?


SMYKATZ-KLOSS BETTINA 1, ZOELLER LUDWIG R. 2, ANTOINE PIERRE 3

presenter's e-mail: ludwig.zoeller@uni-bayreuth.de

1 - University of Bonn, Geography Dept.
2 - University of Bayreuth, Chair for Geomorphology
3 - UMR CNRS 8591 - Laboratoire de Géographie Physique, Meudon




Textbooks of geology and geomorphology mostly regard glacial outwash plains as the main source of loess. The thickest loess units of the world are, however, too far remote from vast glacial outwash plains. Therefore, other possible sources have been suggested in the literature. Shelves emerged due to glacio-eustatic sea-level drop have seldom been discussed as source areas. In many parts of the world shelves are covered by unconsolidated fine-grained detrital sediments which can easily be blown out. The English Channel, e.g., was identified as a significant source area of loess in north-western France by heavy mineral analysis and geomorphologic observations. For loess areas further remote from the coast-line heavy minerals may, however, fail to prove a loess contribution from emerged shelves.

We compared last glacial loess-paleosol sequences from the Picardie historical landscape (NW France) and the rolling land "Pleiser Huegelland" east of the city of Bonn, Germany, situated at the decline of the Rhenish Massif towards the Lower Rhine Embayment. Geochemical, isotopic and mineralogical methods (including microprobe SEM) as well as microscopic investigation of microfossils have been applied.

We found evidence (trace minerals, microfossils) for littoral or shallow marine sediments delivering detrital grains to loess accumulations in areas under investigation, the Picardie (as expected) and the surroundings of Bonn. For the latter, a (dominant) local source (primarily periglacial fluvial terraces of the southern Lower Rhine Embayment) is distinguished from a remote source including emerged littoral or shallow marine sedimentary environments. The far-travelled component cannot be quantified at this stage of our studies, but its qualitative proof may trigger further research into the role of emerged shelves as a source of atmospheric dust. Sea-level change, with regard to this perspective, would not only appear as a result of climate change, but also give rise to a positive feed-back to climate change due to the effects of dust on atmospheric radiation parameters.






PALAEOENVIRONMENTAL EVOLUTION OF THE NORTHERN ARGENTINA CONTINENTAL SHELF DURING THE POST-LGM TRANSGRESSION

VIOLANTE ROBERTO ANTONIO 1

presenter's e-mail: violante@hidro.gov.ar

1 - argentina hydrographic service




Littoral and shallow-marine deposits accumulated during the marine cycle that followed the Last Glacial Maximum constitute the uppermost stratigraphical unit in the northern part of the Argentina continental shelf and adjacent coastal plains. This unit is considered, from the sequence stratigraphy viewpoint, as a depositional sequence that includes two system tracts: transgressive and high-stand. The probable existence of a low-level system tract on the outer margin of the shelf was still not confirmed. System tracts are formed by a succession of depositional systems that represent sedimentary environments such as barriers, beach ridges, coastal lagoons, marshes and estuaries. The study allowed to interpret the sea-level fluctuations and palaeoenvironmental evolution occurred in the region over the last 18.000 to 20.000 years.






SUB-AERIAL EXPOSURE OF CONTINENTAL SHELVES DURING GLACIAL PERIODS AND THE TERMINATION OF ICE AGES


YIM WYSS WAI-SHU 1

presenter's e-mail: wwsyim@hku.hk

1 - Department of Earth Sciences, The University of Hong Kong, Hong Kong SAR, China



The sub-aerial exposure of continental shelves during glacial periods is suggested to provide a mechanism for the production of atmospheric carbon dioxide significant enough to cause the abrupt termination of ice ages. The processes operating leading to such changes include:
(1) Acid-sulphate soil development in exposed siliciclastic shelves.
(2) Karstification of exposed coral reefs.
(3) Karstification of exposed carbonate platforms.
The massive release of carbon dioxide provides the triggering mechanism needed for switching the earth from a full glacial mode back into an interglacial mode (Yim et al., 2002). This is supported by the dramatic increase in carbon dioxide and methane content in the Vostok ice core following the glacial periods of MIS 2, 6, 8, 10 and 12 (Petit et al., 1999).
References -
Petit, J.R., Jouzel, J., Raynauld, D., Barkov, N.I., Barnola, J.-M., Basile, I., Bender, M., Chappellaz, J., Davis, M., Delaygue, G., Delmotte, M., Kotlyakov, V.M., Legrand, M., Lipenkov, V.Y., Lorius, C., Pepin, L., Ritz, C., Saltzman, E., Stievenard, M. (1999). Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica. Nature 399: 429-436.
Yim, W.W.-S., Chan, L.S., Hseih, M., Philp, R.P., Ridley Thomas, W.N. (2002). Carbon flux during the last interglacial cycle in the inner continental shelf of the South China Sea off Hong Kong. Global and Planetary Change 33: 29-45.