Special session within Geological Association of Canada Annual Conference
EARLY HUMANS AND THE EVOLVING NORTHEASTERN PACIFIC MARGIN
Organised by Renée Hetherington (Geological Survey of Canada) and Vaughn Barrie (Geological Survey of Canada).


The session focused on the paleoenvironmental and paleogeographical evolution of the northeastern Pacific margin, particularly leading into and subsequent to the Last Glacial Maximum. This late Pleistocene evolution is a record of how systems have responded to change in the past, how they may respond to anticipated future climate change, and the impacts of change on the coastal region's suitability for early human habitation. The session was timely because any removal of the moratorium on oil exploration in the QCI region will revive interest in land-use issues including land-claims and the ecological, economic, and environmental impacts of resource exploitation, and Canada's coastlines, her people, and infrastructure are vulnerable to the impacts of anticipated climate change. Oral and poster presentations have been given.


PROGRAM
Port Eliza Cave: The sedimentology, stratigraphy and palaeontology of cave deposits and their implications for a human coastal migration route
Al-Suwaidi, M., Ward, Wilson, Enkin, Nagorsen and Wigen
None if by Land, Two if by Sea: Assessing the relative feasibility of Late Pleistocerne coastal vs. interior migration routes for early native Americans moving south of Beringia
Fladmark, K.R., Simon Fraser University
Variations in timing and extent of Late Quaternary sea-level change and glacially-induced crustal displacement along the Pacific margin of Canada: Potential role of tectonics at the plate boundary
Hetherington and Barrie
The environment of late Pleistocene - early Holocene Queen Charlotte Islands archipelago, Western Canada and implications for early humans
Hetherington, R., Barrie, Reid and MacLeod,
Lost Landscapes: A paleogeographic reconstruction of the Queen Charlotte Islands archipelago, western Canada 8.7 to 14.2 ka B
 Hetherington, Barrie, Reid, MacLeod and Kung
The timing of ice-free corridors through the Cordillera and adjacent interior plains--open and shut cases
Jackson
Port Eliza cave: North American west coast interstadial environment and implications for human migrations
 Ward, Wilson, Nagorsen, Wigen and Al-Suwaidi
Early postglacial fossil bison from Vancouver Island, British Columbia, and Orcas Island, Washington: morphology, taxonomy and paleoecological setting
Wilson, Hebda, and Keddie

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Port Eliza Cave: The sedimentology, stratigraphy and palaeontology of cave deposits and their implications for a human coastal migration route

Al-Suwaidi, M., malsuwaa@sfu.ca,
Ward, B.C., Earth Sciences Department, Simon Fraser University
Wilson, M.C., Department of Geology, Douglas College, New West Minster
Enkin, R.J., Geological Survey of Canada – Pacific, 9860 West Saanich Road, POB 6000, Sidney, BC V8L 4B2,
Nagorsen, D.W., Royal British Columbia Museum
Wigen, R.J., Department of Anthropology, University of Victoria


Port Eliza Cave, on the West Coast of Vancouver Island is 85 metres above m.s.l. and records sediments and fauna that reconstruct Late Wisconsinan glacial advances and palaeoclimate. The exposed sediments in the cave and those recorded in a 3 metre excavation will be described in detail. Three units were identified in the excavation, Unit 1is a basal diamicton, Unit 2 is a sequence of laminated clays and Unit 3 consists of oxidised clay capped by stalagmites. The basal diamicton (Unit 1) represents the palaeo-floor of the cave. It contains abundant bone material, clasts varying in lithology, size and shape, and fragments of dripstone. Further work on the clast shapes as well as SEM analysis will be used to determine the genesis of this diamicton. Unit 2 lies unconformably above unit 1. It consists of a succession of laminated to finely bedded clay with millimetre scale soft sediment deformation structures and strong remnant magnetisation. The clays were deposited in glaciolacustrine environment formed when the cave mouth was blocked by ice. The glacial origin and clay provenance of the rhythmites will be determined through thin section work, clay mineralogy and SEM analysis on the grains. Unit 2 contains abundant centimetre scale normal faults, which may be related to isostatic rebound. Capping the sequence is Unit 3, a layer of oxidised clays containing dripstone and charcoal fragments, and the disaggregated remains of a mountain goat. Sporadic stalagmites cover the present floor.
Dates from bones in the basal diamicton (unit 1) of 18.0-16.3ka provide a maximum age for ice presence in the area. A diverse vertebrate fauna of marmot, vole, marten, cervid and various species of birds and fish were recovered from Unit 1. The fish species indicate that relative sea level was close to the cave and that salmon runs were likely present; eustatic models indicate a m.s.l. of 125 metres below present levels. These data suggests that during the deposition of Unit 1 there was significant isostatic depression. The terrestrial vertebrate fauna is consistent with a cool, open parkland environment with maximum summer temperatures cooler than present; these conditions lasted until at least 16ka. The mountain goat will be 14C dated to provide chronological control on deglaciation. With a diverse fauna and favourable climate, humans could have survived locally on a mixed marine-terrestrial diet, This confirms the viability of the coastal migration hypothesis.




None if by Land, Two if by Sea: Assessing the relative feasibility of Late Pleistocerne coastal vs. interior migration routes for early native Americans moving south of Beringia

Fladmark, K.R., Simon Fraser University

This paper will review paleoenvironmental data concerning the relative feasibility of the two main routes used to explain how the first North Americans moved south of Beringia during and just after the maximum of the Late Wisconsinan Glaciation. They are: (1) An “interior ice-free corridor”, lying between Laurentide and Cordilleran/Montane ice masses along the eastern flanks of the Rocky Mountains and (2), a “coastal route”, or chain of small ice-free land areas around the outer northern Pacific margin of the continent.
In summary, there now is considerable evidence that glacial coalescence occurred along at least the central and southern part of the “corridor” during the Late Wisconsinan maximum, with that route first becoming viable for major land mammals only after 11,500-11,000 b.p. In addition, the few early dated archaeological sites currently known in that mid-continental region show a south-to-north age gradient in the 11,500 to 10,500 b.p. time range. That implies that people had already somehow penetrated south of the glaciated areas before that ice began to recede. The only way that could have been accomplished would have been via the so-called “coastal route”. It would have involved boat-using people following a series of islands and headlands along the outer Pacific coast of Alaska and British Columbia which become ice-free and biotically viable by at least 13-15,000 years ago. Those areas also would have been significantly enlarged by sea-levels ca. 100-200 m. lower than present.
Unfortunately, there are few historic parallels for the kinds of “periglacial marine” cultural adaptations that would have been required by early people using such coastal refugia. We do know that modern tour groups regularly paddle kayaks close to the large glaciers which currently reach sea-level in Southeastern Alaska. Thus, presumably, such movements would have been possible for early natives equipped with skin covered boats. We also know that the ethnographic Tlingit occupants of that area interacted successfully with the extensive local Little Ice-Age glacial advances of the 18th and 19th centuries A.D. Thus, some of their stories tell of moving to the outer coast as glaciers advanced, then returning back into the fjords as the ice retreated. Other Tlingit traditions tell of adventurous people paddling canoes through tunnels in glaciers damming rivers, while others walked across those same ice-tongues. Such stories might be seen as historic analogues for human responses to Pleistocene coastal conditions and as indications that human life and movement was feasible in at least some Late Wisconsinan marine “ice-frontal” locations.







Variations in timing and extent of Late Quaternary sea-level change and glacially-induced crustal displacement along the Pacific margin of Canada: Potential role of tectonics at the plate boundary

Hetherington, R. and Barrie, J.V., Geological Survey of Canada

Following the Last Glacial Maximum (LGM), complex sea-level change along the Pacific margin of Canada reflects changing eustatic sea level, deglaciation, a relatively thin, flexible lithosphere, and tectonics on the Pacific margin of Canada. Variations in timing and extent of relative sea level, crustal uplift and depression, and crustal tilting is observed between the Queen Charlotte Basin (QSB) to the north, and the Georgia Basin (GB) to the south, elucidating contrasting cross-shelf crustal response. Relative sea levels reached +50 to +200 m in the GB during initial deglaciation, falling to ~0 at Fraser Lowland and ~ -50 m at Victoria after 10.0 ka BP. Whereas in Queen Charlotte Sound and Hecate Strait sea level exceeded 120 m below present between 13 ka BP and 9.0 ka BP. Monotonic sea-level curves and crustal displacement curves for the GB and northern British Columbia (BC) mainland indicate that ice retreated from the northern BC mainland by 10 ka BP and in the GB by 12.0 ka BP. A reduced ice load persisted in or proximal to the Fraser Lowland, on southern BC mainland, until at least 10.0 ka BP. A forebulge developed in QCB from 13.2 until after 9.7 ka BP, whereas there is no evidence at present of a forebulge developing in the GB.
Unexplained subsidence with an amplitude averaging ~50 m is evident in the northern and western regions of the QCB during the early- and mid-Holocene subsequent to ice retreat. It is difficult to account for observed crustal displacement in QCB using current postglacial rebound models. Mantle material may have flowed from this region to the northeast of the British Columbia mainland and southeastern Alaska where ice retreated earlier than in southwestern British Columbia. However, even if this were the case, it is difficult to explain the magnitude of subsidence over this short interval. We propose that a warm, relatively thin lithosphere combined with local tectonics may have influenced crustal displacement, particularly the decoupling of the North American plate at the proximally located Queen Charlotte (QC) Fault. This fault, which decouples the continental shelf along the shelfbreak, may have allowed the QCB shelf to behave in a “hinge-like” manner to glacial unloading. This would explain large magnitude crustal tilting (2.1 m/km) observed adjacent to the QC Fault. The 50 m of depression observed in the QCB during the Holocene suggests the western edge of the North America Plate “bounced down” below present elevation, producing a repeat wave response to ice loading and unloading.






The environment of late Pleistocene - early Holocene Queen Charlotte Islands archipelago, Western Canada and implications for early humans

Hetherington, R., Natural Resources Canada, Geological Survey of Canada
Barrie, J.V., Natural Resources Canada, Geological Survey of Canada
Reid, R.G.B., Department of Biology, University of Victoria
MacLeod, R., Natural Resources Canada, Geological Survey of Canada

The Americas’ first humans are thought to have migrated down the west coast of North American subsequent to the last glacial maximum (LGM). However, no evidence dating prior to 10,300 BP has been found along the BC - Alaskan coast. Is this a consequence of a lack of early archaeological sites, or is it because the coastline has shifted?
Paleogeographical and paleoenvironmental reconstructions identify a complex glacio-isostatic and sea-level history along Canada’s northeast Pacific margin during and subsequent to the LGM. Glacial ice at least 500 m thicker than present water depth began retreating from Dixon Entrance after 15,000 and prior to 12,600 BP. Prior to this time navigation along northern QCI and Dixon Entrance was precluded due to the presence of ice; early migrants would have skirted outer QCI or traveled over land (ice). Lowered eustatic sea level combined with crustal uplift permitted terrestrial conditions to develop on two emergent coastal plains. The northern plain was present from ~14,000 until at least 9,100 BP. The southern plain remained until as late at 7,800 BP. Northern Hecate Strait closed by ~11,750 BP creating a landbridge that connected the BC mainland and the QCI, facilitating faunal, floral, and potential land-based human migration.
By at least 13,200 BP productive estuaries, quiet water bays, and deltas were home to many edible intertidal molluscs, indicating the region had a suitable climate not only for them, but for human inhabitants as well. Reduced coastal zone productivity during a “Younger Dryas” interval between ~10,900 and 10,200 BP potentially altered migration and habitat conditions, forcing early peoples to migrate greater distances to collect coastal resources and/or increase their reliance on land-based resources. By at least 9,000 BP the currently turbulent outer coast region was highly productive and by ~8,900 BP edible molluscan biomass densities were within viable commercial harvest levels on southern Moresby Island.
Open ocean conditions and a suitable environment existed for early human occupation of the northeast Pacific margin by at least 13,200 BP. Occupation would have likely been limited to resource-rich coastal zones. Numerous resource-rich coastal zones and estuaries in Hecate Strait and QC Sound have been cored and dated and although these would make excellent potential early archaeological site locations, they are now drowned and difficult to access. Paleocoastlines obtained from paleogeographic reconstructions overlaid on present-day subaerial topography outline the location of potential early archaeological sites that are accessible. Paleocoastlines of particular archaeological interest lie along the west coast of QCI, where early peoples likely first traveled and westernmost sites along the BC mainland.



Lost Landscapes: A paleogeographic reconstruction of the Queen Charlotte Islands archipelago, western Canada 8.7 to 14.2 ka BP

Hetherington, R, Geological Survey of Canada,
Barrie, J.V.1, Reid, R.G.B., Department of Biology, University of Victori
MacLeod, R.1 and Kung, R.Geological Survey of Canada,

The Americas’ first humans are thought to have migrated down the west coast of North America subsequent to the last glacial maximum (LGM). However no evidence dating prior to 10.3 ka BP has yet been found along the British Columbia (BC) mainland - Alaska coast. Is this a consequence of a lack of early archaeological sites, or is it because coastlines have shifted making site identification difficult.
A series of paleogeographic maps and isostatic crustal displacement maps chart the sequence of evolving landscapes and display temporal changes in the magnitudes and extent of crustal flexure that resulted in a lack of uniformity in relative sea levels across the Queen Charlotte Islands (QCI) region. These maps were derived from the integration of the following data sets: habitat characteristics and age of molluscs collected from submarine cores, submarine grab samples, and raised beaches; sedimentological analysis of cores and raised beaches; seismic reflection and sidescan sonar records; and bathymetry.
An estimated 690 m of glacial ice began retreating from Dixon Entrance after 14.5 ka BP and prior to 12.6 ka BP, permitting over 100 m of uplift in northern Hecate Strait. A forebulge persisted in Hecate Strait and QC Sound from 13.2 until after 9.7 ka BP implying fixed glacial ice on the BC mainland until ~10 ka BP. Paleogeographic reconstructions show two emergent ice-free terrains extending across the continental shelf (100-150 km) that could have been inhabited by plants and animals, including coastally migrating early humans. Ice-free terrain, present by 13.7 ka BP, were intermittently connected via a landbridge to the Queen Charlotte Islands and the BC mainland. Edible molluscan resources were available from at least 13.2 ka BP. Malacological evidence supports paleoceanographic and palynological studies of a late-glacial Younger Dryas cooling event around the southern limits of Hecate Strait and QC Sound, potentially requiring early peoples to migrate greater distances to collect coastal resources and/or increase their reliance on land-based resources. Early coastlines that have not been drowned and which may harbour early archaeological sites are identified along the western QCI and the BC mainland.







The timing of ice-free corridors through the Cordillera and adjacent interior plains--open and shut cases

Jackson, L.E. Jr., Geological Survey of Canada, Terrain Sciences Division

Late Pleistocene glacial chronology constrains the intervals during which the first peoples of the Americas could have migrated southward through the Canadian Cordillera and the adjacent Interior Plains. Although full coalescence of the Laurentide Ice Sheet and Rocky Mountain glaciers lasted less than about 6 ka, evidence suggests that ice may have blocked one possible corridor east of the Mackenzie Mountains from 30 ka until after 11 ka: a route previously thought to be the northern margin of the ‘ice-free corridor’. However, the Cordilleran Ice Sheet maximum did not occur until ca. 20 ka. Paleoenvironmental data indicate that many areas of the Cordilleran interior were habitable immediately prior to this time. Consequently, people could have migrated through the Cordillera from north to south along plateaux or major valley systems. This Cordilleran ice-free corridor is postulated as a route south while ice sheets barred routes east of the Cordillera and fiord glaciers and ice shelves may have barred passage along the west coast.






Port Eliza cave: North American west coast interstadial environment and implications for human migrations

Ward, B.C., Department of Earth Sciences, Simon Fraser University
Wilson, M.C., Department of Geology, Douglas College
Nagorsen, D.W., Mammalia Biological Consulting,
Wigen, R.J., Department of Anthropology, University of Victoria
Al-Suwaidi, M., Department of Earth Sciences, Simon Fraser University

The timing of late Pleistocene glacial advance, retreat, relative sea level and environmental viability between 25 and 12.5 ka (14C yrs BP) remain a key issue in the feasibility of a coastal migration route for the first North Americans. Here we present stratigraphic, radiometric and faunal data for Port Eliza cave, a raised sea cave, on the west coast of Vancouver Island, British Columbia. A 2.5 m deep excavation near the back of the cave revealed three units: (1) > 50 cm of relatively massive, silty-sandy diamicton that contains bones, striated clasts and small fragments of dripstone; (2) 2 m of laminated clay; and (3) 20 to 30 cm of oxidized, weakly laminated to massive silts and clays containing dripstone fragments, rare bones and charcoal, capped by stalagmites. The genesis of unit 1 is problematic; however, the unit likely represents the surface of the cave floor into which bones became incorporated over time by resedimentation and bioturbation. Unit 2 represents deposition by suspension settling in a subglacial lake, indicating ice cover during the LGM. Unit 3 is interpreted as early postglacial and Holocene accumulation of resedimented fines (from unit 2) in standing water in topographic lows.
Unit 1 has yielded 4 radiocarbon dates from single bone fragments of known species ranging from 18.0-16.3 ka. These dates show that ice cover on the outer coast was brief, from ca. 15.5-14 ka. A diverse vertebrate fauna of marmot, vole, marten, cervid and various species of birds and fish indicates a partially treed landscape with the sea near its present level. The fact that relative sea level was close to the cave at a time when eustatic lowering would otherwise have placed the shoreline ~ 15 km away, implies significant isostatic depression. The terrestrial vertebrate fauna is consistent with a cool, open parkland environment with maximum summer temperatures cooler than present. Although most fossils represent small mammals, the presence of at least one cervid confirms viability for ungulates, a significant source of food for humans. The marine fauna also indicate the proximity of a rich marine environment and suggest that salmon runs, affording an abundant seasonal source of protein, likely existed prior to the LGM. The existence of this diverse vertebrate fauna as late as 16 ka demonstrates both marine and terrestrial resources available to support humans, confirming the viability of the coastal migration hypothesis for this portion of the route.










Early postglacial fossil bison from Vancouver Island, British Columbia, and Orcas Island, Washington: morphology, taxonomy and paleoecological setting

Wilson, M.C., Douglas College,
Hebda, R.J. and Keddie, G., Royal British Columbia Museum

An early postglacial fossil bison skull from marl below bog sediments in northern Saanich Peninsula, Vancouver Island, is identified as Bison antiquus. Morphological evidence suggests affinities with other bison populations in the midcontinent rather than with northern (Beringian) forms. A radiocarbon date of 11,750±110 yr BP indicates that bison were in this area in the relatively warm early postglacial, and associated pollen shows that they lived in a poplar parkland environment with sedge meadows. They likely were extirpated during the cooler Younger Dryas interval about a millennium later when coniferous forests expanded. The Saanich specimen has the broad, arched cranium and laterally directed horns of B. antiquus but relatively smaller horn cores than coeval Great Plains specimens, suggesting a suboptimal environmental setting. Other bison finds from Vancouver Island and from Orcas Island in the San Juan group, Washington, belong to the same time interval. The date and means of their arrival on these islands are not yet clear. If the area was completely ice-covered at the Fraser stage maximum (Vashon stade, ca. 14.5 ka) their arrival was postglacial, but if ice-free areas were locally present the animals may have been able to cross an outwash plain built in advance of Vashon ice and to have persisted in local refugia. Bison remains have also been recovered from pre-Vashon (Quadra equivalent) sediments on Vancouver Island.