Submerged late quaternary terrestrial deposits and paleoenvironment of northern Hecate Strait, British Columbia continental shelf, Canada

Barrie, J. Vaughn; Conway, Kim W.; Mathewes, Rolf W.; Josenhans, H; Johns, Marji J.

doi:10.1016/1040-6182(93)90041-d

Cited by 39 publications

(3 citation statements)

References 12 publications

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“…Many plant species that now grow in southeastern (SE) Alaska appear to have spread northward along the coast into the region perhaps from as far south as coastal areas of Washington State or refugia along the B.C. coast and its exposed continental shelf (Heusser, 1960(Heusser, , 1989Luternauer et al, 1989;Barrie et al, 1994;Fedje and Josenhans, 2000;Lacourse et al, 2003;Lacourse, 2005;Lacourse and Mathewes, 2005;Mathewes and Clague, 2017). However, the early, rapid spread of some tree species, especially pine, during and following deglaciation suggests that some plant populations probably survived in refugia within SE Alaska, and the Queen Charlotte Islands (Haida Gwaii) of B.C.…”

Section: Introductionmentioning

confidence: 99%

Late Quaternary Vegetation Development Following Deglaciation of Northwestern Alexander Archipelago, Alaska

Ager

2019

Front. Earth Sci.

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The Cordilleran Ice Sheet covered most of southeastern Alaska during the Last Glacial Interval (LGI: Marine Isotope Stage 2). Ice began to recede from western Alexander Archipelago ∼17,000 ± 700 yr BP. In this study, pollen analysis and radiocarbon dating of three sediment cores were used to reconstruct, for the first time, the postglacial development of vegetation in the northwestern Alexander Archipelago during the past ∼15,240 cal yr. Hummingbird Lake (HL), on southwestern Baranof Island, yielded a sediment core with one of the longest dated records from southeastern Alaska. The earliest part of the HL pollen record (∼15,240-14,040 yr BP) indicates that the earliest vegetation was pine (Pinus contorta subsp. contorta) parkland with willows (Salix), heaths (Ericaceae), sedges (Cyperaceae), grasses (Poaceae), herbs and ferns. Starting at ∼14,040 yr BP, alder (Alnus) rapidly colonized the area as pine populations declined. By 11,400 yr BP, Sitka spruce (Picea sitchensis) colonized the area, and soon became the dominant conifer. Mountain hemlock (Tsuga mertensiana) also colonized the area by ∼11,400 yr BP, followed by western hemlock (Tsuga heterophylla) at ∼10,200 yr BP. By ∼9200 yr BP, western hemlock had become the dominant tree species in the area. During the late Holocene yellow cedar (Chamaecyparis nootkatensis) became established. Two marine sediment cores were also analyzed for pollen, with the oldest core from Lower Sitka Sound, between Kruzof and Baranof Islands. The lower part of the core consists of interlayered tephras and freshwater lake muds that are estimated to be ∼14,000 to 13,150 yr BP. Pollen evidence indicates that the early postglacial vegetation around Sitka Sound was pine parkland with alders and abundant ferns. Damage to vegetation around Sitka Sound by volcanic eruptions is suggested by abrupt, large shifts in percentages of alder and pine pollen, and fern spores in samples adjacent to tephra layers. A marine sediment core from Slocum Arm, a fiord on the western coast of Chichagof Island, has a basal age of ∼10,000 yr BP. The pollen record is similar to the Holocene pollen record at Hummingbird Lake. The sequence of vegetation changes interpreted from the three northwestern Alexander Archipelago pollen records is similar to those from other well-dated sites in southeastern Alaska, although chronologies differ between sites.

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Section: Introductionmentioning

confidence: 99%

Late Quaternary Vegetation Development Following Deglaciation of Northwestern Alexander Archipelago, Alaska

Ager

2019

Front. Earth Sci.

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“…There may have been ice-free areas on the islands and on the coastal lowlands of northern Haida Gwaii where glaciation was minimal and of short duration (Clague et al, 1982a;Clague, 1989;Mathewes and Clague, 2017). The limited size and extent of the Queen Charlotte Mountain source areas and the proximity of deep water of the open Pacific Ocean, Dixon Entrance, and Queen Charlotte Sound limited expansion of ice on the Haida Gwaii islands (Clague, 1981(Clague, , 1989Warner et al, 1982;Barrie et al, 1993;Barrie and Conway, 1999).…”

Section: Glacial Historymentioning

confidence: 99%

“…Emergence of the continental shelf off western Haida Gwaii by greater than 150 m at the beginning of the Holocene has been postulated (Barrie and Conway, 1999;. This is thought to have been a consequence of a migrating glacial forebulge with a very thick (2500 m) ice load on the mainland of British Columbia (Clague, 1983) and a limited ice load on Haida Gwaii and in Hecate Strait (Clague, 1989;Barrie et al, 1991Barrie et al, , 1993, during a period of eustatic sea-level lowering. Within the largest inlet on western Haida Gwaii, Rennell Sound, sea-level lowstand occurred just prior to 12.6 ka accompanied by significant deposition.…”

Section: Late Quaternary Sea-level Changementioning

confidence: 99%

Late Quaternary sea level, isostatic response, and sediment dispersal along the Queen Charlotte fault

2021

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The active Pacific margin of the Haida Gwaii and southeast Alaska has been subject to vigorous storm activity, dramatic sea-level change, and active tectonism since glacial times. Glaciation was minimal along the western shelf margin, except for large ice streams that formed glacial valleys to the shelf break between the major islands of southeast Alaska and Haida Gwaii. Upon deglaciation, sediment discharge was extensive, but it terminated quickly due to rapid glacial retreat and sea-level lowering with the development of a glacio-isostatic forebulge, coupled with eustatic lowering. Glacial sedimentation offshore ended soon after 15.0 ka. The shelf became emergent, with sea level lowering by, and possibly greater than, 175 m. The rapid transgression that followed began sometime before 12.7 ka off Haida Gwaii and 12.0 ka off southeast Alaska, and with the extreme wave-dominated environment, the unconsolidated sediment that was left on the shelf was effectively removed. Temperate carbonate sands make up the few sediment deposits presently found on the shelf. The Queen Charlotte fault, which lies just below the shelf break for most of its length, was extensively gullied during this short period of significant sediment discharge, when sediment was transported though the glacial valleys and across the narrow shelf through fluvial and submarine channels and was deposited offshore as sea level dropped. The Queen Charlotte fault became the western terminus of the glacio-isostatic forebulge, with the fault acting as a hinged flap taking up the uplift and collapse along the fault of 70+ m. This may have resulted in the development of the distinctive fault valley that presently acts as a very linear channel pathway for sediment throughout the fault system.

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Palaeogeographic Reconstruction of Hecate Strait British Columbia: Changing Sea Levels and Sedimentary Processes Reshape a Glaciated Shelf

Barrie

Conway

2012

Sediments, Morphology and Sedimentary Processes on Continental Shelves

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Submerged late quaternary terrestrial deposits and paleoenvironment of northern Hecate Strait, British Columbia continental shelf, Canada

Cited by 39 publications

References 12 publications

Late Quaternary Vegetation Development Following Deglaciation of Northwestern Alexander Archipelago, Alaska

Late Quaternary Vegetation Development Following Deglaciation of Northwestern Alexander Archipelago, Alaska

Late Quaternary sea level, isostatic response, and sediment dispersal along the Queen Charlotte fault

Palaeogeographic Reconstruction of Hecate Strait British Columbia: Changing Sea Levels and Sedimentary Processes Reshape a Glaciated Shelf

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