Late Pleistocene stratigraphy and chronology of lower Chehalis River valley, southwestern British Columbia: evidence for a restricted Coquitlam Stade

2004 ◽  
Vol 41 (7) ◽  
pp. 881-895 ◽  
Author(s):  
Brent C Ward ◽  
Bruce Thomson
Keyword(s):  
British Columbia ◽  
Late Pleistocene ◽  
River Valley ◽  
Glacial Lakes ◽  
Coast Mountains ◽  
Source Areas ◽  
Definitive Evidence

Sediments in lower Chehalis valley span middle Wisconsin (Olympia nonglacial interval) to Holocene time. Sediments are divided into six units with chronological control provided by 14 new radiocarbon ages. Fluvial gravel spans the transition from the late Olympia nonglacial interval to the early Fraser Glaciation. Glaciolacustrine sedimentation represents the first definitive glacial activity in the valley and indicates that Vashon ice in the Fraser Lowland blocked the mouth of the Chehalis valley at ca. 18–17 ka BP. Ice then flowed down the Chehalis valley. The Chehalis valley deglaciated while ice persisted in the Fraser Lowland, forming another lake. After this lake drained, terraces and fans formed. This style of glaciation–deglaciation is typical of many watersheds peripheral to the Fraser Lowland in that local valley ice was slightly out of phase with ice in the lowland. This resulted in glacial lakes forming during both advance and retreat phases. However, in contrast to watersheds in the northwestern Fraser Lowland, no definitive evidence of a Coquitlam ice advance was found within the Chehalis valley. Although glaciers in the area were likely active and advancing, data from the Chehalis valley indicates that they were not as extensive as previously thought. Since ice source areas in the northeastern Fraser Lowland are in the leeward area of the Coast Mountains, it is suggested that lower precipitation resulted in limited glacier activity there during the Coquitlam Stade.

Late Pleistocene history and geomorphology, southwestern Vancouver Island, British Columbia

1979 ◽  
Vol 16 (9) ◽  
pp. 1645-1657 ◽  
Author(s):  
Neville F. Alley ◽  
Steven C. Chatwin
Keyword(s):  
British Columbia ◽  
Continental Shelf ◽  
Late Pleistocene ◽  
Vancouver Island ◽  
Glacial Lakes ◽  
Small Lakes ◽  
Strait Of Georgia ◽  
Coast Mountains ◽  
Juan De Fuca ◽  
Juan De Fuca Strait

The major Pleistocene deposits and landforms on southwestern Vancouver Island are the result of the Late Wisconsin (Fraser) Glaciation. Cordilleran glaciers formed in the Vancouver Island Mountains and in the Coast Mountains had advanced down Strait of Georgia to southeastern Vancouver Island after 19 000 years BP. The ice split into the Puget and Juan de Fuca lobes, the latter damming small lakes along the southwestern coastal slope of the island. During the maximum of the glaciation (Vashon Stade), southern Vancouver Island lay completely under the cover of an ice-sheet which flowed in a south-southwesterly direction across Juan de Fuca Strait, eventually terminating on the edge of the continental shelf. Deglaciation was by downwasting during which ice thinned into major valleys and the strait. Most upland areas were free of ice down to an elevation of 400 m by before 13 000 years BP. A possible glacier standstill and (or) resurgence occurred along Juan de Fuca Strait and in some interior upland valleys before deglaciation was complete. Glacial lakes occupied major valleys during later stages of deglaciation.

Quadra Sand and its relation to the late Wisconsin glaciation of southwest British Columbia

1976 ◽  
Vol 13 (6) ◽  
pp. 803-815 ◽  
Author(s):  
J. J. Clague
Keyword(s):  
British Columbia ◽  
Climatic Change ◽  
Late Pleistocene ◽  
Marine Sediments ◽  
Strait Of Georgia ◽  
Coast Mountains ◽  
Widespread Distribution ◽  
Source Areas ◽  
The North ◽  
Minimum Age

Quadra Sand is a late Pleistocene lithostratigraphic unit with widespread distribution in the Georgia Depression, British Columbia and Puget Lowland, Washington. The unit consists mainly of horizontally and cross-stratified, well sorted sand. It is overlain by till deposited during the Fraser Glaciation and is underlain by fluvial and marine sediments deposited during the preceding nonglacial interval.Quadra Sand was deposited progressively down the axis of the Georgia–Puget Lowland from source areas in the Coast Mountains to the north and northeast. The unit is markedly diachronous; it is older than 29 000 radiocarbon years at the north end of the Strait of Georgia, but is younger than 15 000 years at the south end of Puget Sound.Aggradation of the unit occurred during the climatic deterioration at the beginning of the Fraser Glaciation. Thick, well sorted sand was deposited in part as distal outwash aprons at successive positions in front of, and perhaps along the margins of, glaciers advancing from the Coast Mountains into the Georgia–Puget Lowland during late Wisconsin time.The sand thus provides a minimum age for the initial climatic change accompanying the Fraser Glaciation. This change apparently occurred before 28 800 y BP, substantially earlier than glacial occupation of the southern Interior Plateau of British Columbia. Thus, several thousand years may have intervened between the alpine and ice-sheet phases of the Fraser Glaciation.

Eocene paleo-physiography and drainage directions, southern Interior Plateau, British Columbia

2005 ◽  
Vol 42 (2) ◽  
pp. 215-230 ◽  
Author(s):  
Selina Tribe
Keyword(s):  
British Columbia ◽  
Middle Eocene ◽  
Regional Scale ◽  
River Valley ◽  
Coast Mountains ◽  
Base Level ◽  
The North ◽  
Bedrock Geology ◽  
River Valleys ◽  
Early Cenozoic

A map of reconstructed Eocene physiography and drainage directions is presented for the southern Interior Plateau region, British Columbia south of 53°N. Eocene landforms are inferred from the distribution and depositional paleoenvironment of Eocene rocks and from crosscutting relationships between regional-scale geomorphology and bedrock geology of known age. Eocene drainage directions are inferred from physiography, relief, and base level elevations of the sub-Eocene unconformity and the documented distribution, provenance, and paleocurrents of early Cenozoic fluvial sediments. The Eocene landscape of the southern Interior Plateau resembled its modern counterpart, with highlands, plains, and deeply incised drainages, except regional drainage was to the north. An anabranching valley system trending west and northwest from Quesnel and Shuswap Highlands, across the Cariboo Plateau to the Fraser River valley, contained north-flowing streams from Eocene to early Quaternary time. Other valleys dating back at least to Middle Eocene time include the North Thompson valley south of Clearwater, Thompson valley from Kamloops to Spences Bridge, the valley containing Nicola Lake, Bridge River valley, and Okanagan Lake valley. During the early Cenozoic, highlands existed where the Coast Mountains are today. Southward drainage along the modern Fraser, Chilcotin, and Thompson River valleys was established after the Late Miocene.

Late Quaternary glacial and interglacial environments of the Nechako River - Cheslatta Lake area, central British Columbia

2001 ◽  
Vol 38 (4) ◽  
pp. 719-731 ◽  
Author(s):  
A Plouffe ◽  
V M Levson
Keyword(s):  
British Columbia ◽  
Late Quaternary ◽  
Late Glacial ◽  
Lake Area ◽  
Glacial Lakes ◽  
Ice Flow ◽  
Coast Mountains ◽  
Quaternary Stratigraphy ◽  
History Of ◽  
Quaternary History

The Quaternary stratigraphy of the Nechako River – Cheslatta Lake area of central British Columbia is described and interpreted to reconstruct the late Quaternary history of the region. Exposures of glacial and nonglacial sediments deposited prior to the last glaciation (Fraser) are limited to three sites. Pollen assemblages from pre-Fraser nonglacial sediments at two of these sites reveal forested conditions around 39 000 BP. During the advance phase of the Fraser Glaciation, glacial lakes were ponded when trunk glaciers blocked some tributary valleys. Early in the glaciation, the drainage was free in easterly draining valleys. Subsequently, the easterly drainage was blocked either locally by sediments and ice or as a result of impoundment of the Fraser River and its tributaries east of the study area. Ice generally moved east and northeast from accumulation zones in the Coast Mountains. Ice flow was influenced by topography. Major late-glacial lakes developed in the Nechako River valley and the Knewstubb Lake region because potential drainage routes were blocked by ice.

Late Pleistocene debris-flow deposits in large glacial lakes in British Columbia and Alaska

1987 ◽  
Vol 53 (1-2) ◽  
pp. 33-71 ◽  
Author(s):  
Nicholas Eyles
Keyword(s):  
British Columbia ◽  
Debris Flow ◽  
Late Pleistocene ◽  
Glacial Lakes

A Middle pleistocene (isotope stage 10) glacial sequence in the Stikine River valley, British Columbia

1996 ◽  
Vol 33 (10) ◽  
pp. 1428-1438 ◽  
Author(s):  
Ian S. Spooner ◽  
Gerald D. Osborn ◽  
H. Barendregt ◽  
E. Irving
Keyword(s):  
British Columbia ◽  
Magnetic Polarity ◽  
River Valley ◽  
Middle Pleistocene ◽  
Glacial Period ◽  
Basalt Flow ◽  
Coast Mountains ◽  
Normal Polarity ◽  
Ice Retreat ◽  
Glacial Advance

In the Stikine River valley, northwestern British Columbia, glacial and nonglacial sediments are preserved beneath Middle Pleistocene basalt-flow remnants that originated from Mount Edziza. The magnetic polarity is consistently normal, indicating that the sediment and the basalts were probably deposited within the Bruhnes normal polarity chron (<780 ka). The sediments record a regional glacial advance. Initial ice advance in the Coast Mountains blocked the westward drainage of the Stikine River and formed an advance-phase glacial lake. Sediments deposited in this lake form a coarsening-upwards sequence; debris-flow diamicton units that originated from the valley sides are common. The lacustrine sequence culminates in a poorly sorted ice-marginal gravel deposited as ice encroached upon the study area. There is little record of ice retreat. The basalts are deposited on fluvial and (or) glaciofluvial gravels, indicating that postglacial reincision was taking place at the time of eruption. Hence, the sediments were deposited in the glacial period immediately prior to the emplacement of the basalt. Evidence is presented that indicates that glacial conditions occurred between 341 and 352 ka, which corresponds to pre-Illinoian isotope stage 10.

Younger Dryas readvance in Squamish river valley, southern Coast mountains, British Columbia

2002 ◽  
Vol 21 (18-19) ◽  
pp. 1925-1933 ◽  
Author(s):  
Pierre A. Friele ◽  
John J. Clague
Keyword(s):  
British Columbia ◽  
Younger Dryas ◽  
River Valley ◽  
Southern Coast ◽  
Coast Mountains

TAXONOMY, DISTRIBUTION, AND ZOOGEOGRAPHIC EVOLUTION OF GRYLLOBLATTA IN CANADA (INSECTA: NOTOPTERA)

1979 ◽  
Vol 111 (1) ◽  
pp. 27-38 ◽  
Author(s):  
J. W. Kamp
Keyword(s):  
British Columbia ◽  
New Species ◽  
Late Pleistocene ◽  
Rocky Mountain ◽  
Coast Mountains ◽  
New Subspecies ◽  
Present Distribution ◽  
Species Groups ◽  
A New Species

AbstractA new species of Grylloblatta from the Coast Mountains of British Columbia and two new subspecies of Grylloblatta campodeiformis Walker from northern British Columbia are described and figured. The distribution of the species groups from the Rocky Mountain and Coast–Cascade Cordillera are indicated. An interpretation of the present distribution as a result of late Pleistocene and Holocene geological and climatic events is presented.

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