Late Quaternary sediments and geomorphic history of northern Vancouver Island, British Columbia

1983 ◽  
Vol 20 (1) ◽  
pp. 57-65 ◽  
Author(s):  
D. E. Howes
Keyword(s):  
British Columbia ◽  
Late Quaternary ◽  
Mass Movement ◽  
Vancouver Island ◽  
Alluvial Fan ◽  
Eastern Coast ◽  
Sedimentary Environments ◽  
History Of ◽  
Floodplain Deposits ◽  
Organic Deposits

Materials from two glacial intervals and one nonglacial interval have been identified on northern Vancouver Island, British Columbia. The oldest Pleistocene unit, termed "older drift," consists of glaciomarine silt and clay >38 000 years BP in age that overlie a till that has only been recorded in well logs. "Older drift" is tentatively correlated with Dashwood drift of the Semiahmoo Glaciation (early Wisconsin or older). No sediments of the succeeding Olympia nonglacial interval (mid-Wisconsin) have been found in the area. It is thought that this interval was characterized by a period of degradation in which Olympia-age sediments were deposited in transient sedimentary environments and subsequently eroded, in part during the Fraser Glaciation (late Wisconsin). The youngest Pleistocene unit, termed Port McNeill drift, includes advance deposits, till, and deglacial sediments, all deposited during Fraser Glaciation. Ice of this glaciation did not cover most of northern Vancouver Island until after 20 600 ± 330 years BP. At the maximum, which probably occurred about 15 000 years ago, Coast Mountain ice coalesced with and overrode Vancouver Island ice, and flowed in a westerly to northwesterly direction across northern Vancouver Island. Deglaciation commenced prior to 12 930 ± 160 years BP and possibly as early as 13 630 years ago on the eastern coast. Maximum sea level during and immediately following deglaciation was about 92 and 20 m elevation on the east and west coasts, respectively. This suggests that ice thickness at the Fraser maximum decreased westward across the study area. Deposits of Recent time include colluvial sediments formed by weathering and mass movement processes, alluvial fan and floodplain deposits, eolian sands associated with active beaches on the west coast, and organic deposits.

Sedimentary Environments and Late Quaternary History of a 'Low-Energy' Mountain Delta

1975 ◽  
Vol 12 (12) ◽  
pp. 2004-2013 ◽  
Author(s):  
Norman D. Smith
Keyword(s):  
Late Quaternary ◽  
Coarse Sand ◽  
Alluvial Fan ◽  
High Mountain ◽  
Fine Grained ◽  
Sedimentary Environments ◽  
Coarse Sediment ◽  
History Of ◽  
Quaternary History ◽  
Time Of Origin

Due to its low input of coarse sediment, Upper Waterfowl Lake, in Banff Park, Alberta, has developed a delta atypical of lacustrine deltas in this high mountain region: lack of foresets, vertically aggrading stable distributary channels, and a surface composed of mostly fine-grained floodplain materials. Deltaic progradation has outrun the supply of coarse sediment, resulting in entrapment of all gravel and coarse sand in proximal channels.Data provided by auger samples, including stratigraphic positions of Mazama and Bridge River volcanic ashes, suggest the lake was formed about 8800 years ago when deposition of a large alluvial fan blocked the Mistaya River at the upper end of Lower Waterfowl Lake. The delta has undergone two progradations, one beginning at the lake's time of origin, the other following a renewed lake level rise some 2300 years ago. Mean aggradation rates since Mazama time (6600 y BP) have been approximately steady at about.05 cm/y. Pre-Mazama lake sediments, however, were deposited more than twice as fast as a result of accelerated sedimentation rates that accompanied deglaciation.

Late Quaternary sediments and geomorphic history of north-central Vancouver Island

1981 ◽  
Vol 18 (1) ◽  
pp. 1-12 ◽  
Author(s):  
D. E. Howes
Keyword(s):  
Late Quaternary ◽  
Lacustrine Sediments ◽  
Late Glacial ◽  
Vancouver Island ◽  
Time Span ◽  
Quaternary Sediments ◽  
Single Exposure ◽  
North Central ◽  
Sedimentary Environments ◽  
History Of

Materials from two glacial and two nonglacial intervals are identified on north-central Vancouver Island, British Columbia. The oldest Pleistocene unit, Muchalat River drift, consists of till and overlying glaciolacustrine silt. It has been tentatively correlated with Dashwood drift of the Semiahmoo Glaciation. An overlying single exposure of mudflow sediment in the Gold River valley contains wood dated at 40 900 ± 2000 years BP within the time span of the Olympia nonglacial interval. The Olympia nonglacial interval was characterized by a period of degradation in which Olympia-age sediments were deposited in transient sedimentary environments and subsequently eroded. Gold River drift includes Gold River advance deposits, Gold River till, and Gold River late glacial deposits, and was deposited during the Fraser Glaciation. The Fraser Glaciation was well underway on north-central Vancouver Island by 25 200 ± 330 years BP. During the Fraser Glaciation maximum, which occurred after 20 600 ± 330 years BP, Coast Mountain ice flowed in a southwesterly direction across north-central Vancouver Island overtopping all but the highest peaks of the Vancouver Island Mountains. Deglaciation commenced prior to 12 930 ± 160 years BP and the ice had probably disappeared before 9500 years ago. During postglacial times rivers have dissected older Quaternary sediments and bedrock up to at least 40 m. Macroflora data recorded in postglacial lacustrine sediments suggest that the Hypsithermal Interval commenced before 8300 ± 70 years BP.

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.

Holocene history of earthflow mass movements in south-central British Columbia: the influence of hydroclimatic changes

1992 ◽  
Vol 29 (8) ◽  
pp. 1746-1755 ◽  
Author(s):  
Michael J. Bovis ◽  
Penny Jones
Keyword(s):  
British Columbia ◽  
Mass Movement ◽  
The Holocene ◽  
Wood Development ◽  
The Past ◽  
South Central ◽  
History Of ◽  
Changing Rate ◽  
Coherent Relationship ◽  
Past 300 Years

Large earthflows in south-central British Columbia have exhibited regionally consistent fluctuations in their movement during the Holocene. Over the past 60 years, air photographs show that many earthflows were reactivated during the relatively wet period 1950–1985. Over the past 300 years, a fairly coherent relationship is established between periods of wetter climate, defined by the tree-ring record, and phases of slope movement, defined by the record of compression-wood development in conifers located near earthflow headscarps. On a time scale of several thousand years, stratigraphic evidence shows that many large earthflows in the region underwent significant reactivation of movement in the post-Mazama period, during the relatively wet, cool Neoglacial interval of the Holocene. These lines of evidence indicate that Holocene hydroclimatic changes have exerted an important influence on the regimen of large earthflows. Earthflows present a wealth of paleogeomorphic information, hitherto largely neglected, that allows a reconstruction of the changing rate of mass movement with time.

On the Boots of Fishermen: The History of Didymo Blooms on Vancouver Island, British Columbia

Fisheries ◽  
2009 ◽  
Vol 34 (8) ◽  
pp. 382-388 ◽  
Author(s):  
Max L. Bothwell ◽  
Donovan R. Lynch ◽  
Harlan Wright ◽  
John Deniseger
Keyword(s):  
British Columbia ◽  
Vancouver Island ◽  
History Of

scholarly journals Reconnaissance sediment budgets for Lynn Valley, British Columbia: Holocene and contemporary time scales

2003 ◽  
Vol 40 (5) ◽  
pp. 701-713 ◽  
Author(s):  
David Campbell ◽  
Michael Church
Keyword(s):  
British Columbia ◽  
Drainage Basin ◽  
Mass Movement ◽  
Alluvial Fan ◽  
Stream Channel ◽  
Sediment Sources ◽  
Stream Channels ◽  
Photographic Analysis ◽  
Sediment Transfer ◽  
Channel Degradation

Volumes of erosional and depositional landforms were estimated by reconnaissance methods in a steep, forested drainage basin in the Coast Mountains, British Columbia, to examine what insight might be gained into the sediment budget in the absence of direct measurements of sediment transfer processes. Sediment transfers in postglacial and contemporary time were inferred on hillslopes, from hillslopes to stream channels, and within stream channels. Data were collected by aerial photographic analysis and field observation. Postglacial sediment sources are major gullies created by debris slides and flows, failures in glaciolacustrine terraces, and stream channel degradation. Depositional landforms consist of talus slopes and colluvial and alluvial fans. Contemporary sediment sources include debris slides and flows in established gullies and minor processes on hillslopes. Debris slide and debris flow volumes were calculated, and other processes were estimated from regional values. Erosion rate averaged over postglacial time is 276 t·km–2·a–1 (0.15 mm·a–1 surface lowering), with gullies and stream channel degradation contributing 170 and 82 t·km–2·a–1, respectively. A terminal alluvial fan provides an independent check of the results. In contemporary time, erosion rates are calculated to be 350 t·km–2·a–1, with debris flows and slides contributing nearly all of this sediment. The contemporary rate is probably perturbed by recent land use history. Mass-movement processes appear to be the dominant mechanism of sediment transfer and, contributions from Pleistocene valley deposits have declined significantly during Holocene time.

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