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TitleOverview of late Quaternary stratigraphy in Saanich Inlet, British Columbia: results of Ocean Drilling Program Leg 169S
AuthorBlais-Stevens, A; Bornhold, B D; Kemp, A E S; Dean, J M; Vaan, A A
SourceMarine Geology 174, 2001 p. 3-26,
Alt SeriesGeological Survey of Canada, Contribution Series 1999236
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf
ProvinceBritish Columbia; Western offshore region
NTS92B/11; 92B/12
AreaSaanich Inlet
Lat/Long WENS-123.5833 -123.4167 48.7500 48.5000
Subjectsstratigraphy; surficial geology/geomorphology; drilling, offshore; paleoenvironment; paleoclimates; oceanography; oceanographic surveys; muds; sands; clays; silts; glaciation; Holocene; radiocarbon dating; lithostratigraphy; varves; glaciomarine deposits; depositional history; Pleistocene; Ocean Drilling Program Leg 169S; Mazama Volcanic Ash; Quaternary
Illustrationssketch maps; graphs; tables; stratigraphic sections; photographs
AbstractContinuous coring in Saanich Inlet (Ocean Drilling Program, ODP Leg 169S), British Columbia, Canada, yielded a detailed record of Late Quaternary climate, oceanography, marine productivity, and terrestrial vegetation. Two sites (1033 and 1034) were drilled to maximum depths of 105 and 118 m, recovering sediments ranging in age from 13,300 to less than 300 14C yr. Earliest sediments consist of dense, largely massive, gray glaciomarine muds with dropstones and sand and silt laminae deposited during the waning stages of glaciation. Deposition of organic-rich olive gray sediments began in the fjord about 12,000 14C yr ago, under well-oxygenated conditions as reflected by the presence of bioturbation and a diverse infaunal bivalve community. At about 10,500 14C yr, a massive, gray unit, 40-50 cm thick, was emplaced in a very short span of time. The unit is marked by a sharp lower contact, a gradational upper contact and an abundance of reworked Tertiary microfossils. It has been interpreted as resulting from massive flood events caused by the collapse of glacial dams in the Fraser Valley of mainland British Columbia. Progressively greater anoxia in bottom waters of Saanich Inlet began about 7000 14C yr ago. This is reflected in the preservation of varved sediments consisting of diatomaceous spring-summer laminae and terrigenous winter laminae. Correlation of the sediments was based on: marked lithologic changes, the presence of massive intervals (reflecting localized sediment gravity flow events), the Mazama Ash, occasional thin gray laminae (indicative of abnormal flood events in nearby watersheds), varve counts between marker horizons, and 71 accelerator mass spectrometry (AMS) radiocarbon dates.