| Abstract/Description or Keywords |
Reconstruction of the geomorphic history of the Moose Lake delta is used to infer environmental change in the uppermostFraser River watershed, British Columbia. Delta-top changes are interpreted from surface channel morphology, riverbankexposures, hand auger data, vibracores and other borehole records. River channel and overbank sediments are related to sourcearea contributions in terms of granule lithology and fine ( < 63 Am) fraction geochemistry. A substantial area of the northeastdelta-top floodplain dates from the early Holocene, and is characterized by fragmentary, low-discharge paleochannels with bedmaterial characteristic of the uppermost Fraser River sub-basin. Floodplain development since ca. 4.0 ka BP has been limited tothe western and southern areas of the delta and records persistently higher sediment loads, aggradation and larger, more activechannels. These changes reflect overall shifts from warm, dry Hypsithermal to cooler, wetter Neoglacial climatic conditionsdefined regionally. The composition of both laterally and vertically accreted floodplain sediments plus channel morphology andfloodplain stratigraphy record the changing influence of partially glaciated source areas on the Holocene sediment flux.Specifically, periods of climatic deterioration and possibly glacier expansion lead to relatively greater yields of carbonate-richsediment from the higher elevation Moose River sub-basin. Storage and reworking of sediments on the Moose Lake delta-topfloodplain influence interpretation of the more distal lacustrine record. Over the last 4000 years, gradual increases in lacustrinesedimentation rate of up to f 18% are inferred to result from delta progradation.D 2003 Elsevier Science B.V. All rights reserved.Keywords: Delta; Floodplain; Sediment yield; Provenance; Holocene; Canadian Rockies; Climatic change |
