Contemporary sedimentation rates and depositional structures in a montane lake basin, southern Coast Mountains, British Columbia, Canada

Abstract

Spatial variability of recent lacustrine sedimentary structures and sedimentation rates are examined for Green Lake, a morphologically complex lake basin of the southern Coast Mountains, British Columbia. A dense, 100 m grid sampling scheme was used for sediment coring within the 2 km 2 lake basin. Deltaic, massive, weakly laminated, and varved sediment sequences are identified within the sediment record. Spatial patterns among these sedimentary deposits are related to within-lake sediment transfer processes, morphometric controls, and the extent of post-depositional mixing by bioturbation. Unconformities, turbidites, and cohesive slump failure deposits, observed within the contemporary varve sequences, could all be correlated with major flooding events in the catchment area and direct anthropogenic disturbances along the shoreline. There is an overall, non-linear decrease in sedimentation rates with increasing distance from the lake inflows; however, this pattern is disrupted in deep water sites of intervening lake sub-basins where locally higher accumulation rates are observed. Spatial sedimentation patterns are quantitatively described by an empiricallyderived model. Systematic variations in the model parameters are observed for different lake sub-regions and are associated with changing sediment transfer dynamics between proximal and distal sub-basin settings.

Bulk organic geochemistry of sediments from Puyehue Lake and its watershed (Chile, 40°S): Implications for paleoenvironmental reconstructions

“…Distances to secondary river and shore were given half weighting to account for their smaller contribution to the total sediment supply compared to major rivers. We used the logarithm of the distance to account for the globally exponential decrease of sediment accumulation rate with increasing distance to the source (Schiefer, 2006). Local variations might be explained by differences in basin shape and height of the water column.…”

Predicting Sediment Physical Properties within a Montane Lake Basin, Southern Coast Mountains, British Columbia, Canada

“…This may be due to reduced time for sediment compaction and consolidation associated with locally rapid deposition effects. Recent fine-grained deposition within the proximal basin exceeded maximum mid and distal basin sedimentation rates by a factor of 2.5 and 6.0, respectively (Schiefer 2004). Between the mid and distal lake sub-basins was another localized depression in the density transect associated with increased organic debris adjacent to the mid-20th century sawmill site.…”

“…The surficial sample (top 1 cm) represented a depositional period ranging from about a year in the proximal basin to over a decade in many distal lake settings (Schiefer 2004). Master cores were additionally sampled vertically using a regular 1-cm down-core interval.…”

Interdecadal patterns of total sediment yield from a montane catchment, southern Coast Mountains, British Columbia, Canada

“…Evidence that the couplets represent varves include (i) independently derived ages obtained using 137 Cs activity of the sediments; (ii) the presence of two dated anthropogenic markers observed in some nearshore sediment cores; and (iii) new couplets being predictably observed in cores taken in subsequent years (Schiefer, 2006a). The lack of intervening water bodies or active floodplains between the lake and sediment source areas suggests that the intermediate storage potential of silt and clay is low.…”