A preliminary survey of relict shoreface-attached sand ridges in Western Lake Superior

Radiocarbon and stable‐isotope geochemistry of organic and inorganic carbon in Lake Superior

“…In large aquatic systems such as Lake Superior and the oceans, several entrainment, lateral transport and redeposition events are required to deposit sediments in the deeper basins, and that could lead to very old ( 14 C depleted) fine particles being present in these regions. The eastern basin, which exhibits more 14 C depletion in its POC samples, contains north‐south trending troughs covered by up to 13–15 cm of soft sediments sitting on top of stiff postglacial sediments due to the high currents that flow through [ Boyer and Hedrick , 1989; Wattrus and Rausch , 2001] whereas the western basin, whose POC radiocarbon signatures are more uniform, is characterized by very low relief with the exception of two deep troughs at the northwestern shore, which have thick deposits of sediments spanning several thousand years [ Wattrus and Rausch , 2001; Pearson , 2005].…”

“…For the resuspended sediments to considerably influence the lake water as suggested by the old ages of POC, strong bottom currents, and/or strong storms are required. Strong storms occur on the lake during spring and fall when the prevailing winds are out of northeast and are strong enough to erode and entrain sediments [ Wattrus and Rausch , 2001]. Previous studies have shown that the south shore is more susceptible to erosion than the north shore is [ Johnson and Johnston , 1995] with coastal erosion of clays being about 5 times faster at the south shore [ Wattrus and Rausch , 2001].…”

“…Strong storms occur on the lake during spring and fall when the prevailing winds are out of northeast and are strong enough to erode and entrain sediments [ Wattrus and Rausch , 2001]. Previous studies have shown that the south shore is more susceptible to erosion than the north shore is [ Johnson and Johnston , 1995] with coastal erosion of clays being about 5 times faster at the south shore [ Wattrus and Rausch , 2001]. Surface water circulation in the lake is mostly cyclonic whereas the bottom/deep circulation pattern in the lake is not well constrained, although thought to be generally cyclonic, flowing northeastward along the south shore [ Lam , 1978], suggesting that entrained sediments from the south shore would potentially influence the central and eastern regions, those exhibiting older radiocarbon POC values.…”

Stabilization of glaciers terminating in closed water bodies: Evidence and broader implications

“…On glaciated continental shelves, high‐resolution multibeam surveys have been used to map drowned glacial landforms [ Ottesen et al , 2005; Todd et al , 1999]. More recently, multibeam surveys have been used to study geologic processes in freshwater lakes [ Bacon et al , 2002; Gardner et al , 2000; Wattrus and Rausch , 2001].…”

Environmental conditions for gravelly and pebbly dunes and sorted bedforms on a moderate-energy inner shelf (Marettimo Island, Italy, western Mediterranean)

“…Several possibilities can be put forward to explain the origin of pebble dunes on the Marettimo shelf: a) there are episodic, high-energy storm events that have not yet been recorded in the study area during the 17 years of wave buoy records; b) the threshold hydrodynamic conditions for dune formation are lower than estimated because of the increased turbulence due to the high roughness associated with the coarse sediment or because grain entrainment only affects the finer fractions (Forbes and Boyd, 1986;Carling et al, 2006;Kuhnle et al, 2006); and c) deeper dunes are relict and were generated at shallow depths during the Holocene post-glacial marine transgression. However, favorable conditions for the preservation of these bedforms would be the presence of a thin layer of fine sediment that buried the paleo-shelf sedimentary structures and protected them from erosive and destructive actions (Brew, 1996) or the occurrence of a very low-energy environment during the sea level rise (Wattrus and Rausch, 2001). Neither of these…”