GRAIN SIZE ANALYSIS OF STREAM SEDIMENTS IN BOW CREEK FEN IN MOUNTAIN TOP (LUZERNE CO.), PA

A tributary of Bow Creek in Mountaintop, PA, runs through a fen of approximately seven acres, dominated by leatherleaf-sedge vegetation, that is part of a conservation easement managed by the North Branch Land Trust. The fen occupies a depression, with the surrounding elevated area underlain by glacial sediments. We collected seven shallow sediment samples, approximately 10 cm in depth, from the stream channel upstream (south), within, and downstream (north) of the fen. The samples were treated with hydrogen peroxide to remove organic material. The sieve analysis involved wet-sieving for within-fen samples and dry sieving at 0.5 phi intervals for the sand fraction. The upstream sample contained a small amount of gravel (8%), with a large proportion of mud. The downstream sample sites were dominated by sand (76% - 96%) and gravel, with the modal sand size and the proportion of gravel increasing with distance downstream from the fen. Samples within the fen were dominated by mud, up to 89% -90%, and were extremely high in organic material. The stream channel feeding into the upstream end of the fen drains from another smaller wetland, is wide and shallow and is not the only source of water to the fen. In the upstream (southern) end of the fen there are numerous springs and seeps and several narrow and indistinct channels, so that it is very hard to determine the main flow. As the water moves through the fen, it becomes more and more channelized, and the stream draining the fen is narrow and channelized with rapid flow. The increase in flow rate is reflected in the grain size composition of the stream sediments.