ORIGIN AND AGE OF FLUVIAL SEDIMENTS, CHARLESTON, STATEN ISLAND
There is some lateral variation within the outcrop, so two sections were logged and samples collected for analysis. The sediments consist of interbedded gravels and sands, with one partially lithified silt/clay layer. The gravels are poorly to very poorly sorted and show a bimodal grain size distribution with coarse pebbles and medium sand predominating. These layers are 20 – 80 cm thick and most likely represent crevasse splay deposits. The sand layers comprise moderately to poorly sorted medium sands, some of which display cross bedding containing fine gravels. They are not all laterally continuous, and represent migrating stream channel deposits. The silt/clay layer has been disrupted, probably by a crevasse splay, and is overlain by a gravel that includes rip up clasts of this mud.
Although there was no pollen or other organic matter found in the sediments collected, the age can be deduced from the composition of the clasts in the gravels. They include numerous red sandstones and siltstones, which are not normally associated with the Pensauken Formation, but are associated with similar Quaternary outwash deposits in neighboring parts of New Jersey. It is assumed that these sediments were deposited after the initial retreat of the ice sheet due to their location north of the terminal moraine. They were most likely deposited on an outwash plain as the ice continued to retreat, close to the shores of glacial Lake Bayonne.
Support for this project was provided by a PSC-CUNY Award, jointly funded by The Professional Staff Congress and The City University of New York.