Origin and Age of Fluvioglacial Sediments on Staten Island NY and Implications for Meltwater Flow

In the northeastern United States, sediments related to the expansion and contraction of the Laurentide ice sheet have been extensively mapped throughout New England, as well as in New Jersey and on Long Island. However, linking these deposits around New York City is challenging due to the extensive urbanization. Staten Island is less developed than the other boroughs of New York City, however outcrops of rock and surface sediment are limited, making interpretation of its geologic history challenging. When small areas of sediment are temporarily exposed, they can be used to improve our understanding of sediment erosion and deposition over time, helping to link the deposits mapped in New Jersey and Long Island. In this study of two small temporary outcrops, the beds of sediment were measured and described in the field and samples were collected for textural and compositional analyses. The results were interpreted in the context of previous work on similar exposures nearby. The sediments are sands and gravels of fluvioglacial origin containing reworked sediments of both the Pliocene Pensauken Formation and older Triassic rocks of the Newark Basin, interpreted to have been deposited on an outwash plain during the Illinoian glaciation (Marine Isotope Stage 6). They were deposited in a topographic low directly overlying Cretaceous sedimentary rocks, but adjacent to sediments of the Pensauken Formation which had in turn been deposited as an earlier valley fill. Similar sequences of repeated valley fills have been observed in New Jersey but have not been documented on Staten Island. This interpretation solves an apparent disagreement between previous studies by illustrating how both the Pensauken Formation and later fluvioglacial sediments can directly overly Cretaceous sediments across a distance of less than a kilometer.