Subsurface geology and paleogeography of Queens County, Long Island, New York

Unconsolidated strata of clay, silt, sand, and gravel of Late Cretaceous and pre-Wisconsin Pleistocene ages lie between crystalline basement rocks (bedrock) of Precambrian ( ) age and unconsolidated deposits of late Pleistocene (Wisconsin) and Holocene ages in Queens County, Lond Island, N.Y. Data collected during a recent study of the hydrogeology of the county and updated records of earlier studies have been used to prepare contour maps that delineate the surfaces of the bedrock and the Upper Cretaceous and pre-Wisconsin Pleistocene deposits. The presence of diabase fragments apparently from the Hudson Palisades in a buried valley through the county suggests that the ancestral Hudson River was diverted into Queens County in Pleistocene time. The contour maps are useful to engineers, ground-water-supply managers, well drillers, and others concerned with subsurface geology in the area. A map showing the apleotopography and geology at the time of the ancestral Hudson River 's entrance into the county is useful in understanding the areal geomorphology. (Woodard-USGS)