Geology
The Raritan River was perhaps the major drainage channel along the ice front throughout the Wisconsin glaciation (Stages 1, 2, 3 and 4). Prior to that time the region drained southward across the saddle between the Atlantic Highlands and the Newark Basin into the Delaware River Valley. This saddle area is a very broad flood plain that preserves river terrace gravels (Pensauken Formation) from the Sangemon Interglacial State (Stage 5), as well as older Pleistocene fluvial deposits (The Bridgetown Formation). During the lowstand in sea level caused by the Wisconsin glacier, the Raritan River carved back into its headlands and captured the major drainages from the Newark Basin.
As the Wisconsin glaciers melted, the Flandrian Transgression eventually flooded the deeper valleys of the Hudson, Raritan, and Arthur Kill. During warming at the end of the Pleistocene and Early Holocene, the area encompassing Raritan Bay changed from tundra to a landscape dominated by spruce and pine forests. These forests gradually gave way to the modern deciduous forest in the region by mid-Holocene time. Lagoons and bays in the area around Sandy Hook hosted oysters, hard and soft shell clams, lobsters, blue crabs, and a variety of other invertebrates common in bays in the region today. South of western Long Island, tidal flats and wetlands occupied the margins of a tidal estuary (now submerged by marine waters). Inner Raritan Bay began to fill about 2,500 years ago with large oyster beds forming along the estuarine tributaries. Sea level continued to rise about one foot per century. This rise in sea level has resulted in the landward migration of the shoreline (aided by storm-induced coastal erosion) as much as two miles in some portions of the coast since colonial times.
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