The maps presented in this report (depth to Coastal Plain unconformity, Quaternary
sediment thickness, paleochannel thickness, and modern sand thickness) are helpful
for determining sand-resource availability for beach nourishment programs and
understanding the influence that the inner-shelf framework of southern Long Island
has on coastal processes and evolution. The maps showing structure of the Coastal
Plain unconformity and thickness of overlying Quaternary sediment delineate the
framework of the coastal region. The map showing the distribution and thickness
of paleochannel fill indicates areas not suitable as sources for beach nourishment,
assuming the channels contain muddy estuarine deposits. The areas between channels
are Pleistocene glacial deposits and probably consist of coarse sediment that
may be suitable for beach nourishment. These coarser-grained glacial deposits
are the source for modern sand deposits. The modern sands have been reworked primarily
from glacial deposits and a Cretaceous outcrop off Watch Hill. These reworked
deposits provide well-sorted clean sand that have and will provide nourishment
for southern Long Island beaches.
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