AGE AND ORIGIN OF NY BIGHT CONCRETIONS

The New York Bight is a shallow body of water located between Long Island and New Jersey. Sedimentation in the Bight is attributed to differential erosion from coastal plain sediments along with sediments derived from the Pleistocene glaciation. Fossiliferous concretions deriving from these sediments are washed up on New York and New Jersey beaches in the apex of the Bight. Concretion abundance decreases with distance from the Apex. Fossils within concretions are of species presently living in Bight waters. Some concretions contain estuarine species such as Crassostrea virginica, while others contain shoreface and nearshore forms such as Anomia simplex and Mytilus edulis, thus indicating that concretions originally formed in different coastal environments. Thin section study of concretion framework materials suggests that most concretions are composed predominately of angular, fine to coarse quartz grains. Pollen grains and foraminifera, including Globigerina bulloides, have been found in concretion thin sections. XRF analyses indicate that in addition to Si, Fe, and Ca, many concretions show the presence of rare earth elements. Included in this grouping are the elements: Sr, Nd, Ba, Ce, and Pr. Concretions that are similar in elemental content are also relatively similar in physical characteristics such as color, matrix, and grain size. We suggest that there are probably multiple sources for concretions and that concretion occurrences on NY Bight beaches are produced by relatively stable or repetitive current patterns. Several carbonate shells from various concretions have produced an age of ~6,000 Years before present (BP). At this time sea level rise first flooded the Bight with seawater, creating the modern Bight Apex configuration of shorelines and estuaries. Thus, 6000 yr BP may represent the time when concretion formation first commenced in the Bight apex. Multiple fossils within a concretion often have different radiocarbon ages. This suggests that concretions form at different times between now and 6000 yrs BP. A unique textile fragment was found within a Sandy Hook concretion having an age of 529 yrs BP. This predates European voyages to Bight waters and suggests a Native American origin for the textile, probably Lenni Lanape - the people who inhabited the mid-Atlantic region at this time.