Selective sediment transport during Hurricane Sandy on Fire Island (New York, USA): Inferences from heavy-mineral assemblages

Journal of Sedimentary Research
By: , and 

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Abstract

In October 2012, Hurricane Sandy caused severe erosion on beaches and dunes of Fire Island (New York, USA). Major shoreline changes occurred with erosional dominance in the upper shoreline and aggradation in the lowermost section of the beach due to the deposition of eroded upper beach and dune sediment. Sand laminations with a high concentration of heavy minerals (“black sand laminations”) were observed in three excavated trenches located on a washover terrace and fan on the east side of Fire Island. The mineralogical composition of these laminations reveals the presence of high quantities of magnetite, ilmenite (as opaque minerals), and garnet (as main translucent mineral). These heavy mineral enriched laminations were formed as waves eroded and transported sand from the primary dune and smaller relict dunes under specific hydrodynamic conditions that promoted grain sorting according to differences in size and specific gravity. Based on the concentrations of certain heavy minerals, the threshold for primarily density-driven sorting probably lies between the specific gravity of a less dense mineral (ilmenite, 4.7) and Garnet almandine (4.3), the most common transparent heavy mineral. The number of laminations and concentrations of heavy minerals vary between trenches on the overwash terrace and appear to be controlled by their distance from sediment sources. The trench with a greatest number of laminations and higher heavy mineral concentrations is located furthest from the main dune but is just 10 m inland of a relict dune that acts as the primary source of sediment of the washover deposit in this trench. A conceptual model for heavy mineral layer deposition is presented based on geomorphological and sedimentological evidences allowing the definition of a density threshold.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Selective sediment transport during Hurricane Sandy on Fire Island (New York, USA): Inferences from heavy-mineral assemblages
Series title Journal of Sedimentary Research
DOI 10.2110/jsr.2020.12
Volume 90
Issue 3
Year Published 2020
Language English
Publisher SEPM
Contributing office(s) Pacific Coastal and Marine Science Center
Description 17 p.
First page 269
Last page 285
Country United States
State New York
Other Geospatial Fire Island
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