Geologic Evidence for Onshore Sediment Transport from the Inner Continental Shelf: Fire Island, New York

Modification of the Quaternary stratigraphic framework of the inner-continental shelf by Holocene marine transgression: An example offshore of Fire Island, New York

“…The relatively sparse seismic-reflection data coverage results in a surface that clearly contains trackline artifacts and a relatively higher uncertainty in comparison with other maps presented. change can be significantly influenced by the antecedent geology being eroded and the availability of nearshore transgressive sand deposits (Riggs et al, 1995;Thieler et al, 1995;Schwab et al, 2000aSchwab et al, , 2013Gayes et al, 2003;Miselis and McNinch, 2006;Hapke et al, 2011;Denny et al, 2013;Twichell et al, 2013). The analysis of the lower shoreface and inner-continental shelf bathymetry, sediment distribution, bedform patterns, and seismostratigraphy presented here supports previous hypotheses and references therein) that: (A) erosion of the Pleistocene glaciofluvial and early Holocene channelfill sediment deposits offshore of Fire Island during Holocene marine transgression formed the present morphology of the inner-continental shelf and sediment distribution patterns; and (B) processes associated with ongoing marine transgression and formation of a ravinement surface yield a relatively finer grained modern sand deposit that is transported in a net westerly direction.…”

“…In other innercontinental shelf settings where sorted bedforms have been mapped in high resolution, they tend to be asymmetric with their relatively coarser flanks facing up current, opposite to the direction of dominant sediment transport (Murray and Thieler, 2004;Goff et al, 2005 and references therein). Thus, Schwab et al (2013) interpreted the relatively higher-backscatter base and eastward-facing flanks of the sorted bedform troughs offshore of eastern Fire Island (Fig. 8A) to be indicative of continued erosion of the seabed by oceanographic processes and net westward transport direction of reworked sediment.…”

“…The evolution of coastal areas, from individual storm events to millennial time scales, is linked directly to the oceanographic processes acting on the geologic framework of the adjacent inner-continental shelf (Swift, 1976;Riggs et al, 1995;Thieler et al, 1995Thieler et al, , 2001Wright, 1995;Schwab et al, 2000aSchwab et al, , 2013Cowell et al, 2003;Miselis and McNinch, 2006;Fagherazzi and Overeem, 2007;Denny et al, 2013;Twichell et al, 2013). Fire Island, a segment of a barrier island system extending along the south coast of Long Island, New York ( Fig.…”

“…Mitigating the impacts of coastal erosion has been an important management objective for decades. Thus, coastal erosion and sediment budget analyses in the Fire Island barrier-island system have been conducted and debated in the scientific and engineering literature (e.g., Gofseyeff, 1952;Saville, 1960;Panuzio, 1968;Kumar and Saunders, 1974;Williams, 1976;Leatherman and Allen, 1985;Kana, 1995;Morang et al, 1999;Smith et al, 1999;Schwab et al, 2000aSchwab et al, , 2013Hapke et al, 2010). It is well documented that a primary Marine Geology 355 (2014) [346][347][348][349][350][351][352][353][354][355][356][357][358][359][360] component of sediment transport in this system is directed alongshore from east to west, but discrepancies in volumetric sediment budget calculations remain (see Hapke et al, 2010 and references therein).…”

“…Thus, in this paper, the geomorphic expression of the Fire Island shoreface is not meant to imply the width of a nearshore zone of active sediment transport nor the seaward limit of processes forming a ravinement surface. Schwab et al (2013) used high-resolution seafloor mapping techniques and historical shoreline analyses to investigate how the geologic framework of the inner-continental shelf influenced the Holocene evolution and modern behavior of Fire Island. Their findings suggested that a realistic coastal sediment budget must include sediment input from the inner-continental shelf.…”