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

Schwab, William C.; Baldwin, Wayne E.; Denny, Jane F.; Hapke, Cheryl J.; Gayes, P. T.; List, Jeffrey H.; Warner, John C.

doi:10.1016/j.margeo.2014.06.011

Cited by 47 publications

(38 citation statements)

References 62 publications

(92 reference statements)

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“…2). A more thorough review of the regional geologic framework and coastal evolution of the Fire Island study area, including major inner continental shelf sedimentary sequences, sediment distribution, and shelf morphology, is presented in Schwab et al, (2000aSchwab et al, ( , 2013Schwab et al, ( , 2014b, and briefly summarized below.…”

Section: Geologic Settingmentioning

confidence: 99%

“…In the central part of the region in water depths greater than~18 m, the eroded remnants of an outwash lobe are identified as a high-backscatter gravelly lag deposit ( Fig. 2; Schwab et al, 2014b). Schwab et al (2013) inferred that erosion of this headland during Holocene marine transgression yielded an abundant volume of very fine-to medium-grained sand, a primary source of sediment for the development of the shoreface-connected sand ridges offshore of western Fire Island.…”

Section: Geologic Settingmentioning

confidence: 99%

“…The USGS has long been involved in research in the New York inner-continental shelf starting in 1996 with the objectives of evaluating the influence of the regional geologic framework on coastal evolution, and formulating a conceptual model of sediment flux in the coastal ocean (Schwab et al, 2000a. In May of 2011, the USGS conducted a high-resolution marine geophysical survey of the lower shoreface and inner continental shelf offshore of Fire Island using interferometric sonar and seismicreflection techniques (Schwab et al, 2014b). Ultimately, this survey served to document conditions on the Fire Island inner continental shelf prior to the passage of Hurricanes Irene (Aug. 2011) and Sandy (Oct. 2012).…”

Section: Introductionmentioning

confidence: 99%

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Inner-shelf ocean dynamics and seafloor morphologic changes during Hurricane Sandy

Warner

Schwab

List

et al. 2017

Continental Shelf Research

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A B S T R A C THurricane Sandy was one of the most destructive hurricanes in US history, making landfall on the New Jersey coast on October 30, 2012. Storm impacts included several barrier island breaches, massive coastal erosion, and flooding. While changes to the subaerial landscape are relatively easily observed, storm-induced changes to the adjacent shoreface and inner continental shelf are more difficult to evaluate. These regions provide a framework for the coastal zone, are important for navigation, aggregate resources, marine ecosystems, and coastal evolution. Here we provide unprecedented perspective regarding regional inner continental shelf sediment dynamics based on both observations and numerical modeling over time scales associated with these types of large storm events. Oceanographic conditions and seafloor morphologic changes are evaluated using both a coupled atmospheric-ocean-wave-sediment numerical modeling system that covered spatial scales ranging from the entire US east coast (1000 s of km) to local domains (10 s of km). Additionally, the modeled response for the region offshore of Fire Island, NY was compared to observational analysis from a series of geologic surveys from that location. The geologic investigations conducted in 2011 and 2014 revealed lateral movement of sedimentary structures of distances up to 450 m and in water depths up to 30 m, and vertical changes in sediment thickness greater than 1 m in some locations. The modeling investigations utilize a system with grid refinement designed to simulate oceanographic conditions with progressively increasing resolutions for the entire US East Coast (5-km grid), the New York Bight (700-m grid), and offshore of Fire Island, NY (100-m grid), allowing larger scale dynamics to drive smaller scale coastal changes. Model results in the New York Bight identify maximum storm surge of up to 3 m, surface currents on the order of 2 ms −1 along the New Jersey coast, waves up to 8 m in height, and bottom stresses exceeding 10 Pa. Flow down the Hudson Shelf Valley is shown to result in convergent sediment transport and deposition along its axis. Modeled sediment redistribution along Fire Island showed erosion across the crests of inner shelf sand ridges and sedimentation in adjacent troughs, consistent with the geologic observations.

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Section: Geologic Settingmentioning

confidence: 99%

Section: Geologic Settingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Inner-shelf ocean dynamics and seafloor morphologic changes during Hurricane Sandy

Warner

Schwab

List

et al. 2017

Continental Shelf Research

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“…The RIS features, however, contain symmetrical ripples with ENE to ESE oriented crestlines that parallel the direction of depression elongation, suggesting that they are wave-orbital ripples produced by waves propagating from the south (Murray and Thieler 2004;Clifton 2006). Sorted bedforms described off North Carolina (Murray and Thieler 2004), Massachusetts (Goff et al 2005), and New York (Schwab et al 2014) have been attributed to enhanced sediment entrainment due to wave interaction with the seabed and bottom roughness elements, and to transverse longshore flow. While wave interaction with bottom roughness elements clearly plays a role in the maintenance of the RIS features, strong sound-wide transverse flows are likely provided by wind-driven currents associated with storms approaching from the south (Ullman and Codiga 2010).…”

Section: Discussionmentioning

confidence: 99%

“…Observational and modeling studies in Rhode Island Sound (RIS) have reported that storm waves there can exceed threshold friction velocities, facilitating resuspension (e.g., First 1972;Boehm and Quinn 1978;Dalyander et al 2013). Other work has described complex features that transect the shoreface and inner shelf, and consist of shallow, elongate depressions containing rippled sand and gravel off the U.S. east (e.g., Murray and Thieler 2004;Goff et al 2005;Oakley et al 2009;Schwab et al 2014) and west (e.g., Cacchione et al 1984;Ferrini and Flood 2005;Davis et al 2013) coasts and globally (Trembanis and Hume 2011, and references therein). These features have been variously called rippled scour depressions, sorted bedforms, and cross-shore swaths.…”

Section: Introductionmentioning

confidence: 99%

Character, distribution, and ecological significance of storm wave-induced scour in Rhode Island Sound, USA

2014

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Multibeam bathymetry, collected during NOAA hydrographic surveys in 2008 and 2009, is coupled with USGS data from sampling and photographic stations to map the seabed morphology and composition of Rhode Island Sound along the US Atlantic coast, and to provide information on sediment transport and benthic habitats. Patchworks of scour depressions cover large areas on seaward-facing slopes and bathymetric highs in the sound. These depressions average 0.5-0.8 m deep and occur in water depths reaching as much as 42 m. They have relatively steep well-defined sides and coarser-grained floors, and vary strongly in shape, size, and configuration. Some individual scour depressions have apparently expanded to combine with adjacent depressions, forming larger eroded areas that commonly contain outliers of the original seafloor sediments. Where cobbles and scattered boulders are present on the depression floors, the muddy Holocene sands have been completely removed and the winnowed relict Pleistocene deposits exposed. Low tidalcurrent velocities and the lack of obstacle marks suggest that bidirectional tidal currents alone are not capable of forming these features. These depressions are formed and maintained under high-energy shelf conditions owing to repetitive cyclic loading imposed by high-amplitude, long-period, stormdriven waves that reduce the effective shear strength of the sediment, cause resuspension, and expose the suspended sediments to erosion by wind-driven and tidal currents. Because epifauna dominate on gravel floors of the depressions and infauna are prevalent in the finer-grained Holocene deposits, it is concluded that the resultant close juxtaposition of silty sand-, sand-, and gravel-dependent communities promotes regional faunal complexity. These findings expand on earlier interpretations, documenting how storm wave-induced scour produces sorted bedforms that control much of the benthic geologic and biologic diversity in Rhode Island Sound.

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Persistent Shoreline Shape Induced From Offshore Geologic Framework: Effects of Shoreface Connected Ridges

et al. 2017

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Mechanisms relating offshore geologic framework to shoreline evolution are determined through geologic investigations, oceanographic deployments, and numerical modeling. Analysis of shoreline positions from the past 50 years along Fire Island, New York, a 50 km long barrier island, demonstrates a persistent undulating shape along the western half of the island. The shelf offshore of these persistent undulations is characterized with shoreface‐connected sand ridges (SFCR) of a similar alongshore length scale, leading to a hypothesis that the ridges control the shoreline shape through the modification of flow. To evaluate this, a hydrodynamic model was configured to start with the US East Coast and scale down to resolve the Fire Island nearshore. The model was validated using observations along western Fire Island and buoy data, and used to compute waves, currents and sediment fluxes. To isolate the influence of the SFCR on the generation of the persistent shoreline shape, simulations were performed with a linearized nearshore bathymetry to remove alongshore transport gradients associated with shoreline shape. The model accurately predicts the scale and variation of the alongshore transport that would generate the persistent shoreline undulations. In one location, however, the ridge crest connects to the nearshore and leads to an offshore‐directed transport that produces a difference in the shoreline shape. This qualitatively supports the hypothesized effect of cross‐shore fluxes on coastal evolution. Alongshore flows in the nearshore during a representative storm are driven by wave breaking, vortex force, advection and pressure gradient, all of which are affected by the SFCR.

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

Cited by 47 publications

References 62 publications

Inner-shelf ocean dynamics and seafloor morphologic changes during Hurricane Sandy

Inner-shelf ocean dynamics and seafloor morphologic changes during Hurricane Sandy

Character, distribution, and ecological significance of storm wave-induced scour in Rhode Island Sound, USA

Persistent Shoreline Shape Induced From Offshore Geologic Framework: Effects of Shoreface Connected Ridges

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