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Geologic Framework and Holocene Sand Thickness Offshore of Seven Mile Island, New Jersey

Scientific Investigations Report 2024-5131
Coastal/Marine Hazards and Resources Program
Prepared in cooperation with the National Fish and Wildlife Foundation
By: , , , and 
https://doi.org/10.3133/sir20245131

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Abstract

The U.S. Geological Survey assessed the Quaternary evolution of Seven Mile Island, New Jersey, to quantify coastal sediment availability, which is crucial for establishing sediment budgets, understanding sediment dispersal, and managing coastlines. This report presents preliminary interpretations of seismic profiles, maps of Holocene sand thickness from the shoreline to 2 kilometers offshore, and tables quantifying the volume of available sediment along the coastal margin based on data collected during 2021 and 2022. The results reveal spatial variability in the thickness and cross-shore extent of Holocene sand. The study area was separated into northern, central, and southern zones by using underlying stratigraphy and geomorphic features. The characteristics and spatial extent of the Holocene sand deposit indicate that hydrodynamic processes contribute to its spatial variability. Northern Seven Mile Island contains the thickest deposits of Holocene sand that were formed by sediment bypass around the Townsends Inlet ebb-tidal delta. Specifically, swash bars have welded to the updrift end of Seven Mile Island and have formed thick deposits of Holocene sand that thicken landward and taper seaward. Despite their thickness, these deposits have the smallest cross-shore extent; therefore, northern Seven Mile Island has the smallest volume of Holocene sand of the three geomorphic zones. Central Seven Mile Island has the thinnest Holocene sand deposits because this section of the barrier island is outside the influence of ebb-tidal deltas. Southern Seven Mile Island has the greatest volumes of Holocene sand because of increased accommodation and deposition adjacent to the Hereford Inlet ebb-tidal delta. Even though tidal inlets exert variable influence on the three geomorphic zones, sediment is distributed fairly uniformly within each geomorphic zone; each of the three zones contains 31.05–36.48 percent of the volume of available Holocene sand.

Suggested Citation

Wei, E.A., Miselis, J.L., Buster, N.A., and Forde, A.S., 2025, Geologic framework and Holocene sand thickness offshore of Seven Mile Island, New Jersey: U.S. Geological Survey Scientific Investigations Report 2024–5131, 19 p., https://doi.org/10.3133/sir20245131.

ISSN: 2328-0328 (online)

Study Area

Table of Contents

  • Acknowledgments
  • Abstract
  • Introduction
  • Regional Geologic Setting
  • Materials and Methods
  • Results
  • Discussion
  • Summary
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Geologic framework and Holocene sand thickness offshore of Seven Mile Island, New Jersey
Series title Scientific Investigations Report
Series number 2024-5131
DOI 10.3133/sir20245131
Publication Date March 14, 2025
Year Published 2025
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) St. Petersburg Coastal and Marine Science Center
Description Report: viii, 19 p.; 2 Data Releases
Country United States
State New Jersey
Other Geospatial Seven Mile Island
Online Only (Y/N) Y
Additional publication details