Holocene reworking of a sand sheet in the Merrimack Embayment, Western Gulf of Maine

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Abstract

Recent bathymetric, backscatter, and seafloor sediment samples demonstrate that a large sand sheet was formed in the inner shelf by the reworking of the Merrimack River lowstand delta (deposited 12 kya; currently at 45 m depth) and braid plain during the Holocene transgression. Asymmetric bedforms and distinct grain size distributions suggest the sand sheet is actively being reworked by inner-shelf processes.

Bottom sediments range from silty sand at the submerged delta to coarse sand and fine gravel in the innermost shelf (depth: 10-50 m). Coarse-grained sand comprises an expansive (32 km2 ) featureless sand sheet centered off the Merrimack River. Fine-grained sand discontinuously overlies this sand sheet in many locations and forms long wavelength (100 – 800 m), low amplitude (1-2 m), asymmetrical bedforms. Sets of these bedforms are oriented from slightly oblique offshore to onshore; several bedform sets are located within 1 km and oriented orthogonally to one another. Along the paleo-delta front north-northwest oriented bedforms are dominant. Inshore of these features, the bedforms become more closely spaced and have orientations to the west and westsouthwest. Preliminary data suggest that the combined forcings of instantaneous storm-wave generated shear stress and storm-induced currents associated with high energy northeast storm events may be responsible for sand sheet reworking and bedform development.

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Additional publication details

Publication type Conference Paper
Publication Subtype Conference Paper
Title Holocene reworking of a sand sheet in the Merrimack Embayment, Western Gulf of Maine
Year Published 2007
Language English
Publisher Coastal Education and Research Foundation
Contributing office(s) Woods Hole Coastal and Marine Science Center
Description 5 p.
Larger Work Type Conference Paper
Larger Work Subtype Conference Paper
Larger Work Title ICS2007 Proceedings
Conference Title The International Coastal Symposium
Conference Location Australia
Conference Date 2007
Country United States
State Maine
Other Geospatial Gulf of Maine, Merrimack River