Inner-shelf shoal formation through transgressive barrier submergence
Shore-parallel sand shoals are common depositional features on the continental shelves of North America and make up a significant component of the stratigraphic record generated by the Holocene transgression. Erosional shoreface retreat and in-place drowning of barrier shorelines are models that have been proposed to explain the generation of these deposits. Sand shoals within the retreat path of the Holocene Mississippi River delta plain were investigated using high-resolution seismic profiles and vibracores to determine their stratigraphic development and to test the models proposed for inner-shelf shoal formation. Ship Shoal is a shore-parallel sand body 50 km long with a relief of 3-5 m and is migrating landward 10-15 m/year in surrounding water depths of 7-15 m. The shoal lies disconformably over regressive deposits of the Maringouin delta, transgressed 6000 years ago. Reworked beach rock, Crassostrea sp. shell, and Rangia sp. shell, along with lagoonal mud, attest to the former existence of barrier shoreline environments. No in-situ barrier shorelined deposits were found within the shoal sand body. These data indicate Ship Shoal is a shelf sand body sourced from the erosion of a former barrier shoreline. Trinity Shoal is a landward migrating, shore parallel, lunate sand body associated with the abandoned Teche delta, transgressed about 3500 years ago. Lying in 7-10 m of water, with an inner shelf relief of 2-4 m, Trinity Shoal is a 5-7 thick sand body lying disconformably over regressive Teche delta deposits. Interpreted high-resolution seismic profiles identified the existence of tidal inlet channels within the shoal sand body, indicating Trinity Shoal is cored by in-situ deposits representing the platform of a former barrier shorelines.
- Research Organization:
- Louisiana Geological Survey, Baton Rouge
- OSTI ID:
- 5165457
- Report Number(s):
- CONF-860624-
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Vol. 70:5; Conference: American Association of Petroleum Geologists annual meeting, Atlanta, GA, USA, 15 Jun 1986
- Country of Publication:
- United States
- Language:
- English
Similar Records
Trinity shoal: a reworked deltaic barrier on Louisiana continental shelf
Sand shoal development on muddy Mississippi river delta shelf