Atlantic Sediments, Erosion Rates, and the Evolution of the Continental Shelf: Some Speculations

Research Article| June 01, 1964 Atlantic Sediments, Erosion Rates, and the Evolution of the Continental Shelf: Some Speculations JAMES GILLULY JAMES GILLULY U. S. Geological Survey, Denver, Colo. Search for other works by this author on: GSW Google Scholar GSA Bulletin (1964) 75 (6): 483–492. https://doi.org/10.1130/0016-7606(1964)75[483:ASERAT]2.0.CO;2 Article history received: 09 Sep 1963 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation JAMES GILLULY; Atlantic Sediments, Erosion Rates, and the Evolution of the Continental Shelf: Some Speculations. GSA Bulletin 1964;; 75 (6): 483–492. doi: https://doi.org/10.1130/0016-7606(1964)75[483:ASERAT]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The volume of Triassic and younger sediment on and offshore from the Atlantic coast between Virginia and Nova Scotia can be estimated from the isopach map by Drake, Ewing, and Sutton (1959) of Atlantic coastal and offshore sediments. This volume is compared with that which would have been derived from the probable source area at present rates of erosion. It is found that the average rate of erosion in Triassic and later time was probably not less than three fourths and perhaps equal to the present rate.The arrangement of the sedimentary troughs identified by Drake, Ewing, and Sutton suggests that the Continental Shelf was formed in part by isostatic sinking of the offshore crust beneath the sedimentary load supplied by the rivers. But the presence of a nearly continuous median ridge in the sedimentary basin suggests that isostatic sinking is not alone responsible for the downwarp and in fact could not suffice to bring it about. The density of the sediment must be less than two thirds that of the subcrustal material displaced. If the basement had been originally horizontal or sloping uniformly seaward, the basin landward of the median ridge must have sunk by a mechanism other than isostatic depression beneath an additional 5000 feet of sediment, for the seafloor is roughly at the same depth over both ridge and inner basin. This differential depression of the basement, as well as the sinking of a former land area to form such basins, requires thinning of the crust; it is here suggested that subcrustal erosion by currents beneath the M discontinuity caused the thinning. Possibly the median ridge and the basins are due partly to instabilities produced by such currents, although they seem too large to be attributed to drag. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.