Sedimentation and echo characteristics in the abyssal hills of the west-central North Atlantic

Abstract

Research Article| March 01, 1978 Sedimentation and echo characteristics in the abyssal hills of the west-central North Atlantic THOMAS H. SHIPLEY THOMAS H. SHIPLEY 1Geophysics Laboratory, Marine Science Institute, University of Texas, Galveston, Texas 77550 Search for other works by this author on: GSW Google Scholar Author and Article Information THOMAS H. SHIPLEY 1Geophysics Laboratory, Marine Science Institute, University of Texas, Galveston, Texas 77550 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1978) 89 (3): 397–408. https://doi.org/10.1130/0016-7606(1978)89<397:SAECIT>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation THOMAS H. SHIPLEY; Sedimentation and echo characteristics in the abyssal hills of the west-central North Atlantic. GSA Bulletin 1978;; 89 (3): 397–408. doi: https://doi.org/10.1130/0016-7606(1978)89<397:SAECIT>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 abyssal hills province of the western North Atlantic 600 km southeast of Bermuda contains irregular hills and basins 10 to 20 km wide, with about 400 m of relief probably generated by ridge-flank volcanism and faulting. Conical(?) abyssal hills 5 to 10 km wide with about 300 m of relief are thought to represent a later stage of midplate volcanism, perhaps related to the post-Eocene uplift of the Bermuda Rise.The 3.5-kHz echo characteristics of the surficial sediments were combined with piston core data to produce a geologic map with six main units. Pelagic brown-clay sedimentation has been fairly constant at 1 to 3 m/m.y. since mid-Cretaceous time. In some of the high areas and on the Bermuda Rise at depths less than 5,500 m, a 30-m opaque unit records carbonate sedimentation that began sometime in Pliocene time with lowering of the calcium carbonate compensation depth. Three distinct echo characters are observed from the various stratified sediment bodies. One is owing to near-outcrop of a deep reflector unit. Another unit is composed of discrete, closely spaced reflectors of the Nares Abyssal Plain and parts of the southern fracture valley. A third unit contains widely spaced (20 m) reflectors restricted to the more northerly fracture valley and certain cross valleys. The stratified sediments in both the Nares Abyssal Plain and the fracture valleys consist of brown clays at the surface and gray clays at depth. The gray clays are interpreted as distal turbidites, having 12% more silt than the pelagic brown clays and always occurring in water depths greater than 5,700 m. The turbidity currents crossed the Nares Abyssal Plain into the southern valley and over low sills into the northerly fracture valley. The veneer of brown clay indicates that turbidity currents probably have not been active in this area for at least 300,000 yr. 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.