Crustal structure of the Faeroe--Shetland Channel
13
Citation
10
Reference
10
Related Paper
Citation Trend
Abstract:
The deep structure of the Faeroe—Shetland Channel has been investigated as part of the North Atlantic Seismic Project. Shot lines were fired along and across the axis of the Channel, with recording stations both at sea and on adjacent land areas. At 61°N, 1.7 km of Tertiary sediments overlies a 3.9–4.5 km s-1 basement interpreted as the top of early Tertiary volcanics. A main 6.0–6.6 km s-1 crustal refractor interpreted as old oceanic crust occurs at about 9 km depth. The Moho (8.0 ° 0.2 km s-1) is at about 15–17 km depth. There is evidence that Pn may be anisotropic beneath the Faeroe—Shetland Channel. Arrivals recorded at land stations show characteristics best explained by scattering at an intervening boundary which may be the continent—ocean crustal contact or the edge of the volcanics. The Moho delay times at the shot points, determined by time-term analysis, show considerable variation along the axis of the Channel. They correlate with the basement topography, and the greatest delays occur over the buried extension of the Faeroe Ridge at about 60° 15′N, where they are nearly 1 s more than the delays at 61°N after correction for the sediments. The large delays are attributed to thickening of the early Tertiary volcanic layer with isostatic downsagging of the underlying crust and uppermost mantle in response to the load, rather than to thickening of the main crustal layer. The new evidence is consistent with deeply buried oceanic crust beneath the Faeroe—Shetland Channel, forming a northern extension of Rockall Trough. The seabed morphology has been grossly modified by the thick and laterally variable pile of early Tertiary volcanic rocks which swamped the region, accounting for the anomalous shallow bathymetry, the transverse ridges and the present narrowness of the Channel.Keywords:
Shetland
Basement
Five deep crustal holes were drilled into the Mid‐Atlantic Ridge near 37°N by Glomar Challenger on Leg 37 of the Deep Sea Drilling Project. The drilling results and laboratory measurements of seismic velocity on samples from one hole of over 500 m into basement have shown that the low velocity upper crustal layer 2a consists of interlayered solid basalt and shattered and fractured volcanic material with extensive large scale porosity and voids and some intercalated sediments. Gabbros and serpentinites with velocity appropriate for the lower crust were recovered from another hole.
Basement
Mid-Atlantic Ridge
Seismic velocity
Cite
Citations (23)
Lineation
Seafloor Spreading
Basement
Oceanic basin
Cite
Citations (12)
Research Article| April 01, 1974 Oceanic Crust Forms Basement of Eastern Panamá J. E. CASE J. E. CASE 1U.S. Geological Survey, P. O. Box 6732, Corpus Christi, Texas 78411 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1974) 85 (4): 645–652. https://doi.org/10.1130/0016-7606(1974)85<645:OCFBOE>2.0.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation J. E. CASE; Oceanic Crust Forms Basement of Eastern Panamá. GSA Bulletin 1974;; 85 (4): 645–652. doi: https://doi.org/10.1130/0016-7606(1974)85<645:OCFBOE>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 Basement rocks of parts of eastern Panamá include tholeiitic pillow basalt and diabase overlain by sedimentary rocks typical of deep oceanic environments. Both paleontologic and stratigraphic evidence indicate that some of these rocks are of Late Cretaceous age or older. Regional Bouguer anomalies over the basement terrane exceed +120 mgal, indicating that eastern Panamá is a raised block of oceanic crust. Age relations in the Caribbean region apparently preclude an "Atlantic" or single intra-Caribbean origin for eastern Panamá and the southern Caribbean basin, but multiple intra-Caribbean origins of the basaltic basement rocks are permitted by the age data. An in situ origin of the oceanic basement of Panamá at a position which later became a Cenozoic island arc is likewise consistent with the available geologic and geophysical data.Seismic horizon B″ in the Caribbean is correlative with or overlain by deep-sea sedimentary rocks of Coniacian to Campanian age. This horizon forms the top of the apparent basement of eastern Panamá and, thus, the eastern isthmus is a horstlike block that has been elevated or obducted a minimum of 6 km since Coniacian-Maastrichtian time, partly caused by northeastward underflow of the Pacific plate but possibly related to southwestward movement of the Caribbean plate beneath the isthmus. 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.
Basement
Panama
Pillow lava
Icon
Cite
Citations (74)
Basement
Cite
Citations (5)
Magma chamber
Hotspot (geology)
Cite
Citations (115)
Epicenter
Cite
Citations (6)
Seafloor Spreading
Mid-Atlantic Ridge
Cite
Citations (4)
Thrust fault
Focal mechanism
Cite
Citations (42)
New data from a region at 4° S on the Mid-Atlantic Ridge, in association with our studies of four other transform faults at 43° N, 9° N, 01° N, and 00° N, and with other workers' reported results, indicate exposure of a wide variety of rock types in fracture zones in the Atlantic Ocean. Rock types include extrusive and intrusive basic rocks as well as plutonic ultrabasic intrusions. Our findings suggest that new oceanic crust, both eruptive and plutonic, is being injected into transform faults. This new crust appears to have different petrologic and chemical characteristics from that formed during sea-floor spreading at normal ridge crests, and forms in response to sea-floor spreading in a direction normal to that which occurs at the ridge crest.
Fracture zone
Seabed
Ultramafic rock
Extrusive
Crest
Mid-Atlantic Ridge
Basement
Transform fault
Cite
Citations (122)