Sea-level oscillations, climatic variations, changes in bottom circulation, and vertical fluctuations of the carbonate compensation depth (CCD) were responsible for lithologic changes and major hiatuses. Depositional environments became more uniform across the margin after the late Campanian, and sedimentation was clearly influenced by more regional or global oceanographic events. Carbonaceous shales were recovered in Cenomanian strata of the deepest site (550) and in lower Turonian beds at sites of intermediate depth (549-551). The Eastern Boundary Current is an essential part of the water mass exchange between the subtropical and subpolar North Atlantic. Before the Campanian, variable depositional environments produced quite diverse sedimentary sequences in the isolated halfgrabens. Here, we study the offshore branch of the European Shelf Current (ESC) over the Goban Spur slope area off. Post-rift sedimentation started in the early Albian, and was accompanied by continuous regional subsidence. At the same time, the seaward edge of the continental crust appears to have been deeply intruded by oceanic tholeiites, forming an intermediate crust of transitional geophysical characteristics. This period was marked by the outpouring of pillows and flows of typical oceanic tholeiites, some of which were recovered at Site 550. (3) The post-rifting period began when ocean crust was accreted in a trough approximately 2000 m deep, beneath what is now the Porcupine Abyssal Plain. Volcanic rocks appear to be rare or absent in the syn-rift deposits on Goban Spur. ![]() Interpretation of seismic profiles indicates that (?)Aptian sequences also were deposited in the deeper half-grabens during this phase of rifting. Syn-rift deposition is recorded at Goban Spur by accumulation of a transgressive sequence of hyposaline to pelagic sediments, chiefly Barremian. (2) A terminal period of active rifting began approximately at the Jurassic/Cretaceous boundary (late Cimmerian phase), and was marked by a regional emergence. A second phase created northwesttrending listric, normal fault systems which delineated the pre-Atlantic rift system of the Early Cretaceous. From the late Paleozoic to the Triassic, a major phase was responsible for the development of northeast-trending grabens and horsts, which were especially active areas of deposition during the early and middle Mesozoic. The geologic history of Goban Spur and adjacent regions may be divided into three periods: (1) a pre-rift period, beginning at the end of the Hercynian orogeny, was marked by several phases of regional faulting. ![]() ![]() Drilling results have been integrated with physiographic, gravimetric, paleomagnetic, and seismostratigraphic data to provide a comprehensive interpretation of the geologic history of this sediment-starved passive margin. Microsoft® Word for Office 365 application/pdf Microsoft® Word for Office 365 uuid:8DEED6C0-1A05-4ED2-A882-7AD5F8A0878F uuid:579105d8-ca07-472c-9690-ff8207bdcf65Įndstreamendobj4161 0 objendobj4162 0 obj/DA(/MyriadPro-Regular 0 Tf 0 Tz 0 g)/F 132/FT/Sig/MK>/P 1 0 R/Rect/Subtype/Widget/T(Signature4)/Type/Annot/V 4163 0 R>endobj4163 0 obj/Filter/PubSec>/SubFilter/ on Leg 80 of the Deep Sea Drilling Project-International Phase of Ocean Drilling was conducted on a transect of four sites (548-551) across the continent-ocean boundary at Goban Spur, a prominent southwest-trending structural and topographic high on the Irish continental slope. Pp)/Rect/Subj(Typewritten Text)/Subtype/FreeText/T(annette.woodham)/Type/Annot>endobj4150 0 obj/DA(/MyriadPro-Regular 0 Tf 0 Tz 0 g)/F 132/FT/Sig/MK>/P 1 0 R/Rect/Subtype/Widget/T(Signature3)/Type/Annot/V 4151 0 R>endobj4151 0 obj/Filter/PubSec>/SubFilter//Type/Sig>endobj4152 0 obj>/Subtype/Form/Type/XObject>streamĮndstreamendobj4153 0 obj>/Subtype/Form/Type/XObject>streamĮndstreamendobj4154 0 obj/Subtype/Form/Type/XObject>streamĮndstreamendobj4155 0 obj/ProcSet>/Subtype/Form/Type/XObject>stream The missing link in the plate boundary between Eurasia and Africa in the central Atlantic is presented and discussed.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |