2002 Denver Annual Meeting (October 27-30, 2002)

Paper No. 9
Presentation Time: 8:00 AM-12:00 PM


GRABOWSKI Jr, George1, SULLIVAN, Michael A.1, STERITZ, John W.2, FERDERER, Robert J.2 and CREANEY, Stephen2, (1)ExxonMobil Exploration Company, 233 Benmar Drive, Houston, TX 77060, (2)ExxonMobil Exploration Co, 233 Benmar Drive, Houston, TX 77060, george.grabowski@exxonmobil.com

Across North Africa and Arabia, the "Hercynian" unconformity is diachronous. In Algeria and westernmost Libya, the main unconformity is early Permian (Sakmarian) and overlies Autunian-Stephanian clastic sediments. In eastern Libya and Egypt, two discrete unconformities exist of early Permian and late Carboniferous age. In Arabia, Westphalian to Artinskian clastic sediments of the Haushi and Unayzah Formations unconformably overlie Carboniferous and older strata. This general younging of uplift and erosion to the east is inconsistent with the well-constrained timing of Hercynian compressional deformation in Europe and northwestern Africa.

Deformational intensity and style also diminishes across the region, with the Trans-Saharan Fault Zone (TSFZ), defining a critical strain partition boundary. To the west of the TSFZ, fold and thrust belt deformation typical of orogenic forelands is observed, whereas to the east in Libya and Egypt, gentle folding and warping is the dominant style.

Paleozoic facies patterns in North Egypt also illustrate progressive uplift, beginning in the Ordovician and culminating in late Carboniferous. It is this uplift, and not far-field "Hercynian" compression that is responsible for unconformities in eastern North Africa and westernmost Arabia. One potential driving mechanism behind this uplift is the progressive development of the long-lived alkaline magmatic provinces of eastern Egypt and northern Sudan. This uplift may also have been an early abortive attempt at rifting in this location. In Arabia, the Central Arabian arch appears compressional in nature and may have resulted from orogenic deformation along the pre-break-up northern margin of Arabia (Present day Iran).