AAPG Webinar w/ Dr. Mark Gordon: Cenozoic brittle deformation in the central Arabian plate скачать в хорошем качестве

AAPG Webinar w/ Dr. Mark Gordon: Cenozoic brittle deformation in the central Arabian plate

Dr. Mark Gordon, speaking on "Cenozoic brittle deformation in the central Arabian plate: Implications for the tectonics of the Middle East" Abstract: Jurassic to Eocene sedimentary rocks in central Arabia have been deformed by faulting and jointing. We measured these structures in the field. Paleostress directions from these data demonstrate that successive extensional events occurred. The most prevalent deformation in the central Arabian graben system is N-S tension associated with E-W normal faults. This deformation is most common in the region of the Nisah graben but is also seen in the northwest portion of the system where the principal faults have a northerly strike (Al Majma'ah region) and two regions (Khurais and Hawtah) that are relatively far from the well-mapped normal faults. Where chronology indicators are present, this phase is always the first phase. Its presence in the Eocene rocks at Khurais demonstrate that this event and all subsequent events occurred during the Eocene or later. The stress directions are generally about 010 and are well constrained by numerous faults. In the central portion of the graben system E-W normal faults with throws of 100 to 200 m were formed during this event and form a series of grabens such as the Nisah. A significant perturbation of the stress direction occurs in the northwest at the Wushayy site where the minimum principal stress direction is NNW. An E-W tension exists not only where the macro normal faults have a northerly strike, but also throughout the graben system and at Hawtah and Khurais. Thus, it is a regionally important event albeit not as pervasive as the N-S tension. Although most of the data is consistent with Phases I and II occurring simultaneously, it is possible that they are distinct phases. The joints associated with these phases have been interpreted as non-contemporaneous. In this case, the macro faults that form the Nisah and other E-W grabens would have had their major slip during Phase I whereas the macro faults in the Al Majma'ah region would have had their major slip during Phase II. The E-W tension at Khurais to the north and at Hawtah to the south shows that the E-W extension was regional. If the phases are considered non contemporaneous, the macro normal faults form in the Nisah region during Phase I and in the Al Majma'ah region during Phase II because the orientation of the basement faults was more favorable for larger slips to occur at the respective times. Bio: Mark B. Gordon graduated from the University of Texas at Austin with a PhD in Geological Sciences under William R. Muehlberger. He did postdoctoral research at the University of Paris 6 (now Sorbonne Université), with Jacques Angelier and Paul Hancock. He also did research at Rice University with Hans Avé Lallemant working on paleostress analysis in Honduras and at UT Austin with Paul Mann in Cuba. Since 1997 he has been working in the oil and gas industry with GX Technology, Repsol, Shell, PGS and BeicipFranlab Asia.