A Sequence Stratigraphic, Geochronological and Chemostratigraphic Investigation of the Ediacaran Antaq Basin, Eastern Arabian Shield

SGS-TR-2010-5 David Nettle
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ABSTRACT


The Antaq Basin is one of a number of late Neoproterozoic volcano-sedimentary basins that overlie the amalgamated arc terranes of the Arabian-Nubian Shield. It is part of the Ediacaran aged Jibalah Group, a series of volcano-sedimentary successions that infill small fault-controlled grabens and pull-apart basins formed by phases of intracontinental extension related to Najd faulting. The Antaq Basin was deposited during the late Neoproterozoic, a period that involved the final amalgamation of Gondwana, a rapidly changing environment and the first appearance of multicellulat life. Previously it has been unclear whether the Antaq Basin is of marine or lacustrine origin. However this study concludes that the Antaq Basin succession was deposited in a marginal marine setting. This is supported by sequence stratigraphy, the presence of Ediacaran fossils and microbial mats, and the correlation of Antaq Basin carbonates with the 13C record of Neoproterozoic oceans. Chemostratigraphy of the Antaq Basin records a positive shift in 13Ccarb from -6‰ to 0‰, interpreted to represent the end of the Shuram-Wonoka anomaly, Earth’s largest negative marine 13Ccarb excursion. U-Pb zircon geochronology has placed a maximum depositional age of 570 Ma on the basin, confirming its Ediacaran age, and placing an upper constraint on the termination of the Shuram-Wonoka anomaly. A number of authors have proposed correlation between the Jibalah Group and the Nafun Group (Huqf Supergroup, Oman). However, the study has provided no reason to correlate the environmentally distinct Nafun and Jibalah Groups. Collins et al (2009) describe a preferred model where the Nafun Group lies on a passive continental margin of India and the Jibalah Group lies on a coeval, ~570 Ma, active margin of the Saharan Craton. The study also presents two Ediacaran body fossils, some of the first discovered from the Arabian Shield.

 

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Nettle, D., 2011, A sequence stratigraphic, geochronological and chemostratigraphic investigation of the Ediacaran Antaq Basin, Eastern Arabian Shield: Saudi Geological Survey Technical Report SGS-TR-2010-5, 83 p., 20 figs., 5 tables.