Deposition, age and Pan-Arabian correlation of late Neoproterozoic outcrops in Saudi Arabia

Ongoing field mapping and sample analyses of late Neoproterozoic outcrops in Saudi Arabia has provided insight into the deposition and correlation of these strata across the Arabian Plate. Outcrops of the Jibalah Group display the same three-fold internal stratigraphy regionally across the Arabian Shield, indicating deposition within a single, laterally continuous basin that evolved from proximal fluvial conditions at its base, to a marine shelf setting at the top. Furthermore, distal marine limestones of the Muraykah Formation appear directly correlatable across the Arabian Plate with the Khufai Formation of Oman based on similarity of facies, relative stratigraphical position, carbon-isotope stratigraphy and age dating. SHRIMP analyses of zircons from tuff beds within the Muraykah Formation have yielded robust U-Pb ages of 588–600 Ma. The newly identified Kurayshah Group in northwest Saudi Arabia comprises a sequence of terminal Neoproterozoic fluvial clastics and basalts that unconformably overlie the Jibalah Group. In one location, basal Kurayshah conglomerates contain sandstone lasts from the underlying Muraykah Formation. Field relationships also indicate that Kurayshah outcrops are older than the pan-Arabian, basal Cambrian unconformity of c. 540–520 Ma. The Kurayshah Group most likely represents backarc sedimentation and volcanism associated with the final stages of Arabian Shield terrane assembly during the late Neoproterozoic. A distinct sequence of post-depositional structural events is regionally mappable within the Jibalah Group in northwest Saudi Arabia, beginning with an initial phase of mild transpression and folding, followed by a major extensional collapse and culminating with Najdtrending shearing, folding and uplift. A final, terminal Neoproterozoic phase of Najd shearing and transtension preserved both the Jibalah and Kurayshah outcrops in small pull-apart grabens on the Arabian Shield, prior to the pan-Arabian, Early Cambrian uplift and peneplanation of c. 540–520 Ma.