A sequence stratigraphic framework for the Upper Callovian-Lower Valanginian of the Arabian Plate
Multidisciplinary analysis of 10 newly-designated sequence stratigraphic reference sections has led to the recognition of 14 candidate bounding surfaces in the Upper Callovian - Lower Valanginian of the Arabian Plate. The spinosum Subzone, upper Remane Zone-B and late Early Valanginian bounding surfaces define two megasequences, within which 3rd Order depositional sequences can be identified and locally correlated. Across the Arabian platform most 3rd Order sequences comprise transgressive-regressive couplets bounded by Type I disconformities. Lowstand deposits are confined to relatively minor lowstand wedges, incised valley-fills and secondary condensed sections. Platform aggradation:progradation ratios are in the order of 1:4, reflecting limited on-shelf accommodation and prolific highstand shedding. The interplay between 2nd and 3rd Order sealevel changes has had a profound impact on sequence architecture. 3rd Order sequences deposited during 2nd Order sealevel rise are characterised by enhanced transgressive systems tracts (TST), well-developed MFS's and starved highstand systems tracts (HST); the associated lowstand systems tracts (LST) are represented by cryptic non-karstified palaeoexposure surfaces across the interfluves, lowstand wedges along the flanks of intra-shelf depressions and secondary condensed sections along the former platform slope. In contrast, 3rd Order sequences deposited during 2nd Order sealevel fall have starved TST's, subdued MFS's and enhanced TST's; the associated LST's are represented by mature paleokarsts across the interfluves, and major incised valley-fills along the former shelf break. MFS's have been dated using ammonites, capionellids and calcareous dinocysts. These datums have been used to constrain the age of genetic sequences and their associated (benthic) biotas. This has resulted in revised stratigraphic ranges for several key taxa.