ABSTRACT
Within the Arabian Peninsula, the Shu’aiba Formation is one of three Cretaceous carbonate formations in which rudist bivalves are an important component. The favourable hydrocarbon reservoir properties of these carbonates are primarily attributed to the presence of the rudists and their associated debris, which accumulated along the margins of an intra-shelf basin. The rudist banks caused differentiation of an earlier carbonate platform into lagoon, back-bank, bank, fore-bank and open marine environments. Understanding of the orientation of these banks has been significantly assisted by micropalaeontological analysis of the rudist-associated sediment, but may be additionally enhanced by the study of Recent large bivalves, such as the ‘fan mussel’ Pinna spp. The depositional geometries of the rudist-dominated facies of the Shu’aiba Formation may be better understood by studying the Great Pearl Bank Barrier, located on the southern flank of the Arabian Gulf, as this may present a Recent analogue for variations in sedimentation and bioclast distribution.
The Great Pearl Bank Barrier complex includes a submarine ridge that extends for approximately 200 kilometers between the Qatar Peninsula and Abu Dhabi, and lies in water depths of less than 8 meters, together with a deep lagoon and barrier flank facies. The submarine barrier complex and the back island lagoons consist primarily of bivalve shells, sands and mud, in which are embedded locally dense populations of the large bivalve species Pinna bicolor Gmelin and P.mururicata (Linnaeus). These forms may serve as Recent counterparts for the extinct Aptian constratal elevator rudists, such as Glossomyophorus costatus Masse, Skelton and Sliskovic, with a form that resembles Pachytraga sp., and Agriopleura blumenbachi that characterise the back-barrier and lagoonal facies, respectively, of the Shu’aiba Formation in the region. The oysters that have colonised the barrier crest have a clinging habit and may occupy a niche that equates with the Aptian recumbent rudist Offneria murgensis.
Genovesa Submarine Ridge: A manifestation of plume-ridge interaction in the northern Galápagos Islands