A MARINE FAUNAL ASSEMBLAGE FROM THE JURASSIC (CALLOVIAN) ETHIOPIAN PROVINCE OF SOUTHERN ISRAEL

The 100 m thick Upper Callovian Matmor Formation in Hamakhtesh Hagadol (Kurnub Anticline), a 15 km long and 6 km wide erosional feature in southern Israel, consists of a package of Jurassic sediments divided into a lower (30 m; subunits 43-52) and upper (70 m; subunits 53-74) sequence. The lower sequence is composed of alternating fossiliferous limestones and marls, correlative with Hudson’s (1958) Somalirhynchia-Putealiceras beds of Late Callovian age, and is assigned to the Peltoceras athleta-Quenstedtoceras (Lamberticeras) lamberti Zone. Beds of fossiliferous limestones yield brachiopods, bivalves, gastropods, echinoderms and ammonites. A faunal assemblage found in this sequence is dominated by the terebratulid brachiopods Digonella and Apatecosia with other faunal constituents including: Ceratomyopsis, Protocardia, Bucardiomya, Parallelodon (bivalves), Rhabdoconcha, Eunerinea (gastropods), Millericrinus, Apiocrinites (echinoderms), and the ammonites Pachyceras, Sowerbyceras, and Lunuloceras. The diverse and rich faunal composition indicates a well-oxygenated normal marine environment at trophic equilibrium. This assemblage is dominated by one trophic group whereas the next most dominant taxon belongs to another trophic group, as is the case with Turpaeva’s (1957) Recent Arctic and Boreal communities. Niche partitioning within the assemblage results in noncompetitive feeding and thus provides a measure of stability. The environment of deposition of these brachiopod-dominated biomicrites was a low energy shallow epeiric sea, largely subtidal with some interbedded marine shales indicative of an influx of mud from rivers that drained adjacent landmasses.