A paleoslope model of late Albian to early Turonian foraminifera of the western Atlantic Margin and North Atlantic basin

Abstract

A paleoslope model of Albian to Turonian benthic foraminifera reveals seven successive biofacies which are associated with increasing paleodepth. The paleoslope model indicates that the biofacies occupied inner neritic to abyssal environments of deposition (10 m to > 3500 m water depth). Biofacies 1 and 2 characterize paleodepths of less than 60 m. The biofacies contain abundant species of Epistomina and Gavelinella and exhibit a rapid stratigraphic alternation in response to local sea level change, which considerably aids in the identification of depositional sequences. Species of Globorotalites, Eggerellina and Neobulimina characterize biofacies 3 which principally occurs between 60 m and 130 m paleodepth. Biofacies 3 is the only biofacies to occur in both the New Jersey coastal plain and the Baltimore Canyon Trough. Biofacies 4 is composed of species of Gavelinella, Gyroidinoides and Valvulineria and is abundant in outer neritic to middle bathyal paleodepths of 130 m to 600 m. It is largely replaced by biofacies 5 during times of maximum flooding during sea level rise. A diverse assemblage of species of Lingulogavelinella and Lenticulina characterize biofacies 5. Paleodepths of 600 m to greater than 3500 m contain abundant species of Osangularia, Pleurostomella, Praebulimina, Pseudopatellinella and Quadrimorphina which define biofacies 6 and 7. In addition, four biofacies of much more limited distribution are recognized. Biofacies 1 ★ characterizes shallow-water, open marine paleoenvironments of the North Atlantic and is composed of spirillinids and species of Epistomina. Turonian dysaerobic environments are indicated by biofacies DSA and DSB which are composed mostly of agglutinated species. Dysaerobic environments expanded rapidly from middle bathyal to outer neritic depths in the early Turonian on the western Atlantic Margin. Biofacies DAA represents disturbed benthic environments and is dominated by species of Psammosphaera and Reophax. Biostratigraphy and species composition of the studied biofacies are similar to previously described European and South Atlantic assemblages. Major speciation events occur among the genera Gavelinella, Lingulogavelinella and Valvulineria. Well defined neritic and bathyal biofacies formed during a rapid late Albian species diversification concomitant with the first major Cretaceous flooding of continental margins.