Chapter from:
AAPG Memoir 68:Regional and Petroleum Geology of the Black Sea and Surrounding Region, Edited by A.G. Robinson
AAPG Memoir 68: Regional and Petroleum Geology of the Black Sea and Surrounding Region. Chapter 10: Upper Jurassic-Cretaceous Planktonic Biofacies Succession and the Evolution of the Western Black Sea Basin , by Marius Dan Georgescu, Pages 169-182

Chapter 10
Upper Jurassic-Cretaceous Planktonic Biofacies Succession and the Evolution of the Western Black Sea Basin

Marius Dan Georgescu
PETROMAR
Constanta, Romania

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ABSTRACT

Three planktonic biofacies successions are recognized in the Upper Jurassic and Cretaceous in the Western Black Sea, offshore Romania. Biofacies A (Oxfordian-Valanginian) contains rare Globuligerina tests in punctual occurrences. The planktonic foraminifera are recorded in carbonate inner-shelf deposits in the Upper Jurassic, and mixed (detrital, clayey, marly) shelf deposits in the Berriasian-Valanginian. The first records of the Western Black Sea opening are dated as Valanginian. Biofacies B largely corresponds to the turbiditic interval of the late Albian-Cenomanian. The planktonic foraminiferal assemblages consist of both primitive (globular chambered) and morphologically advanced taxa (keeled Rotalipora and Praeglobotruncana). The planktonic record is discontinuous, but some claystone levels accumulated under calmer water environments (very low terrigenous input) show remarkable consistency. Biofacies C is peculiar to the outer-shelf deposits of Cenomanian through Maastrichtian age. A gradual increase of the recorded taxa and group diversity is evident. Planktonics are ubiquitous.