First shallow water scleractinian coral reef from the Danian, northern Patagonia, Argentina

BARON-SZABO, R. C.; CASADÍO, S.; PARRAS, A.

Santa Rosa, La Pampa

Jornada; Reunión Anual de Comunicaciones de la Asociación Paleontológica Argentina y Simposio de Tafonomía y Paleoecología; 2003

Asociación Paleontológica Argentina

Hermatypic coral reefs have not been reported from the earliest Paleocene with a few exceptions of unverified records (e.g. Paris Basin). On the other hand a zooxanthellate coral reefs from the early Paleocene of Greenland and Faxe, Denmark are well-documented. We describe the first Danian hermatypic coral reef from the Roca Formation at Lomita Baya, La Pampa, Argentina. The coral reef is primarily formed by the colonial Siderastrea adkinsi (Wells) and Haimesastraea conferta Vaughan, and is distinctly dominated by S. adkinsi (62%-88% in shallowest parts of the reef, 82%-100% in adjacent areas). In the shallowest parts of the reef colonies of S. adkinsi are massive-folios or encrusting, ranging between a few centimeters to over 1 m in diameter. Specimens of H. conferta are distinctly smaller, generally knobby, and range between a few millimeters and 15 centimeters in diameter. Frequently, corals of the "rolling stone type" occur which, in addition to the presence of folios-encrusting morphotypes and the microfacies images, indicate that the reef developed in a highly wave-agitated environment of 0-10 m depth. Sponges and coralline algae played an important role in the reef frame. Other members of the coral reef community are the branching coral Cladocora cf. C. gracilis (d´Orbigny), the solitary coral Sideroseris durhami Wells, the echinoid Micropsis desori (Cotteau), which was an inhabitant of hard substrates, the bivalves Acesta cf. A. latens (Feruglio), and Venericardia iheringi (Böhm), as well as several species of warm water gastropods