THE COPROLITES OF THE LOWER EAGLE FORD GROUP IN NORTH CENTRAL TEXAS

A new highly coprogenic locality is described in the lower Eagle Ford Group of North Central Texas. The age of the sediments is assigned to the upper Cenomanian based on planktonic foraminiferal data. The new locality has yielded a great abundance of well preserved bone-bearing coprolites. Many contain inclusions. They are attributed to large fish and/or sharks, on the basis of their morphology, size and inclusions, and also due to the fact that after coprolites, shark and other fish skeletal remains are the most abundant body fossils in this locality. Because of the abundance of coprolites, these outcrop strata are defined as “coprogenic sediments”. Coprolite horizons have a well known application in paleoecological reconstructions and a great potential in biostratigraphic correlation. Stratigraphically, the new locality represents an important section of the lower Eagle Ford Group: Britton Formation with tentatively identified Tarrant beds strata interfingering. The environment of deposition of this locality is interpreted as low-energy, offshore, poorly oxygenated environment. The thinly laminated sandy clay strata of this locality contain an abundant and very diverse pelagic ichthyofauna, rare benthic fauna, absence of infauna and a very rich coprolitic ichnofauna. The environment of deposition is consistent with the anoxic event recorded during the Cenomanian worldwide.