SYLVESTER, ZOLTAN
Stanford University, CA

Abstract: Facies Architecture of a Mud-Sand Rich Turbidite System: The Eocene Upper Tarcau Sandstone, East Carpathians, Romania

A 15 km long outcrop belt in the Buzau Valley (East Carpathians, Romania), provide an opportunity to study facies and architecture of a mud-sand rich turbidite system, which was deposited in a remnant basin with an abundant sediment supply from adjacent uplifted suture zones. Individual sedimentation units (second-order elements) of the Tarcau Sandstone range from fine grained turbidites, through T_bcde turbidites, to deposits of high-density turbidity currents and cohesive debris flows, up to 20 m thick. Normal grading, with a few exceptions, is present in all types of turbidites. Within each category several types of sedimentation units can be separated. Sedimentation units tend to be clustered into sand- or mud-rich packages (third-order elements). On this hierarchical level, five types of elements can be separated: 1) thick bedded- to disorganized conglomerate/sandstone; 2) thick bedded pebbly sandstone; 3) medium-to thick-bedded sandstone; 4) thin bedded sandstones; 5) mudstone-dominated packages. Each of these is characterized in terms of 1) constitutive sedimentation units; 2) internal structuring; 3) external architecture; 4) distribution and types of bioturbation; 5) paleocurrents. Larger-scale (fourth-order) elements can be defined when coarse grained packages are underlain by an erosional surface and are overlain by fine-grained units, or when different vertical trends can be detected. The whole Upper Tarcau Sandstone, considered a fifth-order element, seems to comprise a lower part dominated by pebbly sandstone-filled channels and the associated overbank fines; a middle part dominated by more sheet-like deposits, possibly corresponding to lobes; and an upper unit, consisting of a regionally extensive debris flow and an overlying thick pebbly sandstone package, which may reflect an eustatic or tectonic influence.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas