ABSTRACT: The Dip Method: An Alternative Method for Inferring Tectonic Kinematics in Extensional Terrains

SCOTT, DEBORAH L., Australian National University, Canberra, Australian Capital Territory, Australia

In recent years a plethora of seismic data have become available to analyze basins, especially submerged basins. These data are often the only source of information for the interpretation of structures that formed the basin. Fault geometries thus derived are frequently ambiguous, but are, nonetheless, used to infer regional tectonic kinematics, particularly in extensional terrains. In ideal orthogonal extension and/or strike-slip deformation there is predicted to be a simple relationship between the primary fault geometries and regional kinematics. However, in the absence of geological kinematic indicators this is only as valid as the structural interpretation is constrained. We present a method of inferring tectonic kinematics that is independent of fault geometries based on the rota ion of infra-basinal basement blocks, termed the dip method. We show the validity of the method in the ideal orthogonal extension case. Further, we show that the method is equally valid for transtensional systems. The method is applied to two such basins, in the East African rift system, Lakes Tanganyika and Malawi and to several offshore basins on passive margins of Australia. Implications of the apparent transtensional nature of all of these basins to structural closures, such as rollover, are addressed.

AAPG Search and Discovery Article #91015©1992 AAPG International Conference, Sydney, N.S.W., Australia, August 2-5, 1992 (2009)