Brian M. Whiting2


A major thematic objective of Ocean Drilling Program Leg 160 drilling was an improved understanding of the processes involved in the initial stages of continental collision. The Eratosthenes platform is hypothesized to be a fragment of thinned North African crust that is about to be subducted beneath Cyprus. Incipient subduction appears to be accompanied by extensive normal faulting, indicating that the Eratosthenes platform is undergoing breakup. Drilling at Sites 965-968 was aimed primarily at documenting the timing and nature of the subsidence and breakup. Using shipboard paleontologic and physical properties data, supplemented with postcruise age refinements, paleobathymetric estimates, and porosity vs. depth determinations, I present quantitative decompacted subsidence histories for Sites 966 and 967, which are located on or immediately adjacent to the Eratosthenes platform. Taken together, the subsidence results are consistent with a model in which the Eratosthenes platform is a part of North African passive margin that underwent exponentially decreasing thermal subsidence since at least early Cretaceous time, was uplifted during the late Oligocene or early Miocene, and then began a phase of rapid tectonic subsidence by late Miocene time, which has continued to the present day. The overall interpretation of the subsidence history presented here is that the Eratosthenes platform represents a thinned promontory of North African lithosphere that is now in the early stages of tectonic contact with the Eurasian plate. Breakup and subsidence since Miocene time may be related to bending stresses on the North African lithosphere associated with collision.

1Robertson, A.H.F., Emeis, K.-C., Richter, C., and Camerlenghi, A. (Eds.), 1998. Proc. ODP, Sci. Results, 160: College Station, TX (Ocean Drilling Program).
2Department of Geology, College of William and Mary, Williamsburg, VA 23187, U.S.A. (Present address: Department of Geology, Central Washington University, Ellensburg, WA 98926, U.S.A.) bmw@gis.cwu.edu