40. STRUCTURAL EVIDENCE FOR THE NATURE OF HIATAL GAPS IN THE UPPER CRETACEOUS TO HOLOCENE SUCCESSION RECOVERED FROM THE ERATOSTHENES SEAMOUNT1

Rachel Flecker,2 Achim Kopf,3 and Maria José Jurado-Rodríguez4, 5

ABSTRACT

Three sites (Sites 965, 966, 967) drilled into the Eratosthenes Seamount during Ocean Drilling Program Leg 160 recovered a Cretaceous to Pleistocene succession in which several stratigraphic gaps were identified. Some of these are associated with changes in depositional environment, whereas others have apparently identical lithofacies on either side of the hiatus. Four independent structural data sets were generated to ascertain the tectonic characteristics of each hiatal gap. These are bedding and fracture measurements on downhole formation microscanner data; bedding and fracture measurements on recovered core; strain data collected from individual marker particles in thin section; and axial ratio measurements of cross sections through burrows exposed on the split-core face. These data, in combination with lithostratigraphic and biostratigraphic information, indicate that, whereas most of the hiatuses were generated by tectonic events, some were generated by a combination of slow sedimentation, reworking, and possibly sediment bypassing. Furthermore, each drill site appears to be located on a different structural block that was affected by differential movement at least as far back as middle Eocene time.

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).
2Cambridge Arctic Shelf Programme, Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 9EU, United Kingdom. rf211@esc.cam.ac.uk
3Geologisches Institut, Albert-Ludwigs Universität, Albertstrasse 23B, 79104 Freiburg, Federal Republic of Germany.
4Geophysikalisches Institut, Universität Karlsruhe, Hertzstrasse16, D-76187 Karlsruhe, Federal Republic of Germany.
5Present address: Instituto de Ciencias de la Tierra (Jaume Almera) CSIC, Luis Sole Sabaris s/n, 08028, Barcelona, Spain.