HR: 1340h
AN: U23A-0858    [Abstracts]
TI: Physical Properties of Suevite Section of the Eyreville Core, Chesapeake Bay Impact Structure
AU: * Elbra, T
EM: tiiu.elbra@helsinki.fi
AF: Division of Geophysics, P.O.Box. 64, Helsinki University, 00014, Finland
AU: Pesonen, L J
EM: lauri.pesonen@helsinki.fi
AF: Division of Geophysics, P.O.Box. 64, Helsinki University, 00014, Finland
AB: Chesapeake is a 35 Ma old shallow marine, complex impact structure with a diameter of ca. 85 km. The structure has previously been mapped with shallow drillings. Recently, the deep drilling into inner crater zone near Cape Charles was carried out in order to provide constraints on cratering processes in multi-layered marine targets. The Eyreville-1 core includes three holes with total depth of 1766m (Gohn et al. 2006). We are analyzing the fragments of the Eyreville core including post-impact, impact and basement units of the structure. The sampling interval was chosen dense enough to allow high-resolution petrophysical, paleomagnetic and rock magnetic data to be extracted from the core. Hereby we report the preliminary petrophysical and rock-magnetic data from suevite section of Eyreville core B. Results obtained so far show large variations in magnetic susceptibility data of suevite section. Polymict lithic breccias and cataclasites in lower part of the section are characterized by low magnetic susceptibility (below 0.0003 SI). The upper part, however, consists of more magnetic (susceptibility up to 0.006 SI) suevites. The rock- magnetic measurements (including thermal behavior of magnetic susceptibility and magnetic hysteresis) show the presence of magnetites in lower part of the section. Upper part shows additionally a distinct change in the slope of the susceptibility curve also near 350C, which may indicate the presence of pyrrhotites or maghemites. More extensive studies will be applied in near future in order to clarify the magnetomineralogy and will be presented. References: G. S. Gohn, C. Koeberl, K. G. Miller, W. U. Reimold, C. S. Cockell, J. W. Horton, W. E. Sanford, M. A. Voytek, 2006. Chesapeake Bay Impact Structure Drilled. EOS, vol 87. nr 35
DE: 1519 Magnetic mineralogy and petrology
DE: 1540 Rock and mineral magnetism
DE: 5109 Magnetic and electrical properties (0925)
DE: 5420 Impact phenomena, cratering (6022, 8136)
SC: Union [U]
MN: 2007 Fall Meeting