Physical Properties Changes of Sediment Packages Determined from Logging-While-Drilling Data at Nankai Trough/Japan (ODP Leg 196)
Abstract
Physical properties of sediments entering the Nankai Trough subduction complex play an important role in the development of this accretionary prism. During May-July 2001 Ocean Drilling Program (ODP) Leg 196 investigated the relationship between deformation, physical properties, and fluid flow in the toe of the Nankai Trough accretionary prism. Previous drilling during ODP Legs 131 and 190 has already focused on the change of index properties around the décollement zone in detail. One of the key questions of ODP Leg 196 was to determine the porosity or fluid content of incoming sediments, accretionary prism, and underthrust sediments. Logging-While-Drilling (LWD) data of high quality exist at two sites: Site 1173 is located seaward of the frontal thrust to provide information on physical properties of the incoming sediments, Site 808 examined the sediments within the protothrust zone. These two sites allow new insights in the physical properties of the development in this sand-rich end member accretionary prism. The LWD data of ODP Leg 196 enable to correlate sediment packages among the two drill sites using the parameters gamma ray, density and magnetic susceptibility. This correlation quantifies the changes of bulk density between Sites 1173 and 808, and estimates the change of water content/porosity within each site. A detailed log analysis of LWD data enables to reconstruct lithologies in sections with no or low core recovery (especially at Site 808). Thus, the lithology-dependent variation of sediment compaction can be characterized.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2001
- Bibcode:
- 2001AGUFM.T41A0850H
- Keywords:
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- 5100 PHYSICAL PROPERTIES OF ROCKS;
- 8045 Role of fluids;
- 8105 Continental margins and sedimentary basins