Texture development in naturally compacted and experimentally deformed silty clay sediments from the Nankai Trench and Forearc, Japan.

Schumann, Kai, Stipp, Michael, Leiss, Bernd and Behrmann, Jan H. (2014) Texture development in naturally compacted and experimentally deformed silty clay sediments from the Nankai Trench and Forearc, Japan. Tectonophysics, 636 . pp. 125-142. DOI 10.1016/j.tecto.2014.08.005.

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The petrophysical properties of fine-grained marine sediments to a large extent depend on the microstructure and crystallographic preferred orientations (CPOs). In this contribution we show that Rietveld-based synchrotron texture analysis is a new and valuable tool to quantify textures of water-saturated fine-grained phyllosilicate-rich sediments, and assess the effects of compaction and tectonic deformation. We studied the CPO of compositionally almost homogeneous silty clay drillcore samples from the Nankai Accretionary Prism slope and the incoming Philippine Sea plate, offshore SW Japan. Basal planes of phyllosilicates show bedding-parallel alignment increasing with drillhole depth, thus reflecting progressive burial and compaction. In some samples calcite and albite display a CPO due to crystallographically controlled non-isometric grain shapes, or nannofossil tests. Consolidated-undrained experimental deformation of a suite of thirteen samples from the prism slope shows that the CPOs of phyllosilicate and calcite basal planes develop normal to the experimental shortening axis. There is at least a qualitative relation between CPO intensity and strain magnitude. Scanning electron micrographs show concurrent evolution of preferred orientations of micropores and detrital illite flakes normal to axial shortening. This indicates that the microfabrics are sensitive strain gauges, and contribute to anisotropic physical properties along with the CPO.

Document Type: Article
Additional Information: WOS:000345821700010
Keywords: Crystallographic preferred orientation; Synchrotron texture analysis; Soft sediment; Nankai Accretionary Prism; Subduction; RV CHIKYU; IODP Expedition 315, 316, 333
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.tecto.2014.08.005
ISSN: 0040-1951
Projects: IODP, NanTroSEIZE, Future Ocean
Date Deposited: 08 Sep 2014 09:28
Last Modified: 23 Sep 2019 21:33
URI: http://oceanrep.geomar.de/id/eprint/25588

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