Abnormal fluid pressures and fault-zone dilation in the Barbados accretionary prism: Evidence from logging while drilling

Moore, J. C., Shipley, T. H., Goldberg, D., Ogawa, Y., Filice, F., Fisher, A., Jurado, M.-J., Moore, G. F., Rabaute, A., Yin, H., Zwart, G., Brückmann, Warner, Henry, P., Ashi, J., Blum, P., Meyer, A., Housen, B., Kastner, M., Labaume, P., Laier, T., Leitch, E. C., Maltman, A. J., Peacock, S., Steiger, T. H., Tobin, H. J., Underwood, M. B., Xu, Y. and Zheng, Y. (1995) Abnormal fluid pressures and fault-zone dilation in the Barbados accretionary prism: Evidence from logging while drilling Geology, 23 (7). pp. 605-608. DOI 10.1130/0091-7613(1995)023<0605:AFPAFZ>2.3.CO;2.

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Abstract

Logs collected while drilling measured density in situ, through
the accretionary prism and decollement zone of the northern Barbados
Ridge. Consolidation tests relate void ratio (derived from
density) to effective stress and predict a fluid pressure profile, assuming
that the upper 100 m of the prism is at a hydrostatic pressure
gradient. The calculated fluid pressure curve rises to >90% of
lithostatic below thrusts in the prism, presumably due to the increase
in overburden and lateral tectonic loading. Thin (0.5–2.0 m)
intervals of anomalously low density and resistivity in the logs
through the basal decollement zone suggest dilation and perhaps
hydrofracturing. A peak in hydraulic head in the upper half of the
decollement zone requires lateral influx of fluid, a conclusion consistent
with previous geochemical studies. Although the calculated
fluid-pressure profile is model dependent, its inherent character
ties to major structural features.

Document Type: Article
Keywords: Barbados accretionary prism; fluid pressure; fault-zone dilation; ODP Leg 156
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
Refereed: Yes
DOI etc.: 10.1130/0091-7613(1995)023<0605:AFPAFZ>2.3.CO;2
ISSN: 0091-7613
Projects: ODP
Date Deposited: 01 Mar 2016 14:18
Last Modified: 17 May 2017 07:58
URI: http://eprints.uni-kiel.de/id/eprint/31649

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