Barbados Ridge Accretionary Prism,
Ocean Drilling Program, Leg 156
Principal Investigator: Thomas H. Shipley
Funded by: Texas A & M University
Leg 156 investigated temporal and spatial scales of fluid flow, the role of faults in
fluid transport, and the relationship between mechanical state and seismicity in the
northern Barbados Ridge accretionary prism. The strategy was to drill into areas of
strikingly different polarity and amplitude of the dŽcollement reflection, revealed
by recently acquired, three-dimensional seismic data and interpreted as areas of varying
fluid content and/or fluid migration paths within the dŽcollement. Eight holes were
drilled at Sites 947, 948, and 949, located 6 km, 4 km, and 2 km west of the thrust front,
respectively.
On Leg 156, the objective was to combine both in situ measurements of permeability and
fluid pressures, long-term monitoring of temperature in and pressure, and fluid chemistry
and structural fabric studies in an integrated program. This experiment is an important
and necessary step in evaluating the role of faults in fluid transport, episodicity of
fluid flow, and the relationship to seismicity. Understanding the fate of subducted and
accreted fluids will also contribute to geochemical cycle definition. This program is a
logical step in advancing the technological and drilling techniques needed in this
environment.
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