170 Scientific Prospectus
Scientific Objectives
The main focus of Leg 170 is to determine mass- and fluid-flow paths through a remarkably well
constrained accretionary complex to calculate mass and fluid balances. Drilling data will facilitate an integrated effort to understand these processes using structural data and the physical and chemical properties of both the sediments and their pore fluids.
The general objectives of the leg are:
- Determine the sediment, chemical, and fluid mass balances within the accretionary prism and the larger subduction system (including the volcanic arc).
- Test whether or not the prism is developing in equilibrium with the incoming sedimentary material and, if so, to quantify the partitioning of material into offscraped, underplated, internally shortened, and subducted volumes.
- Determine the effects of fluids on prism deformation.
The specific objectives of the drilling program are to determine:
- Age and nature of the accretionary wedge beneath the slope apron.
- Rate of accretion of the wedge.
- Nature of the lower part of the apron and time sequence of formation.
- Physical properties of the material above, within, and below the top-prism reflector.
- Relative importance of underplating vs. out-of-sequence faulting;.
- Evidence of fluid stratigraphy and flow distribution within the wedge materials.
- Nature of apron material relative to deep-sea hemipelagic sediment.
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