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Rates Of Sediment Recycling Beneath The Acapulco Trench: Constraints From (U-Th)/He Thermochronology

Domenii publicaţii > Ştiinţele pământului şi planetare + Tipuri publicaţii > Articol în revistã ştiinţificã

Autori: Ducea, M.N., Valencia, V.A., Shoemaker, S., Reiners, P., DeCelles, P., Campa, M., Moran-Zenteno, D., and Ruiz, J.

Editorial: Journal of Geophysical Research, 10.1029/2003JB003112, p.11 p., 2004.

Rezumat:

The Sierra Madre del Sur mountain range is an uplifted forearc associated with the subduction of the Cocos plate along the Acapulco trench beneath mainland southern Mexico. The shallow subduction angle, the truncation of geologic features along the modern Acapulco trench, and direct seismic and drill-hole observations in the trench through deep sea drilling data, suggest that subduction erosion is an important process during the evolution of this margin. Turbidites derived from the uplifted forearc are the predominant sedimentary input into this trench, while pelagic sediments are subordinate. Apatite (U-Th)/He ages were obtained on 23 samples from two transects across the Sierra Madre del Sur (Acapulco and Puerto Escondido) and reveal slow cooling during Miocene. (U-Th)/He ages range between ~25 and 8 Ma, and correlate inversely with elevation. Long-term erosional exhumation rates inferred from these ages range from 0.11 to 0.33 km/My, with higher rates in the range core, and suggest that the Sierra Madre del Sur has been a slowly decaying mountain range, since at least the early Miocene. Apparent Miocene-Pliocene sedimentation (?preservation?) rates in the Acapulco trench derived from DSDP data are about an order of magnitude smaller than the Miocene forearc erosion rates estimated from (U-Th)/He ages, suggesting that the terrigeous input to the trench was almost entirely recycled via subduction erosion, at least during the Miocene. The Miocene subducted flux per unit length of the margin is about 30 km3/(km My), or a subducted volume per unit time of 44 x 103 km3/My, when integrated over the length of the trench.

Cuvinte cheie: subduction erosion, Acapulco trench, UThHe thermochronology