The Middle America Trench
Barclay P. Collins, Joel S. Watkins, 1986. "The Middle America Trench", Seismic Images of Modern Convergent Margin Tectonic Structure, Roland von Huene, Susan Vath, Christine Sperber, Bridgett Fulop, Lee Bailey, Monique Martin
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Seismic line MX-16 transects the Middle America Trench on the Pacific coast of Mexico. The bathymetric map reveals a narrow continental shelf, a steep trench slope, and an axial trench about 5 km below sea level. A large submarine canyon cuts the upper slope in the vicinity of line MX-16. This area was extensively drilled during Leg 66 of the Deep Sea Drilling Project (Watkins et al., 1982).
Subduction in the area has been active intermittently during the last 100 m.y. (Karig et al., 1978). The convergence rate of the underthrusting Cocos plate relative to the overriding North American plate is inferred to be about 7 cm/yr (Minster and Jordan, 1978). Leg 66 drilling results suggest the continental margin in the area was truncated between 10 and 35 m.y.B.P., perhaps by transcurrent faulting or subduction erosion (Moore et al., 1982). A small accreted wedge subsequently developed by sediment underplating and offscraping (Moore et al., 1982). No forearc basin such as those seen on many trench slopes is evident on seismic line MX-16.
Figures & Tables
In 1980, A. W. Bally assembled and edited an innovative three-volume “picture and work” atlas of seismic reflection record sections. This compilation of more than 130 excellent seismic section reproductions provided much new data from the earth's subsurface. For petroleum geologists, academic scientists, and students, it is the field geologist's counterpart of outcrops and type sections. The smaller collection of seismic sections presented in this Studies 26 publication was inspired by Bally's atlas, and follows his general format and philosophy. The objective is to provide a reference series of sections for the earth sciences and a vehicle for continuing scientific dialogue relating to modern convergent margins. This publication's assembled sections represent a single facet of that dialogue by bringing together a series of exceptional seismic sections from the fronts of presently active convergent margins around the Pacific.