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Synchronous 29–19 Ma arc hiatus, exhumation and subduction of forearc in southwestern Mexico

By
J. Duncan Keppie
J. Duncan Keppie
Instituto de Geología
,
Universidad Nacional Autónoma de México
,
04510 México D.F.
,
Mexico
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Dante J. Morán-Zenteno
Dante J. Morán-Zenteno
Instituto de Geología
,
Universidad Nacional Autónoma de México
,
04510 México D.F.
,
Mexico
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Barbara Martiny
Barbara Martiny
Instituto de Geología
,
Universidad Nacional Autónoma de México
,
04510 México D.F.
,
Mexico
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Enrique González-Torres
Enrique González-Torres
Instituto de Geología
,
Universidad Nacional Autónoma de México
,
04510 México D.F.
,
Mexico
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Published:
January 01, 2009

Abstract

The geology of southwestern Mexico (102–96°W) records several synchronous events in the Late Oligocene–Early Miocene (29–19 Ma): (1) a hiatus in arc magmatism; (2) removal of a wide (c. 210 km) Upper Eocene–Lower Oligocene forearc; (3) exhumation of 13–20 km of Upper Eocene–Lower Oligocene arc along the present day coast; and (4) breakup of the Farallon Plate. Events 2 and 3 have traditionally been related to eastward displacement of the Chortís Block from a position off southwestern Mexico between 105°W and 97°W; however at 30 Ma the Chortís Block would have lain east of 95°W. We suggest that the magmatic hiatus was caused by subduction of the forearc, which replaced the mantle wedge by relatively cool crust. Assuming that the subducted block separated along the forearc–arc boundary, a likely zone of weakness due to magmatism, the subducted forearc is estimated to be wedge-shaped varying from zero to c. 90 km in thickness; however such a wedge is not apparent in seismic data across central Mexico. Given the 121 km/Ma convergence rate between 20 and 10 Ma and 67 km/Ma since 10 Ma, it is probable that any forearc has been deeply subducted. Potential causes for subduction of the forearc include collision of an oceanic plateau with the trench, and a change in plate kinematics synchronous with breakup of the Farallon Plate and initiation of the Guadalupe–Nazca spreading ridge.

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Geological Society, London, Special Publications

The Origin and Evolution of the Caribbean Plate

K. H. James
K. H. James
Aberystwyth University, Wales, UK
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M. A. Lorente
M. A. Lorente
Central University of Venezuela, Venezuela
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J. L. Pindell
J. L. Pindell
Tectonic Analysis Ltd, West Sussex, UK
Rice University, Texas, USA
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Geological Society of London
Volume
328
ISBN electronic:
9781862395763
Publication date:
January 01, 2009

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