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Thermal evolution of Monte Blanco dome: Low-angle normal faulting during Gulf of California rifting and late Eocene denudation of the eastern Peninsular Ranges

Axen, Gary J. and Grove, Marty and Stockli, Daniel and Lovera, Oscar M. and Rothstein, David A. and Fletcher, John M. and Farley, Kenneth and Abbott, Patrick L. (2000) Thermal evolution of Monte Blanco dome: Low-angle normal faulting during Gulf of California rifting and late Eocene denudation of the eastern Peninsular Ranges. Tectonics, 19 (2). pp. 197-212. ISSN 0278-7407. http://resolver.caltech.edu/CaltechAUTHORS:20121128-155419476

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Abstract

Footwall rocks of the Cañada David detachment fault, northeastern Baja California, record late Eocene-earliest Oligocene and late Neogene cooling events previously unrecognized in the region. Biotite ^(40)Ar/^(39)Ar ages of ∼65 Ma reflect slow cooling through ∼350°C, 5 to 10 m.y. later than is typical in the region. Multiple diffusion domain modeling of K feldspar ^(40)Ar/^(39)Ar release spectra shows very slow cooling (∼1°C/m.y.) from ∼65 to ∼45 Ma. Accelerated cooling from ∼315°C to ∼215°C between ∼45 and ∼33 Ma records at least 3–4 km of denudation that we relate to east-side-up reactivation of late Cretaceous structures that generally follow the oceanic-continental suture. Previously established rivers flowing west from mainland Mexico apparently became further entrenched during this uplift and continued to supply distinctive rhyolitic detritus to the coast. Ultimately, surface uplift disrupted and rerouted the extraregional rivers some 2 to 6 m.y. before the cooling event ended. Footwall rocks remained nearly isothermal from ∼30 to ∼15–10 Ma, when renewed rapid cooling (33° ± 17°C/m.y.) began in response to footwall exhumation by top-to-the-west low-angle normal faulting that accommodated rift-related extension in what finally became the Gulf of California. Apatite fission track and (U-Th)/He ages of ∼5 Ma and ∼4 Ma, respectively, record final detachment-related cooling through ∼110°C to ∼70°C. Thermal-kinematic modeling suggests that 5–7 km of late Neogene tectonic denudation and 10–12 km of horizontal extension were necessary in order to unroof the samples by 2 Ma. Additional extension, of unknown magnitude, has probably occurred subsequently. Geodetically measured horizontal extension rates are considerably higher than the long-term extension rate that can be attributed to detachment faulting.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1029/1999TC001123DOIUNSPECIFIED
http://www.agu.org/pubs/crossref/2000/1999TC001123.shtmlPublisherUNSPECIFIED
Additional Information:© 2000 American Geophysical Union. Received 19 April 1999; accepted 29 October 1999. Funded by grants from UC MEXUS and UCLA Committee on Research to Axen, from DOE to T.M. Harrison (DE-FG-03-89ER14049), from CONACYT to Fletcher (4345-PT), and a Stanford University McGee grant to Stockli. We thank T. Dumitru for helpful discussions and E. Campbell-Stone and P. Umhoefer for thoughtful reviews.
Funders:
Funding AgencyGrant Number
UC MEXUSUNSPECIFIED
UCLA Committee on ResearchUNSPECIFIED
Department of Energy (DOE)DE-FG-03-89ER14049
CONACYT4345-PT
Stanford University McGee grantUNSPECIFIED
Subject Keywords:Geochemistry: Geochronology; Tectonophysics: Continental tectonics—extensional; Tectonophysics: Continental tectonics—general; Tectonophysics: Plate boundary—general
Record Number:CaltechAUTHORS:20121128-155419476
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20121128-155419476
Official Citation:Axen, G. J., M. Grove, D. Stockli, O. M. Lovera, D. A. Rothstein, J. M. Fletcher, K. Farley, and P. L. Abbott (2000), Thermal evolution of Monte Blanco dome: Low-angle normal faulting during Gulf of California rifting and late Eocene denudation of the eastern Peninsular Ranges, Tectonics, 19(2), 197–212, doi:10.1029/1999TC001123.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:35715
Collection:CaltechAUTHORS
Deposited By: Jason Perez
Deposited On:29 Nov 2012 00:24
Last Modified:27 Dec 2012 03:04

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