Title

Tectonostratigraphic assessment of the Tierra Caliente Metamorphic Complex, southern Mexico

Date of Award

1995

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Marine Geology and Geophysics

First Committee Member

Christopher G. A. Harrison, Committee Chair

Abstract

I present the basic stratigraphy and deformation sequence of the TCMC in southern Mexico, based on the photo interpretation of TM images and field mapping. The more than 2.7 km thick metamorphic portion of the TCMC in the Teloloapan-Arcelia area includes the Taxco Schist, the Roca Verde Taxco Viejo and the Almoloya Phyllite. Although six whole rock, K-Ar radiometric dates (94.4-44.1 Ma) were obtained, the age of the metamorphism and protolith of TCMC metamorphic rocks is still uncertain. The 2.9 km thick disconformable sedimentary cover comprises the Pochote, Morelos, Mexcala formations, and undifferentiated red beds and volcanic rocks that span from Aptian through Tertiary times. Lithologic variations within the study area and surroundings can be explained in terms of carbonate platform and intervening basins, built disconformably over metamorphic rocks of the TCMC. Predominantly carbonate environments developed on and were possibly restricted by contemporary back-arc basin volcanic rocks. The study area consists of the southern portion of a south-plunging antiform cored by the Taxco Schist and fault bounded on both eastern and western flanks. The TCMC rocks show at least two compressional deformation phases. The first and most prominent phase, records a mean direction of 068$\sp\circ$. This phase is responsible for the east verging asymmetrical folding and thrusting of both the metamorphic sequence and suprajacent sedimentary strata. The second phase, has an average transport direction of 232$\sp\circ$ and is apparently restricted to the western portion of the study area. A third extensional phase is responsible for normal faulting. The lack of a discernible deformation phase which pre-dates the Cenomanian-Campanian Mexcala flysch indicates a Late Cretaceous-Paleogene age for the main deformation event in the TCMC. This event would be coincident with Cordilleran Laramide deformation. Analysis of the stratigraphy and structure of the Teloloapan-Arcelia region does not require accretion of exotic terranes. The TCMC region can be better interpreted in terms of the evolution of Mesozoic volcanic and sedimentary strata over attenuated continental crust. In fact, the constraints that this work provide, raise doubts about the allochthonous nature of the TCMC rocks.

Keywords

Geology

Link to Full Text

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