Implications of latest Pennsylvanian to middle permian paleontological and U-Pb SHRIMP data from the tecomate formation to re-dating tectonothermal events in the acatlán complex, Southern Mexico

International Geology Review
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Abstract

Limestones in the highly deformed Tecomate Formation, uppermost unit of the Acatlán Complex, are latest Pennsylvanian—earliest Middle Permian in age rather than Devonian, the latter based on less diagnostic fossils. Conodont collections from two marble horizons now constrain its age to range from latest Pennsylvanian to latest Early Permian or early Middle Permian. The older collection contains Gondolella sp., Neostreptognathodus sp., and Streptognathodus sp., suggesting an oldest age limit close to the Pennsylvanian—Permian time boundary. The other collection contains Sweetognathus subsymmetricus, a short-lived species ranging only from Kungurian (latest Leonardian) to Wordian (earliest Guadelupian: 272 ± 4 to 264 ± 2 Ma). A fusilinid, Parafusulina c.f. P. antimonioensis Dunbar, in a third Tecomate marble horizon is probably Wordian (early Guadelupian, early Middle Permian). Furthermore, granite pebbles in a Tecomate conglomerate have yielded ~320-264 Ma U-Pb SHRIMP ages probably derived from the ~288 Ma, arc-related Totoltepec pluton. Collectively, these data suggest a correlation with two nearby units: (1) the Missourian—Leonardian carbonate horizons separated by a Wolfcampian(?) conglomerate in the upper part of the less deformed San Salvador Patlanoaya Formation; and (2) the clastic, Westphalian—Leonardian Matzitzi Formation. This requires that deformation in the Tecomate Formation be of Early—Middle Permian age rather than Devonian. These three formations are re-interpreted as periarc deposits with deformation related to oblique subduction. The revised dating of the Tecomate Formation is consistent with new data, which indicates that the unconformity between the Tecomate and the Piaxtla Group is mid-Carboniferous and corresponds to a tectonothermal event.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Implications of latest Pennsylvanian to middle permian paleontological and U-Pb SHRIMP data from the tecomate formation to re-dating tectonothermal events in the acatlán complex, Southern Mexico
Series title International Geology Review
DOI 10.2747/0020-6814.46.8.745
Volume 46
Year Published 2004
Language English
Publisher Taylor and Francis
Contributing office(s) Geology, Geophysics, and Geochemistry Science Center
Description 9 p.
First page 745
Last page 753
Country Mexico
Other Geospatial Southern Mexico
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