Implications of Latest Pennsylvanian to Middle Permian Paleontological and U-Pb SHRIMP Data from the Tecomate Formation to Re-dating Tectonothermal Events in the Acatln Complex, Southern Mexico Academic Article uri icon

abstract

  • Limestones in the highly deformed Tecomate Formation, uppermost unit of the Acatln Complex, are latest Pennsylvanianearliest 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 PennsylvanianPermian 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 MissourianLeonardian carbonate horizons separated by a Wolfcampian(?) conglomerate in the upper part of the less deformed San Salvador Patlanoaya Formation; and (2) the clastic, WestphalianLeonardian Matzitzi Formation. This requires that deformation in the Tecomate Formation be of EarlyMiddle 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. 2004 Taylor & Francis Group, LLC.

published proceedings

  • International Geology Review

author list (cited authors)

  • Keppie, J. D., Sandberg, C. A., Miller, B. V., Snchez-Zavala, J. L., Nance, R. D., & Poole, F. G.

citation count

  • 47

complete list of authors

  • Keppie, J Duncan||Sandberg, Charles A||Miller, BV||Sánchez-Zavala, JL||Nance, RD||Poole, Forrest G

publication date

  • January 2004