Paper No. 3
Presentation Time: 08:30-18:30
SEDIMENTATION, DEFORMATION AND MAGMATISM OF THE JURASSIC AYUQUILA AND TECOMAZÚCHIL FORMATIONS IN TEXCALAPA, PUEBLA - HUAJUAPAN DE LEON, OAXACA REGION
Based on the recognition of major unconformities, magmatic and detritic zircons dating, as well as facies analysis of pre-Oxfordian clastic succession of Texcalapa – Huajuapan area, we propose to subdivide the succession into three lithostratigraphic units separated by angular unconformities, these are the La Mora, Ayuquila, and Tecomazuchil formations.The La Mora formation is made up of fine-grained sandstones originated by fluvial flood deposits. The Ayuquila Formation consists of monomictic conglomerate of metamorphic or sandstone clasts, lithic and feldspathic greywacke. We propose as type locality of the Ayuquila Formation, the succession exposed to north of Chilixtlahuaca, Puebla, it contains fossil plants (ferns and wood fragments). Youngest detrital zircon cluster of 182 Ma age from the Ayuquila Formation, constraints the age of the La Mora as pre Pliensbachian. Intrusives of 164.3±3.6 Ma and 156.9±3.5 Ma are emplaced in the La Mora and Ayuquila formations, suggesting that deposition of the Ayuquila Formation occurred between Pliensbachian and Callovian. The Tecomazúchil Formation consists of a fining upward succession, made up of quartz-rich conglomerate and sandstone (subarkose, sublitarenite)It changes from non marine to transitional to marine depositional environments, and changes transitionally to the Chimeco limestone formation. Sedimentation took place in an asymmetric and extensional small sedimentary basin, bounded by faults, El Sabino-Texcalapa normal fault, and left-lateral Petlalcingo - Huajuapan Fault. During the deposition of the Ayuquila Formation (Early to Middle Jurassic) sedimentation occurred from west to east-southeast, building alluvial fans at the faulted western margin and developing braided streams with southward main drainage, and lacustrine facies to the south. The succession of the Ayuquila formation was tilted previous to the deposition of the Tecomazuchil formation. The discordant fluvial sedimentation of the Tecomazúchil Formation was controlled by the Petlalcingo - Huajuapan fault.