Guerrero-Morelos Platform drowning at the Cenomanian–Turonian boundary, Huitziltepec area, Guerrero State, southern Mexico

摘要: Abstract Facies successions in three stratigraphic sections (Barranca del Tigre, Axaxacoalco, and Zotoltitlan, Guerrero State, southern Mexico) that comprise middle Cenomanian to lower Turonian rocks of the central part Guerrero-Morelos Platform, indicate drowning some parts platform near Cenomanian-Turonian boundary. In western study area Tigre section), shallow-marine limestones (mainly subtidal facies) with abundant benthic fauna foraminifera) pass upwards a 7-m-interval open-marine nodular few organisms then dark-grey black laminated pelagic marls. west-central (Axaxacoalco restricted (intertidal change abruptly marls only (calcisphaerulids, planktonic foraminifera, radiolaria). eastern (Zotoltitlan intertidal are overlain by 45 m showing up-section rapid decrease diversity until calcisphaerulids echinoderm fragments occur. Overlying these rocks, there 65 m shaly thick strata renewed fauna, 80 m silty intercalated claystones siltstones, finally, dark grey/black The facies suggest progressive Platform around We attribute occurrence anoxic event. impingement waters over could produce drastic reduction carbonate producing benthos observed therefore accumulation rates. Subsidence late Cenomanian-earliest sea-level rise were able drown platform. This occurred first part, where conditions dominated an irreversible occurred, allowing deposition organic-rich sediments pre-existing carbonates. At same time, dominated, changed conditions, shallow deep later. Here, temporal restoration sedimentation resulted, but eventually this region was also drowned, probably interplay terrigenous-clastic supply new waters.