Discovery of a Mississippian–early Bashkirian carbonate platform coeval with condensed cephalopod limestone sedimentation in NW Spain

Abstract

A new Mississippian to early Bashkirian shallow‐water carbonate platform, the Valdediezma Limestone, is identified in the central–eastern part of the Picos de Europa tectonic unit of the Cantabrian Mountains. The oldest beds (probably late Tournaisian or early Viséan) are faulted above middle Cambrian rocks. Biostratigraphy based on conodont and foraminiferal faunas allows to differentiate the Viséan–early Bashkirian Valdediezma Limestone from younger Bashkirian and Moscovian shallow‐water platforms previously described in the same area (Valdeteja and Picos de Europa formations). The Valdediezma Limestone recorded the rapid growth of a carbonate platform contemporaneous to the extended sedimentation of the Mississippian condensed, cephalopod‐bearing, nodular carbonates of the Alba Formation in the adjacent deep‐water basin. The growth of the platform continued during the late Serpukhovian and early Bashkirian, when deep‐water carbonates of the Barcaliente Formation were deposited in a geographically restricted foreland basin, and siliciclastic deposits filled the foredeep in the south‐western margin of the Cantabrian Mountains. A sedimentary hiatus from the early Bashkirian to the late Moscovian occurs above the Valdediezma Limestone. The exhumed and eroded platform was buried by late Moscovian to Kasimovian strata when the Variscan deformation affected the Picos de Europa unit. The Valdediezma Limestone was deposited on an isolated platform that rarely is preserved in South Europe, where contemporary shallow‐water carbonates were eroded and reworked into the synorogenic siliciclastic deposits of flysch‐type facies.