Paleocene-Lower Eocene carbonate platforms of westernmost Tethys

Abstract

The Paleocene-lower Eocene succession is well exposed in Sierra Espuña-Mula Basin (Betic Cordillera, S Spain) and carbonate platforms are well represented as part of this succession. The study of the paleoenvironmental evolution of these platforms has allowed to cover an important gap in the knowledge in the westernmost Tethys. Thirteen microfacies (Mf1 to MF13) were recognized based mainly on the fossil assemblage (principally larger benthic foraminifera), texture and fabric of the microfacies. The fossiliferous assemblage of the entire succession shows a mixture of photozoan and heterotrophic biogenic elements, typical of an inner to outer ramp environment of a warm temperate biogeographic province. Fragments of hermatypic corals have also been detected in the lower part of the succession (Paleocene) allowing thinking in propitious conditions in this period. The succession evolves upwards (Lower Eocene) to low-energy shallow marine protected environments (lagoon) in inner ramp settings. In addition, abundant porcelaneous larger benthic foraminifera such as alveolinids and soritids are indicative of euphotic shallow marine conditions in moderately oligotrophic upper subtidal environments. In the upper part of the succession, hermatypic corals as displaced fragments and in situ isolated coral phaceloid colonies also appear together with other biogenic components indicating warm shallow and euphotic marine conditions (coral-maërl environment). Lenticular larger benthic foraminifera, characterizing marine mesophotic and oligotrophic habitats can be found in the upper part of the middle ramp, and flattened larger benthic foraminifera forms indicating lowermost mesophotic conditions in a distal middle ramp. The obtained results have been compared with other similar Tethyan sectors obtaining a broader view. The biogenic marine association is characterized by the absence of the ‘Lockhartia community’ of the Tethyan domain, together with the dominance of alveolinids, nummulitids and orthophragminids. During most of the Paleocene, northern Mediterranean Tethys platforms were located in the middle paleolatitudes and characterized by coral-reef and coralgal biofacies. The studied platforms (located at a latitude close to 25°N) show, in a ramp-like context, underdeveloped in situ coral constructions probably of patch-reef type. In the early Eocene the expansion and abundance of the larger benthic foraminifera and the practical disappearance of coral took place in the sedimentary platforms through the entire Tethys. However, in the study area small reef coral build-ups have also been observed in the lower Cuisian beds, indicating that in westernmost Tethys coral construction continued at these latitudes.