The Campo section (Pyrenees, Spain) revisited: Implications for changing benthic carbonate assemblages across the Paleocene–Eocene boundary

The Campo section is a parastratotype section for the shallow-water Ilerdian and Cuisian stages. Although a lot of work has been concentrated during the last years on biostratigraphy, sequence stratigraphy, magnetostratigraphy, and geochemistry, surprisingly little work has been published on the facies development. Here we evaluate the facies evolution with particular emphasis on the biogenic assemblages of the latest Paleocene (shallow benthic zonation 4) to the earliest Eocene (shallow benthic zonations 5 and 6) of the Campo and the nearby Serraduy section. Overall, the facies show a deepening in the Paleocene and the Eocene, interrupted by a terrestrial interval across the newly defined Paleocene/Eocene boundary. In the late Paleocene altogether seven microfacies types were distinguished. These are dominated by various algal taxa and subordinate corals and larger foraminifera. The lower Eocene carbonate platform is characterised by twelve microfacies types, which are dominated by larger foraminifera such as alveolinids, orbitolitids and nummulitids and subordinate corals. This facies dichotomy recognized in the Campo and Serraduy sections can be extrapolated to the whole Pyrenean region in the early Paleogene and is even found in Egypt. The comparison of the two regions shows that the facies dichotomy is less pronounced in the Pyrenean region. This is interpreted to reflect a latitudinal trend, where corals are absent in the low latitudes, while in the middle latitudes they occur subordinately. This gradient within the facies distribution can be explained by latitudinal temperature changes and by the long-time warming in the early Paleogene and the short-time warming of the Paleocene Eocene Thermal Maximum. Hot temperatures in the low latitudes hamper the growth of temperature sensitive corals, while in the middle latitudes the temperatures were still in a favourable temperature range.