A multiproxy approach for the reconstruction of ancient continental environments. The case of the Mio–Pliocene deposits of the Granada Basin (southern Iberian Peninsula)

Abstract

Palaeoenvironmental reconstructions from fossil mammals are based on the straightforward relationship between the environment and the mammal assemblage living in the area. However, in some cases the environmental variables estimated from mammals are biassed by local influences. The palaeoenvironmental reconstruction of the Granada Basin (southern Spain) based on carbon and oxygen isotopes from enamel rodent teeth is compared with the palaeoenvironmental data from small mammal assemblages. Estimated temperatures from both proxies coincide, in general terms: cold-temperate conditions during the latest Tortonian (~16°C; cold-temperate climate), dry sub-tropical conditions during the Messinian (16.6°C–22°C), and dry sub-tropical conditions during the early Pliocene (16.6°C–17.2°C). Reconstructed humidity trends from both proxies only agree in the first part of the record, showing dry conditions during the Tortonian–Messinian boundary and an increase in humidity at the beginning of the Messinian. During the Messinian and earliest Pliocene, humidity trends in each proxy are frequently opposed: small mammal assemblages suggest a huge increase in humidity at the beginning of the Messinian, and a decreasing trend towards the Pliocene, whereas carbon isotopes from rodent teeth suggest moderate humidity conditions during the Messinian. It can be concluded that physical changes in the landscape would affect taxa with high dependence on humid conditions, and they are more likely to record local environmental humidity changes rather than regional or global humidity ones. However, the past reconstructions of temperatures are not biassed by this effect, as the general temperature trends deduced from the faunal assemblages as well as those deduced from the isotopic approaches coincide. The general climatic trends reconstructed from isotopic analyses in small mammal teeth agree with the general environmental change in the western Mediterranean region as well as with the global evolution of sea temperatures.