Miocene paleoenvironmental reconstitution of Chelas (Portugal) using stable isotopes from the enamel of molars from a proboscidean and associated palynomorphs
Paleoclimate reconstruction is essential for understanding the Earth's climate system, its
dynamics, and the drivers of climate change. By examining past climate variability, it provides
critical context for interpreting present-day climate trends and identifying key factors that
shaped past climatic shifts. In this study, we reconstitute the palaeoenvironment of the Middle
Miocene fossil sites of Quinta da Farinheira and Charneca (Chelas Valley and Lumiar, Lisbon,
MN5, 13.7–16.0 Ma) using a multi-proxy approach. This includes biogeochemical analysis of
stable isotopes (δ18O and δ13C) from proboscidean molar enamel and a paleobotanical
investigation of site sediments to analyze local flora. These analyses are complemented by a
systematic review of proboscideans from the area, housed at the Geological Museum of
Lisbon, alongside a detailed description of previously undescribed fossils stored at NOVA
University of Lisbon (UNL). These fossils include eleven molars, a vertebra, and an occipital
cranial bone from large proboscideans.
Proboscidean records from the Miocene in Portugal, such as Gomphotherium sp.,
Deinotherium sp., and Tetralophodon sp., are numerous. Our findings indicate that most of the
materials studied belong to Gomphotherium angustidens, with one exception, specimen FCT-
DCT 4945 belongs to Amebelodon sp. G. angustidens, a species widespread in Europe during
the Miocene. The combination of proxies suggests that the Middle Miocene climate in Chelas
was subtropical and temperate, with mean annual temperatures (MAT) around 20°C. This
aligns with the Mid-Miocene Climatic Optimum (MMCO), occurring between 17 and 15 Ma, a
period marked by elevated global temperatures and atmospheric CO₂ levels. These findings
provide valuable insight into how climate changes impact mammal faunas
