High-resolution clay mineral and δ18Ocarb analyses have been performed on three sections of Valanginian age (Early Cretaceous), from northwestern (~20–30°N) and southern (~53°S) Tethyan realms. The data have been integrated in a large set of published mineralogical (clays), and geochemical (δ18Ocarb, δ18Obivalve, δ18Olenticulina, δ18Obelemnite, and TEX86) data from 17 sections, situated between ~45°N and ~53°S. Based on this data set, we provide new insights into Valanginian climate conditions from a wide range of palaeolatitudes. We highlight climate trends within specific areas and identify main climate belts. In the Proto-North Atlantic realm (~15–17°N) large amounts of smectite together with the occurrence of palygorskite testify for a semi-arid climate belt throughout the Valanginian. Significant variations in kaolinite content in the northwestern Tethyan realm (~20 to 30°N) suggest that this realm has been more sensitive to changes in hydrological cycling and subsequent erosion and runoff processes during the early to early–late Valanginian transition interval. This time interval, that is coincident with the pronounced positive and globally recognized carbon isotope excursion (CIE; the Weissert episode), documents the wet conditions of a humid subtropical climate belt. Temperature ranges derived from δ18O records suggest climate warming by about 3–5±0.9°C in the northern hemisphere, during the Weissert episode. This is followed by a global cooling of about ca. 1–5±0.9°C in both hemispheres, during the late Valanginian.
We postulate that these patterns were due to interplays between tectonic and orbital factors, which have controlled the distribution of regional palaeoclimate belts during the Valanginian. The semi-arid belt expressed in the Proto North Atlantic realm has probably been induced by its specific palaeogeographic configuration and the existence of isolated basins, which were each characterized by strong and continuous thermohaline circulation. An eccentricity paced monsoon-like system might have played a significant role in maintaining the subtropical belt around the northwestern Tethyan realm, up to the mid latitudes (~35–45°N). Superimposed on these regional processes, a widespread magmatic pulse in Paraná-Etendeka volcanic activity might have stimulated greenhouse conditions, impacting marine biota and favouring the development of a dense vegetation cover on the continent. An increase in sedimentary burial of 13C depleted organic carbon on the continents may have contributed to the progressive global positive carbon isotope excursion. In the medium term, it has also probably led to a significant decrease in atmospheric CO2, as testified by the global cooling recorded during the late Valanginian in both hemispheres and the probable concomitant extension of polar ice caps.