High sea-surface temperatures during the Early Cretaceous Epoch

The Early Cretaceous Epoch, about 145-100 million years ago, is generally thought of as a greenhouse period, with high atmospheric CO 2 concentrations and high global mean temperatures. But evidence for episodes of cooler conditions, and even transient glaciations, has been proposed. Here we present sea-surface temperature records spanning the period from 142 to 128 million years ago (Berriasian-Barremian ages) from low and mid latitudes, reconstructed using the TEX 86 palaeotemperature proxy. During this period, we find sea-surface temperatures exceeding 32 °C at 15°-20° N and averaging 26 °C at ∼53° S. These temperatures substantially exceed modern temperatures at equivalent latitudes, and are incompatible with the notion of consistently cooler conditions in the earliest Cretaceous. Moreover, we find little variability in the sea-surface temperature records, even during the Valanginian carbon-isotope excursion ∼138-135 million years ago, which was thought to be associated with marked temperature fluctuations. We conclude that the earliest Cretaceous was characterized by a warm, stable climate, with a lower meridional temperature gradient than today. © 2011 Macmillan Publishers Limited. All rights reserved