The continued fragmentation of Pangaea across the Late Jurassic and Early Cretaceous led to large-scale tectonic processes, on both regional and global scale, accompanied by some of the largest volcanic episodes in the history of the Earth, eustatic oscillations of the sea level, potentially heightened levels of anoxia, oceanic stagnation, and sulphur toxicity. The Weissert Event (~133 million years ago), linked with the main magmatic activity of the Parana`-Etendeka large igneous province (LIP), represents one of the most significant paleoceanographic events of the Early Cretaceous. This global perturbation in the C cycle is marked by a positive (+1.5‰) carbon isotope excursion (CIE) observed both in organic and inorganic records.
A new study analyzed deep sea sediments obtained by the Ocean Drilling Program (ODP) from offshore Antarctica to reconstruct the paleotemperatures. The international team of researchers lead by Liyenne Cavalheiro combinded calcareous nannofossil data and chemostratigraphy, and found that that global temperatures declined by 3.0 °C (±1.7 °C) during the Weissert Event.
Calcareous nannoplankton represent a major component of oceanic phytoplankton. Their calcareous skeletons can be found in fine-grained pelagic sediments in high concentrations and the biomineralization of coccoliths is a globally significant rock-forming process. Additionally, reconstructions of Cretaceous sea-surface temperatures (SSTs) have been revolutionised by the development of the organic palaeothermometer TEX86, based on the distribution of marine archaeal membrane lipids.
Cavalheiro, L., Wagner, T., Steinig, S. et al. Impact of global cooling on Early Cretaceous high pCO2 world during the Weissert Event. Nat Commun 12, 5411 (2021). https://doi.org/10.1038/s41467-021-25706-0
Erba, E., Bartolini, A., & Larson, R. L. (2004). Valanginian Weissert oceanic anoxic event. Geology, 32(2), 149. doi:10.1130/g20008.1
Holz, M., Mesozoic paleogeography and paleoclimates – a discussion of the diverse greenhouse and hothouse conditions of an alien world, Journal of South American Earth Sciences (2015), doi: 10.1016/j.jsames.2015.01.001