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Science 2019 08;365(6456):926-929

Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Princetonlaan 8a, 3584 CB Utrecht, Netherlands.

Astronomical calculations reveal the Solar System's dynamical evolution, including its chaoticity, and represent the backbone of cyclostratigraphy and astrochronology. An absolute, fully calibrated astronomical time scale has hitherto been hampered beyond ~50 million years before the present (Ma) because orbital calculations disagree before that age. Here, we present geologic data and a new astronomical solution (ZB18a) showing exceptional agreement from ~58 to 53 Ma. Read More

Nat Commun 2018 10 1;9(1):4007. Epub 2018 Oct 1.

Research School of Earth Sciences, Australian National University, Canberra, ACT, 2601, Australia.

Understanding marine environmental change and associated biological turnover across the Palaeocene-Eocene Thermal Maximum (PETM; ~56 Ma)-the most pronounced Cenozoic short-term global warming event-is important because of the potential role of the ocean in atmospheric CO drawdown, yet proxies for tracing marine productivity and oxygenation across the PETM are limited and results remain controversial. Here we show that a high-resolution record of South Atlantic Ocean bottom water oxygenation can be extracted from exceptionally preserved magnetofossils-the bioinorganic magnetite nanocrystals produced by magnetotactic bacteria (MTB) using a new multiscale environmental magnetic approach. Our results suggest that a transient MTB bloom occurred due to increased nutrient supply. Read More

Philos Trans A Math Phys Eng Sci 2018 Oct;376(2130)

Department of Earth Sciences, University of California, Riverside, CA 92521, USA

The Paleocene-Eocene Thermal Maximum (PETM, approx. 56 Ma) provides a test case for investigating how the Earth system responds to rapid greenhouse gas-driven warming. However, current rates of carbon emissions are approximately 10 Pg C yr, whereas those proposed for the PETM span orders of magnitude-from ≪1 Pg C yr to greater than the anthropogenic rate. Read More

Philos Trans A Math Phys Eng Sci 2018 Oct;376(2130)

School of Geographical Sciences, University of Bristol, University Road, Bristol BS8 1SS, UK.

Past global warming events such as the Palaeocene-Eocene Thermal Maximum (PETM-56 Ma) are attributed to the release of vast amounts of carbon into the ocean, atmosphere and biosphere with recovery ascribed to a combination of silicate weathering and organic carbon burial. The phytoplanktonic nannoplankton are major contributors of organic and inorganic carbon but their role in this recovery process remains poorly understood and complicated by their contribution to marine calcification. Biocalcification is implicated not only in long-term carbon burial but also both short-term positive and negative climatic feedbacks associated with seawater buffering and responses to ocean acidification. Read More

Philos Trans A Math Phys Eng Sci 2018 Oct;376(2130)

Department of Earth and Planetary Sciences, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA.

Geologically abrupt carbon perturbations such as the Palaeocene-Eocene Thermal Maximum (PETM, approx. 56 Ma) are the closest geological points of comparison to current anthropogenic carbon emissions. Associated with the rapid carbon release during this event are profound environmental changes in the oceans including warming, deoxygenation and acidification. Read More