3 September 2019

Breakthrough to unlock earth’s geologic archives

Astronomical timescale extended by eight million years

Earth scientists from Utrecht University and University of Hawai’i have extended the astronomical time scale by 8 million years. Their new chronology also reveals a new age for the Paleocene-Eocene boundary at 56 million years ago. Additionally, the authors propose an orbital trigger for the onset of the Paleocene-Eocene Thermal Maximum (PETM). Their results were published in the prestigious Science journal.

A couple of the studied drilling cores.

Earth scientists use an astronomical time scale, based on the movements of planets and the sun in our solar system, to study and explain the geological history of the earth. The astronomical calendar of the past provides, amongst others, ages of geologic periods based on astronomy. However, the astronomical time scale does not reach beyond 50 million years, because of disagreeing orbital calculations.

The new breakthrough by Prof Lucas Lourens from Utrecht University and Richard Zeebe from the University of Hawai’i overcomes this obstacle by using geological records to constrain an astronomical chronology. An analysis of deep-sea drill cores from 53 to 58 million years old was used to compare an independently calculated astronomical chronology. The data from the drill cores and the calculated chronology shows exceptional agreement with each other. The new methodology of using climate records to infer the astronomical time scale potentially allows even further extension of the astronomical time scale, unlocking earth’s geological archives step by step.

Data analysis and comparison of deep-sea cores to calculated astronomical solution. Source: Science
Data analysis and comparison of deep-sea cores to calculated astronomical solution. Source: Science

Orbital trigger

The new astronomical time scale also provides a new age for the Paleocene-Eocene boundary at 56 million years, with a small margin of error (0.1%). The authors furthermore show that the onset of a large ancient climate event, the Paleocene-Eocene Thermal Maximum (PETM), occurred near an eccentricity maximum. This suggests that an orbital trigger began this period of extreme global warming.

The study also has implications for astronomy. The new study shows unmistakable fingerprints of solar system chaos around 50 million years ago.

Article

Solar System chaos and the Paleocene–Eocene boundary age constrained by geology and astronomy
Richard E. Zeebe, and Lucas J. Lourens
Science 365 (6456), pp. 926-929