Unravelling short-term climate and sea-level changes in the Cretaceous greenhouse world: The concept and contribution of aquifer-eustasy

Description

In contrast to glacial eustasy controlled mainly by waxing and waning of continental ice sheets, short-time sea-level changes during major greenhouse episodes of the Earth history are still poorly understood, and are often explained by the presence of ephemeral ice sheets even during extreme ‘hothouse’ phases such as the mid-Cretaceous. However, the possible effect of groundwater storage and release on sea-level change has been widely underestimated in its order of magnitude. It is considered to constitute a water volume that is about equivalent to today’s ice volume, thus corresponding to a potential sea-level change of up to ca. 50 m, applying isostatic adjustment. Groundwater aquifer storage, including both freshwater and saline pore waters above sea level, exceeds lake and river storage capacities by several orders of magnitude.
Evidence for aquifer-driven eustatic cycles during supposed ice-free periods of the mid-Cretaceous come from wet-dry weathering cycles and high-resolution stratigraphic correlations between marine and continental lake archives, i.e., lake-level and sea-level fluctuations that are recorded in an out-of-phase relation in such a way that a major marine sea-level low-stand corresponds to a lake-level high-stand (i.e., water ‘removed’ from the sea and stored on the continents), and vice versa. Tests using the Turonian to Campanian Late Cretaceous record of the long-lived lacustrine Songliao basin in China indicate such an out-of-phase relation, and thus support this hypothesis.
The lecturer has been collaboratively involved in some major contributions concerning the concept and application of aquifer eustasy in the Cretaceous in the last decade, which will be part of the presentation.

The talk will cover
1) the fundamentals and theoretical background of the concept of aquifer-eustasy,
2) recent proof of aquifer eustasy, and evidence for it in the geologic record,
3) the contribution of aquifer-eustasy to short term sea-level changes in Earth history, especially during greenhouse/hothouse phases,
4) the impact of the consideration of the process of aquifer eustasy on the interpretation of past short-term climate and sea-level changes focusing on the Cretaceous including potential applications,
5) and, finally, the current state of research and critical discussion of the concept.

Period	29 Nov 2022
Held at	Petrobras, Brazil
Degree of Recognition	Local