Eustasy, its controlling factors, and the limno-eustatic hypothesis – concepts inspired by Eduard Suess
- Autor(en)
- Michael Wagreich, Richard Lein, Benjamin Sames
- Abstrakt
For many years Eduard Suess dealt with the phenomenon of displaced shorelines and the search for explanations for their genesis and the controlling factors. In the year 1888 Suess introduced the term eustatic movements referring to the global synchroneity of marker events in marine successions of the Earth history. Since the times of Suess, rapid scientific progress has considerably widened our understanding of the processes involved in changing sea levels. Eustasy now describes global sea-level changes that play a major role in controlling the development, structure and distribution of marine sedimentary successions. Relative (regional and local) and global (eustatic) sea-level fluctuations are controlled by a variety of endogenic and exogenic processes. Mantle convection and resulting gravity anomalies and tectonism, and climate changes are the main drivers, and apply at different temporal and spatial scales. The long-term sea-level record, i.e. 1
st to 2
nd order cycles and stratigraphic sequences, occurring over millions to tens of millions of years, is mainly controlled by the internal dynamic history of the Earth, e.g., the changing rates of ocean crust production. Short-term eustatic sea-level changes during ice house phases of Earth's climate are clearly controlled by waxing and waning of continental ice sheets. However, significant short-term, i.e. 10s kyr to a few Myr (3
rd to 4
th order cycles), sea-level changes during greenhouse episodes of Earth history are still enigmatic. Such cycles are often explained by the presence of ephemeral ice sheets even during the hottest greenhouse phases ("hothouse periods") of the Phanerozoic climate history such as the mid-Cretaceous. We argue that the effect of groundwater storage and release on sea-level change, particularly important during ice-free greenhousephases, has been and is 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 storage, including both freshwater and saline pore waters, strongly exceeds lake and river storage capacities. We introduce the term "limno-eustatic" to describe the effect of water volumes that are bound to groundwater and lake storage on sea-level fluctuations and cycles during major greenhouse phases of Earth history. Based on these terms the dimension of purely ice-driven glacio-eustatic processes can be better differentiated. The limno-eustatic hypothesis may be testable given high-resolution stratigraphic correlations between marine and continental lake archives during supposed ice-free periods of Earth history. Lake-level and sea-level fluctuations should be in an out of phase relation, i.e. a major marine sea-level lowstand should correspond to a lake-level highstand, and vice versa. Preliminary tests using selected stratigraphic levels of the Late Cretaceous record of the long-lived lacustrine Songliao basin in China indicate such an outof- phase relation, and thus support the limno-eustatic hypothesis as a mechanism to explain significant short-term sea-level fluctuations during greenhouse climate phases.
- Organisation(en)
- Institut für Geologie
- Journal
- Austrian Journal of Earth Sciences
- Band
- 107
- Seiten
- 115 - 131
- Anzahl der Seiten
- 17
- ISSN
- 0251-7493
- Publikationsdatum
- 2014
- Peer-reviewed
- Ja
- ÖFOS 2012
- 105106 Geodynamik, 105110 Geschichte der Geologie, 105123 Stratigraphie
- Schlagwörter
- ASJC Scopus Sachgebiete
- Geology, Palaeontology, Stratigraphy
- Link zum Portal
- https://ucrisportal.univie.ac.at/de/publications/f0c5161b-1494-4e70-8439-0c51df9a905b