Ancient transient landscapes: expressions of dynamic topography within the stratigraphic record?
Abstract
The degree to which convective circulation of the mantle generates and maintains surface elevation is a topic of considerable debate. Recent attempts to characterize present-day convective support suggest that typical amplitudes and wavelengths are ∼ ± 1 km and ∼ 1,000 km, respectively. However, constraining spatial and temporal patterns of dynamic topography through geologic time remains a challenge. Ancient landscapes preserved in the stratigraphic record may provide a significant opportunity to investigate transient vertical motions throughout the Phanerozoic eon. Examples have been identified offshore using three-dimensional seismic reflection data (e.g. from Paleogene times along the margins of the North Atlantic Ocean) and exposed in sedimentary sequences onshore (e.g. from Paleogene times in western Greenland, the Carboniferous period in western North America). These landscapes are typically preceded and followed by marine sedimentation, and record brief periods of base-level fall, subaerial exposure, fluvial incision, and resubmergence. They are also often associated with significant perturbations to regional patterns of tectonic subsidence. Required amplitudes of transient vertical motion can preclude their cause by eustatic sea-level variation. Here, we present and analyze observations from two such ancient landscapes: from the Faroe-Shetland Basin and the Grand Canyon. By modeling the evolution of these landscapes and associated regional subsidence perturbations, we test the hypothesis that they were generated by circulation of sub-plate thermal anomalies. Our analyses indicate that many of the observations concerning the growth and decay of these ancient landscapes can be explained by variations in convective topographic support. These results suggest that transient landscapes preserved in the stratigraphic record can provide important constraints on the evolution of dynamic topography through geologic time, and have important implications for the evolution of passive margins and intracratonic basins.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMDI51B0007M
- Keywords:
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- 1031 Subduction zone processes;
- GEOCHEMISTRYDE: 8031 Rheology: crust and lithosphere;
- STRUCTURAL GEOLOGYDE: 8120 Dynamics of lithosphere and mantle: general;
- TECTONOPHYSICSDE: 8124 Earth's interior: composition and state;
- TECTONOPHYSICS