Sheet-crack cements in Marinoan (635 Ma) cap dolostones as regional benchmarks of vanishing ice-sheets.
Sheet-crack cements and coextensive intrastratal folds and breccias occur in a stratigraphically controlled, meter-thick zone, near the base of Marinoan (635 Ma) cap dolostones in slope settings. We demonstrate that sheet-crack cements on the margins of the Congo and Kalahari cratons are localized a...
| Published in: | Earth and Planetary Science Letters |
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| Main Author: | |
| Format: | Article in Journal/Newspaper |
| Language: | English |
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Elsevier
2010
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| Subjects: | |
| Online Access: | http://nrs.harvard.edu/urn-3:HUL.InstRepos:8141467 https://doi.org/10.1016/j.epsl.2010.10.027 |
| Summary: | Sheet-crack cements and coextensive intrastratal folds and breccias occur in a stratigraphically controlled, meter-thick zone, near the base of Marinoan (635 Ma) cap dolostones in slope settings. We demonstrate that sheet-crack cements on the margins of the Congo and Kalahari cratons are localized at a turbidite-to-grainstone transition, which records a transient fall in relative sea-level, preceding the larger glacioeustatic transgression. Sheet-cracks opened vertically, implying that pore-fluid pressure exceeded lithostatic pressure. When the margin of an ice-sheet retreats from a coast, a net fall in sea-level occurs in the vicinity, because of the weakened gravitational attraction between the ice-sheet and the nearby ocean. Augmented by glacioisostatic adjustment (postglacial rebound), the early regional fall in relative sea-level can mask the simultaneous rise in global mean sea-level caused by the addition of meltwater. We propose that sheet-cracks and related structures in Marinoan cap dolostones manifest pore-fluid overpressures resulting from rapid sea-level falls in the vicinity of vanishing ice-sheets. Earth and Planetary Sciences Proof |
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