Extreme carbonate super-saturation of the ocean and Neoproterozoic ice ages
Abstract
In the modern ocean, reduction in carbonate deposition on the continental shelves can be compensated for by the increased preservation in deep sea sediments of biogenic carbonate originating from planktic calcifiers living in the open ocean. The result is that ocean carbonate chemistry is strongly buffered and the carbon-climate system relatively stable. However, before the advent of metazoan biomineralization in the Cambrian and proliferation of calcareous plankton during the Mesozoic, carbonate deposition would have been largely restricted to shallow water photic environments. Such a system is highly susceptible to positive feedback between sea level fall, reduced shallow water carbonate deposition, increased carbonate saturation of the ocean, atmospheric CO2 draw-down, and ice-sheet growth. This is consistent with the occurrence of ice ages of near-global extent during the Neoproterozoic. Both the widespread occurrence and observed thickness of `cap' (dolostone) carbonate deposited during postglacial transgression are explicit predictions of this hypothesis. The enigmatic cap facies thus record the rapid removal of accumulated alkalinity from an ocean that has reached an extreme degree of carbonate super-saturation by the end of the glacial period.
- Publication:
-
AGU Spring Meeting Abstracts
- Pub Date:
- May 2004
- Bibcode:
- 2004AGUSM.U22A..01R
- Keywords:
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- 1620 Climate dynamics (3309);
- 4806 Carbon cycling;
- 9619 Precambrian