Small-Scale Mantle Convection Produces Stratigraphic Sequences in Sedimentary Basins

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Science  13 Aug 2010:
Vol. 329, Issue 5993, pp. 827-830
DOI: 10.1126/science.1190115

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Changes in the Rocks

Changing sea level or major tectonic events, such as continental collisions, shift stratigraphic sequences by changing the depositional environment where certain rock types form. For example, a deep marine environment where limestone formation is favored may shift relatively quickly to a near-shore environment favoring sandstone formation because the relative sea level has dropped several meters. Petersen et al. (p. 827; see the Perspective by Müller), however, suggest that small-scale convection in the mantle may also induce appreciable changes in the sequence of sedimentary deposits. Using a modeling approach, they found that this is possible on a small scale (that is, just a few hundreds of kilometers) over variable time scales. Thus, while the co-occurrence of sedimentary deposit sequences at regional and global scales can allow sedimentary rocks to serve as markers of marine environments, it should be kept in mind that local changes in surface movements may also manifest themselves in the rock record.


Cyclic sedimentary deposits link stratigraphic sequences that are now geographically distant but were once part of the same depositional environment. Some of these sequences occur at periods of 2 to 20 million years, and eustatic sea-level variations or regional tectonic events are likely causes of their formation. Using numerical modeling, we demonstrate that small-scale mantle convection can also cause the development of stratigraphic sequences through recurrent local and regional vertical surface movements. Small-scale convection-driven stratigraphic sequences occur at periods of 2 to 20 million years and correlate only at distances up to a few hundred kilometers. These results suggest that previous sequence stratigraphic analyses may contain erroneous conclusions regarding eustatic sea-level variations.

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