Identifying the physical processes that control the stratigraphic record

May 07, 2013

The stratigraphic record, the sequential layers of sediment that geologists use to reconstruct the history of a landscape, has been described as "more gaps than record." The record, laid down over time as sediment settles out from flowing water, does not grow consistently. Pauses in sediment deposition can leave gaps, and periods of heightened erosion can wipe sections out.

Though attempts have been made to identify the processes that control the completeness of the stratigraphic record, early analyses relied on parameters (such as the long-term rate) that are not first-order physical landscape processes.

Building on that earlier work, Straub and Esposito used a series of laboratory experiments to identify the physical processes that are relevant to controlling the accumulating stratigraphic record, and to determine the relationships between these processes.

The authors built a series of artificial river deltas, each with varying water flow and sedimentation rates, and used time-lapse photography and topographic measurements to track how the stratigraphic record developed.

They find that the stratigraphic record is most complete when the rate is high, when the water flow rate relative to the rate is low, and when the river channel migrates slowly across the whole delta region.

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More information: Influence of water and sediment supply on the stratigraphic record of alluvial fans and deltas: Process controls on stratigraphic completeness, Journal of Geophysical Research-Earth Surface, doi:10.1002/jgrf.20061, 2013

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