Shelf and Shelf-Margin Growth in Scenarios of Rising and Falling Sea Level
Ronald J. Steel, Cristian Carvajal, Andrew L. Petter, Carlos Uroza, 2008. "Shelf and Shelf-Margin Growth in Scenarios of Rising and Falling Sea Level", Recent Advances in Models of Siliciclastic Shallow-Marine Stratigraphy, Gray J. Hampson, Ronald J. Steel, Peter M. Burgess, Robert W. Dalrymple
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The topset and slope components of aggrading and accreting shelf-margin prisms, and the role of deltas in margin growth, are reviewed. Shelves are constructed by the repeated regressive-transgressive transits of deltas and other shoreline systems on the shelf platform, and when these sediment-delivery systems reach the edge of a preexisting shelf there may be significant accretion of the margin. Regressing deltas/strandplains and transgressing estuaries/barriers can be variably influenced by waves, tides, or river currents, and the presence/distribution of these processes can change in space and time on the shelf platform, and sometimes systematically in cross-shelf transits. The modeled transit time for modern deltas that are able to cross their shelves completely is surprisingly short, usually less than 100 ky. The separation between deltas that are unable or are able to make the entire transit when sea level is rising moderately (2. 1 m/ky) allows accommodation-dominated delivery systems (those that require sea-level fall to force the cross-shelf transit) and supply-dominated systems (those that can cross the shelf even with rising sea level) to be distinguished. These end-member systems, in turn, become important in the rationale for arguing a distinction between the conventional falling (lowstand) relative sea-level model for shelf-margin growth and turbidite accumulations, and a model that delivers deepwater sands with normal regression and rising relative sea level at the shelf margin. The differing deepwater architectures for these two models are outlined.
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Siliciclastic shallow-marine deposits record the interface between land and sea, and its response to a variety of forcing mechanisms: physical process regime, the internal dynamics of coastal and shelfal depositional systems, relative sea level, sediment flux, tectonic setting, and climate. These deposits have long been the subject of conceptual stratigraphic models that seek to explain the interplay between these various forcing mechanisms, and their preservation in the stratigraphic record. This volume arose from an SEPM research conference on shoreline–shelf stratigraphy that was held in Grand Junction, Colorado, on August 24–28, 2004. The aim of the resulting volume is to highlight the development over the last 15 years of the stratigraphic concepts and models that are used to interpret siliciclastic marginal-marine, shallow-marine, and shelf deposits.