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Influence of point-source sediment-supply on modern shelf-slope morphology: implications for interpretation of ancient shelf marginsNormal access

Authors: C. Olariu and R.J. Steel
Journal name: Basin Research
Issue: Vol 21, No 5, October 2009 pp. 484 - 501
DOI: 10.1111/j.1365-2117.2009.00420.x
Organisations: Wiley
Special topic: Trajectory Analysis in Stratigraphy
Language: English
Info: Article, PDF ( 3.62Mb )

Present sea- £oor bathymetry indicates that the continental- shelf and shelf-break morphology have some unique and predictable characteristics in areas with andwithout high sediment supply. Using a global bathymetry dataset in open shelf areas in front of rivers that discharge over 25 x 10 6 tons of sediment per year, five distinct accretionary types of shelf-break are distinguished based on alongshelf gradient variability and inferred shelf-break trajectory. Morphological characteristics of rivermouth shelves (compared with adjacent areas lateral to the immediate fairway of the river) are: (1) an overall lower gradient and greater width, and (2) a relatively high slope gradient/shelf gradient ratio. The exceptions are shelves with active shelf-edge deltas; these are narrower, steeper and have an attenuated shelf break in front of rivers.These observations are at seismic scale and have direct implications for the recognition and positioning of principal cross- shelf, supply fairways on ancient shelves or shelfmargins, and therefore the potential by-pass routes for deepwater sands. Higher slope/shelf gradient ratios in areas of actively accreting margins, where the shelf-break is more prominent and easier to recognize on seismic data compared with adjacent areas, predict areas with high sediment supply. Along- strike morphological changes on supply-dominated shelves suggest that identification of the sediment-feed route and depocenter relative to the shelf break during a relative sea level cycle are critical for understanding/predicting the 3-D architecture of the shelf- slope-basin floor clinoform.

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