Diachronous Development of Late Quaternary Shelf-Margin Deltas in the Northwestern Gulf of Mexico: Implications for Sequence Stratigraphy and Deep-Water Reservoir Occurrence
John B. Anderson, 2005. "Diachronous Development of Late Quaternary Shelf-Margin Deltas in the Northwestern Gulf of Mexico: Implications for Sequence Stratigraphy and Deep-Water Reservoir Occurrence", River Deltas–Concepts, Models, and Examples, Liviu Giosan, Janok P. Bhattacharya
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For the most part, delta development across the northern Gulf of Mexico shelf during the last glacioeustatic cycle occurred throughout the falling limb of sea level. The deltas have different morphologies, sediment facies patterns, and stratigraphic architectures. Depending on the sediment supply of their fluvial feeders, these deltas reached the shelf margin at different times. The Rio Grande, Colorado, Trinity, and Sabine rivers remained fixed in their locations on the shelf throughout the late stages of sea-level fall and into the lowstand. Hence, they all formed lowstand deltas and all nourished slope fans. In contrast, the Brazos and western Louisiana rivers abandoned their shelf-margin deltas prior to the lowstand. Hence, neither the Brazos nor the western Louisiana fluvial systems have linked lowstand delta and slope fans. Because growth of the different shelf-margin deltas spans different portions of the sea-level cycle, the location of the sequence boundary and associated correlative conformity relative to the shelf-margin stratigraphic package varies from one deltaic system to the next.
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Deltas are amongst the most environmentally and economically important coastal sedimentary environments. Studies of deltas lag behind research in both fluvial and deep-water depositional systems, as well as more geomorphologically oriented land studies. This knowledge lag reflects both a reorientation of the petroleum industry in the last two decades toward deep-water systems, as well as the difficulty of working across the shoreline with the traditional tools used for oceanographic or land-based work. However, deltaic studies are experiencing a renewed focus, because of their global importance in environmental and other societal concerns. This volume stems from a special session: Deltas: Old and New, held at the Annual Geological Society of America conference in October 2002, that was convened to highlight these new directions in deltaic research.