Buried Late Quaternary Fluvial Channels on the Louisiana Continental Shelf, USA

Analysis of over 20,000 km of high-resolution seismic profiles, supplemented by vibracores and platform borings, on the southwest Louisiana continental shelf has revealed extensive systems of buried channels in late Quaternary sediments. A fluvial origin of hhe channel systems is indicated by their continuity from the nearshore to the shelf break, as well as the areal pattern, and cross sectional dimensions of as much as 5 km in width and 50 m in depth. Some channels are comparable in size to, or are even larger than, those of the modern Mississippi River, and may represent former positions of this system. Established fluvial systems extend themselves acosss exposed continental shelves during periods of lowered sea level. These channels, buried during subsequent sea level rise, aid in the identification of erosional unconformities and thus in determining sea-level history. Channel systems on the southwest Louisiana continental shelf have been recognized at five different levels, representing regressive periods that are interpreted to range from pre-Wisconsianan to Holocene in age. Sediments contained within the channels and associated estuarine deposits make up a substantial part of the shelf stratigraphy. The extent and size of these features illustrate the significance of fluvial channels and associated facies in the stratigraphy of continental shelves influenced by fluctuating sea levels.