Duchesne, Mathieu Jacques¹, Bernard François Long¹
(1) National Research Scientific Institute, Quebec City, QC

ABSTRACT: Effects of Different Delta Types on Continental Slope and Deep-Sea Fan Sedimentary Architecture Genesis in a Relative-Sea-Level Fall/Lowstand Context: Examples from the Manicouagan Peninsula, Canada

The Manicouagan Peninsula corresponds to a lowstand deltaic plain lying in a pseudo-shelf-edge position along the Laurentian Channel in the St. Lawrence Estuary, Canada. The peninsula is surrounded by three main rivers which have contributed to the deltaic prism construction during the last glacial retreat by supplying their own delta. This system represents a perfect analogue for continental margin settings and therefore for the study of impacts of different delta types on continental slope and deep-sea fan sedimentary architecture. Because this analogue is located in water depths averaging 350 m, the resolution of the study has been enhance by one order of magnitude in comparison with similar systems located in deeper marine settings. Seismic and multibeam data have showed that each of the three delta displays a different construction style; i.e. wave-influenced, river-dominated and river-dominated/wave-influenced. These data have also highlighted the influence of the relative-sea-level fall and the following lowstand context as well as the shelf width on the exportation nature of the deltas. The three river estuaries correspond to by-pass zones where sediments are exported on the shelf and than on the basin floor by mass wasting events or directly on the basin floor via channels which feed a submarine fan. The results contributed 1) to document the evolution of a shelf-edge deltaic prism in a relative-sea-level fall/lowstand context, 2) to identify the different stages of construction and 3) to observe the influence of the different delta styles on channel types and submarine fans architecture.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.