Source-to-Sink: The Importance of the Updip Coastal Area in Defining Deep-Water Sand Characteristics
Arnold H. Bouma, Erik D. Scott, 2013. "Source-to-Sink: The Importance of the Updip Coastal Area in Defining Deep-Water Sand Characteristics", Shelf Margin Deltas and Linked Down Slope Petroleum Systems–Global Significance and Future Exploration Potential, Harry H. Roberts, Norman C. Rosen, Richard H. Fillon, John B. Anderson
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Understanding the interactions of the source-to-sink sedimentary system is necessary to place a deposit in a receiving basin in its proper depositional perspective. This is true for any part of the source-to-sink system, whether it deals with fluvial, deltaic, shelf, slope, or deepwater, especially when the sink is now in the subsurface. One should look updip as well as down-dip to understand better the environment of interest. Critical information to classify the variety of submarine fans, such as the range of grain size and the distribution of sand, can be found in the time-equivalent deltaic environment at the shelf margin.
Four major factors can be identified that influence all parts of the source-to-sink system: tectonic activity, climate, relative sea level fluctuations, and sediment characteristics. Tectonic activity, both local and regional, comprises the primary factor. Pre-depositional tectonic movements guide the location and elevation of the sediment-providing mountains, climatic conditions for weathering and precipitation, types of subaerial transport, development of the coastal plain and its delta (if any), the shelf width, slope characteristics, and the receiving deep-water basin characteristics. Climate influences several attributes, including sea level fluctuations and sediment transport to the coast and beyond. Sea-level fluctuations, controlled by large-scale tectonic activity and/or climatic changes, influence subaerial and coastal processes. During rising, high relative, or global sea level, coastal plains become submerged and sediments are stored on the continent and the shelf. During the lowering and initial rising stages, sea level can result in shelf-edge deltas or the feeding of sediment directly to a deep-water basin. The maturity of the sediment is strongly influenced by the type and duration of subaerial transport, where the majority of the mechanical and chemical weathering takes place. During subaqueous transport, significant amounts of clay-sized sediment facilitate transport of fine-grained sands far into the ocean basins.
Whether deep-water sediments are coarsegrained or fine-grained, the coastline dictates if the feeding sediment source is canyon-fed or delta-fed. Shelf margin deltas are typical for fine-grained sediment and are normally located on wide, low-gradient shelves. Lateral switching of the delta establishes a new location for the entry point of the sediment to a deep-water basin. Shelf margin deltas on narrow shelves do not always exist during low sea-level periods.