Description of the facies associations permits definition of sedimentary processes beginning on the continental terrace and following them through the deep-sea-fan system and distally to basin plain and/or deep-sea channels. After summarizing factors that control deep-sea-fan depositional patterns, we will describe three examples of basic end-member types of debris apron and fans. Seismic stratigraphy, lithology, and depositional facies plus process models will be presented for each end-member example. These end-member patterns will be compared with past models and utilized to define fan development in complex basin and trench environments.
As outlined in Chapter 3, the formation of sediment gravity flows and subsequent turbidity currents takes place through two general mechanisms, slope failure or storm-wave generation associated with canyon heads. On the open slope, mass transport processes are the norm (Table 3-1, Fig. 7-1), and these often continue onto the proximal region of debris aprons (Fig. 6-2). When energy and amount of material are sufficient, these flows will evolve into turbidity currents that deposit thick or thin mud or sand layers in the distal regions of debris aprons. These sheet-flow turbidites may extend onto local basin plains (Fig. 6-2). In very large slope failures, the entire mass-transport process will deposit debris sheets across significant portions of large fans (Fig. 7-2).
Headward slope erosion by slumping probably initiates the formation of submarine canyons and this process continues to be important along canyon walls and tributaries throughout canyon history (Fig. 7-1) (Farre et al., 1983). Once an initial canyon has formed by mass-transport