On present-day deep-sea fans there are two kinds of stratigraphic information aside from late Pleistocene and Holocene stratigraphy from near-surface piston cores: (1) that from acoustic signatures on seismic profiles, and (2) that from Deep Sea Drilling Project (DSDP) drill holes. The former data set often lacks confirmation of reflector age by drill samples and the latter data set provides no consistent pattern of drill hole stratigraphy on any one fan. Fortunately, some high-resolution seismic stratigraphy can be correlated with near-surface piston cores (Fig. 2-3). Realizing these limitations, this section begins with a general summary of acoustic stratigraphy on fans and associated environments. Following this, the general age, thickness, stratigraphy and sedimentation rates on fans will be discussed.
The open continental slope environment normally borders one or more sides of deep-sea fans. Slides or slumps can be mapped acoustically on upper- or mid-slope regions of unstable slope environments (Fig. 5-1) (Field and Edwards 1980; Nardin et al., 1979a). Debris aprons of mass-transport deposits with chaotic acoustic signatures characterize the base-of-slope regions of unstable open slopes (Figs. 5-1 to 5-3). When canyons are present, a complex mosaic of debris aprons and small deep-sea fans can be mapped in restricted basins (Fig. 5-3).
Individual slide, slump and debris-flow events in the surface and subsurface of slope and other areas are readily mapped by side-scan sonar (Figs. 4-6 and 4-18), high-resolution echo character (Fig. 2-3), and seismic profiles (Figs. 2-4, 5-1 and 5-2). Grids of seismic profiles exhibiting rotated blocks and incoherent reflectors
Figures & Tables
This course of modern and ancient deep-sea fan sedimentation provides the framework for understanding the morphology, physiography, geometry, depositional processes and reservoir potential of deep-sea fan deposits. Focus is chiefly on the principles that control fan sedimentation and the resultant morphology of fans deposited in various types of settings. Through the comparison of modern and ancient examples of deep-sea fan sedimentation, the authors hope to increase understanding of the principal characteristics of fans. The course is divided into four parts (1) the Introduction, which covers the organization of the course and history of fan studies, (2) modern deep-sea fan deposits, (3) ancient deep-sea fan deposits, and (4) the synthesis, in which the results of the separate modern and ancient examinations of deep-sea fan deposits are synthesized into models that may be applicable to petroleum exploration.