Marine Techniques

Abstract A number of modern marine geologic techniques are available for the study of modern deep-sea fan environments. These techniques fall into several basic categories, including (1) acoustic techniques to map the sea-floor bathymetry, the sea floor surface, and define subsurface acoustic reflectors, (2) surface and subsurface sampling techniques, and (3) methods to assess environmental parameters of deep-sea-fan deposition. Modern environmental conditions can be assessed using current meters, suspended sediment measuring devices, and biological sampling techniques. General morphology of deep-sea fans can be studied by echo sounding techniques, TV cameras with videotape recording, and bottom photography (Fig. 2-1). Deep-sea-fan stratigraphy and lithology can be studied by continuous seismic profiling, coring, and deep-sea drilling. These techniques have been used to understand the near-surface environment and sedimentary processes of modern deep-sea fans. Although we know near-surface facies for different modern fan environments, the lateral and vertical continuity and three-dimensional lithofacies of modern systems is poorly known. This results in the lack of an adequate data base to make good comparisons of the modern deep-sea-fan environments with comparable information from ancient deep-sea fan rock sequences. Echo-sounding techniques (3.5-12 kHz) have been used for several decades to define submarine bathymetry and outline deep-sea fans, fan valleys, and deep-sea channels (Fig. 2-lA) (Menard, 1955). At the lower frequencies, there often is some subsurface penetration as well as the collection of accurate bathymetric profiles. Recently, SEABEAM, a multi-beam precision echo-sounding techniques coupled with onboard, real-time processing and generation of bathymetric charts has been applied to submarine canyon