Evolution of a Submarine Mass-Transport Complex in Space and Time

Abstract

Submarine mass-transport deposits (MTDs) can be petroleum reservoirs, drilling hazards, or indicators of seafloor instability that need to be considered in deep-water engineering projects. In 3-D seismic reflection data, MTDs are typically characterized by laterally extensive but relatively thin layers of debris with weak and incoherent reflectors and, in many cases, little or no seafloor geomorphic expression. Because of their great lateral extent, it is unusual to see proximal and distal portions of large MTDs in a single data set. We infer that spatial variation in the geometry of a large and exceptionally well-imaged MTD can serve as a proxy for the temporal evolution of the mass transport event at a point. Near its source, the MTD is characterized by disaggregation of originally intact strata. As distance from the source increases, the complex becomes increasingly chaotic the manifestation of the original structure weakens. Each facies also has a characteristic seafloor geomorphologic expression. The spatio-temporal evolution is particularly evident when the fabric is visualized using 3-D seismic volume amplitude attributes that display the lateral continuity of reflectors.