Syndepositional Faults in Mass-Transport Deposits: Seals or Conduits to Fluid Flow?

Dykstra, Mason¹, Benjamin Kneller², Katerina Garyfalou² (1) University of California, Santa Barbara, CA (2) University of Aberdeen, Aberdeen, United Kingdom

Mass-transport deposits are typically thought of as fairly homogenous deposits with a consistency similar to wet cement, and are often thought of as seals. Extensive research on mass-transport processes demonstrates, however, that many mass-transport deposits are composed of internally undeformed coherent blocks as well as homogeneous zones, and everything in between (e.g. Locat and Mienert, 2003; Kneller and Dykstra, 2004). Within mass-transport deposits therefore, strain is accommodated in numerous ways, including by penetrative deformation of the sediment involved, as well as the development of discrete ‘faults' (semi-brittle to brittle discontinuities). The purpose of this contribution is to examine the properties of faults in mass-transport deposits, and how these properties determine the behavior of fluids in the system. Mass-transport related faults include normal, reverse, and strike-slip type faults, many of which often accommodate multiple phases and polarities of motion along them. They fall into three categories with regards to conducting fluids: coarse-sediment filled, fine-sediment filled, and welded faults. The eventual behavior of any given fault as regards fluid flow depends on the type of fill of the fault zone, and any diagenetic overprint that may result in a loss of permeability in the fault fill. We present here end-member examples of fault fills from outcrop data collected in numerous locations, and discuss the implications of these fills to fluid flow and sealing.

Locat, J. and J. Mienert, Eds. (2003). Submarine Mass Movements and Their Consequences. Boston, Kluwer Academic Publishers.

Kneller, B. and M. Dykstra (2004). The Internal Structure and External Morphology of Submarine Landslides: A Causative Link. In: AGU Annual Meeting, San Francisco, California, U.S.A.