Mass Transport Deposits in Deepwater Outcrops: Depositional Setting(s), Types, and Recognition

Tor H. Nilsen¹, Roger Shew², Gary S. Steffens³, and Joseph J. R. Studlick^4
1 Consulting Geologist, CA
² University of North Carolina at Wilmington/Consulting Geologist, Wilmington, NC
³ Shell International Exploration and Production, Houston, TX
⁴ Consulting Geologist, Houston, TX

Deepwater outcrop and subsurface studies often concentrate exclusively on the architectural elements (channels, sheets, and thin beds) that would contribute directly to hydrocarbon production. However, the occurrence of non-reservoir mass transport deposits may play a significant role in the overall external and internal geometries, as recognized at the seismic scale, as well as on the internal reservoir complexity and resultant connectivity/producibility of the reservoir. A compilation of a large number of outcrop studies gathered from around the world for the AAPG Atlas of Deepwater Outcrops illustrates that mass transport deposits are both common and that they occur in most every depositional setting. Their breadth of occurrence (submarine canyons to basinal deposits) is matched by their variety of geometries (mounded to sheet-like) and properties (chaotic, slumped, and heterogeneous deposits of mudstones to matrix supported conglomerates). Recognition of their occurrence and properties provides further critical information for understanding and modeling the subsurface environment. A summary of the non-reservoir mass transport examples and their statistics will be presented.