Sedimentary Characteristics of Mass Transport Deposits

Efthymios K. Tripsanas, Kimberley A. Jenner, and David J. W. Piper
Geological Survey of Canada (Atlantic), Dartmouth, NS

One hundred and ten sediment cores from the continental slopes of the northwest Gulf of Mexico and the eastern Canadian margin were studied to determine the sedimentary characteristics of mass-transport deposits (MTDs). MTDs consist of six sedimentary facies: I) inclined stratified sediments (0.3-7 m thick), II) folded sediments (0.1-6 m thick), III) clast-supported mud-clast conglomerate (0.2-4 m thick), IV) matrix-supported mud-clast conglomerate (0.1-5 m thick), V) diamicton (0.05-0.4 m thick), and VI) sorted sand-gravel deposits (0.05-0.7 m thick).

These MTD facies occur either alone or in combination forming the following types of MTDs: 1) facies I, characterizing local scale failures including creep, rotational slumping and sliding; 2) alternations of facies II and I, comprising either slump or slide deposits or rafted and/or out-runner sediment blocks; 3) facies III, representing debris-avalanche deposits; 4) alternations of facies III, IV, II, and I, characterizing large-scale debris-flow deposits; 5) Facies IV representing deposits of smaller and lower-viscosity debris flows; 6) facies V, usually overlying type 2, 3, and 4 MTDs and representing transitional flows between cohesive debris flows and grain flows; and 7) facies VI, usually occurring above type 2, 3, 4, and 6 MTDs and deposited from high-concentration turbidity currents.

The morphologic distribution of the MTD types is indicative of the mobility of the different transport processes. MTDs of types 1 and 6 occur primarily on the continental slope; types 2, 3 and 4 occur at the base of slope and on the continental rise or basin floor; and types 5 and 7 MTD's occur mainly on the basin floor.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005