AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Seismic Stratigraphic and Seismic Geomorphologic Study of Mass Transport and Sediment Wave Deposition, Offshore Eastern Canada
(1) ETC, Chevron Energy Technology Company, Houston, TX.
(2) Chevron N.A. Exploration Production Co., Houston, TX.
(3) Chevron Australia Pty Ltd, Perth, WA, Australia.
Extensive mass transport deposits characterize the Tertiary deep-water depositional environment, offshore eastern Canada. These deposits are characterized using techniques of seismic stratigraphy and seismic geomorphology, and 3D seismic visualization. A variety of mass transport attributes can be directly imaged and interpreted; these include extensive grooving and erosion at the base of these deposits, localized “substrate plucking”, and extensive extensional faulting indicative of detachment. Some mass transport deposits are underlain by countless tightly-spaced erosional grooves. Individual grooves can be traced for tens of kilometers. Some grooves are in excess of 10-20 meters deep and up to 200 meters wide. Locally, a phenomenon of localized “substrate plucking” can be observed. This process results in circular- to elliptically-shaped divots taken out of the substrate in association with the passage of mass flows. These divots, which are completely ringed by vertical walls up to 75 meters high, can be as large as 1-2 km2. It is common to observe transverse, nearly-vertical faults marking the up-system limits of many of these mass transport deposits, suggesting detachment of substrate sediments that are subsequently incorporated into the mass flow. Similarly, flow-parallel, nearly-vertical faults are common and mark the lateral edges of some of these mass transport deposits. Internally, the seismic expression of the mass transport deposits is chaotic to transparent. Individual mass transport deposits reach thicknesses of greater than 250 meters and can amalgamate to form significantly thicker mass transport complexes.
Extensive sediment wave fields are observed within the deep-water Tertiary section. These sediment waves cover areas measurable in 10’s of km2 and are characterized by relief of up to 150 meters. The wavelength of these features is 1600-2100 meters. In map view, they are observed to be linear and in section view are characterized by a climbing architecture with wave crests inferred to be migrating in the upflow direction. In detail, it is observed that the wave crest migration direction is oblique to the direction of wave accretion. In places these sediment waves can comprise an amalgamated thickness of over 500 meters.