Mtc in Salt Minibasin- Sequence Stratigraphy, Seismic Geomorphologic and Local Tectonics Aspects- a Case Study from Northern Gulf of Mexico
Salt minibasin provinces are important exploration zones in the deep water Gulf of Mexico. Although mass transport complexes (MTC) are rarely considered as primary exploration targets, they are very important in many other aspects, such as determining the depositional history and sequence stratigraphic framework of a basin and the impact they create upon overlying and underlying units. A 100 square kilometer 3D seismic dataset has been analyzed along with well logs and micropaleontologic information from a salt minibasin that falls within the tabular salt minibasin tectono-stratigraphic province (Diegel et al, 1995) of the Gulf of Mexico.
Seismic interpretation reveals that the MTCs within the minibasin are not only affected by sea level fluctuation and regional tectonics, but also by local tectonics due to salt movements. Several seismic attributes, including RMS amplitude, inline and crossline amplitude gradients, Sobel filter edge detector, coherence, most positive and negative curvature and spectral decomposition have been applied to the 3D seismic data. Stratal slices from these attributes reveal several seismic geomorphologic features within MTCs as well as within overlying and underlying strata which help to reconstruct the sequence stratigraphic framework and depositional history of the minibasin.
Attribute analysis indicates two different units within a larger MTC, each with different seismic characteristics. The lower unit might be part of a regional-scale mass flow. The upper unit is more erosive and chaotic in nature, containing some discontinuous features suggesting intensified local salt tectonics and slumping.
Salt movement produced several arcuate extensional faults within the MTC, some of which extend to shallower sequences. A few toe thrust related faults due to thrust impact of the MTC are present.
The intense tectonic activity and rapid basin fill rate during deposition of the upper unit might have changed the depositional pattern and dominant sediment transport direction as revealed by seismic attributes. Rare striations at the base of the MTC and a train of high amplitude blocks were also imaged by different attributes. Using detailed analysis of small seismic geomorphologic features within a conventional seismic data interpretation workflow augmented with well log information, we build a sequence stratigraphic framework of the minibasin with emphasis between two MTCs.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009