Can Sequence Stratigraphy Co-Exist with Instantaneous Event Stratigraphy of the Talus Breccia Reservoir in the Campeche Shelf and Elsewhere in the Gulf of Mexico Basin and Beyond?

Tom Jerzykiewicz¹, Gustavo Hernandez-Garcia², Jaime Rios², Armando Garcia², Griselda Garcia², and Antonio Murillo^2
1 Teknica Mexicana, S.A. de C.V, Cd. del Carmen, Campeche, Mexico
² Pemex PEP Region Marina Noreste, Cd. del Carmen, Campeche, Mexico

Acceptance of the Chicxulub asteroid impact event implies a new approach to the stratigraphy of the breccia reservoir offshore Campeche. It is important to ask to what extent sequence stratigraphic techniques apply to a sedimentary basin affected by an extremely sudden, high-energy event. Seismic sections show significant variability of external geometry and internal architecture of the breccia stratigraphic interval. Sharply based breccia talus is strongly asymmetric between the proximal part, at the margin of Yucatan Platform, and its distal deep-marine apron. Internally, the seismic facies change from a parallel pattern of reflectors to a chaotic, intermittent pattern of very strong reflectors. The former pattern corresponds to cyclic open-shelf sedimentation whereas the latter pattern, which dominates the breccia, is interpreted in terms of episodic sediment gravity flow deposition. Seismic sections suggest that the sediment gravity flow deposits are common both at the proximal and at the distal part of the talus where the KMZ reservoirs occur. Sediment gravity flow deposits infill sharply-based channel-like incisions into the parallel-bedded facies. Some of the channels which attain large dimensions and cut deeply into the Cretaceous strata are produced by the instantaneous event. The initial conclusion is that the external geometry of the talus and the channel-fill breccia are genetically related to the Chicxulub event and do not conform to cyclic sedimentation processes. In contrast the regularly bedded substratum represents a long period of accumulation and can be correlated using sequence stratigraphic methods. Both diametrically opposing facies occur across the KMZ field and need to be taken into account in breccia reservoir characterization.

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