Print this pageAAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
A New Depositional Model for the Chicontepec Basin, Onshore Eastern Mexico
(1) Earth and Atmospheric Sciences, University of Houston, Houston, TX.
(2) Cossey and Associates Inc., Durango, CO.
The Paleocene and Eocene Chicontepec Basin of eastern Mexico has been a topic of interest to geologists ever since a large “paleocanyon” was discovered in the subsurface to the west of Poza Rica. Previous models have been unsuccessful in explaining over 600 meters of erosion in the canyon, where in places the Tertiary unconformably overlies the Jurassic. Some authors have suggested that a lowering of sea level in the Gulf of Mexico was responsible for causing the erosion. Recent detailed outcrop work, including detailed age dating and paleocurrent measurements, suggests the basin-floor topography consisted of several depositional barriers or sills which reflected turbidity currents in the Paleocene. These sills also correspond to faulting and offset of the Cretaceous/Tertiary outcrop contact in the western margin of the basin. One of these sills existed in the area west of Poza Rica, suggesting that the subsurface “paleocanyon” may have been created by erosion after the "fill" of the final basin barrier and "spill" into the next sub-basin.
In the Paleocene, there is no evidence for the existence of a contemporaneous shelf in the basin, but there is paleocurrent evidence for an entry-point in the far northern part of the basin (here named the Tanlajas Canyon) which fed sediments axially into the basin. Dramatic changes occurred in the basin in the Eocene, at about 50 Ma when a shelf developed on the western flank of the basin. Once this shelf developed, at least three canyons formed on the west side of the basin, feeding in sediments laterally rather than axially. Outcrop evidence includes Eocene sediments directly overlying the Cretaceous in the western part of the basin. Although the outcrops are highly vegetated, large-scale slumps and submarine channel sequences have been documented in the area of these Eocene canyons.