Regional Geology of Nuclear Central America and Petroleum Prospects of Belize

R. Rao Prasada, K. M. Nair, R. Ramanathan

The subsurface stratigraphy and structural evolution of nuclear Central America are reviewed in the light of new data from Belize. The northern Belize Corozal basin is the southern continuation of the Yucatan platform of Mexico and the eastern extension of the Peten basin of Mexico and Guatemala. The southern Belize basin is contiguous with the Chapayal basin of Guatemala.

The sedimentary cover in the thickest part of nuclear Central America is over 12,000 m (40,000 ft) thick. The oldest sedimentary rocks are the upper Paleozoic carbonates and clastics associated with metasediments and igneous intrusives. Although Triassic through Lower Jurassic red beds and evaporites are restricted to some parts, the Upper Jurassic to Lower Cretaceous rocks are widespread and constitute the main source for hydrocarbons. Cretaceous rocks make up the bulk of the carbonate-evaporite complex of this province and account for the Mesozoic reservoir and seal. Tertiary rocks are essentially clastic and continental to marine along southeastern Mexico and grade laterally into a carbonate sequence over the Yucatan platform.

The Yucatan Peninsula could be divided into the northeastern part, which has a regional gravity high, and the southwestern part, with a gravity low. The gravity high is the Yucatan platform, whereas the gravity low is the Peten basin. In southeastern Mexico the Peten and Chapayal basins are separated by a gravity high in the Reforma-Campeche area. In Belize and central Guatemala, again there is an east-west gravity high which coincides with the Maya Mountain--Libertad arch that separates the Peten and Chapayal basins.

In Belize, organic-rich thin, black shales have been encountered within the Tertiary and Upper and Lower Cretaceous of the Corozal basin. These rocks would thicken basinward and the organic material could be rich in the depocenters. Maturity has been reached at shallower depths in some wells than in others. If adequate organic matter, maturity, local migration, migration fairways (depositional and tectonic), and trapping mechanism exist on the margins of depocenters, chances of finding commercial accumulations are very good. The types of traps expected in the Corozal basin are normal fault closures and pinch-out of dolomites, whereas in the Belize basin, especially offshore, subthrust prospects are likely to be present.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.