CRETACEOUS PALEOGEOGRAPHY,

CRETACEOUS PALEOGEOGRAPHY, FORAMINIFERAL BIOSTRATIGRAPHY AND PALEOECOLOGY OF BELIZE BASIN, BELIZE

R. RAMANATHAN and E. GARCIA
Petroleum Office, Mm. of Natural Resources,
34136 Unity Boulevard, Belmopan, Belize

Foraminiferal micropaleontological studies carried out on drilled samples from exploratory wells drilled for petroleum in southern and offshore Belize, confirm that this area is contiguous with the South Peten basin of Guatemala. It is recognized as the Belize Basin and accounts for more than 16,000 ft. of Mesozoic and Cenozoic sediments.

Four planktonic foraminiferal assemblage zones have been recognized within the Cretaceous. They are, Hedbergella planispira Assemblage for ?Aptian - Albian, Rotalipora Assemblage for Cenomanian, Globotruncana linneiana - G. fornicata Assemblage for Campanian and Globotruncana stuartiformis - G. contusa Assemblage for Maastrichtian.
The earliest marine transgression within the Mesozoic in the Belize Basin is dated as? Aptian -Albian based on foraminiferal evidence. The predominant lithofacies is shallow marine carbonates associated with lagoonal anhydrites which are classified under the Coban Formation. Development of NE - SW trending ridges and troughs during Late Albian - Early Cenomanian and again during Late Campanian and Maastnchtian accounts for Campur carbonates deposited under shallow marine environment and Toledo turbid tes under deep sea conditions.
Two episodes of oxygen deficient bottom conditions are documented within the Cretaceous which resulted in the deposition of grey-black shales during Late Albian - Early Cenomanian and Late Campanian. These shales seem to be related to an expanding oxygen minimum layer within the adjoining oceanic waters and correlates well with the major global transgressive events.

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