Abstract: Chronostratigraphic Charts of the Eastern Venezuela Basin
G. Gonzales, S. Mata, M. Odehnal, M. Escandon
Two charts were prepared using the seismic-sequence interpretation of 300 km of lines, 38 wells, and 11 outcrop sections. The lithostratigraphic columns are in geologic time (Ma), dated by planktonic foraminifera, calcareous nannoplankton, palynomorphs and ammonites.
In the Zuni and Tejas A, third order sequences are difficult to establish. Supercycles TB1 and TB2 have excellent paleontological control. Supercycle TB3 carries no age marker fossils, but the seismic sequences are clearly defined. All TB 21 third order cycles of the global chart are present.
A transgressive sea up to 75 Ma advances over Guayana Shield, depositing a retrograding continental facies (Temblador) to the South and very good marine source rocks to the north (Querecual).
In Tejas A time the sea retired to the North, creating an extensive hiatus in the South, and depositing in the North the prolific formations of the Carito-Furrial trend. The Tejas A-4 is almost absent. The Lower Oligocene transgression does not occur in this basin. From 30 to 12.5 Ma the sea transgresses to the south, depositing the diachronous Oficina Formation that has the largest oil accumulation in the world.
Towards the end of the Middle Miocene, the maximum transpression occurs between plates, uplifting the Northern Range. After peneplanation, a sea level rise at 3.4 Ma covers the area and progrades toward the East up to the present.
Most of the production comes from Tertiary transgressive sandstones, sourced from Cretaceous mature marine shales.
AAPG Search and Discovery Article #90951©1996 AAPG International Conference and Exhibition, Caracas, Venezuela