Abstract: Sequence Stratigraphy of the Maturin Sub-Basin (Eastern Venezuela)

G. Gonzales, S. Mata, N. Santiago

The prolific Eastern Venezuela Basin has an area of about 160,000 km² and is bounded by the Pilar Fault to the North, the Guayana Shield to the South, the Baul Arch to the West and beyond the Orinoco Delta to the East.

Sequence analysis of three N-S and one W-E regional transects covered by over one thousand km of seismic lines and sedimentological, biostratigraphic and electrofacies studies of 80 wells allowed the definition of the sequence stratigraphic column of the basin.

Seven major unconformity bounded depositional sequences were defined from Barremian to Recent, three in the Cretaceous and four in the Tertiary. Twenty-one third-order cycles were recognized in the Tejas B supercycle (Upper Oligocene-Recent). This cycle correlates very well with the Gulf of Mexico and Global chronostratigraphic charts. In the proximal, southern area, each sequence shows transgressive sandstones in its lower section and regressive ones in the upper part, separated by claystones that include a maximun flooding surface. In the distal area, fine marine sediments predominate with local turbidites. Some electrical markers and planktonic fossils are traceable over long distances.

Regional transects show two distinct structural zones: tensional to the South and compressional to the North.

The best petroleum reservoirs occur in Tertiary and to a lesser extent in Cretaceous sequences. In this basin occurs the largest oil accumulation of the world (Orinoco), as well as several giant oil fields.

AAPG Search and Discovery Article #90951©1996 AAPG International Conference and Exhibition, Caracas, Venezuela