SEISMIC AND GEOLOGIC EVIDENCES OF A COMPLEX STRUCTURAL INVERSION:”POP UP” STRUCTURES INTO THE EOCENE SEQUENCE ALONG STRIKE SLIP LAMA-ICOTEA FAULT. MARACAIBO BASIN, VENEZUELA

The structural evolution of Maracaibo Basin shows a series of complex tectonic events: extension-transtension between Early Eocene and Medium Eocene and Tectonic inversion during Late Eocene and Pliocene (Arminio et al., 1997).

As a part of this tectonic scenario it proposes the structural model of Eocene sequence (Misoa Formation) in the Atico region, located in the north-center area of Maracaibo Basin, called Block I. The sedimentary sequence is bounded by two erosive surfaces recognized in 3D seismic (Paleocene and Eocene unconformity).

Lama-Icotea fault represents the main structure in Block I, N15°-20°E and is a left-lateral strike slip fault. During the Cenozoic age this fault experienced a compressive-transpresive and distensive-transtensive evolution. The Atico is an elongated block oriented NE-SW, which is bounded at the West of the Lama-Icotea fault. The Atico reverse fault root into the main Lama-Icotea fault on the eastern flank. This block is divided for several Intra-Atico reverse faults oriented subparallel to the principal fault Lama-Icotea. This structure was interpreted using 3D seismic and images logs how a reverse fault system inside the Eocene sedimentary sequence (Misoa Formation).

The structural setting is chronologically associated with two evolutionary phases that occurred during Paleogene and Neogene, when the Maracaibo Basin it comprised by a high active tectonic margin: Extension-Transtension between Early Eocene and Middle Eocene in wich Lama-Icotea fault was reactivated how a normal fault with an oblique component, and tectonic inversion between Late Eocene and Pliocene where the oblique compressive forces (NW-SE) became in the strike slip system it has seem actually. The origin of the Atico Block is part of a delayed stage of blocks shortening by compression-transpresion, resulting an uplift of the block bounded by Lama-Icotea and Atico fault which have formed “pop up” features like Atico Block along of this structures.

The integration of 3D seismic interpretation with image logs, correlation wells and dip meters analysis have led improve the knowledge of the timing and evolution of the complex Atico block providing a comprehensive and detailed 3D structural model, in a region where PDVSA continues drilling to drain the hydrocarbon that has been trapped in the Atico block.