Abstract

The Colombian Caribbean Margin, offshore the Guajira Peninsula, results from the complex interaction of the Caribbean oceanic, South American, and Nazca tectonic plates through geologic time. The Chichibacoa–Rancherias Basin (CRB) is located at the boundary of the Caribbean and South American tectonic plates, and extends from the shelf northward into deepwater. The basement of the CRB is characterized by lateral terrane accretion within a major transpressional province, involving the Caribbean plate arc, accreted terranes of transitional crust, and continental crust.

The tectono-stratigraphic framework of the CRB is made up of 10 Paleogene and Neogene depositional sequences we define as SQ 1 to SQ 10 and an earlier Cretaceous (Maastrichtian to Campanian) sequence we define as SQ 0. Each of these sequences records an average time span of 5–10 My, representing major second- to third-order sequences. The definition and classification of the basin involved the application of high-resolution biostratigraphy from exploratory wells, U–Pb zircon isotopes (core), and a systematic calibration of seismic profiles using wells and biostratigraphic data. U–Pb zircon geochronology is used to constrain the age and nature of the basement in the CRB, which consists of Cretaceous meta-sedimentary rocks ranging in age from 67 My to 82 My (SQ 0).

Analysis and interpretation of the data reveals that the CRB displays different structural styles of deformation, distinctive basement types, and sedimentary basin fills. The CRB is bounded by normal faults with strike-slip component. Locally, the strike-slip faults are inverted during the deformation of the accretionary prism of the Southern Caribbean Deformed Belt (SCDB). According to the structural reconstructions, gravimetric and magnetics modeling and basement sample analysis, the CRB lays over continental crust. Along the northern edge of the CRB, the SCDB shows two styles of deformation. The landward segment is characterized by structural inversion of pre-Eocene and probably Oligocene depocenters. Gravity and magnetic data indicate that this zone has a Cretaceous meta-sedimentary basement, which differs from the CRB, which is underlain by continental crust basement. The seaward structural segment (younger) exhibits well-developed thrust faults and duplexes associated with the Miocene and Pliocene deformation.