Description of a Major Addition to the Central African Rift System (CARS) Located in the Central African Republic (CAR), Republic of Congo (ROC), and Democratic Republic of Congo (DRC).

Abstract

More than 35,000 line km of high resolution aerogravity/aeromagnetic data collected between 1992 and 2012 in the SW CAR, Northern ROC, and NW DRC, indicate a NW-SE trending Mesozoic rift basin. The basin extends > 380 km and is similar in orientation to the Muglad Basin. Located in one of the most remote and sparsely populated regions of Africa, the basin is undrilled, although several exploration licenses are in effect in portions of the basin in all three countries and some programs are underway. Known as the Carnot Graben in the early 20th century, the sediment cover over the adjoining Precambrian cratonic basement was believed to consist of no more than 750 meters of Cretaceous clastics. The recent surveys however clearly indicate a much thicker sedimentary section exceeding 7,000 meters and averaging about 3,500 to 5,000 meters. Multiple horst blocks are present within the basin. The outcropping sediments are largely Cenozoic and Cretaceous clastics with some Karoo sediments exposed on the western flank of the basin in the CAR. Upper Jurassic Stanleyville lacustrine shales outcrop a considerable distance to the east in the DRC and may be present. In 1993 we presented results of the first aero geophysical survey (funded in part by five major oil companies) at the EAEG Annual Mtg. and made the observation of a sharp angular bounding fault in the northern Republic of Congo suggestive of a rift basin, which we then called the ‘Carnot Basin’, because we suspected a connection to the outcropping Carnot Graben > 90 km distant. New surveys in 2012, at our suggestion, included trans-border flight grids. These new surveys confirm the continuity of this feature across three countries. The Carnot Basin may have been a significant paleogeographic feature in the Mesozoic through middle Cenozoic. Uplift of the basement in Cameroon /CAR south of the Benue Trough has led to the erosion of the northern limits of the basin's sediments. This results in several small sedimentary inliers in the CAR outcropping basement. At least one of these inliers appears to exhibit significant rainy season oil seepages, which we document. The role of the paleo Congo river drainage may also explain the extensive alluvial diamantiferous terrane near the town of Carnot, whose specific hard rock sources have eluded discovery to date. The presence of this proposed feature, if fully confirmed by future drilling, will require a major updating and rethinking of the Central African Rift System.

AAPG Datapages/Search and Discovery Article #90332 © 2018 AAPG International Conference and Exhibition, Cape Town, South Africa, November 4-11, 2018