Location of the Suture Zone Separating the Great Arc of the Caribbean from Continental Crust of Northwestern South America Inferred from Regional Gravity and Magnetic Data

Abstract

Abstract The strongly curved zone of Cretaceous island arc rocks underlying the Greater Antilles, Aves ridge, and Leeward antilles of the Caribbean region constitutes the remnants of the elongate, east-facing Great Arc of the Caribbean (GAC) that formed in the early Cretaceous along the eastern margin of the Pacific and entered and consumed the proto-Caribbean Sea. The exact location of the suture between arc rocks of the docked GAC and the South American continental margin has remained poorly known in northwestern South America, especially in the area where the suture was subjected to post-collisional, right-lateral strike-slip displacements up to 100 km (62 mi) in magnitude. An improved location of the suture is significant for oil exploration because basins overlying South American continental rocks have higher-quality source and reservoir rocks and much larger oil reserves than basins overlying the GAC. To define the GAC suture location in known or active areas of petroleum exploration in the Falcon Basin, Gulf of Venezuela, La Vela Basin, and Leeward Antilles, we use modeling, filters, and enhancements on two regional gravity and magnetic databases. Regional maps of observed gravity, Bouguer and magnetic anomalies, and filtered and enhanced gravity data show that the elongate GAC has a distinctive character that can be mapped as a continuous feature in the areas of the Leeward Antilles and Paraguana-eastern Falcon areas of western Venezuela. Map view restorations of the right-lateral Oca–Ancon fault zone by realigning offset magnetic highs and lows show an approximate right-lateral displacement within the GAC suture zone area between 80 km and 100 km (50 mi and 62 mi) that is consistent with published estimates for the Oca–Ancon fault zone based on outcrop mapping. Finally, four regional gravity profiles, incorporating other forms of previous data including refraction results and wells to basement, were modeled across the GAC–South American suture zone area. A more precise location of the GAC–South American suture zone is proposed in western Venezuela that is defined by an elongate zone of distinctive magnetic highs.