Abstract

We have estimated the Curie point depth (CPD) in the northwestern corner of South America and the southwestern Caribbean Sea from spectral analysis of magnetic anomalies extracted from the World Digital Magnetic Anomaly Map. To do this, we performed three different spectral methods and chose the model that best fits the geologic and geophysical characteristics of the study area. Then, we calculated the geothermal gradient from these CPD values to assess the likelihood of the hydrocarbon “Golden zone” being present in some of Colombia’s sedimentary basins. Similarly, we tried to establish empirical relationships between CPD, geothermal gradient, and heat flux.

Our results show that the CPD lies between 12.6 km (7.8 mi) and 74 km (45.9 mi). The shallowest depths (<25 km [<15.5 mi]) are in the offshore Venezuela and Colombia basins of the Caribbean Sea, the onshore eastern Llanos and Caguan–Putumayo Basins, and southwestern Venezuela. The greatest depths (>50 km [>31 mi]) occur in parts of the western and central Cordilleras, Santander massif, and middle Magdalena, Catatumbo, Barinas-Apure, and Vaupes-Amazonas Basins. Based on the results, we found a relationship between an unexpected zone of deep CPD values (40–47 km [24.8–29.2 mi]) in the Colombia Basin and the presumable presence of an abnormal thick Caribbean Plateau with a continental inheritance. On the other hand, the contrasting deep and shallow CPD values in the Caribbean support the interpretation of flat subduction of the Caribbean plate beneath South America with a flexural topographic bulge toward the Sinu−San Jacinto and lower Magdalena Basins. Partial erosion of this bulge could have resulted in shallowing of the CPD with a consequent increase in geothermal gradient and heat flux. Also, we found a CPD shallowing beneath Caguan–Putumayo and eastern Llanos Basins.

Finally, based on the calculated geothermal gradient values in Colombia, we consider that the Golden zone of hydrocarbon occurrence most likely exists in the Choco–Uraba, eastern Cordillera, Guajira−Los Cayos, eastern Llanos, and lower Magdalena Basins, while the Golden zone would be absent only in the Vaupes–Amazonas Basin.