New Evidence for Spreading Ridge, Colombia Basin, Southern Caribbean

Abstract

Beginning in 2015, Anadarko Petroleum Corporation partnered with CGG to acquire a world-class 3D seismic dataset covering almost 30,000 km2 immediately outboard and north of the Southern Caribbean Fold Belt. The subsequent seismic volumes have since been processed into depth with a maximum record of 25,000 meters below sea level. The quality of the data is excellent, allowing the interpreter to clearly see unique basement morphologies never before interpreted in this region of the Caribbean plate. The data show two distinct basement fabric orientations, consisting of 1.) Parallel ridges and troughs 15-30 kms wide striking N70degW with morphologic amplitudes of approximately 1,500-2,000 meters from ridge peak to base trough, and 2.) Parallel ridges and troughs 20-30 kms wide striking N25degE with a similar ridge peak to trough amplitude as the former set. In addition to the unique fabrics identified in the two sets of ridge-trough trends, comparable trends in basal crustal reflectors are also evident. The first set (N70degW) is seen mostly in Anadarko’s COL-1 block, and has a prominent and parallel reflector approximately 2.5-3 kms below the top of the crustal reflector. The second set (N25degE) evident in Anadarko’s COL-6 and COL-7 blocks show dramatic thinning of this same interval with the interpretation of potential exposed lithosphere or serpentinized mantle. Realizing the constraints of the data, the authors propose the ridge and trough system of the N70degW lineaments to be the preserved fracture zone of a thin, disorganized oceanic crust emplaced during the separation of North and South America and the orthogonal system (N25degE) marks the final remnant of the associated, potentially magma-poor, spreading ridge.

AAPG Datapages/Search and Discovery Article #90330©2018 AAPG Hedberg: Geology of Middle America – the Gulf of Mexico, Yucatan, Caribbean, Grenada and Tobago Basins and Their Margins “Integration of the geology of the area from the southern onshore of North America to the northern onshore of South America”, Siguenza, Guadalajara, Spain, July 2-5, 2018