Crustal Provinces of the Nicaraguan Rise as a Control on Source Rock Distribution and Maturity

Ott, Bryan; Mann, Paul; Saunders, Mike

The offshore Nicaraguan Rise in the maritime zones of Honduras, Jamaica, Nicaragua and Colombia covers a combined area of 500,000 km2, and is one of the least explored carbonate regions of late Cretaceous-Cenozoic age remaining on Earth. The purpose of this study is to describe the Cretaceous to Recent tectonic history of the deep-water Nicaraguan Rise, and to better understand how different types of tectonically-juxtaposed crustal blocks are overlain by distinctive Eocene to Recent source rocks. We interpreted 8700 km of modern, deep-penetration 2-D seismic data tied to five wells that penetrated the top of late Cretaceous igneous basement. Combining these seismic data with gravity, magnetic and crustal refraction data, we define four, fault-bounded crustal provinces for the offshore Nicaraguan Rise: 1) a thicker (15-18 km) Late Cretaceous Caribbean ocean plateau (COP) with rough, top basement surface; 2) normal (6-8 km) Late Cretaceous COP with smooth top basement surface (B") and with correlative outcrops in southern Haiti and Jamaica; 3) Thinned, Precambrian-Paleozoic continental crust (22-24 km thick) with correlative outcrops in northern Central America; and 4) Cretaceous arc crust (>18 km thick) with correlative outcrops in Jamaica.

Three source rock families have been identified from oil or gas shows in ten, on- and offshore Jamaican wells: 1) Oxfordian, marine source rock equivalent to the Smackover formation of the northern Gulf of Mexico; 2) Maestrichtian, marine source rock; 3) Eocene aged mixed marine/terrestrial Chapelton formation of Jamaica (also known as the Guy's Hill formation). The Chapelton formation sampled in the Content -1 well contains an average total organic carbon (TOC) value of 3.97%, and is the highest quality source rock of all three sources. Tertiary sections of the Chapelton formation that were sampled had not reached depths greater than 2-3 km, making these rocks immature to marginally mature. However, deep rifts up to 9 seconds TWT exist in the immediate offshore areas of Jamaica, and form likely sweet spots for mature source rocks. Late Cretaceous and Eocene source rocks are similar in Jamaica and Honduras, and may form a sheet-like deposit across the Nicaraguan Rise. Light oil and gas shows of similar ages have been identified in the Main Cape -1 and Miskito -1 wells, and may be linked to widespread source rock deposition on the Nicaraguan Rise.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013