AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Nicaraguan Rise Offshore Honduras: Upper Cretaceous Source Rock May Contribute to a Proven Eocene Hydrocarbon System at Main Cape-1 in the Mosquitia Basin
(1) Brazos Valley GeoServices, Inc, Cypress, TX.
(2) Jackson School of Geosciences, University of Texas at Austin, Austin, TX.
(3) Petroleum GeoServices, Inc, Houston, TX.
The submarine Nicaraguan Rise (NR) covers 500,000 km2 and is arguably the largest and most under-explored equatorial, mixed carbonate-terrigenous, Jurassic-Recent environment remaining on Earth. Continuing studies of legacy exploration data from the NR offshore and onshore Honduras are supplemented by 3 new long-offset multi-client 2D seismic profiles provided for this study and by geochemical data from a Main Cape-1 oil sample. Onshore we recognize two rifts sequences: 1) a M-U Jurassic coal-bearing sequence related to the rifting of N and S America, and 2) an U Jurassic-L Cretaceous sequence related to the rifting of the Chortis block from southern Mexico. Offshore the new profiles allow us to extend seismic observations into the deformed Mesozoic strata, which are poorly imaged in the legacy 2D data. The similarity of the onshore and offshore stratigraphy is made apparent by the Caribe-1 well which penetrated a 1,300 m thick Aptian-Albian platform carbonate section and bottomed in Neocomian conglomerate. Seismic correlation of the Mesozoic stratigraphic units is tied to this key well. The faulted Tela basin shelf of northern Honduras appears to be an early Tertiary extensional overprint that defines the northern limit of a mostly N-verging L Cretaceous thin-skinned thrust-fold belt exposed onshore in the Montanas de Colon near the border with Nicaragua and which is represented offshore by inverted extensional structures of the same age. The compressional structures formed by collision of an oceanic terrane (Siuna) with the Chortis block begining in Cenomanian time and lasting until the end of the Cretaceous. U Cretaceous clastic and carbonate strata were deposited in piggy-back basins that formed adjacent to prominent inversions of the Mezozoic rifts, and organic-rich source rocks equivalent to the Guare Limestone onshore may have been deposited in such basins offshore. The piggy-back basins are less deformed and are less deeply buried than the older Mesozoic strata and one such basin is observed to underlie marginally-mature source rocks of M-U Eocene age near the Main Cape well in the Mosquitia basin. Similar basins may also be preserved to the north in the Tela basin - Honduras Borderlands. An oil sample from the Main Cape well suggests a contribution from an U Cretaceous source that may have come from a Guare equivalent. Proximity to preserved U Cretaceous strata may be a key to future exploration success on the NR.