APPLYING RAMAN SPECTROSCOPY OF CARBONACEOUS MATERIAL (RSCM) TO STUDY VERY LOW-GRADE METAMORPHISM AND CONNECT EXPOSED NORTHERN RANGE ROCKS WITH SUBSURFACE ECONOMIC BASEMENT, TRINIDAD, WEST INDIES

The Northern Range exposes predominantly deeply exhumed metasedimentary rocks with Mesozoic depositional ages and Neogene metamorphic ages that strike E-W across the north of Trinidad. South of this range is the lowland Caroni Basin, the hilly Central Range, and prolific oil and gas production from the Southern Basin. The purpose of this study is to better understand the transition between the metamorphic rocks exposed in the Northern Range, subsurface basement rocks of the Northern Basin, and the Lower Cretaceous Cuche Formation exposed in the Central Range. The Lower Cretaceous Cuche Formation is of interest because it is recognized as the subsurface economic basement across Trinidad. The Upper Cretaceous Naparima Hill Formation is the known, mostly subsurface, petroleum source rock. We use Cuche Formation well cuttings and outcrop samples of the Cuche and Naparima Hill Formations to determine the maximum temperatures reached in our sample suite. After preparing and cutting thin sections, and creating a geological GIS, we will utilize Raman spectroscopy of carbonaceous material (RSCM) to determine peak rock temperatures. Through graphitization, the crystal structure of organic carbon changes as temperature increases. Graphitization is irreversible, so RSCM can thus be used to measure maximum rock temperatures. If a surface-subsurface thermal discontinuity is identified, this difference may allow us to determine whether it occurs along a thrust (high over low temperature), strike-slip (large temperature magnitude differences), or a normal fault (low over high temperature). Studying the basement rocks using RSCM across Trinidad should assist us in better understanding the paleo-tectonics of the southeast Caribbean, an area with a complex geologic history, and may enhance the potential for new petroleum discoveries.