Thermal history modeling of the Georges Bank, U.S.A.: thermal inversion of transmittance color index (TCI) and vitrinite reflectance (VR) data

Abstract

Using a one-dimensional basin analysis model for the COST G-2 well in the Georges Bank area, offshore East Coast, U.S.A., thermal inversion of measured Vitrinite Reflectance (VR) data and of the Transmittance Color Index (TCI) converted to an equivalent VR value yielded essentially identical paleoheat flux variations with time. The paleoheat flux showed two peaks at ∼175 Ma BP and at 125-75 Ma BP. The earlier event corresponds to continental breakup and the beginning of the rift phase. The latter event corresponds to continued drifting of the continents and formation of new oceanic basement. Beside answering some important tectonic questions, the observations corroborated the theoretical and empirical connections between TCI and VR found for the G-2 well and for other wells in different geological settings. This fact, together with the fact that TCI measurements on physically amorphous organic material can be made on rocks devoid of vitrinite or spores and pollen (carbonates, pre-Late Silurian rocks, and siliceous black shales), should promote the utility of TCI as an effective geothermal history indicator.