A Multi-Method Approach to Reconstruct the Temperature History of a Triassic Sedimentary Sequence From Edgeøya, Norway

Abstract

Temperature plays a crucial role in the spatial and temporal distribution of diagenetic alterations and maturity of source rocks in sedimentary basins. Therefore, constraining the thermal history of sediments in a sedimentary basin is fundamental in forecasting porosity, permeability, and maturity of source rocks, which represent common uncertainties in petroleum exploration. Previous burial estimates of the Triassic rocks on Svalbard are solely based on organic matter maturation data from organic rich shales. These may have been affected by late Mesozoic magmatism, and there is therefore uncertainty in estimated burial depths and later uplift. The aim of this project was to provide more certain temperature estimates by utilizing a broader data set including both coal bearing strata and mineral diagenesis from sandstones. In the study, Mesozoic source and reservoir rocks from Sassendalen and Kapp Toscana Groups (Edgeøya, Svalbard) were analyzed using thermal maturity indicators from Rock-Eval pyrolysis combined with fluid inclusion microthermometry in diagenetic quartz. Other sedimentary inorganic diagenesis signatures further supported this. Rock-Eval pyrolysis data indicates that the De Geerdalen Formation experienced burial temperatures of ≥ 92 °C while the Tschermakfjellet and Botneheia formations experienced temperatures about > 124 to 138 °C. Fluid inclusions in authigenic quartz give similar diagenetic temperatures, from 70 to 124 °C, indicating that De Geerdalen Formation sandstones have been subjected to a maximum burial temperature of around 124 °C. This is further supported by the presence of a mixture of authigenic kaolinite and dickite implying that the sediments have been subjected to temperatures > 90 °C. This is consistent with the absence of illlite formation associated with kaolinite since the temperature did not exceed 130 °C. Finally, this work demonstrates that fully integrating diagenetic signatures with organic matter maturity indices aid to assess the quality of temperature proxies and to constrain accurately the thermal history of any basin.

AAPG Datapages/Search and Discovery Article #90332 © 2018 AAPG International Conference and Exhibition, Cape Town, South Africa, November 4-11, 2018