Source rock analysis, thermal maturation and hydrocarbon generation in theSiluro-Devonian rocks of the Gaspe Belt basin, Canada.

The northeastern Gaspe Peninsula is divided into two distinct tectono-strat igraphic domains: Cambro-Ordovician rocks of the Humber and Dunnage zones, to the north, and Siluro-Devonian rocks of the Gaspe Belt, to the south. Th e northeastern part of the Gaspe Belt is being investigated for its hydroca rbon potential. This area is dissected by major NW-trending faults that div ide the study area into three tectonic domains: the northern, central and s outhern blocks. During the Late Silurian-Early Devonian Salinic disturbance , the faults were active as synsedimentary normal faults. Faults were react ivated as dextral strike-slip faults during the Middle Devonian Acadian Oro geny. Regional Acadian folds are ENE- to E-trending. Locally, NW-trending f olds related to the Salinic disturbance occur close to the faults. Because of their total organic carbon content (TOC), the Cambro-Ordovician rocks were considered to be more likely source rocks than rocks of the Silu ro-Devonian Gaspe Belt before maturation. Good source rock intervals are locally present in the York River Formation. in all the tectonic blocks of the study area. These beds are rich in organ ic matter, are marginally mature and of limited extent. Based on TOC and Ro ck-Eval analyses. the Indian Point and Forillon formations show significant thicknesses of fair source rocks in some wells of the central block where most oil indications and seeps occur. Our results indicate that these sourc e rocks have the highest hydrocarbon potential. A new calibration is proposed between the reflectance of collotelinite (sta ndard vitrinite) and that of chitinozoans and solid bitumen. which are more common than vitrinite in marine successions of the Gaspe Belt. Interpretat ion of reflectance analysis indicates that thermal maturation in the Gaspe Belt succession is primarily related to burial and occurred during depositi on of the Gaspe Sandstones. Maximum burial is contemporaneous with Acadian ENE- to E-trending folding and pre-dates strike-slip faulting. Oil and cond ensate in Indian Point and Forillon formations were mostly produced before the Acadian deformation, but after the Salinic disturbance. Potential sourc e rocks of the York River Formation generated some oil during and after Aca dian deformation.