Abstract The regional character of organic matter types and depositional conditions of Pendleian, Brigantian and Arnsbergian mudstones between the Craven Basin and the Widmerpool Gulf was compared through interpretation of biomarker and pyrolysis data from 201 samples recovered from nine boreholes. The Carboniferous seaways have been determined to commonly host dysoxic conditions, enabling the preservation of a mixture of marine and terrestrial organic matter types. Photic zone anoxia, established by the presence of aryl isoprenoids, was determined to be persistent during ‘marine’ conditions represented by marine band, high-sea-level and carbonate facies. The observation and correlation of diasteranes and trisnorneohopane/trisnorhopane ratios within the samples and to other maturity parameters highlighted a significant clay mineral catalytic and/or hydrocarbon retention effect in the samples. This influenced both biomarkers and programmed pyrolysis thermal maturity indices such as T max , reducing the reliability of such results for interpreting the burial depth, and ultimately reserve potential.

Abstract Petroleum systems within rifted margin basins affected by volcanism continue to remain challenging for the exploration of hydrocarbons, most notably owing to the volume of intrusions that pose imaging, drilling and exploration problems. Typically, intrusions possess small thermal aureoles, but despite this, there is evidence that intrusions could none the less be responsible for the generation of commercial volumes of hydrocarbons. Here we shed new light on this petroleum systems challenge by integrating organic geochemical and Raman spectroscopic techniques to produce potential volumetric data for hydrocarbons generated as a result of igneous intrusion. The results indicate that, in areas with immature source rock intervals, it may be possible for intrusions to generate volumes of oil that would be capable of comfortably filling likely known oil reservoirs. This is a critical step forward in integrating several analytical techniques, indicating that under the right conditions there is the potential for hydrocarbon generation as a result of igneous intrusion.