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This study characterizes the petrological changes occurring in an organic matter assemblage of Recent lacustrine sediments from Alberta, Canada, during the various steps of Rock-Eval 6® pyrolysis. The results indicate that the organic compounds released during pyrolysis at low temperatures of up to 300 °C (mainly S1-compounds) are most likely derived from a ‘stain-like’ amorphous organic matter, including pigments and oils/lipid products with strong, multicolored VIS fluorescence. The fluid characteristics of the thermally labile S1-compounds possibly account for the significant grain surface coating by the organic matter. Thermal alteration of sediments at 300 °C results in the transformation of some alginite and other macerals into a secondary product of blue–green fluorescing bitumen, which migrates into available free spaces. The release of S2-compounds during high temperature pyrolysis (from 300 to 650 °C) causes severe alterations in the morphology of the liptinitic organic matter. A bright yellow fluorescence that appeared at this stage is likely due to thermal transformation of bitumen produced in S1 pyrolysis and other liptinitic macerals into an “oily-material”, which fills cell lumens and becomes incorporated into the mineral matter. Neither the rapid rate of heating nor the sample residence time during Rock-Eval pyrolysis are sufficient for complete thermal destruction of the secondary hydrocarbon and bitumen products produced in the sample.

The hydrocarbon source rock potential of the Devonian Marcellus and Kettle Point black shales in southern Ontario has been assessed using Rock-Eval pyrolysis, gas chromatography, gas chromatography-mass spectrometry and incident-light microscopy. Both formations contain sufficient hydrogen-rich organic matter (Type II) to be considered possible source rocks. The kerogen is predominantly marine in origin. This organic matter was deposited in a clastic algal-dominated environment, and mainly consists of unstructured bituminite and unicellular alginite. The organic microfacies indicate shelf paleodepositional settings with a transition to an open basinal region. The optical (reflectance, fluorescence) and geochemical (Rock-Eval Tmax, extract yields, distributions of steranes and terpanes) maturity data indicate that the organic matter in the Kettle Point Formation is immature, whereas in the Marcellus Formation it has reached the early stages of hydrocarbon generation and expulsion. Some Devonian oils occurring in this area have characteristics similar to the Marcellus extracts, suggesting that more mature equivalent units from the Appalchian Basin could be their source.

Organic-rich shales are common in the Ringens Formation/Member, an Oxfordian-Kimmeridgian argillaceous unit which is widespread in the Sverdrup Basin of the Canadian Arctic Archipelago. The shales and siltstones of the Ringnes are laminated to burrowed and are interpreted to have been deposited under sub-oxic conditions in a mid to outer shelf setting. The organic matter (OM), which is up to 11 wt%, has relatively low H1 and OI values. Rock-Eval/TOC data, organic petrography and the environment of deposition of the Ringnes, are interpreted to infer that the organic matter in basin margin samples is mainly of terrestrial origin, with a variable but minor marine component. In the axial region of the basin, the OM appears to be of a mixed marine and terrestrial origin and has been partially oxidized. The high organic content is attributed to sedimentation rates high enough to bury the organic-rich sediments before complete destruction by aerobic bacteria and benthic scavengers. The organic content and HI values increase towards the axis of the basin. The thermal maturity of the Ringnes shales varies from immature on the basin margins to mature along the basin axis. In the eastern and central portions of the basin, however, the Ringnes shales are overmature at many localities due to the presence of diabase sills and dykes which were intruded in Early Cretaceous. By contrast, the maturity of the Ringnes is anomalously low over the crests of large salt-cored structures. Rock-Eval/TOC data and petrographic evidence indicate that the Ringnes shales have potential to generate significant amounts of thermogenic gas at low levels of thermal maturity.

Variations in reflectance and bireflectance of graptolites taken from the Cape Phillips Formation in the Queen Elizabeth Islands, Arctic Canada, are documented. Graptolites taken from core samples from Melville Island possess a wide range of reflectance (1.75–3.90% R0max). Graptolites taken from outcrop samples from the other islands have a much narrower reflectance distribution (0.57–0.81% R0max). The latter indicate that the organic matter is in the mature stage of hydrocarbon generation. Conodont colour-alteration indices in strata from Arctic Canada and in the Cape Phillips Formation in Eldridge Bay E-79, Melville Island, are low (1–1.5) and agree with the low reflectance of the Cape Phillips graptolites. The higher maximum reflectance values of the Melville Island graptolites indicate that the host sediments have experienced deeper burial and exposure to elevated temperatures compared to graptolites in the same formation of other islands. This study demonstrates that graptolite reflectance can delineate, relatively accurately, the thermal conditions that sediments enclosing them have experienced and, when combined with bitumen reflectance and stratigraphic and structural evidence, graptolite reflectance can be useful in assessment of thermal maturity and thickness of eroded section in lower Palaezoic successions.

Coals from western Canada were examined for structural changes occurring during oxidation, carbonization and hydrogenation by means of FT-IR spectroscopy, optical microscopy and chemical analysis. The coals are of Cretaceous to Eocene age, ranging in rank from subbituminous C to medium-volatile bituminous (0.42–1.47% R o ). Results indicate that the reactivity of the coals during the above mentioned processes depends on rank and petrological composition. Infrared spectroscopy is shown to be sensitive to the molecular structural changes occurring during these processes and provides a chemical basis for interpreting data from chemical analysis and optical microscopy.

Some of the oldest coals in the world are found within the Middle to Upper Devonian clastic wedge of the Canadian Arctic Archipelago. The coals investigated here occur in the Weatherall, Hecla Bay and Beverly Inlet formations on western Melville Island and range in age from Late Givetian to Middle Frasnian. Many of these coals are rich in liptinite macerals, particularly sporinite and hence can be termed canned coals. Both elemental and Rock-Eval analysis indicate these coals have the potential to generate liquid hydrocarbons. A good correlation between % liptinite with both H/C or Hydrogen Index is observed up to about 50% liptinite after which the latter two parameters level off. The coals range in maturity from 0.61 to 0.87% R o and hence should be in the oil window. The amounts of hydrocarbons that can be extracted from the coals when expressed in mg/g organic carbon are very low, suggesting that they are poor source rocks for oil. All the extracts except for the most mature and vitrinite-rich sample show high pr/ph ratios and biomodal n -alkane distributions. A cannel coal from The Beverley Inlet Formation has a very unusual triterpane distribution that includes regular, AB-ring desmethyl and AB-ring methyl hopanes. Steranes are in very low concentrations compared to hopanes in all samples. The relative abundance of C 28 and C 29 steranes appears to be influenced by maceral composition. Hydrous pyrolysis at 330°C for 72 h generated greater amounts of hydrocarbons from the coals suggesting they could be the source of liquid hydrocarbons at greater maturities. The hydrous pyrolysis experiments also indicate that thin-walled spores are more reactive than thick-walled spores at lower temperatures. The coals on Melville Island are not thought to be significant source rocks for the oil and gas occurrences in this area of the Canadian Arctic because they make up only a very small fraction of the total sedimentary package.

The source of the oil at Norman Wells has long been assumed to have been the Canol Formation and/or the Bluefish Member of the Hare Indian Formation. These two units are stratigraphically above and below the Kee Scarp Formation reservoir unit respectively, and are both bituminous shales. A wide range of analytical techniques including Rock-Eval pyrolysis, solvent extraction and fractionation, capillary gas chromatography, gas chromatography-mass spectrometry, and white light and fluorescence microscopy has been used to characterize core samples of these two units and two samples of crude oil from the Norman Wells field. Most of the analytical techniques were insufficiently refined to either differentiate the extracts from each other or to make a definitive oil/source rock correlation. Collision activated decomposition coupled with multiple ion detection mass spectrometry (GC-MS-MS) did provide sufficient chemical compositional detail of the oils and the two potential sources to demonstrate that the Canol Formation has been the effective source of the Norman Wells oil whereas the Bluefish Member has not. Petrological analysis of the organic fractions also indicates that although the bulk organic composition of both units may be classified as Type II organic matter, significant differences exist between them. The Bluefish Member contains substantial amounts of megaspores, whereas the organic matter in the Canol Formation is largely phytoplankton debris. The level of thermal maturity of the core samples ranges from immature to moderately mature in the vicinity of the Norman Wells field to overmature for the samples obtained to the west and north of the field. The level of thermal maturity of the oil was observed to be somewhat higher than that of the samples of the source formation directly above the field. It was thus inferred that some lateral migration from more mature areas has occurred but the extent of this migration was not necessarily more than a few to tens of kilometers.