While the broadness of the pyrolysis profile of most kerogens is described well by a parallel reaction model, the pyrolysis profile at a constant heating rate for certain well-preserved algal kerogens is narrower than can be described by a single first-order reaction. Further, these kerogens show an acceleratory period under isothermal conditions that is inconsistent with any parallel or nth-order reaction model. Three different models (serial, Bouster, and three-parameter) are tested against isothermal and nonisothermal pyrolysis data for a few samples, with the conclusion that the three-parameter model fits well and is the most stable and reliable. The three-parameter model reduces to a first-order model when the acceleration parameter is zero. The overall activation energy and frequency factor from this model are very close to those of the T max-shift method recommended earlier.

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The Rhaetic - Jurassic - Lower Cretaceous sediments from the Børglum 1 and Uglev 1 wells have been investigated by coal petrographical methods to evaluate their hydrocarbon source rock potential. The methods include vitrinite reflectance analyses of maturity, optical qualitative rating of the composition of the dispersed organic matter in the sediments, along with an estimation of the total organic carbon content of the sediments. The composition of the sedimentary organic matter is highly influenced by the palaeogeographic conditions. In the Børglum 1 well the organic material is dominated by land-derived (mainly gas-prone) plant matter; this is also the case for the marine sediments due to introduction of plant material from the adjacent Fennoscandian Border Zone. The sediments in Uglev 1 also have a high content of terrestrial plant material, although there is more marine dominated (oil-prone) organic matter in the deposits of the Bream Formation. The most promising conditions tor generation of liquid hydrocarbons have been found in the Bream Formation in Uglev 1, but the investigated sediments are generally thermally immature, with a restricted potential tor hydrocarbon generation. The rank gradient for Uglev 1 (0.20 % Ro/km), which is situated over a deep-seated salt diapir is more than three times that of Børglum 1 (0.06 % Ro/km), which is placed more marginally in the Danish Subbasin. This is attributed to differences in the geothermal gradients (Børglum 1:19°C/km, Uglev 1: 32 and 37°C/km, uncorrected)

This study of Upper Pliensbachian – Bajocian/Bathonian deposits in a borehole drilled on the island of Anholt, Denmark incorporates sedimentology, biostratigraphy (palynomorphs and foraminifera), palaeomagnetism and coal petrology. The studied succession records a gradual change from marine inner shelf storm-influenced clays to mainly terrestrial sands, clays, and lignite containing a flora of mainly freshwater algae and pollen. The regression was initiated at the Pliensbachian–Toarcian boundary and marine influence ceased during Bajocian–Bathonian times; the regression thus took place earlier at Anholt than in the centre of the Danish Basin. The sediments in the Anholt borehole are referred to the Fjerritslev and Haldager Sand Formations. Although the Lower–Middle Jurassic boundary is commonly placed at the boundary between the two formations, our data indicate that at Anholt the upper Fjerritslev Formation (member F-IV) is of Aalenian age. The Lower–Middle Jurassic boundary occurs close to the boundary between members F-III and F-IV of the Fjerritslev Formation. In contrast to other Lower–Middle Jurassic successions in the North Sea region, smectites of inferred volcanic origin are preserved in the Anholt section, suggesting limited burial and hence less intense diagenetic illitisation or chloritisation of smectites. A down-hole increase in diagenetic influence is reflected by the increase down-section both in the thermal stability of kaolinite and in the vitrinite reflectance. Kaolinite of inferred authigenic origin forms a white powder in the quartz-dominated sands of the Haldager Sand Formation; this kaolinite is thermally very unstable and is interpreted to be of late diagenetic, post-uplift origin. The vitrinite reflectance data indicate that the Jurassic formations have been exposed to thermal maturation corresponding to burial to a depth of 1000–1200 m below their present depth. Post-maturation uplift of the order of 1 km probably occurred partly during Late Cretaceous – Paleocene inversion in the Kattegat area and partly during Oligocene–Recent regional uplift, the latter being the most important of the two uplift phases. Palaeomagnetic data indicate that the main carrier of magnetic remanence is fine-grained magnetite. The stable remanence shows a pronounced inclination shallowing, which is attributed to post-depositional compaction.