Abstract We evaluated the unconventional hydrocarbon potential of the Holywell Shale Formation, a lateral equivalent of the Bowland Shale Formation deposited in the Blacon Basin. Two cores with Arnsbergian–Chokierian and Kinderscoutian (Namurian, Late Mississippian–Early Pennsylvanian) ages from the Ellesmere Port 1 borehole were sampled for palynological, stable isotope, Rock-Eval 6 pyrolysis and ichnofacies analyses. The study was designed to provide boundary conditions for parameters that are under-represented in the public domain and hamper accurate resource assessments: thermal maturity (through mean random vitrinite reflectance, R r), present-day organic matter content, kerogen type, original hydrogen index and original organic matter content. Our results show that the Arnsbergian Core 2 has been buried to a depth equivalent to the bottom of the oil window to the top of the gas window (% R r = 1.15%–1.29%). The Kinderscoutian Core 1 is too immature to have generated any natural gas (% R r = 0.91–1.03%). Furthermore, kerogen typing and ichnofacies analysis show that the Bowland Shale Formation is very heterogeneous, with organic matter originating from terrestrial and marine sources. Five palynofacies assemblages are described that range in basin setting from proximal and oxic to distal and anoxic with evidence of episodic connections to the open ocean. The combination of heterogeneity and low thermal maturity restricts the thickness of the Bowland Shale Formation in the Blacon Basin that is prospective for unconventional hydrocarbons. Our results show that these Carboniferous mudstones should not be treated as uniform units with uniform composition and maturity in basin modelling and resource estimates. This undoubtedly has repercussions for future exploration because the contrasting composition and density of the materials making up the Bowland Shale Formation may complicate extraction, while the thermal maturity window significantly narrows the prospective interval.

Abstract In the Junggar Basin, northwestern China, the biostratigraphy and vegetation patterns of the Middle–Late Triassic sediments are comparatively poorly resolved. Here we investigate Middle–Late Triassic successions of the Dalongkou Section in the southern Junggar Basin for palynostratigraphy and vegetation patterns. Three palynological abundance zones are proposed here: the Aratrisporites Abundance Zone (Middle Triassic), the Dictyophyllidites – Aratrisporites Abundance Zone (latest Middle to early Late Triassic) and the Lycopodiacidites – Stereisporites informal abundance zone (Late Triassic). A review of previous records of the Fukangichthys Fauna indicates that this vertebrate fossil assemblage is stratigraphically located within the uppermost part of the Karamay Formation and is Middle Triassic in age. The revised dating of this and other faunas are further used to constrain the palynological zones in the Junggar Basin. Although the palynoflora is consistently dominated by non-striate bisaccate pollen (produced by seed ferns and/or conifers) in the studied section, spores record a distinctive abundance increase during the late Middle Triassic. Spore taxon abundance changes indicate a vegetational shift from a Middle Triassic–early Late Triassic community characterized by abundant lycophytes (likely Annalepis and Pleuromeia) to a Late Triassic ecosystem with abundant dipteridaceous ferns (e.g. Dictyophyllum) in the Junggar Basin and across North China. This study updates the Triassic biostratigraphy in the Junggar Basin, and sheds light on temporal floral changes in this basin and elsewhere in North China during the Middle to Late Triassic.

Abstract Large magnitude and rapid negative carbon isotope (δ 13 C) excursions in the Triassic–Jurassic boundary (TJB) interval have been proposed as critical evidence for the hypothesis that the emplacement of the Central Atlantic Magmatic Province (CAMP) triggered global carbon cycle perturbations and the end-Triassic mass extinction (ETE). However, the pattern and timing of δ 13 C variations during the ETE remain poorly constrained. Here I present high-resolution organic carbon isotope (δ 13 C org) records from a terrestrial TJB succession continuously exposed along the Haojiagou valley on the southern margin of the Junggar Basin, northwestern China. The δ 13 C chemostratigraphic correlations, combined with the palynological data, indicate that the position of the TJB should be placed at the base of bed 53. Importantly, the results show that two rapid negative carbon isotope excursions at the end Triassic roughly coincide with two episodes of variations in the palynological records. This observation supports the hypothesis that two pulses of biotic crisis during the ETE may have been triggered by two major episodes of CAMP magmatic activity. In addition, the data in this study support an early start for CAMP magmatic activity in the early Rhaetian, which may have led to a global carbon cycle perturbation and the related biotic crisis or turnover.

Abstract An updated, integrated biozonation scheme for the Jurassic (Hettangian)–lowermost Cretaceous (Upper Berriasian) of the North Sea Basin incorporates 49 palynology biozones plus subzones (based on dinocysts, spores and pollen) and 27 microfaunal zones plus subzones (based on foraminifera, radiolaria and ostracods) to provide the essential chronostratigraphic calibration of the defined sequences. The biozonation scheme is tied to standard ammonite zonal chronostratigraphy wherever possible. Parts of the biozonation scheme are also applicable to onshore UK (boreholes and outcrops), onshore Denmark (boreholes) and offshore Netherlands.