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 Newly discovered foliage of Rhaphidopteri s zhouii sp. nov. from the Lower Jurassic Sangonghe Formation at the Haojiagou section in the Junggar Basin of Xinjiang, northwestern China, is investigated based on morphological characters and cuticular structure. The new species has anisotomically divided leaves and linear ultimate segments with a single vein; amphistomatic cuticle, with epidermal cells that are similar both on the upper and lower surfaces but more regular on the upper surface; stomata that are distributed densely on the lower cuticle and sparsely and confined to two bands near the lateral margin on the upper cuticle; and anomocytic stomata that are longitudinally oriented with four to six subsidiary cells of irregular shape and size. This is the first report of the genus Rhaphidopteris from Xinjiang. The gross morphology and epidermal characters of the new species improves our understanding of the morpho-heterogenus Rhaphidopteri s.

Abstract Twenty taxa of fossil plants are described from the Sangonghe Formation (Lower Jurassic) of the Haojiagou section in the Junggar Basin, Xinjiang, NW China. The Sangonghe flora consists of Equisetales, ferns, bennettitaleans, ginkgoes, conifers and gnetales, but is dominated by ferns. It is a low-species-diversity but extraordinary flora as it has a high proportion (45%) of thermophilous or arid-tolerant (xerophilous) elements, in comparison to 0% in the underlying Badaowan Formation and c. 2% in the overlying Xishanyao Formation. These thermophilous or arid-tolerant (xerophilous) elements include Marattiopsis asiatica Kawasaki, Phlebopteris polypodioides Brongniart and Dictyophyllum sp. (ferns), Otozamites leckenbyi Harris, Otozamites sp., Zamites sp. and Dictyozamites sp. (bennettitaleans), Brachyphyllum (Hirmeriella ?) sp. (conifers) and Cadmisega ephedroides Krassilov and Bugdaeva (gnetales). Based on the geological ranges of the known species and comparisons with coeval floras in Eurasia, the age of the Sangonghe flora is Toarcian (Early Jurassic). The flora reveals a climatic warming and aridification event that occurred during the Toarcian in the Junggar Basin. Palaeontological (including palaeobotanical and palynological), sedimentological and geochemical data demonstrate that warming and aridification occurred widely across the north of China during the Toarcian, and that this might be the response of the terrestrial ecosystem to the Toarcian Oceanic Anoxic Event.