Late Namurian Research Articles

Geochemical study of Mississippian to Pennsylvanian Namurian Shale in the Namur Synclinorium and Campine Basin (Belgium and S-Netherlands): Implication for paleo-redox reconstruction and organic matter characteristics

The Variscan foreland basin in Belgium and the Netherlands (Namur Synclinorium and Campine Basin) possesses potential targets for shale gas exploration based on the presence of Mississippian to Pennsylvanian Namurian black shales. Organic carbon and nitrogen contents and isotope data, major and trace element analysis, petrographic analysis, Rock-Eval pyrolysis, and basin modeling were carried out on a large sample set from 5 wells in the above-mentioned study area. Carbonate-dominated, silica-dominated, and quartz-rich mudstones with dominant type II kerogen were deposited within distal positions close to the basin floor while clay-rich, carbonate-rich, and silt-rich mudstones with mixed type II and III kerogens reflect depositional conditions at more proximal positions close to the basin margin. Sedimentary rocks were deposited in redox-stratified marine environments. Oxygen depleted environments occurred during the early Namurian A age, especially at distal depositional positions in contrast to elevated oxygenated environments during the late Namurian A age, especially at more proximal positions. From distal positions to proximal positions, redox conditions changed from mainly euxinic to anoxic conditions with some dysoxic episodes to mainly anoxic to dysoxic conditions with a few oxic episodes. The variation in δ15Nbulk values in the Namur Synclinorium suggests that N2-fixation dominated in anoxic environments during the early Namurian A age while nitrification, denitrification, and anammox in the water column dominated in anoxic to dysoxic environments with oxic episodes during the late Namurian A age. In the Campine Basin, denitrification and anammox dominated in anoxic to dysoxic environments during the early Namurian A age while N2-fixation dominated in anoxic environments at distal positions and nitrification dominated in dysoxic to oxic environments at proximal positions during the late Namurian A age. Namurian A mudstones are overmature with higher maturity in the Campine Basin than in the Namur Synclinorium. They display low potential for petroleum and gas generation based on Rock-Eval results. Basin modeling results indicate that the thermal maturity of Namurian A mudstones already reached its main phase of dry gas generation with overmature conditions during the Pennsylvanian in the Namur Synclinorium and the southern Campine Basin. In the northern Campine Basin corresponding to a depositional setting further away from the Variscan mountains, however, these sedimentary rocks became overmature during the Jurassic. Conversion of all type II kerogen to petroleum and dry gas occurred during increasing burial depth and thermal maturity. This left only overmature, hydrogen-poor kerogen remaining in the mudstones. The western Namur Synclinorium is regarded as the most prospective exploration area with high gas generation and storage potential as well as good hydraulic fracturing potential in terms of very high total organic matter content, large shale thickness, and high amount of brittle mineral contents. The Campine Basin is a secondary target with more limited gas generation and storage capacity, based on the moderate to high total organic matter content, the limited thickness of the mudstone interval, and limited brittle mineral contents.

A 25 million year macrofloral record (Carboniferous–Permian) in the Czech part of the Intra-Sudetic Basin; biostratigraphy, plant diversity and vegetation patterns

The Intra-Sudetic Basin is essentially a post-orogenic (Variscan) continental basin with a depositional history that ranges from the late Viséan to the Triassic. The fossil record in the Czech part of the basin, although discontinuous, spans the interval from the late Viséan to the Asselian. Middle Baskhirian (late Namurian) to Asselian adpression floras collected from boreholes, coal mines and outcrops permit reconstruction of the stratigraphic ranges of individual species in considerable detail, and reveal changes in plant diversity and vegetation patterns throughout this ~25Myr interval at high resolution, even to the scale of individual coal-bearing cycles. Species diversity recorded in the rock record throughout the studied interval mainly was controlled by climatically-driven potential for preservation of plant material, which was highest in poorly drained/waterlogged habitats (wetlands, lakes) concentrated in basinal lowlands and representing major windows of preservation. Low fossilization potential is typical for well-drained fluvial habitats, now represented by red beds deposited under drier (seasonal) climate. Diversity in major windows of preservation was highest during the late Langsettian and Duckmantian (>50 species), lower in the Late Pennsylvanian (25–40 species) and the lowest in the Asselian (~20 species). The diversity in red bed intervals with poor preservation potential varies between 11 and 21 species. The two distinct habitat types, with high and low preservation potential, were dominated by different plant groups. Wetland habitats flourishing during the (per)humid to slightly seasonal intervals were colonized mainly by cryptogamic plants and some early gymnosperms, mainly pteridosperms and cordaitaleans. Habitats represented by red beds were dominated by cordaitaleans; from late Asturian time walchian conifers also occurred in these plant assemblages. However, conifers only became common in red beds in the Cantabrian. In the Saberian, conifers are rarely found in discrete beds associated with coal-bearing strata, however, their common occurrences start in lacustrine rocks of Asselian age. Temporal changes in vegetation patterns that show an increasing proportion of gymnosperms, in both wetland and dryland habitats are in agreement with the well known aridification trend in late Paleozoic tropical Pangea. Delays between the first appearance of walchian conifers in red beds (late Asturian) versus coal-bearing deposits (Saberian) supports the hypothesis that evolutionary innovations took place outside the windows of preservation, i.e. in well-drained, moisture-deficient areas.

Palynostratigraphy of Mississippian and Pennsylvanian rocks, Joggins area, Nova Scotia and New Brunswick, Canada

Carboniferous rocks in the Joggins area, Nova Scotia, and the Maringouin Peninsula, New Brunswick, are world renowned for their well-preserved macroflora, but this paper is the first detailed study of the palynoflora. The section is comprised of the Mississippian Windsor and Mabou groups overlain disconformably by the Lower Pennsylvanian Cumberland Group. The Windsor Group rocks proved to be barren of palynomorphs but the Mabou Group yielded spores and pollen of Brigantian (late Viséan) to Arnsbergian age (early Namurian = early Serpukhovian). The assemblages are assigned successively to the Schopfipollenites acadiensis–Knoxisporites triradiatus, the Grandispora spinosa–Ibrahimispores magnificus, and the Reticulatisporites carnosus Zones. A major palynofloral change takes place between the Mississippian Mabou and the Pennsylvanian Cumberland assemblages. This is believed to reflect a significant regional hiatus in the Joggins section and elsewhere in eastern Canada. The Cumberland Group is characterized by an abundance of Lycospora spp. and monosaccate gymnosperm species of Yeadonian? (Late Namurian = middle Bashkirian?) to late Duckmantian (late Bashkirian?) age. The palynological succession is divided into the Raistrickia saetosa, the Raistrickia fulva, and the Vestispora magna zones. Age determinations of the zones, based on comparisons with Western Europe and the North Sea, are tentative because the Cumberland assemblages lack diversity and many taxa diagnostic in Western Europe are absent in the assemblages of the Joggins area, possibly due to environmental and climatic differences.

Understanding basin sedimentary provenance: evidence from allied phytogeographic and heavy mineral analysis of the Palaeocene of the NE Atlantic

The drilling of hydrocarbon exploration wells in the Faroe–Shetland Basin has provided an expanding sample resource that provides material for testing recently developed palynology-based sediment transport analysis. This technique has been verified by comparison with heavy mineral analysis; both approaches have been used to identify sediment sources and input points along the strike of the Palaeocene West Shetland Platform. Integration of heavy mineral and palynological data has provided a basis for understanding arenaceous and argillaceous sediment distribution and sourcing. In addition to a source from the western, Greenland side of the basin, four argillaceous and four arenaceous sedimentary sources have been identified along the strike of the West Shetland Platform. These vary in temporal and spatial distribution, and thus provide a history of sediment source evolution. This analysis supports a persistent difference in source between the Corona Basin and the Flett and Judd Sub-basins. Although source variation and overlap between basins is evident, transfer zones represent both conduits for and barriers to effective sediment transport. Both palynological and heavy mineral evidence identifies the former presence of Late Namurian–Westphalian strata on the West Shetland Platform, which were removed by subsequent erosion.

Long term monitoring of urban subsidence by Permanent Scatterer DInSAR

Abstract A new dragonfly of family Meganeuridae Shenzhousia qilianshanensis ge. et sp. nov., discovered from Ningxia Hui Autonomous Region in North China, is described in the present paper. It has an estimated wingspan of about 450–500 mm and may be the largest fossil insect in Late Carboniferous Namurian Stage discovered by far. The new species is referred to Meganeuridae because of the presence of the characteristic oblique vein between anterior branch of radius (RA) and posterior branch of radius (RP) near the base of RP2. It differs from other genera within the family in the following characteristics: Precostal area short and not extending to the midwing; posterior branch of subcostal vein short, merging into costal vein near the level of originating point of IR2; RP forking earlier than anterior branch of media basally; RP1+2 and RP3+4 parallel and close to each other for a long distance, and then diverge gradually surpass midwing. * Supported by National Natural Science Foundation of China (Grant No...

A Late Namurian (318Ma) $^{40}Ar/^{39}Ar$ Age for Kaersutite Megacrysts from the Black Ball Head Diatreme: An Age Limit for the Variscan Deformation in South-West Ireland

The Black Ball Head diatreme on the Beara Peninsula (Co. Cork, south-west Ireland) intrudes Lower Carboniferous marine siliciclastic sediments, and comprises an inner and an outer zone of pyroclastic infill. The outer zone is dominated by lithoclasts of local sediments and igneous rocks, whereas the inner zone is characterised by an assemblage of kaersutite, phlogopite and Ti-magnetite megacrysts and ultramafic pyroxenite nodules. $^{40}Ar/^{39}Ar$ step-heating dating of two kaersutite megacrysts from the inner zone yielded a c. 318 ± 3Ma plateau age (2σ). This late Namurian age is interpreted to be the age of diatreme emplacement. The pyroclastic infill is foliated and the c. 318Ma age therefore provides an older age limit for the Variscan deformation in this part of the Rhenohercynian fold belt.

A Late Namurian (318Ma) 40Ar/39Ar Age For Kaersutite Megacrysts from the Black Ball Head Diatreme: an Age Limit for the Variscan Deformation in South-West Ireland

The Black Ball Head diatreme on the Beara Peninsula (Co. Cork, south-west Ireland) intrudes Lower Carboniferous marine siliciclastic sediments, and comprises an inner and an outer zone of pyroclastic infill. The outer zone is dominated by lithoclasts of local sediments and igneous rocks, whereas the inner zone is characterised by an assemblage of kaersutite, phlogopite and Ti-magnetite megacrysts and ultramafic pyroxenite nodules. 40Ar/39Ar step-heating dating of two kaersutite megacrysts from the inner zone yielded a c. 318 ‘ 3Ma plateau age (2ao). This late Namurian age is interpreted to be the age of diatreme emplacement. The pyroclastic infill is foliated and the c. 318Ma age therefore provides an older age limit for the Variscan deformation in this part of the Rhenohercynian fold belt.

Late Yeadonian (Upper Sandstone Group) incised valley supply and depositional systems in the South Wales peripheral foreland basin: implications for the evolution of the Culm Basin and for the Silesian hydrocarbon plays of onshore and offshore UK

Abstract The Upper Sandstone Group of South Wales has previously been interpreted as a simple NNW–SSE trending incised valley that was filled during the late Yeadonian (Namurian G1b). Data presented in this study indicate a far more complex scenario. The group is well developed in the Pembrokeshire sub-basin but it is absent from the main part of the South Wales Basin located to the east of the Penlan Axis. The principal source area for sediment flux was the forebulge of the basin located to the north in Lower Palaeozoic (foreland) strata. Variscan flexural uplift of this source area and an accompanying rapid, high magnitude fall in sea level produced a very high sediment budget. Thus, during the late Yeadonian lowstand of sea level, massive amounts of sediment were being generated and transported via an incised valley system across the western part of the South Wales peripheral foreland basin. The location and orientation of the incised supply system and its related interfluves were controlled by intrabasinal, synsedimentary Variscan structures, many of which were reactivated Caledonian extensional faults. During the succeeding sea-level rise the incised valley was filled, initially by fluvio-deltaic sands and later by estuarine argillaceous sediments. The implications of this combined tectonic–sedimentological–high resolution sequence stratigraphic model for the evolution of the late Namurian (Crackington Formation) turbidites of the Culm Basin are discussed. Examples of Silesian incised valley fill sandstone reservoirs developed in the East Midlands Oilfield and the Southern Gas Basin are briefly summarised and their spatial and temporal distributions are appraised. Data, generated from these case studies, are assessed in terms of their use for the modelling of incised valley fill sequences in foreland basins and other tectonic settings.

Late Yeadonian (Upper Sandstone Group) incised valley supply and depositional systems in the South Wales peripheral foreland basin: implications for the evolution of the Culm Basin and for the Silesian hydrocarbon plays of onshore and offshore UK

The Upper Sandstone Group of South Wales has previously been interpreted as a simple NNW–SSE trending incised valley that was filled during the late Yeadonian (Namurian G1b). Data presented in this study indicate a far more complex scenario. The group is well developed in the Pembrokeshire sub-basin but it is absent from the main part of the South Wales Basin located to the east of the Penlan Axis. The principal source area for sediment flux was the forebulge of the basin located to the north in Lower Palaeozoic (foreland) strata. Variscan flexural uplift of this source area and an accompanying rapid, high magnitude fall in sea level produced a very high sediment budget. Thus, during the late Yeadonian lowstand of sea level, massive amounts of sediment were being generated and transported via an incised valley system across the western part of the South Wales peripheral foreland basin. The location and orientation of the incised supply system and its related interfluves were controlled by intrabasinal, synsedimentary Variscan structures, many of which were reactivated Caledonian extensional faults. During the succeeding sea-level rise the incised valley was filled, initially by fluvio-deltaic sands and later by estuarine argillaceous sediments. The implications of this combined tectonic–sedimentological–high resolution sequence stratigraphic model for the evolution of the late Namurian (Crackington Formation) turbidites of the Culm Basin are discussed. Examples of Silesian incised valley fill sandstone reservoirs developed in the East Midlands Oilfield and the Southern Gas Basin are briefly summarised and their spatial and temporal distributions are appraised. Data, generated from these case studies, are assessed in terms of their use for the modelling of incised valley fill sequences in foreland basins and other tectonic settings.

The rotations of the Variscides during the Carboniferous collision: paleomagnetic constraints from the Vosges and the Massif Central (France)

This study aims at completing and refining results from previous paleomagnetic investigations carried out in various outcrops of the European Variscan belt. Sampling was performed in Visean effusive and intrusive rocks of the southern Vosges basin and the northern Massif Central, all emplaced in the time range 345–340Ma. Stepwise thermal demagnetization of 254 specimens from 13 sites of the Doller Valley and nine sites of the Massif Central has yielded a very similar paleomagnetic record for both areas. With the exception of post-Carboniferous overprints isolated in the southern Vosges, two groups of directions, with both normal and reversed polarity have been evidenced. The first group of directions, labelled C, occurs in both areas and is characterized by scarce pre-tectonic magnetizations (two sites) and by syn-tectonic overprints (five sites) acquired during the Late Visean convergence, i.e. in the time-range 340–328Ma. The mean pole Co is 28°S/45°E (k=139, α95=5°). The main group, labelled B, shows a negative fold test and a positive reversal test, indicating that the magnetizations are post-tectonic overprints, acquired after the main tightening phase, i.e. after 328Ma. At a few sites in both areas were evidenced syn-tectonic B magnetizations that are in favour of an overprinting in the context of post-Visean extension tectonics. The mean post-tectonic B direction of the Doller Valley (southern Vosges) 62°/−25° (k=52, α95=6°, N=11; VGP: 8°N/127°E) is consistent with the mean post-tectonic B direction 72°/−23° (k=126, α95=5°, N=6; VGP: 3°N/114°E) obtained from the tuffs, the grey microgranite and the dyke intrusive into the microgranite of the Massif Central. The occurrence of similar paleomagnetic records in the eastern and central Variscides implies that, from the Massif Central to the Sudetes, the belt has probably moved as one block, since Early Carboniferous.The change in inclination of the C components suggests a southward drift of the Moldanubian and Saxothuringien Variscides in the Late Visean (340–328Ma). According to geological features, in the same time, the Rhenohercynian crust was underplating the Saxothuringian arc and fore-arc zone. Subsequent to 328Ma, the drift turned into a rapid clockwise rotation by about 70° around a pole located on southeastern corner of Baltica, leading to the closure of the Rhenohercynian oceanic basin. In the Namurian, large-scale overprinting (B components), likely related to post-rotation extension, affected the internal belt. The convergence continuing, the Variscides underwent a second clockwise rotation by about 45° in the Late Namurian–Westphalian (320–305Ma). Stacking of the Rhenohercynian sedimentary cover and thrusting over the London–Brabant basement may be related with this motion.

Paleomagnetic evolution of the Armorican Massif in Late Paleozoic times, in the light of overprints recorded in Cadomian and Paleozoic units

Previous investigations have shown that in Paleozoic outcrops of the Variscides, the major part of the paleomagnetic record consists of overprints. After identification and dating of these overprints, the magnetic record can be used to constrain the geotectonic evolution of the investigated area after the major tectonic event. In order to test this hypothesis, a paleomagnetic investigation was carried out on various volcanic and plutonic units from Northern Brittany (48.5°N/3°W), emplaced and metamorphosed in the Late Proterozoic, during the Cadomian orogeny. To calibrate the overprints in terms of their ages, doleritic dykes intruded into the Cadomian basement in the Early Paleozoic, as well as Early Carboniferous intrusive and extrusive rocks were also sampled. Thermal demagnetization often shows multivectorial behaviour of most NRMs and indicates a wide range of magnetic components, characterized by various unblocking temperatures. A large majority of the components isolated in Cadomian units display directions that are consistent whith the results from the younger, Paleozoic units. With exception of the 〈D〉 components (mean VGP: 7°S/152°E) which are interpreted as being Ordovician in age, all other mean directions/poles agree with results obtained from Visean volcanic, plutonic and metamorphic rocks of the central part of the Variscan belt. This means that no Cadomian magnetization has survived the tectonic, magmatic and metamorphic phases that have affected the Cadomian basement during the Paleozoic. The major part of the magnetic overprints were acquired during the Variscan orogeny, particularly in relation to Visean and Westphalian magmatism.The Early Carboniferous (340–328Ma) 〈Cn〉 (7°S/53°E), 〈Co〉 (29°S/60°E) and 〈Cp〉 (51°S/62°E) components, the Middle Carboniferous (328–310Ma) 〈B〉 components (11°N/124°E), the Late Carboniferous (310–300Ma) 〈A1〉 (30°N/151°E), the Late Permian 〈A〉 (51°N/154°E) and the Jurassic 〈J1〉 overprints (72°N/107°E) delineate an apparent polar wander path that can be interpreted in terms of geotectonic evolution. Since the Late Visean, this evolution was the same as for the Massif Central, the Vosges, the Black Forest and the Odenwald-Spessart. The variable inclinations of the 〈C〉 components suggest a northwestward tilting of the area north of Saint-Brieuc and a possible latitudinal drift of the whole massif in Late Visean times. The 〈C–B〉 and 〈B–A1〉 segments of the APWP reveal two successive clockwise rotations by 70–80° in the latest Visean and by 30° in the Late Namurian–Early Westphalian. The first rotation closed the Rhenohercynian basin. During the last rotation the Variscan belt was tied to northern Europe. The 〈A〉 and 〈J1〉 overprints give evidence of hydrothermal activity in Northern Brittany in the Late Permian and the Early Jurassic.

Modèle sédimentaire et évolution géodynamique du Nord-Est de la Méséta occidentale marocaine au cours du Carbonifère inférieur

The Early Carboniferous sediments of the North-East of the Moroccan western Meseta are very diversified. They contain numerous types of carbonates, deposited upon shallow shelves, as well as deeper gravity and hemipelagic deposits. The progressive Early Carboniferous transgression, starts from the Agouraï area at V2a and reaches Imouzzer of Kandar at V3bγ. The opening of the North-East of the western Meseta basin by strike-slip NE–SW faults, is V2a in age. This basin evolved in an extensive context during all of the Early Carboniferous. These sediments were stricken by a compressive deformation between the Late Namurian and Permian times.

Stratigraphic evolution of provenance characteristics in Westphalian sandstones of the Yorkshire Coalfield

SUMMARY A combined study of heavy minerals and palaeocurrents shows that three main fluvial systems transported sediment to the Pennine Basin during Namurian and Westphalian times. The first, which brought a garnet-rich monazitic heavy mineral suite from the north, peaked in the Namurian and diminished through the Langsettian. The second flowed from the west, bringing heavy mineral suites with low garnet, low monazite and variable amounts of chrome spinel. It started in the late Namurian, replaced the first system in the Langsettian, and dominated thereafter until it was itself replaced in the late Duckmantian by the third system. This brought a garnetiferous heavy mineral suite with both monazite and chrome spinel from the E or SE and continued to the top of the preserved sequence, in the late Bolsovian. The first sourceland lay to the north, perhaps between Laurentia and Baltica, and included high grade metasediments or charnockites and granites. The second sourceland lay to the west and included mature, pre-existing clastic sediments of Devonian and possibly Lower Palaeozoic age. Ultramafic rocks such as ophiolites, possibly associated with Lower Palaeozoic ocean closure, were periodically exposed there. The third sourceland lay to the south, probably within the uplifting Variscan orogenic belt. It included low to moderate grade metasediments, high-grade gneisses, granites and ultramafic rocks.

Paleomagnetism of the Distal Member of the New Glasgow Formation, Nova Scotia, Canada: New Constraints on Magnetic Polarity Stratigraphy near the Base of the Kiaman Superchron

The ca. 315–260‐Ma Kiaman Reversed (Permo‐Carboniferous) Magnetic Superchron is an important time marker that can be used for correlation of stratigraphic sequences from a local to a global scale. Earlier workers, from a paleomagnetic study of the Joggins stratigraphic section of the western Cumberland Basin of Nova Scotia, demonstrated that the base of the superchron lies above redbeds of the lowermost portion of the late Namurian–Westphalian A Boss Point Formation. Although a detailed sequence of reversals was observed below this point, no normal magnetic polarity zones were recognized above it. In our study, samples were collected from redbeds of the distal member of the Westphalian A New Glasgow formation of the eastern Cumberland Basin, which directly overlie the gray sandstones of the Boss Point Formation. Most sampling sites carry a normal polarity magnetization, probably acquired at about the time of deposition. Therefore, the base of the Kiaman Reversed Superchron lies within or above the New Glasgow formation. Either the top of the Boss Point Formation is diachronous between the two areas, or, more likely, the base of the superchron is significantly higher in the stratigraphic section than previously recognized, a conclusion that is important for both intrabasin and intercontinental stratigraphic correlations. It implies that the pattern of pre‐Kiaman magnetic reversals reported from below the Boss Point Formation in the Joggins section is significantly older than previously thought and, therefore, cannot be used for comparison with magnetic reversal patterns that closely underlie the base of the superchron at other localities in the Cumberland Basin or on other continents.

A Carbon Isotopic Stratigraphic Pattern of the Late Palaeozoic Coals in the North China Platform and Its Palaeoclimatic Implications

Abstract This paper gives the stable carbon isotopic data in coals from the Late Namurian to Kazanian stages in the Serteng Mt., Xishan and Huainan coalfields of the North China Platform. Its stratigraphic pattern shows that several isotopic shifts are apparent, and the large δ13C negative shifts (approximately 2.5 to 3.0 %%) occurred during the Stephanian, Artinskian and Kazanian are observed in three Permo‐Carboniferous coalfields. Those negative shifts are neither related to the coal rank and coal macerals, nor caused by the variety of peat‐forming plants. The general decrease in the δ13C values of the Stephanian, Artinskian and Kazanian coals is consistent with an overall decrease in the δ13C values of ambient atmospheric CO2 and/or a relative increase in atmospheric Pco2 during the coal‐forming periods. Therefore the authors postulate that the oxidation of peat, and the δ13C‐depleted CO2 flux into the atmosphere during the above stages may have contributed to coeval palaeoclimatic warming by way of the greenhouse effect.

Sediment supply as a control on the variability of sequences: an example from the late Namurian of northern England

Currently, variations in accommodation space are seen as the major control on facies stacking patterns and stratal geometries. This paper emphasizes the importance of the sediment supply variable through the use of a regional, stratal surface-based interpretation of the late Namurian stratigraphy of northern England. Late highstand palaeogeographies and stacking pattern variations highlight spatial and temporal variations in sediment supply, which promote the contemporaneous development of prograda-tional, aggradational and retrogradational stacking patterns. This questions the derivation of relative sea-level curves from specific stacking patterns and highlights the potential for miscorrelation in areas with major sediment supply variations.

Palynological zonations and paleoecology of Carboniferous sequence from Zhongwei of Ningxia, Northwest China

Six miospore assemblage zones are established for Carboniferous strata (Namurian-Stephanian) in the Xiaheyan Section of Zhongwei, Ningxia, Northwest China. They correspond to the Early Namurian (goniatite E Zone and H Zone), Late Namurian (goniatite R-G Zone), Westphalian A-B, Westphalian C-D and Stephanian of West Europe, respectively. The general aspect of Carboniferous palynofloral in Zhongwei is dominated by spore types with affinities of Filicopsida and Pteridospermospsida; Sphenopisd and Lycopsid spores occupy the subdominant position, while the gymnospermous pollen grains of Cordaitopsida and Confiferopsida make lesser contribution to the flora. Three miospore phases are recognized in ascending order as Lycospora-Crassispore phase, Laevigatosporites-Torispora phase and Florinites-Pityosporites phase. The palaeoecological considerations of each phase are also discussed.

High Resolution Sequence Stratigraphy of the Late Namurian, Onshore Northern England: Implications for Silesian Reservoir Development: ABSTRACT

High Resolution Sequence Stratigraphy of the Late Namurian, Onshore Northern England: Implications for Silesian Reservoir Development: ABSTRACT

High resolution sequence stratigraphy of the late Namurian in the Widmerpool Gulf (East Midlands, UK)

Analysis of facies stacking patterns and stratal surfaces within late Namurian deltas of the Widmerpool Gulf has revealed 10 high frequency (fourth-order) depositional sequences. Sequence correlation is based on the characteristic ‘marine band’ fauna of their condensed sections. In many instances, sequence boundaries are difficult to recognize unless there is clearly demonstrable lowstand incision. Consequently, it is often difficult to separate late highstand from falling stage progradation with any degree of confidence. Sequence thickness variations and the dominance of particular stratal surfaces and systems tracts were controlled by a longer period (third-order) cycle of relative sea-level rise and fall during the Marsdenian-Yeadonian. Major fluvio-deltaic sand bodies in the Widmerpool Gulf were formed by distributary channel progradation (e.g. Chatsworth Grit) during the late highstand and/or falling stage systems tracts, and by the filling of incised valleys (e.g. Ashover Grit and Rough Rock) following marked sea-level falls. Channel belt and valley fill orientation was initially influenced by differential compaction, but this influence decreased during the late Namurian. The recognition of incised valley fills within the late Namurian has implications for estimating the magnitudes and periodicities of Carboniferous relative sea-level change.

A revision of the biostratigraphy of the Late Namurian–Early Westphalian succession of Westward Ho!, North Devon

Newly discovered non-marine bivalve bands and other fossiliferous horizons, re-collection of some known horizons and re-examination of museum material from an inland section covered over for many years are utilized to correlate the succession at Westward Ho!. A non-marine bivalve band at Westward Ho! is correlated with one in the late Namurian of South Wales. The dated strata range from the late Namurian, very probably late R 1c in Cycle 3 of the Bideford Group, to the lower part of the Communis Chronozone in Cycle 9, which includes the Cornborough Sandstone and overlying ‘Culm Bed’. The adjacent Greencliff Beds, which have yielded a marine trace fossil, are briefly discussed and their structure is re-interpreted. They may possibly be of an earlier age than the Bideford Group. The Westward Ho! sequence, when compared with those of nearby Clovelly and Bude to the southwest, reveals stratigraphical gaps and lacks five black shale horizons with major goniatite bands. The possible significance of these differences in the Westward Ho! succession is briefly discussed.