Late Mississippian Research Articles

Detrital thermochronology histories preserved in Paleogene strata of Utah (USA) provide distant records of Paleozoic Alleghanian orogenesis and sediment dispersal

We present new zircon U-Pb and (U-Th)/He data from sandstone cobbles of the Paleocene−Eocene Wasatch Formation of northern Utah (western United States). Provenance data demonstrate that these zircons have been recycled through at least two sedimentary cycles, deposited first as sand grains in the Pennsylvanian−Permian Weber Sandstone and second as sandstone cobbles in the Wasatch Formation. The thermal history of these grains requires rapid Late Mississippian−Pennsylvanian cooling, preserving a new, distant record of early Alleghanian orogenesis that is also a distinct provenance signature. Zircon thermochronology provides a powerful archive of ancient exhumation patterns and continental-scale sediment transport and deposition. Our study demonstrates that such thermal histories are resilient throughout multiple episodes of recycling.

The palaeobiogeographic significance of the Nötsch area (Austria) during the Middle and Late Mississippian based on rugose corals

The Carboniferous of Nötsch (South Austria) is composed of three formations: the Erlachgraben Formation, the Badstub Breccia, and the Nötsch Formation, that yielded abundant corals, several of them being new for that region. The assemblage is composed of 11 rugose coral species (Siphonophyllia sp., Pseudozaphrentoides juddi, Lublinophyllum? sp., Dibunophyllum bipartitum, Arachnolasma cylindrica, Palaeosmilia murchisoni, Aulokoninckophyllum carinatum, Siphonodendron martini, Diphyphyllum furcatum, Solenodendron furcatum, and Solenodendron horsfieldi), two tabulate species (Multithecopora sp. and Palaeacis sp.) and one heterocoral species (Hexaphyllia mirabilis). In addition, five rugosans that are not in our collection have been identified by previous authors (Clisiophyllum sp., Pseudozaphrentoides sp., Caninia sp., “Palaeosmilia isae”, and Lophophyllidium sp.). The rugose and tabulate species are described and figured. A palaeobiogeographic analysis comparing the Mississippian assemblages from Nötsch and other Austrian outcrops with other domains in Central Europe has been performed using hierarchical clustering with Simpson and Dice similarity indices. The statistical comparison of the rugose coral assemblages at the genus level allows a better perception of the distribution of the shallow water carbonate platforms in that part of the Western Palaeotethys during the Visean and Serpukhovian. The results are incorporated in a schematic palaeogeographical map of the studied area for the late Visean.

Burial and thermal history modeling of basins in convergent oblique-slip mobile zones: A case study of the Ardmore Basin, southern Oklahoma

The burial and thermal history of sedimentary basins within oblique-slip mobile zones are unique and multifaceted, with irregular periods of subsidence that are closely related to compressional and shear stress. Modern basin modeling techniques can constrain the timing of tectonic events and thermal history as well as determine rates and magnitudes of basin subsidence, which in turn, helps guide exploration for hydrocarbons. The work presented here is the first modern basin modeling effort in the Ardmore Basin in southern Oklahoma. The study uses 12 one-dimensional burial history models to evaluate the thermal maturity of the Late Devonian (Famennian)–Early Mississippian (Tournaisian) Woodford Shale and the Early–Late Mississippian (Tournaisian–Serpukhovian) Caney Shale hydrocarbon source rocks. All models display a similar tectonic evolution with subsidence during and following Cambrian Iapetan rifting, tectonic stability during a Silurian–Late Mississippian passive margin phase, Pennsylvanian synorogenic subsidence, Permian post-orogenic subsidence, Late Permian–Early Cretaceous regional uplift and unroofing, and Early Cretaceous–Paleogene subsidence of the Gulf of Mexico Basin. Episodic Pennsylvanian subsidence appears to have been synchronous with sequential uplift of the Wichita Uplift and the Arbuckle Uplift in response to major left-lateral transpression. Rapid and high magnitude Late Mississippian–Permian subsidence (>250 m/m.y.; 820 ft/m.y. in basin synclines) suggests the Ardmore Basin functioned episodically as an elevator basin, which is typical of sedimentary basins in oblique-slip mobile zones. The Devonian–Mississippian shale section has a broad range of thermal maturity (vitrinite reflectance, 0.40–2.00% Ro), which is strongly dependent on structural position. Isoreflectance lines are subhorizontal and cross-cut structure, indicating post-kinematic thermal maturation in which strata are thermally immature in uplifts and thermally overmature in the deepest synclines. The post-kinematic pattern is a product of a rapid, early phase of synkinematic thermal maturation that has been obscured by a prolonged period of post-kinematic thermal maturation. Variations in basal heat flow, structural history, and general variability of hydrocarbon source rock organic composition, particularly at low thermal maturity levels, have resulted in a modest degree of scatter in the vitrinite reflectance-depth data.

The Bowland Shale Formation in the Blacon Basin: palaeoecology and resource potential

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.

Cross-basin Mo and U analysis of the Upper Mississippian Bowland Shale, UK

Abstract The Bowland sub-basin is a target for hydrocarbon exploration, but to a large extent it remains unexplored. To determine the economic potential of the Bowland sub-basin, it is important to identify the oceanographic processes involved in the deposition of the Bowland Shale Formation in the Late Mississippian ( c. 330 Ma). Palaeoceanographic processes are known to be a major control on the development of hydrocarbon source rocks. This study investigates core (Preese Hall-1 and Becconsall-1Z) materials from the Upper Bowland Shale, and makes a comparison with previously published data (outcrop Hind Clough), all from the Bowland sub-basin, Lancashire, UK. The sedimentology and geochemistry of this formation were determined via a multi-technique approach including X-ray fluorescence, sedimentology, gamma-ray spectra, X-ray diffraction and Rock-Eval pyrolysis. Key trace metal abundances and enrichment factors were used to assess sediment provenance and to determine the bottom-water redox conditions during the deposition of the Upper Bowland Shale. Our results support interpretations of contemporaneous anoxia developing in bottom waters in at least three sites in the Bowland sub-basin. In a comparison with the Fort Worth Basin (Barnett Shale, USA), the Bowland sub-basin was apparently less restricted and deposited under a much higher mean sediment accumulation rate. Knowledge from this study will improve future resource estimates of the Bowland Shale Formation, and challenge the early assumptions that the Barnett Shale is an analogue of the Bowland Shale.

New ctenacanth sharks (Chondrichthyes; Elasmobranchii; Ctenacanthiformes) from the Middle to Late Mississippian of Kentucky and Alabama

ABSTRACT Two new ctenacanthiform sharks representing two families, Ctenacanthidae and Heslerodidae, have been identified from the Middle to Late Mississippian marine sediments from Mammoth Cave National Park, Kentucky, and two Late Mississippian marine horizons in northern Alabama. The ctenacanthid, Troglocladodus trimblei, gen. et sp. nov., is known from isolated teeth from the Middle Mississippian St. Louis Formation and Ste. Genevieve Formation of Mammoth Cave and the Late Mississippian Bangor Limestone of northern Alabama. Troglocladodus gen. nov. is characterized by broad median cusps, pronounced longitudinal cristae, multiple intermediate cusps, and labiolingually shortened tooth bases. The heslerodid, Glikmanius careforum sp. nov., is known from isolated teeth and visceral arches from the Middle Mississippian St. Louis Formation and Ste. Genevieve Formation and the Late Mississippian Haney Formation, a Hartselle Sandstone-equivalent shale interval, and Bangor Limestone. Glikmanius careforum sp. nov. has proportionately distinct teeth among species of Glikmanius, with more robust and shorter cusps. The palatoquadrate of G. careforum has a short palatine ramus, otic process that is dorsoventrally deep and less expanded antero-posteriorly similar to Heslerodus and Dracopristis, and an elongated quadrate process like Heslerodus. The Meckel’s cartilage is less dorsoventrally deep than Dracopristis. These two new ctenacanth taxa add important information on the diversity of Ctenacanthiformes suggesting three major lineages within the order. Ctenacanths have a rich fossil history from the Late Devonian to the Middle Permian evolving a variety of tooth types and small to large body sizes.

Late Mississippian (early Serpukhovian) carbon isotope record of northern Laurussia: A proposal for the Viséan/ Serpukhovian boundary

The fauna provincialism in the interval led to the appearance of some problems with the tracing of this boundary with biostratigraphic methods. Therefore, it is important to determine auxiliary non-biostratigraphic markers of the boundary. The article is focused on the evaluation of the correlation potential of carbon isotope excursions near the Viséan/Serpukhovian boundary, with special attention to the northern Laurussia region. The biostratigraphically constrained carbon isotope record is revealed from the terminal Viséan ‑ lower Serpukhovian (Mississippian) shelf successions of the northern Laurussia (six key sections located in the north of Urals and Cis-Urals, NE Europe). Onset of a negative excursion in the middle part of the Lochriea ziegleri conodont Zone (lower Serpukhovian) shows amplitude of 1–2‰ and high spatial stability, and can be used as a stratigraphic marker in regional and global correlations.

Drainage area estimates for synorogenic clastic wedges in the Central Appalachian Basin (sink) with implications for terrane accretion in the hinterland (source)

AbstractSource‐to‐sink studies typically utilize the sedimentary record preserved in basins to infer source area parameters such as estimates of drainage area and discharges of fluvial systems in the hinterland, the characterization of which remains elusive as few geomorphic elements of the hinterland are preserved. Clastic wedges within foreland basin settings often contain fluvial deposits, and the scale of fluvial architectural elements can be used to estimate drainage area and discharge within the accreted hinterland. This study uses thicknesses of fluvial architectural elements within the Late Ordovician Taconic, the Late Devonian‐Early Mississippian Acadian, and the Late Mississippian to Early and Middle Pennsylvanian Alleghanian clastic wedges, together with climatic conditions interpreted from palaeosol data, to estimate the drainage areas and discharges of the river systems which drained the hinterlands of the accreted Taconic and Acadian terrains and the Alleghanian suture of Laurentia and Gondwana. Published detrital zircon age spectra provide insight into ages of source areas of sediments as well as the timing of terrane accretion. The increase in hinterland drainage areas calculated for Late Devonian Acadian Orogeny river systems compared to Late Ordovician Taconic Orogeny river systems can be attributed to the increase in size of accreted terranes to the east of the foreland basins during that period of time. The decrease in hinterland drainage area from the Late Devonian Acadian Orogeny to the Middle to Late Pennsylvanian Alleghanian Orogeny is attributed to the westward migration of the drainage divide as the Alleghanian orogeny proceeded. It is inferred that the drainage divide migrated towards the drier leeward side of the mountain range and caused drainage basins to shrink and split into smaller drainage basins.

Middle to Late Mississippian and Early Pennsylvanian foraminiferal zonal scheme of South China—a case study from the Youjiang Basin: biostratigraphical and palaeobiogeographical implications

Middle to Late Mississippian and Early Pennsylvanian foraminiferal zonal scheme of South China—a case study from the Youjiang Basin: biostratigraphical and palaeobiogeographical implications

Provenance of Carboniferous-Permian sedimentary units in southern Mexico: evidence for peri-arc basin evolution during the Pangea assembly

ABSTRACT The Oaxacan Complex Carboniferous-Permian sedimentary cover in southern México records provenance shifts through time, reflecting the collision between Gondwana and Laurentia to amalgamate Pangea. The integration of petrological analysis and LA-ICP-MS U-Pb zircon geochronology from Santiago, Ixtaltepec and Yododeñe formations compared with adjacent terranes suggests that: (1) during the Early Mississippian, the Santiago Formation received sediments mainly from local sources such as the Oaxacan Complex and Tiñu Formation, with minor contributions from adjacent peri-Gondwana sources. The magmatic activity may have started during this time (~359–346 Ma) (2) during the Late Mississippian (Ixtaltepec Formation), detrital zircon grains of Ediacaran-Cambrian age are dominant, derived from sediments either related to the Pan-African/Brasiliano orogeny or the opening of the Iapetus Ocean; (3) during the Late Mississippian-Middle Pennsylvanian, intercalated marine volcaniclastic sandstone (Ixtaltepec Formation) provides the first record of Carboniferous arc-related volcanism reported in southern Mexico, dated between 330 and 308 Ma; (4) the early Permian Yododeñe Formation records the exhumation and erosion of the sedimentary cover during the final stage of Pangea assembly. Rhyodacitic subvolcanic sills and lavas dated at ~282–270 Ma are present throughout the succession. Volcanism and ca. 360–308 Ma detrital zircon grains could be associated with a Carboniferous magmatic arc formed by subduction of the Rheic oceanic plate beneath Gondwana. Slightly younger detrital zircon and subvolcanic rocks dated at ~300–270 Ma are linked to a western Pangea arc developed in response to the subduction of the Paleo-Pacific Ocean following Pangea assembly. Our results suggest that the Carboniferous-Permian units were deposited in a peri-arc basin, sharing sediment provenance with the Maya and Coahuila blocks, the Sierra de Juárez Complex, and northwestern South America.

Illusion of flight? Absence, evidence and the age of winged insects

Abstract The earliest fossils of winged insects (Pterygota) are mid-Carboniferous (latest Mississippian, 328–324 Mya), but estimates of their age based on fossil-calibrated molecular phylogenetic studies place their origin at 440–370 Mya during the Silurian or Devonian. This discrepancy would require that winged insects evaded fossilization for at least the first ~50 Myr of their history. Here, we examine the plausibility of such a gap in the fossil record, and possible explanations for it, based on comparisons with the fossil records of other arthropod groups, the distribution of first occurrence dates of pterygote families, phylogenetically informed simulations of the fossilization of Palaeozoic insects, and re-analysis of data presented by Misof and colleagues using updated fossil calibrations under a variety of prior probability settings. We do not find support for the mechanisms previously suggested to account for such an extended gap in the pterygote fossil record, including sampling bias, preservation bias, and body size. We suggest that inference of an early origin of Pterygota long prior to their first appearance in the fossil record is probably an analytical artefact of taxon sampling and choice of fossil calibration points, possibly compounded by heterogeneity in rates of sequence evolution or speciation, including radiations or ‘bursts’ during their early history.

Discovery of Late Mississippian (late Serpukhovian)-Early Pennsylvanian (earliest Bashkirian?) foraminiferal assemblages from the Sanandaj-Sirjan Zone, Iran: Biostratigraphic and palaeoenvironmental implications.

This study reports the new discovery of relatively abundant foraminiferal faunas from the upper Serpukhovian-lowermost Bashkirian? of the Ghaleh Formation in the Shahreza region of the Sanandaj-Sirjan Zone, Iran. Four successive assemblages spanning the upper Serpukhovian-lowermost Bashkirian? are proposed: (1) Assemblage with Biseriella minima and Eostaffellina paraprotvae; (2) Assemblage with Bradyina cribrostomata; (3) Assemblage with Parastaffella utkaensa and Plectostaffella spp., (4) Assemblage with Plectostaffella ex gr. varvariensis. The newly discovered foraminiferal assemblages of the Sanandaj-Sirjan Zone have some species in common with assemblages of the Russian Platform, Donets Basin, Urals, and Western Europe. Ikensieformis aff. mirifica, and Eostaffella igoi, and a new species Ikensieformis persiaensis sp. nov. are described. The microfacies analysis of the Ghaleh Formation limestones suggests a moderate to high-energy shallow marine warm environment, more likely of the inner ramp.

Age and provenance of the Middle Jurassic Norphlet Formation of south Texas: stratigraphic relationship to the Louann Salt and regional significance

The age and provenance of the Norphlet Formation in south Texas and its stratigraphic relationship to the Louann Salt are documented for the first time using new detrital zircon U–Pb geochronological data. Nine samples from the Hockley salt diapir and four deep wells (three in south Texas, one offshore México) yielded 1001 zircon ages and eight age populations; the most important of these are Neoproterozoic (900–541 Ma), Cambrian–Middle Mississippian, and arc-related Middle to Late Mississippian–Permian–Triassic and Triassic–Jurassic, the latter two representing the first evidence of Nazas and Guerrero arc extrusive volcanism reaching south Texas. Statistical analyses of these data and published zircon ages support the interpretation that these age populations reflect the dominance of peri-Gondwanan sources, especially the Yucatán/Maya Block and Coahuila terrane, although Laurentian sources probably contribute to specific populations. The maximum depositional age of upper Norphlet Formation sandstones is 165.5 ± 1.5 Ma (Callovian). These upper sandstones are separated from lower Norphlet sandstones by an unconformity spanning 1.5–5 myr; the lower sandstones are interbedded with halite of the Louann Salt, and may be as old as Bathonian. These new data may be of regional significance when applied to future models of the Jurassic evolution of the Gulf of Mexico. Supplementary material : The detrital zircon dataset for this study, DZmix and DZmds model parameters, DZmix statistics and references for figures are available at https://doi.org/10.6084/m9.figshare.c.6002060

The Palaeozoic genus Psephodus (Chondrichthyes, Cochliodontiformes) and the transition from teeth to tooth plates in holocephalians

Remains of the chondrichthyan Psephodus Morris and Roberts, 1862 consist mainly of isolated tooth plates. The genus has a range from the Late Devonian (Famennian) to the Late Mississippian (Serpukhovian). The most complete specimen is a partially articulated set of teeth and tooth plates of the type species, P. magnus , from the early Serpukhovian of East Kilbride, Lanarkshire, Scotland. A row of minute nodes is present along the basal margins of the Lophodus -like and Helodus -like teeth of the East Kilbride specimen. This distinguishes these teeth from typical Lophodus -like and Helodus -like teeth. As in Helodus simplex , some specimens of Psephodus display varying degrees of fusion of teeth from the same labiolingually oriented file into tooth plates. However, unlike Helodus simplex , some specimens of Psephodus display fusion of mesiodistally separated tooth plates, each representing a fused tooth file, into a larger tooth plate. Psephodus , which crosses the Devonian–Carboniferous boundary, may be ancestral to other Mississippian holocephalians, such as Cochliodus or Chondrenchelys , in which dentitions consist of a few tooth plates with only few, or no, separate teeth. An unpublished watercolour by Agassiz's artist Dinkel depicts five tooth plates, which can be designated as syntypes of P. magnus. A lectotype for Psephodus crenulatus is designated.

Age constraints of the Guttulapollenites hannonicus–Cladaitina veteadensis Biozone in Argentina reveal the first record of Early Triassic (Olenekian) palynofloras in Western Gondwana

The upper Palaeozoic basins of central-western Argentina include continuous fossiliferous successions spanning the Carboniferous-Permian interval. The palynostratigraphic biozones comprise Late Mississippian, Pennsylvanian and Cisuralian assemblages. Recently, new palynofloras of the La Veteada Formation were referred to the Lopingian (late Permian). However, they are characterized by spores and tetrads of Lundbladispora spp. and Densoisporites spp., pollen grains of Lunatisporites pellucidus, L. noviaulensis and Protohaploxypinus samoilovichii, and the alga Syndesmorion stellatum, that distinguish the post-Permian recovery floras worldwide. A new uranium-lead chemical abrasion-isotope dilution-thermal ionization mass spectrometry (U-Pb CA-ID-TIMS) age confirms the Olenekian age of this stratigraphic unit and allows the identification of the first Early Triassic palynofloras in this region of western Gondwana. Comparison and correlation with similar assemblages from the southern and northern hemispheres supports the Early Triassic turnover with an increase of lycopsid cavate spores associated with some diagnostic species of taeniate and non-taeniate bisaccate pollen.

High-pressure granulite-facies metamorphism in the junction between the Siberian and Kazakhstan-Junggar continents and implications for the assembly of Pangea

The assembly of Pangea is usually thought to be finally completed by the accretion of the Siberian continent to Laurussia, but the exact timing of the accretion is poorly constrained in global paleogeographic reconstructions, which lagged behind the Kazakhstan-Laurussian amalgamation in the latest Mississippian and was possibly coeval with, or after, the amalgamation of the Tarim and Kazakhstan-Junggar continents in the Pennsylvanian. In this respect, the geological features, such as the medium-pressure facies series metamorphism in the Irtysh Complex, NW China, from the junction between the Siberian and Kazakhstan-Junggar continents are expected to provide crucial constraints on the timing of the accretion. The metamorphic rocks in the Irtysh Complex record the high-pressure granulite-facies metamorphism with the assemblage of kyanite + K-feldspar + garnet and show a complete clockwise metamorphic P-T-t path, involving rapid burial to the peak P-T conditions of ∼11 Kbar and 800 °C at ∼300 Ma and complicated exhumation to the surface during the Permian. The Pennsylvanian (∼322–300 Ma) rapid burial was coeval with the collision of Siberian and Kazakhstan-Junggar continents, whereas the Permian exhumation was triggered by post-collisional extension and sinistral shearing and can be divided into three substages: isothermal decompression at ∼300 Ma, near-isobaric cooling (∼300–268 Ma), and decompression-cooling to the surface prior to ∼253 Ma. The high-pressure granulite-facies metamorphism suggests that the Siberian continent was amalgamated with the Kazakhstan-Junggar continent in the Pennsylvanian, almost coeval with the amalgamation of the Tarim and Kazakhstan-Junggar continents. Therefore, the assembly of Pangea was completed in the latest Carboniferous at least.

Exploring the influence of Late Mississippian to Middle Pennsylvanian tectonics on sediment transport through detrital zircon geochronology, southwestern Kansas and northwestern Arkansas

This study explores the influence of the Alleghanian-Ouachita-Marathon Orogeny and Ancestral Rocky Mountains (ARM) uplifts on sediment dispersal in the Carboniferous through sandstone compositions and detrital zircon provenance analysis. We focus on Upper Mississippian to Middle Pennsylvanian siliciclastic intervals in two areas: (1) the Hugoton Embayment in southwestern Kansas, where six samples of Upper Mississippian and Lower Pennsylvanian sandstone were collected from two boreholes and (2) the Arkoma Shelf and foreland basin in northwestern Arkansas, where nine samples were collected from Lower through Middle Pennsylvanian outcrops. We report 1544 new concordant ages, 582 ages from Kansas core and 962 ages from Arkansas outcrop samples. UPb age spectra are characterized by major Grenville (900–1300 Ma) and Taconic-Acadian (350–500 Ma) age clusters and minor components of older age groups, suggesting a persistent source in the Appalachians tied to the Alleghanian orogeny. However, by Early Pennsylvanian, the Hugoton Embayment samples see the Appalachian source partially replaced by Yavapai-Mazatzal (1800–1600 Ma) and Granite-Rhyolite (1550–1300 Ma) grains, major components of the local basement, that suggest contributions from nearby ARM uplifts. In contrast, contributions from midcontinent basement sources are limited in the Arkoma Shelf and foreland basin samples. Sandstone composition data are also consistent across all Arkoma Shelf and Upper Mississippian Hugoton Embayment samples; whereas, Lower Pennsylvanian Hugoton samples show increases in feldspar and volcanic lithic grains, consistent with input from local midcontinent age provinces. Comparison with published data suggests a similar change in provenance, from extraregional to local sediment sources, is observed across western Laurentia where ARM deformation was active. Together, new and published data support development of a major transcontinental sediment dispersal system in the Late Mississippian, controlled by Alleghanian orogenesis on the eastern Laurentian margin; however, by the Early Pennsylvanian this system was disrupted by development of the ARM.

Non‐palimpsested crowded Skolithos ichnofabrics in a Carboniferous tidal rhythmite: Disentangling ecological signatures from the spatio‐temporal bias of outcrop

AbstractA heterolithic tidalite succession yielding spring–neap bundles is newly reported from a mid‐Carboniferous (Serpukhovian) section of the Alston Formation of Northumberland, England. The rhythmite records deposition over an interval that can be confidently calibrated to at least 84 lunar days, and attests to a non‐negligible tidal range in parts of the Northwest European Seaway in the late Mississippian. The tidalite is notable for the presence of a striking crowded Skolithos ichnofabric on both bedding planes and in vertical section. Bedding plane expressions of the ichnofabric reveal true substrates of sand piles excavated during burrow construction, in addition to an apparently remarkable equal spacing between individual burrows that is shown to be genuine through pair correlation function analysis. These characteristics show that the burrowed horizons were registered by contemporaneous ichnocoenoses, with no palimpsesting of burrows. The irregular vertical distribution of burrow horizons, despite a near‐continuous semi‐diurnal record of sedimentation, is suggested to be an artefact of spatial patchiness of burrowing communities in the depositional environment; imperfectly registered in a vertical profile with high‐temporal, low‐spatial resolution. The succession proves that burrow palimpsesting is not an inevitable ichnological conclusion of sedimentary stasis, and attests to intermittent palaeoecological fidelity of the stratigraphic record at the small spatio‐temporal scales recorded at outcrop.

Channel-fill deposits in the northwestern Harz Mountains – a new facies model and the goniatite stratigraphy of the Kulm greywackes (upper Viséan, Late Mississippian, Central Germany)

Channel-fill deposits in the northwestern Harz Mountains – a new facies model and the goniatite stratigraphy of the Kulm greywackes (upper Viséan, Late Mississippian, Central Germany)

Late Paleozoic (Late Mississippian–Middle Permian) sediment provenance and dispersal in western equatorial Pangea

Late Mississippian to middle Permian sediment-dispersal networks of regional to continental scale in western equatorial Pangea, depicted here in a series of paleogeographic maps, developed in response to temporally and spatially changing influences of climate, eustasy, and a continent-wide late Paleozoic orogenic system. The orogenic system included linked Alleghanian, Ouachita-Marathon-Sonora collisional belts and associated foreland basin systems on Laurentia and magmatic arcs on Gondwana, intracratonic basement uplifts and basins of the Ancestral Rocky Mountains, flexural arches and intracratonic basins of the US midcontinent region, and basins and uplifts of the southwestern Laurentian transcurrent continental margin. Consideration of new and published U-Pb detrital-zircon datasets permits delineation of Laurentian sediment-dispersal networks of the developing supercontinent. The Transcontinental Arch deflected Late Mississippian transcontinental rivers with Alleghanian headwaters toward the southern midcontinent and nascent, deep-marine foreland basins along the Ouachita collision orogen. Pennsylvanian rivers likewise headed in the Alleghanian Orogen, transporting sediment southwest across the midcontinent and along the Alleghanian foreland basin to empty into the Arkoma Basin and Fort Worth Basin, which also received voluminous sediment from Gondwana and the Ouachita Orogen. Concomitantly, major growth of Ancestral Rocky Mountains uplifts yielded basement-derived sediment, much of which was retained in local flexural basins. Increased aridity drove ascendant eolian transport in early Permian (Artinskian) time, just as lowstand desiccation of a midcontinent seaway exposed unconsolidated silt and sand derived from eastern, western, and southern sources in an extensive interior desert sink. Eolian transport within the interior desert further mixed and deflated the already-cosmopolitan sediment, pushing it southwest toward the Permian Basin and westward beyond the Ancestral Rocky Mountains. Intercepted by newly developed monsoonal circulation, the deflated sediment came to reside in erg systems along the western marine margin of Pangea. Subtropical Pennsylvanian transcontinental fluvial networks were similar to those of modern big river systems of the eastern and midcontinent United States that drain toward the Gulf of Mexico. In contrast, Permian drainage networks yielding sediment to a continental desert more resembled Pleistocene sediment routes of the Arabian Plate; there, intermittent wadis draining western rift highlands and big rivers of the Mesopotamian foreland contribute sediment to Arabian eolian sands via zonal and monsoonal surface winds to create widespread sand seas of mixed Eurasian and Arabian provenance.