Moscovian Time Research Articles

SIGNIFICANCE FOR INTERNATIONAL CORRELATION OF THE PERAPERTÚ FORMATION IN NORTHERN PALENCIA, CANTABRIAN MOUNTAINS. TECTONIC/STRATIGRAPHIC CONTEXT AND DESCRIPTION OF MISSISSIPPIAN AND UPPER BASHKIRIAN GONIATITES

Small ammonoid assemblages are recorded from the Perapertú Formation in northern Palencia. This is a mudstone unit with local platform limestones characterised by carbonate debris flows on the limestone margins. This unit, of Late Bashkirian to Early Moscovian age, participates in a series of southwards verging thrust slicesNorth of a major fault zone which originated as the head (leading edge) of a large thrust sheet with an internal deformation consisting of thrust slices and at least one nappe structure. Opposed vergencies at the head of this major thrust sheet (Carrionas Thrust Front) and the Ruesga Fault which locally modifies its trace, mark the position where the northern branch of the Cantabric-Asturian arcuate fold belt has overridden the southern branch in early Westphalian (Langsettian) times. The chronostratigraphic significance of the Perapertú Formation is discussed in the context of marine-terrestrial correlations for the Late Bashkirian-Early Moscovian time interval. It is concluded that the evidence from NW Spain suggests a position of the base of the Moscovian at the level of basal Westphalian or even within the highest Namurian. A brief analysis of the literature shows this position to be different to some of the correlations admitted in recent publications.A newly discovered goniatite fauna from the lower part of the Perapertú Formation contains Brannerocera ssp. indicating Late Bashkirian to earliest Moscovian, and Deleshumardites cantabricus Kullmann gen. et sp. nov. This fauna is figured and described in conjunction with the new subfamily Dombaritinae Kullmann (family Delepinoceratidae).

Dating of lithospheric buckling: 40Ar/39Ar ages of syn-orocline strike–slip shear zones in northwestern Iberia

Orogenic curvature is a ubiquitous feature of mountain belts, and the plate tectonic and geodynamic setting responsible for the development of curved orogens is a subject of debate. In order to distinguish between different models of orocline formation it is necessary to tightly constrain the absolute timing of oroclinal development. However, determining the absolute (isotopic) timing of oroclinal bending is challenging. The most direct method available to constrain the time interval during which an orocline formed is to obtain absolute age constraints on fabrics generated within syn-orocline strike–slip shear zones that accommodated rotations around a vertical axis during the development of crustal or lithospheric scale orogenic curvature. Here we present a data set of 40Ar/39Ar ages obtained from five shear-zones, some of which display curved traces parallel to the Cantabrian Orocline structural grain in NW Iberia and are interpreted to have been generated coevally to it. The 40Ar/39Ar ages were obtained by laser-rastering induced step-heating on single muscovite crystals that grew synkinematically during shearing. All five samples yielded ages that cluster tightly at 308±3Ma providing direct evidence for the age of oroclinal bending. This age is consistent with the age constraints obtained from paleomagnetic and structural data that place the onset of oroclinal bending in Moscovian times. Our 40Ar/39Ar age determinations therefore provide a reliable absolute constraint on the age of buckling of the Variscan orogen around a vertical axis and provide further evidence that oroclinal bending is unrelated to Variscan convergence/collision or the subsequent extensional collapse of the mountain belt.

A Late Carboniferous algal mound from the Tarim Basin, NW China: internal structure and palaeoecology

A Beresella‐dominated algal mound and its internal construction from Paojianggou, southwestern Tarim Basin, NW China are studied for the first time. This algal mound was constructed during the early–middle late Moscovian and its age is constrained by fusulinids of the Fusulina kamensis and F. quasicylindrica zones of middle Pennsylvanian age. The mound substrate beds are composed of crinoid and brachiopod grainstones. Crinoid bank and brachiopod‐dominated skeletal shoals indicate a high‐energy environment and produced a local topographic high on which the mound grew. Komia bafflestone of the foremound facies further increased the relief of the crinoid bank on the seafloor. The lower part of the mound framework is dominated by Shamovella–Archaeolithoporella boundstone, while the main (upper) mound framework consists predominantly of Beresella boundstone. Grainstone–packstone characterizes the windward mound flank facies. The mound capping facies include a lower skeletal packstone–wackestone and an upper lagoon facies marlstone and black shale. Various algal colonies performed different roles in the formation of the mound. Komia colonies were the mound constructors that baffled higher energy currents and entrapped fine sediment. Archaeolithoporella, Shamovella and possibly microbes (cyanobacteria) acted as the binders to stabilize mud and fine‐grained sediment. Beresella colonies were the major framework constructors whose network entrapped the mud to build the mound.The growth of the Paojianggou mound in the Tarim Basin has undergone three major algal colonization stages: Komia baffling, laminar Archaeolithoporella and Shamovella encrusting and binding, and Beresella binding and stabilizing. The Paojianggou mound developed in a protected lagoonal position behind the shoals and grew during a short rise in sea level followed by a long‐period sea‐level fall. Its demise was caused by terrigenous siliciclastic input due to regional tectonic uplifting in the Tarim Basin during the latest Moscovian time. Copyright © 2012 John Wiley & Sons, Ltd.

Basin evolution and coal geology of the Donets Basin (Ukraine, Russia): An overview

Abstract The Donets Basin is a major coal-mining district in eastern Ukraine and adjacent portions of Russia. It comprises the Donbas Foldbelt, which is the uplifted and compressionally deformed part of the Pripyat–Dniepr–Donets (PDD) Basin, and the significantly less deformed Western Donbas region. The PDD Basin is a Late Devonian rift structure located within the East European Craton. Thick coal-measures formed during the post-rift stage of the basin in Serpukhovian to Moscovian times, when about 130 seams, each with a thickness over 0.45 m, have been deposited. Early Serpukhovian coal accumulated in a relatively narrow shore-zone. It is rich in inertinite and liptinite and very low in ash. Bashkirian and Moscovian coal have a significantly wider lateral extension and are generally rich in vitrinite. Bashkirian and Moscovian coal seams usually have high ash yields (12–18%) and high sulfur contents (2.5–3.5%), but these data vary significantly depending on peat facies. Coal rank ranges from subbituminous to anthracite and is mainly controlled by the depth of the seams and the heat flow during maximum (Permian) burial. Permo-Triassic thermal events locally overprinted the resulting coalification pattern. Coked coal occurs at the contact to presumed Permian sills and dikes southwest of Donetsk. Deep Permian burial was followed by major Permian and Mesozoic uplift events. The Donets Basin hosts proven reserves in the order of 60 Gt at the exploitable depth. The thickness of coal seams currently mined is in the range of 0.6 to 2.5 m. Production during 2009 was 68.7 Mt in the Ukrainian and 4.9 Mt in the Russian part of the basin. Coal mines in the Donets Basin are among the gassiest in the world. The average methane content of coal is 14.7 m³/t, but numerous seams have significantly higher gas content. The high methane content presents a severe mine safety problem. On the other hand, it represents also a high potential for coal mine bed methane projects. Emissions of coal gas released by mining and related structurally induced underground hazards (coal and gas outbursts) are a major problem for safe and efficient coal exploitation in the basin.

Rainforest collapse triggered Carboniferous tetrapod diversification in Euramerica

Abrupt collapse of the tropical rainforest biome (Coal Forests) drove rapid diversification of Carboniferous tetrapods (amphibians and reptiles) in Euramerica. This finding is based on analysis of global and alpha diversity databases in a precise geologic context. From Visean to Moscovian time, both diversity measures steadily increased, but following rainforest collapse in earliest Kasimovian time (ca. 305 Ma), tetrapod extinction rate peaked, alpha diversity imploded, and endemism developed for the first time. Analysis of ecological diversity shows that rainforest collapse was also accompanied by acquisition of new feeding strategies (predators, herbivores), consistent with tetrapod adaptation to the effects of habitat fragmentation and resource restriction. Effects on amphibians were particularly devastating, while amniotes (‘reptiles’) fared better, being ecologically adapted to the drier conditions that followed. Our results demonstrate, for the first time, that Coal Forest fragmentation influenced profoundly the ecology and evolution of terrestrial fauna in tropical Euramerica, and illustrate the tight coupling that existed between vegetation, climate, and trophic webs.

Tropical marine climate during the late Paleozoic ice age using trace element analyses of brachiopods

The late Paleozoic ice age can be considered an important analogue to the modern ice age, but comparisons between the two time intervals have been hampered by the difficulty of resolving climatic changes that occur over short (e.g., seasonal) time scales in the Paleozoic record. As a first step toward overcoming these limitations, this study employed Mg/Ca trace element ratios sampled across the growth bands of six specimens of the brachiopod Composita to assess differences in tropical marine mean temperature and seasonality in Viséan and Moscovian time. These time intervals bracket the onset of the late Paleozoic ice age, which occurred in mid-Serpukhovian time, and thus provide a snapshot of climate changes from a greenhouse to an icehouse world. Shells were screened for diagenetic alteration by cathode luminescence and by comparing the values of Mn, Sr, Na, and B to those reported for modern brachiopods. In addition, a 87Sr/ 86Sr value, measured for one specimen, agreed with a published strontium isotope curve for the late Paleozoic Era. Both the mean and range of Mg/Ca values were larger in Viséan than Moscovian time, suggesting colder and less seasonal temperatures during the late Paleozoic ice age. The decline in seasonality was due to a greater proportional reduction of maximum values (which presumably represent summer temperatures) than minimum values. These relative differences between the pre-ice age and ice age tropical climate provide a first step toward understanding the broad patterns of seasonal-scale changes in temperature during a critical time in Earth's history.

BOTHROPHYLLUM CONICUM (FISCHER, 1837) (RUGOSA) FROM THE MIDDLE AND UPPER CARBONIFEROUS OF THE DONETS BASIN

The species Bothrophyllum conicum (Fischer, 1837) has been found in the limestones O6 of the Donets Basin for the first time. The species В. dobrolyubovae Yakovlev, identified here previously from the Middle and Upper Carboniferous, is considered now to be a junior synonym of the described species. Study of the evolutional transformations in the phylogenetic trend B. pseudoconicum - B. conicum that occured in Moscovian time allows marking the important level of correlation between the Donets Basin and Moscow syneclise.

Carboniferous-Permian long-term sea-level change inferred from Panthalassan oceanic atoll stratigraphy

This paper traces late Palaeozoic second-order sea-level change based on the stratigraphy of the Akiyoshi Limestone, an accreted Carboniferous-Permian Panthalassan atoll carbonate succession in SW Japan. The estimated subsidence of a volcanic edifice and the variable rate of carbonate accumulation reveal the long-term sea-level history of the late Palaeozoic. During Bashkirian time, just after the lowstand stage at the mid-Carboniferous boundary, a slow progressive long-term sea-level rise began. This sea-level rise then increased greatly during Moscovian time. The following Kasimovian to Asselian interval represents a stable highstand stage. Beginning in the Sakmarian, sea level fell slowly and became stable in the Yakhtashian (= Artinskian). This stable sea level was maintained into the Midian (= Capitanian), although a small-scale sea-level rise of approximately 55–70 m is recognized in the Murgabian (= Wordian). The most noteworthy aspect of this change of sea level is the rapid sea-level rise during the Moscovian that created a very large accommodation space and resulted in accumulation of a thick carbonate succession. The eustatic rise from the earliest Bashkirian lowstand to the latest Moscovian highstand had an amplitude of approximately 230–240 m. Such a large-scale eustatic rise in the long-term sea-level change would most likely be caused by greater uplift of the ocean floor along the mid-oceanic ridges, as a result of an increase in the production of oceanic crust during that time.

Palaeofloristics of Middle Pennsylvanian medullosaleans in Variscan Euramerica

Medullosaleans were an abundant and widely distributed group of seed-plants in the Moscovian palaeotropical wetland forests (‘coal forests’). Using mainly a combination of cluster analysis and Detrended Correspondence Analysis, the distribution of medullosalean species has revealed five distinct palaeofloristic units within Variscan Euramerica. Two palaeofloristic units characterise lowland paralic areas: the Rhine Palaeoprovince found in parts of the Variscan Foreland and the Donets Basin; and the Iberia Palaeoprovince found in northern Spain and Portugal. The Silesia Palaeoprovince represents somewhat lower-diversity medullosalean macrofloras, mainly associated with more marginal areas of the Variscan Foreland. Intramontane basins are characterised by two palaeofloristic units that are quite distinct from those of the more lowland areas, and to a lesser-extent different from each other: the Saar-Lorraine and Central Bohemia Palaeoprovinces (the latter found in the Intrasudetic Basin and Zwickau, as well as Central Bohemia). Except for the appearance of the Iberia Palaeoprovince in late Moscovian times, the basic palaeofloristic structure of Variscan Euramerica remained essentially unchanged through the Moscovian Age. Those palaeofloristic changes that did take place mainly reflect localised increased influxes of sediment or changes in water-table. The palaeofloristic data provides no evidence of regional-scale environmental changes taking place, such as marked climate-change, regional uplift, or major palaeolatitudinal change.

Carboniferous normal faults in the Eastern Pyrenees: evidences and age constrains of syn-orogenic Variscan extension

In low grade rocks of the Eastern Pyrenees syn-orogenic Variscan extension is achieved by kilometric scale low-angle brittle normal faults. Evidence of these faults is generally depicted by subtractive contacts between Devonian upon Cambro-Ordovician rocks. Normal faults are cut by a Variscan granodiorite pluton and U-Pb available geochronologic data of the granodiorite, 305 Ma ± 3 [30], indicates that the age of extension can be attributed to Moscovian times. Extension postdates the main period of Variscan crustal thickening and occurs in N-S to NE-SW direction, roughly perpendicular to the trend of the main Variscan compressional structures. Such relationships point out that the onset of Variscan extension occurs after compression and prior to the granodiorite emplacement and to the deposition of post-orogenic volcanics.

The Upper Paleozoic preflysch and overthrusting in the Türkstan-Alay ranges, southern Fergana

The Upper Paleozoic preflysch sedimentary rocks in the Turkstan-Alay ranges are combined in a common section with limestone of autochthon and synsedimentation carbonate nappes, thus forming the upper-most layers of the stratigraphic section of the latter. By their lithology, relatively small thickness, facies variability, and position at the boundary between carbonate and flysch-olistostrome sequences (in the autochthon), these rocks correspond to a certain extent to preflysch of the Urals and the Mediterranean Alpine Belt. This association of clayey, carbonate, and terrigenous rocks is strictly constrained in stratigraphy (the upper portion of the lower Moscovian substage and the lower portion of the upper Moscovian substage) and localization (the southern slopes of carbonate platforms). The formation of this rock association immediately predated the Late Paleozoic overthrusting and deposition of terrigenous flysch. In paleotectonic terms, preflysch is an indicator of the initial stage of tectonic and magmatic activation that led to the replacement of carbonate sedimentation with deposition of terrigenous and clayey sediments, coeval volcanism, and stratiform ore formation. The following sequence of events has been outlined in the Early and Middle Carboniferous: (1) thrusting of volcanic-sedimentary rocks filling troughs over the northern margins of carbonate platforms, (2) lateritic weathering and deposition of marine bauxite in the Bashkirian and early Moscovian, (3) repeated overthrusting and deposition of preflysch on southern slopes of platforms, (4) invasion of the frontal flysch trough from the south, (5) scouring of preflysch and the underlying limestone, and (6) formation of flysch-olistostrome sequences and tectonic and gravity nappes in the late Moscovian time. This interpretation takes into account the southward vergence of thrust sheets and nappes, the structure and localization of allochthonous fragments of marginal zones of carbonate platforms, and the pre-Bashkirian thrusting of volcanic and sedimentary rocks over the condensed pelagic deposits of the Shalan Group. It is suggested that bauxite and preflysch materials had the same source and were deposited in the Middle Carboniferous on the offshore carbonate shoals.

DIACHRONOUS APPEARANCES OF THE PENNSYLVANIAN FUSULINID PROFUSULINELLA IN EURASIA AND NORTH AMERICA

Abstract The Pennsylvanian fusulinid genus Profusulinella appeared in sub-Arctic North America in Medial Atokan (=Early Moscovian) time, roughly 4–5 My later than its oldest known occurrence in the Eurasian-Arctic province. The genus originated in the latter area in late Early Bashkirian time and then underwent significant diversification, so that by Early Moscovian time a range of shell morphologies existed. The first sub-Arctic North American species in the genus are interpreted as immigrants from Eurasia, with their migration through the Franklinian corridor having been facilitated by generally east-to-west currents during a glacio-eustatic flooding event. Previous work suggested that North American Profusulinella spp. may have derived from a local ancestor such as Eoschubertella. This possibility seems unlikely given that early North American species in Profusulinella are very similar to age-equivalent Eurasian forms, that they differ from North American Eoschubertella in a number of morphologic featu...

The two-phase model applied to some U.S. coals

The Donets Basin is a major coal-mining district in eastern Ukraine and adjacent portions of Russia. It comprises the Donbas Foldbelt, which is the uplifted and compressionally deformed part of the Pripyat–Dniepr–Donets (PDD) Basin, and the significantly less deformed Western Donbas region. The PDD Basin is a Late Devonian rift structure located within the East European Craton. Thick coal-measures formed during the post-rift stage of the basin in Serpukhovian to Moscovian times, when about 130 seams, each with a thickness over 0.45 m, have been deposited.Early Serpukhovian coal accumulated in a relatively narrow shore-zone. It is rich in inertinite and liptinite and very low in ash. Bashkirian and Moscovian coal have a significantly wider lateral extension and are generally rich in vitrinite. Bashkirian and Moscovian coal seams usually have high ash yields (12–18%) and high sulfur contents (2.5–3.5%), but these data vary significantly depending on peat facies.Coal rank ranges from subbituminous to anthracite and is mainly controlled by the depth of the seams and the heat flow during maximum (Permian) burial. Permo-Triassic thermal events locally overprinted the resulting coalification pattern. Coked coal occurs at the contact to presumed Permian sills and dikes southwest of Donetsk. Deep Permian burial was followed by major Permian and Mesozoic uplift events.The Donets Basin hosts proven reserves in the order of 60 Gt at the exploitable depth. The thickness of coal seams currently mined is in the range of 0.6 to 2.5 m. Production during 2009 was 68.7 Mt in the Ukrainian and 4.9 Mt in the Russian part of the basin. Coal mines in the Donets Basin are among the gassiest in the world. The average methane content of coal is 14.7 m³/t, but numerous seams have significantly higher gas content. The high methane content presents a severe mine safety problem. On the other hand, it represents also a high potential for coal mine bed methane projects. Emissions of coal gas released by mining and related structurally induced underground hazards (coal and gas outbursts) are a major problem for safe and efficient coal exploitation in the basin.