Middle Moscovian climate of eastern equatorial Pangea recorded in paleosols and fluvial architecture
Authors:
Opluštil et al
Abstract:
Fluvial architecture in conjunction with the morphology, petrographical, mineralogical and geochemical composition of intercalated paleosols of the Middle Moscovian upper Radnice Member of the continental Kladno-Rakovník Basin, Czech Republic, were studied in order to decipher climatic signals in the eastern Pangea region during the Late Paleozoic Ice Age. Analysis of architectural elements reveals vertical changes from strongly amalgamated channel fills of bedload-dominated braided streams, to isolated ribbon-like meandering channel fills in mud-dominated floodplain strata. The resulting large scale fining upward cycles separated by laterally widespread bounding surfaces are interpreted as having been formed in response to allocyclic processes driven by variable intensities of precipitation which affected the density of vegetation cover across the landscape and, in turn, the amount and character of sediment supply. Bedload-dominated parts of the cycles were deposited during periods of low water tables and sparse vegetation, whereas periods of maximum precipitation resulted in higher water tables and a greater density of vegetation cover, which, in turn stabilized the floodplains and fixed streams to narrow meandering/anastomosing channels in mud-dominated floodplain strata. Associated paleosols resemble modern Vertisols, which form under seasonal precipitation in modern settings. However, coeval formation of inertinite-rich peat represented by histosols and gleyed low chroma Vertisols in the stratigraphically lowest paleosol succession occurred under overlapping marginal conditions for the climatically different types of soils (i.e., under a seasonal climate where precipitation exceeds evapotranspiration for 6 to 8 months out of the year). Mean annual precipitation calculated from the geochemistry of B horizons of Vertisols (CALMAG proxy) varies between 1815 and 1730 mm/yr.
Late Pennsylvanian aridification on the southwestern margin of Gondwana (Paganzo Basin, NW Argentina): A regional expression of a global climate perturbation
Authors:
Gulbranson et al
Abstract:
Paleosols of the Paganzo Group preserve a shift from the cool climate of the glaciated high-latitudes of Gondwana to a long-term aridification punctuated by shorter-term fluctuations in moisture regime in the late Carboniferous. A quantitative reconstruction of paleoclimate inferred from the major element chemistry of paleosol horizons and the stable isotope geochemistry of soil-formed minerals and organic matter indicates that the climate varied substantially during deglaciation along the southwestern margin of Gondwana in the Middle Pennsylvanian including two geologically abrupt shifts to notably drier conditions. This dynamic climate terminates in a dry subhumid moisture regime characterized by steppe/dry scrub floral provinces. Quantitative estimates of net primary production during the post-glacial interval inferred from paleosol major element geochemistry are consistent with a mesic soil temperature regime, in agreement with paleotemperatures inferred from pedogenic goethite δD and δ18O. Contemporaneous aridification is well expressed in paleotropical continental records with Middle to Late Pennsylvanian aridification coincident with an abrupt evolutionary change in many marine and terrestrial species. The synchrony of aridification between the high and low paleo-latitudes and concomitant major restructuring of some ecosystems suggests that a paleoclimate change of global nature occurred during the Moscovian and Kasimovian.
Paleobiology and paleoecology of Palaeoaplysina and Eopalaeoaplysina new genus in Arctic Canada
Authors:
Anderson et al
Abstract:
Palaeoaplysina is an enigmatic platy macrofossil with a cellular skeleton and internal canal system common to upper Carboniferous–lower Permian reefs of the northern hemisphere. Its rapid flourishing from the Moscovian and subsequent extinction near the end of the Sakmarian, as well as its unique combination of physical features, are poorly understood. In addition to Palaeoaplysina reefs forming major petroleum exploration targets in Russia, Palaeoaplysina is abundant and well preserved in the Sverdrup Basin in the Canadian Arctic Archipelago. A new genus of Palaeoaplysinaceae, Eopalaeoaplysina n. gen., is also widespread in the Sverdrup Basin and identified based on a simple morphology with broad canals distributed in roughly even rows. The distribution of paleoaplysinids in strata from the Moscovian to the Sakmarian in the Sverdrup Basin reveals Eopalaeoaplysina and Palaeoaplysina represent two distinct reef-building forms with an increase in complexity over time. The aragonitic composition of Palaeoaplysina, in addition to its distribution within the photic zone and differentiated cellular skeleton, suggests paleoaplysinids were ancestral red algae. Palaeoaplysina occurs in both low-energy back-reef and higher-energy reef front facies. Preserved thin edges of Palaeoaplysina plates indicate it was encrusting, at least in low-energy conditions. The exclusion of Palaeoaplysina from the late Paleozoic tropics and the southern hemisphere, its rapid appearance and proliferation, and its eventual extinction may point towards an evolutionary niche optimized for warm-water conditions at unusually high latitudes along the western margin of Pangea.
Edestus, the Strangest Shark? First Report from New Mexico, North American Paleobiogeography, and a New Hypothesis on its Method of Predation more
Author:
Itano
Abstract:
Two incomplete teeth of the chondrichthyan genus Edestus are reported. They were collected fromthe Gray Mesa Formation (Pennsylvanian, late Desmoinesian), Socorro County, New Mexico, in 1996.The better-preserved tooth belongs to Edestus sp. cf. E. heinrichi. The other cannot be identifiedbeyond the generic level. These are the first specimens of the genus known to be reported from NewMexico. The only other specimens known from the Rocky Mountain region are from Colorado. Boththe New Mexico and Colorado collections are from marine limestones. In North America, Edestus ismost common in marine black shales of the Illinois Basin, but to date has not been found in marinegray shales or limestones in the Appalachian Basin. The failure to find Edestus remains in the Appalachian Basin is probably the result of the precise timing and limited extent of marine incursionsinto that region. Edestus might have been less tolerant of restricted marine environments than otherchondrichthyans collected from Pennsylvanian deposits in the Appalachian Basin. The function of thesymphyseal tooth whorls of Edestus is obscure, inasmuch as their convex curvature makes them poorly-adapted to the “scissors” function proposed in some previous studies. Alternatively, it is pro-posed here that Edestus teeth were used to disable prey with a slicing action carried out with a verticalmotion of the head, with jaws fixed relative to each other, and not with a scissors-like action of thejaws moving relative to each other. This hypothesis is supported by the author’s observations of wearand damage on the teeth of the holotype of Edestus newtoni. Helicoprion tooth whorls are similar to those of Edestus in that they contain sharp, serrated tooth crowns along the convex margin of the whorls and extend outside the oral cavity. The whorls might have functioned similarly to the mannerthat is hypothesized for Edestus,that is, to slash prey with a downward motion of the head, with jawsfixed. This proposed similarity in form and function would likely represent convergence
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Cranial anatomy, ontogeny, and relationships of the Late Carboniferous tetrapod Gephyrostegus bohemicus Jaekel, 1902
Authors:
Klembara et al
Abstract:
We review the cranial morphology of the Late Carboniferous terrestrial tetrapod Gephyrostegus bohemicus from the coal deposits of the Nýřany Basin in the Czech Republic. Gephyrostegus is known from several skulls ranging in length from about 25 mm to about 58 mm (holotype). The narrow skull is about twice as long as wide and shows a well-ossified quadrate and articular, but no evidence of braincase ossification. Autapomorphic features include a pustular ornamentation on some skull table bones, and a plate-like tabular process exhibiting a fine dorsal pitting. Gephyrostegus shares with Bruktererpeton fiebigi (Late Carboniferous, Germany) the presence of low, anteromedially to posterolaterally orientated sharp ridges on the posteroventral surface of the vomer. It shares with seymouriamorphs a rectangular, transverse pterygoid process and closely packed, radially arranged rows of small denticles on the palate. A phylogenetic analysis retrieves Gephyrostegidae (Gephyrostegus, Bruktererpeton) as sister group to Seymouriamorpha, although this wider clade receives low bootstrap support.
