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Ioannina, Greece

Kalvoda J.,Masaryk University | Babek O.,Palacky University | Devuyst F.X.,Lime Technology | Sevastopulo G.D.,Trinity College Dublin
Bulletin of Geosciences

A study of three carbonate and carbonate-siliciclastic sections at the Tournaisian-Viséan (Tn-V) boundary in the Dublin Basin (Ireland), has been carried out using high resolution foraminiferal biostratigraphy and gamma-ray spectrometry. The aim was to identify the Tn-V boundary and trace correlatable log patterns in different environmental settings of the Dublin Basin. The foraminiferal fauna in the heterozoan and mixed heterozoan-photozoan (foramderm and bryonoderm extended) late Tournaisian shallow ramp facies and its calciturbidite products is taxonomically impoverished and resembles the similar impoverished foraminiferal associations of western Canada interpreted as reflecting upwelling zones. The increase of photozoan bioclasts which occurs in the latest Tournaisian is accompanied by the entry of important foraminiferal guides of the Tn-V boundary interval. The combination of biostratigraphic and spectral gamma-ray data proved to be a useful tool for the identification of the sequence boundary just below the Tn-V boundary across the different environmental settings of the Dublin Basin. The recognized sea-level fall is correlatable across the London Brabant Massif from western Ireland through to England, South Wales and Belgium. Source

Groves J.R.,Lime Technology | Wang Y.,CAS Nanjing Institute of Geology and Palaeontology
Journal of Paleontology

A comprehensive, high resolution stratigraphic database of fusulinoidean foraminifers reveals that this group of protists suffered extreme losses during the Guadalupian extinction. Most species (88%) were eliminated gradually over the course of 9 myr during the Wordian and Capitanian ages. A pulse of greatly elevated per capita extinction frequency occurred during the last million years of the Capitanian (260-259 Ma). Contrary to prevailing opinion, the end-Capitanian event did not preferentially eliminate large, morphologically complex species in the families Schwagerinidae and Neoschwagerinidae, because most species in those families were already extinct. Rather, 69 percent of the species eliminated at the end of the Capitanian were small, morphologically conservative representatives of the Ozawainellidae, Schubertellidae and Staffellidae. Survivors from these families comprised the low-diversity association of Wuchiapingian fusulinoideans. Schubertellids, and to a lesser extent ozawainellids, diversified in the late Wuchiapingian and Changhsingian ages before the final demise of fusulinoideans during the end-Permian mass extinction. The Wordian-Capitanian fusulinoidean attrition might have been caused by photosymbiont loss and habitat reduction stemming from an interval of global cooling termed the Kamura event (∼265-259.5 Ma), although the onset of fusulinoidean diversity decline predates geochemical evidence for the beginning of the Kamura event by ∼3 myr. The end-Capitanian extinction pulse might reflect environmental deterioration from the combined effects of global cooling, Emeishan effusive volcanism and sea-level lowstand. Copyright © 2013, The Paleontological Society. Source

Babek O.,Masaryk University | Babek O.,Palacky University | Kalvoda J.,Masaryk University | Cossey P.,Staffordshire University | And 3 more authors.
Sedimentary Geology

We studied the relationships between stratigraphic distribution of outcrop spectral gamma-ray, magnetic susceptibility and carbonate facies stacking patterns across the regionally significant transgressive-regressive cycle at the Tournaisian/Viséan boundary (Tn/V, early Carboniferous) in southern Great Britain and Ireland (South Wales, North Staffordshire and Dublin Basin). The Tn/V boundary coincides with a prominent climatic pulse connected with the Late Paleozoic glaciation of Gondwana. The aim was to correlate the gamma-ray and magnetic susceptibility log patterns in carbonate ramp- and basin settings and discuss the global/regional nature and magnitude of this transgressive-regressive cycle. A robust ramp-to-basin correlation was produced based on the log patterns, facies stacking patterns and foraminifer biostratigraphy. The concentrations of K and Th, the "clay" gamma-ray values and, partly, magnetic susceptibility are dependent on facies and show systematic changes along the inferred bathymetric profile from inner ramp to outer ramp and basin. A model of carbonate productivity-driven dilution of fine-grained siliciclastics in CaCO3 as the major control on the petrophysical patterns is discussed. The cleaning-up and cleaning-down petrophysical trends are related to down-dip and up-dip shifts of the carbonate factory with changing relative sea level. In middle-to-outer ramp and basin settings, this generates petrophysical trends just opposite to Paleozoic carbonate shelves where peaks in magnetic susceptibility are known to be associated with peak regressions. A distinct, late Tournaisian to early Viséan regressive-to-transgressive cycle with a prominent sequence boundary located close to the Tn/V stage boundary can be seen in the sections. Glacioeustatic origin of the sequence boundary is inferred from its correlation with Tn/V boundary sections from Europe, carbon isotope data from South China and the glacial deposits in the southern hemisphere mentioned by previous authors. © 2012 Elsevier B.V. Source

Rak S.,Charles University | Kalvoda J.,Masaryk University | Devuyst F.-X.,Lime Technology
Geologica Carpathica

Eleven trilobite species (Archegonus (Archegonus) aequalis philliboloides R. Hahn, 1967, Bollandia persephone (Hahn & Hahn, 1970), Bollandia cf. megaira (Hahn & Hahn, 1970), Liobole (Panibole) cf. jugovensis (Osmólska, 1968), Liobole (Sulcubole) glabroides (Richter & Richter, 1949), Semiproetus (Macrobole) drewerensis latipalpebratus (Osmólska, 1973), Proliobole vigilax (Chlupáč, 1961), Cyrtoproetus (Cyrtoproetus) cracoensis cracoensis (Reed, 1899), Carbonocoryphe (Carbonocoryphe) bindemanni Richter & Richter, 1950, Tawstockia (Beleckella) milleri (Hahn & Hahn, 1971), Cummingella (Cummingella) cf. auge Hahn & Hahn, 1968) are described for the first time from the shales of the Březina Formation in Mokrá Quarry near Brno (Bohemian Massif, Moravian Karst). This typical trilobite association-comparable to that previously described from the Erdbacher Kalken of Steeden in Hessen (Germany)-was found during excavation in the Mokrá Quarry but they do not come from the exact Tournaisian-Visean boundary. Stratigraphical correlation and comparison of material is mentioned below, as is the history of the trilobite research from the Moravian Karst. Source

Groves J.R.,Lime Technology | Pike M.,University of Northern Iowa | Westley K.,TestAmerica Inc.

Late Paleozoic fusuline foraminifera are thought to have hosted photosymbionts, as do modern larger foraminifera, but the ancient host-symbiont relationship has never been demonstrated conclusively. Among modern larger foraminifera, deeper-dwelling species exhibit large surface-to-volume ratios in order to maximize the amount of sunlight that can be captured for use by photosymbionts. Shallower-dwelling species exhibit smaller surface-to-volume ratios in order to limit incoming sunlight, especially ultraviolet radiation. If modern symbiont-bearing foraminifera are appropriate analogues for fusulines, then deeper-dwelling fusulines ought to exhibit larger surface-to-volume ratios than shallower-dwelling ones. This prediction was tested by analyzing fusuline shells from the Virgilian (Upper Pennsylvanian) Oread, Lecompton and Deer Creek cyclothems in Kansas. Specimens from deeper-water "middle" limestones exhibit significantly larger surface-to-volume ratios than those from regressive "upper" limestones, and specimens with the smallest surface-to-volume ratios occur in shoaling deposits at or near the tops of regressive limestones. Shell shape does not vary predictably with depth of habitat. Rather, changes in surface-to-volume ratio were accomplished mainly by changes in size, with larger shells always characterized by smaller ratios. The observed trend is significantly nonrandom with respect to depth of habitat (p = 0.012). The trend is not likely the result of hydrodynamic adaptation, postmortem size sorting or size decrease along a bottom oxygen gradient. It most likely reflects geometric optimization for photosymbiosis. Copyright © 2012 SEPM (Society for Sedimentary Geology). Source

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