Rezsu u. 83


Rezsu u. 83

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Kraus S.H.,Free University of Berlin | Brandner R.,University of Innsbruck | Heubeck C.,Free University of Berlin | Kozur H.W.,Rezsu u. 83 | And 3 more authors.
Fossil Record | Year: 2013

The latest Permian mass extinction, the most severe Phanerozoic biotic crisis, is marked by dramatic changes in palaeoenvironments. These changes significantly disrupted the global carbon cycle, reflected by a prominent and well known negative carbon isotope excursion recorded in marine and continental sediments. Carbon isotope trends of bulk carbonate and bulk organic matter in marine deposits of the European Southern Alps near the low-latitude marine event horizon deviate from each other. A positive excursion of several permil in δ13Corg starts earlier and is much more pronounced than the short-term positive δ13Ccarb excursion; both excursions interrupt the general negative trend. Throughout the entire period investigated, δ13Corg values become lighter with increasing distance from the palaeocoastline. Changing δ13Corg values may be due to the influx of comparatively isotopically heavy land plant material. The stronger influence of land plant material on the δ13Corg during the positive isotope excursion indicates a temporarily enhanced continental runoffthat may either reflect increased precipitation, possibly triggered by aerosols originating from Siberian Trap volcanism, or indicate higher erosion rate in the face of reduced land vegetation cover. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Moix P.,University of Lausanne | Beccaletto L.,Bureau de Recherches Géologiques et Minières | Masset O.,ETH Zurich | Kozur H.W.,Rezsu u. 83 | And 4 more authors.
Turkish Journal of Earth Sciences | Year: 2011

Our paper aims to give a thorough description of the infra-ophiolitic mélanges associated with the Mersin ophiolite. We propose new regional correlations of the Mersin mélanges with other mélange-like units or similar series, located both in southern Turkey and adjacent regions. The palaeotectonic implications of the correlations are also discussed. The main results may be summarized as follows: the infra-ophiolitic mélange is subdivided into two units, the Upper Cretaceous Sorgun ophiolitic mélange and the Ladinian-Carnian Hacialani{dotless} mélange. The Mersin mélanges, together with the Antalya and Mamonia domains, are represented by a series of exotic units now found south of the main Taurus range, and are characteristic of the South-Taurides Exotic Units. These mélanges clearly show the mixed origin of the different blocks and broken formations. Some components have a Palaeotethyan origin and are characterized by Pennsylvanian and Lower to Middle Permian pelagic and slope deposits. These Palaeotethyan remnants, found exclusively in the Hacialani{dotless} mélange, were reworked as major olistostromes in the Neotethys basin during the Eo-Cimmerian orogenic event. Neotethyan elements are represented by Middle Triassic seamounts and by broken formations containing typical Neotethyan conodont faunas such as Metapolygnathus mersinensis Kozur & Moix and M. primitius s. s., both present in the latest Carnian interval, as well as the occurrence of the middle Norian Epigondolella praeslovakensis Kozur, Masset & Moix. Other elements are clearly derived from the former north Anatolian passive margin and are represented by Huǧlu-type series including the Upper Triassic syn-rift volcanic event. These sequences attributed to the Huǧlu-Pindos back-arc ocean were displaced southward during the Late Cretaceous obduction event. The Tauric elements are represented by Eo-Cimmerian flysch-like and molasse sequences intercalated in Neotethyan series. Additionally, some shallow-water blocks might be derived from the Bolkardaǧ paraautochthonous and the Taurus-Beydaglari marginal sequences. ©TÜBİTAK.

Lucas S.G.,New Mexico Museum of Natural History | Tanner L.H.,Le Moyne College | Kozur H.W.,Rezsu u. 83 | Weems R.E.,Paleo Quest | Heckert A.B.,Appalachian State University
Earth-Science Reviews | Year: 2012

The Late Triassic timescale is poorly constrained due largely to the dearth of reliable radioisotopic ages that can be related precisely to biostratigraphy combined with evident contradictions between biostratigraphic and magnetostratigraphic correlations. These problems are most apparent with regard to the age and correlation of the Carnian-Norian boundary (base of the Norian Stage). We review the available age data pertaining to the Carnian-Norian boundary and conclude that the "long Norian" in current use by many workers, which places the Carnian-Norian boundary at ~. 228. Ma, is incorrect. The evidence supports a Norian stage that is much shorter than proposed by these workers, so the Carnian-Norian boundary is considerably younger than this, close to 220. Ma in age. Critical to this conclusion is the correlation of the Carnian-Norian boundary in nonmarine strata of Europe and North America, and its integration with existing radioisotopic ages and magnetostratigraphy. Three biostratigraphic datasets (palynomorphs, conchostracans and tetrapods) reliably identify the same position for the Carnian-Norian boundary (within normal limits of biostratigraphic resolution) in nonmarine strata of the Chinle Group (American Southwest), Newark Supergroup (eastern USA-Canada) and the German Keuper. These biostratigraphic datasets place the Carnian-Norian boundary at the base of the Warford Member of the lower Passaic Formation in the Newark Basin, and, as was widely accepted prior to 2002, this correlates the base of the Norian to a horizon within Newark magnetozone E13n. In recent years a correlation based solely on magnetostratigraphy has been proposed between the Pizzo Mondello section in Sicily and the Newark section. This correlation, which ignores robust biostratigraphic data, places the Norian base much too low in the Newark Basin section (~. at the base of the Lockatong Formation), correlative to a horizon near the base of Newark magnetozone E8. Despite the fact that this correlation is falsifiable on the basis of the biostratigraphic data, it still became the primary justification for placing the Carnian-Norian boundary at ~. 228. Ma (based on Newark cyclostratigraphy). The "long Norian" created thereby is unsupported by either biostratigraphic or reliable radioisotopic data and therefore must be abandoned. While few data can be presented to support a Carnian-Norian boundary as old as 228. Ma, existing radioisotopic age data are consistent with a Norian base at ~. 220. Ma. Although this date is approximately correct, more reliable and precise radioisotopic ages still are needed to firmly assign a precise age to the Carnian-Norian boundary. © 2012 Elsevier B.V.

Conchostracan-rich beds between the Siberian Trap flood basalts and within the thick underlying Hungtukun tuffs of the Tunguska Basin can be closely correlated with conchostracan faunas of Dalongkou (NW China) and the Germanic Basin. The Germanic Basin faunas in turn can be closely correlated with the marine international stratigraphic time scale, and the accuracy of the biostratigraphic correlation of the Permian-Triassic boundary (PTB) is confirmed by a minimum in δ13Ccarb values at this level. These high-resolution correlations demonstrate conclusively that the PTB is located within the temporally brief but thick Siberian Trap flood basalt sequence. The PTB lies slightly above the level of the main Permo-Triassic extinction event in low latitude marine beds, which occurred at the base of the C. meishanensis-H. praeparvus conodont zone and correlates with the beginning of the Siberian Trap flood basalt event. The main end-Permian continental extinction event was somewhat earlier, within the middle of the C. changxingensis-C. deflecta conodont zone. This horizon marks a mass extinction that devastated a diverse conchostracan fauna and left only low diversity faunas at low and high latitudes. This continental extinction event horizon lies within the middle of the Hungtukun tuffs of the Tunguska Basin and 107m above the base of the Guodikeng Formation at Dalongkou (NW China). A "Triassic type" pioneer flora with numerous lycopod spores appears immediately above this level. Severe high northern and southern latitude marine extinctions occurred concurrently with this continental event, but low latitude marine biota was not then affected. This earlier event is best explained by global warming. The main low latitude extinction event in marine warm water faunas occurred somewhat later and left no signature in high latitude marine faunas or in continental faunas, but it does coincide with a rapid collapse of tropical rain forest environments (disappearance of the highly diverse Gigantopteris flora). This collapse likely was caused by global cooling due to a volcanic winter event. © 2011.

Lucas S.G.,New Mexico Museum of Natural History | Tanner L.H.,Le Moyne College | Donohoo-Hurley L.L.,University of New Mexico | Geissman J.W.,University of New Mexico | And 3 more authors.
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2011

Strata of the Moenave Formation on and adjacent to the southern Colorado Plateau in Utah-Arizona, U.S.A., represent one of the best known and most stratigraphically continuous, complete and fossiliferous terrestrial sections across the Triassic-Jurassic boundary. We present a synthesis of new biostratigraphic and magnetostratigraphic data collected from across the Moenave Formation outcrop belt, which extends from the St. George area in southwestern Utah to the Tuba City area in northern Arizona. These data include palynomorphs, conchostracans and vertebrate fossils (including footprints) and a composite polarity record based on four overlapping magnetostratigraphic sections. Placement of the Triassic-Jurassic boundary in strata of the Moenave Formation has long been imprecise and debatable, but these new data (especially the conchostracans) allow us to place the Triassic-Jurassic boundary relatively precisely in the middle part of the Whitmore Point Member of the Moenave Formation, stratigraphically well above the highest occurrence of crurotarsan body fossils or footprints. Correlation to marine sections based on this placement indicates that major terrestrial vertebrate extinctions preceded marine extinctions across the Triassic-Jurassic boundary and therefore were likely unrelated to the Central Atlantic Magmatic Province (CAMP) volcanism. © 2011 Elsevier B.V.

Kozur H.W.,Rezsu u. 83 | Wardlaw B.R.,U.S. Geological Survey
Micropaleontology | Year: 2010

The red, ammonoid-bearing limestones at Rustaq and Wadi Wasit contain Jinogondolella aserrata, the index species for the type Wordian. It occurs with an abundant smooth Mesogondolella fauna and an advanced Waagenoceras ammonoid fauna. In the Rustaq section, two species of Mesogondolella are present in both lower and upper red, ammonoid-bearing limestoneswith M. siciliensis dominating the lower beds and M. omanensis (new species) dominating the upper beds. The same two Mesogondolella species occur in the single, ammonoid-bearing limestone unit at the Wadi Wasit section, where there are additional conodont species including M. bitteri. The faunas at Wadi Wasit section and the upper red, ammonoid-bearing limestone at the Rustaq section contain Stepanovites? festivus which is indicative of the Wordian-Capitanian boundary interval. Capitanian Jinogondolella altudaensis appears in the rocks above the ammonoid-bearing limestone at the Wadi Wasit section.

Korte C.,Free University of Berlin | Kozur H.W.,Rezsu u. 83
Journal of Asian Earth Sciences | Year: 2010

The Palaeozoic-Mesozoic transition is marked by distinct perturbations in the global carbon cycle resulting in a prominent negative carbon-isotope excursion at the Permian-Triassic (P-T) boundary, well known from a plethora of marine and continental sediments. Potential causes for this negative δ13C trend (and their links to the latest Permian mass extinction) have been intensively debated in the literature. In order to draw conclusions regarding causation, a general δ13C curve was defined after consideration of all available datasets and with due reference to the biostratigraphic background. The most important features of the P-T carbon-isotope trend are the following: the 4-7‰ δ13C decline (lasting ∼500,000years) is gradual and began in the Changhsingian at the stratigraphic level of the C. bachmanni Zone. The decreasing trend is interrupted by a short-term positive event that starts at about the latest Permian low-latitude marine main extinction event horizon (=EH), indicating that the extinction itself cannot have caused the negative carbon-isotope excursion. After this short-term positive excursion, the δ13C decline continues to a first minimum at about the P-T boundary. A subsequent slight increase is followed by a second (occasionally two-peaked) minimum in the lower (and middle) I. isarcica Zone. The negative carbon-isotope excursion was most likely a consequence of a combination of different causes that may include: (1) direct and indirect effects of the Siberian Trap and contemporaneous volcanism and (2) anoxic deep waters occasionally reaching very shallow sea levels. A sudden release of isotopically light methane from oceanic sediment piles or permafrost soils as a source for the negative carbon-isotope trend is questionable at least for the time span a little below the EH and somewhat above the P-T boundary. © 2010 Elsevier Ltd.

Kozur H.W.,Rezsu u. 83 | Bachmann G.H.,Martin Luther University of Halle Wittenberg
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2010

The Middle Carnian Wet Intermezzo (MCWI) of the Stuttgart Formation (Schilfsandstein) and age-equivalent strata of the northwestern Tethys occurred entirely within equivalents of the upper subzone of the Austrotrachyceras austriacum ammonoid zone of the late Julian. Its duration is estimated to be only about 0.7-0.8 myr. In both the Germanic Basin and the northwestern Tethys, the warm climate during the MCWI was characterized by a rate of precipitation that exceeded somewhat the evaporation but was not so great as to be pluvial. The MCWI was related to the atmospheric circulation of a megamonsoonal system that was characterized by strong, moisture-laden, northwesterly flowing trade winds that rose as they reached the estimated 2000-3000 m high eastern shoulder uplift of a huge rift causing them to drop an extraordinary amount of rain. This eastern shoulder uplift lay within the Caledonides of modern day western Scandinavia. This region only, between 30 and 50°N palaeolatitude, had a truly pluvial climate, and the huge amounts of fresh water dropped there transported large amounts of siliciclastics from this rift-shoulder uplift southward into the Germanic Basin. Before deposition of the siliciclastics an early Julian eustatic sea-level fall caused widespread erosion in the Germanic Basin. In the later part of late Julian, a transgression from the eastern gates with the concurrent strong fresh water influx from the north flooded the centre of the northern Germanic Basin with a shallow brackish sea in which the Osterhagen Horizon (Basisschichten) of the lower Stuttgart Formation was deposited. In the upper Osterhagen Horizon the salinity rapidly decreased from mesohaline through mio- and oligohaline to fresh water levels. In southern Germany the Basisschichten formed entirely within fresh water or very low salinity brackish environments. Later, a slight subsidence of the southwestern Germanic Basin shifted the main outflow of fresh water toward the southwestern end of the basin, creating local brackish conditions in the northern marginal part of the northwestern Tethys (e.g. in the Lunz Beds). During this time interval, tidal influence also can be found in the Stuttgart Formation deposited in palaeoestuaries of the southwestern Germanic Basin adjacent to the Tethys. The very strong fresh water influx from the north, however, prevented these estuaries from developing a strongly elevated salt content, so that only fresh water to oligohaline brackish faunas are found there such as the Eberstadt bivalve-conchostracan fauna. At the base of the Tuvalian, the megamonsoonal system either disintegrated or else the trade winds shifted their principal flow direction. This caused the climate within the Germanic Basin and in the nearby northwestern Tethys Sea to become arid again as it had been before the deposition of the Stuttgart Formation. These changes in the atmospheric circulation patterns also terminated the pluvial climatic regime to the north along the Scandinavian eastern rift-shoulder uplift. This in turn ended the transport of huge amounts of siliciclastics from this region southward into the Germanic Basin and ended the deposition of the Schilfsandstein. After this, the hypersaline sabkha and playa sedimentation of the Weser Formation began, which was accompanied by some minor marine ingressions in the southwestern Germanic Basin. © 2009 Elsevier B.V. All rights reserved.

Korte C.,Free University of Berlin | Pande P.,University of Delhi | Kalia P.,University of Delhi | Kozur H.W.,Rezsu u. 83 | And 2 more authors.
Journal of Asian Earth Sciences | Year: 2010

Bulk carbonate and conodonts from three Permian-Triassic (P-T) boundary sections at Guryul Ravine (Kashmir), Abadeh (central Iran) and Pufels/Bula/Bulla (Italy) were investigated for δ13C and δ18O. Carbon isotope data highlight environmental changes across the P-T boundary and show the following features: (1) a gradual decrease of ∼4‰ to more than 7‰ starting in the Late Permian (Changhsingian) C. bachmanni Zone, with two superimposed transient positive excursions in the C. meishanensis-H. praeparvus and the M. ultima-S. ? mostleri Zones; (2) two δ13C minima, the first at the P-T boundary and a higher, occasionally double-minimum in the lower I. isarcica Zone. It is unlikely that the short-lived phenomena, such as a breakdown in biological productivity due to catastrophic mass extinction, a sudden release of oceanic methane hydrates or meteorite impact(s), could have been the main control on the latest Permian carbon isotope curve because of its prolonged (0.5 Ma) duration, gradual decrease and the existence of a >1‰ positive shift at the main extinction horizon. The P-T boundary δ13C trend matches in time and magnitude the eruption of the Siberian Traps and other contemporaneous volcanism, suggesting that volcanogenic effects, such as outgassed CO2 from volcanism and, even more, thermal metamorphism of organic-rich sediments, as the likely cause of the negative trend. © 2009 Elsevier Ltd. All rights reserved.

Carbon isotope trends are useful for stratigraphic correlation, especially for time intervals when major perturbations of the global carbon cycle occurred. Such perturbations have been documented for the Triassic-Jurassic (T-J) boundary, and several successions from this time interval are characterized by (1) an initial negative excursion, followed by (2) a pronounced positive excursion and a subsequent (3) main negative carbon isotope excursion. These features, however, are not present in all T-J boundary sections, or the stratigraphic position of the positive or the main negative excursion has variable locations. In the present study, we analysed carbon isotopes in bulk carbonate from the pelagic Cso{double acute}vár quarry section in Hungary and from the intra-platform basin to shallow subtidal marine Kendlbachgraben section in Austria. Both T-J boundary successions are biostratigraphically well controlled enabling - with particular focus on the bio- and chemostratigraphy of other T-J boundary sections - correlation of the carbon isotope trends. This evaluation shows that the apex of the initial negative δ13C excursion occurred slightly, but distinctly, below the mass extinction event and represents an excellent stratigraphic correlation tool. © 2011 by Bulletin of the Geological Society of Denmark.

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