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1

The Jurassic–Cretaceous transition in the High-Tatric succession (Giewont Unit, Western Tatra Mts, Poland): integrated stratigraphy and microfacies

Lodowski Damian Gerard, Pszczółkowski Andrzej, Wilamowski Andrzej, Grabowski Jacek

Acta Geologica Polonica

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2022

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Vol. 72, no. 1

107--135

EN

Herein are presented the results of detailed bio - (calcareous dinocysts, calpionellids, foraminifers, saccocomids) and chemostratigraphic (δ13C) studies combined with high-resolution microfacies, rock magnetic and gamma-ray spectrometry (GRS) investigations performed on the upper Kimmeridgian-upper Valanginian carbonates of the Giewont succession (Tatricum, Giewont and Mały Giewont sections, Western Tatra Mountains, Poland). The interval studied covers the contact between the Raptawicka Turnia Limestone (RTL) Fm. and the Wysoka Turnia Limestone (WTL) Fm. Their sedimentary sequence is composed of micrites, pseudonodular limestones, cyanoid packstones, lithoclastic packstone and encrinites. A precise correlation with the previously published Mały Giewont section is ensured by biostratigraphy, rock magnetic and GRS logs. The methodology adopted has enabled the recognition of two stratigraphic discontinuities, approximated here as corresponding to the latest Tithonian-early (late?) Berriasian and the early Valanginian. The hiatuses are evidenced by biostratigraphic data and the microfacies succession as well as by perturbations in isotopic compositions and rock magnetic logs; they are thought to result from a conjunction of tectonic activity and eustatic changes. A modified lithostratigraphic scheme for the Giewont and the Osobita High-Tatric successions is proposed. The top of the RTL Fm. falls in the upper Tithonian, where cyanoid packstones disappear. At the base of the WTL Fm. a new Giewont Member is defined as consisting of a basal lithoclastic packstone and following encrinites.

2

Redox conditions, glacio-eustasy, and the status of the Cenomanian-Turonian Anoxic Event: new evidence from the Upper Cretaceous Chalk of England

Jeans Christopher V., Wray David S., Williams C. Terry, Bland David J., Wood Christopher J.

Acta Geologica Polonica

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2021

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Vol. 71, no. 2

103--152

EN

The nature of the Cenomanian–Turonian Oceanic Anoxic Event (CTOAE) and its δ13 C Excursion is considered in the light of (1) the stratigraphical framework in which the CTOAE developed in the European shelf seas, (2) conclusions that can be drawn from new detailed investigations of the Chalk succession at three locations in England, at Melton Ross and Flixton in the Northern Province where organic-rich ‘black bands’ are present, and at Dover in the Southern Province (part of the Anglo-Paris Basin) where they are absent, and (3) how these conclusion fit in with the present understanding of the CTOAE. The application of the cerium anomaly method (German and Elderfield 1990) at Dover, Melton Ross and Flixton has allowed the varying palaeoredox conditions in the Chalk Sea and its sediments to be related to the acid insoluble residues, organic carbon, δ18O (calcite), δ13C (calcite), δ13C (organic matter), Fe 2+ and Mn2+ (calcite), and P/TiO2 (acid insoluble residue). This has provided evidence that the initial stages of the δ13C Excursion in England were related to (1) a drop of sea level estimated at between 45 and 85 metres, (2) influxes of terrestrial silicate and organic detritus from adjacent continental sources and the reworking of exposed marine sediments, and (3) the presence of three cold water phases (named the Wood, Jefferies and Black) associated with the appearance of the cold-water pulse fauna during the Plenus Cold Event. Conditions in the water column and in the chalk sediment were different in the two areas. In the Northern Province, cerium-enriched waters and anoxic conditions were widespread; the δ13C pattern reflects the interplay between the development of anoxia in the water column and the preservation of terrestrial and marine organic matter in the black bands; here the CTOAE was short-lived (~0.25 Ma) lasting only the length of the Upper Cenomanian Metoicoceras geslinianum Zone. In the Southern Province, water conditions were oxic and the δ13C Excursion lasted to the top of the Lower Turonian Watinoceras devonense Zone, much longer (~1.05 Ma) than in the Northern Province. These differences are discussed with respect to (1) the Cenomanian–Turonian Anoxic Event (CTAE) hypothesis when the ocean-continent-atmosphere systems were linked, (2) limitations of chemostratigraphic global correlation, and (3) the Cenomanian-Turonian Anoxic Event Recovery (CTOAER), a new term to define the varying lengths of time it took different oceans and seas to recover once the linked ocean-continent-atmosphere system was over. The possibility is considered that glacio-eustasy (the glacial control hypothesis of Jeans et al. 1991) with the waxing and waning of polar ice sheets, in association with the degassing of large igneous provinces, may have set the scene for the development of the Cenomanian-Turonian Anoxic Event (CTAE).

3

Summer–winter contrast in carbon isotope and elemental composition of total suspended particulate matter in the urban atmosphere of Krakow, Southern Poland

Zimnoch Mirosław, Morawski Filip, Kuc Tadeusz, Samek Lucyna, Bartyzel Jakub, Gorczyca Zbigniew, Skiba Alicja, Rozanski Kazimierz

Nukleonika

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2020

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Vol. 65, No. 3

181--191

EN

The city of Krakow located in southern Poland ranks among the most polluted urban agglomerations in Europe. There are persisting controversies with respect to impact of different pollution sources operating in Krakow agglomeration on air quality within the city. The presented pilot study was aimed at exploring the possibilities offered by elemental and carbon isotope composition of total suspended particulate matter (TSPM) for better characterization of its sources in Krakow atmosphere. The analyses of carbon isotope composition of total carbon in the investigated TSPM samples were supplemented by parallel analyses of radiocarbon content in atmospheric carbon dioxide (CO2). This study revealed large seasonal variability of carbon isotope composition in the analysed TSPM samples. This large variability reflects seasonally varying contribution of different sources of fossil and modern carbon to the TSPM pool. The elemental composition of TSPM also reveals distinct seasonal variability of the analysed elements, reflecting varying mixture of natural and anthropogenic sources of those elements. A linear relationship between the fossil carbon load in the TSPM samples and the fossil carbon load in the atmospheric CO2 was found, pointing to the presence of additional source of anthropogenic carbonaceous particles not associated with burning of fossil fuels. Wearing of tyres and asphalt pavement is most probably the main source of such particles.

4

Paleoklimatologia : co nam powie skład izotopowy węgla

Popkiewicz Marcin, Kardaś Aleksandra

LAB Laboratoria, Aparatura, Badania

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2020

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R. 25, nr 1

37--42

5

Carbon isotopes in wood combustion/pyrolysis products: experimental and molecular simulation approaches

Hercman Helena, Szczerba Marek, Zawidzki Paweł, Trojan Agata

Geochronometria

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2019

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Vol. 46, no. 1

111--124

EN

A series of laboratory experiments was performed to determine the carbon stable isotopic composition of different combustion/pyrolysis (B/P) products. Variation in the δ13C values of the products was observed, up to 4‰. The differences in the carbon isotopic compositions of the B/P products were dependent on temperature, time and wood type. Comparison of the results for fresh and fossil oak wood suggested that the δ13C differences were the effect of selective decomposition of some wood components during the fossilization process. The temperature dependence of the carbon isotopic composition was linked to variation in the carbon isotopic composition of the main wood components, which each had different levels of thermal stability. Isotopes exchange reactions in between different products can be also considered as possible source of variation of δ13C on temperature. Both these hypotheses were supported by molecular simulations of cellulose and lignin B/P. The results confirm that B/P should be treated as a continuous process, where the results depend on the degree of process development. Natural burning processes are dynamic and burning conditions change rapidly and it is necessary to take care when using combustion products as a paleoenvironmental proxy or as an isotopic characteristic for the identification of source material.

6

From carbonate platform to euxinic sea – the collapse of an Early/Middle Devonian reef, Cantabrian Mountains (Spain)

van Loevezijn G. B. S., Raven J. G. M.

Geologos

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2017

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Vol. 23, No. 3

143–-161

EN

The Santa Lucía Formation represents the major phase in Devonian reef development of the Cantabrian Zone (Cantabrian Mountains, northwest Spain). In the present study the transition from the carbonate platform deposits of the Santa Lucía Formation to the overlying euxinic basinal deposits of the Huergas Formation is described. These transitional strata are connected to the Basal Choteč Event and represent a condensed sedimentation of micritic dark-grey and black limestones with an upward increase of dark shale intercalations with iron mineralisation surfaces and storm-induced brachiopod coquinas. The transitional beds are grouped into a new unit, the Cabornera Bed, which consists of lime-stone, limestone-shale and shale facies associations, representing a sediment-starved euxinic offshore area just below the storm wave base. Four stages in reef decline can be recognised: a reef stage, an oxygen-depleted, nutrient-rich stage, a siliciclastic-influx stage and a pelagic-siliciclastic stage. Additional geochemical and geophysical investigations are needed to verify the results presented herein.

7

Latest Triassic climate humidification and kaolinite formation (Western Carpathians, Tatric Unit of the Tatra Mts.)

Lintnerová O., Michalik J., Uhlík P., Soták J., Weissová Z.

Geological Quarterly

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2013

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Vol. 57, No. 4

701–-728

EN

The Tomanová Formation, of Rhaetian age, overlying the Norian Carpathian Keuper in the Tatra Mts. is built of cyclic parasequences of mudstones and sandstones. Quartz (15 to 70 wt.%), kaolinite (13 to 46 wt.%) and 2:1 Al dioctahedral phyllosilicates (dioct 2:1: muscovite, illite, illite/smectite: 5 to 39 wt.%) represent the major mineral phase. The kaolinite/dioct 2:1 ratio decreases upwards in the section (from 4.3 to 0.5) and signals variability in weathering/erosion intensity and changing water salinity. Major and trace elements (LILE, HSFS, REE) indicate a uniform source – felsic rocks located probably in the Vindelician Highlands. The sedimentation rate (83 mm/ky) was controlled by climate. Alternation of dry and humid periods is refered by sedimentary textures and by maturity of quartz (aeolian vs. fluvial grains), and organic matter content and composition (Corg and d13Corg). Authigenic siderite or bethierine documents wet and reduced conditions in the upper part of the Tomanová Formation. The sedimention rate of the marine Dudzinec Formation attained 25 mm/ka and the character of cycles preserved in the sequence is similar as that of the Tomanová Formation (fining upwards parasequences). However, the different clay mineralogy, the recycled character of the silicates, the different d13Corg and elevated imput of carbonate detritus with specific C and O isotopic patterns document a discontinuity in the section. The transgressive character of the Dudzinec Fm. was deduced from the stratigraphic distribution and environmental characteristics of the benthic foraminifera present. Involutinids and spirillinids dominate in the lower part, endothyrinids govern the middle part, and in the upper part nodosariids and Ammodiscus-type microfauna occur. These age-diagnostic microfossils indicate a late Rhaetian age. Sea level rise in the Tatric Zone triggered by thermal expansion of the Central Atlantic Rift was gradual, being affected by input of terrestrial clastic sediment both by freshwater and by wind. The Tatric Triassic sequence in the Western Carpathians helps understanding of the development of sedimentation, palaeoclimate (kaolinite weathering), and palaeogeography of the northernmost Tethyan Domain.

8

Foraminifers and stable isotope record of the Dubivtsi chalk (upper Turonian, Western Ukraine): palaeoenvironmental implications

Dubicka Z., Peryt D.

Geological Quarterly

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2012

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Vol. 56, No 1

199-214

EN

A combined micropalaeontological and stable isotope study of the Dubivtsi chalk in the Western Ukraine indicates its middle late Turonian age. One long-term and clearly distinguishable positive excursion of the isotope curve (d1318

9

Foraminiferal colonization related to the Zechstein (Lopingian) transgression in the western part of the Wolsztyn Palaeo-Ridge area, Western Poland

Peryt D., Peryt T. M., Raczyński P., Chłódek K.

Geological Quarterly

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2012

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Vol. 56, No 3

529--546

EN

The basal Zechstein succession in SW Poland is dominated by breccias and/or conglomerates or extraclast-bearing bioclastic limestones, which were deposited during rapid flooding of the pre-existing intracontinental basin in the early Lopingian (Late Permian). Of these, the boulder-cobble breccias and conglomerates are interpreted as deposited in a rocky shore-zone where density flows and upwelling prevailed. The breccias gradually pass up into bryozoan (or other bioclastics) grainstones. The matrix-supported breccias were deposited as large extraclasts and blocks of Carboniferous rock were rolled down or detached from a cliff and were then either embedded into a carbonate sand or formed a framework supplying voids that could be colonized by tubular encrusting foraminifers. These foraminifers abound in all basal Zechstein facies (except in the debris-flow deposits) and are attributed to Palaeonubecularia. The associated faunas include other foraminifers (uniserial and hemigordiopsids), bryozoans, brachiopods, bivalves, gastropods, and microbial deposits. The prolific growth of tubular encrusting foraminifers has resulted from nutrient supply from the basin by upwelling. Botryoidal aragonite cements (also interpreted as due to upwelling) also characterize the basal Zechstein strata, although they were previously reported only from the upper Zechstein Limestone. The ẟI3C values of the basal Zechstein deposits show small variation and oscillated around 4.0%o, suggesting that these deposits are younger than the Kupferschiefer.

10

Zmienność składu izotopowego węgla i wodoru w eksploatowanym złożu gazu ziemnego

Pleśniak Ł., Bucha M., Jędrysek M.-O.

Bezpieczeństwo Pracy i Ochrona Środowiska w Górnictwie

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2012

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nr 12

28-34

PL

W celu zwiększenia efektywności wydobycia, w kopalniach gazu ziemnego stosuje się technologię wzmożonego pozyskania gazu (EGR), która bazuje na zatłaczaniu CO2 do złoża. Podczas takiego procesu należy spodziewać się efektów izotopowych. Badania objęły analizę składu trwałych izotopów węgla i wodoru w metanie ze złoża, w którym technologia EGR jest stosowana. Badania składu trwałych izotopów prowadzono od września 2009 r. Stwierdzona, zarówno przestrzenna, jak i czasowa zmienność tego składu pozwala stwierdzić, że cały układ jest bardzo dynamiczny. Wyraźnie da się zauważyć, że występują preferencyjne kierunki transportu metanu w złożu, co wpływa na efekty izotopowe, a front najwyższej prędkości migracji metanu jest znaczony przez najniższe stosunki składu trwałych izotopów węgla i wodoru z metanu.

EN

In order to increase recovery of gas and oil from deposits some technologies, called Enhanced Gas Recovery, with injection of C02 are used. In this process isotopic effects are expected. Therefore we have analyzed isotopic composition of carbon and hydrogen in methane in one EGR object. Carbon and hydrogen stable isotopic observations of methane from the EGR object have been carried out since September 2009. Both spatial and temporal variations in carbon and hydrogen isotopic ratios in methane show that the system is very dynamie. It has been observed clearly that there are some preferential paths of methane transportation through the deposit, what resulted in isotopic effects. Namely, the carbon and hydrogen isotopic ratios show that the front of the highest velocity of methane movement is marked by the lowest isotopic ratios.

11

Climate change at the Triassic/Jurassic boundary in the northwestern Tethyan realm, inferred from sections in the Tatra Mountains (Slovakia)

Michalik J., Biron A., Lintnerova O., Gotz A., Ruckwied K.

Acta Geologica Polonica

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2010

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Vol. 60, no. 4

535-548

EN

Sedimentological, palynological, clay mineralogical and carbon isotope studies were carried out on the Triassic/Jurassic (T/J) boundary interval in the NW Tethyan Realm. The analyses are based on two sections in the Slovakian Tatra Mountains (Western Carpathians): the Siroky Zl'ab section in the Med'odoly Valley and the Furkaska section above the Juranova Valley. Clay mineralogical analysis suggests an increasing intensity of chemical weathering in the hinterland due to increasing humidity. The palynological data do not allow the inference of a major T/J boundary mass extinction event. The observed striking increase in spores points instead to sudden climatic change, interpreted as a result of distant volcanic activity associated with the onset of rifting of Pangea. The [delta^13]C[org] excursion across the T/J boundary follows the globally documented perturbation of the carbon cycle during this period. it may be used for a more precise regional and global correlation.

12

Wykorzystanie trwałych izotopów tlenu (16O2 i 18O2) i węgla (12C i 13C) do badania katalitycznego procesu całkowitego utleniania metanu

Rotko M., Machocki A., Stasińska B.

Przemysł Chemiczny

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2009

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T. 88, nr 7

815-818

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Sedimentary development and isotope analysis of deposits at the Cretaceous/Palaeogene transition in the Paraíba Basin, NE Brazil

Neumann Virgínio Henrique, Barbosa José Antônio, Nascimento-Silva Valberlândia Maria, Sial Alcides Nobrega, Filho Mario

Geologos

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2009

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Vol. 15, No. 2

103--113

EN

New data are presented for three formations (Itamaracá, Gramame and Maria Farinha) and two boundaries (Campanian/Maastrichtian and Maastrichtian/Danian) in the Olinda Sub-basin of the Paraíba Basin. Currently accepted facies models, sequence stratigraphy characterizations, and stable-isotope data of carbon and oxygen are reviewed. The carbonate cement of the Itamaracá Formation sandstones shows carbon- and oxygen-isotope ratios consistent with a shallow-marine depositional environment: δ18O ranges from -0.8 to -2.7‰ PDB, and δ13C ranges from +1 to +2‰ PDB. Within the Itamaracá Formation, a maximum flooding surface at the Campanian/Maastrichtian transition has been identified. During the Maastrichtian, a Highstand System Tract was deposited, which shows an increase in temperature and marine bioproductivity as recorded by stable-isotope values (δ18O from -3 to -5‰ PDB, and δ13C values of -1.2, -0.3, 0.1 and +2.3‰ PDB). Just below the K/Pg boundary, the O-isotope signal indicates three warming phases, alternating with four cooling phases.

14

Delta13C of organic atmospheric dust deposited in Wrocław (SW Poland): critical remarks on the passive method

Górka M., Jędrysek M. O.

Geological Quarterly

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2008

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Vol. 52, No 2

115-115

EN

This paper reports the results of the application of passive collectors to the collection of solid organic atmospheric particles (SOAP) in Wrocław (SW Poland) to carry out stable carbon isotope analyses. delta exp.13C (SOAP) values collected during the vegetation-free period, from November to March, vary in a narrow range from -24.5 to -27.8‰. We show that d13C (SOAP) is able to provide information about atmospheric pollution with respect to different emission sources. delta exp.13C (SOAP) values collected during the period of vegetation growth, from April to October, show a wide range from -20.5 to -26.9‰. The most probable explanations for the 13C- enriched values in summer are that: (i) the SOAP have been contaminated with fresh and decomposed organic matter in the passive collector and/or (ii) SOAP are derived from out side the city or from out side Poland (C4 plant particles). There fore, the d13C (SOAP) may not represent a strictly anthropogenic im pact. The passive collector method for the (SOAP) collection should be applied only in areas with dry deposition of atmospheric dust where deposited organic matter is not de composed in the water contained in collectors. We recommend the use of active sampling methods (hi-volume sampler) to collect SOAP use ful for carbon isotope analyses.

15

Origin of siderites from the Lower Jurassic Ciechocinek Formation from SW Poland

Leonowicz P.

Geological Quarterly

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2007

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Vol. 51, No 1

67-78

EN

Sideritic rocks, which are characteristic constituents of muddy-silty deposits of the Lower Jurassic Ciechocinek Formation, occur commonly as layers, lenses and small irregular concretions composed of siderite mudstone and siltstone as well as less common lenses of sideritic sandstones. Three types of siderite cement were observed in thin sections: fine-crystalline variety (SF), coarse-crystalline rhombohedra (SR) and fine-crystalline biogenic aggre gates (SA). In all these types BSE analysis revealed compositional zonation of crystals, with in ternal parts enriched in Mg, Mn and Ca and outer zones almost pure siderite. d13C values and chemical composition of siderites combined with the presence of early diagenetic pyrite indicate that siderite crystallized from brackish marine-derived solutions; only in the case of two samples from the lower part of the Ciechocinek Formation the fresh water origin cannotbe excluded. Mn and Fe were supplied by rivers and released by Fe- and Mn-reduction in suboxic zone, whereas Mg and Ca were derived from sea water, which infiltrated into the sediment. Crystal zonation resulted from the diagenetic evolution of pore water as the sediment was buried. Similar composition and development of siderite crystals from different parts of one layer indicate that siderite precipitated simultaneously throughout the whole horizon. Precipitation began from the formation of numerous nuclei and continued by growth of crystals onto them. It could begin already in the iron reduction subzone and continued in the sulphate reduction and methanogenesis zones.

16

An integrated study (inoceramid bivalves, ammonites, calcareous nannofossils, planktonic foraminifera, stable carbon isotopes) of the Ten Mile Creek section, Lancaster, Dallas County, north Texas, a candidate Global boundary Stratotype Section and Point

Gale A.

Acta Geologica Polonica

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2007

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Vol. 57, no. 2

113-160

EN

The WalMart section on Ten Mile Creek, Lancaster, Dallas County, Texas, exposes a 23 metre section of Austin Chalk that can be integrated into a more than 60 m composite sequence for the Dallas area on the basis of bed-by-bed correlation. The section was proposed as a possible candidat e Global Boundary Stratotype at the 1995 Brussels meeting on Cretaceous Stage boundaries, with the first occurrence of the inoceramid bivalve Cladoceramus undulatoplicatus (ROEMER, 1852) as the potential boundary marker. An integrated study of the inoceramid bivalves, ammonites, planktonic foraminifera, and calcareous nannofossils places the first occurrence of Cl. undulatoplicatus in a matrix of ten ancillary biostratigraphic markers. The candidate Global boundary Stratotype Section and Point (GSSP) is located within a composite stable carbon isotope curve for the Austin Chalk as a whole. This shows it to lie 3.5 m below the Michel Dean stable carbon isotope event, originally recognised in the English Chalk. The first occurrence of Cl. undulatoplicatus lies in the same position in relation to stable carbon isotope events in both Texas and England that can in principle be recognised globally in marine sediments. The WalMart section satisfies many of the criteria required of a GSSP for the base of the Santonian Stage, although ownership and access require clarification.

17

The Middle Oxfordian Platysphinctes event-horizon – an integrated tool in the correlations around the boundary of the Plicatilis and Transversarium zones in Europe

Glowniak E., Wierzbowski H.

Volumina Jurassica

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2006

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Vol. 4, no. 1

162-163

EN

Palaeobiogeographic differentiation of the Late Jurassic faunas of the northern hemisphere was connected with temporal excursions and mixing of the Boreal-Subboreal and Mediterranean ammonites in the area of the Submediterranean epicratonic seas of the northern Tethyan shelf. These excursions are well recognized from the Late Oxfordian onwards (e.g. Atrops et al. 1993) but are less well-known in the Middle Oxfordian. However, the lower Mid-Oxfordian Platysphinctes event-horizon first recognized in central Poland (GĐowniak 2000), has been recently evidenced also in southern Poland and NW Germany. According to the new study (GĐowniak 2006b, in press) it appears in central Europe within the Arkelli Horizon of the Arkelli Subzone (Mid-Oxfordian Plicatilis Zone in the usage of the Submediterranean zonal scheme based on perisphinctid lineage, GĐowniak 2002, 2006a) and was a proxy for a biogeographical phenomenon referred to as the “Mediterranean Spread”. At that time, geographical barriers did not hinder communication between the Submediterranean and Tethys basins, which may point to the occurrence of the “Mediterranean Spread” in conditions of a sea-level rise. In accordance with the previous opinion remain geochemical isotope data based on stratigraphically well-dated belemnite rostra derived from the Mid-Oxfordian sections of central Poland (Wierzbowski 2002). A gradual positive shift in ä13C values, which starts at the Lower/Middle Oxfordian boundary, reaches its maximum in the Platysphinctes event-horizon. According to Wierzbowski (2002) the early Middle Oxfordian carbon isotope excursion may have been linked to transgression, which occurred during a longer period of the crisis in oceanic carbonate sedimentation. The early Middle Oxfordian positive carbon isotope shift was subsequently recognized in the sections of Scotland (Wierzbowski 2004, Pearce et al. 2005). The geochemical events from Poland and Scotland are simultaneous and should be correlated with the Platysphinctes event-horizon (cf. Wierzbowski 2002, 2004). As a consequence, the latter becomes a precise marker for the stratigraphic correlations of the Mid-Oxfordian zonal schemes in the upper Plicatilis Zone between the Submediterranean and Boreal-Subboreal Europe.

18

Prospects for correlation of the Triassic/Jurassic boundary between marine and non-marine facies using carbon-isotope stratigraphy: a case study from Xinjiang, northwest China

Hesselbo S., Deng S., Lu Y.

Volumina Jurassica

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2006

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Vol. 4, no. 1

286-287

EN

An apparently global pattern of carbon-isotope change in carbonates and organic matter across the T/J boundary has increasingly been recognized from marine sections, and may be useful as a basis for correlation. Evidence from other geological events indicates that this isotopic pattern should also have the power to resolve correlations between marine and non-marine sections where organic matter is preserved. In the present study we apply this method to the non-marine succession in the Junggar Basin, Xinjiang, northwest China. The Haojiagou Section there includes an excellent ˜700 m thick exposure of the Haojiagou Formation and lower member of the Badaowan Formation, from which fossils indicative of the T/J boundary have been described. However, different horizons have been suggested on the basis of different fossil groups. The T/J boundary has previously been placed at the lowest level in the section (at the base of Bed 25, Haojiagou Formation) on the basis of megaspores, and Bed 40, higher in the Haojiagou Formation, has been suggested to be Early Jurassic in age based on the occurrence of conchostracan taxa and the bivalve Ferganochonca. In contrast, on the basis of palynology, the T/J boundary has been placed higher in the section, at the base of Bed 45 (also the base of the Badaowan Formation), where there is an absence of pre-Jurassic index fossils such as Taeniaesporites, and occurrences of the post-Triassic index fossils, such as Cyathidites. Macrofossil plants suggests that the boundary lies between Beds 37 and 51 based on Hausmannia sp. in Bed 37, and Todites princeps and Clathopteris elegans in Bed 51 and higher. Carbon-isotope data have been obtained from both bulk sedimentary organic matter and from fossil wood fragments that were individually selected. Delta 13CWood carbon isotope values show a systematic stratigraphic trend from -21 per mil in Bed 25, to -26 per mil in Bed 52, although some samples around bed 25 also show very light isotopic values. Bulk organic isotope data show a similar overall trend, but show considerably less variance. Although the data are noisy, they suggest that the "main" negative isotope excursion of marine sections corresponds to the formational boundary and the "T/J boundary" recognized on the basis of plant macrofossils and microfossils, whilst the "initial" isotope excursion of marine sections may be expressed in wood values around beds 23-25. Depending on GSSP decisions either of these horizons may be regarded as the T/J boundary.

19

Oyster and brachiopod stable isotopes across the Triassic/Jurassic boundary and in the Early Jurassic

Korte C., Hesselbo S., Jenkyns H., Dietl G., Dulai A., Vörös A.

Volumina Jurassica

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2006

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Vol. 4, no. 1

289-289

EN

Oxygen and carbon isotope values have been obtained from oysters for the Triassic/Jurassic boundary section at Lavernock Point (Wales), and from brachiopods and oysters for different Hettangian, Sinemurian and Pliensbachian localities of South Germany and Hungary. Low-Mg-calcite brachiopods and oysters are particularly suitable for such studies because this carbonate phase is the most resistant to diagenetic alteration. Nevertheless, all fossils have been screened by chemical and optical techniques (optical microscope, scanning electron microscopy, trace element analyses) to evaluate the isotope data for diagenetic change, and only samples with Mn content less than 250 ppm and Sr content more than 400 ppm, complemented by well preserved textures under SEM, were considered in this study. For the Triassic/Jurassic boundary (TJB) the carbon isotope values are at about 2.5‰ in the lower Langport Member, increase to 4.5‰ in the lowest Blue Lias and decrease subsequently to 1.5‰ just below the Planorbis Zone. The data remain low with variations between 1.5 and 2.5‰ up to the Liassicus Zone. These results correspond to the organic carbon isotope trend for the Triassic/Jurassic boundary section at St Audrie's Bay (Hesselbo et al. 2002). Oxygen isotope values increase from -0.5‰ in lower Langport Member to 0‰ at the base of the Blue Lias, decrease in the Blue Lias down to -1.5‰ just below the Planorbis Zone and change in parallel with the organic and inorganic carbon-isotope trends. The δ ¹ ⁸O values indicate decreasing seawater temperature with increasing δ ¹ ³C in the Langport Member and increasing water temperatures of about 6°C in the lower Blue Lias. The distinct warming trend occurred during the "main" TJB negative excursion. Carbon and oxygen isotope values from Hettangian, Sinemurian and Pliensbachian brachiopods and oysters, as well as from some complementary belemnites, show similar values and trends compared to the data compilation by Jenkyns et al. (2002). Carbon isotope values are between 1 and 2‰ in the Hettangian and Early Sinemurian followed by an increase of about 1‰ during the Sinemurian, a nearly 3‰ decrease in the Early Pliensbachian and higher δ ¹ ³C values (˜2.5‰) in the later Pliensbachian.

20

Hettangian ammonite succession and analysis of the Triassic/Jurassic boundary sequence at Black Bear Ridge, Williston Lake, British Columbia

Hall R., Pitaru S., Henderson C.

Volumina Jurassica

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2006

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Vol. 4, no. 1

285-286

EN

The basal Fernie Formation at Black Bear Ridge consists of 22 m of concretionary, brown weathering siltstones containing abundant ammonites which prove the presence of lower, middle, and upper Hettangian strata. Based on over 300 specimens we have recognized 13 ammonite horizons which may be grouped into six local zones. Lower Hettangian faunas are dominated by strongly ribbed psiloceratids associated, in the upper part of their range, with small Kammerkarites; no smooth psiloceratids of the tilmannipacificum-planorbis group have been found. The Middle Hettangian is marked by the appearance of Kammerkarites hircinum associated with Kammerkarites spp., Discamphiceras, and Pleuroacanthites mulleri. Upper parts of the Middle Hettangian yield Sunrisites sunrisense, Saxoceras portlocki, Kammerkarites spp., Discamphiceras and Alsatites. First appearance of schlotheimiids, which marks the base of Upper Hettangian strata, is above the last occurrences of Sunrisites sunrisense. Faunas in higher strata are dominated by Laqueoceras nigroursus, which ranges up into beds containing Badouxia oregonensis; near the top of the section, Pseudaetomoceras doetzkirchneri appears. Lower Hettangian psiloceratid faunas from Black Bear Ridge can best be correlated with European zonations. Elsewhere, first occurrences of Kammerkarites usually mark the base of the Middle Hettangian, and they are not usually associated with psiloceratids as at Black Bear Ridge. However, strata with Kammerkarites in both Alaska and Queen Charlotte Islands have been placed in the Lower Hettangian. Sunrisites here is associated with both Saxoceras portlocki and Alsatites subliasicus, indicating its Middle Hettangian age, while in both Nevada and South America it occurs above intervals with Kammerkarites and Saxoceras, and is associated with Schlotheimia. At Black Bear Ridge the latter genus only appears above the last Sunrisites. In both Nevada and South America, Laqueoceras is also associated with Sunrisites, not succeeding it as here. Occurrences of Badouxia and Pseudaetomoceras clearly indicate correlation of the highest parts of the sequence with the Upper Hettangian. Correlation of the ammonite associations recorded at Black Bear Ridge with a regional zonation scheme proposed for North America is only partially successful due to differing local ranges of key taxa, and the absence of some genera (Euphyllites, Mullerites, Franziceras, Fergusonites, and Eolytoceras) in this section. Between the "Monotis beds", dense coquinas comprising the uppermost Pardonet Formation (Norian), and the first Jurassic ammonites in the base of the Fernie Formation, is a sparsely fossiliferous interval of flaggy-bedded, brown siltstones 2.3 m thick. Fragmented pectiniform and ramiform conodont elements of Norigondolella sp. and Epigondolella sp., obtained by us from two beds 1.5 and 1.7 m above the "Monotis beds", indicate a probable Rhaetian age for part of this interval. Positive carbon- and nitrogen-isotope excursions at the top of the "Monotis beds" have been correlated with the Norian/Rhaetian boundary (Sephton et al. 2002); they interpreted the Rhaetian/Hettangian (Triassic/Jurassic) boundary to occur 9.0 m higher in the section, though the anticipated negative carbon-isotope excursion was not found at this level. Our new ammonite data confirm that strata just 2.3 m above the top of the "Monotis beds" are already of Hettangian age.