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 for the base of the Santonian Stage
GALE A.S. 1, KENNEDY W.J. 2, LEES J.A.3, PETRIZZO M.R.4, WALASZCZYK I.5
1School of Earth and Environmental Sciences, University of Portsmouth, Burnaby Building, Burnaby Road, Portsmouth PO1 3QL, UK
2Oxford University Museum of Natural History, Parks Road, Oxford OX1 3PW, UK
3Department of Earth Sciences, University College London, Gower Street, London WC1E 6BT, UK
4Dipartimento di Scienze della Terra "Ardito Desio", Universita degli Studi di Milano, Via Mangiagalli 34, 20133 Milano, Italy
5Institute of Geology, University of Warsaw, Al. Zwirki i Wigury 93, PL–02–089 Warsaw, Poland
ABSTRACT: 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 candidate 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.
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A rare comatulid crinoid, Semiometra petitclerci (CAILLET, 1923), from the Upper Oxfordian of Poland
RADWANSKA U.
Institute of Geology, University of Warsaw, Al. Zwirki i Wigury 93; PL-02-089 Warszawa, Poland.
u.radwanska@ uw.edu.pl
ABSTRACT: A small faunule of feather stars or comatulids (free-living crinoids of the order Comatulida A.H. CLARK,
1908) is recorded from Upper Oxfordian strata (Bielawy/Wapienno sequence) in the Couiavia region,
north-western Central Poland. It represents a single, very small-sized species, Semiometra petitclerci
(CAILLET, 1923), hitherto an extreme rarity in the Jurassic sequences of France and Germany. The present
record extends the geographic distribution of the species in Europe, to evidence a wider range of
the genus Semiometra GISLEN, 1924, prior to its fairly common occurrence and higher diversity during
the Late Cretaceous.
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The highest records of North American scaphitid ammonites in the European Maastrichtian (Upper Cretaceous) and their stratigraphic implications
MACHALSKI M.1, JAGT J. W. M. 2, LANDMAN NEIL H.3, MOTCHUROVA-DEKOVA N.4
1Institute of Paleobiology, Polish Academy of Sciences, ul. Twarda 51/55, PL 00-818 Warszawa, Poland.
mach@twarda.pan.pl
2Natuurhistorisch Museum Maastricht, de Bosquetplein 6-7, NL-6211 KJ Maastricht, The Netherlands.
john.jagt@maastricht.nl
3Division of Paleontology (Invertebrates), American Museum of Natural History, 79th Street at Central Park West, New York, NY 10024, USA.
landman@amnh.org
4National Museum of Natural History, 1, Tsar Osvoboditel Bvd, Sofia 1000, Bulgaria
neda@nmnh.bas.bg
ABSTRACT: The uppermost lower to upper Maastrichtian records of North American scaphitid ammonites in Europe
are discussed in terms of taxonomy and significance for transatlantic correlation. A previous record of a
U.S. Western Interior scaphitid ammonite, Jeletzkytes dorfi, from the lower part of the upper Maastrichtian
in northeast Belgium, is demonstrated to have been based on specimens which reveal features typical of the
indigenous European Hoploscaphites constrictus lineage. However, one of the individuals in this collection
combines distinct mid-ventral swellings, characteristic of the H. constrictus stock, with irregular flank ornament,
typical of J. dorfi. It is speculated that this specimen may be a product of interspecies hybridization.
Hoploscaphites sp., allied to H. nicolletii or to H. comprimus, previously known only from the U.S. Western
Interior, is recorded from the lower upper Maastrichtian of Austria, and Discoscaphites gulosus, hitherto
regarded to be confined to the U.S. Western Interior, Gulf Coast, and Atlantic Seaboard, has been recognised
in the upper Maastrichtian of Bulgaria. Additionally, poorly preserved material referred to as
Discoscaphites? sp. is recorded from the uppermost lower Maastrichtian of Denmark, and from the upper
Maastrichtian of southern Sweden. These records of scaphitids support earlier conclusions that the base of
the European upper Maastrichtian roughly corresponds to the base of the Hoploscaphites birkelundae Zone
in the U.S. Western Interior.
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Flowstone-like calcite in the andesite of Jarmuta Mt. - dating the Holocene tectonic activity in the vicinity of Szczawnica (Magura Nappe, Outer Carpathians, Poland)
JUREWICZ E.1, HERCMAN H2, NEJBERT K.3
1Institute of Paleobiology, Polish Academy of Sciences, ul. Twarda 51/55, PL 00-818 Warszawa, Poland.
mach@twarda.pan.pl
2Natuurhistorisch Museum Maastricht, de Bosquetplein 6-7, NL-6211 KJ Maastricht, The Netherlands.
john.jagt@maastricht.nl
33Division of Paleontology (Invertebrates), American Museum of Natural History, 79th Street at Central Park West, New York, NY 10024, USA.
landman@amnh.org
ABSTRACT: Extensional fractures partly filled with calcite showing the characteristics of flowstone have been
observed in the andesite from Jarmuta Mt. The isotopic composition of this calcite indicates low-temperature
crystallization conditions and its vadose origin. U-Th dating of the flowstone-like calcite indicates
ages of ~2.5-6.5 ka. The calcite grew on a rough and fresh andesite surface, and hence its age may
correspond to the age of the extensional fractures. Rhythmically distributed intergrowths of clay minerals
present in the calcite may reflect annual climatic oscillations and show that the calcite grew for at
least 500 years. The calcite filling the extensional fractures, like the calcite cementing the loosened cataclastic
zones cutting the andesite, does not show any features indicating younger deformations. The
origin and geometric features of the fractures show that they could have formed in response to increased
strike-slip activity within the deep fault zone known as the Dunajec Fault, which may coincide with the
fracture zone between the Upper Silesian and Malopolska blocks.
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Selected benthic faunas from the Devonian of the Ardennes: an estimation of palaeobiodiversity
HUBERT B. L.M. 1,2, ZAPALSKI M. K.1,3, NICOLLIN J.-P. 1, MISTIAEN B.1, BRICE D.1
1Laboratoire de Paléontologie stratigraphique FLST & ISA, UMR 8014 CNRS, 41, rue du Port, 59046 Lille cedex, France.
2Unite de Recherche de Petrologie sedimentaire, B20, Universite de Liege, Sart-Tilman B-4000 Liege, Belgium.
benhubert@free.fr
3Laboratory of Palaeontology, Warsaw University, Faculty of Geology, Zwirki i Wigury 93, PL-02-089 Warszawa, Poland.
m.zapalski@uw.edu.pl
ABSTRACT: A survey of the principal benthic faunas from the Devonian of the Ardennes is presented. The α-diversity
is very high (707 species, including 138 species of stromatoporoids, 113 species of tabulates, hydroids
and chaetetids, and 456 species of brachiopods). Analysis of their distribution through time indicates
two brachiopod diversity peaks (Emsian/Eifelian and Frasnian), a single stromatoporoid diversity peak
(Givetian), and no clear peak of tabulate corals (with the highest diversification during the
Eifelian–Frasnian). The highest diversity of bioconstructors in the Givetian correlates with a decrease
in brachiopod diversity. Changes in the vertical distribution of the faunas are correlated with the facies
development: the development of carbonates correlates with the abundance of stromatoporoids and
tabulates, while brachiopods were most abundant before and after the peak of carbonate development.
Bioconstructors are absent (or nearly absent) in siliciclastic facies.
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