Devonian chitinozoan biozones of Western Gondwana
GRAHN Y.
UERJ, Faculdade de Geologia, Bloco A – Sala 4001, Rua Sao Francisco Xavier 524, 20550-013 Rio de Janeiro, R.J., Brazil.
yngvegrahn@hotmail.com
ABSTRACT: A formal Devonian chitinozoan biozonation for western Gondwana is proposed. This palaeogeographic
province corresponds to South America, and was located in medium to high latitudes during the Devonian. Devonian chitinozoans are known
from northern Argentina, Bolivia, Brazil and eastern Paraguay. Altogether 230 localities (including wells and outcrops) are included in this
study, and 171 species have been encountered. One new species, Angochitina praedensibaculata, is described. A biozonation based on
the first occurrence of critical chitinozoan species is introduced. Thirteen biozones are defined: the Angochitina praedensibaculata,
Angochitina strigosa, Urochitina loboi, Ramochitina magnifica, Ancyrochitina pachycerata,
Ancyrochitina parisi, Alpenachitina eisenacki, Ramochitina stiphrospinata, Fungochitina microspinosa –
Ancyrochitina taouratinensis, Hoegisphaera glabra, Urochitina bastosi – Sommerochitina langei,
Fungochitina fenestrata and Fungochitina ultima zones. These biozones are compared with known spore zones from the
same area, and chitinozoan biozones on a global basis.
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On the palaeomagnetic age of the Zalas laccolith (southern Poland)
NAWROCKI J.1, POLECHONSKA1, LEWANDOWSKA A.2, WERNER T.3
1Paleomagnetic Laboratory, Polish Geological Institute, Rakowiecka 4, PL-00-975 Warszawa, Poland.
jerzy.nawrocki@pgi.gov.pl
olga.polechonska@pgi.gov.pl
2Institute of Geological Sicences, Jagiellonian University, Oleandry 2a, PL-30-063 Kraków, Poland.
ania@ing.uj.edu.pl
3Institute of Geophysics, Polish Academy of Sciences, Ks. Janusza 64, PL-01-452 Warszawa, Poland.
twerner@igf.edu.pl
ABSTRACT: An age estimation for the Zalas laccolith (Kraków area, South Poland) using the palaeomagnetic method is presented. 29 hand samples were taken from the rhyodacites and neighbouring Visean sediments cropping out in three localities. Two components of magnetization were isolated in the volcanic rocks and Visean sediments. The “A” component, common to the greenish rhyodacites and Visean sediments from Orlej, is carried by magnetite and is regarded as primary. Comparison of the mean inclination of this component with the expected (reference) stable European inclinations leads to the conclusion that the Zalas laccolith was emplaced about 280 Ma ago. The second component, “B”, characteristic of the reddish rhyodacites, is carried by hematite and was recorded during the Late Permian (c. 260 Ma) metasomatic alterations of these rocks. The palaeomagnetic poles calculated for the “A” component show a distinct departure from the Permian segment of the Baltic apparent polar wander path (APWP) due to anticlockwise block rotations of the rocks studied that were most probably connected with the Early Permian sinistral transtensional tectonic regime in Central Europe.
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Provenance analyses of the Late Cretaceous – Palaeocene deposits of the Magura Basin (Polish Western Carpathians) – evidence from a study of the heavy minerals
OSZCZYPKO N., SALATA D.
Jagiellonian University, Institute of Geological Sciences, Oleandry 2a, PL-30-063 Krakow, Poland.
nestor@ing.uj.edu.pl
salata@ing.uj.edu.pl
ABSTRACT: The Late Cretaceous-Palaeocene sequence of the Magura Nappe in Poland is underlain by the Albian-Cenomanian spotty marls at the base and overlapped by the Palaeocene/Early Eocene variegated shales at the top. The spotty marls are followed by variegated shales and then by turbiditic deposits. The upper boundary of the variegated shales is diachronous – older in the Racˇa zone (Santonian) and younger in the Krynica zone (Campanian/Maastrichtian). The turbiditic deposits of the marginal (northern) zone of the Magura Nappe display palaeocurrent directions from the NW in the western part and from the NE in the eastern part. In other parts of this unit palaeocurrent directions from the SE and E were observed. The northern source area of the Magura Basin is commonly connected with the Silesian Ridge, while the south-eastern one could be connected with an accreted fragment of the Inner Carpathians. The heavy mineral assemblages of the Magura Nappe are dominated by stable and ultrastable species. Chromian spinels occur additionally in the Krynica zone and to some extent in the Bystrica and Racˇa zones. Investigation of the chemical composition of the heavy minerals showed that that the southern source area was built of low- to medium-grade metamorphic rocks, as well as igneous rocks associated with ophiolite sequences. The chemical composition of minerals deriving from the NW indicates that they crystallized mainly in low- to high-grade metamorphic rocks and granitoids.
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Lower Kimmeridgian comatulid crinoids of the Holy Cross Mountains, Central 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: An assemblage of feather stars or comatulids (free-living crinoids of the order Comatulida A.H. CLARK, 1908) is reported for the first time from Upper Jurassic sequences of Poland, precisely from Lower Kimmeridgian strata of the Holy Cross Mountains. The major part of this assemblage comes from oolitic deposits exposed at Malogoszcz Quarry, others from oyster (Actinostreon, and Nanogyra) shellbeds higher up section at Malogoszcz, as well as from the coeval strata of the Karsy section. Taxonomically recognizable skeleton elements such as calyces, isolated centrodorsals and radials are here assigned to seven taxa, three of which are new to science: Comatulina malogostiana sp.nov., Palaeocomaster karsensis sp.nov., and Solanocrinites sanctacrucensis sp.nov. The majority of the material available was contained in burrows made by some ancestral stock of alpheid shrimp, closely comparable to those of present-day snapping shrimp (genus Alpheus WEBER, 1795), and its allies. These burrows, situated at the tops of oolitic shoals/banks at Ma∏ogoszcz, casually served both as habitats of cryptic faunas (mostly comatulids, dwarf-sized gastropods) and as preservational/taphonomic traps for others, primarily echinoderms (ten taxa of echinoids, three stalked crinoids, two ophiuroids, one asteroid) swept into by highly agitated waters, most likely during storms, to produce an Echinodermenlagerstätte. Comatulid remains from the oyster shellbeds underwent longer periods of transport, to be entombed far from their habitats.
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Late Triassic charophytes around the bone-bearing bed at Krasiejów (SW Poland) – palaeoecological and environmental remarks
ZATON M.1, PIECHOTA A.1, SIENKIEWICZ E.2
1Faculty of Earth Sciences, Bedzinska Str. 60, PL-41-200 Sosnowiec, Poland.
mzaton@wnoz.us.edu.pl
apiechot@wnoz.us.edu.pl
2Institute of Geological Sciences, Polish Academy of Sciences, Twarda 51/55 Street, 00-818 Warszawa, Poland.
esienkie@twarda.pan.pl
ABSTRACT: Thousands of Late Carnian (Late Triassic) charophyte gyrogonites belonging to four species [Stellatochara germanica KOZUR & REINHARDT, Stomochara starozhilovae (KISIELEVSKY), Stenochara kisielevskyi BILAN and Porochara triassica (SAIDAKOVSKY)] occur in the beds around the vertebrate-bearing level at Krasiejów, SW Poland. The abundant and wellpreserved gyrogonites generally attest to fossilization in situ. Information about the habitat of recent charophytes is useful for reconstruction of their past environments. The factors limiting the habitat of modern charophytes suggests that these algae, and other micro- and macrofauna sedimented within the bone-bearing bed, lived in a shallow, freshwater environment (probably lacustrine). Above the bone bed, there is a rapid drop in gyrogonite abundance. This could have been caused by changes in environmental conditions: increase in salinity, or increase in water energy. The preliminary mineralogical data suggest arid to semi-arid climate.
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Geodynamic evolution of the Tatra Mts. and the Pieniny Klippen Belt (Western Carpathians): problems and comments
JUREWICZ E.
Institute of Geology, Warsaw University, Al. Zwirki i Wigury 93, PL-02-089 Warszawa, Poland.
edyta.jurewicz@uw.edu.pl
ABSTRACT: The geodynamic evolution of the Pieniny Klippen Belt (PKB) and the Tatra Mts. assumes that: The Oravic-Vahic Basin developed due to Jurassic rifting processes with thinned continental crust. The oblique rift without rift-related volcanism had probably a WSW-ENE course. Late Cretaceous thrust-folding of the Chocˇ, Krízˇna and High-Tatric nappes took place underwater and at considerable overburden pressure (~6-7 km). The geometry of the structures was strongly disturbed by pressure solution processes leading to considerable mass loss. Nappe-folding in the PKB was connected with the slow and flat subduction of thinned continental crust of the Vahicum-Oravicum under the northern margin of the Central Carpathians Block. In the terminal phase, the northernmost units of the PKB were transported through gravitational sliding, forming numerous olistolites. In the Tatra Mts. and the PKB, the nappe thrust-folding was influenced by a strike-slip shear zone between the edge of the Central Carpathians and the PKB and caused e.g. the counter-clockwise rotation of the Tatra block and relative changing directions of thrusting. The consequence of Miocene oblique subduction and subsequent collision of the North-European continental crust with the Central Carpathian Block was the activation of NNW-SSE deep fault zones. With one of these – the Dunajec Fault – were connected en echelon shears trading on the andesite dykes swarm. Miocene collision caused the disintegration of the Central Carpathian Block into individual massifs and their rotational uplift. The value of rotation around the horizontal axis for the Tatra Massif is estimated at ~40o.
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