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Number of results: 12
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Abstract

The Jurassic period is symbolized by large reptiles that dominated the land and seas. The most recent paleontological findings indicate that the territory of Poland was inhabited by several groups of large marine animals.
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Abstract

Mount Flora at Hope Bay, in northernmost part of Antarctic Peninsula, is a famous Jurassic flora locality. It has already been studied for a hundred years, but however, it is still possible to find there new taxa. Based on two species of liverworts found at Mount Flora (Schizolepidella gracilis and Schizolepidella birkenmajeri sp. nov.), the present study discusses affiliation of the genus Schizolepidella to liverworts. The new species Schizolepidella birkenmajeri is erected.
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Abstract

A small collection of discinids from Spitsbergen includes two poorly preserved fragments of ventral valves with an incomplete pedicle disc bearing a narrowly trigonal pedicle tract. This element is similar to the type known in Recent discinids. Its general size, comparatively large, is suggestive of a wide embayment of the larval ventral valve. A new species Discinisca spitsbergensis sp. n. is proposed.
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Abstract

This is a second paper dealing with juvenile and little known Mesozoic gastropods from Siberia and the Timan region. This part contains description of gastropods belonging to Neogastropoda and Heterobranchia. Described are 16 species, five of them are new. They are: Sulcoactaeon uralicus, S. timanicus, S. bojarkensis (Bullinidae), Vasjugania vasjuganensis (Acteonidae), and Biplica siberica (Ringiculidae). The new genus Vasjugania (Acteonidae) is proposed. Eight species are left in the open nomenclature. The protoconch of Siberian Khetella, illustrated here for the first time, suggests that this genus belongs to Purpurinidae and the whole family is a possible stem group for the Neogastropoda. Apart from Khetella the Siberian fauna seems to be of cosmopolitan character having common elements both with Europe and North America.
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Abstract

The well−known Jurassic macrofloras from Hope Bay at the northernmost tip of the Antarctic Peninsula continue to yield new taxa . This paper reports on a new type of plant re− productive organ. The affinity of this organ r emains unclear; it may be affiliated with the Schizaceae or Osmundaceae, but similarities to po llen organs of the Podocarpaceae are also discussed. Because the fossils differ from hitherto known Mesozoic fertile fronds and conifer pollen organs in some details, the new taxon, Spesia antarctica nov. gen. et sp. is proposed.
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Abstract

The shallow-marine carbonate deposits of the Reuchenette Formation (Kimmeridgian, Upper Jurassic) in northwestern Switzerland and adjacent France yield highly diverse bivalve associations, but only rarely contain remains of pinnid bivalves. The three occurring taxa Pinna (Cyrtopinna) socialis d’Orbigny, 1850, Stegoconcha granulata (J. Sowerby, 1822) and Stegoconcha obliquata (Deshayes, 1839) have been revised. A lectotype for Pinna (C.) socialis was designated and the taxon is assigned herein to P. (Cyrtopinna) Mörch, 1853, the first record of the subgenus from the Jurassic. A brief review of Stegoconcha Böhm, 1907 revealed two species groups within the genus. Species close to the type species S. granulata are characterized by a nearly smooth anterior shell, followed posteriorly by deep radial furrows and rows of pustules covering the dorsal flank. Another group comprises radially ribbed species related to S. neptuni (Goldfuss, 1837). It includes among others the Paleogene species S. faxensis (Ravn, 1902), extending the known range of Stegoconcha from the Middle Jurassic into the Paleogene. The paper suggests a relationship between Stegoconcha and the Cretaceous Plesiopinna Amano, 1956, with S. obliquata as a possible intermediate species leading to Plesiopinna during the Early Cretaceous. Furthermore, a possible relationship between Stegoconcha and Atrina Gray, 1842 is discussed.
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Abstract

The Lower Jurassic to Aalenian carbonate-clastic Dudziniec Formation exposed in the autochthonous unit of the Tatra Mountains (Kościeliska Valley) hosts neptunian dykes filled with various deposits. The development of the fissures took place in multiple stages, with the same fractures opening several times, as is indicated by their architecture, occurrence of internal breccias and arrangement of the infilling sediments. Various types of internal deposits were derived in a different manner and from different sources. Fine carbonate sediments, represented by variously coloured pelitic limestones, calcilutites and fine calcarenites, most probably come from uplifted and corroded carbonate massifs (possibly from the allochthonous units of the High-Tatric succession). Products of weathering, both in dissolved form and as small particles, were washed into the sedimentary basin of the autochthonous unit, and redeposited within the dykes. The sandy varieties of the infillings, represented by red, ferruginous calcareous sandstones, come directly from the host rocks or from loose sediments present on the sea bottom at the time of fracturing. The most probable age of the infilling sediments is Sinemurian to Pliensbachian. The occurrence of dykes of this age is yet another feature confirming that the sedimentary development of the Lower Jurassic sandy-carbonate facies in the autochthonous unit was strongly influenced by synsedimentary tectonic activity, such as block-faulting.
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Abstract

The radiolarian biostratigraphy of the Middle–Upper Jurassic pelagic siliceous sediments (Czajakowa Radiolarite Formation) in the Niedzica succession of the Pieniny Klippen Belt (Carpathians) is interpreted in terms of their age in a stratotype section, and facies equivalents in other tectonic-facies units of this region. The siliceous sediments are represented by radiolarian cherts and silicified limestones which are underlain and overlain by red nodular limestones, equivalents of the Rosso Ammonitico facies. The radiolarian association includes thirty-seven taxa belonging to twenty one genera which represent the Northern Tethyan Palaeogeographic Province. Key radiolarians recorded provide a means of correlation with zonation schemes based on Unitary Associations defined for the Jurassic Tethyan sediments. The age of the Czajakowa Radiolarite Formation in the stratotype section is determined as U.A.Z.9 to U.A.Z.11 corresponding to middle Oxfordian up to Kimmeridgian. Comparison of radiolarian biozones from the stratotype section with other facial equivalent sections in the Pieniny Klippen Belt reveals a significant diachronism for both the lower and the upper limits of the Jurassic pelagic siliceous facies.
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Abstract

The Marhřgda Bed occurring at base of the Adventdalen Group in Sassenfjorden, Spitsbergen contains common ankerite–replaced belemnite skeletons. Petrographic, major element geochemical, and stable carbon and oxygen isotopic data indicate that the ankerite originated in a catagenic environment associated with thermal degradation of kerogenan d hydrocarbongen erationinthe sequence. It formed at maximum temperature of 150°C under burial of approx. 2 000 m, most probably during Paleogene filling and subsidence of the Central Spitsbergen Basin. Dissolution of biogenic calcite and precipitation of ankerite reflect extensive heat flow through the Adventdalen Group sequence related to the Cretaceous and Paleogene magmatic and orogenic activity in Svalbard.
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Abstract

Diagenetic carbonate deposits (concretions, cementation bodies and cementstone bands) commonly occur in organic carbon-rich sequence of the Agardhfjellet Formation (Upper Jurassic) in Spitsbergen . They are dominated by dolomite/ankerite and siderite. These deposits originated as a result of displacive cementation of host sediment in a range of post-depositional environments, from shallow subsurface to deep-burial ones. Preliminary results of the carbon and oxygen isotopic survey of these deposits in southern Spitsbergen (Lĺgkollane, Ingebrigtsenbukta, Reinodden, and Lidfjellet sections) show the δ13C values ranging between –13.0‰ and –1.8‰ VPDB, and the δ18O values between –16.0‰ and –7.7‰ VPDB. These results suggest that the major stage of formation of the carbonate deposits occurred during burial diagenesis under increased temperature, most probably in late diagenetic to early catagenic environments. Carbonate carbon for mineral precipitation was derived from dissolution of skeletal carbonate and from thermal decomposition of organic matter.
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Abstract

The Marhegda Bed is a carbonate-dominated Uthostratigraphic unit occurring locally at base of the Middle-Late Jurassic organic-rich sequence of the Agardhfjellet Formation in Spitsbergen, Svalbard. It has been interpreted to represent oolitic limestone facies deposited during an initial stage of Late Jurassic transgression. Petrographic, major element geochemical, and stable carbon and oxygen isotopic data presented in this paper indicate that this litho-stratigraphic unit is not a depositional limestone, but a diagenetic cementstone band originated in organic-rich sediment containing glauconite pellets and phosphatic ooids and grains. Two ep­isodes of carbonate diagenesis, including early precipitation of siderite and burial precipitation of ankerite, have contributed to the development of this cementstone. Extensive siderite precipi­tation occurred at sedimentary temperatures in nearsurface suboxic environment in which microbial reduction of ferric iron was the dominant diagenetic process. Precipitation of ankerite occurred at temperatures of about 80-100°C in burial diagenetic environment overwhelmed by thermal decarboxylation processes. Formation of ankerite was associated with advanced alteration of glauconite, dissolution of apatite and precipitation of kaolinite.
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