Joachim Szulc

The Middle Triassic magnetostratigraphy from the Peri-Tethys basin in Poland

Abstract The paper presents the first complete magnetic polarity scale obtained for the Middle Triassic of the northern Peri-Tethys area. The Roetian and Muschelkalk deposits of southern Poland (Upper Silesia, the Holy Cross Mountains) were studied paleomagnetically. The obtained paleopole ‘A’ (52°N, 143°E) fits well to the Middle Triassic (ca. 240 Ma) segment of the Stable European APWP. A set of various quality characteristic directions isolated in 106 samples was used for construction of the composite polarity scale. This Peritethyan scale has been tied with conodont zonation and referred to the scale erected earlier in the Tethyan realm. Comparison of both scales indicates that the whole Roetian succession in the southern Polish basin should be correlated with the latest Olenekian. The normal marine sedimentation ceased in the Polish basin as early as in the late Fassanian time. The obtained magnetostratigraphic scale combined with the sequence stratigraphic framework enables a reliable chronological correlation of the late Olenekian–Ladinian succession over the entire Peri-Tethys Basin.

The lower permian freshwater carbonates of the Slawkow graben, Southern Poland: Sedimentary facies context and stable isotope study

Abstract During early Permian times the post-Hercynian rift valley known as the Slawkow graben was filled with typical continental molasse deposits including fanglomerates and olistolites, playa flat sediments with evaporites, volcaniclastics and carbonates deposited in small spring-fed basins (oasis environment). Lithofacies variability, lithofacies relationships, sedimentary structures and paleokarst data indicate a highly changeable sedimentary environment controlled by climate, syndepositional faulting, and accompanying volcanism. Differential uplift resulted in a high-relief topography, the basin-margin mountains probably having a relative altitude of up to 1000 m. The stable isotopic composition ( δ 13 C, δ 18 O) of the spring-related carbonates indicate seasonal temperature differences of up to 15°C, a value that is close to the average annual temperature amplitude in the present-day subtropical zone. Other environmental indicators (e.g. red beds, evaporites, braided-stream sediments) corroborate the isotopic interpretation. A longer-term 6–7 year cycle, reflected in δ 18 O-composition of the carbonate, is attributed to rainfall fluctuations.

Middle Jurassic stromatactis mud-mound in the Pieniny Klippen Belt (Western Carpathians)

SummaryA stromatactis mud-mound has been found near Slavnické Podhorie in the Czorsztyn Unit of the Pieniny Klippen Belt (Western Carpathians, Slovakia). Its stratigraphic range is Bathonian to Callovian and it is one of the youngest known true stromatactis mud-mounds. The complete shape the mound is not visible since the klippe is a tectonic block encompassed by younger Cretaceous marls. The matrix is micritic to pelmicritic mudstone, wackestone to packstone with pelecypods, brachiopods, ammonites, and crinoids. An important component of the mound is stromatactis cavities that occur as low as the underlying Bajocian-Bathonian crinoidal limestones. The stromatactis cavities are filled by radiaxial fibrous calcite (RFC) as well as in some places by internal sediment and, finally, by clear blocky calcite. Some cavities remain open with empty voids in the centres. In some stromatactis cavities, tests of cavedwelling ostracodsPokornyopsis sp. were found, surrounded by the latest stages of the RFC. This indicates that stromatactis cavities formed an open network enabling migration of the ostracods and their larvae over a period of time.Except in the case of the stromatactis cavities, there are numerous examples of seeming recrystallizationsensu Black (1952) and Ross et al. (1975) and Bathurst (1977). The radiaxial fibrous calcite encloses patches of matrix and isolated allochems. The RFC crystals are oriented perpendicularly to the substrate whether it is a cavity wall or enclosed allochems. This means that the RFC crystals could not grow from the centre of the cavity outward as postulated by Ross et al. (1975). There are also numerous “floating” isolated allochems, which are much smaller than the surrounding RFC crystals. The explanation involving three-dimensional interconnection of allochems seems to be unlikely. In the discussed mud-mound there is a conflict between apparently empty cavities that had to exist in the sediment and seeming “recrystallization” related to the same RFC that forms the initial void filling. The authors favor an alternative explanation of the “recrystallization”. We presume that the allochems served as nucleation points on which the crystals started to grow. Obviously, the allochems and the micritic patches were different from the surrounding material. RFC crystals (either short-or long-bladed) of the “recrystallization” spar grew at the expense of decaying microbial mucillages. The mucus can enclose peloids, allochems, or whole micritic patches that “floated” in the cavity and served as nucleation sites for the RFC crystals. The entire mud-mound represents a microbially bound autochthonous micritic mass; the stromatactis and stromatactis-like cavities originated where purer mucillage patches occurred, giving rise to open spaces. Such features as the morphological variety of stromatactis fabrics, the pervasive penetration of the sparry calcite into matrix, and the enclosure of the “floated” allochems and mudstone patches by sparry calcite, seem to provide support for the presence of mucus aggregates within the mound body. The mucus might be related to protozoans rather than to sponges or other well organized metazoan organisms.Occurrence of the stromatactis cavities in the underlying Bajocian-Bathonian crinoidal limestones support the inference on biological origin of the stromatactis fabrics. The alternative inorganic models of stromatactis origin (e.g., internal erosion or water-escape) are hardly applicable to the sediment formed by crinoidal skeletal detritus.

Weathering, sedimentary and diagenetic controls of mineral and geochemical characteristics of the vertebrate-bearing Silesian Keuper

Abstract Mudstones and claystones from the southern marginal area of the European Upper Triassic, midcontinental Keuper basin (Silesia, southern Poland) were investigated using XRD, organic and inorganic geochemistry, SEM, K-Ar of illite-smectite, AFT, and stable isotopes of O and C in carbonates in order to unravel the consequent phases of the geological history of these rocks, known for abundant fossils of land vertebrates, and in particular to evaluate the diagenetic overprint on the mineral composition. The detected and quantified mineral assemblage consists of quartz, calcite, dolomite, Ca-dolomite, illite, mixed-layer illite-smectite, and kaolinite as major components, plus feldspars, hematite, pyrite, chlorite, anatase, siderite, goethite as minor components. Palygorskite, gypsum, jarosite and apatite were identified in places. The K-Ar dates document a post-sedimentary thermal event, 164 Ma or younger, which resulted in partial illitization of smectite and kaolinite. The maximum palaeotemperatures were estimated from illite-smectite as ~125°C. Apatite fission track data support this conclusion, indicating a 200-160 Ma age range of the maximum temperatures close to 120°C, followed by a prolonged period of elevated temperatures. These conclusions agree well with the available data on the Mesozoic thermal event, which yielded Pb-Zn deposits in the area. Organic maturity indicators suggest the maximum palaeotemperatures <110°C. Palygorskite was identified as authigenic by crystal morphology (TEM), and calcite by its accumulation in soil layers and by its isotopic composition evolving with time, in accordance with the sedimentary and/or climatic changes. Dolomite isotopic composition indicates more saline (concentrated) waters. Palygorskite signals a rapid local change of sedimentary conditions, correlated with algal blooms. This assemblage of authigenic minerals indicates an arid climate and the location at the transition from a distal alluvial fan to mudflat. Fe-rich smectite, kaolinite, and hematite were products of chemical weathering on the surrounding lands and are therefore mostly detrital components of the investigated rocks. Kaolinite crystal morphology and ordering indicates a short transport distance. Hematite also crystallized in situ, in the soil horizons. A large variation in kaolinite/2:1 minerals ratio reflects hydraulic sorting, except of the Rhaetian, where it probably signals a climatic change, i.e. a shift in the weathering pattern towards kaolinite, correlated with the disappearance of hematite. Quartz, 2M1 illite, and minor feldspars and Mg-chlorite were interpreted as detrital minerals. The documented sedimentation pattern indicates that in more central parts of the Keuper playa system, where an intense authigenesis of the trioctahedral clays (chlorite, swelling chlorite, corrensite, sepiolite) took place, illite and smectite were the dominant detrital clay minerals. Cr/Nb and Cr/Ti ratios were found as the best chemostratigraphic tools, allowing for the correlation of all investigated profiles. A stable decrease of these ratios up the investigated sedimentary sequence is interpreted as reflecting changes in the provenance pattern from more basic to more acidic rocks.

Late Paleozoic Continental Gastropods from Poland: Systematic, Evolutionary and Paleoecological Approach

Abstract Two taxa of the Late Carboniferous and four species of the Early Permian terrestrial snails have been found in the Late Paleozoic continental molasse sediments of the Upper Silesian-Cracow Upland (Southern Poland). Discovery of Anthracopupa ohioensis and Protodiscus priscus indicates that, besides in North America, they occurred also in the European part of the Pangea supercontinent. According to the general sedimentary facies context and the accompanying floral and faunal assemblages, the gastropods lived in swamp environments, including a topogenous fen.