Sediment 2007 Posterabstracts Sediment 2007 THE LATE TRIASSIC HAUPTDOLOMITE SECTION WIESTALSTAUSEE NEAR HALLEIN (NORTHERN CALCAREOUS ALPS, AUSTRIA): BIOMARKER EVIDENCE FOR THE FORMATION OF ORGANIC-RICH SUCCESSIONS IN SMALL SCALE BASINS WITHIN CARBONATE PLATFORMS A. Bechtel1,2, H.-J. Gawlick1, R. Gratzer1, M. Tomaselli1, and W. Püttmann3 1 Department Angewandte Geowissenschaften und Geophysik, Montanuniversität Leoben, Peter-Tunner-Str. 5, A-8700 Leoben, Austria 2 Institute of Mineralogy and Petrology, University of Bonn, Poppelsdorfer Schloss, D-53115 Bonn, Germany 3 Institute of Atmospheric and Environmental Sciences, Department of Environmental Chemistry, J. W. Goethe-Universität, Georg-Voigt-Str. 14, D-60054 Frankfurt a.M., Germany The origin of organic-bearing reducing sediments green sulfur bacteria (Chlorobiaceae), indicates the estab- within the Late Triassic Hauptdolomite/Dachstein carbon- lishment of euxinic conditions in the bottom water. ate platform of the Northern Calcareous Alps, a subject of some debate, is clarified by microfacies biomarker analy- Comparable diagenetic degradation mechanisms led ses that enable the characterization of the depositional to the formation of hopanes and hop-17(21)-enes. environment of the Norian dolomicrites (Hauptdolomite) Methylated chromans occur in low abundance, and the of the Wiestalstausee section (Lower Tirolic nappe, predominant occurrence of trimethylated C29 chroman Salzburg Calcareous Alps). By examining the section using (tri-MTTC) over dimethylated C28 chroman (di-MTTC) indi- the oxygen-restricted biofacies (ORB) classification, we cates enhanced salinity in the upper part of the water col- find ORB 1-4 mostly in the dark grey organic- rich sedi- umn. Diagenetic conversion of organic matter under ments and ORB 6, or normal oxygen conditions for the anoxic conditions in a high-sulfur environment due to light grey dolomites. Anaerobic biofacies, characterized salinity stratification are further indicated by low Pr/Ph by the total absence of benthic organisms and a fissile values and high contents of the C35 benzohopane com- sediment fabric, predominate for most of the dark grey pared to the C32 to C34 homologues. The relative propor- and micritic parts of the section. The laminated dolomi- tions of S/R isomers of the ααα C29 steranes and the crites show ORB 3 and ORB 4, containing very few benthic αβ C31 hopanes are consistent with an organic matter species, which are abundant on some bedding planes in maturity equivalent to vitrinite reflectance values of ORB 4. Here, the sediment fabric is planar laminated, but ~0.5% Rr. This maturity assessment is further confirmed limited bioturbation may occur. This sediment type corre- by the predominance of monoaromatic over triaromatic sponds to the poikiloaerobic and episodically dysaerobic steroids. facies. In the present study, the interaction of salinity varia- The n-alkane distribution patterns and relative intensi- tions, water column stratification, and the establishment ties of steranes are typical for organic matter of predomi- of anoxic conditions within a restricted carbonate plat- nantly algal and/or microbial origin with minor contribu- form is highlighted using molecular indicators. For the tions from land plants. Phytoplankton (including dinofla- first time, sedimentological and geochemical features gellates) and photosynthetic bacteria are considered as provide evidence for the establishment of small-scale the major primary producers of the biomass accumulated anoxic basins through erosion by currents or from the within the immature, carbonate-rich rocks. High contents remnants of channels, which were possibly isolated peri- of hopanoid biomarkers and constituents related to the odically by small scale sea level changes. Changes in car- arborane/fernane skeleton are considered to be of bacter- bonate production also may play a role. Beside tectonical- ial origin and indicate enhanced microbial activity in the ly induced formation of anoxic basins in the Late Triassic sedimentary environment. However, a terrestrial origin carbonate platform (e.g., Seefeld basins), this mechanism (from land plants) of the arborane/fernane-derivatives may contribute to the enhancement of the hydrocarbon cannot be excluded. The occurrence of aryl isoprenoids, potential of the Hauptdolomite/Dachstein carbonate probably derived from carotenoids of the photosynthetic platform of the in the whole western Tethyan realm. Geo.Alp, Vol. 4, 2007 39 Sediment 2007 THE SEDIMENTOLOGICAL, PALEONTOLOGICAL AND GEOCHEMICAL IMPLICATIONS OF THE BASAL CHOTEČ EVENT (MIDDLE DEVONIAN, EIFELIAN) IN PRAGUE BASIN (CZECH REPUBLIC) Stanislava Berkyová and Jiří Frýda Stanislava Berkyová, Charles University, Faculty of Science, Department of Geology and Paleontology; [email protected] Albertov 6, 128 43 Prague and Czech Geological Survey, Geologicka 6, 150 00 Prague, Czech Republic; Jiří Frýda, Czech Geological Survey, Geologicka 6, 150 00 Prague, Czech Republic; [email protected] The Basal Choteč event, first named by House (1985) (KJB307020602). It represents our contribution to the and typified by sequences in Bohemia (Chlupáč and Kukal, IGCP 499. 1986) has been documented in Central and Southern Eu- rope (e.g. Chlupáč et al. 2000), North Africa (e.g. Becker and House 1994), Southern America (Troth 2005), North Becker, R.T. & House, M. R. (1994): International Devonian America (Ver Straeten 2005), Siberian platform (Yolkin et goniatite zonation, Emsian to Frasnian, with new al. 2005) and therefore it is regarded as an important records from Morocco. – Cour. Forsch. Inst. Senckenb., global geo-event. In its type area (Prague Basin) the afore- 169: 79–135. mentioned event falls at the boundary between the Tře- Chlupáč, I. & Kukal Z. (1986): Reflection of possible global botov Limestone (Emsian/Eifelian) and the Choteč Lime- Devonian events in the barrandian area, C.S.S.R. – In: stone (Eifelian) and their equivalents, close above the Lecture Note in Earth Sciences, Global Bio-events, ed. Lower-Middle Devonian boundary. It is correlated with O. Walliser, 169–179, Springer-Verlag, Berlin. the base of the Pinacites jugleri and Polygnathus costatus Chlupáč, I., Feist, R. & Morzadec, P. (2000): Trilobites and costatus biozons. The Třebotov Limestone is mostly a bio- standard Devonian stages. – In: Bultynck, P. (Ed.), Sub- clastic wackestone-packstone with a relatively high bio- commision on Devonian Stratigraphy: Fossils Groups genic content and intense bioturbation. The presence of Important for Boundary Definition. – Cour. Forsch. Inst. micritic matrix, benthic fauna typical for muddy bottom Senckenb., 220: 87–98. environments and absence of sedimentological features House, M. R. (1985): Correlation of mid-Palaeozoic indicating current activity suggest a calm, low-energy, ammo noid evolutionary events with global sedimen- relatively deep sedimentary environment rich in free oxy- tary perturbations. – Nature, 313:17–22. gen (inferred from intense bioturbation and diverse ben- Troth, I. (2005): When did the Malvinokaffric real break- thic assemblages). The sedimentary environment is inter- down? – In E. A. Yolkin (ed.): Contributions to the IGCP preted here as proximal offshore, bellow storm wave base. 499 Project (Devonian Terrestrial and Marine environ- The Choteč Limestone, on the other hand, reflects in its ments: From Contient to Shelf. Novosibirsk, Publishing development and fossil content perturbation and non House of SB RAS, 2005. steady state conditions. The above mentioned limestone is Ver Straten C. A. (2005): The Late Pragian, Emsian, And represented by the alternation of well-sorted peloidal Eifelian in the Appalachian Basin, Eastern U.S.A. – In E. packstone/grainstone and dark lime- mudstone/wacke- A. Yolkin (ed.): Contributions to the IGCP 499 Project stone and are regarded here as a representatives of tem- (Devonian Terrestrial and Marine environments: From pestites, reflecting in its development eustatic oscillations Contient to Shelf. Novosibirsk, Publishing House of SB in sea level. RAS, 2005. Yolkin E.A., Izokh N.G., Obut O.T. & Kipriyanova, T.P. (2005): Acknowledgements Field Excursion Guidebook to the IGCP 499 Project (De- vonian Terrestrial and Marine environments: From The research is supported by the grant of Grant Agency Contient to Shelf). – Novosibirsk, Publishing House of of the Academy of Science of the Czech Republic SB RAS, 2005. 40 Geo.Alp, Vol. 4, 2007 Sediment 2007 PALEOMETEOROLOGY OF DUST EVENTS Stephan Dietrich1, Klemens Seelos1, and Frank Sirocko1 1 Johannes Gutenberg-Universität Mainz, Institut für Geowissenschaften; [email protected] 16 long sediment cores from Eifel dry maar lakes have hemisphere, as documented in the North GRIP dust parti- been drilled between 1999 and 2005 by the ELSA project cle record (Ruth et al. 2003), should indicate if dust storms (Eifel Laminated Sediment Archive) and document the last in the Eifel are associated with large hemispheric weather 0 - 140 ka. In this project we will evaluate in detail distinct extremes (high pressure cells over eastern Europe and dust layers, which can be correlated between the cores. Siberia or storms in the west wind drift) and thus with a Dust phases (dry and cool winds > 5m/s) over the conti- hemisphere wide forcing process or only local/regional nent have been related to the cold events in the Greenland weather anomalies in the Eifel. ice and North Atlantic sea surface temperature patterns (Seelos & Sirocko, 2006). A continuous dust stack (0-140 ka)