Search

Your search keyword '"Harazim, Dario"' showing total 13 results
Start Over Author "Harazim, Dario"
13 results on '"Harazim, Dario"'

8. Mud deposition and diagenesis within an Early Palaeozoic clinothem: Power Steps Formation, Newfoundland, Canada.

Author

Denommee, Kathryn C., Harazim, Dario, Bentley, Samuel J., Macquaker, James H., Lode, Stefanie, and Olanipekun, Babatunde John

Subjects
*MUD, *DIAGENESIS, *SOIL horizons, *CLAY minerals, *PARAGENESIS, *STORM surges, *SAND waves, *HYDROTHERMAL alteration
Abstract

The early Ordovician (∼385 Ma) Power Steps Formation, Newfoundland, Canada, exposes a well-preserved mudstone-dominated clinothem that serves as an excellent archive for understanding how mud has been produced, transported and converted into mudstone prior to the evolution of globally widespread, deep soil horizons. Sedimentological analysis of four sandstone and five mudstone facies, along the Ochre Cove clinothem, reveal that mud and sand were delivered by unidirectional currents and experienced episodic reworking by storm waves. Petrographic examination and X-ray diffraction from described mudstone facies reveal significant variability in the distribution of illite versus chlorite between the lower and upper part of the Ochre Cove clinothem. This research highlights that in the present-day clay mineral fraction, illite is often detrital whereas chlorite originated via the alteration of silt-sized, highly unstable, mafic (volcanoclastic?) grains. Throughout all sedimentologic facies, albeit in different proportions, these mafic lithic grains were diagenetically altered via in situ weathering before significant compaction occurred, resulting in the precipitation of significant volumes of pore-bridging, silica- and iron-rich chlorite cement. Compositional, diagenetic and textural attributes across the Ochre Cove mud clinothem vary as a function of starting composition, hydrodynamic sorting and grain density. Given that a significant proportion of clay minerals has been generated via in situ transformation of a mafic, non-stable precursor assemblage, we recommend future studies to incorporate detailed petrographic description along with X-ray diffraction analyses when aiming to employ trends in whole-rock clay mineral data as a proxy in provenance and palaeoclimate studies of very old (pre-Devonian) mudstones and sandstones. [ABSTRACT FROM AUTHOR]

Published
2020
Full Text
View/download PDF

11. The enigmatic ichnofossil Tisoa siphonalis and widespread authigenic seep carbonate formation during the Late Pliensbachian in southern France

Author

Schootbrugge, Bas van de, Harazim, Dario, Sorichter, Katrin, Oschmann, Wolfgang, Fiebig, Jens, Püttmann, Wilhelm (Prof. Dr.), Peinl, Mark, Zanella, Friedhelm, Teichert, Barbara M. A., Hoffmann, J., Stadnitskaia, Alina, Rosenthal, Yair, Schootbrugge, Bas van de, Harazim, Dario, Sorichter, Katrin, Oschmann, Wolfgang, Fiebig, Jens, Püttmann, Wilhelm (Prof. Dr.), Peinl, Mark, Zanella, Friedhelm, Teichert, Barbara M. A., Hoffmann, J., Stadnitskaia, Alina, and Rosenthal, Yair

Abstract

Tubular carbonate concretions of up to 1 m in length and perpendicular to bedding, occur abundantly in the Upper Pliensbachian (upper Amaltheus margaritatus Zone, Gibbosus Subzone) in outcrops (Fontaneilles section) in the vicinity of Rivière-sûr-Tarn, southern France. Stable isotope analyses of these concretions show negative delta 13C values that decrease from the rim to the center from - 18.8‰ to - 25.7‰ (V-PDB), but normal marine delta 18 O values (- 1.8‰). Carbon isotope analyses of Late Pliensbachian bulk carbonate (matrix) samples from the Fontaneilles section show clearly decreasing C-isotope values across the A. margaritatus Zone, from +1‰ to - 3‰ (V-PDB). Isotope analyses of coeval belemnite rostra do not document such a negative C-isotope trend with values remaining stable around +2‰ (V-PDB). Computer tomographic (CT) scanning of the tubular concretions show multiple canals that are lined or filled entirely with pyrite. Previously, the formation of these concretions with one, two, or more central tubes, has been ascribed to the activity of an enigmatic organism, possibly with annelid or arthropod affinities, known asTisoa siphonalis. Our results suggest tisoan structures are abiogenic. Based on our geochemical analyses and sedimentological observations we suggest that these concretions formed as a combination of the anaerobic oxidation of methane (AOM) and sulfate reduction within the sediment. Fluids rich in methane and/or hydrocarbons likely altered local bulk rock carbon isotope records, but did not affect the global carbon cycle. Interestingly, Tisoa siphonalis has been described from many locations in the Grands Causses Basin in southern France, and from northern France and Luxemburg, always occurring at the same stratigraphic level. Upper Pliensbachian authigenic carbonates thus possibly cover an area of many thousand square kilometers. Greatly reduced sedimentation rates are needed to explain the stabilization of the sulfate-methane transition zone

Published
2010

Catalog

Books, media, physical & digital resources
See catalog results