The Experts below are selected from a list of 255 Experts worldwide ranked by ideXlab platform
Anna Antoshkina - One of the best experts on this subject based on the ideXlab platform.
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Ooid stromatolite association as a precursor of bioevents silurian timan northern ural region
Palaeoworld, 2015Co-Authors: Anna AntoshkinaAbstract:Abstract This study reports the frequent occurrence of Ooid-stromatolite association levels at the starting of bioevents at various Silurian stratigraphical boundaries in the Timan–northern Ural region. Five genetic types of Ooids show various depositional settings and environments of their formation. The important feature of studied Ooids is the fact that calcite crystals of their cortex have the distinct traces of dissolution formed by organic acids of embedded microorganisms. A honeycomb-like pattern of subpolygonal to subspherical pits and walls is interpreted as calcified extracellular polymeric substance (EPS) within stromatolite fabrics and some microscopic Ooids (less than 0.1 mm in size) in the beginning of their microbial cortex formation are locally visible. This is important observation because well-preserved different fabrics seen in ancient Ooids and stromatolites have previously been interpreted to represent paleoenvironmental conditions brought about by different scale changes in benthic assemblages. Results from this study suggest that it is possible that the connection of Ooids with stromatolites at these time-levels depends on their genetic relationship to abundance microbial habitats in the Silurian shallow water marine basin of the region.
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Ooid-stromatolite association as a precursor of bioevents (Silurian, Timan–northern Ural Region)
Palaeoworld, 2014Co-Authors: Anna AntoshkinaAbstract:Abstract This study reports the frequent occurrence of Ooid-stromatolite association levels at the starting of bioevents at various Silurian stratigraphical boundaries in the Timan–northern Ural region. Five genetic types of Ooids show various depositional settings and environments of their formation. The important feature of studied Ooids is the fact that calcite crystals of their cortex have the distinct traces of dissolution formed by organic acids of embedded microorganisms. A honeycomb-like pattern of subpolygonal to subspherical pits and walls is interpreted as calcified extracellular polymeric substance (EPS) within stromatolite fabrics and some microscopic Ooids (less than 0.1 mm in size) in the beginning of their microbial cortex formation are locally visible. This is important observation because well-preserved different fabrics seen in ancient Ooids and stromatolites have previously been interpreted to represent paleoenvironmental conditions brought about by different scale changes in benthic assemblages. Results from this study suggest that it is possible that the connection of Ooids with stromatolites at these time-levels depends on their genetic relationship to abundance microbial habitats in the Silurian shallow water marine basin of the region.
Philippe Courville - One of the best experts on this subject based on the ideXlab platform.
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depositional environments and iron Ooid formation in condensed sections callovian oxfordian south eastern paris basin france
Sedimentology, 2005Co-Authors: Pierreyves Collin, Jeanpaul Loreau, Philippe CourvilleAbstract:Carbonate platforms across Western Europe were superseded at the Middle–Upper Jurassic (Callovian–Oxfordian) boundary either by alternating marl–limestone and widespread marl deposits or by condensed sections containing iron Ooids. The characteristics of marine condensed sections in the south-eastern part of the Paris Basin (France) and their distribution pattern are examined here, and a model of iron Ooid formation is developed. Iron Ooids are found from the shoreface to the offshore zone. They are most abundant in the median-to-distal offshore transition zone, where they originally formed. They also occur commonly, albeit often as reworked grains, in the proximal offshore zone, to which they were transported. The contemporaneous, thick, predominantly marl sections that occur laterally are devoid of iron Ooids and were deposited in deeper settings (distal offshore zone). The iron Ooids are composed of goethite. Typically, they have a nucleus made up of a clump of goethite crystals and a laminated cortex. Three distinctive nanostructures are identified in the cortex laminae: (i) a nanograined crystalline structure typical of primary goethite; (ii) a secondary nanoflaked structure thought to have formed mechanically by reorientation of the goethite crystals; and (iii) a coalesced structure acquired by subsequent diagenetic recrystallization. The iron Ooids formed successively (i) by lamina growth when goethite precipitated in the surface layer of the sediment (nanograined structure) and (ii) by interruption of growth when the Ooids were remobilized by hydrodynamic agents, as reflected by the flaked nanostructure; (iii) these two nanostructures were sometimes transformed into a coalesced structure by recrystallization when Ooids were buried.
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Depositional environments and iron Ooid formation in condensed sections (Callovian Oxfordian, South-eastern part of the Paris basin, France)
Sedimentology, 2005Co-Authors: Collin P.y., Loreau J.p., Philippe CourvilleAbstract:Carbonate platforms across Western Europe were superseded at the MiddleUpper Jurassic (CallovianOxfordian) boundary either by alternating marllimestone and widespread marl deposits or by condensed sections containing iron Ooids. The characteristics of marine condensed sections in the south-eastern part of the Paris Basin (France) and their distribution pattern are examined here, and a model of iron Ooid formation is developed. Iron Ooids are found from the shoreface to the offshore zone. They are most abundant in the median-to-distal offshore transition zone, where they originally formed. They also occur commonly, albeit often as reworked grains, in the proximal offshore zone, to which they were transported. The contemporaneous, thick, predominantly marl sections that occur laterally are devoid of iron Ooids and were deposited in deeper settings (distal offshore zone). The iron Ooids are composed of goethite. Typically, they have a nucleus made up of a clump of goethite crystals and a laminated cortex. Three distinctive nanostructures are identified in the cortex laminae: (i) a nanograined crystalline structure typical of primary goethite; (ii) a secondary nanoflaked structure thought to have formed mechanically by reorientation of the goethite crystals; and (iii) a coalesced structure acquired by subsequent diagenetic recrystallization. The iron Ooids formed successively (i) by lamina growth when goethite precipitated in the surface layer of the sediment (nanograined structure) and (ii) by interruption of growth when the Ooids were remobilized by hydrodynamic agents, as reflected by the flaked nanostructure; (iii) these two nanostructures were sometimes transformed into a coalesced structure by recrystallization when Ooids were buried
Pierreyves Collin - One of the best experts on this subject based on the ideXlab platform.
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depositional environments and iron Ooid formation in condensed sections callovian oxfordian south eastern paris basin france
Sedimentology, 2005Co-Authors: Pierreyves Collin, Jeanpaul Loreau, Philippe CourvilleAbstract:Carbonate platforms across Western Europe were superseded at the Middle–Upper Jurassic (Callovian–Oxfordian) boundary either by alternating marl–limestone and widespread marl deposits or by condensed sections containing iron Ooids. The characteristics of marine condensed sections in the south-eastern part of the Paris Basin (France) and their distribution pattern are examined here, and a model of iron Ooid formation is developed. Iron Ooids are found from the shoreface to the offshore zone. They are most abundant in the median-to-distal offshore transition zone, where they originally formed. They also occur commonly, albeit often as reworked grains, in the proximal offshore zone, to which they were transported. The contemporaneous, thick, predominantly marl sections that occur laterally are devoid of iron Ooids and were deposited in deeper settings (distal offshore zone). The iron Ooids are composed of goethite. Typically, they have a nucleus made up of a clump of goethite crystals and a laminated cortex. Three distinctive nanostructures are identified in the cortex laminae: (i) a nanograined crystalline structure typical of primary goethite; (ii) a secondary nanoflaked structure thought to have formed mechanically by reorientation of the goethite crystals; and (iii) a coalesced structure acquired by subsequent diagenetic recrystallization. The iron Ooids formed successively (i) by lamina growth when goethite precipitated in the surface layer of the sediment (nanograined structure) and (ii) by interruption of growth when the Ooids were remobilized by hydrodynamic agents, as reflected by the flaked nanostructure; (iii) these two nanostructures were sometimes transformed into a coalesced structure by recrystallization when Ooids were buried.
Collin P.y. - One of the best experts on this subject based on the ideXlab platform.
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Depositional environments and iron Ooid formation in condensed sections (Callovian Oxfordian, South-eastern part of the Paris basin, France)
Sedimentology, 2005Co-Authors: Collin P.y., Loreau J.p., Philippe CourvilleAbstract:Carbonate platforms across Western Europe were superseded at the MiddleUpper Jurassic (CallovianOxfordian) boundary either by alternating marllimestone and widespread marl deposits or by condensed sections containing iron Ooids. The characteristics of marine condensed sections in the south-eastern part of the Paris Basin (France) and their distribution pattern are examined here, and a model of iron Ooid formation is developed. Iron Ooids are found from the shoreface to the offshore zone. They are most abundant in the median-to-distal offshore transition zone, where they originally formed. They also occur commonly, albeit often as reworked grains, in the proximal offshore zone, to which they were transported. The contemporaneous, thick, predominantly marl sections that occur laterally are devoid of iron Ooids and were deposited in deeper settings (distal offshore zone). The iron Ooids are composed of goethite. Typically, they have a nucleus made up of a clump of goethite crystals and a laminated cortex. Three distinctive nanostructures are identified in the cortex laminae: (i) a nanograined crystalline structure typical of primary goethite; (ii) a secondary nanoflaked structure thought to have formed mechanically by reorientation of the goethite crystals; and (iii) a coalesced structure acquired by subsequent diagenetic recrystallization. The iron Ooids formed successively (i) by lamina growth when goethite precipitated in the surface layer of the sediment (nanograined structure) and (ii) by interruption of growth when the Ooids were remobilized by hydrodynamic agents, as reflected by the flaked nanostructure; (iii) these two nanostructures were sometimes transformed into a coalesced structure by recrystallization when Ooids were buried
Jeanpaul Loreau - One of the best experts on this subject based on the ideXlab platform.
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depositional environments and iron Ooid formation in condensed sections callovian oxfordian south eastern paris basin france
Sedimentology, 2005Co-Authors: Pierreyves Collin, Jeanpaul Loreau, Philippe CourvilleAbstract:Carbonate platforms across Western Europe were superseded at the Middle–Upper Jurassic (Callovian–Oxfordian) boundary either by alternating marl–limestone and widespread marl deposits or by condensed sections containing iron Ooids. The characteristics of marine condensed sections in the south-eastern part of the Paris Basin (France) and their distribution pattern are examined here, and a model of iron Ooid formation is developed. Iron Ooids are found from the shoreface to the offshore zone. They are most abundant in the median-to-distal offshore transition zone, where they originally formed. They also occur commonly, albeit often as reworked grains, in the proximal offshore zone, to which they were transported. The contemporaneous, thick, predominantly marl sections that occur laterally are devoid of iron Ooids and were deposited in deeper settings (distal offshore zone). The iron Ooids are composed of goethite. Typically, they have a nucleus made up of a clump of goethite crystals and a laminated cortex. Three distinctive nanostructures are identified in the cortex laminae: (i) a nanograined crystalline structure typical of primary goethite; (ii) a secondary nanoflaked structure thought to have formed mechanically by reorientation of the goethite crystals; and (iii) a coalesced structure acquired by subsequent diagenetic recrystallization. The iron Ooids formed successively (i) by lamina growth when goethite precipitated in the surface layer of the sediment (nanograined structure) and (ii) by interruption of growth when the Ooids were remobilized by hydrodynamic agents, as reflected by the flaked nanostructure; (iii) these two nanostructures were sometimes transformed into a coalesced structure by recrystallization when Ooids were buried.
