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Structural evolution of the Prague Synform (Czech Republic) during Silurian times; an AMS, rock magnetism, and paleomagnetic study of the Svaty Jan pod Skalou dikes; consequences for the nappes emplacement

Tahar Aifa, Petr Pruner, Martin Chadima and Petr Storch
Structural evolution of the Prague Synform (Czech Republic) during Silurian times; an AMS, rock magnetism, and paleomagnetic study of the Svaty Jan pod Skalou dikes; consequences for the nappes emplacement (in The evolution of the Rheic Ocean; from Avalonian-Cadomian active margin to Alleghenian-Variscan collision, Ulf Linnemann (editor), R. Damian Nance (editor), Petr Kraft (editor) and Gernold Zulauf (editor))
Special Paper - Geological Society of America (2007) 423: 249-265

Abstract

Silurian effusive basalts and volcaniclastics compose the Svaty Jan volcanic center, which is located in the northwestern limb of the Prague Synform, where three major volcanic phases have been recognized: the first one of early to mid-Wenlock and the last of mid-Ludlow age. Two alkaline basalt dikes of late Wenlock to mid-Ludlow age, respectively tilted to the west and to the northeast, as observed in a 100-m-thick tuff sequence, which represents the second volcanic phase, have been extensively sampled. An anisotropy of the magnetic susceptibility (AMS) study of seventy-nine specimens taken from a 5-m-thick dike (dike 1) and thirty-two specimens cored in a 3.5-m-thick dike (dike 2) shows two different fabrics, carried mainly by Ti-magnetite and/or magnetite, which are considered to be related to the transtensional opening phase of the dikes. Four components of magnetization, attributed to Middle-Late Silurian (C1), Middle-Late Carboniferous (C2), Cretaceous (B), and Paleocene (D), in agreement with already-published directions for the Bohemian Massif, have been isolated. They are carried by Ti-magnetite for components Cl and C2, hematite and goethite for components B and D. The opening mode, which controlled both dikes, corresponds to a dextral transtensional regime, as deduced from the AMS K1 axis. They may have been opened during several magmatic stages related to different injections during late Wenlock to mid-Ludlow times. The first stage is dominant and controlled by the primary fabric, which is mainly oblate. With a NNW-SSE strike, perpendicular to the shortening direction, this fabric is in agreement with the direction of emplacement of the nappes during the Late Devonian. At that time the nappes emplacement that pre-dates this direction was probably associated with the sinistral closure of the Rheic Ocean, in agreement with post-Givetian folding and faulting, which deformed the synform infill and closed the Barrandian marine sedimentary cycle.


ISSN: 0072-1077
EISSN: 2331-219X
Coden: GSAPAZ
Serial Title: Special Paper - Geological Society of America
Serial Volume: 423
Title: Structural evolution of the Prague Synform (Czech Republic) during Silurian times; an AMS, rock magnetism, and paleomagnetic study of the Svaty Jan pod Skalou dikes; consequences for the nappes emplacement
Title: The evolution of the Rheic Ocean; from Avalonian-Cadomian active margin to Alleghenian-Variscan collision
Author(s): Aifa, TaharPruner, PetrChadima, MartinStorch, Petr
Author(s): Linnemann, Ulfeditor
Author(s): Nance, R. Damianeditor
Author(s): Kraft, Petreditor
Author(s): Zulauf, Gernoldeditor
Affiliation: Universite de Rennes I, Geosciences Rennes, Rennes, France
Affiliation: Staatliche Naturhistorische Sammlungen Dresden, Museum fuer Mineralogie und Geologie, Dresden, Federal Republic of Germany
Pages: 249-265
Published: 2007
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 48
Accession Number: 2008-044780
Categories: Structural geologySolid-earth geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, geol. sketch map
N49°55'00" - N50°10'00", E13°45'00" - E14°00'00"
Secondary Affiliation: Ohio University, USA, United StatesCharles University Prague, CZE, Czech RepublicUniversitaet Frankfurt am Main, DEU, Federal Republic of GermanyAcademy of Sciences of the Czech Republic, CZE, Czech Republic
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200813
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