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Kinematics of Jurassic rifting, mantle exhumation, and passive-margin formation in the Austroalpine and Penninic nappes (eastern Switzerland)

Nikolaus Froitzheim and Gianreto Manatschal
Kinematics of Jurassic rifting, mantle exhumation, and passive-margin formation in the Austroalpine and Penninic nappes (eastern Switzerland)
Geological Society of America Bulletin (September 1996) 108 (9): 1120-1133

Abstract

The Austroalpine and Upper Penninic nappes in eastern Switzerland represent a passive continental margin and the adjacent ocean of Jurassic-Cretaceous age, imbricated by Late Cretaceous-Tertiary orogenic shortening. Well-preserved, rift-related faults allow reconstruction of the passive margin and ocean-continent transition zone and yield new information on the kinematics of rifting. Rifting evolved from pure-shear stretching to detachment-controlled, asymmetric stretching and resulted in complete exhumation of subcontinental mantle rocks at the sea floor. After precursory normal faulting in the Late Triassic, Jurassic rifting occurred in two phases. During the first rifting phase (Hettangian-Sinemurian), predominantly east-dipping normal faults developed in the upper crust; their dips decreased in the middle to lower crust, where they probably graded into anastomosing shear zones in the lower crust and mantle lithosphere. The resulting overall geometry approximated pure-shear stretching. During the second rifting phase (Toarcian-Middle Jurassic), a system of west-dipping detachment faults formed, penetrating the whole lithosphere and accommodating asymmetric extension. During progressive stretching, subcontinental mantle rocks were tectonically exhumed and exposed at the sea floor in two areas, represented by the Platta and Malenco nappes (Penninic). The intervening Margna and Sella continental nappes are interpreted as an extensional allochthon belonging to the Apulian margin. Finally, a mid-ocean ridge may have formed west of the Margna-Sella allochthon. The Austroalpine realm thus represents the lower-plate margin-and the Brianconnais, the upper-plate margin-of the Piemont-Liguria ocean. This scenario is in qualitative agreement with the subsidence histories of the two margins.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 108
Serial Issue: 9
Title: Kinematics of Jurassic rifting, mantle exhumation, and passive-margin formation in the Austroalpine and Penninic nappes (eastern Switzerland)
Affiliation: Universitaet Basel, Geologisch-Palaeontologisches Institut, Basel, Switzerland
Pages: 1120-1133
Published: 199609
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 90
Accession Number: 1996-074691
Categories: Structural geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., geol. sketch map
N46°15'00" - N46°45'00", E09°30'00" - E10°30'00"
Secondary Affiliation: ETH-Zentrum, CHE, Switzerland
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 199623
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