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K-Ar fault gouge dating of Neogene thrusting; the case of the siliciclastic deposits of the Trasimeno Tectonic Wedge (Northern Apennines, Italy)

Filippo Carboni, Giulio Viola, Luca Aldega, Roelant Van der Lelij, Francesco Brozzetti and Massimiliano R. Barchi
K-Ar fault gouge dating of Neogene thrusting; the case of the siliciclastic deposits of the Trasimeno Tectonic Wedge (Northern Apennines, Italy)
Italian Journal of Geosciences (June 2020) 139 (2): 300-308

Abstract

The Northern Apennines (NA) are a characteristic example of foreland fold-and-thrust belt progressively migrating towards its foreland. Their tectonic evolution has been quite tightly constrained in time by microfossil biostratigraphy applied to syn-orogenic deposits within foreland basins. This makes the NA well suited to test the reliability of K-Ar illite dating of Neogene deformation affecting siliciclastic sequences. We sampled two top-to-the-ENE thrusts, whose well defined cores are defined by scaly gouge formed at the expense of the pelitic component of the host rock. X-ray diffraction (XRD) and K-Ar isotopic analysis of multiple grain-size fractions of the gouge, allowed us to discriminate between syn-kinematic and inherited illite crystals in the fault rocks. Illite age analysis (IAA) constrains fault slip along the thrusts to 15.2+ or -7.6 Ma and 15.4+ or -16.6 Ma. The results, in spite of their analytical uncertainty, are fully consistent with the local evolution of the NA as constrained by the independent biostratigraphic studies and confirm the general suitability of this geochronological approach to Neogene deformation.


ISSN: 2038-1719
EISSN: 2038-1727
Coden: BOGIAT
Serial Title: Italian Journal of Geosciences
Serial Volume: 139
Serial Issue: 2
Title: K-Ar fault gouge dating of Neogene thrusting; the case of the siliciclastic deposits of the Trasimeno Tectonic Wedge (Northern Apennines, Italy)
Affiliation: University of Perugia, Department of Physics and Geology, Perugia, Italy
Pages: 300-308
Published: 202006
Text Language: English
Publisher: Societa Geologica Italiana, Rome, Italy
References: 55
Accession Number: 2020-072351
Categories: StratigraphyGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, geol. sketch maps
N42°00'00" - N44°00'00", E11°00'00" - E13°00'00"
Secondary Affiliation: University of Bologna, ITA, ItalyUniversita di Roma La Sapienza, ITA, ItalyGeological Survey of Norway, NOR, NorwayUniversita G. d'Annunzio, ITA, Italy
Country of Publication: Italy
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute. Abstract, Copyright, Societa Geologica Italiana. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 2020
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