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Fluid pressure cycles, variations in permeability, and weakening mechanisms along low-angle normal faults; the Tellaro Detachment, Italy

Luca Clemenzi, Fabrizio Storti, Fabrizio Balsamo, Giancarlo Molli, Rob Ellam, Philippe Muchez and Rudy Swennen
Fluid pressure cycles, variations in permeability, and weakening mechanisms along low-angle normal faults; the Tellaro Detachment, Italy
Geological Society of America Bulletin (May 2015) 127 (11-12): 1689-1710

Abstract

Classical frictional fault reactivation models indicate that slip along misoriented fault planes is not possible under most conditions. Nevertheless, active or exhumed low-angle normal faults have been described in many settings worldwide. This discrepancy is addressed by contrasting models: (1) those proposing that low-angle normal faults result from postkinematic passive rotation of former high-angle extensional faults; and (2) those proposing that specific conditions can promote slip along misoriented fault planes. This paper describes the Tellaro detachment, a mid-late Miocene low-angle normal fault that was responsible for approximately 500 m of tectonic vertical thinning in the carbonate-dominated Triassic to Lower Miocene succession of the Northern Apennines, Italy. By integrating structural, petrographic, isotopic, and fluid inclusion data, we show that: (1) the main kinematic activity of the Tellaro detachment occurred between approximately 8 and 4 km depths and peak temperature approximately 190 degrees C; (2) dilational breccias, tens of cubic meters in volume, are frequently associated with major low-angle fault segments; (3) slip along misoriented planes was favored by elevated fluid pressures and low differential stress; and (4) the fault system was characterized by transient permeability pulses and overpressure buildups, associated with multiple fracturing and cementation events that caused the downward migration of master slip surfaces. Results presented in this study show that: (1) in a fluid-active regime, continental crustal thinning can occur for shallow values of fault dip; (2) low-angle normal faults have a great influence on fluid circulation within the upper crust; and (3) episodic permeability enhancement and destruction in detachment faults can promote overpressure buildups, triggering deformation episodes.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 127
Serial Issue: 11-12
Title: Fluid pressure cycles, variations in permeability, and weakening mechanisms along low-angle normal faults; the Tellaro Detachment, Italy
Affiliation: University of Parma, Department of Physic and Earth Sciences "Macedonio Melloni", Parma, Italy
Pages: 1689-1710
Published: 20150519
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 139
Accession Number: 2015-081895
Categories: Structural geology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2015178
Illustration Description: illus. incl. sects., geol. sketch maps
N44°00'00" - N44°10'00", E09°00'00" - E10°00'00"
Secondary Affiliation: Scottish Universities Environmental Research Centre, GBR, United KingdomKatholieke Universiteit Leuven, BEL, Belgium
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201535
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