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Thermochronologic evidence for orogen-parallel variability in wedge kinematics during extending convergent orogenesis of the Northern Apennines, Italy

Stuart N. Thomson, Mark T. Brandon, Peter W. Reiners, Massimiliano Zattin, Peter J. Isaacson and Maria Laura Balestrieri
Thermochronologic evidence for orogen-parallel variability in wedge kinematics during extending convergent orogenesis of the Northern Apennines, Italy
Geological Society of America Bulletin (July 2010) 122 (7-8): 1160-1179

Abstract

Analysis of 146 new apatite (U-Th)/He ages, six new apatite fission-track ages, and 165 previously published apatite fission-track (AFT) ages from the northern Apennine extending convergent orogen reveals a significant along-strike change in post-late Miocene wedge kinematics and exhumation history. East of approximately 11 degrees 30'E, age patterns and age-elevation relationships are diagnostic of ongoing frontal accretion and slab retreat consistent with a northeastward-migrating "orogenic wave." Enhanced erosion rates of approximately 1 mm/yr over a period of approximately 3-5 Ma are recorded on the contractional pro-side of the orogen and approximately 0.3 mm/yr on the extending retro-side. West of approximately 11 degrees 30'E, ongoing exhumation has been restricted to the range core since at least ca. 8 Ma at rates of approximately 0.4 mm/yr increasing to approximately 1 mm/yr in the Pliocene (ca. 3 Ma) accompanied by post-Pliocene tilting and associated faulting. This pattern can be attributed to either continued convergence (but a switch in the transfer of material into the wedge to a regime dominated by underplating or out-of-sequence shortening), or a slowdown or cessation of frontal accretion and slab retreat with enhanced Pliocene uplift and erosion triggered by a deeper seated process such as lithospheric delamination, complete slab detachment, or slab tear. These findings emphasize that no single model of wedge kinematics is likely appropriate to explain long-term northern Apennine orogenesis and synconvergent extension, but rather that different lithospheric geodynamic processes have acted at different times in different lateral segments of the orogen.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 122
Serial Issue: 7-8
Title: Thermochronologic evidence for orogen-parallel variability in wedge kinematics during extending convergent orogenesis of the Northern Apennines, Italy
Affiliation: Yale University, Department of Geology and Geophysics, New Haven, CT, United States
Pages: 1160-1179
Published: 201007
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 135
Accession Number: 2010-050192
Categories: Structural geologyGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 2009284; includes appendix
Illustration Description: illus. incl. geol. sketch map
N43°00'00" - N45°00'00", E09°00'00" - E13°00'00"
Secondary Affiliation: University of Arizona, USA, United StatesUniversita di Bologna, ITA, ItalyCNR, Istituto di Geoscienze e Georisorse, ITA, Italy
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, 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: 201027
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