The effects of pre-existing normal faults on thrust ramp development: An example from the northern Apennines,Italy |
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Authors: | E Tavarnelli |
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Institution: | (1) Dipartimento di Scienze della Terra, Via delle Cerchia 3, I-53100 Siena, Italy;(2) Present address: Department of Geology and Geophysics, University of California, 94720 Berkeley, California, USA |
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Abstract: | The Umbria-Marche foreland fold-and-thrust belt in the northern Apennines of Italy provides excellent evidence to test the
hypothesis of synsedimentary-structural control on thrust ramp development. This orogenic belt consists of platform and pelagic
carbonates, Late Triassic to Miocene in age, whose deposition was controlled by significant synsedimentary extension. Normal
faulting, mainly active from Jurassic through Late Cretaceous-Paleogene time, resulted in significant lateral thickness variability
within the related stratigraphic sequences. By Late Miocene time the sedimentary cover was detached from the underlying basement
and was deformed by east-verging folds and west-dipping thrusts. Two restored balanced cross sections through the southernmost
part of the belt show a coincidence between the early synsedimentary normal faults and the late thrust fault ramps. These
evidences suggest that synsedimentary tectonic structures, such as faults and the related lithological lateral changes, can
be regarded as mechanically important controlling factors in the process of thrust ramp development during positive tectonic
inversion processes. |
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Keywords: | Umbria-Marche Apennines Synsedimentary normal faults Thrust ramps Mechanical heterogeneities Positive tectonic inversion |
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