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Early Cretaceous tectonic event in the Adria: Insight from Umbria-Marche pelagic basin (Italy)

By
Marco Menichetti
Marco Menichetti
Dipartimento di Scienze Pure e Applicate, Università degli Studi di Urbino “Carlo Bo,” Campus Scientifico, Località Crocicchia, 61029 Urbino, Italy
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Published:
July 01, 2016

Soft-sediment deformation structures crop out in the Lower Cretaceous succession of the Gubbio anticline in the Umbria-Marche Apennines of Italy. The deformation interval is ~13 m thick and occurs between the upper Hauterivian–lower Aptian Maiolica Formation and the Aptian Marne a Fucoidi Formation. It can be observed along the anticline for a distance of 12 km.

Different types of deformation structures are distributed in several outcrops, with detachment extensional structures prevailing in the southeast sector. Imbricated slides, slump structures, and chaotic layers are distributed vertically and longitudinally in the middle and/or lower part of the deformed sediments. In the northwest sector of the anticline, compressional duplex structures can be considered the lower section of a large sediment failure. Geometrical and kinematic analysis of the fold axis trends and sliding surfaces have led to infer a single, large gravitational event possibly Albian in age.

The synsedimentary deformation could be activated by several internal trigger mechanisms induced by external regional tectonic events such as earthquakes. An orthogonal system of calcite veins crossing the limestone layers represents the primary pathway for fluid-driven breaching of joint seals. These fluids can be related to the significant increase in the total organic carbon in the Hauterivian–Aptian layer of the Maiolica and Marne a Fucoidi Formations. This suggests the possibility that the limestone layer, sandwiched and sealed between clay of the organic-rich black shales, could have favored a pore pressure increase approaching lithostatic stress. With a thin overburden, lithostatic stress is more easily reached at low hydrostatic pressure.

This slump sheet occurrence suggests the existence of a local paleoslope dipping toward the north-northwest, where the mass involved in the deformation is distributed over an estimated area of 60 km2 for a volume of 0.8 km3 of displaced sediments.

The restoration and rotation of the slump fold hinges to the Early Cretaceous direction, in line with available paleomagnetic data, have shown that the strike of the slope corresponds to the main trend of the oldest Jurassic extensional lineaments and is linked to transform faults of the westernmost Tethys rifting systems.

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GSA Special Papers

The Stratigraphic Record of Gubbio: Integrated Stratigraphy of the Late Cretaceous–Paleogene Umbria-Marche Pelagic Basin

Marco Menichetti
Marco Menichetti
Dipartimento di Scienze Pure e Applicate, Universita` degli Studi di Urbino, 61029 Urbino (PU), Italy
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Rodolfo Coccioni
Rodolfo Coccioni
Dipartimento di Scienze Pure e Applicate, Universita` degli Studi di Urbino, 61029 Urbino (PU), Italy
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Alessandro Montanari
Alessandro Montanari
Osservatorio Geologico di Coldigioco, Cda. Coldigioco 4, 62021 Apiro (MC), Italy
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Geological Society of America
Volume
524
ISBN print:
9780813725246
Publication date:
July 01, 2016

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