The long-term evolution of Monte Marine and Monte Pettino seismogenic faults: tectono-stratigraphic, isotopic, and chronological constraints

Giorgio Arriga, Philippe Claeys, Marta Marchegiano, M. Y. Peral, Federico Rossetti, Domenico Cosentino, Paola Cipollari, Michele Soligo, Valentina Argante, Junjie Zhang, Hsun-Ming Hu, Chuan-Chou Shen, Mauro Brilli

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The central Apennines are a Cenozoic fold-and-thrust belt that has been affected by post-orogenicextension in its axial region since the end of the early Pliocene (ca. 4 Ma). Post-orogenic extensiongenerated several intermontane basins bounded by high-angle normal faults, striking NW-SE,subparallel to the backbone of the chain. The Monte Pettino and the Monte Marine seismogenicfaults (MPF, MMF) are the boundary faults of the western portion of the late Pliocene-QuaternaryL’Aquila intermontane basin. Their long-term activity is typified by exhumed fault cores thatcoexist with active fault strands localised at the fault hanging walls, providing evidence of apolyphase tectonic activity. The fault cores are decorated by diffuse dolomitization, which indicatesstructurally controlled fluid-flow and metasomatism. To constrain the long-term (space-time)evolution of the MPF-MMF faults, we integrated fieldwork, stable isotope systematics (δ18O, δ13Cand Δ47), carbonate thermoluminescence and U-Th dating. Our results highlight two main tectonicphases, with different structural evolution and fluid-rock interaction. The first phase correspondsto the development of a major cataclastic zone, defined by meter-thick, SW-dipping (65-70°), faultcores exposed at the piedmont of the MPF-MMF ridges. The C-O systematics of the cataclasite andof the associated calcite slickenfibers, which are in the range of the carbonate bedrock, indicate a"closed" system behaviour during fault nucleation and development. Preliminary results from Δ47thermometry of syn-kinematic carbonate structures indicate temperatures of 34 ± 2 °C.Thermoluminescence dating of dolomite clasts in the fault zone indicates age in the range of 3.0 –3.4 Ma, whilst the cataclastic fault core is younger (< 800 ka). The second phase is mainly recordedin upper Pleistocene sedimentary Breccias (ca. 350 ka) which unconformably cover the bedrockand the exhumed fault cores at the SE termination of the MPF. It consists of anastomosed, highangleWNW-ESE striking fault strands, spaced meters apart and with cm-m displacements,associated with carbonate veining and travertines. Stable isotopes measured from the faultslickenfibers, carbonate veins and travertines show negative δ13C and δ18O values, suggesting a depositional system dominated by meteoric fluid ("open" system) with an important contributionof organic carbon. Travertines and veins precipitated at colder temperatures (12 ± 2 °C), in therange of the average local air temperatures, thus excluding precipitation from a hydrothermalcircuit. Moreover, their U-Th ages range between 182 and 331 ka, compatible with the temporalconstraints from stratigraphic data. Structural and isotopic results do not support tectonicreactivation of the cataclastic core of the MPF during the middle-late Pleistocene, confirming thestratigraphic evidence. Our results provide the first absolute age constraint on the post-orogenicextensional faulting in the L’Aquila basin, demonstrating a two-stage fault activity, characterised bya change from localised (from ca. 3 to ca. 0.8 Ma) to delocalised faulting (200-300 ka to present).We infer that this change in the style of extensional faulting was consequence of the evolvingrheological structure of the fault zones, primarily regulated by the feedback and interactionsinvolving structurally-controlled fluid flow, rock metasomatism and cataclastic processes in spaceand time.
Originele taal-2English
TitelEGU General Assembly Conference Abstracts
UitgeverijEuropean Geosciences Union (EGU)
Pagina's1-1
Aantal pagina's1
Uitgave2023
StatusPublished - 26 feb 2023
EvenementEGU General Assembly 2023 - Austria Center Vienna (ACV), Vienna, Austria
Duur: 23 apr 202328 apr 2023
Congresnummer: EGU23-9009
https://www.egu23.eu/

Conference

ConferenceEGU General Assembly 2023
Verkorte titelEGU23
Land/RegioAustria
StadVienna
Periode23/04/2328/04/23
Internet adres

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