Abstract Reliable macro‐ and meso‐scale structural criteria for identifying pre‐thrusting normal faults within inversion‐dominated foreland thrust belts are here reappraised by showing field cases from the Central‐Northern Apennines of Italy. Field‐based analyses of relative chronologies among the structures allow determination of the timing of pre‐thrusting normal faulting, the positive inversion of the faults and their post‐thrusting reactivation when absolute chronostratigraphic constraints are lacking. The correct identification of pre‐thrusting normal faults allows recognition of shortcut and reactivation anticlines, and these have important implications for the definition of the thrust‐belt structural style and for the estimation of post‐orogenic extension.
Knowledge of seismotectonics, active deformation, and the structure of Earth’s crust is key for the first-order perception and assessment of the seismic hazard, and consequently the seismic risk, of an area [...]
Positive structural inversion within foreland domains ahead of thrust belts can create structures with significant hydrocarbon potential in mature and underexplored areas. Within this context, the Adriatic region represents a well-established hydrocarbon province constituting a foreland domain bounded by the Apennines, Southern Alps, and Dinaric fold-and-thrust belts. Newly reprocessed regional 2D seismic data and a renewed exploration interest in the area motivate a reappraisal of the regional structure and stratigraphy of the deformed Central Adriatic region of Italy (i.e., the Mid-Adriatic Ridge). Here, we developed and discussed examples of inversion structures that have different structural styles. The structural interpretations displayed on time-to-depth converted profiles had been validated by 2D structural-kinematic balancing and forward modeling. Our aim was to better define the geometry, style, and timing of the analyzed inversion-related folds. Positive inversion structures appeared locally as asymmetric harpoon-shaped anticlines riding over high-angle blind thrusts. More commonly, inversion structures were symmetric anticlines formed above conjugate faults. Retrodeformed cross sections showed that positive inversion involved symmetric graben and asymmetric half-graben that originated during the Triassic and Jurassic. That these inversion structures developed during basement-involved thrusting, as suggested for the Adriatic in general, was consistent with forward modeling. Regionally, the contractional structures belonging to the Mid-Adriatic Ridge can be explained in terms of intraplate deformation that chiefly acted through reactivation of Mesozoic normal faults.
The Umiat Basin extends in the eastern sector of the National Petroleum Reserve in Alaska (NPRA) in the North Slope of northwestern Artic Alaska. Newly reprocessed 2D regional seismic profiles extending through the entire NPRA provide a clearer resolution imaging of the basin subsurface. Their structural and stratigraphic interpretation confirm the presence of local compressional features, such as reverse faults, thrust-related folds and synkinematic thinning of strata, within the Umiat Basin. The positive inversion process caused reactivation in terms of reverse faulting of some of the basement-rooted normal faults. The reverse reactivated normal fault producing the inversion anticline in the central zone of the seismic section exhibits a change in geometry from down-dip listric to up-dip anti-listric that is a typical geometry resulting from positive inversion. The presence of compressional structures testify that contractional reworking and inversion occurred within the Umiat Basin and it is likely related to distal compressional stresses transmitted through the basin.
Stili di inversione tettonica positiva plio-quaternari in Appennino Centro-Meridionale e in Avampaese Adriatico.Integrando dati geolgico-strutturali di superficie e di sottosuolo e stato ricostruito uno stile di inversione tettonica positiva simile sia nel settore frontale della catena Appennica Centro-Meridionale che nell'antistante avampaese Adriatico deformato (Dorsale Medio-Adriatica).Faglie normali pre-thrusting orientate N-S sono state riutilizzate come rampe oblique di sovrascorrimenti ad alto angolo durante la deformazione compressiva, sia nel settore di catena che nell'area di avampaese. Nella catena appenninica, inoltre, i tratti a direzione NW-SE di tali faglie normali sono stati dislocati con traiettorie di short-cut da sovrascorrimenti in rampa frontale.
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