Using UAV-Based Photogrammetry Coupled with In Situ Fieldwork and U-Pb Geochronology to Decipher Multi-Phase Deformation Processes: A Case Study from Sarclet, Inner Moray Firth Basin, UK

Constraining the age of formation and repeated movements along fault arrays in superimposed rift basins helps us to better unravel the kinematic history as well as the role of inherited structures in basin evolution. The Inner Moray Firth Basin (IMFB, western North Sea) overlies rocks of the Caledonian basement, the pre-existing Devonian–Carboniferous Orcadian Basin, and a regionally developed Permo–Triassic North Sea basin system. IMFB rifting occurred mainly in the Upper Jurassic–Lower Cretaceous. The rift basin then experienced further regional tilting, uplift and fault reactivation during the Cenozoic. The Devonian successions exposed onshore along the northwestern coast of IMFB and the southeastern onshore exposures of the Orcadian Basin at Sarclet preserve a variety of fault orientations and structures. Their timing and relationship to the structural development of the wider Orcadian and IMFB are poorly understood. In this study, drone airborne optical images are used to create high-resolution 3D digital outcrops. Analyses of these images are then coupled with detailed field observations and U-Pb geochronology of syn-faulting mineralised veins in order to constrain the orientations and absolute timing of fault populations and decipher the kinematic history of the area. In addition, the findings help to better identify deformation structures associated with earlier basin-forming events. This holistic approach helped identify and characterise multiple deformation events, including the Late Carboniferous inversion of Devonian rifting structures, Permian minor fracturing, Late Jurassic–Early Cretaceous rifting and Cenozoic reactivation and local inversion. We were also able to isolate characteristic structures, fault kinematics, fault rock developments and associated mineralisation types related to these event

Structures Related to the Emplacement of Shallow-Level Intrusions

A systematic view of the vast nomenclature used to describe the structures of shallow-level intrusions is presented here. Structures are organised in four main groups, according to logical breaks in the timing of magma emplacement, independent of the scales of features: (1) Intrusion-related structures, formed as the magma is making space and then develops into its intrusion shape; (2) Magmatic flow-related structures, developed as magma moves with suspended crystals that are free to rotate; (3) Solid-state, flow-related structures that formed in portions of the intrusions affected by continuing flow of nearby magma, therefore considered to have a syn-magmatic, non-tectonic origin; (4) Thermal and fragmental structures, related to creation of space and impact on host materials. This scheme appears as a rational organisation, helpful in describing and interpreting the large variety of structures observed in shallow-level intrusions

Geology and evolution of fissure systems in fractured basement rocks, Calabria, southern Italy: implications for sub-unconformity reservoirs and aquifers

Basement-hosted fissure-fill networks in sub-unconformity settings are increasingly recognized globally and have the potential to act as important subsurface reservoirs and/or migration pathways for hydrocarbons, geothermal fluids and groundwater. We examine well-exposed fissures from exhumed crystalline upper Carboniferous basement rocks in southern Italy (Calabria) and describe their nature, origin and evolution. The basement rocks record the emplacement and exhumation of their plutonic protoliths. The evolution of these rocks includes their initial intrusion in the late Carboniferous, followed by veining, folding and rifting events, to eventual exhumation at the surface when fissuring occurred in the mid-Miocene. The fissure network hosts fossiliferous marine sediments, wall rock collapse breccias and limited mineralization with vuggy cavities. In the basement below the main erosional unconformity, fissure-fills form up to 50% by volume of the exposed rock. The fills are notably more porous (up to 15-25% matrix porosity) than the ultra-low-porosity (<1%) crystalline host rocks. We present field observations, palaeostress analyses of fault slickenlines and fracture topology analyses demonstrating that these exceptionally well-connected fissure networks are related to rifting and penetrated to depths of at least 150 m below the main Miocene erosion surface

Surface faulting of the April 6, 2009, Mw 6.3 L'Aquila earthquake in Central Italy

This paper documents the evidence of surface faulting associated to the April 6, 2009, moderate-sized earthquake (Mw 6.3) in the Central Apennines of Italy, that determined major damage to L'Aquila town and its surroundings. Coseismic surface ruptures were mapped for a minimum distance of 2.6 km along the Paganica Fault, a "minor" active fault, if compared with other faults nearby, that show more spectacular evidence of recent activity. SRL and MD parameters (2.6 km and 10 cm, respectively) are in good agreement with what expected for a magnitude 5.8 event in that tectonic environment. Although small, the coseismic vertical displacement determined significant damage to houses and infrastructures. The comparison with the past seismicity, especially the much stronger 1703 earthquake, and the evidence for activity of the other active faults, clearly show that the 2009 event cannot be taken as the reference event for assessing the seismic hazard of the region. Nevertheless, it point out once more the need to pay more attention to these moderate events, being relatively frequent in the whole Mediterranean region and potentially even more destructive than in the past, due to the expanding urban centers and infrastructures inside their epicentral regions