Application of lineament analysis in structural geology gained renewed interest when remote sensing data and technology became available through dedicated Earth observation satellites like Landsat in 1972. Lineament data have since been widely used in general structural investigations and resource and geohazard studies. The present contribution argues that lineament analysis remains a useful tool in structural geology research both at the regional and local scales. However, the traditional “lineament study” is only one of several methods. It is argued here that structural and lineament remote sensing studies can be separated into four distinct strategies or approaches. The general analyzing approach includes general structural analysis and identification of foliation patterns and composite structural units (mega-units). The general approach is routinely used by most geologists in preparation for field work, and it is argued that at least parts of this should be performed manually by staff who will participate in the field activity. We argue that this approach should be a cyclic process so that the lineament database is continuously revised by the integration of data acquired by field data and supplementary data sets, like geophysical geochronological data. To ensure that general geological (field) knowledge is not neglected, it is our experience that at least a part of this type of analysis should be performed manually. The statistical approach conforms with what most geologists would regard as “lineament analysis” and is based on statistical scrutiny of the available lineament data with the aim of identifying zones of an enhanced (or subdued) lineament density. It would commonly predict the general geometric characteristics and classification of individual lineaments or groups of lineaments. Due to efficiency, capacity, consistency of interpretation methods, interpretation and statistical handling, this interpretative approach may most conveniently be performed through the use of automatized methods, namely by applying algorithms for pattern recognition and machine learning. The focused and dynamic approaches focus on specified lineaments or faults and commonly include a full structural geological analysis and data acquired from field work. It is emphasized that geophysical (potential field) data should be utilized in lineament analysis wherever available in all approaches. Furthermore, great care should be taken in the construction of the database, which should be tailored for this kind of study. The database should have a 3D or even 4D capacity and be object-oriented and designed to absorb different (and even unforeseen) data types on all scales. It should also be designed to interface with shifting modeling tools and other databases. Studies of the Norwegian mainland have utilized most of these strategies in lineament studies on different scales. It is concluded that lineament studies have revealed fracture and fault systems and the geometric relations between them, which would have remained unknown without application of remote sensing data and lineament analysis.

The International Lithosphere Project deep reflection seismic survey in the Norwegian sector of the North Sea has been reprocessed, particularly focusing on the deep crust, the reflection Moho, and the upper mantle. The data display shifting reflection patterns of the crust and the upper mantle parallel to the eastern margin of the Viking Graben. In the upper crust, which is mainly seismically transparent by the processing techniques utilized here, large‐scale structural features like detachment shear zones and master faults can be identified. Several of the major onshore faults and shear zones match seismic features in the seismic lines. Many of these structures acted as extensional shear zones in the Devonian. The middle crust is of variable reflectivity, whereas the lower crust is generally strongly reflective and is particularly so in the southern domain. The reflection Moho is identified throughout the study area but is of variable character. The presence of a S(E) dipping structure (Hardanger Moho Offset) that displaces the Moho by approximately 10 km, extends deep into the mantle (below the 50 km line depth), is positioned where the shallower Hardangerfjord Shear Zone, which flattens on the level of the middle crust, is situated. The Hardangerfjord Shear Zone/Hardanger Moho Offset‐system coincides with change of the crustal thickness (depth to Moho), a change that also coincides with the transition from thin‐ to thick‐skinned Caledonian deformation. Intramantle reflections are common in the study area, some of which are interpreted as shear zones, whereas others most likely represent magmatic intrusions.

On Varanger Peninsula, the roughly NW–SE-trending Trollfjorden–Komagelva Fault Zone separates Neoproterozoic successions that accumulated in a shallow-marine platformal domain to the SW of the fault from deep-marine basinal to deltaic sediments to the NE. In Ediacaran time the fault scarp acted as a buttress in a period of basinal inversion during the top-to-the-SW, contractional Timanian orogeny. During the subsequent, top-to-the-SE to -ESE, polyphase Caledonian orogenesis the fault acted as a dextral strike-slip megafracture and lateral ramp. In the northeastern terrane, Timanian and Caledonian fold interference has produced several examples of double-folding and intersecting cleavages. In the southwestern terrane, the Lower Allochthon Gaissa Thrust Belt overlies the Parautochthon, below which a 45 km long deformation front has been mapped. Tectonic shortening within this frontal zone varies from top-to-the-SSE in the west to top-to-the-ESE in the east. Imbricate thrust sheets disrupt the succession in the northeastern terrane, below which a floor décollement is speculated to emerge as a frontal fault along a prominent footwall of the precursor fault that acted on the seabed in outermost Varangerfjorden. By use of potential field data, the Caledonian structures on Varanger can be followed to the north into the Barents Sea where the nappe pile in the pre-Carboniferous basement reaches a thickness of several kilometres. Thematic collection: This article is part of the Fold-and-thrust belts collection available at: https://www.lyellcollection.org/cc/fold-and-thrust-belts

The Loppa High area has been subject to several events of uplift and subsidence from the Late Paleozoic to Present. The driving mechanisms behind the vertical movements, however, are not fully understood. We propose that uplift and subsidence were influenced by the combination of density changes caused by metamorphic phase changes in a 90 × 140 km wide mafic lower crustal body below the Loppa High and local (rift-related) and far-field stress. Through a numerical modelling approach we analyse the tectonically induced variations in pressure and temperature in the lower crust, their influence on phase changes in the mafic body and the affiliated vertical movements. Results show that (1) densification of the mafic body caused by far-field compression associated with the late Triassic westward translation of Novaya Zemlya could cause surface subsidence, (2) heat and fluid influx provided by early Cretaceous rifting could trigger density reduction and surface uplift and (3) the present-day geometry of the Loppa High as observed in seismic data can be reproduced by combining the modelled effect of rift flank uplift and phase changes in the mafic body. Phase change-driven vertical movements may also have affected other structural highs in the western Barents Sea, including the Stappen High.

Field analysis shows that fault cores of brittle, extensional faults at a medium to mature stage of development are commonly dominated by lozenge-shaped horses (fault-core lenses) characterized by a variety of lithologies, including intact, mildly to strongly deformed country rock derived from the footwalls and hanging walls, various types of fault rocks of the protocatalasite and breccia series, breccia, fault gouge and clay smear. The lenses are sometimes stacked to form complex duplexes. These structures are commonly separated by high-strain zones of sheared cataclasite, and/or clay smear/clay gouge. The geometry and distribution of clay gouge in high-strain zones sometimes display evidence of intrusion, indicating high fluid pressure.Although the sizes of the horses vary over several orders of magnitude, they frequently display a length:thickness (a:c) ratio of between 1:4 and 1:15.The high-strain zones of fault rocks commonly constitute unbroken, 3D membranes that are likely to constrain fluid communication both across and along the fault zone.There are significant contrasts in fault core architecture that are probably related to processes associated with contrasting fluid pressure, strain intensity and strain hardening/strain softening. Faults associated with strain softening are characterized by less abundant brittle deformation products and are less likely to be conduits for fluid flow compared to those that are affected by strain hardening.