Abstract. The advent of large digital datasets from unmanned aerial vehicle (UAV) and satellite platforms now challenges our ability to extract information across multiple scales in a timely manner, often meaning that the full value of the data is not realised. Here we adapt a least-cost-path solver and specially tailored cost functions to rapidly interpolate structural features between manually defined control points in point cloud and raster datasets. We implement the method in the geographic information system QGIS and the point cloud and mesh processing software CloudCompare. Using these implementations, the method can be applied to a variety of three-dimensional (3-D) and two-dimensional (2-D) datasets, including high-resolution aerial imagery, digital outcrop models, digital elevation models (DEMs) and geophysical grids.We demonstrate the algorithm with four diverse applications in which we extract (1) joint and contact patterns in high-resolution orthophotographs, (2) fracture patterns in a dense 3-D point cloud, (3) earthquake surface ruptures of the Greendale Fault associated with the M w 7.1 Darfield earthquake (New Zealand) from high-resolution light detection and ranging (lidar) data, and (4) oceanic fracture zones from bathymetric data of the North Atlantic. The approach improves the consistency of the interpretation process while retaining expert guidance and achieves significant improvements (35-65 %) in digitisation time compared to traditional methods. Furthermore, it opens up new possibilities for data synthesis and can quantify the agreement between datasets and an interpretation.

Complex arrays of faults in extensional basins are potentially influenced by pre-existing zones of weakness in the underlying basement, such as faults, shear zones, foliation, and terrane boundaries. Separating the influence of such basement heterogeneities from far-field tectonics proves to be challenging, especially when the timing and character of deformation cannot be interpreted from seismic reflection data. Here we aim to determine the influence of basement heterogeneities on fault patterns in overlying cover rocks using interpretations of potential field geophysical data and outcrop-scale observations. We mapped >1 km to meter scale fractures in the western onshore Gippsland Basin of southeast Australia and its underlying basement.Overprinting relationships between fractures and mafic intrusions are used to determine the sequence of faulting and reactivation, beginning with initial Early Cretaceous rifting. Our interpretations are constrained by a new Early Cretaceous U-Pb zircon isotope dilution thermal ionization mass spectrometry age (116.04 ± 0.15 Ma) for an outcropping subvertical, NNW-SSE striking dolerite dike hosted in Lower Cretaceous Strzelecki Group sandstone. NW-SE to NNW-SSE striking dikes may have signaled the onset of Early Cretaceous rifting along the East Gondwana margin at ca. 105-100 Ma. Our results show that rift faults can be oblique to their expected orientation when pre-existing basement heterogeneities are present, and they are orthogonal to the extension direction where basement structures are less influential or absent. NE-SW to ENE-WSW trending Early Cretaceous rift-related normal faults traced on unmanned aerial vehicle orthophotos and digital aerial images of outcrops are strongly oblique to the inferred Early Cretaceous N-S to NNE-SSW regional extension direction. However, previously mapped rift-related faults in the offshore Gippsland Basin (to the east of the study area) trend E-W to WNW-ESE, consistent with the inferred regional extension direction. This discrepancy is attributed to the influence of NNE-SSW trending basement faults underneath the onshore part of the basin, which caused local re-orientation of the Early Cretaceous far-field stress above the basement during rifting. Two possible mechanisms for inheritance are discussed-reactivation of preexisting basement faults or local re-orientation of extension vectors. Multiple stages of extension with rotated extension vectors are not required to achieve non-parallel

Abstract. Two centuries ago William Smith produced the first geological map of England and Wales, an achievement that underlined the importance of mapping geological contacts and structures as perhaps the most fundamental skill set in earth science. The advent of large digital datasets from unmanned aerial vehicle (UAV) and satellite platforms now challenges our ability to extract information across multiple scales in a timely manner, often meaning that the full value of the data is not realised. Here we adapt a least-cost-path solver and specially tailored cost-functions to rapidly extract and measure structural features from point cloud and raster datasets. We implement the method in the geographic information system QGIS and the point cloud and mesh processing software CloudCompare. Using these implementations, the method can be applied to a variety of three-dimensional (3D) and two-dimensional (2D) datasets including high-resolution aerial imagery, virtual outcrop models, digital elevation models (DEMs) and geophysical grids. We demonstrate the algorithm with four diverse applications, where we extract: (1) joint and contact patterns in high-resolution orthophotographs; (2) fracture patterns in a dense 3D point cloud; (3) earthquake surface ruptures of the Greendale Fault associated with the Mw7.1 Darfield earthquake (New Zealand) from high-resolution light detection and ranging (LiDAR) data, and; (4) oceanic fracture zones from bathymetric data of the North Atlantic. The approach improves the objectivity and consistency of the interpretation process while retaining expert-guidance, and achieves significant improvements (35–65 %) in digitisation time compared to traditional methods. Furthermore, it opens up new possibilities for data synthesis and can quantify the agreement between datasets and an interpretation.

Reactivation of weak surfaces (e.g., foliation planes) in metamorphic basement rocks facilitates the nucleation of new faults along such pre-existing surfaces (Byerlee, 1978;Sibson, 1985). Hence, basement reactivation gives rise to extension-oblique, rift-related faults that nucleate on basement weaknesses and inherit the strike and dip direction of the basement fabric (Collanega et al., 2019;Phillips et al., 2016;Rotevatn et al., 2018). As a consequence, the similarity in orientation between pre-existing basement structures and new rift faults has often been interpreted as evidence of basement-influenced rifting, involving reactivation of the aforementioned basement structures (

Fracture systems are often geometrically invariant across a range of scales, but the impact of structural inheritance on this relationship is poorly understood. This paper shows how fracture orientations in sedimentary rocks vary at different scales when influenced by pre-rift basement structures. We use high-resolution unmanned aerial vehicle (UAV) orthophotos to map folds and fractures in the basement and cover rocks of the Gippsland Basin, southeast Australia. Outcrop-scale observations are compared with >1 km long faults previously interpreted from potential field data. We use length-coloured rose diagrams of fracture traces to compare trends in fracture orientations. Early Cretaceous syn-rift normal faults exhibit the same ENE-WSW trend at basin (>1 km) and outcrop (meters) scales. Pervasive outcropscale, subvertical, NNW-SSE striking joints record a subsequent regional shortening event, but at the basin scale this is only expressed as reverse reactivated ENE-WSW striking faults.Thus, fabrics and/or faults in the underlying basement exert significant control on the orientation of basin-scale fractures in the cover but appear to have limited influence on outcrop-scale fracture orientations. Our observations show that fracture systems influenced by structural inheritance are not scale-invariant, and that a proper understanding of structural architecture can only be achieved by analysing data that span multiple scales. INTRODUCTIONStructural inheritance can impact the location, shape, and orientation of entire rift systems