Martijn Passchier, Janos Urai, Cees Passchier

Outcrop studies of fracture networks are important to understand such networks in the subsurface, but complete
maps of all fractures in large outcrops are rare due to limitations of outcrop and image resolution. We present the
first full-resolution UAV-based, Gigapixel dataset and DEM of the wave-cut Lilstock Benches in the southern Bristol Channel basin, a classic outcrop of layer-bound fracture networks in limestones. With this dataset, we mapped the patterns and age relationships of successive generations of joints in dm-thick limestone layers separated by claystone beds. Using well-defined interpretation criteria based on crosscutting relationships and joint length, up to eight generations of joints were mapped. Results show that joint geometry and interrelations are fully resolved in the whole outcrop. Different joint generations have unique characteristics in terms of shape, orientation, spatial distribution and cross-cutting relations. The presence of low-angle crossings and junctions of joints suggest periods of partial joint cementation and reactivation. The dataset and interpretations are proposed as a benchmark of a large scale, complete fracture network to test digital fracture network models.