PRELIMINARY APPLICATION OF A UAV-BASED DIGITAL OUTCROP MODEL TO THE CAMBRIAN BRAIDPLAIN STRATIGRAPHY OF THE MIDDLE MEMBER WOOD CANYON FORMATION, MARBLE MOUNTAINS, CALIFORNIA, USA

Images from an unmanned aerial vehicle (UAV) survey conducted in the Marble Mountains, Mojave Desert, California have been used to build a digital outcrop model (DOM) used to investigate the ancient braidplain stratigraphy of the Cambrian middle member Wood Canyon Formation (mmWCF). The images cover a cliff face that is approximately perpendicular to the inferred paleocurrent direction of the fluvial stratigraphy, exposing channel cross-section geometries. Using PIX4D photogrammetry software, several thousand images from the UAV were stitched into a georeferenced DOM that covers approximately 16000 m²of mmWCF stratigraphy along strike. With Virtual Reality Geological Studio (VRGS; www.vrgeoscience.com) 3D visualization software, the DOM can be viewed, measured, and annotated with tools designed specifically for stratigraphic studies. The program can also be used to trace and map geological features.

Viewing the targeted outcrop using a DOM provides an unprecedented visual perspective that is complementary to surveying the area from the ground, where beds are difficult to trace because of fracture sets and steep topography. Tracing out beds, specifically channels, is crucial to studying pre-Devonian continental braidplains, where channels can be 100s of meters in width. The new aerial view reveals numerous channels and partial channels in the mmWCF, displaying the shallow, wide geometry expected in this depositional setting. Other sandstone beds appear tabular, and may represent channels with widths on the scale of a kilometer or more. Candidates for lateral accretion and convex-up bedforms are present within the stratigraphy. The variety of morphologies mapped on the DOM supports the diverse depositional nature of a pre-vegetated braidplain environment. Integrating multiple UAV surveys with field work to collect observations at different scales increases the usefulness of both methods. Following traditional field work and UAV survey of the mmWCF, and DOM analysis, additional trips will collect further measurements, including paleocurrent from cross-bedding and the orientations of architectural elements, not discernable from the DOM.