A PRELIMINARY ANALYSIS OF TERRESTRIAL LIDAR FOR SEDIMENTOLOGICAL DESCRIPTION AND INTERPRETATION OF GLACIAL OUTWASH AND DEBRIS FLOWS: GRAND MESA, CO, USA

The use of LiDAR has expanded rapidly over the last ten years, as researchers have used LiDAR for various applications in the geosciences. For example, geomorphologists have used LiDAR to map temporal changes in slopes, volumetric changes on beaches, coral reefs, and burned surfaces after forest fires, to mention a few. From our search of the literature, unfortunately, it appears terrestrial LiDAR has been used very little in sedimentological work. Studying the Pleistocene deposits on and around Grand Mesa stimulated us to ask if terrestrial LiDAR can provide sufficient definition to be used to examine, describe, and interpret sedimentary facies at outcrop scale?

As the Pleistocene ice cap draping Grand Mesa melted, glacio-fluvial sediments intermixed with debris flows were deposited on the southern slopes of the mesa. Numerous outcrops appear between Cory and Poinia, which have been described by Brunk and Giardino. We used their initial fieldwork along with our own to compare traditional field-mapped deposits with those features appearing in the LiDAR imagery. We selected several outcrops to image; the most spatially extensive outcrop is exposed along highway 65 adjacent to Cory Grade and was imaged along with similar outcrops in the area. We used traditional sedimentological fieldwork to improve upon Brunk and Giardino’s descriptions and interpretations of outcrops to produce reference models for each outcrop. A millimeter scale fine-point mesh was created for each outcrop using the LIDAR from multiple angles to create 3D images combined with GigaPan^® ultra high-definition panoramic images. The LiDAR and GigaPan^® images were merged using ParaView^® software to create a 3D projection of the outcrop in an immersive environment. New descriptions and interpretations were completed using the 3D images and compared to the original descriptions. Preliminary analysis suggests that the proposed methods of LiDAR images combined with the GigaPan^® images provides sufficient definition and detail to undertake and produce a detailed stratigraphic model of the facies of the Grand Mesa. Refinement of the LiDAR techniques will provide a new, significant approach to mapping outcrop sedimentology.