INCORPORATING DIGITAL IMAGING TECHNIQUES INTO OUTCROP INVESTIGATIONS OF ALASKA’S NORTH SLOPE STRATIGRAPHY

Gil Mull, an Arctic Alaska geology expert and accomplished photographer, understood the value and power of a well-composed photograph, interpreted outcrop imagery, and the marriage of geology and photography. Advances in digital imaging and processing techniques offer new opportunities for geologists to photographically document remote, restricted, difficult to access, steep, and/or laterally extensive outcrops that provide key windows into the regional stratigraphy, structure, and tectonics. Digital imagery can effectively bring an outcrop “back to the office” permitting re-examination of geologic relations and otherwise inaccessible details, and refining and communicating interpretations. Structure from motion (SfM) and high-resolution photomosaic surveys can be implemented and ground truthed during fieldwork, providing unique access to mountain-scale to outcrop-scale features (e.g., systems tracts, stratal stacking, architectural elements), and bed-scale and smaller elements (e.g., sedimentary structures, ichnology), placing key characteristics within a broader context.

North Slope outcrops are valuable to academia, government agencies, and the petroleum industry, providing insights into basin dynamics, the spatial-temporal evolution of high-latitude depositional systems, and analogs for subsurface reservoirs-seals for geomodelling. We present examples of classic and newly investigated North Slope outcrops to showcase the benefits of incorporating drone-based SfM photogrammetry and high-resolution photomosaics (GigaPan imagery) into outcrop investigations. The images permit 1) identification of architectural elements and stratal stacking in 3D space; 2) recognition and tracing key litho- and sequence-stratigraphic surfaces; 3) paleohorizontal reconstructions of structurally tilted beds; 4) imaging of inaccessible or unsafe outcrops; 5) preserving classic and/or unstable outcrops for posterity; and 6) providing remote access for individuals who may not have the ability or means to visit these outcrops. Examples from the Schrader Bluff and Nanushuk formations along the Colville and Nanushuk rivers and at Slope Mountain are discussed. We suggest that Alaska’s geologic photograph repositories should be capable of hosting SfM and photomosaic outcrop imagery.