Northeastern Section - 49th Annual Meeting (23–25 March)

Paper No. 9
Presentation Time: 11:00 AM


HELD, Cameron A., Geology, Bates College, 435 Bates College, Lewiston, ME 04240 and EUSDEN Jr., J. Dykstra, Geology, Bates College, 44 Campus Avenue, Lewiston, ME 04240,

Recently, geomorphologic mapping techniques have undergone rapid developments as high-resolution ortho-imagery and digital elevation models augment traditional field-based surveying methods. Utilizing 2011-2012 LiDAR data, this project maps and classifies the geomorphology of the Swift River region of the White Mountains of New Hampshire. The bedrock is composed of Jurassic intrusions, dominated by the Conway and Osceola granites, and on the Northeast corner of the study area is a Jurassic ring dike complex. Wisconsinan glaciation produced streamlined till ridges and some depositional features which were subsequently modified by post-glacial fluvial processes and mass wasting events. LiDAR Hillshade maps with illuminations/elevations of 315/45 and 45/45 produced the best images to view the complexities of the landscape. Analysis of the bare ground LiDAR has allowed new landscape units to be recognized and mapped, including: 1) depositional and erosional floodplain fluvial features (approximately 15% of the study area); 2) stream incision features on sloping landscapes (average slope range of 18° - 40°); 3) glacially streamlined features (310° azimuth of orientation); 4) other glacial landforms such as eskers(?); 5) stoss and lee bedrock features (with dominant fracture orientations of 5°, 40°, and 130°); 6) and potential glacial melt water streams among others. Lineament analysis of the fractured bedrock using the methodology of Mabee et al. (1994), shows no variation between the Jurassic igneous units in the study area and a strong correlation to the field-measured joints in the same units created during the rifting of Pangea. However, there were several less prominent orientations that appeared in the LiDAR but were not fractures, and these are assumed to be of glacial origin. Further analysis of the landscape geomorphology focused on where the polygons overlapped using the intersect tool in ArcGIS to create areas of mixed landscape units (ex. overlap of glacial depositional and fluvial erosional polygons or overlap of fractured bedrock and glacial depositional regions). This study shows that LiDAR can be successfully used to map the bedrock and surficial landscape geomorphology of large, remote regions of land that were previously unable to be viewed due to the dense tree canopy.