LIDAR AS A TOOL FOR LINEAMENT MAPPING AND REEVALUATION OF BEDROCK GEOLOGY: EXAMPLES FROM THE MOUNT MOOSILAUKE REGION OF THE WHITE MOUNTAIN NATIONAL FOREST, NEW HAMPSHIRE

The increased availability and reliability of meter and sub-meter resolution LiDAR has provided unprecedented opportunities to map features of bedrock geology in the last decade. Using ArcGIS and 2011-2012 LiDAR provided by the Natural Resources Conservation Service, this study remotely measured fractured bedrock lineaments and reevaluated the distribution and character of previously mapped bedrock units in the Mount Moosilauke region of the White Mountain National Forest, New Hampshire. The lineament measurements were checked against steeply-dipping fracture data collected in the field for the five major geologic units of the region. LiDAR hillshade maps with azimuths/altitudes of 315/45 and 45/45 produced the best images to view the predominately NE and NW striking geologic elements, respectively. The major bedrock units and the dominant joint sets, as collected at single, extensive, outcrops, include: 1) the Oliverian Plutonic Suite with two sets trending N to S and ENE to WSW: 2) the Ammonoosuc Volcanics with two sets trending ENE to WSW and NW to SE; 3) the Bethlehem Granodiorite with one set trending NE to SW; 4) the Kinsman Granodiorite with two sets trending NE to SW and WNW to ESE; and 5) the Littleton Formation with three sets trending N to S, NNW to SSE, and ENE to WSW. Correlations between field measured joint sets at single outcrops and remotely measured lineament sets were modest. However, most joint sets were detectable through the LiDAR lineament analyses. This suggests that LiDAR is an effective tool to evaluate the fractured bedrock lineament geometry of a large region and the correlation to field-measured joints is dependent on the number and location of outcrops measured. We also used the LiDAR to evaluate the accuracy of existing geologic maps as well as the LiDAR character of the bedrock units. For example, in LiDAR the Fitch Formation shows as a deeply furrowed trough, the Littleton Formation shows individual bedding planes, the previously mapped Hogsback thrust fault expresses well as a lineament but the position and complexity needs to be modified, and several features that we interpreted to be faults have been discovered. LiDAR has proved to be an extremely effective tool to study bedrock features and generates a list of many regions where targeted fieldwork should be done.