The purpose of this report is to map and describe the geologic setting, structure, geologic hazards, and mineral resources of this 7.5-minute quadrangle located in the southeastern corner of La Plata County in southwestern Colorado. Dr. David Gonzales and undergraduate students, Katie Potter and Brian Turner, from Fort Lewis College initiated the field work and research on this project between March and August of 2005, completing the northern and eastern part of the quadrangle. Dr. Gonzales completed the mapping in the spring and summer of 2007. Dr. Gonzales was the principal mapper and author for this report, using maps and field notes generated by all three investigators. Digital ZIP/PDF download. OF-08-14D
From the Author’s Notes:
The Bayfield 7.5-minute quadrangle includes about 60 square miles of chiefly hilly terrain within the eastern part of La Plata County in southwestern Colorado. The west and east boundaries of the quadrangle lie at longitudes of 107° 37’ 30” W and 107° 30’ 00” W, respectively. The south margin of the map is at latitude 37° 07’ 30” N and the north margin is at latitude 37° 15’ 00” N. The city of Bayfield is located in the northwestern corner of the quadrangle. The Bayfield quadrangle lies near the transition of the east-central part of the Colorado Plateau physiographic province and western edge of the Southern Rocky Mountains (Hardwick and others, 2008). The elevation of the terrain in the mapping area varies from 6,500 ft above sea level in the Los Piños River valley to around 8,600 ft in the mountainous terrain on the east margin of the quadrangle. The Los Piños River, which drains much of the southeastern Needle Mountains, flows from north to south across the quadrangle.