Rio Chama Country

About this guidebook

The Eleventh Annual Field Conference of the New Mexico Geological Society will investigate the general geology of parts of three rather distinct structural provinces, the great Rio Grande structural trough, or complex graben, the southwestern prong of the Rocky Mountain System, and the marginal areas of the Colorado Plateaus. The first day of the field conference deals principally with two of these provinces, namely, the Rio Grande trough and the Brazos uplift, which are a part of the Rocky Mountain System. The remainder of the trip will be in and adjacent to the Rio Chama country, most of which is situated in areas in or marginal to the Colorado Plateaus. The town of Taos is on the margin of the Rio Grande trough. To the east are the rugged Sangre de Cristo Mountains, the segment adjacent to Taos sometimes being referred to as the Wheeler Range. To the west, and along the route of the conference during the first few hours of the trip, is the lava capped Taos Plateau within the Rio Grande trough. The Rio Grande has cut a deep gorge into Cenozoic rocks in this part of the trough and the numerous flows and associated sediments will be visible at the crossing of the Rio Grande near Taos Junction. West of the river the conference will cross a great lava plain and then will skirt the Tusas Mountains, which define the western margin of the Rio Grande structural trough and are a part of the southwestern lobe of the Rocky Mountains. Rather late on the first day of the trip the caravan will descend into the area variously referred to in this Guidebook as the Chama platform and the Chama basin. The editorial staff prefers to be neutral, hence the name Rio Chama country. The remainder of the trip, embracing the second and third days of the conference, will be in and adjacent to this country where rocks ranging in age from Precambrian to Cenozoic will be viewed closely or from a distance. The structure of the Rio Chama country, which is believed by some to be quite complex and by others to be relatively simple, should be a major topic of discussion at many of the stops. At other stops the main interests will be in the stratigraphic sequences and their lateral variations. Although immediately adjacent to the San Juan Basin, one of the larger subdivisions of the Colorado Plateaus and one of the great petroleum provinces of the Southwest, th e Chama River country has lagged behind in resources development. Although known for many years to contain some commercial pools, exploration until very recently has been fraught with disappointments. Apparently at least some of the keys to discovery have now been found, and it would appear that the Chama River country is coming into its own.