A contour map of the Precambrian surface for a part of northeastern New Mexico has been prepared from aeromagnetic, gravity, and drill-hole data. The area extends approximately from the Colorado border south to latitude 34° N., and from the foothills of the Sangre de Cristo Mountains east to longitude 104° W. Thirty-seven depths to Precambrian rocks were computed from aeromagnetic anomalies. Regional gravity anomalies were generally not suitable for quantitative analysis, but the gravity highs correlated with known areas of basement highs, providing a basis for contouring in areas of meager depth control. Drill-hole data provided 61 depths to basement in and near the survey area. The contouring along the east edge of the Sangre de Cristo Mountains was guided by exposures of Precambrian rocks. A principal feature of the contour map is the Sierre Grande Arch, a basement highland that trends southwest across the area to the northwest part of Guadalupe County. Major depressions are outlined west of Vegas Junction, northeast of Santa Rosa, and north and northeast of Las Vegas. The largest of these, the Las Vegas basin, occupies more than 1,000 square miles and may be more than 10,000 ft deep
XVII.—Contributions from the New Mexico biological station.—X. Observations on bees collected at Las Vegas, New Mexico, and in the adjacent mountains. II