New Mexico Geological Society Annual Spring Meeting — Abstracts

Recent ⁴⁰Ar/³⁹Ar data obtained in the Raton-Clayton Volcanic Field has provided a concise record of the eruptive history and landscape evolution in the field. Previous workers have completed extensive field work in examining the petrology and the geochemistry of the field, but only a limited effort has been made to date the volcanic rocks. One use of the data was to follow the development of the volcanic field through time. 43 selective whote rock samples were analyzed by the ⁴⁰Ar/³⁹Ar geochronologic dating method. The results indicate that there are three phases of volcanic activity in the field. The Raton phase consists of activity from 8.77-7.52 Ma, with sporadic activity to 3.60 Ma, the Clayton phase lasting 3.51-2.24 Ma, and the Capulin phase from 1.68 Ma-30 Ka. Eruption activity at Sierra Grande overlaps the Raton and Clayton phases from 3.80-2.67 Ma. Each phase is characterized by differing petrology and geochemistry established from previous studies. Another application of the data was used to estimate the amount of erosion that has occurred in the volcanic field, especially in the western portion. This erosion represents continuous post-emplacement erosion around these flows, possibly due to intense precipitation events (Chapin, pers. comm.). Since the oldest flows are on top of the local mesas, by simply calculating the vertical distance of the flows from the current surface and the age of the flows, an erosional rate can be established. Erosion rates have been calculated that range from as high as 120 m/Ma at the Raton Pass to zero in the eastern portion of the field. This provides information which can be used in conjunction with other data to estimate the paleoclimatology of the region.