MORPHOLOGIC ANALYSIS OF QUATERNARY CINDER CONES, POTRILLO VOLCANIC FIELD, NEW MEXICO

Over 100 cinder cones reside in the western Potrillo Volcanic Field, within the axis of the Rio Grande Rift in southern New Mexico.  ³He surface exposure dating and ⁴⁰Ar/³⁹Ar dating methods reveal the age of the volcanic field to be from 1 Ma to 20 ka years old.  ³He surface exposure dating of lava flows associated with cinder cones and current morphologic dating methods show a relationship between cinder cone slope degradation and age.  Previous studies investigating the morphology of Quaternary basaltic cinder cones in Hawaii, Mexico and Nevada conclude that cinder cone slope angle, which decreases with time, is a reliable age indicator.  New morphologic dating methods using digital topographic maps (DRGs) with digital elevation models (DEMs) in conjunction with Nash's diffusion equation model confirm this correlation.  Spatial analysis of cinder cone slope distribution reveals three distinct age groups.  Group 1 with slope angles ranging from 4 through 8 indicate an age of around 250 ka years old.  Group 2 with slope angles ranging from 10 to 16 reveal an age approximating 125 ka years old.  Group 3 with slope angles ranging from 17 to 23 average an age approximating 60 ka years old.  This new morphologic dating methods suggest that cinder cone formation in the Potrillo Volcanic Field may have occurred at different intervals and that the field may be currently developing new cinder cones.