A stratigraphic framework for the eastern Mogollon-Datil volcanic field based on paleomagnetism and high-precision 40Ar/39Ar dating of ignimbrites--A progress report
William C. McIntosh, John F. Sutter, Charles E. Chapin, Glenn R. Osburn, and James C. Ratte
A reliable stratigraphic framework for the Oligocene Mogollon–Datil volcanic field is being developed by correlating ignimbrites (ash-flow tuffs) using existing detailed mapping in conjunction with paleomagnetic measurements and high-precision Ar40/Ar39 dating of sanidine separates, which has a relative error of ±0.15 my or better.
Thirty-three ignimbrite units have been studied, of which at least 27 are stratigraphically distinct. Thus far, the stratigraphy and age of 14 of the units have been tightly constrained. The ages of these units fall into three eruptive intervals.
The early group of ignimbrites was erupted between 35.51 and 33.93 my. Well-dated ignimbrite units emplaced during this interval include Datil Well Tuff (35.51 my), Kneeling Nun Tuff (35.28 my), Tadpole Ridge Tuff (35.14 my), and Blue Canyon Tuff (33.93 my). Polarity of the Datil Well Tuff is normal, and the other three units are reversed. The normal-to-reversed polarity transition at about 35.4 my can be traced throughout many of the older exposed Oligocene sections in the Mogollon–Datil volcanic field.
The middle eruptive interval (<33.93 to >29.03 my) is represented by only one well-dated unit, the Hells Mesa Tuff (32.04 my). The 1.89 and 3.01 my long ignimbrite hiatuses respectively preceding and following the eruption of the Hells Mesa Tuff are well established for the Socorro area and may extend throughout the entire Mogollon–Datil volcanic field.
The late eruptive interval includes at least nine voluminous ignimbrites erupted in the 1.67 my interval between 29.03 and 27.36 my. These units, totaling at least 6,000 km', were erupted from calderas in both the Mogollon Mountains and Socorro areas. Well-dated ignimbrites emplaced during this interval include Davis Canyon Tuff (29.03 my), La Jencia Tuff (28.78 my), Vicks Peak Tuff (28.46 my), Shelley Peak Tuff (28.52 my), Bloodgood Canyon Tuff (28.36 my), tuff of Caronita Canyon (27.85 my), Lemitar Tuff (27.97 my), tuff of Triangle C Ranch (27.98 my), and South Canyon Tuff (27.36 my). Only three of these units (tuff of Caronita Canyon, Lemitar Tuff, and tuff of Triangle C Ranch) are normally magnetized. This normal-polarity interval may correlate with sea-floor normal anomaly 10, although the data is not yet sufficient to substantiate this
Taylor Creek Rhyolites have not been dated in this study, but some of the domes are tightly bracketed by stratigraphic correlation between the La Jencia and Bloodgood Canyon tuffs at 28.78 to 28.36 my.
- McIntosh, William C.; Sutter, John F.; Chapin, Charles E.; Osburn, Glenn R.; Ratte, James C., 1986, A stratigraphic framework for the eastern Mogollon-Datil volcanic field based on paleomagnetism and high-precision 40Ar/39Ar dating of ignimbrites--A progress report, in: Truth or Consequences region, Clemons, R. E.; King, W. E.; Mack, G. H., New Mexico Geological Society, Guidebook, 37th Field Conference, pp. 183-195.