New Mexico Bureau of Mines & Mineral Resources Bulletin 149 Field-trip guide to the geochronolgy of El Malpais National Monument and the Zuni-Bandera volcanic field, New Mexico

Cover

PREFACE

INTRODUTION

FIRST-DAY ROAD LOG

SECOND-DAY ROAD LOG

REFERENCES

COVER—Block diagram of the Zuni-Bandera volcanic field looking north toward Mount Tayloer. The lava flows are shown in tones of gray with the youngest flows being the darkest. Drawn by John Tubb of Los Alamos National Laboratory.

FIGURE 1—Map of Zuni-Bandera volcanic field showing field-guide stops.

FIGURE 2—El Tintero cinder cone is the source for the Bluewater flow. Cinders are being quarried at this site for use as road material. A late, stubby basalt flow from El Tintero can be seen in the foreground.

FIGURE 3—²³⁰Th/²³²Th versus ²³⁸U/²³²Th for the Bluewater flow from the Zuni-Bandera volcanic field on the Jemez lineament in New Mexico. The isochron, shown by the dashed line, gives a 2σ age of 79 ka + 40 ka/-30 ka.

FIGURE 4—This photo shows the ~3 ka McCartys flow overlying the older (110-128 ka) Laguna flow near the intersection of Interstate 40 and NM 117 about 6 mi east of Grants.

FIGURE 5a—Aerial photo of the eastern edge of McCartys flow. Stop 3 is near the center of the photo.

FIGURE 5b—This portion of the geologic map of Maxwell (1986) covers essentially the same area as the photograph in Fig. 5a.

FIGURE 6—Geologist Steven Reneau of the Los Alamos National Laboratory is collecting charcoal for ¹⁴C dating from the baked soil beneath McCartys flow.

FIGURE 7a—Aerial photo showing the numerous volcanic vents near Bandera Crater. Field-guide Stops 4, 5, and 6 are marked on the photo, as is the site where charcoal was collected beneath the Bandera scoria.

FIGURE 7b—This portion of the geologic map of Maxwell (1986) covers the area shown in Fig. 7a.

FIGURE 8—Aerial photo looking south toward Bandera Crater. Cerro Rendija is the low shield volcano in the background.

FIGURE 9—This map shows the geochronology sampling sites near Bandera Crater.

TABLE 1—Representative chemical compositions of dated basalts.

TABLE 2—K-Ar dates on second pulse basalts in the Zuni-Bandera volcanic field.

TABLE 3—Conventional K-Ar and ⁴⁰Ar/³⁹Ar dates for the Fence Lake flow and North Plains basalts.

TABLE 4—Summary of Zuni-Bandera volcanic-field stratigraphy.

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Unpublished geochemical and geochronological data provided by
Paul E. Damon Paul G. Drake Matthew T. Heizler A. William Laughlin William C. McIntosh Michael T. Murrell	Frank V. Perry Jane Poths Steven L. Reneau Muhammed Shafiqullah Kenneth Sims Giday WoldeGabriel
This work was performed under the auspices of the U.S. Department of Energy.

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