Geologic map of the New Harmony quadrangle, Washington County, Utah (MP 95-2)

By: S. K. Grant

The New Harmony quadrangle lies between Cedar City and St. George, in southwest Utah. It is dominated by the eastern part of the Pine Valley Mountains, a complex mass of extrusive and intrusive latite-monzonite porphyry. Immediately east of the quadrangle is the north-trending Hurricane fault zone, which has influenced structural features in the map area. The oldest rocks are Jurassic in age. These rocks, together with Cretaceous rocks, are found in the deeply eroded southern part of the quadrangle. They have been deformed by the fold-and-thrust actions of the Late Cretaceous Sevier orogeny: A post-orogenic period of erosion beveled the area before deposition of the Claron Formation in early Tertiary time. Mid-Tertiary ash-flow tuffs may have covered the entire quadrangle before being deformed and removed by uplift and sliding due to the emplacement of the Pine Valley monzonite-Iatite rocks. Faulting related to horizontal extension occurred in several directions and in a systematic clockwise pattern during the late Cenozoic. During this time two episodes of basalt extrusion and three alluvial-fan depositional events are recognized. Younger alluvial and other surface processes completed the depositional activities in the Quaternary.

Other Information:
Published: 1995
Pages: 14 p.
Plates: 2 pl.
Scale: 1:24,000
Location: Washington County
Media Type: Paper Map