1 Distributed volcanic fields of the southwestern U.S.

This session invites submissions from various disciplines (e.g., petrology, tectonics, geophysics, geochronology) that explore distributed volcanism in the southwestern U.S. Topics of interest include spatio-temporal trends, magma compositions, and mantle and/or crustal controls on volcanism.

Monday, 18 May 2026
8:00 AM - 12:00 PM
Alvarado A

Spatial analysis of volcanic vents in the Southwest Utah and its relationship to pre-existing normal faults

Paper number: 1-5
Program: Technical Sessions
Time: 9:20 AM – 9:40 AM

Authors

Abstract

The Southwest Utah Volcanic Field (SWUVF), located in the transition between the Colorado Plateau and Basin and Range provinces, hosts ~219 Quaternary vents expressed as isolated vents, alignments, and clusters. We use this field to assess the relationship between normal faults and vent location. We compiled vent coordinates and a regional fault database from the Utah Geological Survey and analyzed spatial patterns using Poisson nearest-neighbor (PNN) statistics, kernel density estimation, vent-fault distance distribution, vent alignment and fault orientations. The SWUVF defines a polygon hull area of            ~ 7,250 km² with a minimum-area enclosing ellipse trending N40°E, and an average vent density population of 3.02x10-2/km2. PNN analysis yields an observed mean nearest-neighbor distance (Mobs) of 1,886.82 m, an expected random mean (Mexp) of 3,032.0 m, and R = 0.62 (Mobs/Mexp), indicating significant clustering. Kernel density maps show multiple vent clusters that coincide with zones of closely spaced normal faults. The field is divided into two structurally distinct regions: a western sector characterized by N–S trending normal faults and an eastern sector dominated by NE–SW trending normal faults. Vent alignments in both sectors consistently parallel the orientation of the local normal faults. This structural partitioning coincides with the transition between the extensional Basin and Range–Transition Zone to the west and the Colorado Plateau to the east. A right-skewed distribution of vent-to-fault distances peaks within 0.25 km and shows that 57% of the vents lie within ~1 km of the nearest mapped fault. These results, together with the parallelism to sub parallelism of alignments to dominant normal-fault trends (N30°E and N5°E) are interpreted as an indicative of an important control on magma pathways and vent localization by pre-existing normal faults within this intraplate extensional setting. This is an example of how monogenetic volcanic fields provide sensitive records of upper-crustal magma transport, where vent positions may reflect the active stress field and pre-existing crustal structures.

Geological Society of America Abstracts with Programs. Vol. 58, No. 4

doi: 10.1130/abs/2026RM-410640

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