11 Using Volcanic Deposits to Help Us Understand Volcanic and Magmatic Processes

This session invites presentations that leverage volcanic deposits to reconstruct magmatic and eruptive processes. We welcome contributions from field and experimental volcanology, petrology, geochemistry, thermodynamics, and fluid mechanics, ranging from the landform to nanoscale.

Sunday, 19 October 2025
8:00 AM - 12:00 PM
HBGCC, 217A

Mapping and Geochemistry of the Black Mountain-Santo Tomas Chain, Potrillo Volcanic Field, Southern New Mexico

Paper number: 11-4
Program: Technical Sessions
Time: 9:00 AM – 9:15 AM

Authors

Abstract

Black Mountain is the largest feature in the Black Mountain-Santo Tomas volcanic chain, located in the eastern Potrillo Volcanic Field (PVF) in southern New Mexico. The Black Mountain-Santo Tomas volcanic chain consists of monogenetic basalts related to the intracontinental Rio Grande rift (RGR). Previous studies of magma assembly and monogenetic volcanism within this intra-continental rift system focused on the central PVF, and only limited work on the eastern PVF has been done. This ~165 ka volcanic chain has at least five main eruptive centers along a south to north trend: Black Mountain, a cone north of Black Mountain, Little Black Mountain, San Miguel, and Santo Tomas, respectively.

Early maps of Black Mountain from the 1960s are difficult to reconcile due to aeolian sand cover and recent quarrying. New field mapping and geographic information systems (GIS) analysis identified four vents and six flows associated with Black Mountain, different from the five vents and six flows from previous maps. Each Black Mountain flow was identified from its height profile, made from National Agriculture Imagery Program (NAIP) images and 1m digital elevation model (DEM) overlays, and differences in the ΄a΄ā and pāhoehoe textures. This updated map will be vital to reconstruct the magmatic history of Black Mountain and assess the relationship between features within the eastern chain and the larger PVF.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-414727

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