24 Tectonics, Volcanism, and Sediment Dispersal Within and Proximal to the Rio Grande Rift and Southern Rocky Mountains (Posters)

This session integrates research on coupled tectonics, volcanism, and sediment dispersal in the Rio Grande Rift and southern Rockies. We examine how extensional faulting controls volcanic processes and reshapes sediment routing from Colorado through Texas.

Tuesday, 19 May 2026
8:00 AM - 5:30 PM
Alvarado D/E

Hard Rock, Long Journey: Quartzite and Fluvial Pathways in the Miocene Ogallala of the Southern High Plains

Paper number: 24-1
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

Quartzite cobble and pebble analysis of the Miocene–Pliocene Ogallala Formation in western Texas and eastern New Mexico reveals the evolution of regional drainage systems sourced from the southern Rocky Mountains. Petrographic analysis of quartzite clasts documents variable metamorphic grades and textures, indicating derivation from multiple metamorphic terranes with distinct histories. Lithographic types include the following such as sillimanite-andalusite-bearing quartzite, sillimanite-only bearing quartzite, kyanite, garnet-bearing quartzite, granoblastic quartzite, sheared quartzite, and meta-sandstone. Many of these lithotypes are characteristic of high- to medium-grade metamorphic terranes exposed in the Picuris and Sangre de Cristo Mountains of northern New Mexico and the Los Pinos Mountains in central New Mexico. This distinctive quartzite assemblage, confirms that the dominant paleodrainage network originated from headwaters in northern and central New Mexico rather than from southern sources. This provenance signature documents major reorganization of Miocene–Pliocene drainage systems, including shifts in trunk river courses and systematic channel migration. Future work will integrate additional sampling from central southern Rocky Mountain source areas and central Ogallala outcrops to reconstruct detailed paleodrainage pathways and temporal changes in sediment routing. These data will provide critical constraints on the timing and mechanisms of Cenozoic landscape evolution in the southern Great Plains, including the development of the regionally extensive aggradational surfaces that characterize this portion of the Ogallala aquifer system.

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

doi: 10.1130/abs/2026RM-410503

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