Yeso Group

Yeso Group
Name	Yeso Group
Type	Group
Age	? (Permian–Triassic)
Period	Permian
Primary lithology	Sandstone, siltstone, shale
Other lithology	Gypsum, limestone, conglomerate
Named for	Yeso Mountains
Region	Southwestern United States
Country	United States

Yeso Group — The Yeso Group is a sequence of Permian to Triassic age continental and marginal marine strata exposed in the southwestern United States, notable for its layered sandstones, siltstones, and evaporites. The unit plays a significant role in regional correlations between New Mexico, Texas, and Arizona, and is important for understanding late Paleozoic tectonics, sedimentation on the western margin of the supercontinent Pangaea, and Permian paleoenvironments. It contains fossils and resources that link it to broader studies of the Permian–Triassic extinction event, basin evolution of the Ancestral Rocky Mountains, and basin-fill sequences adjacent to the Rio Grande rift precursors.

Geology and Stratigraphy

The Yeso succession overlies the Abo Formation and underlies strata correlated with the Glorieta Sandstone and younger Mesozoic units, forming part of the Permian stratigraphic framework of the San Juan Basin, Manzano Mountains, and surrounding provinces. Regional mapping ties the group into composite stratigraphic columns used in sections near Socorro, New Mexico, Las Vegas, New Mexico, and exposures along the Rio Grande corridor. Stratigraphic subdivision commonly recognizes members and beds that correlate with names used in field studies by stratigraphers working in the United States Geological Survey tradition and by researchers from the New Mexico Bureau of Geology and Mineral Resources.

Lithology and Sedimentology

Lithologic assemblages include cross-bedded quartz-rich sandstones, ripple-laminated siltstones, mudstones, interbedded evaporitic gypsum/anhydrite layers, and lensoidal carbonate beds that resemble facies described in research from the Permian Basin. Sedimentological features such as planar and trough cross-stratification, flaser bedding, desiccation cracks, and evaporite pseudomorphs indicate fluctuating salinity and episodic exposure comparable to facies seen in the Cutler Group and Bell Canyon Formation. Clast-supported conglomerates and pebble lag horizons occur locally where the group records proximal alluvial input linked to uplift along ancestral structures like the Hogback monocline.

Age and Paleontology

Biostratigraphic and chronostratigraphic data place the Yeso interval in the late Guadalupian to early Lopingian stages of the Permian with some correlations extending toward the Triassic boundary in isolated sections. Fossils recovered include trace fossils, ostracods, bivalves, and plant impressions that are compared with assemblages from the Zechstein Sea–age sequences of Europe and contemporaneous faunas from the Kaibab Formation. Ichnofossils assigned to vertebrate and invertebrate tracemakers provide paleoecological constraints used alongside palynological data and conodont occurrences correlated with collections curated by institutions such as the Smithsonian Institution and regional university collections.

Depositional Environment and Paleogeography

Sedimentary facies indicate deposition across a coastal plain to shallow epicontinental shelf setting influenced by cyclic transgression–regression events tied to Permian eustasy and regional tectonics related to the western margin of Pangaea. Interpretations invoke environments ranging from fluvial braidplain channels analogous to the Mancos Shale–proximal systems, tidal flats comparable to modern Wadden Sea analogues, to restricted lagoons and sabkha settings that promoted gypsum precipitation similar to models developed for the Sabkha facies in the Arabian Peninsula. Paleogeographic reconstructions place the unit within the paleolatitudinal belt that later hosted assemblages documented in the Siberian Basin and Gondwana margins, yielding data used in plate reconstructions by researchers involved with the Paleobiology Database community.

Economic Resources and Uses

The Yeso contains economically relevant gypsum and evaporite horizons exploited for industrial gypsum and mineralogical study similar to deposits mined in the Guadalajara region of Mexico and the Permian Basin evaporite mines. Permeable sandstone intervals serve as minor aquifers tapped by municipal wells in counties such as Doña Ana County, New Mexico and have been evaluated for groundwater storage analogous to studies of the Edwards Aquifer. Hydrocarbon exploration models have considered the group as potential reservoir and seal intervals in regional plays influenced by structural traps associated with the Laramide Orogeny and foreland-basin architecture analyzed by oil companies and government surveys.

History of Investigation and Naming

Early geologists mapping Permian rocks in the American Southwest, including field parties from the United States Geological Survey and academic geologists at University of New Mexico, first described and named component beds after topographic features such as the Yeso Mountains and nearby localities. Subsequent stratigraphic revisions and member-level redefinitions appeared in monographs authored by regional stratigraphers and published in professional venues like the Geological Society of America and state geological survey bulletins. Ongoing work by paleontologists and sedimentologists at institutions such as New Mexico State University and collaborative teams with the Bureau of Land Management continues to refine correlations, nomenclature, and basin-scale interpretations.

Category:Permian geology Category:Geologic groups of New Mexico Category:Geologic groups of Texas