Volcanism and sedimentation along the western margin of the Rio Grande rift between caldera-forming eruptions of the Jemez Mountains volcanic field, north-central New Mexico, USA
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
- New Mexico Bureau of Geology and Mineral Resources, Socorro, NM (United States)
- Resources; Colorado State Univ., Fort Collins, CO (United States). Warner College of Natural, Geosciences Dept.
The Cerro Toledo Formation (CTF), a series of intracaldera rhyolitic dome complexes and their associated extracaldera tephras and epiclastic sedimentary deposits, records the dynamic interplay between volcanic, tectonic, and geomorphic processes that were occurring along the western margin of the Rio Grande rift between major caldera-forming eruptions of the Bandelier Tuff 1.65–1.26 Ma. The Alamo Canyon and Pueblo Canyon Members differ significantly despite deposition within a few kilometers of each other on the Pajarito Plateau. These differences highlight spatial distinctions in vent sources, eruptive styles, and depositional environments along the eastern side of the Jemez Mountains volcanic field during this ca. 400,000 year interval. Intercalated pyroclastic fall deposits and sandstones of the Pueblo Canyon Member reflect deposition with a basin. Thick Alamo Canyon Member deposits of block-and-ash-flow tuff and pyroclastic fall deposits fill a paleovalley carved into coarse grained sedimentary units reflecting deposition along the mountain front. Chemistry and ages of glass from fall deposits together with clast lithologies of sedimentary units, allow correlation of outcrops, subsurface units, and sources. Dates on pyroclastic fall deposits from Alamo Canyon record deep incision into the underlying Otowi Member in the southern part of the Pajarito Plateau within 100 k.y. of the Toledo caldera-forming eruption. Reconstruction of the CTF surface shows that this period of rapid incision was followed by aggradation where sediments largely filled pre-existing paleocanyons. Complex sequences within the upper portion of the Otowi Member in outcrop and in the subsurface record changes in the style of eruptive activity during the waning stages of the Toledo caldera-forming eruption.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE Office of Environmental Management (EM)
- DOE Contract Number:
- AC52-06NA25396
- OSTI ID:
- 1459627
- Report Number(s):
- LA-UR--16-26739
- Journal Information:
- Journal of Volcanology and Geothermal Research, Journal Name: Journal of Volcanology and Geothermal Research Vol. 327; ISSN 0377-0273
- Publisher:
- Elsevier
- Country of Publication:
- United States
- Language:
- English
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Cerro Toledo Rhyolite, Jemez Volcanic Field, New Mexico: {sup 40}Ar/{sup 39}Ar geochronology of eruptions between two caldera-forming events
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