Chronology of Young Basalt Flows from Lava Tube Gypsum U-series Ages

Authors

Victor J. Polyak, University of New MexicoFollow
Julian R. Dillon
Yemane Asmerom, University of New MexicoFollow
Bogdan P. Onac, University of South FloridaFollow

Document Type

Article

Publication Date

8-2020

Keywords

Lave tube cave, Gypsum, U-series, El malpais, Isotope

Digital Object Identifier (DOI)

https://doi.org/10.1016/j.quageo.2020.101083

Abstract

Basaltic lavas provide a window into their mantle sources and the associated geodynamic processes associated with them. Obtaining absolute chronology on young basalt flows is often challenging. Some gypsum crusts in pyro-duct (lava tube) caves crystallize during the last “cooling” stages of tube formation probably at relatively low temperatures (i.e., <100 °C). Here we propose uranium-series dating of these ‘speleogenetic’ gypsum crusts as a way to establish the ages of young basalt flows. We demonstrate the technique using cave crusts from four young basalt flows in El Malpais National Monument, New Mexico, three of which are moderately well-dated by alternative methods (¹⁴C, ³⁶Cl, and ³He ages). They all exhibit well-formed lava tube systems that contain gypsum crust speleothems interpreted to be remnant of the volcanic sulfur or sulfate processes when the tube systems were active during their terminal stages. δ¹⁸O_SO4, δ³⁴S, ⁸⁷Sr/⁸⁶Sr, and δ²³⁴U values for the gypsum crusts have near-basaltic signatures, and the crusts contain uranium concentrations suitable for uranium-series dating in three of these four basalt flows. Analyses of gypsum from caves of two well-dated basalt flows yielded uranium-series ages that agree with the ages determined by other techniques showing that absolute ages of young basalt flows can be achieved by this method. The fourth flow, the Hoya de Cibola basalt, previously undated by other absolute means has a U–Th gypsum crust isochron age of 16.9 ± 0.9 ka. The uranium-series age and isotopic analyses of these gypsum crusts should be useful in geologic applications involving young basalt flows.

Was this content written or created while at USF?

Yes

Citation / Publisher Attribution

Quaternary Geochronology, v. 59, art. 101083

Scholar Commons Citation

Polyak, Victor J.; Dillon, Julian R.; Asmerom, Yemane; and Onac, Bogdan P., "Chronology of Young Basalt Flows from Lava Tube Gypsum U-series Ages" (2020). School of Geosciences Faculty and Staff Publications. 2299.
https://digitalcommons.usf.edu/geo_facpub/2299