Basaltic phreatomagmatic fissure at 71 Gulch Part 1: sediment magma mingling and eruptive behavior
- PDF / 8,107,825 Bytes
- 17 Pages / 595.276 x 790.866 pts Page_size
- 99 Downloads / 155 Views
RESEARCH ARTICLE
Basaltic phreatomagmatic fissure at 71 Gulch Part 1: sediment magma mingling and eruptive behavior K. L. Bennis 1
&
A. H. Graettinger 2
Received: 20 April 2020 / Accepted: 26 October 2020 # This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply 2020
Abstract 71 Gulch Volcano, located in the western Snake River Plain, southwestern Idaho (USA), was formed by a basaltic fissure eruption into Pliocene Lake Idaho. Deposits at and below the eruptive surface record the nature of explosive and nonexplosive sediment-magma and water-magma interactions. The paleoenvironment and the volcanic plumbing system of 71 Gulch eruption were reconstructed from a detailed study of the now-exposed eruptive and subsurface deposits. Estimated water levels during the eruption range from 1 to 53 m across the entire volcano based on the distribution of pillow lavas. Billowed dikes and fluidal peperites are two types of intrusive features found ≤ 12 m below the syn-eruptive surface that have similar continuous margins representing ductile behavior and emplacement into soft, deformable sediment. In comparison, tabular dikes and blocky peperites occur throughout 41 m thick of exposed deposits below the syn-eruptive surface. A conical, diatreme-like vent structure dominates the subsurface exposure, indicating excavation by phreatomagmatic explosions. Localized spatter within the main subsurface vent suggests temporary exclusion of water and thus a period of brief vent growth above the lake level. Evidence of sediment-magma mingling through blocky and fluidal peperites shows how differing subsurface depths impact the resulting mingling textures. Keywords Phreatomagmatism . Sediment-magma mingling . Fissure . Peperite . Billowed dikes . Idaho
Introduction Sediment-magma mingling can occur when rising magma interacts with surrounding unconsolidated sediment below the eruptive surface. Deposits recording this mingling are frequently found at sites that also experienced explosive phreatomagmatic eruptions (Zimanowski et al. 1991; Dvorak 1992; White 1996; Starostin et al. 2005; Befus et al. 2008; Amin and Valentine 2017; van Otterloo et al. 2018). The relative influence of conditions such as sediment componentry, sediment grain size, and magma rheology
Editorial responsibility: P-S. Ross * K. L. Bennis [email protected] 1
Global Volcanism Program, Smithsonian National Museum of Natural History, 10th St. & Constitution Ave. NW, Washington, D.C. 20560, USA
2
Department of Earth and Environmental Science, University of Missouri Kansas City, Kansas City, MO, USA
(Busby-Spera and White 1987; Dadd and Van Wagoner 2002; Martin and Németh 2007; Khalaf et al. 2015; Kwon and Gihm 2017), lithostatic pressure, and magma flux are still not well constrained. Studying eruptive and subsurface deposits from subaqueous eruptions better establishes the conditions that produce the spectrum of explosive and nonexplosive behavior through wet sediment-magma mingling processes. Field examp
Data Loading...
