Timing and development of the Heise volcanic field, Snake River Plain, Idaho, western USA

Abstract

The Snake River Plain (SRP) developed over the last 16 Ma as a bimodal volcanic province in response to the southwest movement of the North American plate over a fi xed melting anomaly. Volcanism along the SRP is dominated by eruptions of explosive high-silica rhyolites and represents some of the largest eruptions known. Basaltic eruptions represent the fi nal stages of volcanism, forming a thin cap above voluminous rhyolitic deposits. Volcanism progressed, generally from west to east, along the plain episodically in successive volcanic fi elds comprised of nested caldera complexes with major caldera-forming eruptions within a particular fi eld separated by ca. 0.5-1 Ma, similar to, and in continuation with, the present-day Yellowstone Plateau volcanic fi eld. Passage of the North American plate over the melting anomaly at a particular point in time and space was accompanied by uplift, regional tectonism, massive explosive eruptions, and caldera subsidence, and followed by basaltic volcanism and general subsidence. The Heise volcanic fi eld in the eastern SRP, Idaho, represents an adjacent and slightly older fi eld immediately to the southwest of the Yellowstone Plateau volcanic fi eld. Five large-volume (>0.5 km 3) rhyolitic ignimbrites constitute a time-stratigraphic framework of late Miocene to early Pliocene volcanism for the study region. Field relations and high-precision 40 Ar/ 39 Ar age determinations establish that four of these regional ignimbrites were erupted from the Heise volcanic fi eld and form the framework of the Heise Group. These are the Blacktail Creek Tuff (6.62 ± 0.03 Ma), Walcott Tuff (6.27 ± 0.04 Ma), Conant Creek Tuff (5.51 ± 0.13 Ma), and Kilgore Tuff (4.45 ± 0.05 Ma; all errors reported at ± 2σ). The fi fth widespread ignimbrite in the region is the Arbon Valley Tuff Member of the Starlight Formation (10.21 ± 0.03 Ma), which erupted from a caldera source outside of the Heise volcanic fi eld. These results establish the Conant Creek Tuff as a distinct and widespread ignimbrite in the Heise volcanic fi eld, eliminating former confusion resulting from previous discordant K/Ar and fi ssion-track dates. New 40 Ar/ 39 Ar determinations, when combined with geochemical, lithologic, geophysical, and fi eld data, defi ne the volcanic and tectonic history of the Heise volcanic fi eld and surrounding areas. Volcanic units erupted from the Heise volcanic fi eld also provide temporal control for tectonic events associated with late Cenozoic extension in the Snake Range and with uplift of the Teton Range, Wyoming. In the Snake Range, movement of large (≥0.10 km 3) slide blocks of Mississippian limestone exposed 50 km to the east of the Heise fi eld occurred between 6.3 and 5.5 Ma and may have been catastrophically triggered by the caldera eruption of the 5.51 ± 0.13-Ma Conant Creek Tuff. This slide block movement of ~300 vertical meters indicates that the Snake Range had signifi cant relief by at least 5.5 Ma. In Jackson Hole, the distribution of outfl ow facies of the 4.45 ± 0.05-Ma Kilgore Tuff rel...

Correlation between basalt flows and radiochemical and chemical constituents in selected wells in the southwestern part of the Idaho National Laboratory, Idaho

“…Thermal disruption resulted in a time transgressive series of silicic volcanic fields, characterized by positive geoid anomalies, rhyolitic resurgent caldera eruptions, emplacement of a mid-crustal mafic sill, and subsidence with later basaltic plains magmatism (Braile and others, 1982;Anders and Sleep, 1992;Peng and Humphries, 1998;Rodgers and others, 2002;Shervais and others, 2006). The part of the ESRP now occupied by the INL was the site of resurgent caldera activity, including the Picabo volcanic field from 10.2 ± 0.06 million years ago (Ma) to 7.9 ± 0.4 Ma (Kellogg and others, 1994;McCurry and Hughes, 2006), and the Heise volcanic field from 7.05 ± 0.04 Ma to 4.43 ± 0.08 Ma (Pierce and Morgan, 1992;Pierce and others, 2002;Morgan and McIntosh, 2005;McCurry and Hughes, 2006).…”

A field trip guide to the petrology of Quaternary volcanism on the Yellowstone Plateau

“…An approximately 2.3 m.y. hiatus occurred between the last significant caldera-forming events, the 4.5 Ma Kilgore eruption (Wotzlaw and others, 2014) in the Heise volcanic field to the southwest (Morgan and McIntosh, 2005;Ellis and others, 2017a) and the initiation of volcanism at Yellowstone Plateau around 2.1 Ma. The first known eruption at Yellowstone Plateau produced the Snake River Butte, which is a small rhyolite dome located at the southeast margin of the Big Bend Ridge caldera (the caldera produced during the first caldera-forming eruption at Yellowstone).…”

“…At the base of the sequence is the gray-colored tuff of Wolverine Creek containing glassy pyroclasts of obsidian and pumice. Sanidines from the tuff of Wolverine Creek have yielded 40 Ar/ 39 Ar dates of 5.72±0.03 Ma (Anders and others, 2014) and 5.59±0.05 Ma (Morgan and McIntosh, 2005). The latter date recalculates to 5.67 Ma if the calibration factors of the former are used (Anders and others, 2014).…”

“…Lithic fragments of sandstone and volcanic rock are scattered through the tuff (Watts and others, 2011). The tuff of Kilgore was the youngest of the large explosive eruptions from Heise volcanic center, it covered an area of at least 20,000 km 2 across Idaho, Montana, and Wyoming (Morgan and McIntosh, 2005), and has yielded a (Bindeman and others, 2007;Watts and others, 2011). This volume is comparable to the largest supereruptions from the Yellowstone Plateau.…”

“…1, 2). Four Miocene-Pliocene caldera-forming eruptions occurred at the Heise center since ~6.7 Ma, resulting in a ~10,000 square kilometer (km 2 ) area of nested calderas, although much of the volcanic center is now buried by sediments and PleistoceneHolocene basalts of the SRP (Morgan and McIntosh, 2005). The youngest Heise units, sampled by drill cores, are dated at ~3.9 Ma (Watts and others, 2011;Ellis and others, 2017a).…”