Mark E. Stelten

• PhD, University of California, Davis
• Research Geologist at United States Geological Survey, Menlo Park, CA, USA

We present new sanidine ⁴⁰Ar/³⁹Ar ages and paleomagnetic data for pre- and post-caldera rhyolites from the second volcanic cycle of the Yellowstone Plateau volcanic field, which culminated in the caldera-forming eruption of the Mesa Falls Tuff at ca. 1.3Ma. These data allow for a detailed reconstruction of the eruptive history of the second volcani...

Injection of mantle-derived magmas into the Earth's crust provides the heat necessary to develop and maintain large silicic magmatic systems. However, the role of mantle-derived magmas in controlling the compositional evolution of large silicic systems remains poorly understood. Here we examine the role of mantle-derived magmas in the post-caldera...

We constrain the physical nature of the magma reservoir and the mechanisms of rhyolite generation at Yellowstone caldera via detailed characterization of zircon and sanidine crystals hosted in three rhyolites erupted during the (c. 170–70 ka) Central Plateau Member eruptive episode—the most recent post-caldera magmatism at Yellowstone. We present 2...

In the Salton Trough, CA, five rhyolite domes form the Salton Buttes: Mullet Island, Obsidian Butte, Rock Hill, and North and South Red Hills, from oldest to youngest. Results presented here include 40Ar/39Ar anorthoclase ages, 238U-230Th zircon crystallization ages, and comparison of remanent paleomagnetic directions with the secular variation cur...

The nature of compositional heterogeneity within large silicic magma bodies has important implications for how silicic reservoirs are assembled and evolve through time. We examine compositional heterogeneity in the youngest (~170 to 70 ka) post-caldera volcanism at Yellowstone caldera, the Central Plateau Member (CPM) rhyolites, as a case study. We...

We integrate new geochemical data with field relations, ³⁶ Cl surface-exposure ages, and paleomagnetic data to understand the petrogenesis and eruption duration of three young basaltic lava flows in northern Harrat Rahat, a distributed volcanic field in central-western Saudi Arabia. These lavas, collectively referred to as the Five Fingers, erupted...

The chronology of mafic eruptions and their temporal relation to rhyolitic volcanism in the Yellowstone Plateau volcanic field are poorly known, thereby limiting our understanding of the way(s) in which mafic magmatism drives rhyolitic activity. To address this, we measured 40Ar/39Ar eruption ages on 13 mafic samples collected from Henrys Fork Cald...

The Inland Pacific Northwest documents geologic processes from Proterozoic time to the Present. This volume presents field trips from the 2024 GSA Cordilleran and Rocky Mountain Joint Sections Meeting, exploring the genesis of bedrock in Idaho, Neoproterozoic development of supercontinents in Washington, Cambrian tectonic and biostratigraphic histo...

Widely separated basalt lava-flow outcrops in north-central Oregon, USA, expose products of a single eruptive episode. A Pliocene lava flow, here informally termed the Tetherow basalt, issued from vents near Redmond, in the Deschutes basin of Oregon, as a plains-forming basalt now exposed in continuous outcrops northward for 60 km. A similar basalt...

Recently active distributed volcanic fields (DVFs) can pose a variety of potential hazards: many DVFs are characterized by mafic scoria cones and localized lava flows, but eruptions can also be more felsic, explosive, and/or voluminous. The San Francisco Volcanic Field (SFVF) near Flagstaff, AZ is a DVF that has produced a variety of compositions a...

At least 28 rhyolitic lava flows, domes, and tuffs erupted within Yellowstone caldera following its formation 631 ka. Understanding the timing of intracaldera eruptions is essential for characterizing natural hazards posed by Yellowstone volcano. We present 40Ar/39Ar eruption ages for the Mallard Lake Member and Central Plateau Member of the Platea...

The evolution of strain in nascent continental plate boundaries commonly involves distributed deformation and transitions between different styles of deformation as the plate boundary matures. Distributed NW-striking faults, many with km-scale right-lateral separation, are prevalent near Blythe, California, and have been variably interpreted to hav...

The eight field trips in this volume, associated with GSA Connects 2021 held in Portland, Oregon, USA, reflect the rich and varied geological legacy of the Pacific Northwest. The western margin of North America has had a complex subduction and transform history throughout the Phanerozoic, building a collage of terranes. The terrain has been modifie...

Sanidine dating and magnetostratigraphy constrain the timing of integration of the lower Colorado River (southwestern United States and northern Mexico) with the evolving Gulf of California. The Colorado River arrived at Cottonwood Valley (Nevada and Arizona) after 5.24 Ma (during or after the Thvera subchron). The river reached the proto–Gulf of C...

In continental arcs, the exposure of primitive eruptive products at the surface is typically a result of rapid magmatic transfer through the crust. As a result, the initially primitive magma experiences minimal crustal residence and thus insignificant differentiation towards more evolved products. This rapid transfer of primitive magma through thic...

Harrat Rahat, one of several large, basalt-dominated volcanic fields in western Saudi Arabia, is a prime example of continental, intraplate volcanism. Excellent exposure makes this an outstanding site to investigate changing volcanic flux and composition through time. We present 93 40Ar/39Ar ages and six 36Cl surface-exposure ages for volcanic depo...

The 40Ar/39Ar dating method is among the most versatile of geochronometers, having the potential to date a broad variety of K-bearing materials spanning from the time of Earth’s formation into the historical realm. Measurements using modern noble-gas mass spectrometers are now producing 40Ar/39Ar dates with analytical uncertainties of ∼0.1%, thereb...

Ion‐microprobe ²⁰⁶Pb/²³⁸U geochronology and trace element geochemistry of the unpolished rims and sectioned interiors of zircons from Yellowstone caldera's oldest post‐caldera lavas provide insight into the magmatic system during the prelude and aftermath of the caldera‐forming Lava Creek supereruption. The post‐caldera lavas compose the Upper Basi...

The Mono Craters are an overlapping chain of at least 28 domes and coulees located south of Mono Lake, east central California, and represent the most recent eruptions of high-silica rhyolite magma in the Mono Lake-Long Valley volcanic region. Regionally widespread tephra fall deposits from the Mono Craters serve as important chronostratigraphic ma...

The Harrat Rahat volcanic field, located in the west-central part of the Kingdom of Saudi Arabia, is the largest of 15 harrats (Arabic for 'volcanic field') hosted within the Arabian plate. Harrat Rahat is 50 to 75 km wide (east-west) and 300 km long (north-south), covering an area of approximately 20,000 square kilometers and encompassing more tha...

The Harrat Rahat volcanic field, which is in the west-central part of the Kingdom of Saudi Arabia, is the largest of 15 harrats (Arabic for “volcanic field”) hosted within the Arabian plate (fig. 1). Harrat Rahat is 50 to 75 km wide (east-west) and 300 km long (north-south), covering an area of approximately 20,000 km2 and encompassing more than 90...

Mafic volcanic fields are widespread, but few have erupted in historic times, providing limited observations of the magnitudes, dynamics, and timescales of lava flow emplacement in these settings. To expand our knowledge of effusive mafic eruptions, we must evaluate solidified flows to discern syn-eruptive conditions. The Harrat Rahat volcanic fiel...

A fundamental goal of igneous petrology is to quantify the duration of time required to produce evolved magmas following influx of basalt into the crust. However, in many cases, complex field relations and/or the presence of a long-lived magmatic system make it difficult to assess how basaltic inputs relate to more evolved magmas, therefore, preclu...

The following statement was omitted from the acknowledgments section of the manuscript but is included now in accordance with U.S. Geological Survey policy. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

The youngest major caldera-forming event at Yellowstone was the ~ 630-ka eruption of the Lava Creek Tuff. The tuff as mapped consists of two major ignimbrite packages (members A and B), linked to widespread coeval fall deposits and formation of the Yellowstone Caldera. Subsequent activity included emplacement of numerous rhyolite flows and domes, a...

We present a detailed geologic investigation of Pleistocene to Holocene mafic volcanism within the northernmost part of the Harrat Rahat volcanic field, proximal to the city of Al-Madinah, Saudi Arabia. Our study area covers ~570 km², and encompasses lava flows, scoria cones, and shield volcanoes of 32 mapped eruptive units consisting of continenta...

Application of 238U–230Th disequilibrium dating of accessory minerals with contrasting stabilities and compositions can provide a unique perspective on magmatic evolution by placing the thermochemical evolution of magma within the framework of absolute time. Chevkinite, a Th-rich accessory mineral that occurs in peralkaline and metaluminous rhyolit...

We present sub-crystal-scale 238U–230Th zircon ages and 238U–230Th–226Ra plagioclase ages of bulk mineral separates from the Holocene (2.0–2.3ka) eruptions of the Rock Mesa (RM) and Devil's Hills (DH) rhyolites at South Sister volcano, Oregon. We link these age data with sub-crystal trace-element analyses of zircon and plagioclase to provide insigh...

We examine magma mixing and crystal exchange in a young magma reservoir by correlating sub-crystal-scale SIMS age, SIMS trace element, and LA-MC-ICPMS Hf-isotopic data from zircons in the coeval ca. 100ka, yet compositionally distinct rhyolites of the Solfatara Plateau flow (SPF) and Hayden Valley flow (HVF) at Yellowstone Caldera. The SPF and HVF...