Geology topics

Judith E. Fierstein

Publications and source records attributed to Judith E. Fierstein.

12 recordsLinked to original sources

USGS2024

Two-million-year eruptive history of Laguna del Maule volcanic field

The Laguna del Maule (LdM) volcanic field, which surrounds the 54-km 2 lake of that name, covers ∼500 km 2 of mountainous glaciated terrain with Quaternary lavas and tuffs that extend 40 km westward from the Argentine frontier and 30 km north-south from the Río Campanario to Laguna Fea. Complementing recent investigations of postglacial volcanism and the ongoing geophysical unrest around the lake, we here review the longer eruptive history that spanned the entire Quaternary.

Journal of South American Earth Sciences↗

USGS2023

Ages of the granitic basement of Long Valley Caldera, California, USA, and siting of the Quaternary granite-rhyolite pluton

The leucogranitic crystal-mush pluton beneath the iconic Long Valley Caldera, California, USA, released >820 km 3 of crystal-poor Pleistocene rhyolite, which was hosted by numerous Mesozoic granitic plutons, only a few of which had been dated until now. Reported here are U-Pb zircon ages, determined by sensitive high-resolution ion microprobe−reverse geometry (SHRIMP-RG), for 11 circumcaldera granitoids, all of them either Triassic or Cretaceous. Growth of the 35-km-wide Quaternary rhyolite-leucogranite plutonic reservoir was fostered by collocation of (1) a dense swath of late Pliocene basaltic vents, (2) a left-stepping extensional reentrant in the rangefront fault zone of the Sierra Nevada batholith, and (3) a sharp offset of the Proterozoic continental margin as represented by the Sr-isotope 0.706 line. We further consider whether the basement architecture of as many as 26 separate Triassic and Cretaceous plutons and intervening septa and pendants of Paleozoic metasedimentary rocks influenced siting of the Quaternary pluton and whether the ragged margin of Proterozoic lithosphere helped to focus asthenospheric edge upwelling that intensified crustal melting and intrusion in both the Triassic and the Quaternary.

California↗

USGS2023

Precaldera mafic magmatism at Long Valley, California: Magma-tectonic siting and incubation of the Great Rhyolite System

The iconic volcanic center at Long Valley has released ∼820 km 3 of rhyolite in at least 110 eruptions. From 2.2 Ma until 0.23 Ma, products were exclusively rhyolitic, and ∼ 700 km 3 were high-silica rhyolite severely depleted in Sr, Ba, and Eu. The rhyolitic interval was preceded by an interval from 3.9 to 2.6 Ma with numerous basalt-andesite-dacite eruptions accompanied by no rhyolite at all. We have now mapped the circumcaldera products of this interval, defined 107 eruptive units, characterized them all chemically and petrographically, and dated many by 40 Ar/ 39 Ar. Here we display and describe them by sector around the caldera, interpret the nature of the transcrustal magma system that eventuated in the 35-km-wide Long Valley granite-rhyolite pluton, and analyze regional tectonic factors that did or did not contribute to siting the system. Nine Miocene (12–6 Ma) eruptive units close to Long Valley were followed by a Pliocene flare-up that released >300 mafic eruptions in a SW–NE swath 170 km long, centered across the later site of Long Valley. The basalts and their fractionates are intraplate alkalic products dominated by a continental lithosphere that had long been fluxed by Mesozoic subduction. Tertiary arc volcanism had not impinged on the area of Long Valley. Volumes estimated for the 107 Neogene precaldera eruptive units (only 40 of which exceeded 0.1 km 3 ) total ∼ 27 km 3 ± 50%—only ∼3% of the subsequent volume of rhyolite erupted. Such a volume of high-silica rhyolite with ultra-low Sr and Eu is not a product of partial melting but requires as proximate parent a leucogranitic crystal mush that is itself the upper level of a long-lived plutonic reservoir that extends to the lower crust. The 27 km 3 of Neogene magma that erupted was a small contingent of the mantle-derived basaltic flux needed to energize (and contribute its fractionated melt to) a 30-km-deep compositionally graded crustal column, which culminated in ∼10,000 km 3 of granitoid mush from which 820 km 3 of Quaternary high-silica rhyolitic melt escaped and erupted. Pliocene basaltic eruptions ceased at ∼2.6 Ma, probably because the basaltic flux intensified sufficiently to render the mushy upper crust impenetrable. The 2.6–2.2 Ma quiescent interval represented culmination of thermal activation of the plutonic column and refinement of its leucogranitic mushy upper layer, from which extreme melts escaped for the next 2 Myr. The Pliocene mafic swath crosses the Sierran rangefront fault zone coincident with a left-stepping extensional reentrant that also began developing at ∼3 Ma. Moreover, Long Valley overlies a dextral offset in the initial Sr-isotope 0.706 line, which may reflect the rifted or attenuated edge of Proterozoic crust and mantle lithosphere. Concatenation of these three influences may account for siting of intensified edge-focused magmatism that produced the great Quaternary pluton.

California↗

USGS2022

Lateral extent of pyroclastic surge deposits at Ubehebe Crater (Death Valley, CA) and implications for hazards in monogenetic volcanic fields

Hazard assessments in monogenetic volcanic fields require estimates of the runout of pyroclastic surges that result from phreatomagmatic explosive activity. Previous assessments used runout distances of 1-4 km, with large cases up to 6 km. Surge deposits at Ubehebe Crater (~2100 y.b.p., Death Valley, California) have been traced ~9 km from the crater center, and likely originally extended 1-3 km farther. There is no evidence that the Ubehebe Crater activity was unusually energetic; rather, its distal deposits are better preserved than those at most maar volcanoes because of its young age and the arid environment. Numerical simulations illustrate how long runout is facilitated by low temperatures of phreatomagmatic surges due to reduced expansion of entrained air compared to hot surges, allowing cool surges to retain higher densities than ambient air. We suggest that hazard assessments for volcanic fields with phreatomagmatic, maar-forming eruptions should consider runout distances in the range of 10-15 km.

California↗

USGS2022

Pyroclastic deposits of Ubehebe Crater, Death Valley, California, USA: Ballistics, pyroclastic surges, and dry granular flows

We describe and interpret deposits associated with the final Ubehebe Crater-forming, phreatomagmatic explosive phase of the multivent, monogenetic Ubehebe volcanic center. Ubehebe volcano is located in Death Valley, California, USA. Pyroclastic deposits occur in four main facies: (1) lapilli- and blockdominated beds, (2) thinly bedded lapilli tuff, (3) laminated and cross-laminated ash, and (4) massive lapilli ash/tuff. Lapilli- and block-dominated beds are found mostly within several hundred meters of the crater and transition outward into discontinuous lenses of lapilli and blocks; they are interpreted to have been deposited by ballistic processes associated with crater-forming explosions. Thinly bedded lapilli tuff is found mainly within several hundred meters, and laminated and cross-laminated ash extends at least 9 km from the crater center. Dune forms are common within ~2 km of the crater center, while finer-grained, distal deposits tend to exhibit planar lamination. These two facies (thinly bedded lapilli tuff and laminated and cross-laminated ash) are interpreted to record multiple pyroclastic surges (dilute pyroclastic currents). Repeated couplets of coarse layers overlain by finer-grained, laminated horizons suggest that many or most of the surges were transient, likely recording individual explosions, and they traveled over complex topography in some areas. These two factors complicate the application of classical sediment-transport theory to quantify surge properties. However, dune-form data provide possible constraints on the relationships between suspended load sedimentation and bed-load transport that are consistent using two independent approaches. Massive lapilli ash/tuff beds occur in drainages below steep slopes and can extend up to ~1 km onto adjacent valley floors beneath large catchments. Although they are massive in texture, their grain-size characteristics are shared with laminated and cross-laminated ash facies, with which they are locally interbedded. These are interpreted to record concentrated granular flows sourced by remobilized pyroclastic surge deposits, either during surge transport or shortly after, while the surge deposits retained their elevated initial pore-gas pressures. Although similar surge-derived concentrated flows have been described elsewhere (e.g., Mount St. Helens, Washington, USA, and Soufriére Hills, Montserrat, West Indies), to our knowledge Ubehebe is the first case where such processes have been identified at a maar volcano. These concentrated flows followed paths that were independent of the pyroclastic surges and represent a potential hazard at similar maar volcanoes in areas with complex terrain.

California↗

USGS2020

Soft sediment deformation in dry pyroclastic deposits at Ubehebe Crater, Death Valley, California

Soft sediment deformation structures are common in fine-grained pyroclastic deposits and are often taken, along with other characteristics, to indicate that deposits were emplaced in a wet and cohesive state. At Ubehebe Crater (Death Valley, California, USA), deposits were emplaced by multiple explosions, both directly from pyroclastic surges and by rapid remobilization of fresh, fine-ash-rich deposits off steep slopes as local granular flows. With the exception of the soft sediment deformation structures themselves, there is no evidence of wet deposition. We conclude that deformation was a result of destabilization of fresh, fine-grained deposits with elevated pore-gas pressure and dry cohesive forces. Soft sediment deformation alone is not sufficient to determine whether parent pyroclastic surges contained liquid water and caused wet deposition of strata.

California↗

USGS2020

The remarkable volcanism of Shastina, a stratocone segment of Mount Shasta, California

Mount Shasta, a 400 km 3 volcano in northern California (United States), is the most voluminous stratocone of the Cascade arc. Most Mount Shasta lavas vented at or near the present summit; relatively smaller volumes erupted from scattered vents on the volcano’s flanks. An apron of pyroclastic and debris flows surrounds it. Shastina, a large and distinct cone on the west side of Mount Shasta, represents a brief but exceptionally vigorous period of eruptive activity. Its volume of ∼13.5 km 3 would make Shastina itself one of the larger Holocene Cascade stratovolcanoes. Its andesite-dacite lavas average 63 wt% SiO 2 and have little compositional or petrographic variation; they erupted almost entirely from one central vent, although a single vent below Shastina’s north side erupted a flow of the same composition. Eruptions ended with explosive enlargement and breaching of the central crater and successive emplacement of four, more-silicic dacite domes within the crater and pyroclastic flows down its flank. Black Butte, a large volcanic dome and pyroclastic complex below the west flank of Shastina, is petrographically and chemically distinct but only slightly younger than Shastina itself, part of a nearly continuous Shastina–Black Butte eruptive episode. Shastina overlies the widespread pumice of Red Banks, erupted from the Mount Shasta summit area and 14 C dated at ca. 10,900 yr B.P. (calibrated). Shastina and Black Butte pyroclastic deposits have calibrated 14 C ages indistinguishable from one another at ca. 10,700 cal. yr B.P. A cognate granitic-textured inclusion in a late Shastina lava flow yields a 238 U- 230 Th date on zircons within error of those ages. Our conclusion that the entire, voluminous Shastina–Black Butte episode lasted no more than a few hundred years is confirmed by almost identical remanent magnetic directions of all of the lavas and pyroclastic deposits. Although extremely similar, the remanent magnetic directions do reveal a short path of secular variation through the eruptive sequence. We conclude that the entire Shastina–Black Butte eruptive episode lasted no more than ∼200 yr. The magmas that produced the Shastina and Black Butte eruptions were separate individual bodies at different crustal levels. Each of these eruptive sequences probably represents magma approximating a liquid composition that experienced only minimal differentiation or crustal contamination and remained separated from the main central conduit for most eruptions of Mount Shasta. The probability of another rapidly developing, brief but voluminous eruptive episode at Mount Shasta is low but should not be ignored in evaluating future possible eruptive hazards.

California↗

USGS2018

Eruptive history of Middle Sister, Oregon Cascades-Product of a late Pleistocene eruptive episode

New mapping, geochemistry, and argon geochronology illuminate a brief, remarkably silicic episode set in a mafic segment of the Cascade arc. Middle Sister was constructed during a 35-k.y. episode in the late Pleistocene from mafic, intermediate, and silicic eruptions adjacent to the primarily rhyolitic South Sister. Eruptions in the Three Sisters volcanic cluster prior to 50 ka were exclusively mafic (<57 wt% SiO 2 ), and several basaltic andesite lava flows can be traced to Middle Sister or a predecessor volcano (prior to 150 ka). Lava flows erupted 50–37 ka at Middle Sister and on its periphery were chemically diverse, with abundant basaltic andesite, a high-silica rhyolite flow, and an andesite produced from mixing of a rhyolite and mafic magma. Abundant rhyolite and rhyodacite erupted in this interval also at South Sister. Eruptive activity paused at Middle Sister 37–27 ka but continued at South Sister with large volumes of dacite and andesite lavas. Middle Sister erupted mafic, intermediate, and silicic lava flows 27–15 ka and then ceased to erupt. Calculated eruptive rates for the entire Three Sisters volcanic cluster quadrupled from ∼0.2 to ∼0.8 km 3 /k.y. between 50 and 15 ka, largely owing to the eruptions focused at Middle and South Sisters, and the cluster has now returned to its modest eruptive output, mainly away from the stratovolcanoes. Time–volume results for the volcanic cluster are compared to studies of other well-mapped, well-dated stratovolcanoes. Nearly all centers record similar eruptive-volume behavior with long histories of relatively constant output punctuated by short episodes of voluminous eruptions. In addition to the Three Sisters, two of these centers (Mt. Mazama, Crater Lake, Oregon, and Puyehue/Cordon Caule in the southern Andes) record significant compositional changes associated with the voluminous eruptive episodes.

Oregon↗

USGS2018

McGee Till—oldest glacial deposit in the Sierra Nevada, California— and Quaternary evolution of the rangefront escarpment

The McGee Till is an early Pleistocene glacial diamict as thick as 50 m, preserved over an area of 1.65 km 2 on a relict low-relief Pliocene plateau that stands 900 m higher than mouths of its bounding canyons, on the rangefront of the Sierra Nevada. Although recognized 90 years ago as the oldest till in the Sierra, its age and relation to the next oldest Sierran till have remained uncertain, even controversial. This contribution seeks to clarify both. The McGee Till consists predominantly of grussy boulders and sandy-granular matrix derived largely from a distinctive Cretaceous granodiorite that walls McGee Creek canyon 4–8 km to the south. The till rests directly upon two different basaltic units that yield 40 Ar/ 39 Ar ages of 2.8 and 2.6 Ma and show little or no evidence of preglacial erosion. The basalts preserve a minimum of 165–255 m of relief on steep slopes that existed around the plateau margins at the time of their eruption. McGee Creek consists of two segments—a north-directed reach that confined the glacier that deposited the till and, now diverging at a right bend just upvalley from the till, a northeast-flowing reach that was incised later. The base of the McGee Till is at 3160 m elevation on the present-day rim of McGee Creek, 610 m above the bend. The base of the 130-ka Tahoe Till (MIS 6) is at 2550 m elevation directly downslope from the McGee Till and at 2300 m at the rangefront mouth of the canyon's northeast reach. The base of the 900–866 ka Sherwin Till (MIS 22) is at 2400 m at the nearby rangefront mouth of Rock Creek. As the canyons were cut to nearly modern depths before the Sherwin glaciation, the high-perched McGee Till is probably older than 2 Ma and possibly close in age to the 2.6 Ma basalt it overlies. Growth in rangefront relief since about 3.0–2.5 Ma owes to normal slip on the Hilton Creek and Round Valley Faults east of McGee Mountain as well as to the 767-ka collapse of Long Valley caldera to its north.

California↗

USGS2017

Early postcaldera rhyolite and structural resurgence at Long Valley Caldera, California

After the 767-ka caldera-forming eruption of 650 km 3 of rhyolite magma as the Bishop Tuff, 90–100 km 3 of similar rhyolite erupted in the west-central part of Long Valley caldera in as many as 40 batches spread over the 110,000-year interval from ~ 750 ka to ~ 640 ka. Centrally, this Early Rhyolite (ER) is as thick as 622 m, but it spread radially to cover much of the caldera floor, where half its area is now concealed by post-ER sediments and lavas. At least 75% of the ER is aphyric rhyolite tuff. Drillholes encountered ~ 22 (altered) ER lava flows intercalated in the pyroclastic pile, and another 11 units of (largely fresh) ER lava are exposed on the caldera's resurgent dome and at Lookout Mountain. Exposed units have been distinguished, mapped, studied petrographically and chemically, and radioisotopically dated; each is described in detail. Their phenocryst contents range from 0 to 2.5 wt%. All the phyric units have plagioclase, orthopyroxene, and ilmenite; most have biotite and rare tiny magnetite, and a few contain rare zircon. The compositional range of fresh obsidians is narrow—74.3–75.0% SiO 2 , 1.21–1.37% FeO*, and 5.12–5.26% K 2 O, but wider variations in Ti, Ba, Sr, and Zr permit distinction of individual units and eruptive groups. The limited chemical and petrographic variability shown by so many ER batches released episodically for ~ 110,000 years suggests a thermally buffered and well-stirred reservoir. The ER central area, where ER eruptions had taken place, was uplifted ~ 400 m to form a structural dome ~ 10 km in diameter. Most of the inflation is attributable to 10 sills of ER that intrude the Bishop Tuff beneath the uplift, but other processes potentially contributing to resurgence are also considered. As shown by erratics of Mesozoic rocks ice-rafted from the Sierra Nevada and dropped on ER lavas, much of the ER had erupted early enough and at low enough elevation to be inundated by the intracaldera lake and was only later lifted by the resurgence that also raised clusters of the erratics hundreds of meters higher than any shoreline. Most of the uplift was over by ~ 570 ka, but dome-crossing faults that exhibit normal throw of 10–30 m cut lavas as young as 175–125 ka. For most elements, chemical ranges of the ER lie within those of the zoned Bishop Tuff, which had erupted earlier from the same place. Only Ba, Zr, Hf, and Eu/Eu* extend to ranges outside those of the Bishop Tuff, nominally to less evolved compositions. Initial 87 Sr/ 86 Sr values of ER are likewise within the range of the Bishop Tuff, but ER ratios of 143 Nd/ 144 Nd and 206 Pb/ 204 Pb extend beyond those of the Bishop Tuff to values slightly more influenced by upper-crustal contributions. FeTi-oxide geothermometry yields 752°–844 °C for ER, compared to 700°–820 °C for the Bishop Tuff. ER fO 2 values are 0.5–1.0 log units more reduced than those of the T–fO 2 array of the Bishop Tuff. The postcaldera reduction may reflect reaction with graphite from the black lithics of Paleozoic graphitic metapelite so abundant in the Bishop Tuff. Much of the pumice emplaced during the later half of the Bishop Tuff eruption has 10–25 wt% phenocrysts, dominantly quartz and sanidine, but the 100 km 3 of ER has only 0–2.5 wt% and completely lacks quartz and sanidine. Postcaldera processes, including mixing, volatile ascent, and crystal resorption, as well as potential contaminants and magmatic inputs, are all considered.

California↗

USGS2017

Eruptive history of the Ubehebe Crater Cluster, Death Valley, California

A sequence of late Holocene eruptions from the Ubehebe Crater cluster in Death Valley was short-lived, emplacing several phreatomagmatic and magmatic deposits. Seven craters form the main group, which erupted along a north-south alignment 1.5 km long. At least five more make a 500-m east-west alignment west of the main crater group. One more is an isolated shallow crater ~ 400 m south of that alignment. All erupted through Miocene fanglomerate and sandstone, which are now distributed as comminuted matrix and lithic clasts in all Ubehebe deposits. Stratigraphic evidence showing that all Ubehebe strata were emplaced within a short time interval includes: (1) deposits from the many Ubehebe vents make a multi-package sequence that conformably drapes paleo-basement topography with no erosive gullying between emplacement units; (2) several crater rims that formed early in the eruptive sequence are draped smoothly by subsequent deposits; and (3) tack-welded to agglutinated spatter and bombs that erupted at various times through the sequence remained hot enough to oxidize the overlying youngest emplacement package. In addition, all deposits sufficiently consolidated to be drilled yield reliable paleomagnetic directions, with site mean directions showing no evidence of geomagnetic secular variation. Chemical analyses of juvenile components representing every eruptive package yield a narrow range in major elements [SiO 2 (48.65–50.11); MgO (4.98–6.23); K 2 O (2.24–2.39)] and trace elements [Rb (28–33); Sr (1513–1588); Zr (373–404)]. Despite lithologic similarities, individual fall units can be traced outward from vent by recording layer thicknesses, maximum scoria and lithic sizes, and juvenile clast textural variations. This permits reconstruction of the eruptive sequence, which produced a variety of eruptive styles. The largest and northernmost of the craters, Ubehebe Crater, is the youngest of the group. Its largely phreatomagmatic deposits drape all of the others, thicken in paleogullies and thin over several newly created crater rims. Evidence in-hand virtually requires that the Ubehebe cluster of craters erupted over a brief time interval, not protracted over centuries.

California↗

USGS2016

Katmai National Park and Preserve and Alagnak Wild River: Geologic resources inventory report

The Geologic Resources Inventory (GRI) is one of 12 inventories funded by the National Park Service (NPS) Inventory and Monitoring Program. The Geologic Resources Division of the NPS Natural Resource Stewardship and Science Directorate administers the GRI. This GRI report was written for resource managers to support science-informed decision making. It may also be useful for interpretation. The report was prepared using available geologic information. Chapters of the report discuss distinctive geologic features and processes, describe the geologic history leading to the present- day landscape, highlight geologic issues facing resource managers, and provide information about the associated GRI geologic map data. A poster (Plate 1, in pocket) illustrates these data.

Alaska↗