Pinyon–juniper woodlands are dry ecosystems defined by the presence of juniper (Juniperus spp.) and pinyon pine (Pinus spp.), which stretch over 400 000 km2 across 10 US states. Certain areas have become unnaturally dense and have moved into former shrub and grasslands, while others have experienced widespread mortality. To properly manage these woodlands, sites must be evaluated individually and decisions made based on scientific information that is often not available. Many species utilize pinyon–juniper woodlands, including the pinyon jay (Gymnorhinus cyanocephalus), named for its mutualism with pinyon pine, whose population has declined by c. 2.2% per year from 1966 to 2022, an overall decrease of c. 71%. To increase the likelihood of further research progress, we propose a tool to model the distribution of pinyon pine at a finer scale than current woodland classification tools in the northern US Great Basin: a random forest model using geographical, ecological and climate variables. Our results achieved an accuracy of 93.94%, indicating high predictive power to identify locations of pinyon pine in north-eastern Nevada, the south-eastern corner of Oregon and southern Idaho. These findings can inform managers and planners researching pinyon pine, pinyon–juniper woodlands and potentially the pinyon jay.

Stibiogoldfieldite, Cu12(Sb2Te2)S13, was approved as a new mineral species from the Mohawk mine, Goldfield mining district, Esmeralda County, Nevada, USA. It occurs as metallic anhedral grains, dark grey in colour. It is associated with quartz, pyrite and an Ag–Bi–(S,Se) phase (holotype material) and with quartz, pyrite, calaverite, bismuthinite, bohdanowiczite, and the Ag–Bi–(S,Se) phase (cotype material). In reflected light, stibiogoldfieldite is isotropic, grey in colour, with indistinct brownish shade. Reflectance data in air [R (%)] are: 31.1 at 470 nm, 30.9 at 546 nm, 30.8 at 589 nm and 31.0 at 650 nm. Electron microprobe analysis for holotype material gave (in wt.% – average of 60 spot analyses): Cu 45.03(60), Ag 0.26(7), Fe 0.02(3), Zn 0.13(15), Sn 0.02(4), Pb 0.05(6), Sb 8.02(62), As 2.80(65), Bi 2.77(87), Te 15.15(1.24), S 24.50(32), Se 0.52(11), total 99.27(69). On the basis of (As + Sb + Te + Bi) = 4 atoms per formula unit (apfu), the empirical formula of stibiogoldfieldite is (Cu12.05Ag0.04Zn0.03Fe0.01)Σ12.13(Sb1.12As0.63Bi0.23Te2.02)Σ4.00(S12.99Se0.11)Σ13.10. Chemical data on an additional sample from the same locality (cotype material) gave the following results (in wt.% – average of 181 spot analyses): Cu 43.84(63), Ag 0.21(7), Sb 5.92(78), As 2.63(45), Te 20.07(1.19), S 25.13(53), Se 0.97(35), total 99.47(66). On the basis of (As + Sb + Te + Bi) = 4 apfu, the empirical formula of cotype material is (Cu11.30Ag0.03)Σ11.33(Sb0.80As0.57Bi0.06Te2.57)Σ4.00(S12.83Se0.20)Σ13.03. Stibiogoldfieldite is cubic, I$\overline 4$3m, with unit-cell parameters a = 10.3466(17) Å, V = 1107.6(5) Å3 and Z = 2 (holotype). Unit-cell parameters for the cotype sample are a = 10.3035(2) Å and V = 1093.83(7) Å3. The crystal structure of holotype stibiogoldfieldite was refined by single-crystal X-ray diffraction data to a final R1 = 0.032 on the basis of 285 reflections with Fo > 4σ(Fo) and 20 refined parameters. Stibiogoldfieldite is isotypic with other members of the tetrahedrite group.

Analyses of macroscopic charcoal, sediment geochemistry (%C, %N, C/N, δ13C, δ15N), and fossil pollen were conducted on a sediment core recovered from Stella Lake, Nevada, establishing a 2000 year record of fire history and vegetation change for the Great Basin. Charcoal accumulation rates (CHAR) indicate that fire activity, which was minimal from the beginning of the first millennium to AD 750, increased slightly at the onset of the Medieval Climate Anomaly (MCA). Observed changes in catchment vegetation were driven by hydroclimate variability during the early MCA. Two notable increases in CHAR, which occurred during the Little Ice Age (LIA), were identified as major fire events within the catchment. Increased C/N, enriched δ15N, and depleted δ13C values correspond with these events, providing additional evidence for the occurrence of catchment-scale fire events during the late fifteenth and late sixteenth centuries. Shifts in the vegetation community composition and structure accompanied these fires, with Pinus and Picea decreasing in relative abundance and Poaceae increasing in relative abundance following the fire events. During the LIA, the vegetation change and lacustrine geochemical response was most directly influenced by the occurrence of catchment-scale fires, not regional hydroclimate.

The Pioche Formation of SE Nevada preserves a diverse soft-bodied fauna from the early and middle Cambrian (Series 2–3: Stage 4–5). While the fauna is dominated by arthropods, animals belonging to other taxa can be found. Here we document the first occurrence of Herpetogaster collinsi outside the Burgess Shale. Further, the specimens are from the Nephrolenellus multinodus biozone and thus represent the oldest occurrence of the species, as well as possibly the earliest soft-bodied deuterostomes in Laurentia.

Ferribushmakinite (IMA2014-055), Pb2Fe3+(PO4)(VO4)(OH), the Fe3+ analogue of bushmakinite, is a new mineral from the Silver Coin mine, Valmy, Iron Point district, Humboldt County, Nevada, USA, where it occurs as a low-temperature secondary mineral in association with plumbogummite, mottramite, Br-rich chlorargyrite and baryte on massive quartz. Ferribushmakinite forms yellow slightly flattened prisms up to 0.2 mm long growing in X and sixling twins. The streak is pale yellow. Crystals are translucent and have adamantine lustre. The Mohs hardness is ∼2, the tenacity is brittle, the fracture is irregular to splintery and crystals exhibit one or two fair cleavages in the [010] zone. The calculated density is 6.154 g/cm3. Electron microprobe analyses provided: PbO 63.69, CaO 0.07, CuO 1.11, Fe2O3 7.63, Al2O3 1.63, V2O5 12.65, As2O5 3.09, P2O58.63, H2O 1.50 (structure), total 100.00 wt.% (normalized). The empirical formula (based on nine O a.p.f.u.) is: (Pb1.99Ca0.01)Σ2.00(Fe0.66Al0.22Cu0.10)Σ0.98(V0.97P0.85As0.19)Σ2.01O7.84(OH)1.16. Ferribushmakinite is monoclinic, P21/m, a = 7.7719(10), b = 5.9060(7), c = 8.7929(12) Å, β = 111.604(8)°, V = 375.24(9) Å3 and Z = 2. The eight strongest lines in the powder X-ray diffraction pattern are [dobs in Å (I)(hkl)]: 4.794(46)(011); 3.245(84)(211); 2.947(100)(020,212,103); 2.743(49)(112); 2.288(30)(220); 1.8532(27)(314,403); 1.8084(27)(multiple); and 1.7204(28)(312,114,321). Ferribushmakinite is a member of the brackebuschite supergroup. Its structure (R1 = 3.83% for 577 Fo > 4σF) differs from that of bushmakinite only in the dominance of Fe3+ over Al in the octahedral site.

Crimsonite (IMA2014-095), PbFe3+2(PO 4)2(OH)2, the phosphate analogue of carminite, is a new mineral from the Silver Coin mine, Valmy, Iron Point district, Humboldt County, Nevada, USA, where it occurs as a low-temperature secondary mineral in association with fluorwavellite, goethite, hematite, hentschelite, plumbogummite and variscite on quartz. Crimsonite occurs in subparallel aggregates of deep red blades or plates flattened on {100} and up to 0.1 mm in maximum dimension. The streak is light purplish orange. Crystals are transparent and have adamantine lustre. The Mohs hardness is ∼3½, the tenacity is brittle, the fracture is irregular to splintery and an imperfect cleavage is likely on {101}. The calculated density is 5.180 g/cm3. Crimsonite is optically biaxial (+), with 2V = 85.5(5)° and γ – α = 0.011. Using the Gladstone-Dale relationship, the calculated indices of refraction are α = 2.021, β = 2.026 and γ = 2.032. The optical orientation is X = b; Y = a; Z = c and the pleochroism is X light orange, Y light yellow, Z red brown; Y < X < Z. Electron microprobe analyses provided PbO 40.69, CaO 0.60, ZnO 0.72, CuO 0.13, Fe2O3 23.36, Al2O3 0.34, V2O5 0.70, As2O5 12.05, P2O5 16.03, SO3 0.33 and H2O 3.64 (structure), total 98.59 wt.%. The empirical formula (based on 10 O apfu) is (Pb1.06Ca0.06)∑1.12(Fe1.71Zn0.05Al0.04Cu0.01)∑1.81(P1.32As0.61V0.05S0.02)∑2.00O8[(OH)1.64(H2O)0.36]∑2.00. Crimsonite is orthorhombic, Cccm, a = 16.2535(13), b = 7.4724(4), c = 12.1533(9) Å, V = 1476.04(17) Å3 and Z = 8. The eight strongest lines in the powder X-ray diffraction pattern are [dobs in Å(I)(hkl)]: 5.86(42)(111); 4.53(45)(112); 3.485(64)(113); 3.190(100) (022); 3.026(40)(004); 2.902(54)(511); 2.502(77)(422) and 2.268(54)(224). The structure of crimsonite (R1 = 3.57% for 740 Fo > 4σF) contains FeO6 octahedra that share edges to form dimers, which are then linked to other dimers by corner sharing to form chains along [010]. These chains are linked by PO4 tetrahedra yielding sheets parallel to {001}. The sheets are linked to one another via bonds to 8-coordinated Pb2+ atoms with non-stereoactive 6s2 lone-electron pairs.

The mid-to-late Pleistocene Devils Hole δ18O record has been extended from 60,000 to 4500 yr ago. The new δ18O time series, in conjunction with the one previously published, is shown to be a proxy of Pacific Ocean sea surface temperature (SST) off the coast of California. During marine oxygen isotope stages (MIS) 2 and 6, the Devil Hole and SST time series exhibit a steady warming that began 5000 to > 10,000 yr prior to the last and penultimate deglaciations. Several possible proximate causes for this early warming are evaluated. The magnitude of the peak δ18O or SST during the last interglacial (LIG) is significantly greater (1 per mill and 2 to 3°C, respectively) than the peak value of these parameters for the Holocene; in contrast, benthic δ18O records of ice volume show only a few tenths per mill difference in the peak value for these interglacials. Statistical analysis provides an estimate of the large shared information (variation) between the Devils Hole and Eastern Pacific SST time series from ∼ 41 to ∼ 2°N and enforces the concept of a common forcing among all of these records. The extended Devils Hole record adds to evidence of the importance of uplands bordering the eastern Pacific as a source of archives for reconstructing Pacific climate variability.

Paleomagnetic secular variation in a portion of the Bonneville Alloformation is compared with secular variation in lacustrine sediments in the Mono Basin, California, and with secular variation in Lake Lahontan sediments in the northwestern Great Basin. The comparison places an age of about 18,000 yr B.P., and a span of 1000 to 3000 yr, on part of a transgressive stage of Lake Bonneville near Delta, Utah, that is coeval with a wet period in the Lahontan Basin.

Pollen and algae microfossils preserved in sediments from Pyramid Lake, Nevada, provide evidence for periods of persistent drought during the Holocene age. We analyzed one hundred nineteen 1-cm-thick samples for pollen and algae from a set of cores that span the past 7630 years. The early middle Holocene, 7600 to 6300 cal yr B.P., was found to be the driest period, although it included one short but intense wet phase. We suggest that Lake Tahoe was below its rim for most of this period, greatly reducing the volume and depth of Pyramid Lake. Middle Holocene aridity eased between 5000 and 3500 cal yr B.P. and climate became variable with distinct wet and dry phases. Lake Tahoe probably spilled intermittently during this time. No core was recovered that represented the period between 3500 and 2600 cal yr B.P. The past 2500 years appear to have had recurrent persistent droughts. The timing and magnitude of droughts identified in the pollen record compares favorably with previously published δ18O data from Pyramid Lake. The timing of these droughts also agrees with the ages of submerged rooted stumps in the Eastern Sierra Nevada and woodrat midden data from central Nevada. Prolonged drought episodes appear to correspond with the timing of ice drift minima (solar maxima) identified from North Atlantic marine sediments, suggesting that changes in solar irradiance may be a possible mechanism influencing century-scale drought in the western Great Basin.

Despite growing concerns that ecological stressors (fire, insect and pathogen outbreaks) may force vegetation change, few studies have attempted to use paleoecological data to understand small-scale interactions between disturbance and vegetation. Using charcoal and pollen data, we infer past fire episodes and subsequent vegetation responses for a limber pine (Pinus flexilis) forest in northwestern Nevada, USA, to determine local vegetation recovery from disturbance. Using superimposed epoch analysis we examined average-vegetation and individual-taxon responses to eight randomly selected fire events over the past 4.0 ka. Pollen evidence shows that on average fires produce a weak response of declining Pinus while other taxa including Artemisia and Poaceae increase directly after fire episodes. Within 30 yr of a disturbance, pollen data indicate ecosystem recovery to pre-fire composition, consistent with modern studies of fire recovery of limber pine forests. Similar to short-term changes of pollen abundance, long-term vegetation responses indicate Pinus abundance weakly declining and Artemisia increasing when fire episodes are frequent. However, despite fire-episode frequencies varying between 75 and 250 yr, the overall vegetation structure has remained relatively stable over the past 4.0 ka. Our study contributes to the limited information on the disturbance ecology of isolated, subalpine forests in the intermountain West.

Morphological and chemical characteristics were determined for airborne tungsten particles in Fallon, Nevada, a town that is distinguishable environmentally by elevated airborne tungsten and cobalt. From samples of airborne dust collected previously at six different places in Fallon, tungsten-rich dust particles were isolated and analyzed with automated electron microprobe and wavelength-dispersive spectrometry. Representative W particles were further analyzed using transmission electron microscopy. Morphologically, Fallon W particles are angular and small, with minimum and maximum sizes of ≤1 μm and 5.9 μm in diameter, respectively. The number and size of tungsten-rich particles decrease in Fallon with distance from a hard-metal facility located near the center of town. Chemically, Fallon airborne W particles include mixtures of tungsten with cobalt plus other metals such as chromium, iron, and copper. No W-rich particles were identifiable as CaWO4 (scheelite) or MnWO4 (huebnerite). From d-spacings, Fallon particles are most consistent with identification as tungsten carbide. Based on these multiple lines of evidence, airborne W particles in Fallon are anthropogenic in origin, not natural. The hard-metal facility in Fallon processes finely powdered W and W-Co, and further investigation using tracer particles is recommended to definitively identify the source of Fallon's airborne tungsten.

Two Ordovician graptolite assemblages are recognised and described for the first time in the allochthonous siliceous assemblage or succession forming the Guayacan Group of central Sonora in northwestern Mexico. A Middle Ordovician assemblage referable to the Nemagraptus gracilis-Climacograptus wilsoni zonal interval occurs in the upper siliceous shale of unit 1 of the Guayacan Group and an Upper Ordovician assemblage representative of the Dicellograptus ornatus Zone of the Pacific faunal province has been collected from shaly partings in the bedded radiolarian chert constituting unit 2. The stratigraphical make-up of the siliceous assemblage bears a striking similarity to the better known—and correlative—Lower Palaeozoic siliceous succession of central and northern Nevada, giving credence to the hypothesis that the Palaeozoic siliceous assemblage in northwestern Mexico was originally the extension of the Nevadan assemblage into California, which has been transposed to its present position along a left-lateral megashear of the magnitude of at least 1000 km.

A review of the proximal development of the spinose species remaining in the form genus Climacograptus Hall has led to the proposal to restrict the genus to Climacograptus bicornis (Hall), its type species, and to two other septate species of early Middle Ordovician age (Llandeilo-early Caradoc) with a primitive type of proximal-end development. The genus Euclimacograptus, with Climacograptus hastatus T. S. Hall as the type species, is proposed for spinose Upper Ordovician climacograptids with an advanced proximal-end development. The genus Ensigraptus, with Climacograptus caudatus Lapworth as the type species, is also proposed for species homeomorphic with those included in Normalograptus Legrand but with a less advanced proximal-end development. Five species are described.