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USGS2003

Biodiversity changes in Cretaceous palynofloras of eastern Asia and western North America

Palynology has great potential for providing comparative data and interpretations about changes in biodiversity during the Cretaceous Period. This is especially true for both eastern Asia and western North America because of strong floristic similarities that existed between these regions during Cretaceous time. Also, because palynomorphs of terrestrial origin can be deposited in offshore as well as terrestrial environments, significant potential exists for marine-to-continental palynostratigraphic correlations in both regions. Palynological biostratigraphy can improve the geologic dating of changes in biodiversity. During the Early Cretaceous, eastern Asia and western North America lay within the Cerebropollenites palynofloral province, a circumpolar phytogeographic zone characterized by distinctive palynological assemblages. During most of the Late Cretaceous, these regions lay within the palynofloristically unique Aquilapollenites Province, which was more restricted geographically than the Cerebropollenites Province. The most important development during Cretaceous time that is reflected in palynological assemblages was the rise of the angiosperms as the numerically and ecologically dominant forms of vegetation. The most striking short-term palynofloral event in the two regions was the sudden disappearance of species of Aquilapollenites and associated genera at the Cretaceous-Tertiary (K/T) boundary. Both of these occurrences produced major changes in biodiversity in the terrestrial realm. Geologic research in International Geological Correlation Program Project 434 can benefit from applications of palynostratigraphy. Palynologic research within Project 434 could include development of a comprehensive palynostratigraphic zonation for the Cretaceous, the definition of regional palynostratigraphic datums, and investigation of the record of floral change at the K/T boundary. ?? 2002 Elsevier Science Ltd. All rights reserved.

Journal of Asian Earth Sciences↗

USGS2013

Ambient seismic noise interferometry in Hawai'i reveals long-range observability of volcanic tremor

The use of seismic noise interferometry to retrieve Green's functions and the analysis of volcanic tremor are both useful in studying volcano dynamics. Whereas seismic noise interferometry allows long-range extraction of interpretable signals from a relatively weak noise wavefield, the characterization of volcanic tremor often requires a dense seismic array close to the source. We here show that standard processing of seismic noise interferometry yields volcanic tremor signals observable over large distances exceeding 50 km. Our study comprises 2.5 yr of data from the U.S. Geological Survey Hawaiian Volcano Observatory short period seismic network. Examining more than 700 station pairs, we find anomalous and temporally coherent signals that obscure the Green's functions. The time windows and frequency bands of these anomalous signals correspond well with the characteristics of previously studied volcanic tremor sources at Pu'u 'Ō'ō and Halema'uma'u craters. We use the derived noise cross-correlation functions to perform a grid-search for source location, confirming that these signals are surface waves originating from the known tremor sources. A grid-search with only distant stations verifies that useful tremor signals can indeed be recovered far from the source. Our results suggest that the specific data processing in seismic noise interferometry—typically used for Green's function retrieval—can aid in the study of both the wavefield and source location of volcanic tremor over large distances. In view of using the derived Green's functions to image heterogeneity and study temporal velocity changes at volcanic regions, however, our results illustrate how care should be taken when contamination by tremor may be present.

Hawai'i↗

USGS2006

Characterization and petrologic interpretation of olivine-rich basalts at Gusev Crater, Mars

Rocks on the floor of Gusev crater are basalts of uniform composition and mineralogy. Olivine, the only mineral to have been identified or inferred from data by all instruments on the Spirit rover, is especially abundant in these rocks. These picritic basalts are similar in many respects to certain Martian meteorites (olivine-phyric shergottites). The olivine megacrysts in both have intermediate compositions, with modal abundances ranging up to 20-30%. Associated minerals in both include low-calcium and high-calcium pyroxenes, plagioclase of intermediate composition, iron-titanium-chromium oxides, and phosphate. These rocks also share minor element trends, reflected in their nickel-magnesium and chromium-magnesium ratios. Gusev basalts and shergottites appear to have formed from primitive magmas produced by melting an undepleted mantle at depth and erupted without significant fractionation. However, apparent differences between Gusev rocks and shergottites in their ages, plagioclase abundances, and volatile contents preclude direct correlation. Orbital determinations of global olivine distribution and compositions by thermal emission spectroscopy suggest that olivine-rich rocks may be widespread. Because weathering under acidic conditions preferentially attacks olivine and disguises such rocks beneath alteration rinds, picritic basalts formed from primitive magmas may even be a common component of the Martian crust formed during ancient and recent times.

Journal of Geophysical Research E: Planets↗

USGS2002

Scaup migration patterns in North Dakota relative to temperatures and water conditions

Greater ( Aythya marila ) and lesser scaup ( A. affinis ) have protracted spring migrations. Migrants may still be present on southern breeding areas when the annual Waterfowl Breeding Population and Habitat Surveys (WBPHS) are being conducted. Understanding factors affecting the chronology and rate of spring migration is important for the interpretation of data from annual population surveys. We describe the general temporal pattern of scaup numbers in south-central North Dakota in spring, examine the relationships between scaup numbers and measures of local water conditions and spring temperatures, and assess timing of the WBPHS relative to numbers of scaup occurring in the study area in late May. Scaup were counted weekly on a 95-km, 400-m-wide transect from late March through May, 1957-1999. Average numbers of scaup per count were positively associated with numbers of seasonal, semipermanent, and total ponds. Average minimum daily ambient temperatures showed a trend of increasing temperatures over the 43 years, and dates of peak scaup counts became progressively earlier. Weeks of early migration usually had higher temperatures than weeks of delayed migration. The relationship between temperature and timing of migration was strongest during the second and third weeks of April, which is A# 1 week before numbers peak (median date = 19 Apr). Trends in sex and pair ratios were not consistent among years. Counts in late May-early June indicated considerable annual variability in the magnitude of late migrants. Scaup numbers during this period seemed to stabilize in only 5 of the 19 years when 2 or more surveys were conducted after the WBPHS. These findings corroborate concerns regarding the accuracy of the WBPHS for representing breeding populations of scaup and the possibility of double-counting scaup in some years.

North Dakota↗

USGS1992

Ground water chemistry and geochemical modeling of water-rock interactions at the Osamu Utsumi mine and the Morro do Ferro analogue study sites, Poços de Caldas, Minas Gerais, Brazil

Surface and ground waters, collected over a period of three years from the Osamu Utsumi uranium mine and the Morro do Ferro thorium/rare-earth element (Th/REE) deposits, were analyzed and interpreted to identify the major hydrogeochemical processes. These results provided information on the current geochemical evolution of ground waters for two study sites within the Poços de Caldas Natural Analogue Project. The ground waters are a K–Fe–SO 4 –F type, a highly unusual composition related to intense weathering of a hydrothermally altered and mineralized complex of phonolites. Tritium and stable isotope data indicate that ground waters are of meteoric origin and are not affected significantly by evaporation or water–rock interactions. Recharging ground waters at both study sites demonstrate water of less than about 35 years in age, whereas deeper, more evolved ground waters are below 1 TU but still contain in most cases detectable tritium. These deeper ground waters may be interpreted as being of 35 to 60 or more years in age, resulting mainly from an admixture of younger with older ground waters and/or indicating the influence of subsurface produced tritium. Geochemical processes involving water–rock–gas interactions have been modeled using ground water compositions, mineralogic data, ion plots and computations of speciation, non-thermodynamic mass balance and thermodynamic mass transfer. The geochemical reaction models can reproduce the water chemistry and mineral occurrences and they were validated by comparing the results of thermodynamic mass transfer calculations (using the PHREEQE program, Parkhurst et al., 1980). The results from the geochemical reaction models reveal that the dominant processes are production of CO 2 in the soil zone through aerobic decay of organic matter, dissolution of fluorite, calcite, K-feldspar, albite, chlorite and manganese oxides, oxidation of pyrite and sphalerite, and precipitation of ferric oxides, silica and kaolinite. Gibbsite precipitation can be modeled for the shallow (recharge) water chemistry at Morro do Ferro, consistent with known mineralogy. Recharge waters are undersaturated with respect to barite and discharging waters and deeper ground waters are saturated to supersaturated with respect to barite demonstrating a strong solubility control. Strontium isotope data demonstrate that sources other than calcium-bearing minerals are required to account for the dissolved strontium in the ground waters. These may include K-feldspar, smectite–chlorite mixed-layer clays and goyazite [SrAl 3 (PO 4 ) 2 (OH) 5 • H 2 O]. 1992.

Journal of Geochemical Exploration↗

USGS2007

Ovarian follicle dynamics of female Greater Scaup during egg production

Studies of female waterfowl nutrient reserve use during egg production require a precise understanding of ovarian follicle dynamics to correctly interpret breeding status, and, therefore, derive proper inference. Concerns over numerical declines of North American scaup have increased the need to better understand the role of female condition in reproductive performance. We quantified ovarian follicle dynamics of female Greater Scaup ( Aythya marila ) breeding on the Yukon–Kuskokwim Delta, Alaska, using a method that accounts for within day variation in follicle size. We considered several models for describing changes in follicle growth with the best supported model estimating the duration of rapid follicle growth (RFG) to be 5.20 ± 0.52 days (±95% confidence intervals) for each developing follicle. Average diameter and dry mass of preovulatory follicles were estimated to be 9.36 mm and 0.26 g, respectively, at the onset of RFG, and these follicle characteristics were 41.47 mm and 15.57 g, respectively, at ovulation. The average diameter of postovulatory follicles immediately following ovulation was estimated to be 17.35 mm, regressing quickly over several days. In addition, we derived predictive equations using diameter and dry mass to estimate the number of days before, and after, ovulation for pre- and postovulatory follicles, as well as an equation to estimate dry mass of damaged follicles. Our results allow precise definition of RFG and nest initiation dates, clutch size, and the daily energetic and nutritional demands of egg production at the individual level. This study provides the necessary foundation for additional work on Greater Scaup reproductive energetics and physiology, and offers an approach for quantifying ovarian follicle dynamics in other species.

Journal of Field Ornithology↗

USGS2019

National Gas Hydrate Program expedition 02: Identification of gas hydrate prospects in the Krishna-Godavari Basin, offshore India

After completing the first expedition of India's National Gas Hydrate Program (NGHP-01) in 2006, it was concluded that for the next expedition (National Gas Hydrate Program 02; NGHP-02), a new drill site review effort should focus on identifying potential deep-water offshore gas hydrate accumulations in sand dominated depositional environments. Therefore, geological and geophysical data analysis and 3D seismic data interpretation along with associated seismic modeling were carried out in three areas of the Krishna-Godavari Basin: Areas B, C, and E. Conventional petroleum exploration approaches of seismic amplitude evaluation were adapted to prospect for potential sand-rich depositional systems within the gas hydrate stability zone. Subsequently, these prospective areas were further assessed through the geological and geophysical evaluation of depositional setting, gas sources, and gas migration pathways. In Area B, prospecting focused on a large anticlinal structure with a prominent bottom-simulating reflector and several key horizons that indicated evidence for potential sand-hosted hydrate occurrences. In Area C, the prospects were distributed throughout various settings within a very large deep-water channel-levee-fan system with complex indications of potential gas hydrate occurrence in sand-prone seismic facies. In Area E, prospects were associated with high amplitude events within inferred channel-levee sequences. Based on the pre-expedition/onboard drill-site evaluation, the 22 most promising sites in the Krishna-Godavari Basin were identified and prioritized to investigate and delineate a total of 17 identified gas hydrate prospects. This paper describes the geo-scientific studies carried out prior to NGHP-02 for site identification, evaluation and prioritization. An important outcome of this study is the identification of two potentially producible gas hydrate systems inferred to host significant quantity of gas hydrate in stratigraphic-structural traps.

Journal of Marine and Petroleum Geology↗

USGS1994

Geochemistry of the 1989-1990 eruption of redoubt volcano: Part I. Whole-rock major- and trace-element chemistry

The 1989-1990 eruption of Redoubt Volcano produced medium-K calc-alkaline andesite and dacite of limited compositional range (58.2-63.4% SiO2) and entrained quenched andesitic inclusions (55% SiO2) which bear chemical similarities to the rest of the ejecta. The earliest (December 15) magmas are pumiceous, often compositionally banded, and the majority is relatively mafic (< 59% SiO2). The most silicic magmas of the eruption are the late December to early January domes (up to 63.4% SiO2). Subsequent magmas formed domes and rare pumices which converge on 60% SiO2. Chemical variations among ejecta comprise tight, linear, two-component arrays for all elements for which the analytical uncertainty is much less than the compositional range. The two-component arrays are interpreted as mixing arrays between unrelated magmas because several of the arrays are at steep angles to the normal liquid line of descent. Additionally, the felsic endmember cannot be easily related to the mafic endmember by normal high-temperature igneous processes (e.g., the silicic endmember has higher Zr yet lower Hf than the mafic endmember). Also relative enrichments of highly incompatible elements are dramatically different across the arrays. The mixing event must have preceded eruption by a significant, yet unspecified amount of time because groundmass glass compositions are homogeneous for all post-December samples (Swanson et al., 1994-this volume), in spite of the whole-rock chemical diversity. This implies time for additional crystallization after the mixing event. Swanson et al. (1994-this volume) discuss evidence for a potentially different mixing event recorded only in December 15 magmas. Cognate cumulate xenoliths composed of pl+cpx+opx+hb+mt+melt were recovered from January and April deposits. These blocks differ from local batholithic country rock in their low concentrations of incompatible elements (e.g., Rb < 5 ppm vs 20-90 ppm, Ba < 150 ppm vs 300-2000 ppm) and low SiO2 (< 50 wt.% vs > 60 wt.%). They have Mg, Cr, Ni, Sc, and V contents higher than the andesites, but lower than Redoubt basalts and basaltic andesites. Thus, they may be crystallization products of andesites, but do not represent the cumulate residue of basalt fractionation. The xenoliths were probably derived from a shallow or intermediate crustal chamber. ?? 1994.

Journal of Volcanology and Geothermal Research↗

USGS2011

Sources and physical processes responsible for OH/H2O in the lunarsoil as revealed by the Moon Mineralogy Mapper (M3)

Analysis of two absorption features near 3 μ m in the lunar reflectance spectrum, observed by the orbiting M 3 spectrometer and interpreted as being due to OH and H 2 O, is presented, and the results are used to discuss the processes producing these molecules. This analysis focuses on the dependence of the absorptions on lunar physical properties, including composition, illumination, latitude, and temperature. Solar wind proton-induced hydroxylation is proposed as the creation process, and its products could be a source for other reported types of hydrogen-rich material and water. The irregular and damaged fine-grained lunar soil seems especially adapted for trapping solar wind protons and forming OH owing to abundant dangling oxygen bonds. The M 3 data reveal that the strengths of the two absorptions are correlated and widespread, and both are correlated with lunar composition but in different ways. Feldspathic material seems richer in OH. These results seem to rule out water from the lunar interior and cometary infall as major sources. There appear to be correlations of apparent band strengths with time of day and lighting conditions. However, thermal emission from the Moon reduces the apparent strengths of the M 3 absorptions, and its removal is not yet completely successful. Further, many of the lunar physical properties are themselves intercorrelated, and so separating these dependencies on the absorptions is difficult, due to the incomplete M 3 data set. This process should also operate on other airless silicate surfaces, such as Mercury and Vesta, which will be visited by the Dawn spacecraft in mid-2011.

Journal of Geophysical Research E: Planets↗

USGS2021

Deepwater debrites and linked megaturbidites in confined basins: An example from the Onnuri Basin, East Sea of Korea

We analyzed data from seven piston cores, multi-channel seismic-reflection (MCS) and chirp profiles, and multibeam echosounder (MBES) data to study the distribution, emplacement time, sedimentary facies, and depositional processes of sediment-gravity-flow deposits in the Onnuri Basin, a confined basin in the East Sea. These data reveal that debris flows have traveled ca. 30 km downslope, forming a seismic facies consisting of stacked, wedge-shaped, transparent units separated by high-amplitude continuous reflectors. Analysis of piston cores shows three distinct sedimentary units, throughout the basin. The lowest unit, I, is a debrite containing numerous mud clasts of varying size and color distributed in a mud-rich matrix; it is absent over elevated basinal highs or ridges, such as the Onnuri Ridge, suggesting that local topography controls its distribution. The debrite forms a recognizable acoustically transparent layer on subbottom chirp profiles (av. 7 m thick), covers approximately 500 km 2 , and has an estimated volume of ∼ 3.5 km 3 . The overlying unit, II, contains normally graded beds composed of massive sand, laminated and cross-laminated sand and silt, and a thick cap of structureless mud. This unit is interpreted to be a megaturbidite deposited from turbidity currents that originated from the flow transformation of debris flows on the upper continental slope. The megaturbidite covers the entire basin (at least 650 km 2 ), and has an average thickness of 2.8 m (maximum thickness of 4.35 m), and comprises a volume of 1.8 km 3 . Variations in grain size and sedimentary structures suggest that the megaturbidite was deposited by progressively waning flows that reflected off basin flanks and ridges. The thick (up to 3.65 m) structureless mud cap further indicates deposition in a confined basin. The sharp basal contact, together with the lack of hemipelagic sediments between debrite and overlying megaturbidite, suggest that both were deposited during the same flow event, likely to have originated from a single catastrophic slope failure. Collapsing slide material evolved into a debris flow, from which a turbidite formed by dilution of the debris flow. Radiocarbon dates suggest that the slope failure occurred about 13–11 ka, a time when sea level was ca. 50 m lower than at the present day. Hemipelagic sediments in the topmost unit, III-2, above the megaturbidite indicate that the basin has been stable since ca. 11 ka. We provide robust evidence that submarine slope failures evolve downslope into slides, debris flows, and finally, thick megaturbidites. This contribution highlights the importance of seafloor morphology on the distribution and stratigraphy of submarine flows in confined basins.

Onnuri Basin↗

USGS2010

Rayleigh-wave phase-velocity maps and three-dimensional shear velocity structure of the western US from local non-plane surface wave tomography

We utilize two-and-three-quarter years of vertical-component recordings made by the Transportable Array (TA) component of Earthscope to constrain three-dimensional (3-D) seismic shear wave velocity structure in the upper 200 km of the western United States. Single-taper spectral estimation is used to compile measurements of complex spectral amplitudes from 44 317 seismograms generated by 123 teleseismic events. In the ﬁrst step employed to determine the Rayleigh-wave phase-velocity structure, we implement a new tomographic method, which is simpler and more robust than scattering-based methods (e.g. multi-plane surface wave tomography). The TA is effectively implemented as a large number of local arrays by deﬁning a horizontal Gaussian smoothing distance that weights observations near a given target point. The complex spectral-amplitude measurements are interpreted with the spherical Helmholtz equation using local observations about a succession of target points, resulting in Rayleigh-wave phase-velocity maps at periods over the range of 18–125 s. The derived maps depend on the form of local ﬁts to the Helmholtz equation, which generally involve the nonplane-wave solutions of Friederich et al. In a second step, the phase-velocity maps are used to derive 3-D shear velocity structure. The 3-D velocity images conﬁrm details witnessed in prior body-wave and surface-wave studies and reveal new structures, including a deep (>100 km deep) high-velocity lineament, of width ∼200 km, stretching from the southern Great Valley to northern Utah that may be a relic of plate subduction or, alternatively, either a remnant of the Mojave Precambrian Province or a mantle downwelling. Mantle seismic velocity is highly correlated with heat ﬂow, Holocene volcanism, elastic plate thickness and seismicity. This suggests that shallow mantle structure provides the heat source for associated magmatism, as well as thinning of the thermal lithosphere, leading to relatively high stress concentration. Our images also conﬁrm the presence of high-velocity mantle at 100 km depth beneath areas of suspected mantle delamination (southern Sierra Nevada; Grande Ronde uplift), low velocity mantle underlying active rift zones, and high velocity mantle associated with the subducting Juan de Fuca plate. Structure established during the Proterozoic appears to exert a lasting inﬂuence on subsequent volcanism and tectonism up to the Present.

Geophysical Journal International↗

USGS2011

Columbus crater and other possible groundwater-fed paleolakes of Terra Sirenum, Mars

Columbus crater in the Terra Sirenum region of the Martian southern highlands contains light‐toned layered deposits with interbedded sulfate and phyllosilicate minerals, a rare occurrence on Mars. Here we investigate in detail the morphology, thermophysical properties, mineralogy, and stratigraphy of these deposits; explore their regional context; and interpret the crater's aqueous history. Hydrated mineral‐bearing deposits occupy a discrete ring around the walls of Columbus crater and are also exposed beneath younger materials, possibly lava flows, on its floor. Widespread minerals identified in the crater include gypsum, polyhydrated and monohydrated Mg/Fe‐sulfates, and kaolinite; localized deposits consistent with montmorillonite, Fe/Mg‐phyllosilicates, jarosite, alunite, and crystalline ferric oxide or hydroxide are also detected. Thermal emission spectra suggest abundances of these minerals in the tens of percent range. Other craters in northwest Terra Sirenum also contain layered deposits and Al/Fe/Mg‐phyllosilicates, but sulfates have so far been found only in Columbus and Cross craters. The region's intercrater plains contain scattered exposures of Al‐phyllosilicates and one isolated mound with opaline silica, in addition to more common Fe/Mg‐phyllosilicates with chlorides. A Late Noachian age is estimated for the aqueous deposits in Columbus, coinciding with a period of inferred groundwater upwelling and evaporation, which (according to model results reported here) could have formed evaporites in Columbus and other craters in Terra Sirenum. Hypotheses for the origin of these deposits include groundwater cementation of crater‐filling sediments and/or direct precipitation from subaerial springs or in a deep (∼900 m) paleolake. Especially under the deep lake scenario, which we prefer, chemical gradients in Columbus crater may have created a habitable environment at this location on early Mars.

Journal of Geophysical Research E: Planets↗

USGS2017

FinDer v.2: Improved real-time ground-motion predictions for M2-M9 with seismic finite-source characterization

Recent studies suggest that small and large earthquakes nucleate similarly, and that they often have indistinguishable seismic waveform onsets. The characterization of earthquakes in real time, such as for earthquake early warning, therefore requires a flexible modeling approach that allows a small earthquake to become large as fault rupture evolves over time. Here, we present a modeling approach that generates a set of output parameters and uncertainty estimates that are consistent with both small/moderate (≤M6.5) and large earthquakes (>M6.5) as is required for a robust parameter interpretation and shaking forecast. Our approach treats earthquakes over the entire range of magnitudes (>M2) as finite line-source ruptures, with the dimensions of small earthquakes being very small (<100 m) and those of large earthquakes exceeding several tens to hundreds of kilometres in length. The extent of the assumed line source is estimated from the level and distribution of high-frequency peak acceleration amplitudes observed in a local seismic network. High-frequency motions are well suited for this approach, because they are mainly controlled by the distance to the rupturing fault. Observed ground-motion patterns are compared with theoretical templates modeled from empirical ground-motion prediction equations to determine the best line source and uncertainties. Our algorithm extends earlier work by Böse et al. for large finite-fault ruptures. This paper gives a detailed summary of the new algorithm and its offline performance for the 2016 M7.0 Kumamoto, Japan and 2014 M6.0 South Napa, California earthquakes, as well as its performance for about 100 real-time detected local earthquakes (2.2 ≤ M ≤ 5.1) in California. For most events, both the rupture length and the strike are well constrained within a few seconds (<10 s) of the event origin. In large earthquakes, this could allow for providing warnings of up to several tens of seconds. The algorithm could also be useful for resolving fault plane ambiguities of focal mechanisms and identification of rupturing faults for earthquakes as small as M2.5.

California↗

USGS1993

Relations of ammonium minerals at several hydrothermal systems in the western U.S.

Ammonium bound to silicate and sulfate minerals has recently been located at several major hydrothermal systems in the western U.S. utilizing newly-discovered near-infrared spectral properties. Knowledge of the origin and mineralogic relations of ammonium minerals at known hydrothermal systems is critical for the proper interpretation of remote sensing data and for testing of possible links to mineralization. Submicroscopic analysis of ammonium minerals from two mercury- and gold-bearing hot-springs deposits at Ivanhoe, Nevada and McLaughlin, California shows that the ammonium feldspar, buddingtonite, occurs as fine-grained euhedral crystals coating larger sulfide and quartz crystals. Ammonium feldspar seems to precipitate relatively late in the crystallization sequence and shows evidence for replacement of NH4+ by K+ or other monovalent cations. Some buddingtonite is observed in close association with mercury, but not with gold. Ammonioalunite is found in a variety of isolated crystal forms at both deposits. Nitrogen isotopic values for ammonium-bearing minerals show a 14??? range in composition, precluding assignment of a specific provenance to the nitrogen. The correlations of nitrogen isotopic values with depth and ammonium content suggest some loss of nitrogen in the oxidizing supergene environment, possibly as a metastable mineral. The high ammonium content in these hydrothermal systems, the close association to mercury, and the small crystal size of the ammonium-bearing minerals all suggest that ammonium may be transported in a late-stage vapor phase or as an organic volatile. Such a process could lead to the formation of a non-carbonaceous organic aureole above a buried geothermal source. The discovery of a 10-km outcrop of ammonium minerals confirms that significant substitution of ammonium in minerals is possible over an extensive area and that remote sensing is a feasible means to detect such aureoles. ?? 1993.

Journal of Volcanology and Geothermal Research↗

USGS2007

Possible refugia in the Alexander Archipelago of southeastern Alaska during the late Wisconsin glaciation

The interpretation of the extent of late Wisconsin glaciation in southeastern Alaska has varied between geologists and biologists. Maps and reports of the region prepared by geologists commonly indicated that late Wisconsin ice extended as a large uniform front west to the edge of the continental shelf. However, the distribution of plants and animals in the region has led many biologists to suggest that there may have been ice-free areas that served as refugia during the late Wisconsin. Based on analyses of aerial photographs, topographic maps, and bathymetric charts, in conjunction with a review of previous literature and reconnaissance fieldwork throughout the region, this study presents data supporting a limited ice extent in the Alexander Archipelago during the late Wisconsin and identifies possible ice-free areas that may have served as refugia. These areas include (1) the Fairweather Ground, (2) the Herbert Graves Island area, (3) the western coast of southern Baranof Island and adjacent continental shelf, (4) Coronation Island and the adjacent continental shelf, (5) the Warren Island area, (6) the continental shelf from west of Heceta Island to Forrester Island in the south, (7) parts of the west coast of southern Dall Island, and (8) lowland areas in southern Prince of Wales Island. The identification of these possible refugia has bearing on the recolonization of the Alexander Archipelago, as they could have served as centers of biotic dispersal upon regional deglaciation and as stepping stones for early humans with a maritime tradition entering the western hemisphere from Asia. ?? 2007 NRC Canada.

Canadian Journal of Earth Sciences↗

USGS2002

Linking the pacific decadal oscillation to seasonal stream discharge patterns in Southeast Alaska

This study identified and examined differences in Southeast Alaskan streamflow patterns between the two most recent modes of the Pacific decadal oscillation (PDO). Identifying relationships between the PDO and specific regional phenomena is important for understanding climate variability, interpreting historical hydrological variability, and improving water-resources forecasting. Stream discharge data from six watersheds in Southeast Alaska were divided into cold-PDO (1947-1976) and warm-PDO (1977-1998) subsets. For all watersheds, the average annual streamflows during cold-PDO years were not significantly different from warm-PDO years. Monthly and seasonal discharges, however, did differ significantly between the two subsets, with the warm-PDO winter flows being typically higher than the cold-PDO winter flows and the warm-PDO summer flows being typically lower than the cold-PDO flows. These results were consistent with and driven by observed temperature and snowfall patterns for the region. During warm-PDO winters, precipitation fell as rain and ran-off immediately, causing higher than normal winter streamflow. During cold-PDO winters, precipitation was stored as snow and ran off during the summer snowmelt, creating greater summer streamflows. The Mendenhall River was unique in that it experienced higher flows for all seasons during the warm-PDO relative to the cold-PDO. The large amount of Mendenhall River discharge caused by glacial melt during warm-PDO summers offset any flow reduction caused by lack of snow accumulation during warm-PDO winters. The effect of the PDO on Southeast Alaskan watersheds differs from other regions of the Pacific Coast of North America in that monthly/seasonal discharge patterns changed dramatically with the switch in PDO modes but annual discharge did not. ?? 2002 Elsevier Science B.V. All rights reserved.

Journal of Hydrology↗

USGS1978

Conductive heat flows in research drill holes in thermal areas of Yellowstone National Park, Wyoming

In convection systems with boiling springs, geysers, fumaroles, and other thermal features, the modes of heat flow become increasingly complex as a single liquid phase at depth rises into the near-surface environment where heat flows by convection of liquid and vapor and by conduction in high thermal gradients. This paper is mainly concerned with the changing patterns of conductive heat flow as related to channels of subsurface convective flow and to horizontal distance from spring vents. The primary data consist of temperatures measured in 13 cored drill holes as drilling progressed. Some temperatures plot convincingly on straight-line segments that suggest conductive gradients in rocks of nearly constant thermal conductivity. Temperature gradients and the conductive component of total heat flow nearly always decrease drastically downward; the gradient and heat flow of the lowest depth interval recognized in each hole is commonly only about 10 percent of the highest interval; the changes in gradient at interval boundaries are commonly interpreted as channels of near-boiling water or of cooler meteoric water. Temperature reversals are probably related to inflowing cooler water rather than to transient effects from recent changes. Some temperatures plot on curved segments that probably indicate dispersed convective upflow and boiling of water in ground penetrated by the drill hole. Other similar curved segments are too low in temperature for local boiling and are probably on the margins of hot upflow zones, reflecting conductive cooling of flowing water. The conifers of Yellowstone National Park (mainly lodgepole pine) seem to have normal growth characteristics where near-surface conductive heat flow is below about 200 heat-flow units (1 HFU = 10 -6 cal/cm 2 = 41.8 mW/m 2 ). Most areas of abnormal "stunted" trees (low ratio of height to base diameter, and low density of spacing) are characterized by conductive heat flows of about 250 to 350 HFU. The critical factor affecting growth is probably the seasonal maximum soil temperature at the root depths preferred by each form, rather than the heat flow as such. Heat flows up to 300 HFU are greatly dominated near the surface by conduction and are little affected by convection within the measured intervals. With increasing total heat flow above 300 HFU, the convection component, as indicated by snowfall calorimetry, becomes increasingly important. Snowfall calorimetry and tree growth as related to heat flow are calibrated by the heat-flow data considered here. Both snowfall calorimetry and tree growth patterns can be extrapolated rapidly, although without high precision, to thermal areas that lack subsurface data.

Wyoming↗

USGS2022

Characterization of bituminite in Kimmeridge Clay by confocal laser scanning and atomic force microscopy

This work investigates bituminite (amorphous sedimentary organic matter) in Upper Jurassic Kimmeridge Clay source rock via confocal laser scanning microscopy (CLSM) and atomic force microscopy (AFM). These petrographic tools were used to provide better understanding of the nature of bituminite, which has been historically difficult to identify and differentiate from similar organic matter types in source rocks. As part of an International Committee for Coal and Organic Petrology (ICCP) working group, an immature (0.42% vitrinite reflectance), organic-rich (44.1 wt% total organic carbon content) sample of Kimmeridge Clay was distributed to multiple laboratories for CLSM characterization. The primary observations from CLSM imaging and spectroscopy include: 1) the interpreted presence of Botryococcus algae as a contributor to bituminite precursors; 2) color red-shift of sulfide reflectance and bituminite auto-fluorescence from below the sample surface; 3) positive alteration of bituminite from laser-induced photo-oxidation of the sample surface, including fluorescence blue-shift; 4) fluorescence blue-shift associated to higher fluorescence intensity regions in bituminite indicative of compositional (fluorophore) differences; 5) the need for fluorescence spectroscopy standardization as applied via CLSM; and 6) the suitability of CLSM fluorescence spectroscopy to predict solid bitumen reflectance from bituminite spectral emission via calibration to an extant dataset. Secondary CLSM observations include detection of reflected laser light from highly reflective inclusions in bituminite, including sulfides and fusinite, and radiolytic alteration of bituminite caused by substitution of U for Fe in sulfides. Findings from AFM include the observation that surface roughening or surface flattening of bituminite are induced by differential broad ion beam (BIB) milling and are dependent on the location and scale of AFM topology measurement. This result highlights our still limited understanding of the effects of BIB milling on sedimentary organic matter and indicates the need for further research before this technique can be advanced as a standard practice in petrographic sample preparation. Collectively, the results of this study illustrate the general applicability and versatility of AFM and CLSM as tools for organic petrology research, specifically for better understanding of the nature and properties of the bituminite maceral.

Kimmeridge↗