Evaluation of models for the origin of Miocene low-δ18O rhyolites of the Yellowstone/Columbia River Large Igneous Province

Two models have been proposed for the origin of the low-δ¹⁸O rhyolites of the Snake River Plain–Yellowstone hotspot trend. The first involves a single multicyclic caldera system, or multiple nested or overlapping systems, in which the early-erupted products become hydrothermally altered and are subsequently melted to form low-δ¹⁸O rhyolites (Bindeman and Valley, 2001; Watts et al., 2011). The second model appeals to a crustal magma source which was hydrothermally altered in a thermal event prior to the onset of Miocene magmatism (Boroughs et al., 2005). We critically evaluate the plausibility of each and provide thermal, temporal, and volume constraints which must be included in any model for the petrogenesis of low-δ¹⁸O rhyolites of the central Snake River Plain. Although the models are not mutually exclusive, we conclude that a component of pre-existing low-δ¹⁸O crust is required in the central Snake River Plain where the greatest volumes of strongly ¹⁸O-depleted rhyolite occur. This component could be provided by meteoric–hydrothermally altered granites of the Idaho batholith, which are cut by the central Snake River Plain.     

Preservation of a Paleoproterozoic rifted margin in the Himalaya:Insight from the Ulleri-Phaplu-Melung orthogneiss

Orthogneiss within the Paleoproterozoic strata of Lesser Himalayan sequence across the Himalaya has been variably linked to development in a continental arc setting, Indian basement, or a continental rift.New whole rock and trace element geochemical data and U/Pb zircon geochronology indicate that the granitoid protoliths to these rocks were derived from upper crustal sources in the Paleoproterozoic and have within-plate, A-type affinities. This is consistent with their generation in a rifted margin and is compatible with paleogeographic reconstructions that indicate an open boundary for present-day northern India in the Paleoproterozoic.     

Isotopic evidence for temporal variation in proportion of seasonal precipitation since the last glacial time in the inland Pacific Northwest of the USA

Large-scale atmospheric circulation patterns determine the quantity and seasonality of precipitation, the major source of water in most terrestrial ecosystems. Oxygen isotope (δ¹⁸O) dynamics of the present-day hydrologic system in the Palouse region of the northwestern U.S.A. indicate a seasonal correlation between the δ¹⁸O values of precipitation and temperature, but no seasonal trends of δ¹⁸O records in soil water and shallow groundwater. Their isotope values are close to those of winter precipitation because the Palouse receives  75% of its precipitation during winter. Palouse Loess deposits contain late Pleistocene pedogenic carbonate having ca. 2 to 3‰ higher δ¹⁸O values and up to 5‰ higher carbon isotope (δ¹³C) values than Holocene and modern carbonates. The late Pleistocene δ¹⁸O values are best explained by a decrease in isotopically light winter precipitation relative to the modern winter-dominated infiltration. The δ¹³C values are attributed to a proportional increase of atmospheric CO₂ in soil CO₂ due to a decrease in soil respiration rate and ¹³C discrimination in plants under much drier paleoclimate conditions than today. The regional climate difference was likely related to anticyclonic circulation over the Pleistocene Laurentide and Ice Sheet.     

Site formation processes in the cody and early plains archaic levels at the laddie creek site,wyoming

The combination of previously published pedological and phytolith analyses with new information on the geology, palynology, and an innovative analysis of archaeological chipped stone remains (including backplots, cluster analyses of artifacts, and chipped stone refitting) clarifies the environment and site formation of the mid-Holocene deposits at the Laddie Creek site, Wyoming. Palynological analyses strengthen the argument made by Reider and Karlstrom (1987) that the site was slightly wetter and warmer during the Altithermal (7500–5000 B.P.). The mid-Holocene environment at the site was conductive to the formation of soils and the preservation of archaeological deposits. A Cody Complex level associated with a colluvial C horizon provides evidence of greater movement of this material than that seen in the multiple Early Plains Archaic occupations associated with four A-horizons. The cultural levels identified in laboratory analyses are palimspsests deposited during multiple occupations.     

Future changes in vegetation and ecosystem function of the Barents Region

The dynamic vegetation model (LPJ-GUESS) is used to project transient impacts of changes in climate on vegetation of the Barents Region. We incorporate additional plant functional types, i.e. shrubs and defined different types of open ground vegetation, to improve the representation of arctic vegetation in the global model. We use future climate projections as well as control climate data for 1981–2000 from a regional climate model (REMO) that assumes a development of atmospheric CO₂-concentration according to the B2-SRES scenario [IPCC, Climate Change 2001: The scientific basis. Contribution working group I to the Third assessment report of the IPCC. Cambridge University Press, Cambridge (2001)]. The model showed a generally good fit with observed data, both qualitatively when model outputs were compared to vegetation maps and quantitatively when compared with observations of biomass, NPP and LAI. The main discrepancy between the model output and observed vegetation is the overestimation of forest abundance for the northern parts of the Kola Peninsula that cannot be explained by climatic factors alone. Over the next hundred years, the model predicted an increase in boreal needle leaved evergreen forest, as extensions northwards and upwards in mountain areas, and as an increase in biomass, NPP and LAI. The model also projected that shade-intolerant broadleaved summergreen trees will be found further north and higher up in the mountain areas. Surprisingly, shrublands will decrease in extent as they are replaced by forest at their southern margins and restricted to areas high up in the mountains and to areas in northern Russia. Open ground vegetation will largely disappear in the Scandinavian mountains. Also counter-intuitively, tundra will increase in abundance due to the occupation of previously unvegetated areas in the northern part of the Barents Region. Spring greening will occur earlier and LAI will increase. Consequently, albedo will decrease both in summer and winter time, particularly in the Scandinavian mountains (by up to 18%). Although this positive feedback to climate could be offset to some extent by increased CO₂ drawdown from vegetation, increasing soil respiration results in NEE close to zero, so we cannot conclude to what extent or whether the Barents Region will become a source or a sink of CO₂.     

Temperature dependence of the water-ice spectrum between 1 and 4 microns: Application to Europa,Ganymede and Saturn's rings

Reflection spectra of water ice from 1 to 4 μm are presented as a function of temperature. It is found that a feature at 6056 cm^?1 changes its intensity sufficiently that it can be used as a spectroscopic measure of the ice temperature. A temperature calibration curve of this feature down to 55 K is developed and is used to determine ice temperatures for the Galilean satellites Europa (95±10 K), Ganymede (103±10 K), and the rings of Saturn (80±5 K). The ice temperatures for the Galilean satellites are lower than their measured brightness temperatures, which can be explained by a higher albedo of the ice covered regions relative to the rest of the satellite and possibly a concentration of the ice near the polar caps.     

Seasonality of Plankton Assemblages in a Temperate Estuary

Abstract. Synoptic measurements of temperature, salinity, nutrients, primary productivity, chlorophyll a, and abundance and composition of phytoplankton, zooplankton, and ichthyoplank-ton were made over an annual cycle on the Peconic Bay estuary (Long Island, New York, USA). There were pronounced seasonal fluctuations in all variables measured. During the warmer season, the plankton was dominated by nanophytoplankton (athecate microflagellates and chlorophytes, short chains of diatoms), small zooplankton (copepod nauplii, copepodites, and adults of small copepod species) and gelatinous carnivores (ctenophores and medusae). During the colder season, the plankton was dominated (in terms of primary productivity and chlorophyll a) by netplankton, larger zooplankton (adult copepods) and fish larvae. The winter bloom of apparent netplankton (> 20 μm fraction) was largely an artifact of the screening method employed, in that long chains of a diatom with small individual cell size (Skeletonema costatum) comprised 84.4–97.8% of the phytoplankton present. There was a significant negative relationship over the year between length of diatom chains and number of smaller zooplankton. For this reason, as well as initiation of the winter bloom during a period of declining levels of both light and zooplankton, inception of the bloom appeared more related to release of zooplankton grazing pressure than to illumination. Temporally offset pulses of ctenophores and other zooplankton during the warmer season suggest substantial predation by ctenophores. Apparent decimation of copepod populations by ctenophore predation in late summer and fall immediately preceeded inception of the winter diatom bloom. Larval Ammodytes americanus were the dominant ichthyoplankton, and these co-occurred in winter with increased abundances of larger adult copepods of species upon which A. americanus is known to feed. With certain modifications the patterns recorded for Peconic Bay corresponded to both of two generalized trophic pathways proposed by Greve & Parsons (1977) for temperate waters: nanoplankton → small zooplankton → gelatinous zooplankton carnivores or netplankton → larger zooplankton → young fish. The former pattern characterized the warmer season, and the latter the colder season. Comparison of patterns in Peconic Bay with those in some other temperate estuarine and coastal waters suggests similarity, particularly for estuaries of the northeastern United States.     

Place-Based Pathways to Proenvironmental Behavior: Empirical Evidence for a Conservation–Recreation Model

This study expands existing models of proenvironmental behavior (PEB) to examine the potentially important and interacting influences of nature-based recreation and sense of place on participation in conservation-oriented activities. We tested hypothesized relationships using a structural equation modeling approach that accounted for common behavioral antecedents within a sample of 1,124 nature-based recreationists and property owners in rural counties of New York, USA. We found that place attachment played an important role in strengthening connections between nature-based recreation and PEB. Birdwatching and hunting participation contributed independently and significantly to PEB, both directly and indirectly through effects on place meanings and place attachment. While birdwatching appeared to influence place attachment by impacting environmental place meanings, hunting exerted similar effects by affecting sociocultural place meanings. Ultimately, our synthesis results in the articulation of a comprehensive conservation–recreation model that could help researchers and practitioners identify and explore novel pathways to PEB.