Neodymium isotopic constraints for the origin of Mesoproterozoic felsic magmatism, Gawler Craton, South Australia

1995 ◽  
Vol 32 (4) ◽  
pp. 460-471 ◽  
Author(s):  
Robert A. Creaser
Keyword(s):  
High Temperature ◽  
North America ◽  
Partial Melting ◽  
Large Scale ◽  
South Australia ◽  
Isotopic Analysis ◽  
Thermal Processes ◽  
Western North America ◽  
Archean Crust ◽  
Rifted Margin

Mesoproterozoic felsic magmatism of the Gawler Range Volcanics and Hiltaba Suite granites occurred at 1585–1595 Ma across much of the Gawler Craton, South Australia. Nd isotopic analysis of this felsic magmatism, combined with petrological and geochemical arguments, suggest derivation by partial melting of both Paleoproterozoic and Archean crust. The majority of samples analyzed have Nd isotopic and geochemical characteristics compatible with the involvement of Paleoproterozoic crust stabilized during the 1.85–1.71 Ga Kimban orogeny as sources for the Mesoproterozoic magmatism; others require derivation from sources dominated by Archean rocks. This cycle of Paleoproterozoic crustal stabilization followed by involvement of this crust Mesoproterozoic felsic magmatism is one previously documented from many parts of Mesoproterozoic Laurentia. On the basis of models proposing East Australia–Antarctica to be the conjugate landmass at the rifted margin of western North America, it appears that the voluminous magmatism of South Australia is another example of a typically Mesoproterozoic style of magmatism linked to Laurentia. This Mesoproterozoic magmatism appears temporally linked to regional high-temperature, low-pressure metamorphism of the region, and together with the presence of mantle-derived magmas, implicates the operation of large-scale tectono-thermal processes in the origin of felsic magmatism at 1590 Ma.

scholarly journals Using oxygen and hydrogen stable isotopes to track the migratory movement of Sharp-shinned Hawks (Accipiter striatus) along Western Flyways of North America

PLoS ONE ◽  
2020 ◽  
Vol 15 (11) ◽  
pp. e0226318
Author(s):  
Elizabeth A. Wommack ◽  
Lisa C. Marrack ◽  
Stefania Mambelli ◽  
Joshua M. Hull ◽  
Todd E. Dawson
Keyword(s):  
Stable Isotope ◽  
North America ◽  
Large Scale ◽  
Pacific Coast ◽  
Isotope Analysis ◽  
Western North America ◽  
Migration Routes ◽  
The Pacific ◽  
Accipiter Striatus ◽  
Hydrogen And Oxygen Isotope

The large-scale patterns of movement for the Sharp-shinned Hawk (Accipiter striatus), a small forest hawk found throughout western North America, are largely unknown. However, based on field observations we set out to test the hypothesis that juvenile migratory A. striatus caught along two distinct migration routes on opposite sides of the Sierra Nevada Mountains of North America (Pacific Coast and Intermountain Migratory Flyways) come from geographically different natal populations. We applied stable isotope analysis of hydrogen (H) and oxygen (O) of feathers, and large scale models of spatial isotopic variation (isoscapes) to formulate spatially explicit predictions of the origin of the migrant birds. Novel relationships were assessed between the measured hydrogen and oxygen isotope values of feathers from A. striatus museum specimens of known origin and the isoscape modeled hydrogen and oxygen isotope values of precipitation at those known locations. We used these relationships to predict the origin regions for birds migrating along the two flyways from the measured isotope values of migrant’s feathers and the associated hydrogen and oxygen isotopic composition of precipitation where these feathers were formed. The birds from the two migration routes had overlap in their natal/breeding origins and did not differentiate into fully separate migratory populations, with birds from the Pacific Coast Migratory Flyway showing broader natal geographic origins than those from the Intermountain Flyway. The methodology based on oxygen isotopes had, in general, less predictive power than the one based on hydrogen. There was broad agreement between the two isotope approaches in the geographic assignment of the origins of birds migrating along the Pacific Coast Flyway, but not for those migrating along the Intermountain Migratory Flyway. These results are discussed in terms of their implications for conservation efforts of A. striatus in western North America, and the use of combined hydrogen and oxygen stable isotope analysis to track the movement of birds of prey on continental scales.

scholarly journals Changes toward Earlier Streamflow Timing across Western North America

2005 ◽  
Vol 18 (8) ◽  
pp. 1136-1155 ◽  
Author(s):  
Iris T. Stewart ◽  
Daniel R. Cayan ◽  
Michael D. Dettinger
Keyword(s):  
North America ◽  
Large Scale ◽  
Center Of Mass ◽  
Principal Component ◽  
Warming Trend ◽  
Western North America ◽  
Climate Fluctuations ◽  
Climate Indicators ◽  
Decadal Scale ◽  
Streamflow Timing

Abstract The highly variable timing of streamflow in snowmelt-dominated basins across western North America is an important consequence, and indicator, of climate fluctuations. Changes in the timing of snowmelt-derived streamflow from 1948 to 2002 were investigated in a network of 302 western North America gauges by examining the center of mass for flow, spring pulse onset dates, and seasonal fractional flows through trend and principal component analyses. Statistical analysis of the streamflow timing measures with Pacific climate indicators identified local and key large-scale processes that govern the regionally coherent parts of the changes and their relative importance. Widespread and regionally coherent trends toward earlier onsets of springtime snowmelt and streamflow have taken place across most of western North America, affecting an area that is much larger than previously recognized. These timing changes have resulted in increasing fractions of annual flow occurring earlier in the water year by 1–4 weeks. The immediate (or proximal) forcings for the spatially coherent parts of the year-to-year fluctuations and longer-term trends of streamflow timing have been higher winter and spring temperatures. Although these temperature changes are partly controlled by the decadal-scale Pacific climate mode [Pacific decadal oscillation (PDO)], a separate and significant part of the variance is associated with a springtime warming trend that spans the PDO phases.

scholarly journals Using oxygen and hydrogen stable isotopes to track the migratory movement of Sharp-shinned Hawks (Accipiter striatus) along Western Flyways of North America

2019 ◽  
Author(s):  
Elizabeth A. Wommack ◽  
Lisa C. Marrack ◽  
Stefania Mambelli ◽  
Joshua M. Hull ◽  
Todd E. Dawson
Keyword(s):  
Stable Isotope ◽  
North America ◽  
Large Scale ◽  
Pacific Coast ◽  
Isotope Analysis ◽  
Western North America ◽  
Migration Routes ◽  
The Pacific ◽  
Accipiter Striatus ◽  
Hydrogen And Oxygen Isotope

AbstractThe large-scale patterns of movement for the Sharp-shinned Hawk (Accipiter striatus), a small forest hawk found throughout western North America, are largely unknown. However, based on field observations we set out to test the hypothesis that juvenile migratory A. striatus caught along two distinct migration routes on opposite sides of the Sierra Nevada Mountains of North America (Pacific Coast and Intermountain Migratory Flyways) come from geographically different natal populations. We applied stable isotope analysis of hydrogen (H) and oxygen (O) of feathers, and large scale models of spatial isotopic variation (isoscapes) to formulate spatially explicit predictions of the origin of the migrant birds. Novel relationships were assessed between the measured hydrogen and oxygen isotope values of feathers from A. striatus museum specimens of known origin and the isoscape modeled hydrogen and oxygen isotope values of precipitation at those known locations. We used these relationships to predict the origin regions for birds migrating along the two flyways from the measured isotope values of migrant’s feathers and the associated hydrogen and oxygen isotopic composition of precipitation where these feathers were formed. The birds from the two migration routes had overlap in their natal/breeding origins and did not differentiate into fully separate migratory populations, with birds from the Pacific Coast Migratory Flyway showing broader natal geographic origins then those from the Intermountain Flyway. The methodology based on oxygen isotopes had, in general, less predictive power than the one based on hydrogen. There was broad agreement between the two isotope approaches in the geographic assignment of the origins of birds migrating along the Pacific Coast Flyway, but not for those migrating along the Intermountain Migratory Flyway. These results are discussed in terms of their implications for conservation efforts of A. striatus in western North America, and the use of combined hydrogen and oxygen stable isotope analysis to track the movement of birds of prey on continental scales.

Changes in bird communities throughout succession following fire and harvest in boreal forests of western North America: literature review and meta-analyses

2006 ◽  
Vol 36 (5) ◽  
pp. 1299-1318 ◽  
Author(s):  
Jim Schieck ◽  
Samantha J Song
Keyword(s):  
North America ◽  
Populus Tremuloides ◽  
Boreal Forests ◽  
Large Scale ◽  
Forest Type ◽  
Bird Species ◽  
Bird Communities ◽  
Forest Birds ◽  
Western North America ◽  
Meta Analyses

Within boreal forests of western North America, the dominant large-scale natural disturbance is wildfire. Thus, harvesting that is as similar as possible to fire is expected to best maintain natural bird communities. We reviewed studies of birds (mainly grouse, woodpeckers, and songbirds) from boreal forests of western North America and conducted meta-analyses to compare the similarity of bird communities occurring postfire versus postharvest. We compared the bird communities at five seral stages and also summarized the effects of retaining large live trees at harvest. Bird communities immediately postharvest differed greatly from those postfire. Differences between disturbance types disappeared as the forest regenerated, and both disturbance types became dominated by relatively few bird species in 31- to 75-year-old forests. During the period 76–125 years postdisturbance, old-forest birds became present and bird species richness increased. However, the trajectory of forest succession during this period influenced bird communities; old aspen (Populus tremuloides Michx.), old mixedwood, and old white spruce (Picea glauca Moench (Voss)) forests all had different bird communities. Retention of large live trees in cutblocks resulted in their use by many old-forest birds, but results were not consistent among studies. Although most bird species had clear peaks in abundance in a specific forest type, no species with more than five detections was limited to a single forest type.

Footprints of Atlantic Multidecadal Oscillation in the Low-Frequency Variation of Extreme High Temperature in the Northern Hemisphere

2019 ◽  
Vol 32 (3) ◽  
pp. 791-802 ◽  
Author(s):  
Miaoni Gao ◽  
Jing Yang ◽  
Daoyi Gong ◽  
Peijun Shi ◽  
Zhangang Han ◽  
...  
Keyword(s):  
High Temperature ◽  
North America ◽  
Northern Hemisphere ◽  
Low Frequency ◽  
Atlantic Multidecadal Oscillation ◽  
Frequency Variation ◽  
Eastern Siberia ◽  
Western North America ◽  
Mongolian Plateau ◽  
Extreme High Temperature

The frequency and intensity of extreme high temperature (EHT) in the Northern Hemisphere exhibit remarkable low-frequency (LF) variations (longer than 10 years) in summer during 1951–2017. Five hotspots featuring large LF variations in EHT were identified, including western North America–Mexico, eastern Siberia, Europe, central Asia, and the Mongolian Plateau. The probability density functions show that the higher EHT occurrences over these hotspots in recent decades is consistent with the shifted average and increased variances in daily mean temperature. The common features of the LF variation in EHT frequency over all domains are the remarkable increasing trends and evident decadal to multidecadal variations. The component of decadal to multidecadal variations is the main contribution to the LF variations of temperature in the last century. Further analysis shows that the coherent variability of decadal to multidecadal temperature variations over western North America–Mexico, eastern Siberia, Europe, and the Mongolian Plateau are the footprints of a dominant natural internal signal: the Atlantic multidecadal oscillation. It contributes to the variations in temperature over these hotspots via barotropic circumglobal teleconnection, which imposes striking anomalous pressure over these regions. This study implies that natural internal variability plays an important role in making hotspots more vulnerable to EHT.

Tectonic inheritance at multiple scales during more than two complete Wilson cycles recorded in eastern North America

2018 ◽  
Vol 470 (1) ◽  
pp. 337-352 ◽  
Author(s):  
William A. Thomas
Keyword(s):  
North America ◽  
Large Scale ◽  
Multiple Scales ◽  
Eastern North America ◽  
Transform Faults ◽  
Tectonic Inheritance ◽  
Fault Systems ◽  
Basement Faults ◽  
Iapetus Ocean ◽  
Rifted Margin

AbstractEastern North America holds clear records of two Wilson cycles and hints of two earlier cycles, through which tectonic inheritance is evident at multiple scales. Large-scale transform offsets of rifted margins indicate inheritance through multiple cycles; transform-parallel intracratonic fault systems suggest a transform-parallel fabric in the lithosphere. Rift segments of the continental margins did not inherit the locations of earlier rifts; synrift intracratonic fault systems follow earlier contractional fabrics of supercontinent assembly. Large-scale curves of the Appalachian–Ouachita orogenic belt (closing of the Iapetus Ocean) mimic the shape of the Iapetan rifted margin of Laurentia. Basins along the Iapetan rifted margin reflect inheritance from transform faults in the greater magnitudes of early post-rift thermal subsidence and later synorogenic tectonic loading and flexural subsidence. Older synrift basement faults buttressed the frontal ramps of Appalachian–Ouachita thin-skinned thrust faults. Basement fault blocks and associated synrift stratigraphic variations in the weak layers that host the regional décollement localized transverse alignments of lateral ramps, as well as tectonic thickening of a mud-dominated graben-fill succession in a ductile duplex (mushwad). The many examples of tectonic inheritance attest to the linkages between processes of successive opening and closing of oceans, as well as the break-up and assembly of supercontinents, through successive Wilson cycles.

The Potential of Photoelectrochemical Carbon Sinks

2018 ◽  
Author(s):  
Matthias May ◽  
Kira Rehfeld
Keyword(s):  
Global Warming ◽  
High Temperature ◽  
Greenhouse Gas ◽  
Large Scale ◽  
High Efficiency ◽  
Carbon Sink ◽  
Solar Fuels ◽  
Negative Emissions ◽  
Viable Approach ◽  
Low Sensitivity

Greenhouse gas emissions must be cut to limit global warming to 1.5-2C above preindustrial levels. Yet the rate of decarbonisation is currently too low to achieve this. Policy-relevant scenarios therefore rely on the permanent removal of CO<sub>2</sub> from the atmosphere. However, none of the envisaged technologies has demonstrated scalability to the decarbonization targets for the year 2050. In this analysis, we show that artificial photosynthesis for CO<sub>2</sub> reduction may deliver an efficient large-scale carbon sink. This technology is mainly developed towards solar fuels and its potential for negative emissions has been largely overlooked. With high efficiency and low sensitivity to high temperature and illumination conditions, it could, if developed towards a mature technology, present a viable approach to fill the gap in the negative emissions budget.<br>

The Potential of Photoelectrochemical Carbon Sinks

2018 ◽  
Author(s):  
Matthias May ◽  
Kira Rehfeld
Keyword(s):  
Global Warming ◽  
High Temperature ◽  
Greenhouse Gas ◽  
Large Scale ◽  
High Efficiency ◽  
Carbon Sink ◽  
Solar Fuels ◽  
Negative Emissions ◽  
Viable Approach ◽  
Low Sensitivity

Greenhouse gas emissions must be cut to limit global warming to 1.5-2C above preindustrial levels. Yet the rate of decarbonisation is currently too low to achieve this. Policy-relevant scenarios therefore rely on the permanent removal of CO<sub>2</sub> from the atmosphere. However, none of the envisaged technologies has demonstrated scalability to the decarbonization targets for the year 2050. In this analysis, we show that artificial photosynthesis for CO<sub>2</sub> reduction may deliver an efficient large-scale carbon sink. This technology is mainly developed towards solar fuels and its potential for negative emissions has been largely overlooked. With high efficiency and low sensitivity to high temperature and illumination conditions, it could, if developed towards a mature technology, present a viable approach to fill the gap in the negative emissions budget.<br>

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