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River Region (river + region)

Distribution by Scientific Domains

Earth and Environmental Science	57%
Humanities and Social Sciences	28%

Selected Abstracts

Chemical U-Th-Pb Monazite Dating of Deformations versus Pluton Emplacement and the Proterozoic History of the Arkansas River Region, Colorado, USA

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 5 2009
Hui CAO
Abstract: Five lengthy periods involving multiple phases of cordierite and andalusite growth were revealed by detailed studies of foliation inflection/intersection axes (FIA) preserved in porphyroblasts in schists from the Arkansas River region in Colorado, USA. The regionally consistent character of the succession of five different FIA trends enabled the relative timing of each FIA with respect to the next to be determined. The FIA succession from first to last is: FIA 1 trending W-E, FIA 2 trending SSW-NNE, FIA 3 trending NNW-SSE, FIA 4 trending NW-SE and FIA 5 trending SW-NE. For four of the FIA sets, samples were found containing monazite grains preserved as inclusions. These were dated on an electron microprobe. The ages obtained concur exactly with the FIA succession, with FIA 1 at 1506 ± 15 Ma, FIA 2 at 1467 ± 23 Ma, FIA 3 at 1425 ± 18 Ma, FIA 4 not dated and FIA 5 at 1366 ± 20 Ma. These ages are directly reflected in a succession of plutons in the surrounding region dated by other isotopic approaches, suggesting that deformation, metamorphism and pluton emplacement occurred together episodically, but effectively continuously, for some 140 Ma. [source]

MODELED REGIONAL CLIMATE CHANGE IN THE HYDROLOGIC REGIONS OF CALIFORNIA: A CO2 SENSITIVITY STUDY,

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 3 2004
Mark A. Snyder
ABSTRACT: Using a regional climate model (RegCM2.5), the potential impacts on the climate of California of increasing atmospheric CO2 concentrations were explored from the perspective of the state's 10 hydrologic regions. Relative to preindustrial CO2 conditions (280 ppm), doubled preindustrial CO2 conditions (560 ppm) produced increased temperatures of up to 4°C on an annual average basis and of up to 5°C on a monthly basis. Temperature increases were greatest in the central and northern regions. On a monthly basis, the temperature response was greatest in February, March, and May for nearly all regions. Snow accumulation was significantly decreased in all months and regions, with the greatest reduction occurring in the Sacramento River region. Precipitation results indicate drier winters for all regions, with a large reduction in precipitation from December to April and a smaller decrease from May to November. The result is a wet season that is slightly reduced in length. Findings suggest that the total amount of water in the state will decrease, water needs will increase, and the timing of water availability will be greatly perturbed. [source]

Yanomami Shamanic Initiation: The Meaning of Death and Postmortem Consciousness in Transformation

ANTHROPOLOGY OF CONSCIOUSNESS, Issue 1 2008
ZELJKO JOKIC
ABSTRACT The main aim of shamanic initiation among the Yanomami people of the Upper Orinoco River region in Venezuela is the metamorphosis of the human body into a cosmic body, or what I term "corporeal cosmogenesis." During the initiatory ordeal, the neophyte undergoes an intense experience of death through dismemberment by the spirits and subsequent rebirth, thus overcoming the human condition and becoming an individual living spirit. But, at the same time, he becomes a "collection" of other spirits who leave their natural habitats,located on the mountaintops and in the forest,and move into the initiate's body, which becomes their abode. As the candidate surrenders his soul and humanness to the spirits, the latter become his personal allies and sources of power while imbuing the shaman's postmortem ego with certain properties that can best be described in holographic terms. After the shaman's biological death, his personal spirits become disembodied again and disperse back into the forest and on the mountaintops. When the shaman dies, his soul multiplies, as each of the disembodied spirits becomes a carrier of the shaman's soul image. In this way, through initiations, the shaman becomes a part of a dynamic cosmic circuity, as his hekura can be called upon to invade the bodies of new shamans, and start a cosmogonic initiatory act anew. [source]

Chemical U-Th-Pb Monazite Dating of Deformations versus Pluton Emplacement and the Proterozoic History of the Arkansas River Region, Colorado, USA

40Ar- 39Ar Dating of Albite and Phlogopite from Porphyry Iron Deposits in the Ningwu Basin in East-Central China and Its Significance

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 2 2004
YU Jinjie
Abstract,40Ar- 39Ar dating of albite from the Meishan and Taocun iron deposits yields plateau ages of 122.90±0.16 Ma and 124.89±0.30 Ma, and isochron ages of 122.60±0.16 Ma and 124.90±0.29 Ma, respectively. Phlogopite from the Zhongshan-Gushan ore field has a plateau age of 126.7±0.17 Ma and an isochron age of 127.21±1.63 Ma. Analysis of regional geodynamic evolution of the middle-lower Yangtze River region suggests that the porphyry iron deposits were formed as a result of large-scale lithosphere delamination and strong sinistral strike-slip movement of the Tancheng-Lujiang fault zone. The copper, molybdenum and gold deposit system in the middle-lower Yangtze River region was formed during the stress transition period of the eastern China continent. [source]

Spatial and temporal variations in bank erosion on sand-bed streams in the seasonally wet tropics of northern Australia

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 9 2006
M. J. Saynor
Abstract Bank erosion rates and processes across a range of spatial scales are poorly understood in most environments, especially in the seasonally wet tropics of northern Australia where sediment yields are among global minima. A total of 177 erosion pins was installed at 45 sites on four sand-bed streams (Tributaries North and Central, East Tributary and Ngarradj) in the Ngarradj catchment in the Alligator Rivers Region. Bank erosion was measured for up to 3·5 years (start of 1998/99 wet season to end of 2001/02 wet season) at three spatial scales, namely a discontinuous gully (0·6 km2) that was initiated by erosion of a grass swale between 1975 and 1981, a small continuous channel (2·5 km2) on an alluvial fan that was formed by incision of a formerly discontinuous channel between 1964 and 1978, and three medium-sized, continuous channels (8·5,43·6 km2) with riparian vegetation. The bank erosion measurements during a period of average to above-average rainfall established that substantial bank erosion occurred during the wet season on the two smaller channels by rapid lateral migration (Tributary Central) and by erosion of gully sidewalls due to a combination of within-gully flows and overland flow plunging over the sidewalls (Tributary North). Minor bank erosion also occurred during the dry season by faunal activity, by desiccation and loss of cohesion of the sandy bank sediments and by dry flow processes. The larger channels with riparian vegetation (East Tributary and Ngarradj) did not generate significant amounts of sediment by bank erosion. Deposition (i.e. negative pin values) was locally significant at all scales. Bank profile form and channel planform exert a strong control on erosion rates during the wet season but not during the dry season. Copyright © 2006 Commonwealth Government of Australia. [source]

A Strategic Framework for Monitoring Coastal Change in Australia's Wet-dry Tropics , Concepts and Progress

GEOGRAPHICAL RESEARCH, Issue 2 2009
C. MAX FINLAYSON
Abstract A strategic framework for monitoring natural and human-induced change in the coastal plains of the Alligator Rivers Region in the wet-dry tropics of northern Australia is presented. The framework also supports refinement of methods used to monitor the vulnerability of coastal areas to change, including human-induced climate change and sea-level rise. The information derived through the framework can be used to assess scenarios, highlight the potential significance and implications of changes, and assist land managers formulate management responses. The framework incorporates several large-scale studies for monitoring atmospheric and hydrodynamic processes as well as mapping and monitoring projects specific to environmental change in the freshwater wetlands and the floodplains of the Region. Monitoring is proposed to address processes influencing the stability and rate of change of the floodplain environments. These include large-scale processes, such as inter-annual variability in weather conditions affecting the morphology of the coastal plains, shoreline and riverbank stabilisation, headward expansion of tidal creeks, and salinisation of freshwater basins. Information management is also addressed, and a Geographic Information System structure proposed for effective data collation, analysis and management. The information management system will facilitate data sharing and participation of multiple agencies and organisations interested in coastal change, especially where a landscape perspective or whole ecosystem approach is advocated. [source]