The lithology of Ogallala gravels and hunter‐gatherer procurement strategies along the Southern High Plains eastern escarpment of Texas,USA     

Stance Hurst  Eileen Johnson  Zaneta Martinez McCoy  Doug Cunningham 《Geoarchaeology》2010,25(1):96-121

Ogallala gravels are an important lithic material source for stone tool manufacture across the Great Plains. The lithology of eight gravel sample locations along the eastern escarpment of the Southern High Plains has been examined to quantify the composition and variability in Ogallala deposits. In addition, three Ogallala gravel quarry sites have been analyzed to determine how the lithology of Ogallala gravels influenced procurement and tool production strategies. Results indicate deposits of Ogallala gravels differ in their composition related to their position on the landscape, and the types of rocks vary by size and shape. Investigation of the quarry sites has revealed that the lithology of Ogallala gravels had an impact on testing and the initial stages of lithic reduction. Different rock types, however, may have more of an influence on later stages of tool manufacture at nearby campsites and other locations where Ogallala gravels are not as dense. © 2009 Wiley Periodicals, Inc.  相似文献   

Application of multi-isotope ratios to study the source and quality of urban groundwater in Metro Manila,Philippines   总被引：1，自引：0，他引：1  

Takahiro Hosono  Fernando Siringan  Tsutomu Yamanaka  Yu Umezawa  Shin-ichi Onodera  Takanori Nakano  Makoto Taniguchi 《Applied Geochemistry》2010

  相似文献   

Extreme events and disasters: a window of opportunity for change? Analysis of organizational,institutional and political changes,formal and informal responses after mega-disasters   总被引：3，自引：3，他引：0  

J. Birkmann  P. Buckle  J. Jaeger  M. Pelling  N. Setiadi  M. Garschagen  N. Fernando  J. Kropp 《Natural Hazards》2010,55(3):637-655

Disaster associated with natural hazards can lead to important changes—positive or negative—in socio-ecological systems. When disasters occur, much attention is given to the direct disaster impacts as well as relief and recovery operations. Although this focus is important, it is noteworthy that there has been little research on the characteristics and progress of change induced by disasters. Change, as distinct from impacts, encompasses formal and informal responses to disaster events and their direct and indirect impacts. While smaller disasters do not often lead to significant changes in societies and organizational structures, major disasters have the potential to change dominant ways of thinking and acting. Against this background, the article presents an analytical framework for distinguishing change from disaster impacts. Drawing from research in Sri Lanka and Indonesia, formal and informal changes after the Indian Ocean Tsunami of 2004 are examined and discussed against the background of the conceptual framework. The changes examined range from the commencement of the peace process in Aceh, Indonesia, to organizational and legal reforms in Sri Lanka. The article concludes that change-making processes after disasters need to be understood more in depth in order to derive important strategic policy and methodological lessons learned for the future, particularly in view of the increasing complexity and uncertainty in decision making due to climate change.  相似文献   

Estimation of aquifer hydraulic parameters from surface geophysical measurements: a case study of the Upper Cretaceous aquifer, central Sinai, Egypt     

Usama Massoud  Fernando Santos  Mohamed A. Khalil  Ayman Taha  Abbas M. Abbas 《Hydrogeology Journal》2010,18(3):699-710

The integration of geophysical data with direct hydrogeological measurements can provide a minimally invasive approach to characterize the subsurface at a variety of resolutions and over many spatial scales. The field of hydrogeophysics has attracted much attention during the last two decades. In this domain, the geophysical data inverted to geophysical models are interpreted in terms of the hydrogeology to serve as a basis for the definition of hydraulic models in the areas of interest. The hydraulic conductivity (K) value measured in a reference borehole has been combined with the electrical conductivity obtained from nearby geo-electromagnetic sounding data in the Cenomanian (Upper Cretaceous) aquifer, central Sinai, Egypt. The resulting relation was interpreted with Dar Zarrouk parameters to infer the transmissivity variations at other vertical electrical sounding locations, where K values are unknown. Coincident transient electromagnetic data have been adopted to increase accuracy while interpreting the aquifer geoelectrical properties. The results indicate that the transmissivity values in the aquifer of interest vary from 2,446 to 9,694 m²/day, and K varies from 12.9 to 57.0 m/day throughout the studied area.  相似文献   

Reply to the comment by Michard et al. on “Tectonic relationships of Southwest Iberia with the allochthons of Northwest Iberia and the Moroccan Variscides”     

José Fernando Simancas  Antonio Azor  David Martínez-Poyatos  Abdelfatah Tahiri  Hassan El Hadi  Francisco González-Lodeiro  Andrés Pérez-Estaún  Ramón Carbonell 《Comptes Rendus Geoscience》2010,342(2):175-177

  相似文献   

Catchment precipitation processes in the San Francisco valley in southern Ecuador: combined approach using high-resolution radar images and in situ observations     

Andreas Fries  Rütger Rollenbeck  Fabian Bayer  Victor Gonzalez  Fernando Oñate-Valivieso  Thorsten Peters  Jörg Bendix 《Meteorology and Atmospheric Physics》2014,126(1-2):13-29

The precise estimation of precipitation quantities in tropical mountain regions is in great demand by ecological and hydrological studies, due to the heterogeneity of the rainfall distribution and the lack of meteorological station data. This study uses radar images and ground station data to provide the required high-resolution precipitation maps. Also wind data are taken into account, due to its influence on the precipitation formation and to demonstrate the relation between synoptic wind, topography and the precipitation distribution inside small mountain valleys. The study analyses the rainfall distribution and amounts of 4 days inside the San Francisco Valley, a small catchment in the tropical Andes of southern Ecuador, representing different seasons and the typical atmospheric flows, which are correlated to the annual precipitation map. The results show that the rainfall distribution and amounts are generally defined by the wind direction and velocity, besides the topographic location in relation to the main barriers and pathways. The dominant wind direction causes a division of the catchment in a wetter eastern and a dryer western part. Moreover, the annual seasons are reversed; the main rainy season for the eastern part occurs between June and August, while the western part reaches the precipitation maximum between January and March. This may have influence on the species composition at the different slopes and the annual hydrological cycle inside the catchment.  相似文献   

Assessment of uncertainties in the response of the African monsoon precipitation to land use change simulated by a regional model     

Samson Hagos  L. Ruby Leung  Yongkang Xue  Aaron Boone  Fernando de Sales  Naresh Neupane  Maoyi Huang  Jin-Ho Yoon 《Climate Dynamics》2014,43(9-10):2765-2775

Land use and land cover (LULC) over Africa have changed substantially over the last 60 years and this change has been proposed to affect monsoon circulation and precipitation. This study examines the uncertainties of model simulated response in the African monsoon system and Sahel precipitation due to LULC change using a set of regional model simulations with different combinations of land surface and cumulus parameterization schemes. Although the magnitude of the response covers a broad range of values, most of the simulations show a decline in Sahel precipitation due to the expansion of pasture and croplands at the expense of trees and shrubs and an increase in surface air temperature. The relationship between the model responses to LULC change and the climatologists of the control simulations is also examined. Simulations that are climatologically too dry or too wet compared to observations and reanalyses have weak response to land use change because they are in moisture or energy limited regimes respectively. The ones that lie in between have stronger response to the LULC changes, showing a more significant role in land–atmosphere interactions. Much of the change in precipitation is related to changes in circulation, particularly to the response of the intensity and latitudinal position of the African Easterly Jet, which varies with the changes in meridional surface temperature gradients. The study highlights the need for measurements of the surface fluxes across the meridional cross-section of the Sahel to evaluate models and thereby allowing human impacts such as land use change on the monsoon to be projected more realistically.  相似文献   

Lateral variations in tectonic style across cross-strike discontinuities: an example from the Central Apennines belt (Italy)     

Sara Satolli  Paolo Pace  Mauro Gabriele Viandante  Fernando Calamita 《International Journal of Earth Sciences》2014,103(8):2301-2313

In foreland thrust belts, abrupt lateral changes in tectonic style, structural–stratigraphic features, and topography usually occur across cross-strike faults. The Central Apennines of Italy offer an exceptional scenario of lateral variations in tectonic setting. Here, the Sangro Volturno oblique thrust ramp (SVOTR) represents the outer thrust front of the Pliocene–Quaternary foreland thrust system, confining southward the axial culmination of the orogen that occurs in the Central Apennines. We present an interpretation of the Pliocene–Quaternary evolution of this cross-strike fault through an integrated dataset including structural-geological mapping and subsurface onshore seismic reflection profiles. The interpretation of the structural framework is augmented by the analysis of low-temperature thermochronometers from 32 new sites extending across the subsurface transverse structure. As evidenced by seismic line interpretation, the localization and development of the SVOTR have been influenced by inherited extensional faults within a positive inversion tectonics context. The regional distribution of the maximum paleotemperature values across the SVOTR constrains the original extent of the allochthonous thrust sheet over all its hanging-wall and footwall blocks. The Pliocene–Quaternary thrusting and inversion of SVOTR caused the strong hanging-wall uplift, which brought to the complete erosion of the allochthonous units and the exhumation of the Adria units. The integrated analysis of low-temperature thermochronometers and structural evidence as applied in the study case can define the role of major cross-strike discontinuities in foreland thrust belts, by constraining and verifying their tectonics inversion significance and the amount of related exhumation.  相似文献   

Zinc and sulfur isotope variation in sphalerite from carbonate-hosted zinc deposits,Cantabria, Spain   总被引：2，自引：0，他引：2  

Jan Pašava  Fernando Tornos  Vladislav Chrastný 《Mineralium Deposita》2014,49(7):797-807

We studied zinc and sulfur isotopes and the chemical composition of sphalerite samples from Picos de Europa (Aliva mine) and sphalerite and hydrozincite samples from La Florida mine, two carbonate-hosted Mississippi Valley-type (MVT) deposits located in northern Spain; despite being close, they are hosted in carbonatic rocks of different ages, Lower Carboniferous and Lower Cretaceous, respectively. The two generations of sphalerite at Picos de Europa show different δ⁶⁶Zn values (stage 1 sphalerite +0.24 per mil and stage 2 sphalerite from ?0.75 to +0.08 per mil). Both generations also differ in the sulfur isotope composition (stage 1 has δ³⁴S?=?+6.6 and stage 2 has δ³⁴S?=??0.9 to +2.9 per mil) and the chemical composition (stage 1 sphalerite, compared to stage 2 sphalerite, is significantly enriched in Pb, As, Mn, Sb, slightly enriched in Ag, Ni, and Cu and depleted in Co, Ga, Tl, Te, Ge, and Sn). We suggest that Zn isotope fractionation was controlled predominantly by pH and T changes. High Zn isotope values reflect rapid precipitation of sphalerite from higher-temperature acidic fluids that carried Zn mostly as chloride species after interaction with carbonate rocks while lower Zn isotope values most likely resulted from a longer precipitation process from fluid at higher pH and decreasing T that carried dominantly Zn sulfide species. At La Florida, sphalerite samples show light ⁶⁶Zn-depleted signatures with δ⁶⁶Zn values from ?0.80 to ?0.01 per mil (mostly between ?0.80 and ?0.24 per mil) and δ³⁴S values from +10.7 to +15.7 per mil without any relationship between the δ⁶⁶Zn and δ³⁴S values. Here, the variation in Zn isotope values is interpreted as related to mixing of fluids from two reservoirs. The Zn was carried by a single deep-seated and higher T (~250–320 °C) fluid, and precipitation took place after mixing with a connate S-rich fluid in a system with mH₂S?>?mZn²⁺ as a result of change in pH, T, and Zn predominant species. The light δ⁶⁶Zn accompanied by heavy δ³⁴S values resulted from fractionation of Zn aqueous sulfides at near-neutral pH and decreasing T. Hydrozincite samples show much heavier δ⁶⁶Zn values (+0.21 to +0.33 per mil), consistent with fractionation during supergene processes.  相似文献   

Late Cretaceous porphyry copper mineralization in Sonora,Mexico: Implications for the evolution of the Southwest North America porphyry copper province   总被引：1，自引：0，他引：1  

Fernando Barra  Victor A Valencia 《Mineralium Deposita》2014,49(7):879-884

Two porphyry Cu-Mo prospects in northern Sonora, Mexico (Fortuna del Cobre and Los Humos) located within the southwestern North American porphyry province have been dated in order to constrain the timing of crystallization and mineralization of these ore deposits. In Fortuna del Cobre, the pre-mineralization granodiorite porphyry yielded an U-Pb zircon age of 76.5?±?2.3 Ma, whereas two samples from the ore-bearing quartz feldespathic porphyry were dated at 74.6?±?1.3 and 75.0?±?1.4 Ma. Four molybdenite samples from Los Humos porphyry Cu prospect yielded a weighted average Re-Os age of 73.5?±?0.2 Ma, whereas two samples from the ore-bearing quartz monzonite porphyry gave U-Pb zircon ages of 74.4?±?1.1 and 74.5?±?1.3 Ma, showing a Late Cretaceous age for the emplacement of this ore deposit. The results indicate that Laramide porphyry Cu mineralization of Late Cretaceous age is not restricted to northern Arizona as previously thought and provide evidence for the definition of NS trending metallogenic belts that are parallel to the paleo-trench. Porphyry copper mineralization follows the inland migration trend of the magmatic arc as a result of the Farallon slab flattening during the Laramide orogeny.  相似文献