Results 1 - 10 of 514
Results 1 - 10 of 514. Search took: 0.026 seconds
|Sort by: date | relevance|
[en] A series of faults have recently been identified which cut a folded succession of stratified alluvial deposits located along the north side of the new River Valley between Pembroke and Pearisburg in Giles County, Virginia. Although the age of neither the faults nor the sediments is currently known, the unlithified nature of the alluvial deposits suggests that both are, geologically, relatively recent (Tertiary or Quaternary). The faults are regarded by the authors as being of considerable potential importance to both the assessment of seismic hazard and to the present understanding of fault development in this section of the Valley and Ridge Province as they would appear to indicate the, at least local occurence, of geologically recent near surface faulting. The occurrence of faulting in these geologically recent sediments was first detected during excavation for land-fill material in early 1992 when two extensional faults were exposed on land owned by Mr Arnold Bostic of Pembroke, Virginia. the authors became aware of these newly exposed faults in late May 1992 and have since carried out a detailed analysis of the near surface folding and faulting of the sediments under Nuclear Regulatory Commission Contract No. NRC-04-85-121. This analysis has involved the excavation of five bench-type exposures (above road level) and one trench (below road level). Reconaissance geophysical surveys have also been undertaken in an attempt to trace to depth the structures revealed in these temporary exposures
[en] In southern Uruguay there are several known occurrences of base metal sulphide mineralization within an area of Precambrian volcanic sedimentary rocks. Regional geochemical stream sediment reconnaissance surveys revealed new polymetallic anomalies in the same stratigraphic zone. Geochemical interpretation of multi-element data from a soil and stream sediment survey carried out in one of these anomalous areas is presented.
[en] The early sixteenth century century was crucial to Spain as a new government at the European level was born, after completion of the “Reconquista”, in a very competitive political world and an innovative movement in all the social orders known as Renaissance. Addressing these requirements would have required an internal, political, economic and administrativly intense approach, along with a suitable external strategy level that corresponded to Spain in Europe. But Spain had just finished a war of 700 years, bringing the classic problems of the Middle Ages without having an economic financial or industrial or commercial infrastructure that would serve to support this great transformation. The strategic decision of ocean travel, the only possible way for Spainish expansion by the Catholic Monarchs, had an unexpected success as it gave access to the Indies at the first attempt, giving great hope for the Crown and their impoverished subjects of acquiring wealth, given the enduring legends about the Far East. The Discovery is a single event but the process of colonization or conquest requires an approach for which Spain was not ready, due to inexperience, ignorance and uncertainty of the new territories and their remoteness, so that the beginnings were not easy. However at the very beginning of the new 1502 century the first effective way to manage the new territory with Governor General Nicolás de Ovando in Hispaniola was found, and applied immediately to gold mining, exploiting deposits of alluvial placers. This intense mining activity lasted uninterruptedly until 1515, then went down to almost nothing in 1520, when there were other more profitable and productive alternatives mainland. During the years of production supplied by the “quinto real” or royal fifth (a 20% tax), tons of gold were sent to the Crown, constituting the financial guarantee of the continuity of the Discovery and covering the financial demands of state policies, which coincidentally fell when King Ferdinand died, in early 1516.
[es]Los primeros años de la colonización del Nuevo Mundo, después de la euforia del Descubrimiento, fueron años muy difíciles, por la incertidumbre, la inexperiencia y el incumplimiento de las expectativas, tanto para la Corona como para los colonos. Pero La Española, constituida en cabeza de puente, fue capaz de dar una respuesta satisfactoria bajo el gobierno de Nicolás de Ovando (1502-1509) con una minería de oro de resultados espectaculares pudiendo cumplimentar las demandas esperadas y garantizar la continuidad económica del Descubrimiento. Los cronistas de la época recogen de distinta forma esta minería, ilustrándonos con los métodos de laboreo, ubicación, problemas de explotación, etc., mostrando la transcendencia de su actividad. Sacando a la luz estos datos, con un análisis técnico del complejo sistema productivo, podemos dar una imagen más real que justifique su evolución y valore en su medida el esfuerzo realizado por aquellos mineros americanos
[en] Laboratory and field studies were performed for the determination of a calibration curve of a neutron probe in three different kinds of soils: Red Yellow PODZOLIC, LITOLIC and ALLUVIAL, in the last one laboratory studies were done to determine local humidity on the calibration curve parameters. (A.C.A.S.)
[pt]Foram conduzidos estudos em laboratorio e em campo para determinacao das curvas de calibracao de uma sonda de neutrons, em tres solos diferentes, PODZOLICO VERMELHO AMARELO, LITOLICO e ALUVIAL. Neste ultimo foram efetuados estudos em laboratorio para determinar a influencia da unidade inicial sobre os parametros da curva de calibracao. (A.C.A.S.)
[en] Fine-grained sandstones of Permian alluvial fan deposits from three Nagra boreholes (Weiach, Riniken, Kaisten) and an exploration well, drilled at Wintersingen are clast supported, moderately sorted arkosic greywackes containing typically 2-20 % clayey matrix. Petrographic studies indicate that the origin of this clayey matrix is postdepositional. Mechanical infiltration of fines and diagenetic reddening of detrital and authigenic iron oxides are the earliest recorded events. Additionally, nodular calcites of calcrete origin and fibrous illitic clays are also ascribed to the eogenetic environment. The present strong compaction fabric results from general lack of eogenetic framework supporting cements. During mesogenesis, secondary porosity was generated through partial removal of early calcite. At the same time, a first generation of syntaxial quartz cementation and a subsequent fibrous illite authigenesis took place. Leaching of detrital K-feldspars post-dating compaction is recorded throughout the studied boreholes. The following burial diagenetic events differ between the various boreholes: in Weiach and Wintersingen kaolinite, illite, prismatic quartz and ankerite/siderite are recorded; in Riniken K-feldspar, illite, prismatic quartz and dolomite developed; whilst in Kaisten K-feldspar and microcrystalline quartz-cement dominate. These differences reflect the chemistry, pH and ionic strength of the pore fluids. Filling of veins by dolomite/ankerite, iron-rich and subsequent iron-poor calcite is the latest recorded event. (author) 21 refs., 10 figs., 1 tab
[en] The outcroping deposits in the ravines of the Conlara River are dominated by silt with subordinated and variable percentages of sand and clays. In the section that is described, at the south of the town of Santa Rosa del Conlara, these materials have been deposited responding generally climatic changing conditions. The base of the profile, assigned to the late Pleistocene, contains extint fauna of the Lujanense and a datation of 8950 B.P., and it is represented by fluvial sandy gravels. The overlaying succession, assigned to the Holocene, shows an intercalation of horizons generated by eolic-loessic deposits and deposits with development of pedogenetic processes. The whole succession shows characteristic of corresponding to a vegetated plain, next to the river flood plain. The discriminated horizons are the result of a detailed sampling and the representation of range parameters of the same ones, in function of the depth, this last one oscillates between 6 and 8 meters. The quaternary deposits of the region, support indistinctly as on the crystalline basement of San Luis range, as on the calcretes assigned to the Neogene
[es]Los depositos aflorantes en las barrancas del rio Conlara, estan dominados por limos con porcentajes subordinados y variables de arenas y arcillas. En la seccion que se describe, al sur de la localidad de Santa Rosa del Conlara, dichos materiales han sido depositados respondiendo a condiciones cambiantes, generalmente climaticas. La base del perfil, asignada al Pleistoceno tardio, contiene fauna extinta del Lujanense y un fechado de 8950 A.P., y esta representada por gravas arenosas fluviales. La sucesion suprayacente, asignada al Holoceno, muestra una intercalacion de horizontes generados por depositos eolicos-loessicos y depositos con desarrollo de procesos de pedogenesis. Toda la sucesion muestra caracteristicas de corresponder a una planicie vegetada, proxima a la llanura de inundacion de un rio. Los horizontes discriminados responden a un muestreo detallado y representacion de los parametros de rango de los mismos, en funcion de la profundidad, esta ultima oscila entre 6 y 8 metros. Los depositos cuaternarios de la region, apoyan indistintamente tanto sobre el basamento cristalino de la sierra de San Luis, como sobre los calcretes asignados al Neogeno
[en] The mineralogy of matrix fines in alluvium from borehole U11g, expl. 1, north of Frenchman Flat, Nevada Test Site, has been examined for evidence of past variations in water table elevation. Although an abundance of zeolite and slightly expanded basal spacings in smectite clays suggest effects of increased hydration of material up to 50 m above the present water table, these differences might also be related to provenance or environment of deposition. However, the relative uniformity of clay hydration properties in the 50 meters above the current water table suggests long-term stability near the present level, perhaps through most of the Quaternary