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61.
Marcelo S. de la Fuente Aldo M. Umazano Juliana Sterli José L. Carballido 《Cretaceous Research》2011,32(4):527-537
A new chelid species (Prochelidella cerrobarcinae nov. sp.) are described from the Aptian-Albian? Puesto La Paloma Member, Cerro Barcino Formation, northern of Chubut Province, Argentina. The basal section of this member, which bears the turtle remains, is composed of tuffaceous mudstones with plane parallel lamination, asymmetrical ripples and a chert intercalation suggesting sub-aqueous deposition in a relatively shallow lacustrine environment. Pr. cerrobarcinae nov. sp. is represented by post-cranial remains of several specimens that not only represents the oldest pleurodiran chelid record in the world but, together with the chelid remains of Albian Lightning Ridge, New South Wales, Australia, indicates that chelid diversification began well before the final fragmentation of southern Gondwana. 相似文献
62.
Severe storms in desert regions, especially along the coastal area of the Chilean desert, produce very destructive mud flows
that last a few hours and constitute the only surface run-off in these events. To date, there is no simple or practical methodology
for assessing such mud flows. Given the settlement of mining fields and creation of desert campgrounds, it is increasingly
necessary to understand how these water and/or mud flows behave in order to develop structural and non-structural mitigation
plans. Thus, herein, we present software known as PVCS, which provides a system for calculating mud volumes after a strong
storm. This hydrological and computer tool allows us to calculate the structure and volume of mud passing through the mouth
of a hydrographic watershed after a desert rainstorm. To use this software, it is necessary to know the hydrological, meteorological,
and morphometric parameters of the watershed under study. These data are entered into a model that estimates the amount of
mud that will pass through the mouth with each hour of rain. Simulations can be done with historical data or data designed
for future events, thereby allowing the preparation of measures to protect people and property. We use the watershed Quebrada
La Cadena to exemplify the use of this software. This drainage basin is located on the western slope of the Chilean Coastal
Range in Antofagasta, a city in northern Chile. Here, rain in June 1991 produced a destructive flood that killed nearly one
hundred people living at the main mouth of the watershed and caused huge economic losses. Data from this catastrophe have
significantly improved the understanding of such flows, and this has been incorporated into the software. The principal value
of PVCS lies in its ability to forecast the volume of mud that will result from a storm and hourly outflows that will pass
through a specific populated area, mining camp, or industrial plant located in the mouth of a watershed of any size. This
information is used to determine the most critical moment, i.e., the time of the largest outflows, which can then be used
to organize timely evacuations to safe places for people, animals, and machines. Moreover, the program is methodologically
valuable since, in order to implement PVCS, the user must structure information in a hydrological way. In summary, this program
simulates different rain scenarios, thereby allowing us to design structural mitigation projects and contingency plans. 相似文献
63.
Juliana?TrochEmail authorView authors OrcID profile Ben?S.?Ellis Axel?K.?Schmitt Anne-Sophie?Bouvier Olivier?Bachmann 《Contributions to Mineralogy and Petrology》2018,173(7):54
The Island Park-Mount Jackson series in the Yellowstone volcanic field, Wyoming (USA), is a suite of rhyolitic domes and lavas that erupted between the caldera-forming eruptions of the Mesa Fall Tuff (1.3 Ma) and the Lava Creek Tuff (0.6 Ma). Combined zircon U/Pb geochronology, Raman spectroscopy, oxygen isotopic and trace elemental compositions document storage conditions of these magmas between consecutive supereruptions. Based on comparison with co-erupted melt compositions and textural criteria, four zircon compositional groups are identified that record different stages along a continuous magmatic evolution from trace element-poor rhyolite at high temperatures to extremely fractionated rhyolite where zircon trace elements are highly enriched (e.g., >?1000 ppm U). These latter zircon domains are dark in cathodoluminescence images and show broadened Raman peaks relative to near-endmember zircon, indicating that substitution of non-stoichiometric trace elements into zircon leads to distortion of the crystal lattice. Some of these zircon domains contain inclusions of U-Th-REE-phases, likely originating from coupled dissolution–reprecipitation of metastable trace element-rich zircon in the presence of a fluid phase. Rhyolite-MELTS simulations indicate that at the conditions required to produce the observed enrichment in trace elements, a fluid phase is likely present. These findings illustrate that zircons can be assembled from a variety of co-existing magmatic environments in the same magma reservoir, including near-solidus volatile-rich melts close to the magmatic–hydrothermal transition. 相似文献
64.
V. Crego-Prieto D. Danancher D. Campo J. Perez E. Garcia-Vazquez A. Roca 《Marine pollution bulletin》2013
Oil spills cause aggressive impacts on marine ecosystems affecting immense areas and the species inhabiting them. If wastes are not cleaned up properly, the remnants may affect local populations for a long time. This work focuses on the long-term impacts of the Prestige spillage that occurred off Galician coast (Spain) in November 2002. Model species were two sympatric flatfish, the megrims Lepidorhombus whiffiagonis and Lepidorhombus boscii. Samples obtained before and nine years after the Prestige accident from affected and unaffected areas were genotyped for six hypervariable nuclear markers and for the mitochondrial D-loop sequence. The results revealed a high proportion of post-F1 interspecific hybrids in the area affected, and also increased intraspecific population differentiation likely due to such localized introgression of foreign genes. These changes suggest the appearance of a hybrid zone following the accident and emphasize the need of paying special attention to potential evolutionary impacts of oil spills. 相似文献
65.
Juliana Maantay 《The Professional geographer》2013,65(3):406-408
The North Carolina Hispanic population has grown at a rapid pace in recent years. Before 1980, the majority of Hispanics in North Carolina were engaged primarily in migrant agricultural work. Hispanics who are part of the new influx are arriving in urban areas and are working at nonagricultural pursuits. Previous research and anecdotal evidence suggest that Hispanic newcomers come from other U.S. jurisdictions and from abroad. Labor migration occurs in response to demand for labor, and labor demand is meditated by employers’ preferences and hiring practices. However, focusing solely on employer demand for labor ignores the role of past U.S. immigration policy and the large growth in services employment in the Sunbelt that have fueled the Hispanic in–migration. This research project explored the attitudes and recruiting behavior of employers in the Triangle region of North Carolina. A newspaper content analysis was undertaken, and interviews were conducted with selected intermediaries and a group of employers. Qualitative analysis of the data collected revealed that these employers utilize the social networks of their immigrant Hispanic employees to recruit new workers. They also use a variety of other recruiting methods to recruit Hispanics both locally and from abroad. If this practice is widespread, it may be fueling the influx of Hispanic immigrants to North Carolina. Employers interviewed extolled the work ethic of Hispanic workers and often bypassed native–born workers, whom they felt were inferior employees. These findings have ramifications for future immigration policy and for the success of welfare–to–work programs. Employer demand for labor is one factor that must be considered when formulating new immigration policy. 相似文献
66.
M.L. Carapezza F. Barberi M. Ranaldi T. Ricci L. Tarchini J. Barrancos C. Fischer D. Granieri C. Lucchetti G. Melian N. Perez P. Tuccimei A. Vogel K. Weber 《Applied Geochemistry》2012
Gas hazard was evaluated in the three most important cold gas emission zones on the flanks of the quiescent Colli Albani volcano. These zones are located above structural highs of the buried carbonate basement which represents the main regional aquifer and the main reservoir for gas rising from depth. All extensional faults affecting the limestone reservoir represent leaking pathways along which gas rises to the surface and locally accumulates in shallow permeable horizons forming pressurized pockets that may produce gas blowout when reached by wells. The gas, mainly composed of CO2 (>90 vol.%), contains appreciable quantities of H2S (0.35–6 vol.%), and both represent a potentially high local hazard. Both gases are denser than air and accumulate near ground where they may reach hazardous concentrations, and lethal accidents frequently occur to animals watering at local ponds. In order to evaluate the rate of degassing and the related hazard, CO2 and H2S diffuse soil flux surveys have been repeatedly carried out using an accumulation chamber. The viscous gas flux of some important discrete emissions has been evaluated and the CO2 and H2S air concentration measured by portable devices and by Tunable Diode Laser profiles. The minimum potential lethal concentration of the two gases (250 ppm for H2S and 8 vol.% for CO2) is 320 times higher for CO2, whereas the CO2/H2S concentration ratio in the emitted natural gas is significantly lower (15–159). This explains why H2S reaches hazardous, even lethal, concentrations more frequently than CO2. A relevant hazard exists for both gases in the depressed zones (channels, excavations) particularly in the non-windy early hours of the day. 相似文献
67.
Ignacio?Torresi Roberto?Perez?XavierEmail author Diego?F.?A.?Bortholoto Lena?V.?S.?Monteiro 《Mineralium Deposita》2012,47(3):299-323
The Alvo 118 iron oxide–copper–gold (IOCG) deposit (170 Mt at 1.0 wt.% Cu, 0.3 g/t Au) lies in the southern sector of the
Itacaúnas Shear Belt, Carajás Mineral Province, along a WNW–ESE-striking, 60-km-long shear zone, close to the contact of the
~2.76-Ga metavolcano-sedimentary Itacaiúnas Supergroup and the basement (~3.0 Ga Xingu Complex). The Alvo 118 deposit is hosted
by mafic and felsic metavolcanic rocks and crosscutting granitoid and gabbro intrusions that have been subjected to the following
hydrothermal alteration sequence towards the ore zones: (1) poorly developed sodic alteration (albite and scapolite); (2)
potassic alteration (biotite or K-feldspar) accompanied by magnetite formation and silicification; (3) widespread, pervasive
chlorite alteration spatially associated with quartz–carbonate–sulphide infill ore breccia and vein stockworks; and (4) local
post-ore quartz–sericite alteration. The ore assemblage is dominated by chalcopyrite (~60%), bornite (~10%), hematite (~20%),
magnetite (10%) and subordinate chalcocite, native gold, Au–Ag tellurides, galena, cassiterite, F-rich apatite, xenotime,
monazite, britholite-(Y) and a gadolinite-group mineral. Fluid inclusion studies in quartz point to a fluid regime composed
of two distinct fluid types that may have probably coexisted within the timeframe of the Cu–Au mineralizing episode: a hot
(>200°C) saline (32.8‰ to 40.6 wt.% NaCl eq.) solution, represented by salt-bearing aqueous inclusions, and a lower temperature
(<200°C), low to intermediate salinity (<15 wt.% NaCl eq.) aqueous fluid defined by two-phase (LH2O + VH2O) fluid inclusions. This trend is very similar to those defined for other IOCG systems of the Carajás Mineral Province. δ
18OH2O values in equilibrium with calcite (−1.0‰ to 7.5‰ at 277°C to 344°C) overlap the lower range for primary magmatic waters,
but the more 18O-depleted values also point to the involvement of externally derived fluids, possibly of meteoric origin. Furthermore, sulphide
δ
34S values (5.1‰ to 6.3‰), together with available boron isotope and Cl/Br–Na/Cl data provide evidence for a significant component
of residual evaporative fluids (e.g., bittern fluids generated by seawater evaporation) in this scenario that, together with
magma-derived brines, would be the main sources of the highly saline fluids involved in the formation Alvo 118 IOCG deposit.
The restricted high temperature sodic alteration, the pervasive overprinting of the potassic alteration minerals by chlorite
proximal to the ore zones, ore breccias with open-space filling textures in brittle structures, microthermometric and stable
isotope data indicate, collectively, that the Alvo 118 IOCG system developed at structurally high levels and may be considered
the shallower representative of the IOCG systems of the CMP. 相似文献
68.
69.
70.
Summary Estimates of hourly global irradiance based on geostationary satellite data with a resolution of several (2 to 10) kilometres
reproduce ground-measured values with a Root Mean Square Error (RMSE) of typically 20% to 25%. The different components of
this RMSE have been enumerated by several authors but, due to the lack of adequate measurements, their respective importance
is not well settled. In the present study we attempt to quantify these components from a practical point of view, that is
from the point of view of users having to rely on time/site specific irradiance data. We conclude that the intrinsic, or “effective”
RMSE is more along the line of 12%. This effective RMSE is the measure of the methodological imprecision (satellite-to-irradiance
conversion models). The remaining part of the overall RMSE is the amount by which spatially averaged satellite-derived estimates
are, by their very nature, bound to differ from ground-measured local insolation.
Received August 15, 1997 Revised March 4, 1998 相似文献