New materials of lithostrotian titanosaurs (Dinosauria: Sauropoda) from the Upper Cretaceous of central Patagonia     

《Cretaceous Research》2017

Continental Cretaceous deposits exposed in central Patagonia, Argentina, preserve a rich and important record of titanosaurian evolution that spans the entire Upper Cretaceous. Recently, a new lithostragraphic unit, the Lago Colhué Huapi Formation (Coniacian – Maastrichtian), was located in the Golfo San Jorge Basin. Here, we describe new titanosaurian sauropod material from that formation (UNPSJB-Pv 1051). The material consists of a partially articulated left hind limb and disarticulated but associated skeletal elements. They are confidently referred to Titanosauria, and within that clade, to Lithostrotia, probably occupying a derived position. We interpret the bone concentration as an assemblage of hydraulic origin deposited in a fluvial channel. This new material begins the incipient fossil record of the Lago Colhué Huapi Formation, thereby also increasing the titanosaurian diversity of the latest Cretaceous. Additionally, the new titanosaurian enhances evidence in support of strong faunal similarities among the Allen and Marilia formations, chronological equivalents in the Cretaceous of South America. Furthermore, the Lago Colhué Huapi specimen adds to the Late Cretaceous record of Titanosauria and augments our knowledge of central Patagonian terrestrial vertebrate assemblages during this interval.  相似文献   

A new Encephalarteae trunk (Cycadales) from the Cretaceous of Patagonia (Mata Amarilla Formation,Austral Basin), Argentina     

《Cretaceous Research》2017

  相似文献   

Palaeomagnetic study of the El Quemado complex and Marifil formation, Patagonian Jurassic igneous province, Argentina   总被引：1，自引：0，他引：1  

Maria P. Iglesia Llanos  Roberto Lanza  Alberto C. Riccardi  Silvana Geuna  Marinella A. Laurenzi  Raffaella Ruffini † 《Geophysical Journal International》2003,154(3):599-617

  相似文献   

DEGLACIATION OF THE EASTERN FLANK OF THE NORTH PATAGONIAN ICEFIELD AND ASSOCIATED CONTINENTAL-SCALE LAKE DIVERSIONS   总被引：1，自引：1，他引：1  

K.J. TURNER  C.J. FOGWILL  R.D. McCULLOCH  D.E. SUGDEN 《Geografiska Annaler: Series A, Physical Geography》2005,87(2):363-374

ABSTRACT. We examine the deglaciation of the eastern flank of the North Patagonian Icefield between latitudes 46° and 48°S in an attempt to link the chronology of the Last Glacial Maximum moraines and those close to present-day outlet glaciers. The main features of the area are three shorelines created by ice-dammed lakes that drained eastwards to the Atlantic. On the basis of 16 ¹⁴C and exposure age dates we conclude that there was rapid glacier retreat at 15–16 ka (calendar ages) that saw glaciers retreat 90–125 km to within 20 km of their present margins. There followed a phase of glacier and lake stability at 13.6–12.8 ka. The final stage of deglaciation occurred at c. 12.8 ka, a time when the lake suddenly drained, discharging nearly 2000 km³ to the Pacific Ocean. This latter event marks the final separation of the North and South Patagonian Icefields. The timing of the onset of deglaciation and its stepped nature are similar to elsewhere in Patagonia and the northern hemisphere. However, the phase of lake stability, coinciding with the Antarctic Cold Reversal and ending during the Younger Dryas interval, mirrors climatic trends as recorded in Antarctic ice cores. The implication is that late-glacial changes in southern Patagonia were under the influence of the Antarctic realm and out of phase with those of the northern hemisphere.  相似文献   

A GLACIAL STAGE SPANNING THE ANTARCTIC COLD REVERSAL IN TORRES DEL PAINE (51°S), CHILE, BASED ON PRELIMINARY COSMOGENIC EXPOSURE AGES     

C.J. FOGWILL  P.W. KUBIK 《Geografiska Annaler: Series A, Physical Geography》2005,87(2):403-408

ABSTRACT. Initial cosmogenic ¹⁰Be results from a former ice limit in Torres del Paine indicate a shortlived stillstand or readvance of Patagonian ice culminating at 12–15 kyr BP with a mean age of 13.2 ± 0.8 kyr BP. The glacier extended some 40 km beyond the present ice margin and was within 15 km of the presumed Last Glacial Maximum limits. The timing of the glacier stage spans the cooling event recorded in Antarctic ice cores, termed the Antarctic Cold Reversal (14.5–12.9 kyr BP). This result implies that glaciers at these latitudes were out of phase with those in the northern hemisphere; instead they mirrored the climate structure of Antarctica during the last glacial to interglacial transition.  相似文献   

Geophysical Evidence for Terrane Boundaries in South-Central Argentina   总被引：1，自引：0，他引：1  

Carlos J. Chernicoff  Eduardo O. Zappettini   《Gondwana Research》2004,7(4):1105-1116

The geological interpretation of high-resolution aeromagnetic data over the La Pampa province, in central Argentina, in addition to lower resolution magnetic information from the region of the Neuquén and Colorado basins, leads to the definition of the precise boundaries of the Chilenia, Cuyania, Pampia and Patagonia terranes, as well as that of the Río de la Plata Craton, within the study region. The high-resolution aeromagnetic survey data are compared and studied in conjunction with all the available geological information, to produce a map of the solid geology of this region, which is largely covered by Quaternary sediments. A number of structures of different magnitudes, as well as their relative chronology, are also recognized, i.e., regional faults, sub-regional faults, fractures and shear zones, as well as the most conspicuous magnetic fabric of the basement that reflects its main planar structures. Three different basements are distinguished on the basis of their contrasting magnetic character, and are interpreted to represent the Cuyania and Pampia terranes and the Río de la Plata Craton, separated from each other by large-scale discontinuities. In the western part of the study region an additional major discontinuity separates the Chilenia and Cuyania terranes. In the southernmost area studied, WNW-trending structures are predominant, particularly a major NNE-vergent thrust that indicates the truncation of the Cuyania-Pampia suture and is regarded to be related to the possible collision of the Patagonia terrane. An E–W – trending magnetic and gravity anomaly traversing the full extra-Andean Argentine territory, located immediately to the south of 39°S, represents a major structure. The activation of this structure during the Mesozoic gave rise to the Huincul Ridge and marks the interruption of the distinct N-S structures of the Chilenia, Cuyania and Pampia terranes, as well as those of the Río de la Plata Craton, to the north. This E–W represents the suture zone of the Patagonia terrane.  相似文献   

Environmental controls on lambing rate in Patagonia (Argentina): A regional approach     

S.A. Hall  J.M. Paruelo 《Journal of Arid Environments》2006,64(4):713-735

Sheep herd sustainability in Patagonia is limited by reproductive efficiency. As the herds graze on natural vegetation year round, efficiency is constrained by biophysical factors. Our aim was to characterize the environmental controls over effective lambing rate in northwest Patagonia. We related remotely sensed data [surface temperatures and Normal Difference Vegetation Index (NDVI), a surrogate for forage availability] and climatic information to lambing rates. A spatial model explained 63% of the variability in mean lambing rate, based on mean annual NDVI and mean spring surface temperature. The relative inter-annual variability in lambing rates was of similar magnitude to that of annual NDVI. Both lambing rate and NDVI were less variable than climatic factors. Two regional temporal models explained approximately 25% of the variability, based on NDVI values representative of ewes’ nutrition during late gestation and lambing. These models predicted, with 65% and 76% accuracy respectively, the occurrence of better-than-average and worse-than-average yearly lambing rates. These results provided insights into the factors limiting reproduction, and they form the basis for important decision tools for ranch managers. Prediction of lambing rates based on remotely sensed data will reduce the uncertainty and risk in sheep production, increasing the economic sustainability of sheep production.  相似文献   

Contesting sustainable development in Tierra del Fuego     

Peter Klepeis  Paul Laris 《Geoforum》2006,37(4):505-518

Despite wide ranging interpretations of the concept of sustainable development there is growing consensus about the ecological, social, and economic conditions necessary to foster a sustainability transition. In addition to quantitative assessments of sustainability indicators, qualitative process indicators are being identified. For example, active, democratic, and inclusive decision-making are shown to lead to more informed decisions and, presumably, more sustainable use systems. The creation of these conditions, however, often requires bridging lack of mutual trust and scientific uncertainty. And while the ideals of sustainable development suggest that all stakeholders get what they want, without compromise nothing approaching sustainable development is attainable. Obstructing compromise, environmental ideology represents a key remaining hurdle to achieving a middle ground in environment and development debates. In the 1990s, the US-based Trillium Corporation sought to implement a large-scale logging project in Tierra del Fuego, Chile, but was rebuffed by environmentalists who embraced ecotourism as the preferred development option. The case is analyzed in the context of calls to reconsider conceptually nature-society relationships and ideas in sustainability science about which land management systems best match sustainability goals. Findings show that the decision-making process for determining whether or not to implement the logging project was flawed. We explore two implications. First, achieving sustainable development requires a consensus view of nature-society relationships that embraces humanized landscapes. Second, inclusive and effective decision-making about sustainable development necessitates free and open exchange of information, collective learning about regional environment and development, and the identification of compromise positions.  相似文献   

Summer phytoplankton composition and nitrogen limitation of the deep, naturally-acidic (pH∼2.2) Lake Caviahue, Patagonia, Argentina     

Sara G. Beamud  Mónica M. Diaz  Fernando L. Pedrozo 《Limnologica》2007,37(1):37-48

During the warm seasons of 1998-2004, the naturally-acidic (pH∼2.2) Lake Caviahue was sampled for conductivity, temperature, oxygen, light, nutrients, and phytoplankton (density, biomass and chlorophyll a) with a view to studying the summer phytoplankton population changes with relation to environmental factors, as well as the significance of nitrogen limitation on the phytoplankton yield. Lake Caviahue is characterized by its low transparency, CO₂, and N concentration; significant P values; a distinctive vertical distribution of phytoplankton biomass with high values along the water column; and sometimes maximum meta-hypolimnion values. Biodiversity is very low as a result of extreme environmental conditions, Chlorophyceae being the prevailing algae group. Two types of bioassays were carried out to assess nitrogen limitation. For the first bioassay, a solution of ammonium-nitrogen chloride and/or wastewater (rich in ammonium and phosphorus) was used, while one of the lake's sediments was the source of nutrients for the second bioassay. Contrary to the case of acidic mining lakes, N-ammonium proved to be a significant supportive capacity limiting factor as to phytoplankton yield. The present paper provides for the first time information on phytoplankton nitrogen limitation in a naturally-acidic lake.  相似文献   

Climatically induced lake level changes during the last two millennia as reflected in sediments of Laguna Potrok Aike,southern Patagonia (Santa Cruz,Argentina)   总被引：1，自引：0，他引：1  

Torsten?HaberzettlEmail author  Michael?Fey  Andreas?Lücke  Nora?Maidana  Christoph?Mayr  Christian?Ohlendorf  Frank?Sch?bitz  Gerhard?H.?Schleser  Michael?Wille  Bernd?Zolitschka 《Journal of Paleolimnology》2005,33(3):283-302

The volcanogenic lake Laguna Potrok Aike, Santa Cruz, Argentina, reveals an unprecedented continuous high resolution climatic record for the steppe regions of southern Patagonia. With the applied multi-proxy approach rapid climatic changes before the turn of the first millennium were detected followed by medieval droughts which are intersected by moist and/or cold periods of varying durations and intensities. The total inorganic carbon content was identified as a sensitive lake level indicator. This proxy suggests that during the late Middle Ages (ca. AD 1230–1410) the lake level was rather low representing a signal of the Medieval Climate Anomaly in southeastern Patagonia. At the beginning of the Little Ice Age the lake level rose considerably staying on a high level during the whole period. Subsequently, the lake level lowered again in the course of the 20th century.  相似文献