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Germán Aguilar Rodrigo Riquelme Joseph Martinod José Darrozes Eric Maire 《地球表面变化过程与地形》2011,36(13):1736-1748
We quantify erosion rates in the higher sectors of the Huasco Valley, in the Main Cordillera of the semi‐arid Andes of Chile, using elevation differences between three successive geomorphic markers (pediments and paleo‐valleys) and the present day valley. Available Ar‐Ar ages of Neogene pediments are used to estimate mean erosion rates for the three periods (16 to 13 My, 13 to 8 My, and following 8 My). The landscape of the Huasco Valley is in a transient state, as indicated by well‐preserved pediment surfaces in interfluves, valleys deeply incised by fluvial and glacial erosion and scarped head‐valleys that represent the current knickzones. Higher erosion rates (45–75 m/My) are calculated for the more recent period (< 8 My) during which deep incision developed compared to previous periods (6–31 m/My). Quantitative data indicate that glaciers had a much higher erosional capability than fluvial activity in the higher sectors of the Main Cordillera. Comparison with erosion rates calculated in other drainage basins of the Chilean Andes suggests that the variability of erosion rates depends on the landscape's transient erosive state. The landscape's geomorphologic response to the uplift of the Main Cordillera results in the retreat of a knickzone, for which retreat velocity depends on precipitation rate pattern and glacial erosion intensity. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Rodrigo Riquelme Grard Hrail Joseph Martinod Reynaldo Charrier Jos Darrozes 《Geomorphology》2007,86(3-4):283-306
We analyze remarkable examples of the large ( 10,000 km2) and local-scale ( 100 km2) landscape forms related to Late Cenozoic geomorphologic evolution of the Andean forearc region in the Southern Atacama Desert. We also consider the continental sedimentary deposits, so-called “Atacama Gravels”, which are related to the degradation of the landscape during the Neogene. Our analysis integrates 1:50,000 field cartography, Landsat TM images observations, 1:1000 sedimentary logging data, and 50 m horizontal resolution topographic data to reconstruct the Late Cenozoic geomorphologic evolution of this region and discuss the factors that control it, i.e., Miocene aridification of the climate and Neogene Central Andean uplift. We determine that the Precordillera was already formed in the Oligocene and most of the present-day altitude of the Precordillera was reached before that time. Afterward, five episodes of geomorphologic evolution can be differentiated: (1) the development of an Oligocene deep incised drainage system cutting the uplifted Precordillera (up to 2000 m of vertical incision) and connecting it to the Ocean; followed by (2) the infilling of deep incised valleys by up to 400 m of Atacama Gravels. This infill started in the Early Miocene with the development of fluvial deposition and finished in the Middle Miocene with playa and playa lake depositions. We propose that playa-related deposition occurs in an endorheic context related to tectonic activity of the Atacama Fault System and Coastal Cordillera uplift. However, the upward sedimentologic variation in the Atacama Gravels evidences a progressive aridification of the climate. Subsequently, we have identified the effects of the Middle–Upper Miocene slow tectonic deformation: the Neogene Andean uplift is accommodated by a tilting or flexuring of the inner-forearc (Central Depression and Precordillera) related to some hundreds of meters of uplift in the Precordillera. This tilting or flexuring results in (3) the Middle Miocene re-opening of the valley network to the Pacific Ocean. Upper Miocene aridification, from arid to hyperarid, induces alluvial fans backfilling in the Central Depression (4) resulting in up to 50 m of Atacama Gravel deposition. Finally, in response to an increase in the rate of tilting, a new phase of vertical incision (up to 800 m in the Precordillera) allows the development of the canyon that crosses the forearc (5). 相似文献
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This study focuses on the effect of oil on periphytic marine microflora on glass surfacesin situ. Two groups of glass slides were used, one with oil and the other without oil. Bacteria, algae and protozoa were counted and periphytic heterotrophic bacteria were isolated. Significant differences in physiological and morphological characteristics of periphytic heterotrophic bacteria on both surfaces of glass slides with and without oil were found. Quantitative differences between the microflora of both groups were also observed. Total number of each group such as bacteria, protozoa and primary producers were significantly affected by the presence of oil. 相似文献
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The large (≈10000 km2) and local-scale (<400 km2) geomorphologic, geomorphometric and field evidence indicates that, from the mid-Miocene onwards, the Atacama Fault System (AFS) accommodated the relative uplift of the western side of the Chilean Coastal Cordillera of the Chañaral region (southern Atacama Desert). The mean regional altitude systematically decreases eastwards crossing the AFS, independent of the lithological characteristics of the substratum cut by this system of faults. Topographic analysis reveals a more incised landscape west of the AFS that, at the local scale, is reported by the distribution of the altitudes (hypsometric curves and integrals) of tributary basins and by the presence of terraces. In the Middle and Upper Miocene, a thick (>300 m) sedimentary succession was deposited east of the AFS. The succession fills previously deep paleovalleys. And it consists of gravel, so-called “Atacama Gravels”, which passes laterally into fine-grained playa related deposits near the AFS. We interpret the deposition of this succession as a result of a blocking closure of the valley flowing from the Precordillera due to the activity on AFS. A pedimentation episode followed sediment deposition and is locally strongly re-incised by the main modern-day river valleys draining the Precordillera. Incision may result from either regional uplift of the forearc, and/or from more localized activity on the AFS. Furthermore, Recent (Quaternary?) tectonic activity on the AFS has been observed which is consistent with a localized relative uplift of the crustal block west of the AFS. 相似文献
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J. Aroba J. A. Grande J. M. Andújar M. L. de la Torre J. C. Riquelme 《Environmental Geology》2007,53(1):135-145
In this article, a set of clustering algorithms based on Fuzzy Logic and Data Mining are applied, allowing to obtain data
in the form of linguistic rules and charts about the behaviour of the Tinto and Odiel river estuary (SW Spain) affected by
Acid Mine Drainage (AMD). In order to provide researchers with no skills on data mining techniques an easy and intuitive interpretation,
we have developed a computer tool based on fuzzy logic that allows immediate qualitative analysis of the data contained in
a data from the estuary water chemical analyses, and serves as a contrast to functioning models previously proposed with classical
statistics. 相似文献
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Silva-Aciares F Zapata M Tournois J Moraga D Riquelme C 《Marine pollution bulletin》2011,62(12):2671-2680
This study reports molecular markers potentially associated with resistance or sensitivity to the impact of copper in juvenile red abalone, Haliotis rufescens, in the north of Chile under experimental conditions. Genomic analysis was made applying subtractive hybridization libraries (SSH) to identify genes up-and down regulated during cooper exposure in abalone over periods of 12 and 168 h exposed to 2.5 and 10 μg/L of Cu+2. Results obtained from the SSH library revealed 368 different sequences regulated by copper, that correspond to eight major physiological functions. The validation of these sequences obtained by SSH as well as their expression kinetics were made by PCR in real time on 14 potential genes regulated by metal stress. This study provides information for the characterization of potential genomic markers that may be used in future environmental monitoring and to investigate new mechanisms of stress to copper in this commercially important marine species. 相似文献
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Exhumation history and timing of supergene copper mineralisation in an arid climate: New thermochronological data from the Centinela District,Atacama, Chile 总被引：1，自引：0，他引：1 
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下载免费PDF全文 Caroline Sanchez Stéphanie Brichau Rodrigo Riquelme Sébastien Carretier Thomas Bissig Cristopher Lopez Constantino Mpodozis Eduardo Campos Vincent Regard Gérard Hérail Carlos Marquardt 《地学学报》2018,30(1):78-85
Supergene copper mineralisation (SCM) processes occur during the unroofing of porphyry copper deposits. However, the geomorphological stage during which the main mineralisation occurs is still under debate. Here, we present 24 new thermochronological data from Cenozoic intrusives and compare them with the evolution of supergene mineralisation from the Centinela Mining District in the Atacama Desert. Our results indicate a two‐step cooling path: a rapid Late Eocene exhumation followed by a slow denudation. Previously published supergene mineralisation ages cluster after the main Upper Oligocene exhumation period. Ours is the first study that establishes the relationship between exhumation and supergene processes on the scale of a single mining district. It confirms that SCM took place during pediplanation, likely a required condition for efficient SCM under arid climatic conditions, in contrast to wet tropical environments where SCM occurs during rapid relief growth but has limited preservation potential. 相似文献
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A review of the impacts of salmonid farming on marine coastal ecosystems in the southeast Pacific 总被引：2，自引：0，他引：2