Chaines andines et chaines alpines; regard sur la geologie de la Cordillere des Andes au parallele de l'Argentine moyenne

1966 ◽  
Vol S7-VIII (7) ◽  
pp. 1050-1070 ◽  
Author(s):  
Jean Aubouin ◽  
Angel V. Borrello
Keyword(s):  
Tectonic Evolution ◽  
Quaternary Period ◽  
Alpine Orogeny ◽  
Mountain Ranges ◽  
Terrigenous Sediments ◽  
The Andes ◽  
Reverse Faulting ◽  
Thrust Sheets

Abstract The tectonic evolution of the Andes was generally contemporaneous with the Alpine orogeny (Mesozoic-Tertiary). Pre-Andean tectonic cycles (Hercynian) involved Infracambrian and Paleozoic sediments. Comparison of the Andean cycle with the Alpine cycle shows a similar evolution in three major periods: a Mesozoic period characterized by strong compressional movements during which the thick sediments of the Chilean slopes were thrust over the relatively thin sediments of the Argentine slopes; an Eocene-Oligocene-Miocene period characterized by the deformation of terrigenous formations as a result of andesitic volcanism and reverse faulting; and a Plio-Quaternary period marked by basalt flows and the accumulation of thick terrigenous sediments in faulted, deformed basins. The absence of flysch deposits, ophiolites, major thrust sheets, and widespread metamorphism in the Andes, however, distinguishes them from the Alpine ranges. Thus, two main types of pericratonic mountain ranges (as opposed to intracratonic ranges) should be differentiated: precursory (or Andean) ranges developed on the periphery of continents but within their margins and geosynclinal (or Alpine) ranges part of which are extracratonic.

The striking endemism pattern of the species-richest snake genus Atractus (Dipsadidae: Serpentes) highlights the hidden diversity in the Andes

2021 ◽  
pp. 1-12
Author(s):  
Andrés D. Pomar-Gómez ◽  
Paulo Cordeiro ◽  
Thaís B. Guedes ◽  
Paulo Passos
Keyword(s):  
Atlantic Forest ◽  
Scientific Literature ◽  
Species Range ◽  
Museum Specimens ◽  
Mountain Ranges ◽  
The Andes ◽  
Colombian Andes ◽  
Methodological Approaches ◽  
Endemic Areas ◽  
Forest Mountain

Abstract The distribution of the highly diversified and species-rich snake genus Atractus was assessed in search for endemism areas. The dataset of 6000 museum specimens was used to run an Endemicity Analyses in order to identify areas of biogeographic relevance for the genus Atractus. By using distinct methodological approaches and modifying the size and shape of grid cells we obtained a better adjustment to each species range, taking into account species distributed along the Andean and Atlantic Forest mountain ranges or certain vegetation constraints. Three scales of endemism were observed: micro endemic areas, represented by three different regions; intermediate sized endemic areas, represented by nine different regions; and macro-endemic areas, represented by four different provinces. Although most assessed regions corroborate well-defined biogeographic units according to the scientific literature, some, mainly located in the Colombian Andes, are not regularly considered in biogeographic syntheses carried out for vertebrates. Methodological approaches, along with a well curated database and taxonomic accuracy, may significantly influence the recovery of endemism areas, mainly considering mountain topography and local niche structure. The results present herein highlight the relevance of three Colombian Cordilleras, in order to completely understand Neotropical biota patterns of distribution. It is important to note that a well-resolved taxonomy represents both the framework and the first step toward a comprehensive biographical synthesis reducing Wallacean shortfalls in biodiversity.

New evidence of glacier surges in the Central Andes of Argentina and Chile

2018 ◽  
Vol 42 (6) ◽  
pp. 792-825 ◽  
Author(s):  
Daniel Falaschi ◽  
Tobias Bolch ◽  
Maria Gabriela Lenzano ◽  
Takeo Tadono ◽  
Andrés Lo Vecchio ◽  
...  
Keyword(s):  
Satellite Imagery ◽  
Remote Sensing Data ◽  
Central Andes ◽  
Aerial Images ◽  
Mountain Ranges ◽  
The Andes ◽  
Digital Elevation ◽  
Heterogeneous Behavior ◽  
Elevation Changes ◽  
Glacier Surges

In contrast to the large surge-type glacier clusters widely known for several mountain ranges around the world, the presence of surging glaciers in the Andes has been historically seen as marginal. The improved availability of satellite imagery during the last years facilitates investigating of glaciers in more detail even in remote areas. The purpose of the study was therefore to revisit existing information about surge-type glaciers for the Central Andes of Argentina and Chile (32° 40′–34° 20′ S), to identify and characterize possible further surge-type glaciers, providing new insights into the mass balance and evolution of the velocity of selected glaciers during the surge phase. Based on the analysis of 1962–2015 satellite imagery, historical aerial images, differencing of digital elevation models and a literature survey, we identified 21 surge-type glaciers in the study area. Eleven surge events and six possible surge-type glaciers were identified and described for the first time. The estimation of annual elevation changes of these glaciers for the 2000–2011 period, which encompasses the latest surge events in the region, showed heterogeneous behavior with strongly negative to positive surface elevation change patterns (−1.1 to +1.0 m yr−1). Additionally, we calculated maximum surface velocities of 3±1.9 m d−1 and 3.1±1.1 m d−1 for two of the glaciers during the latest identifiable surge events of 1985–1987 and 2003–2007. Within this glacier cluster, highly variable advance rates (0.01–1 km yr−1) and dissimilar surface velocities at the surge peak (3–35 m d−1) were observed. In comparison with other clusters worldwide, surge-type glaciers in the Central Andes are on average smaller and show minor absolute advances. Generally low velocities and the heterogeneous duration of the surge cycles are common between them and glaciers in the Karakorum, a region with similar climatic characteristics and many known surge-type glaciers. As a definitive assertion concerning the underlying surge mechanism of surges in the Central Andes could not be drawn based on the remote sensing data, this opens more detailed research avenues for surge-type glaciers in the region.

scholarly journals Climate controls on erosion in tectonically active landscapes

2020 ◽  
Vol 6 (42) ◽  
pp. eaaz3166 ◽  
Author(s):  
B. A. Adams ◽  
K. X. Whipple ◽  
A. M. Forte ◽  
A. M. Heimsath ◽  
K. V. Hodges
Keyword(s):  
Tectonic Evolution ◽  
Predictive Power ◽  
Annual Rainfall ◽  
Potential Influence ◽  
Ongoing Debate ◽  
Mountain Ranges ◽  
Erosion Rates ◽  
Tectonically Active ◽  
Climate Controls ◽  
The Himalaya

The ongoing debate about the nature of coupling between climate and tectonics in mountain ranges derives, in part, from an imperfect understanding of how topography, climate, erosion, and rock uplift are interrelated. Here, we demonstrate that erosion rate is nonlinearly related to fluvial relief with a proportionality set by mean annual rainfall. These relationships can be quantified for tectonically active landscapes, and calculations based on them enable estimation of erosion where observations are lacking. Tests of the predictive power of this relationship in the Himalaya, where erosion is well constrained, affirm the value of our approach. Our model allows estimation of erosion rates in fluvial landscapes using readily available datasets, and the underlying relationship between erosion and rainfall offers the promise of a deeper understanding of how climate and tectonic evolution affect erosion and topography in space and time and of the potential influence of climate on tectonics.

New paleontological evidence for complex middle Paleozoic tectonic evolution in the Appalachian western Blue Ridge

2020 ◽  
Vol 132 (9-10) ◽  
pp. 2105-2118
Author(s):  
Mary E. Lupo ◽  
James F. Tull ◽  
John Repetski ◽  
Paul A. Mueller
Keyword(s):  
North Carolina ◽  
Tectonic Evolution ◽  
Blue Ridge ◽  
Relative Paucity ◽  
Southern Appalachian ◽  
Stratigraphic Framework ◽  
Taconic Orogeny ◽  
Middle Paleozoic ◽  
Thrust Sheets ◽  
Group B

Abstract Reconstructing the tectonic evolution of the southern Appalachian metamorphic internides is hampered by the relative paucity of accurate geochronologic constraints and the apparent rarity or absence of Paleozoic cover sequences. At the orogen’s greatest width, near the junction of Georgia, North Carolina, and Tennessee, the western Blue Ridge is a composite metamorphic allochthon of three major thrust sheets: (A) a basal sheet above the Great Smoky fault overlying rocks of the foreland thrust belt composed of the Lower Cambrian Chilhowee Group and underlying Sandsuck Formation of the Neoproterozoic Walden Creek Group; (B) an intermediate sheet above the Maggies Mill–Citico fault composed of the middle Paleozoic Maggies Mill Formation; and (C) the main mass of the western Blue Ridge above the Alaculsy Valley–Miller Cove fault composed of the Neoproterozoic Ocoee Supergroup, and younger overlying sequences in the Epperson and Murphy synclinoria. The age of peak deformation and metamorphism in all of these sequences has historically been assigned to the Ordovician Taconic orogeny, but recent paleontologic discoveries suggest these events are significantly younger. In addition to the middle Paleozoic fauna recently reported from the Maggies Mill Formation in the intermediate thrust sheet, Silurian-Devonian conodonts have been found in units formerly correlated with the Walden Creek Group in the Epperson synclinorium. These discoveries suggest that widespread middle Paleozoic successor basin sequences unconformably overlie the Neoproterozoic-Cambrian drift-facies of the Chilhowee Group (and equivalents) and underlying rift-facies of the Ocoee Supergroup, and require modifications to existing models for the timing of the region’s stratigraphic framework and tectono-metamorphic evolution.

scholarly journals Distribution and natural history notes on Tachymenis chilensis chilensis (Schlegel, 1837) (Reptilia: Serpentes: Dipsadidae) in Argentina

Check List ◽  
2012 ◽  
Vol 8 (5) ◽  
pp. 919 ◽  
Author(s):  
Alejandro R. Giraudo ◽  
Félix Vidoz ◽  
Vanesa Arzamendia ◽  
Santiago J. Nenda
Keyword(s):  
Natural History ◽  
Barrier Effect ◽  
History Data ◽  
Mountain Ranges ◽  
Distribution Limit ◽  
The Andes ◽  
Northern Distribution ◽  
First Time ◽  
Latitudinal Range ◽  
Prey Items

We revisit the distribution and natural history data of Tachymenis chilensis chilensis (Schlegel, 1837) in Argentina based on compiled and novel records, extending its northern and southern distribution from the previously known localities in Argentina. We recorded two prey items in Argentinean populations: Rhinella rubropunctata, reported for the first time, and Liolaemus pictus. Tachymenis c. chilensis is mainly found in forested habitats, generally near wetlands with abundant populations of amphibians. The latitudinal range occupied by T. c. chilensis in Argentina is similar to that in Chile, but its northern distribution limit reaches the lowest latitudes in Chile. This is probably due to the higher humidity levels in the western slopes of the Andes and the barrier effect of the highest mountain ranges in this area.

scholarly journals Thick-Skinned and Thin-Skinned Tectonics: A Global Perspective

2017 ◽  
Author(s):  
O. Adrian Pfiffner
Keyword(s):  
Continental Crust ◽  
Large Scale ◽  
Crystalline Basement ◽  
Global Perspective ◽  
Normal Faults ◽  
Basin Inversion ◽  
Mountain Ranges ◽  
Passive Margins ◽  
Detachment Layer ◽  
Thrust Sheets

This paper gives an overview of the large-scale tectonic styles encountered in orogens worldwide. Thin-skinned and thick-skinned tectonics represent two end member styles recognized in mountain ranges. Both styles are encountered in former passive margins of continental plates. Thick-skinned style including the entire crust and possibly the lithospheric mantle are associated with intracontinental contraction. Delamination of subducting continental crust and horizontal protrusion of upper plate crust into the opening gap occurs in the terminal stage of continent-continent collision. Continental crust thinned prior to contraction is likely to develop relatively thin thrust sheets of crystalline basement. A true thin-skinned type requires a detachment layer of sufficient thickness. Thickness of the décollement layer as well as the mechanical contrast between décollement layer and detached cover control the style of folding and thrusting within the detached cover units. In subduction-related orogens, thin- and thick-skinned deformation may occur several hundreds of kilometers from the plate contact zone.  Basin inversion resulting from horizontal contraction may lead to the formation of basement uplifts by the combined reactivation of pre-existing normal faults and initiation of new reverse faults. In most orogens thick-skinned and thin-skinned structures both occur and evolve with a pattern where nappe stacking propagates outward and downward

Using repeat oblique aerial photography and satellite imagery to detect glacial change in the Cordillera Vilcanota, Peru, since 1931

2021 ◽  
Author(s):  
Ulrich Kamp ◽  
Karina Yager ◽  
Elise Arnett ◽  
Krysten Bowen ◽  
Kate Truitt ◽  
...  
Keyword(s):  
Satellite Imagery ◽  
Forest Cover ◽  
Primary Source ◽  
Ground Truth ◽  
Aerial Photographs ◽  
Aerial Image ◽  
Survey Method ◽  
Mountain Ranges ◽  
The Andes ◽  
Glacier Recession

<p>Terrestrial and aerial image analysis has proven to be a valuable survey method for documenting terrestrial landscape change related to, for example, biodiversity, urbanization, and environmental services such as land vegetation or forest cover and use, glacier extent, and water resources. Historical oblique aerial photographs offer exceptional opportunities to extend the observational record beyond the period covered by traditional nadir aerial surveys and satellite imagery. Here we apply these methods in the Cordillera Vilcanota of Southern Peru, home to the largest high alpine lake, Sibinacocha, in the Andes, a primary source of the Amazon River. The Shippee-Johnson aerial expedition of 1931 produced oblique photographs of glaciated peaks of the Cordillera Vilcanota. To determine the extent of glacial loss, we compared the 1931 glacier extents with more recent ones derived from satellite imagery analyses using Agisoft Metashape and Pixcavator. The identification of the flight camera positions from 1931 proved to be challenging, since the original photographs come with only rudimentary information. For three test glaciers, the Metashape analysis showed a glacier recession of between 50% and 95% from 1931 to 2018. Preliminary Pixcavator analysis results demonstrated a area decrease of 62% at two glacier termini between 1931 and 2020. Future studies will include repeating the oblique aerial photographs across the Vilcanota and other Andean mountain ranges, and also include ground truth and UAS imagery analysis.</p>

Sign in / Sign up

Export Citation Format

Share Document