Rios Cardoza, Carlos Francisco

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Rios Cardoza, Carlos Francisco

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Instituto de la Patagonia

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DOI 10.1016/j.geomorph.2020.107297
The formation of a giant collapse caprock sinkhole on the Barda Negra plateau basalts (Argentina): Magnetic, mineralogical and morphostructural evidences
2020-10-15
Diaz Michelena, Marina
;
Kilian, Rolf
;
Baeza, Oscar
;
Rios, Francisco
;
Angel Rivero, Miguel
;
Luis Mesa, Jose
;
Gonzalez, Veracruz
;
Arlensiu Ordonez, Amanda
;
Langlais, Benoit
;
Rocca, Maximiliano C. L.
The 1.5-km-wide, 40-m-deep, crater-like structure in the 10 Ma old Barda Negra basaltic plateau in Central Argentina was discovered in the early 2000s. Based on remote sensing surveys and on its morphological characteristics, similar to those of the Barringer crater in Arizona, the structure is described to be originated by an impact. In this study we ran several fieldwork campaigns and collected and analysed samples, in order to find more evidences to endorse or reject this hypothesis. We observe a circular depression not generally surrounded by raised rims, in contrast to craters produced either by a meteorite impact or phreatomagmatic eruption (maars). Mineralogical investigations of rocks and sediments do not show high pressure and temperature minerals, such as coesite or stishovite, or any remnants of an impactite or impact melt/glass. Likewise, no textural evidences for impact-related fracturing or stress are observed. A detailed geomorphological mapping indicates a successive crater development which invokes local stepwise subsidence. Magneticmapping performed with the EU-funded NEWTON multisensor novel instrument shows a similar to 2000 nT field anomaly associated to the edges of the crater, and susceptibility measurements cast an important contrast between the basaltic rims and plateau, and the crater interior. Therefore, we propose a sink-hole origin for the crater, with a former collapse of the plateau basalts and a latter infill with sedimentary material. This hypothesis is supported by the fact that the 40 to 85 m thick and 14 to 15 Ma old carbonate-bearing Collon Cura Formation, underneath the 100 to 150 m thick basaltic plateau lava sheet, represents ideal rocks for dissolution and karst formation; remote sensing data show other nearby sinkholes (20 km westward), with extensions of 3 x 6 km and 100 m depth, which are emplaced within a cogenetic neighboring basaltic plateau with a similar underlying lithology; and the consistence of the magnetic model computed with this scheme and on measured rock remanence and susceptibilities of the structure and surroundings. These giant collapse sinkholes, up to 6 km in diameter, within caprocks of very thick plateau basalts, represent unique examples for planetary surface shaping processes which also occur on Mars and comets in areas with basalts or rigid caprocks. (c) 2020 The Author(s). Published by Elsevier B.V.
Scopus© Citations 10 2
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DOI 10.1016/j.csr.2020.104101
Environmental and coastline changes controlling Holocene carbon accumulation rates in fjords of the western Strait of Magellan region
2020-08-01
Rios, Francisco
;
Kilian, Rolf
;
Lange, Carina B.
;
Baeza-Urrea, Oscar
;
Arz, Helge W.
;
Zindorf, Mark
;
De Pol Holz, Ricardo Hernán
;
Lamy, Frank
Organic-rich sediments of the southernmost Chilean Pacific coast and its fjord system constitute an important component of the global marine carbon budget. Sediment records from Trampa and Caribe bays and Churruca fjord in the western Magellan fjord system have been analyzed with the goal of understanding the factors controlling carbon accumulation and its regional fluctuation throughout the Holocene. The individual response in paleoproductivity at the different sites and related variations in accumulation rates document a very complex interplay among local and regional-scale environmental changes, and coastline elevation across the Holocene. Shallow sill basins close to the Pacific coast, as the ones studied here, are particularly sensitive to these processes, having responded with strong productivity changes throughout the Holocene. A Bayesian mixed model approach, using sediment archived provenance proxies, indicates that components of terrestrial plants and soils washed-out into these basins contribute with a variable proportion (20-80 wt%) of the total accumulated organic carbon. Accumulation rates of terrestrial carbon increase with the amount of precipitation in the hyper-humid mountain area, but also reflect distinct Holocene plant successions as well as long-term development of soil and vegetation cover that strongly overprint the direct precipitation impact. Over the Holocene accumulation rates of biogenic carbonate and aquatic-marine organic carbon range between 5 and 118 kg m(-2) kyr(-1) and 0.3-20 kg m(-2) kyr(-1), respectively. This variability depends on water column structure and conditions, which are regulated by the degree of marine transgression as a function of post glacial sea level rise and isostatic uplift as well as precipitation-related surface water freshening. In the Bahia Trampa record, a significant change in accumulation rates indicates a marine transgression at ca. 12.2 kyr BP, when the global sea level was 60-70 m lower than today and eustatic rise overcame isostatic rebound rates. In Caribe and Trampa records, CaCO3 accumulation rates were higher at ca. 7 kyr BP. The Churruca record shows organic carbon accumulation rates up to 36.2 kg m(-2) kyr(-1) during the early Holocene.
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DOI 10.1016/j.csr.2020.104101
Environmental and coastline changes controlling Holocene carbon accumulation rates in fjords of the western Strait of Magellan region
2020-08-01
Rios, Francisco
;
Kilian, Rolf
;
Lange, Carina B.
;
Baeza-Urrea, Oscar
;
Arz, Helge W.
;
Zindorf, Mark
;
De Pol Holz, Ricardo Hernán
;
Lamy, Frank
Organic-rich sediments of the southernmost Chilean Pacific coast and its fjord system constitute an important component of the global marine carbon budget. Sediment records from Trampa and Caribe bays and Churruca fjord in the western Magellan fjord system have been analyzed with the goal of understanding the factors controlling carbon accumulation and its regional fluctuation throughout the Holocene. The individual response in paleoproductivity at the different sites and related variations in accumulation rates document a very complex interplay among local and regional-scale environmental changes, and coastline elevation across the Holocene. Shallow sill basins close to the Pacific coast, as the ones studied here, are particularly sensitive to these processes, having responded with strong productivity changes throughout the Holocene. A Bayesian mixed model approach, using sediment archived provenance proxies, indicates that components of terrestrial plants and soils washed-out into these basins contribute with a variable proportion (20-80 wt%) of the total accumulated organic carbon. Accumulation rates of terrestrial carbon increase with the amount of precipitation in the hyper-humid mountain area, but also reflect distinct Holocene plant successions as well as long-term development of soil and vegetation cover that strongly overprint the direct precipitation impact. Over the Holocene accumulation rates of biogenic carbonate and aquatic-marine organic carbon range between 5 and 118 kg m(-2) kyr(-1) and 0.3-20 kg m(-2) kyr(-1), respectively. This variability depends on water column structure and conditions, which are regulated by the degree of marine transgression as a function of post glacial sea level rise and isostatic uplift as well as precipitation-related surface water freshening. In the Bahia Trampa record, a significant change in accumulation rates indicates a marine transgression at ca. 12.2 kyr BP, when the global sea level was 60-70 m lower than today and eustatic rise overcame isostatic rebound rates. In Caribe and Trampa records, CaCO3 accumulation rates were higher at ca. 7 kyr BP. The Churruca record shows organic carbon accumulation rates up to 36.2 kg m(-2) kyr(-1) during the early Holocene.
Scopus© Citations 8 1
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DOI 10.1016/j.quascirev.2019.07.014
Evolutionary history of herbivory in the Patagonian steppe: The role of climate, ancient megafauna, and guanaco
2019-09-15
Hernandez, Fidel
;
Rios Cardoza, Carlos Francisco
;
Perotto-Baldivieso, Humberto L.
Herbivory is an important ecological process than has influenced the evolution of grassland-savannah systems. The evolutionary history of herbivory largely determines how resilient plant communities are to herbivory, with communities evolving with a long history generally possessing plant adaptations that make them able to cope with such disturbance. Thus, the evolutionary history of herbivory can serve as an indicator of a system's resilience to modern grazing. Determining this history, however, is problematic because quantitative measures of herbivory and knowledge of plant origin are needed over appropriate evolutionary time frames. Paleoecology offers a useful framework for assessing this evolutionary history of plant-herbivore interactions. The Patagonian steppe is a phytogeographic province of South America whose evolutionary history of herbivory has been debated. Past discussions have focused completely on the abundance of its sole large ungulate herbivore-the guanaco (Lama guanicoe Muller 1776)-since European colonization of the continent. Here we use a paleoecological approach to reconstruct the evolutionary history of herbivory and plant evolution in the Patagonian steppe over a much broader, geologic time frame (Cenozoic) to shed light on the matter. We examine the role of past climate, ancient megafauna, and guanaco in shaping the vegetation and briefly discuss how present land use may be misaligned with the steppe's evolutionary history of herbivory. (C) 2019 Elsevier Ltd. All rights reserved.
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DOI 10.1016/j.quascirev.2019.07.014
Evolutionary history of herbivory in the Patagonian steppe: The role of climate, ancient megafauna, and guanaco
2019-09-15
Hernandez, Fidel
;
Rios Cardoza, Carlos Francisco
;
Perotto-Baldivieso, Humberto L.
Herbivory is an important ecological process than has influenced the evolution of grassland-savannah systems. The evolutionary history of herbivory largely determines how resilient plant communities are to herbivory, with communities evolving with a long history generally possessing plant adaptations that make them able to cope with such disturbance. Thus, the evolutionary history of herbivory can serve as an indicator of a system's resilience to modern grazing. Determining this history, however, is problematic because quantitative measures of herbivory and knowledge of plant origin are needed over appropriate evolutionary time frames. Paleoecology offers a useful framework for assessing this evolutionary history of plant-herbivore interactions. The Patagonian steppe is a phytogeographic province of South America whose evolutionary history of herbivory has been debated. Past discussions have focused completely on the abundance of its sole large ungulate herbivore-the guanaco (Lama guanicoe Muller 1776)-since European colonization of the continent. Here we use a paleoecological approach to reconstruct the evolutionary history of herbivory and plant evolution in the Patagonian steppe over a much broader, geologic time frame (Cenozoic) to shed light on the matter. We examine the role of past climate, ancient megafauna, and guanaco in shaping the vegetation and briefly discuss how present land use may be misaligned with the steppe's evolutionary history of herbivory. (C) 2019 Elsevier Ltd. All rights reserved.
Scopus© Citations 15 4

Rios Cardoza, Carlos Francisco

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