Pub Date : 2022-03-07DOI: 10.5027/andgeov49n2-3444
J. Cabello
The discovery of lithium in the Salar de Atacama in northern Chile in 1969 laid the foundations for the development of the world's leading lithium brine deposit. The available background on the brine deposits located in the Atacama and Maricunga salt flats indicates reserves of 10,879,000 tons of lithium, to which resources are added for 3,335,100 tons of lithium identified in 9 additional Andean and pre-Andean salt flats. The future of exploration is also auspicious considering that there is information on the presence of lithium-bearing brines in another 13 salt flats and 36 identified prospective areas that have not yet been studied. The level of lithium reserves and resources identified and the encouraging expectations for exploration place Chile as a relevant player in the development of the lithium industry worldwide.
{"title":"Reservas, recursos y exploración de litio en salares del norte de Chile","authors":"J. Cabello","doi":"10.5027/andgeov49n2-3444","DOIUrl":"https://doi.org/10.5027/andgeov49n2-3444","url":null,"abstract":"The discovery of lithium in the Salar de Atacama in northern Chile in 1969 laid the foundations for the development of the world's leading lithium brine deposit. The available background on the brine deposits located in the Atacama and Maricunga salt flats indicates reserves of 10,879,000 tons of lithium, to which resources are added for 3,335,100 tons of lithium identified in 9 additional Andean and pre-Andean salt flats. The future of exploration is also auspicious considering that there is information on the presence of lithium-bearing brines in another 13 salt flats and 36 identified prospective areas that have not yet been studied. The level of lithium reserves and resources identified and the encouraging expectations for exploration place Chile as a relevant player in the development of the lithium industry worldwide.","PeriodicalId":49108,"journal":{"name":"Andean Geology","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2022-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42447657","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-03-07DOI: 10.5027/andgeov49n2-3417
Maria C. Zamaloa, Elina Cornou, M. Martínez, M. Quattrocchio, D. Olivera, C. Zavala, Marcos Asensio
A Miocene macroflora recovered from Ñirihuau Formation sediments exposed at Quebrada Vera site in northwesterern Patagonia, Argentina, is recorded and described for the first time. The assemblage is composed exclusively of free-sporing plants, mainly by Equisetum remains with subordinate occurrences of four fern morphotypes (represented by bi-, tri- and pinnate fronds). Equisetum imprints and molds include distinctive jointed stems with whorls of linear and basally fused leaves, numerous scars of lateral branches arranged in a radially symmetrical pattern situated at the nodes, and nodal diaphragms of up to 4 cm in diameter. The large size and regular branching of the stems link the fossils to the South American giant members of the genus and they probably represent a new fossil species. This is the first conclusive fossil record of a giant Equisetum worldwide, and consequently, it is biogeographically and evolutionarily relevant. The new findings attest that members of the giant horsetail clade were components of the Patagonian vegetation in the Miocene, implying that the age of the clade must predate that estimated from morphological and/or molecular data. The plant fossil assemblage represents part of a wetland community probably growing close to a riverside or lakeshore in coincidence with previous sedimentological estimates.
{"title":"The first fossil record of a giant horsetail (Equisetum, Equisetaceae) is from the Miocene of Patagonia, Argentina","authors":"Maria C. Zamaloa, Elina Cornou, M. Martínez, M. Quattrocchio, D. Olivera, C. Zavala, Marcos Asensio","doi":"10.5027/andgeov49n2-3417","DOIUrl":"https://doi.org/10.5027/andgeov49n2-3417","url":null,"abstract":"A Miocene macroflora recovered from Ñirihuau Formation sediments exposed at Quebrada Vera site in northwesterern Patagonia, Argentina, is recorded and described for the first time. The assemblage is composed exclusively of free-sporing plants, mainly by Equisetum remains with subordinate occurrences of four fern morphotypes (represented by bi-, tri- and pinnate fronds). Equisetum imprints and molds include distinctive jointed stems with whorls of linear and basally fused leaves, numerous scars of lateral branches arranged in a radially symmetrical pattern situated at the nodes, and nodal diaphragms of up to 4 cm in diameter. The large size and regular branching of the stems link the fossils to the South American giant members of the genus and they probably represent a new fossil species. This is the first conclusive fossil record of a giant Equisetum worldwide, and consequently, it is biogeographically and evolutionarily relevant. The new findings attest that members of the giant horsetail clade were components of the Patagonian vegetation in the Miocene, implying that the age of the clade must predate that estimated from morphological and/or molecular data. The plant fossil assemblage represents part of a wetland community probably growing close to a riverside or lakeshore in coincidence with previous sedimentological estimates.","PeriodicalId":49108,"journal":{"name":"Andean Geology","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2022-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48450827","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-03-07DOI: 10.5027/andgeov49n2-3418
S. Master
South African geologist Alexander du Toit spent three months in 1923 doing reconnaissance mapping in South America, which resulted in his seminal 1927 work “A Geological Comparison of South America and South Africa”. A few photographs taken by du Toit were published, but most were destroyed in a devasting fire in April 2021. Some surviving annotated images, giving locations, of a trip du Toit had made from Argentina to Chile on the Transandine Railway, in 1923, are reproduced here. They may help with recognizing landscape changes, such as due to melting glaciers, during the century since the photographs were taken.
1923年，南非地质学家Alexander du Toit花了三个月的时间在南美洲进行勘察测绘，这促成了他1927年的开创性著作《南美洲和南非的地质比较》。杜托伊特拍摄的一些照片被公布，但大多数照片在2021年4月的一场毁灭性大火中被毁。1923年，杜托伊特乘坐Transandine铁路从阿根廷到智利的一次旅行，一些幸存的带注释的图像，给出了地点，在这里被复制。它们可能有助于识别自照片拍摄以来的一个世纪内的景观变化，例如冰川融化。
{"title":"Historical photographs by South African geologist Alexander L. du Toit taken along the Transandine Railway (Argentina-Chile) in 1923","authors":"S. Master","doi":"10.5027/andgeov49n2-3418","DOIUrl":"https://doi.org/10.5027/andgeov49n2-3418","url":null,"abstract":"South African geologist Alexander du Toit spent three months in 1923 doing reconnaissance mapping in South America, which resulted in his seminal 1927 work “A Geological Comparison of South America and South Africa”. A few photographs taken by du Toit were published, but most were destroyed in a devasting fire in April 2021. Some surviving annotated images, giving locations, of a trip du Toit had made from Argentina to Chile on the Transandine Railway, in 1923, are reproduced here. They may help with recognizing landscape changes, such as due to melting glaciers, during the century since the photographs were taken.","PeriodicalId":49108,"journal":{"name":"Andean Geology","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2022-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46695815","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-03-07DOI: 10.5027/andgeov49n2-3397
Rebecca M. E. Williams, B. Hynek
Punctuated lake level drops at Lake General Carrera, Chile, over the last ~13 ka are recorded in multiple stacked deltas that differ in scale. Fifteen delta terrace suites are studied to examine the factors that influence deposit morphology. Surprisingly, the pronounced longitudinal precipitation gradient is inversely correlated with the observed variations in delta size. We find the drainage basins with long-term water storage in glaciers are associated with larger deltas. In these cases, the added contribution of rare, high-magnitude ice meltwater release events (> 600 m3/s) is suggested as the differential driver to enhance delta growth. The overall progradation rate is modest (0.2 - 1 m/yr), and appears to have slowed over time. For the youngest deltas, we estimate the range in the intermittency factor, a dimensionless measure of the frequency of floods, is 1 x 10-2 to 4 x10-5. Our results illustrate the natural variability of delta growth in a small region (
智利卡雷拉将军湖在过去约13卡的时间里，记录到多个规模不同的堆叠三角洲出现了点状湖面下降。研究了15个三角洲阶地套房，以考察影响矿床形态的因素。令人惊讶的是，明显的纵向降水梯度与观测到的三角洲大小变化呈负相关。我们发现，冰川中长期蓄水的流域与更大的三角洲有关。在这些情况下，罕见的高强度冰融水释放事件（>600 m3/s）的额外贡献被认为是促进三角洲增长的差异驱动因素。总体进积速率适中（0.2-1米/年），并且随着时间的推移似乎有所减缓。对于最年轻的三角洲，我们估计间歇性因子（洪水频率的无量纲度量）的范围为1 x 10-2至4 x10-5。我们的结果说明了小区域三角洲增长的自然变异性(
{"title":"Delta size variability at Lake General Carrera, Patagonia","authors":"Rebecca M. E. Williams, B. Hynek","doi":"10.5027/andgeov49n2-3397","DOIUrl":"https://doi.org/10.5027/andgeov49n2-3397","url":null,"abstract":"Punctuated lake level drops at Lake General Carrera, Chile, over the last ~13 ka are recorded in multiple stacked deltas that differ in scale. Fifteen delta terrace suites are studied to examine the factors that influence deposit morphology. Surprisingly, the pronounced longitudinal precipitation gradient is inversely correlated with the observed variations in delta size. We find the drainage basins with long-term water storage in glaciers are associated with larger deltas. In these cases, the added contribution of rare, high-magnitude ice meltwater release events (> 600 m3/s) is suggested as the differential driver to enhance delta growth. The overall progradation rate is modest (0.2 - 1 m/yr), and appears to have slowed over time. For the youngest deltas, we estimate the range in the intermittency factor, a dimensionless measure of the frequency of floods, is 1 x 10-2 to 4 x10-5. Our results illustrate the natural variability of delta growth in a small region (","PeriodicalId":49108,"journal":{"name":"Andean Geology","volume":"110 ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2022-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41281770","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-03-07DOI: 10.5027/andgeov49n2-3419
A. Kramarz, E. Bellosi, M. Bond, A. Forasiepi, J. Fernicola, Guillermo Aguirrezabala, Daniella Teixeira de Rezende
The Paleogene terrestrial faunal succession and its associated bearing volcaniclastic deposits has been exhaustively studied in central Patagonia, but there is still no acceptable litho-bio-chronostratigraphic ordering for the extra-Andean North Patagonia. The only references on Paleogene mammals bearing deposits north to Chubut River are imprecise and contradictory. West to Ingeniero Jacobacci (Río Negro Province, Argentina), the paleontologist and archaeologist Rodolfo Casamiquela reported a fossiliferous succession with Casamayoran or Mustersan (Eocene) and Deseadan (Oligocene) mammals from rocks currently mapped as the Las Chacras Formation. This unit includes acid to intermediate tuffs, ignimbrites, paleosols, conglomerates, and basalts originated in a perivolcanic fluvial system, under a seasonal subhumid-humid climate according to predominant pedogenic features. As a result of our fieldworks and fossil collection in the area of Ingeniero Jacobacci, and the revision of the materials collected by Casamiquela in the forties and fifties (with well-known stratigraphic origin), we identified a single mammal association from the lower section of the Las Chacras Formation (here named the Lower Las Chacras fauna) composed by: Plesiofelis schlosseri Roth, 1903 (Sparassodonta), Trigonostylops Ameghino, 1897, Astraponotus Ameghino, 1901 (Astrapotheria), Propyrotherium Ameghino, 1901 (Pyrotheria), Pseudhyrax eutrachytheroides Ameghino, 1901, Eohegetotherium priscum Ameghino, 1901, Puelia sigma (Ameghino, 1901), Periphragnis Roth, 1899 (Notoungulata), Isutaetus depictus Ameghino, 1902 (Cingulata), and a new member of Adianthidae (Litopterna) and probably of Pichipilidae (Paucituberculata). This assemblage is closer to that derived from the Rosado Member of the Sarmiento Formation at Gran Barranca, central Patagonia (type locality of the Mustersan Land Mammal Age) dated in ca. 38 Ma (late middle Eocene). A pyroclastic flow associated to the bearing deposits of Ingeniero Jacobacci was dated (K-Ar) in 39.2±2 Ma, value compatible with the Mustersan age here inferred for the Lower Las Chacras fauna. The alleged occurrence of Deseadan mammals in these levels was based on remains of an isotemnid notoungulate incorrectly identified as a leontinid. The presence of the Tinguirirican (early Oligocene) notoungulate Eohegetotherium priscum, with more apomorphic dental traits than in its Eocene allies, and of an astrapotheriid more derived than Astraponotus suggests that some advanced faunal elements would have been established in North Patagonia earlier than in central Patagonia.
{"title":"Eocene mammals from volcaniclastic deposits of the Somun Cura Plateau: biostratigraphic implications for north Patagonia Paleogene","authors":"A. Kramarz, E. Bellosi, M. Bond, A. Forasiepi, J. Fernicola, Guillermo Aguirrezabala, Daniella Teixeira de Rezende","doi":"10.5027/andgeov49n2-3419","DOIUrl":"https://doi.org/10.5027/andgeov49n2-3419","url":null,"abstract":"The Paleogene terrestrial faunal succession and its associated bearing volcaniclastic deposits has been exhaustively studied in central Patagonia, but there is still no acceptable litho-bio-chronostratigraphic ordering for the extra-Andean North Patagonia. The only references on Paleogene mammals bearing deposits north to Chubut River are imprecise and contradictory. West to Ingeniero Jacobacci (Río Negro Province, Argentina), the paleontologist and archaeologist Rodolfo Casamiquela reported a fossiliferous succession with Casamayoran or Mustersan (Eocene) and Deseadan (Oligocene) mammals from rocks currently mapped as the Las Chacras Formation. This unit includes acid to intermediate tuffs, ignimbrites, paleosols, conglomerates, and basalts originated in a perivolcanic fluvial system, under a seasonal subhumid-humid climate according to predominant pedogenic features. As a result of our fieldworks and fossil collection in the area of Ingeniero Jacobacci, and the revision of the materials collected by Casamiquela in the forties and fifties (with well-known stratigraphic origin), we identified a single mammal association from the lower section of the Las Chacras Formation (here named the Lower Las Chacras fauna) composed by: Plesiofelis schlosseri Roth, 1903 (Sparassodonta), Trigonostylops Ameghino, 1897, Astraponotus Ameghino, 1901 (Astrapotheria), Propyrotherium Ameghino, 1901 (Pyrotheria), Pseudhyrax eutrachytheroides Ameghino, 1901, Eohegetotherium priscum Ameghino, 1901, Puelia sigma (Ameghino, 1901), Periphragnis Roth, 1899 (Notoungulata), Isutaetus depictus Ameghino, 1902 (Cingulata), and a new member of Adianthidae (Litopterna) and probably of Pichipilidae (Paucituberculata). This assemblage is closer to that derived from the Rosado Member of the Sarmiento Formation at Gran Barranca, central Patagonia (type locality of the Mustersan Land Mammal Age) dated in ca. 38 Ma (late middle Eocene). A pyroclastic flow associated to the bearing deposits of Ingeniero Jacobacci was dated (K-Ar) in 39.2±2 Ma, value compatible with the Mustersan age here inferred for the Lower Las Chacras fauna. The alleged occurrence of Deseadan mammals in these levels was based on remains of an isotemnid notoungulate incorrectly identified as a leontinid. The presence of the Tinguirirican (early Oligocene) notoungulate Eohegetotherium priscum, with more apomorphic dental traits than in its Eocene allies, and of an astrapotheriid more derived than Astraponotus suggests that some advanced faunal elements would have been established in North Patagonia earlier than in central Patagonia.","PeriodicalId":49108,"journal":{"name":"Andean Geology","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2022-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42982412","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-11-22DOI: 10.5027/andgeov49n1-3309
Liliana Londoño Ortiz, C. Villagrán, Ismael E. Rincon, L. Hinojosa, Giselle Andrea Astorga
This study examines the new fossiliferous site Huapilacuy II of Mid-Holocene age (7,344±51-6,865±58 cal years BP.) located in the northwestern coast of the Isla Grande de Chiloé. This area was not affected by the successive Pleistocene glaciations, and therefore it presents a biogeographic relevance as a potential area of refugia and stability for the vegetation. The presence of plant macrofossils contained in a sedimentary sequence of ca. 300 cm thick, confers a special interest to the site, due to the scarce information available on this type of indicator in paleoenvironmental studies of southern Chile. Additionally, several pollen-based reconstructions from the southern Lake District of Chile (40-44˚ S), document the Holocene sequence of recolonization by the different temperate rainforests types that today occupy this region, although there are non-Holocene records for the Pacific coast of the region. The aim of this study is to reconstruct the local environmental conditions and paleoecology based on the stratigraphic context and the analysis of plant macrofossils at the site Huapilacuy II. In addition, based on the pollen analysis of the deposit, we provide new information to reconstruct the regional characteristics of the vegetation during the Middle-Holocene. In particular, the plant macrofossil record of marsh species contained in the sediments of the lower section of the studied sedimentary sequence, together with the pollen analysis of the same sequence, document a first phase of plant colonization at 7,344±51 cal yrs. BP, with predominance of Poaceae, ferns, and trees with regeneration capacity in open areas, such as Embothrium coccineum and Drimys winteri. The analysis of leaf macrofossils and palynomorphs recovered from several intercalated layers, from the middle section of the sedimentary sequence, show the local and regional development of dense and very humid forests dominated by Aextoxicon punctatum, associated with several species of Myrtaceae. The presence of soil moisture indicator species, such as Luma chequen, Myrceugenia sp. and Myrtaceae Blepharocalyx-type is consistent with the sedimentary environment and the local development of swamp or riverine forests. This hygrophile forest environment is also consistent with the assemblage of fossil mosses, dominated by species that grow today in dense closed-canopy forests, such as Weymouthia, Ptychomnium, Rigodium, Porothamnium and Eucamptodon. The regional correlation of the pollen spectra from Huapilacuy II and other records from the Lake District allows us to establish latitudinal and longitudinal differences of tree composition in the temperate-rainforests that expanded during the Early to Mid-Holocene. In particular, this study established for the northwestern coast of the Isla Grande de Chiloé the presence of the coastal association of the valdivian forest (As. Lapagerio-Aextoxiconetum), currently distributed along the Chilean coastline between 30˚- 43˚S. In contrast, the
{"title":"Historia de la vegetación del sitio Huapilacuy II durante el Holoceno Medio a partir del análisis polínico y de macrofósiles vegetales, Isla Grande de Chiloé, Chile","authors":"Liliana Londoño Ortiz, C. Villagrán, Ismael E. Rincon, L. Hinojosa, Giselle Andrea Astorga","doi":"10.5027/andgeov49n1-3309","DOIUrl":"https://doi.org/10.5027/andgeov49n1-3309","url":null,"abstract":"This study examines the new fossiliferous site Huapilacuy II of Mid-Holocene age (7,344±51-6,865±58 cal years BP.) located in the northwestern coast of the Isla Grande de Chiloé. This area was not affected by the successive Pleistocene glaciations, and therefore it presents a biogeographic relevance as a potential area of refugia and stability for the vegetation. The presence of plant macrofossils contained in a sedimentary sequence of ca. 300 cm thick, confers a special interest to the site, due to the scarce information available on this type of indicator in paleoenvironmental studies of southern Chile. Additionally, several pollen-based reconstructions from the southern Lake District of Chile (40-44˚ S), document the Holocene sequence of recolonization by the different temperate rainforests types that today occupy this region, although there are non-Holocene records for the Pacific coast of the region. The aim of this study is to reconstruct the local environmental conditions and paleoecology based on the stratigraphic context and the analysis of plant macrofossils at the site Huapilacuy II. In addition, based on the pollen analysis of the deposit, we provide new information to reconstruct the regional characteristics of the vegetation during the Middle-Holocene. In particular, the plant macrofossil record of marsh species contained in the sediments of the lower section of the studied sedimentary sequence, together with the pollen analysis of the same sequence, document a first phase of plant colonization at 7,344±51 cal yrs. BP, with predominance of Poaceae, ferns, and trees with regeneration capacity in open areas, such as Embothrium coccineum and Drimys winteri. The analysis of leaf macrofossils and palynomorphs recovered from several intercalated layers, from the middle section of the sedimentary sequence, show the local and regional development of dense and very humid forests dominated by Aextoxicon punctatum, associated with several species of Myrtaceae. The presence of soil moisture indicator species, such as Luma chequen, Myrceugenia sp. and Myrtaceae Blepharocalyx-type is consistent with the sedimentary environment and the local development of swamp or riverine forests. This hygrophile forest environment is also consistent with the assemblage of fossil mosses, dominated by species that grow today in dense closed-canopy forests, such as Weymouthia, Ptychomnium, Rigodium, Porothamnium and Eucamptodon. \u0000The regional correlation of the pollen spectra from Huapilacuy II and other records from the Lake District allows us to establish latitudinal and longitudinal differences of tree composition in the temperate-rainforests that expanded during the Early to Mid-Holocene. In particular, this study established for the northwestern coast of the Isla Grande de Chiloé the presence of the coastal association of the valdivian forest (As. Lapagerio-Aextoxiconetum), currently distributed along the Chilean coastline between 30˚- 43˚S. In contrast, the ","PeriodicalId":49108,"journal":{"name":"Andean Geology","volume":"1 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2021-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41835542","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-11-22DOI: 10.5027/andgeov49n1-3370
Igor Aguirre, José Maringue, I. Santibáñez, Gonzalo A. Yáñez
The hydric resource coming from groundwater has a strategic nature at global scale, within a context of overpopulation and over exploitation of the resource and climate change. Chile doesn’t scape to it, where climate models predict a drought for most of the country, including partially, the agriculture region of the Central Valley between Santiago and Puerto Montt. The adaption process to global change demands the exploration new sources of provisions of this resource, being strategic the one coming from aquifers. To date, the knowledge of these resources is limited to depths below 200 m in each aquifer. However, in the Central Valley between Santiago and Chiloé, the geophysical evidences allow to infer the existence of a thick volcano-sedimentary basin growing in thickness southward well above 500m, with good potential for occurrence of large groundwater resources. The characterization of deep aquifers, 200-1,000 m of depth, demands to have an exploration tool economic, non-invasive, and reliable, able to be applied in semi-urban and rural environments, where the water resource need is higher. The geophysical methodologies meet these characteristics and have been applied in Chile and elsewhere as an exploration tool of ground water resources. However, its application have not been described in Andean environments, of large population and/or agro-industrial activity. In consequence, the present work raises a methodological strategy for the characterization of groundwater resources, in particular for the detection of deep resources. We propose the application of a combination of complementary geophysical techniques, including electrical, electromagnetic, and gravimetric methods (to determine the aquifer geometry) along with complementary techniques, like magnetometry, to reduce interpretation ambiguity and , constrained by hydrogeological information and petrophysics of rocks and sediments of the basin and basement. Complementary, we include an analysis of the potential effects of cultural noise and its effects on geophysical observations, given the focus of exploration in semi-urban and rural places. With the aim to validate the proposed methodology we use as a case study the aquifer of Ñuble river, in the Ñuble region, Chile. This aquifer properly represents an Andean forearc environment in rural and semi-urban condition, and potentially hosting a deep seated aquifer. The results allow the characterization of an aquifer with hydrogeological potential between 50 and 300-500 depth, overlying a sedimentary basin of more than 1,000 m thickness. The application of the proposed methodology for the exploration of groundwater resources will provide, in consequence, the recognition of a vital relevance resource for the sustainability of Chile during the following decades.
{"title":"El rol de la exploración geofísica en acuíferos profundos en ambientes semiurbanos y rurales en cuencas de ante arco Andino, caso de estudio en acuífero del río Ñuble, Valle Central de Chile","authors":"Igor Aguirre, José Maringue, I. Santibáñez, Gonzalo A. Yáñez","doi":"10.5027/andgeov49n1-3370","DOIUrl":"https://doi.org/10.5027/andgeov49n1-3370","url":null,"abstract":"The hydric resource coming from groundwater has a strategic nature at global scale, within a context of overpopulation and over exploitation of the resource and climate change. Chile doesn’t scape to it, where climate models predict a drought for most of the country, including partially, the agriculture region of the Central Valley between Santiago and Puerto Montt. The adaption process to global change demands the exploration new sources of provisions of this resource, being strategic the one coming from aquifers. To date, the knowledge of these resources is limited to depths below 200 m in each aquifer. However, in the Central Valley between Santiago and Chiloé, the geophysical evidences allow to infer the existence of a thick volcano-sedimentary basin growing in thickness southward well above 500m, with good potential for occurrence of large groundwater resources. \u0000The characterization of deep aquifers, 200-1,000 m of depth, demands to have an exploration tool economic, non-invasive, and reliable, able to be applied in semi-urban and rural environments, where the water resource need is higher. \u0000The geophysical methodologies meet these characteristics and have been applied in Chile and elsewhere as an exploration tool of ground water resources. However, its application have not been described in Andean environments, of large population and/or agro-industrial activity. In consequence, the present work raises a methodological strategy for the characterization of groundwater resources, in particular for the detection of deep resources. We propose the application of a combination of complementary geophysical techniques, including electrical, electromagnetic, and gravimetric methods (to determine the aquifer geometry) along with complementary techniques, like magnetometry, to reduce interpretation ambiguity and , constrained by hydrogeological information and petrophysics of rocks and sediments of the basin and basement. Complementary, we include an analysis of the potential effects of cultural noise and its effects on geophysical observations, given the focus of exploration in semi-urban and rural places. \u0000With the aim to validate the proposed methodology we use as a case study the aquifer of Ñuble river, in the Ñuble region, Chile. This aquifer properly represents an Andean forearc environment in rural and semi-urban condition, and potentially hosting a deep seated aquifer. The results allow the characterization of an aquifer with hydrogeological potential between 50 and 300-500 depth, overlying a sedimentary basin of more than 1,000 m thickness. The application of the proposed methodology for the exploration of groundwater resources will provide, in consequence, the recognition of a vital relevance resource for the sustainability of Chile during the following decades.","PeriodicalId":49108,"journal":{"name":"Andean Geology","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2021-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43996634","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-11-22DOI: 10.5027/andgeov49n1-3369
Andrés Lo Vecchio Repetto, M. Candela, Daniel Falaschi, Federico Otero, María Alejandrina Videla, M. G. Lenzano, Andrés Rivera
Current climatic conditions in Central Andes (CA) (31-36 °S) have triggered the reduction of glacier area. Although CA are geographically circumscribed to an area under the same macroclimatic domain, their rugged topography creates several topoclimates as response to the effects of elevation, slope and aspect (morphometric factors). This study explores the impact of morphometric factors on the evolution of the glacial surface located above of Maipo volcano (34°09'50''S; 69°49'53''W). Through the use of 11 LANDSAT images (MSS, TM and OLI), the spatio-temporal evolution (period 1976-2020) of the glacier area was reconstructed. On this period, glacier area was reduced by 6 ± 0.5 km2 (-0.14 ± 0.01 km2a-1), equal to 63 % of 1976 glacial area (9.6 ± 0.5 km2). Fifty percent of the reduction occurred between 3,900 and 4,000 m elevation, with absolute losses towards lower elevations. In addition, it was detected that for every 100 m of ascent the relative area loss rate decreased 0.1 %a-1 (R2 = 0.81; p-value
{"title":"Cambio de área glaciar en el volcán Maipo (Andes Centrales), una aproximación morfométrica: 4 décadas de registros satelitales","authors":"Andrés Lo Vecchio Repetto, M. Candela, Daniel Falaschi, Federico Otero, María Alejandrina Videla, M. G. Lenzano, Andrés Rivera","doi":"10.5027/andgeov49n1-3369","DOIUrl":"https://doi.org/10.5027/andgeov49n1-3369","url":null,"abstract":"Current climatic conditions in Central Andes (CA) (31-36 °S) have triggered the reduction of glacier area. Although CA are geographically circumscribed to an area under the same macroclimatic domain, their rugged topography creates several topoclimates as response to the effects of elevation, slope and aspect (morphometric factors). This study explores the impact of morphometric factors on the evolution of the glacial surface located above of Maipo volcano (34°09'50''S; 69°49'53''W). Through the use of 11 LANDSAT images (MSS, TM and OLI), the spatio-temporal evolution (period 1976-2020) of the glacier area was reconstructed. On this period, glacier area was reduced by 6 ± 0.5 km2 (-0.14 ± 0.01 km2a-1), equal to 63 % of 1976 glacial area (9.6 ± 0.5 km2). Fifty percent of the reduction occurred between 3,900 and 4,000 m elevation, with absolute losses towards lower elevations. In addition, it was detected that for every 100 m of ascent the relative area loss rate decreased 0.1 %a-1 (R2 = 0.81; p-value","PeriodicalId":49108,"journal":{"name":"Andean Geology","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2021-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48252200","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-11-22DOI: 10.5027/andgeov49n1-3316
A. Tauber, F. Alvarez, G. Martínez, José Augusto Haro, J. Krapovickas, G. Nieto
New fossil remains were found in Neogene and quaternary sedimentary sequences exposed in Alpa Corral and río San Bartolomé localities (Rio Cuarto Department, Córdoba, Argentina). They were assigned to Nopachtus cabrerai (Xenarthra, Cingulata, Glyptodontidae), Notiomastodon platensis (Proboscidea, Gomphotheriidae) and cf. Trigodon gaudryi (Notoungulata, Toxodontidae), and traces of the Scoyenia ichnofacies, as Taenidium barretti, were identified. Based on these findings, we conclude that: 1, the species Nopachtus cabrerai and cf. Trigodon gaudryi are registered for the first time in the Sierras Pampeanas region and support (along with the rest of the known taxa) a clear faunistic similarity to the Pampean region; 2, the beginning of the Neogene sedimentation in the Alpa Corral area (Las Barrancas river and San Bartolome river) would have started during the early Pliocene (Montehermosan Age); 3, the paleoenvironment would have been a fluvial system, with meandering canals interspersed with paleosols developed in floodplains with overflow deposits or abandoned meanders; 4, the paleontological and sedimentary record suggests a well-marked diachronism (from west-southwest to east-northeast) between the beginning of the Neogene sedimentation in the southern sector of San Alberto valley (late Miocene [Huayquerian Age]), the Alpa Corral region (early Pliocene [Monthermosan Age), and Río La Cruz valley (late Pliocene [Chapadmalalan Age]).
在Alpa Corral和río San Bartolomé地区（阿根廷科尔多瓦的Rio Cuarto省）暴露的新第三纪和第四纪沉积序列中发现了新的化石遗迹。它们被分为卡氏Nopachtus cabrerai（异齿目、Cingulata、Glyptodontidae）、Notiomastodon platensis（长鼻目、Gomphotheridae）和比较Trigodon gaudryi（Notoungulata、Toxodontidae），并鉴定出Scoyenia遗迹相的痕迹，如Taenidium barreti。基于这些发现，我们得出结论：1，Nopachtus cabrerai和C.Trigodon gaudryi物种首次在Sierras Pampeanas地区登记，并支持（与其他已知分类群一起）与Pampean地区在动物区系上的明显相似性；2、Alpa Corral地区（Las Barrancas河和San Bartolome河）的新第三纪沉积始于上新世早期（蒙特赫莫桑时代）；3、古环境应为河流系统，蜿蜒的运河中穿插着在泛滥平原上发育的古土壤，其中有溢流沉积物或废弃的曲流；4，古生物学和沉积记录表明，在圣阿尔贝托山谷南部的新第三纪沉积开始（中新世晚期[华克时代]）、Alpa Corral地区（上新世早期[蒙赫莫桑时代]）和Río La Cruz山谷（上新世晚期[查帕德马拉兰时代]）之间存在明显的年代交替（从西南偏西到东北偏东）。
{"title":"Nuevos sitios fosilíferos y evolución paleoambiental del cenozoico tardío del suroeste de Córdoba, Argentina","authors":"A. Tauber, F. Alvarez, G. Martínez, José Augusto Haro, J. Krapovickas, G. Nieto","doi":"10.5027/andgeov49n1-3316","DOIUrl":"https://doi.org/10.5027/andgeov49n1-3316","url":null,"abstract":"New fossil remains were found in Neogene and quaternary sedimentary sequences exposed in Alpa Corral and río San Bartolomé localities (Rio Cuarto Department, Córdoba, Argentina). They were assigned to Nopachtus cabrerai (Xenarthra, Cingulata, Glyptodontidae), Notiomastodon platensis (Proboscidea, Gomphotheriidae) and cf. Trigodon gaudryi (Notoungulata, Toxodontidae), and traces of the Scoyenia ichnofacies, as Taenidium barretti, were identified. Based on these findings, we conclude that: 1, the species Nopachtus cabrerai and cf. Trigodon gaudryi are registered for the first time in the Sierras Pampeanas region and support (along with the rest of the known taxa) a clear faunistic similarity to the Pampean region; 2, the beginning of the Neogene sedimentation in the Alpa Corral area (Las Barrancas river and San Bartolome river) would have started during the early Pliocene (Montehermosan Age); 3, the paleoenvironment would have been a fluvial system, with meandering canals interspersed with paleosols developed in floodplains with overflow deposits or abandoned meanders; 4, the paleontological and sedimentary record suggests a well-marked diachronism (from west-southwest to east-northeast) between the beginning of the Neogene sedimentation in the southern sector of San Alberto valley (late Miocene [Huayquerian Age]), the Alpa Corral region (early Pliocene [Monthermosan Age), and Río La Cruz valley (late Pliocene [Chapadmalalan Age]).","PeriodicalId":49108,"journal":{"name":"Andean Geology","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2021-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45617820","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-11-22DOI: 10.5027/andgeov49n1-3383
E. Rossello, S. Cossey, G. Fernández
The offshore Talara Basin is the western extension of the hydrocarbon producing onshore fields since the mid-1800s area of Peru and is also located above the subduction zone of the active continental margin of South America. The offshore portion was evaluated using high quality 3D seismic where mapping horizons are all unconformities within the Eocene as well as the unconformities at the top Paleocene and top Cretaceous. Possible source rocks are the Cretaceous black marine shales of the Campanian Redondo Formation, the limestones of the Albian Muerto Formation, and the marine shales of the Paleogene. The primary target offshore is expected to be deep-water turbidites of Paleocene/Eocene age with a depositional source from the northeast from highlands created by the compressional uplift of the Andes. The main seals offshore are expected to be shales of the upper Eocene Lagunitos Formation and shales in the Chacra Formation, which are also seals in the onshore Litoral field. Thermal maturation modeling shows that two hydrocarbon kitchens exist in the offshore portion of the Talara basin, one in the north and one in the south. The probable Cretaceous source rocks reached the onset of maturity (VR = 0.63%) at a depth of 3,250 to 3,285 m (10,663 – 10,778 ft) between 30 and 39 Ma (Late Eocene to Oligocene). Importantly, the Cretaceous source rocks stay within the oil window once they enter it in the late Eocene. Satellite studies show a large offshore present-day oil seep in the southern part of the basin and 3D seismic shows direct hydrocarbon indicators (DHIs) imaged as flat spots and bottom simulating reflectors (BSR). Basin modeling suggests hydrocarbon migration pathways would have been updip (to the east) into the onshore traps and would therefore have first filled the offshore traps along the migration pathway. We conclude that the Talara Basin offshore offers excellent exploration opportunities in a proven productive area where multiple prospects have been mapped.
{"title":"The hydrocarbon potential of the offshore Talara Basin, Peru","authors":"E. Rossello, S. Cossey, G. Fernández","doi":"10.5027/andgeov49n1-3383","DOIUrl":"https://doi.org/10.5027/andgeov49n1-3383","url":null,"abstract":"The offshore Talara Basin is the western extension of the hydrocarbon producing onshore fields since the mid-1800s area of Peru and is also located above the subduction zone of the active continental margin of South America. The offshore portion was evaluated using high quality 3D seismic where mapping horizons are all unconformities within the Eocene as well as the unconformities at the top Paleocene and top Cretaceous. Possible source rocks are the Cretaceous black marine shales of the Campanian Redondo Formation, the limestones of the Albian Muerto Formation, and the marine shales of the Paleogene. The primary target offshore is expected to be deep-water turbidites of Paleocene/Eocene age with a depositional source from the northeast from highlands created by the compressional uplift of the Andes. The main seals offshore are expected to be shales of the upper Eocene Lagunitos Formation and shales in the Chacra Formation, which are also seals in the onshore Litoral field. Thermal maturation modeling shows that two hydrocarbon kitchens exist in the offshore portion of the Talara basin, one in the north and one in the south. The probable Cretaceous source rocks reached the onset of maturity (VR = 0.63%) at a depth of 3,250 to 3,285 m (10,663 – 10,778 ft) between 30 and 39 Ma (Late Eocene to Oligocene). Importantly, the Cretaceous source rocks stay within the oil window once they enter it in the late Eocene. Satellite studies show a large offshore present-day oil seep in the southern part of the basin and 3D seismic shows direct hydrocarbon indicators (DHIs) imaged as flat spots and bottom simulating reflectors (BSR). Basin modeling suggests hydrocarbon migration pathways would have been updip (to the east) into the onshore traps and would therefore have first filled the offshore traps along the migration pathway. We conclude that the Talara Basin offshore offers excellent exploration opportunities in a proven productive area where multiple prospects have been mapped.","PeriodicalId":49108,"journal":{"name":"Andean Geology","volume":" ","pages":""},"PeriodicalIF":0.9,"publicationDate":"2021-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45709091","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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