Germán Otharán, Carlos Zavala, Mariano Arcuri, Mariano Di Meglio, Agustín Zorzano, Denis Marchal, Guillermina Köhler
{"title":"与泥流有关的细粒沉积物的相分析。阿根廷Neuquina盆地中部Vaca Muerta地层(Tithoniano-Valanginiano)","authors":"Germán Otharán, Carlos Zavala, Mariano Arcuri, Mariano Di Meglio, Agustín Zorzano, Denis Marchal, Guillermina Köhler","doi":"10.5027/andgeov47n2-3061","DOIUrl":null,"url":null,"abstract":"The conventional sedimentological model suggests that the accumulation of organic-rich fine-grained sedimentary rocks (<62.5 μm) is uniquely associated with fallout processes in low energy depositional environments. This contribution analyzes organic-rich mudstones belonging to the lower section of the Vaca Muerta Formation at central areas of the Neuquen Basin (Arroyo Mulichinco, Tres Chorros and Rio Neuquen localities). The studied interval is characterized by the highest organic matter content of the Vaca Muerta Formation (up to 8% TOC). The associated mudstone deposits are usually highly compacted, thus obscuring the recognition of the original fabric and the analysis of mudstone depositional processes. Nevertheless, the common occurrence of carbonate concretions within these highly compacted intervals provides an exceptional preservation of mudstone primary fabric. After macroscopic study of polished slabs and thin sections of these cemented beds, a series of facies genetically linked to muddy underflows were recognized. The origin of these deposits is related to long-lived muddy hyperpycnal flows (quasi-steady mud flows) triggered by extreme river discharges during rainfall humid periods. During their travel basinward, hyperpycnal flows, originally composed of detrital mud, would be able to go through very low gradient reliefs, incorporating the available intrabasinal components (including organic matter) to their extrabasinal sedimentary load. The rapid basinward transfer of organic-rich mud would have provided a fast deposition and efficient burial of organic matter, avoiding its potential degradation at seafloor. Muddy underflows constitute a rational mechanism to explain the common occurrence of bituminous mudstones at central areas of the Neuquen Basin.","PeriodicalId":49108,"journal":{"name":"Andean Geology","volume":null,"pages":null},"PeriodicalIF":0.9000,"publicationDate":"2020-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"13","resultStr":"{\"title\":\"Análisis de facies en depósitos de grano fino asociados a flujos de fango. Formación Vaca Muerta (Tithoniano-Valanginiano), Cuenca Neuquina central, Argentina\",\"authors\":\"Germán Otharán, Carlos Zavala, Mariano Arcuri, Mariano Di Meglio, Agustín Zorzano, Denis Marchal, Guillermina Köhler\",\"doi\":\"10.5027/andgeov47n2-3061\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"The conventional sedimentological model suggests that the accumulation of organic-rich fine-grained sedimentary rocks (<62.5 μm) is uniquely associated with fallout processes in low energy depositional environments. This contribution analyzes organic-rich mudstones belonging to the lower section of the Vaca Muerta Formation at central areas of the Neuquen Basin (Arroyo Mulichinco, Tres Chorros and Rio Neuquen localities). The studied interval is characterized by the highest organic matter content of the Vaca Muerta Formation (up to 8% TOC). The associated mudstone deposits are usually highly compacted, thus obscuring the recognition of the original fabric and the analysis of mudstone depositional processes. Nevertheless, the common occurrence of carbonate concretions within these highly compacted intervals provides an exceptional preservation of mudstone primary fabric. After macroscopic study of polished slabs and thin sections of these cemented beds, a series of facies genetically linked to muddy underflows were recognized. The origin of these deposits is related to long-lived muddy hyperpycnal flows (quasi-steady mud flows) triggered by extreme river discharges during rainfall humid periods. During their travel basinward, hyperpycnal flows, originally composed of detrital mud, would be able to go through very low gradient reliefs, incorporating the available intrabasinal components (including organic matter) to their extrabasinal sedimentary load. The rapid basinward transfer of organic-rich mud would have provided a fast deposition and efficient burial of organic matter, avoiding its potential degradation at seafloor. 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Análisis de facies en depósitos de grano fino asociados a flujos de fango. Formación Vaca Muerta (Tithoniano-Valanginiano), Cuenca Neuquina central, Argentina
The conventional sedimentological model suggests that the accumulation of organic-rich fine-grained sedimentary rocks (<62.5 μm) is uniquely associated with fallout processes in low energy depositional environments. This contribution analyzes organic-rich mudstones belonging to the lower section of the Vaca Muerta Formation at central areas of the Neuquen Basin (Arroyo Mulichinco, Tres Chorros and Rio Neuquen localities). The studied interval is characterized by the highest organic matter content of the Vaca Muerta Formation (up to 8% TOC). The associated mudstone deposits are usually highly compacted, thus obscuring the recognition of the original fabric and the analysis of mudstone depositional processes. Nevertheless, the common occurrence of carbonate concretions within these highly compacted intervals provides an exceptional preservation of mudstone primary fabric. After macroscopic study of polished slabs and thin sections of these cemented beds, a series of facies genetically linked to muddy underflows were recognized. The origin of these deposits is related to long-lived muddy hyperpycnal flows (quasi-steady mud flows) triggered by extreme river discharges during rainfall humid periods. During their travel basinward, hyperpycnal flows, originally composed of detrital mud, would be able to go through very low gradient reliefs, incorporating the available intrabasinal components (including organic matter) to their extrabasinal sedimentary load. The rapid basinward transfer of organic-rich mud would have provided a fast deposition and efficient burial of organic matter, avoiding its potential degradation at seafloor. Muddy underflows constitute a rational mechanism to explain the common occurrence of bituminous mudstones at central areas of the Neuquen Basin.
期刊介绍:
This journal publishes original and review articles on geology and related sciences, in Spanish or English, in three issues a year (January, May and September). Articles or notes on major topics of broad interest in Earth Sciences dealing with the geology of South and Central America and Antarctica, and particularly of the Andes, are welcomed.
The journal is interested in publishing thematic sets of papers and accepts articles dealing with systematic Paleontology only if their main focus is the chronostratigraphical, paleoecological and/or paleogeographical importance of the taxa described therein.