Pub Date : 2023-04-15DOI: 10.18268/bsgm2023v75n1a181122
Alexander Sánchez-Duque, F. Bautista, Rubén Cejudo, M. Cervantes-Solano, Avto Goguitchaichvili
En el presente trabajo se reportan los resultados de un estudio de magnetismo ambiental realizado en el Área Metropolitana del Valle de Aburrá (Colombia) con el objetivo de determinar la variación espacial de la contaminación en la zona urbana. Se diseñó un muestreo bidimensional en el que se definieron 99 sitios de muestreo, cada uno de los sitios fue georreferenciado y descrito por factores categóricos de uso de suelo, jerarquía vial, superficie vial, grupo de suelo o unidad geológica, especie vegetal recolectada y ciudad o municipio. En total se recolectaron 307 muestras ambientales de las cuales, 110 fueron de suelo urbano superficial, 99 de polvo urbano y 98 hojas de plantas de ornato público. Se emplearon técnicas de magnetismo de rocas para determinar la naturaleza de los minerales magnéticos presentes en las muestras. Se realizó un análisis de varianza no paramétrico para relacionar los valores de los parámetros magnéticos con los factores categóricos y revelar las posibles fuentes de las partículas magnéticas. Posteriormente, mediante el factor de aumento magnético en las muestras de polvo y suelo superficial, se definieron los valores de referencia de la contaminación específicos para cada zona y cada tipo de muestra. A partir de los valores calculados y georreferenciados se diseñaron mapas que muestran modelos descriptivos de la contaminación ambiental para cada área urbana según el tipo de muestra ambiental y los parámetros magnéticos. Los resultados revelan que la señal magnética en los sitios con mayor concentración de minerales magnéticos es dominada por minerales ferrimagnéticos de origen antrópico. Los análisis no paramétricos de la varianza muestran que una mayor concentración relativa de estos minerales tiene una fuerte relación con la jerarquía vial y en menor grado con usos de suelo. Los mapas demuestran que la mayor parte de la superficie urbana estudiada presenta algún nivel de contaminación.
{"title":"Las partículas magnéticas como indicadoras de contaminación en el Valle de Aburrá (Colombia)","authors":"Alexander Sánchez-Duque, F. Bautista, Rubén Cejudo, M. Cervantes-Solano, Avto Goguitchaichvili","doi":"10.18268/bsgm2023v75n1a181122","DOIUrl":"https://doi.org/10.18268/bsgm2023v75n1a181122","url":null,"abstract":"En el presente trabajo se reportan los resultados de un estudio de magnetismo ambiental realizado en el Área Metropolitana del Valle de Aburrá (Colombia) con el objetivo de determinar la variación espacial de la contaminación en la zona urbana. Se diseñó un muestreo bidimensional en el que se definieron 99 sitios de muestreo, cada uno de los sitios fue georreferenciado y descrito por factores categóricos de uso de suelo, jerarquía vial, superficie vial, grupo de suelo o unidad geológica, especie vegetal recolectada y ciudad o municipio. En total se recolectaron 307 muestras ambientales de las cuales, 110 fueron de suelo urbano superficial, 99 de polvo urbano y 98 hojas de plantas de ornato público. Se emplearon técnicas de magnetismo de rocas para determinar la naturaleza de los minerales magnéticos presentes en las muestras. Se realizó un análisis de varianza no paramétrico para relacionar los valores de los parámetros magnéticos con los factores categóricos y revelar las posibles fuentes de las partículas magnéticas. Posteriormente, mediante el factor de aumento magnético en las muestras de polvo y suelo superficial, se definieron los valores de referencia de la contaminación específicos para cada zona y cada tipo de muestra. A partir de los valores calculados y georreferenciados se diseñaron mapas que muestran modelos descriptivos de la contaminación ambiental para cada área urbana según el tipo de muestra ambiental y los parámetros magnéticos. Los resultados revelan que la señal magnética en los sitios con mayor concentración de minerales magnéticos es dominada por minerales ferrimagnéticos de origen antrópico. Los análisis no paramétricos de la varianza muestran que una mayor concentración relativa de estos minerales tiene una fuerte relación con la jerarquía vial y en menor grado con usos de suelo. Los mapas demuestran que la mayor parte de la superficie urbana estudiada presenta algún nivel de contaminación.","PeriodicalId":48849,"journal":{"name":"Boletin De La Sociedad Geologica Mexicana","volume":"1 1","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41456558","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 : 2023-04-15DOI: 10.18268/bsgm2023v75n1a250822
M. Torres-Martínez, Francisco Sánchez-Beristain, J. Reitner
The San Cassiano Formation from the Dolomites, NE Italy, is a Ladinian–Carnian (Middle – Upper Triassic) lithostratigraphic unit belonging to the Western Tethys domain. In this formation numerous groups of marine invertebrates from reef communities have been reported. In particular, brachiopods are represented by different orders. Thecideids are the most abundant and diverse, with different species of the genus Thecospira. Despite the apparent abundance, only one report exists of a thecideid of the genus preserved in life position: Thecospira tyrolensis. In this study, we describe and discuss the first finding of Thecospira semseyi and Thecospira tenuistriata in life position based on the study of thin sections of Cipit boulders. Seemingly, the Th. semseyi shells were not firmly attached to the substrate by a small cementation surface; therefore, they could have lived embedded into the biogenic matrix. By contrast, Th. tenuistriata displays an umbonal region modified in a cementation area, allowing the attachment to the bio-builder. Most samples don’t show any signal of transport since all specimens are articulated and are still attached to the substrate. Besides, the commissures are partially opened, free of any encrustation of sponge or bryozoan growing. The preservation of brachiopods suggests that the samples of both species were fossilized in life position. Moreover, Th. semseyi and Th. tenuistriata continued to live although the host’s fabric was imbibing the brachiopods’ ventral valve. This shows that thecideids were important components of Tethys reef communities.
{"title":"First occurrence in life position of two Triassic brachiopod species (Thecideida) from NE Italy: Paleoecological considerations","authors":"M. Torres-Martínez, Francisco Sánchez-Beristain, J. Reitner","doi":"10.18268/bsgm2023v75n1a250822","DOIUrl":"https://doi.org/10.18268/bsgm2023v75n1a250822","url":null,"abstract":"The San Cassiano Formation from the Dolomites, NE Italy, is a Ladinian–Carnian (Middle – Upper Triassic) lithostratigraphic unit belonging to the Western Tethys domain. In this formation numerous groups of marine invertebrates from reef communities have been reported. In particular, brachiopods are represented by different orders. Thecideids are the most abundant and diverse, with different species of the genus Thecospira. Despite the apparent abundance, only one report exists of a thecideid of the genus preserved in life position: Thecospira tyrolensis. In this study, we describe and discuss the first finding of Thecospira semseyi and Thecospira tenuistriata in life position based on the study of thin sections of Cipit boulders. Seemingly, the Th. semseyi shells were not firmly attached to the substrate by a small cementation surface; therefore, they could have lived embedded into the biogenic matrix. By contrast, Th. tenuistriata displays an umbonal region modified in a cementation area, allowing the attachment to the bio-builder. Most samples don’t show any signal of transport since all specimens are articulated and are still attached to the substrate. Besides, the commissures are partially opened, free of any encrustation of sponge or bryozoan growing. The preservation of brachiopods suggests that the samples of both species were fossilized in life position. Moreover, Th. semseyi and Th. tenuistriata continued to live although the host’s fabric was imbibing the brachiopods’ ventral valve. This shows that thecideids were important components of Tethys reef communities.","PeriodicalId":48849,"journal":{"name":"Boletin De La Sociedad Geologica Mexicana","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46845425","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 : 2023-04-15DOI: 10.18268/bsgm2023v75n1a031122
Marco Rogelio Bustamante-Orozco, Ojilve Ramón Medrano-Pérez, Iris Neri-Flores, Edgar Ángeles-Cordero
El objetivo de esta investigación es interpretar las respuestas magnéticas y gravimétricas del subsuelo en la porción oeste en la cuenca Grijalva, México, para identificar y delimitar las áreas de unidades de rocas con potencial acuífero. Para ello, se realizó el procesamiento de datos aeromagnéticos y gravimétricos satelitales con el propósito de delimitar las características geológicas de mayor interés. Los resultados muestran que la parte centro-norte de la porción de estudio representa la zona con mayor potencial acuífero, y coincide con las áreas de mayor espesor sedimentario, de menor altitud y donde se concentran las concesiones de agua subterránea. Por tanto, el cambio de gradientes entre las respuestas magnéticas y gravimétricas favorecen el conocimiento del marco estructural (fallas, fracturas, bordes y contactos geológicos) y la inferencia de las áreas con potencial acuífero. En detalle, de las trasformaciones o filtros utilizados la Derivada Tilt (TDR, por sus siglas en inglés) presenta las tendencias lineales asociadas al marco estructural con particular interés hídrico. Se busca favorecer la toma de decisión y la investigación en los temas geohidrológicos, ordenamiento territorial y políticas públicas relacionadas.
{"title":"Interpretación de datos aeromagnéticos y gravimétricos satelitales para la identificación de zonas con potencial acuífero en la porción oeste de la cuenca Grijalva, México","authors":"Marco Rogelio Bustamante-Orozco, Ojilve Ramón Medrano-Pérez, Iris Neri-Flores, Edgar Ángeles-Cordero","doi":"10.18268/bsgm2023v75n1a031122","DOIUrl":"https://doi.org/10.18268/bsgm2023v75n1a031122","url":null,"abstract":"El objetivo de esta investigación es interpretar las respuestas magnéticas y gravimétricas del subsuelo en la porción oeste en la cuenca Grijalva, México, para identificar y delimitar las áreas de unidades de rocas con potencial acuífero. Para ello, se realizó el procesamiento de datos aeromagnéticos y gravimétricos satelitales con el propósito de delimitar las características geológicas de mayor interés. Los resultados muestran que la parte centro-norte de la porción de estudio representa la zona con mayor potencial acuífero, y coincide con las áreas de mayor espesor sedimentario, de menor altitud y donde se concentran las concesiones de agua subterránea. Por tanto, el cambio de gradientes entre las respuestas magnéticas y gravimétricas favorecen el conocimiento del marco estructural (fallas, fracturas, bordes y contactos geológicos) y la inferencia de las áreas con potencial acuífero. En detalle, de las trasformaciones o filtros utilizados la Derivada Tilt (TDR, por sus siglas en inglés) presenta las tendencias lineales asociadas al marco estructural con particular interés hídrico. Se busca favorecer la toma de decisión y la investigación en los temas geohidrológicos, ordenamiento territorial y políticas públicas relacionadas.","PeriodicalId":48849,"journal":{"name":"Boletin De La Sociedad Geologica Mexicana","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45586224","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 : 2023-04-15DOI: 10.18268/bsgm2023v75n1a161122
David Gómez-Vivo, Fernando Gervilla, A. Azor, Rebeca Hernández-Díaz, R. Piña, C. Alvarez
El yacimiento de Zn-Pb de Castellanos, situado al noroeste de la isla de Cuba, encaja en un paquete de pizarras negras intercalado en la parte superior de una potente secuencia siliciclástica (>4km), constituida principalmente por areniscas y limolitas de edad Jurásico Inferior y Medio (Formación San Cayetano). El yacimiento es estratiforme, se orienta en dirección NE-SO concordantemente con la estratificación de las pizarras encajantes y está constituido por dos bloques (el bloque Farallones al NE y el bloque Susana al SO) separados por una zona de falla con rumbo N120ºE; una zona de falla con la misma dirección limita también el bloque Farallones en su contacto NE. Este bloque se superpone a un complejo filoniano constituido por filones de pirita±calcopirita y cuarzo, de <10cm de espesor, y orientados también en dirección N120ºE. El cuerpo estratiforme principal está constituido por pirita, esfalerita y galena, con ganga de carbonatos (principalmente dolomita-ankerita y calcita), cuarzo, barita y, y menores proporciones de sericita, biotita parcialmente alterada a clorita y apatito criptocristalino. Muestra una estructura zonal con una zona basal discontinua rica en pirita y una zona superior heterogénea en la que varían tanto las proporciones modales de sulfuros+carbonatos (localmente con cuarzo), como la abundancia relativa de esfalerita+galena respecto a pirita. En conjunto, presenta una textura groseramente bandeada en la que alternan irregularmente bandas ricas en pirita, bandas con esfalerita y galena, y bandas de dolomita-ankerita (±sericita, biotita-clorita y apatito criptocristalino), mejor definida hacia el SO del cuerpo mineral. En este sentido, y hacia el techo de la mineralización., tiende a aumentar la proporción modal de cuarzo y localmente de barita. De NE a SO también se observa una variación en la composición química de la esfalerita, la cual se hace progresivamente más rica en Zn, a la vez que cristaliza una generación más tardía de esfalerita extremadamente pobre en Fe (<1% en peso). En los límites de bloques, la mineralización está afectada por varios episodios de fracturación y brechificación durante los cuales precipitaron y/o se movilizaron diversas generaciones de calcita, barita, cuarzo y galena. En los episodios más tardíos de esta etapa precipita también calcopirita rellenando fracturas y huecos intersticiales entre los fragmentos de sulfuros previos. La interpretación genética de la mineralización de Castellanos que se propone está basada en la precipitación repetitiva (multifásica) de los sulfuros+carbonatos como consecuencia de la interacción de fluidos/salmueras mineralizantes ascendentes a lo largo de las fracturas que dieron lugar al complejo filoniano con los sedimentos ricos en materia orgánica depositados en el fondo de una subcuenca anóxica desarrollada en la cuenca de margen pasivo donde se depositó la Formación San Cayetano. Las salmueras fueron oxidantes, saturadas en sulfato, y se habrían generado en la
{"title":"El yacimiento de Zn-Pb de Castellanos (Cuba): un depósito sedimentario-exhalativo finijurásico-cretácico","authors":"David Gómez-Vivo, Fernando Gervilla, A. Azor, Rebeca Hernández-Díaz, R. Piña, C. Alvarez","doi":"10.18268/bsgm2023v75n1a161122","DOIUrl":"https://doi.org/10.18268/bsgm2023v75n1a161122","url":null,"abstract":"El yacimiento de Zn-Pb de Castellanos, situado al noroeste de la isla de Cuba, encaja en un paquete de pizarras negras intercalado en la parte superior de una potente secuencia siliciclástica (>4km), constituida principalmente por areniscas y limolitas de edad Jurásico Inferior y Medio (Formación San Cayetano). El yacimiento es estratiforme, se orienta en dirección NE-SO concordantemente con la estratificación de las pizarras encajantes y está constituido por dos bloques (el bloque Farallones al NE y el bloque Susana al SO) separados por una zona de falla con rumbo N120ºE; una zona de falla con la misma dirección limita también el bloque Farallones en su contacto NE. Este bloque se superpone a un complejo filoniano constituido por filones de pirita±calcopirita y cuarzo, de <10cm de espesor, y orientados también en dirección N120ºE. El cuerpo estratiforme principal está constituido por pirita, esfalerita y galena, con ganga de carbonatos (principalmente dolomita-ankerita y calcita), cuarzo, barita y, y menores proporciones de sericita, biotita parcialmente alterada a clorita y apatito criptocristalino. Muestra una estructura zonal con una zona basal discontinua rica en pirita y una zona superior heterogénea en la que varían tanto las proporciones modales de sulfuros+carbonatos (localmente con cuarzo), como la abundancia relativa de esfalerita+galena respecto a pirita. En conjunto, presenta una textura groseramente bandeada en la que alternan irregularmente bandas ricas en pirita, bandas con esfalerita y galena, y bandas de dolomita-ankerita (±sericita, biotita-clorita y apatito criptocristalino), mejor definida hacia el SO del cuerpo mineral. En este sentido, y hacia el techo de la mineralización., tiende a aumentar la proporción modal de cuarzo y localmente de barita. De NE a SO también se observa una variación en la composición química de la esfalerita, la cual se hace progresivamente más rica en Zn, a la vez que cristaliza una generación más tardía de esfalerita extremadamente pobre en Fe (<1% en peso). En los límites de bloques, la mineralización está afectada por varios episodios de fracturación y brechificación durante los cuales precipitaron y/o se movilizaron diversas generaciones de calcita, barita, cuarzo y galena. En los episodios más tardíos de esta etapa precipita también calcopirita rellenando fracturas y huecos intersticiales entre los fragmentos de sulfuros previos. La interpretación genética de la mineralización de Castellanos que se propone está basada en la precipitación repetitiva (multifásica) de los sulfuros+carbonatos como consecuencia de la interacción de fluidos/salmueras mineralizantes ascendentes a lo largo de las fracturas que dieron lugar al complejo filoniano con los sedimentos ricos en materia orgánica depositados en el fondo de una subcuenca anóxica desarrollada en la cuenca de margen pasivo donde se depositó la Formación San Cayetano. Las salmueras fueron oxidantes, saturadas en sulfato, y se habrían generado en la","PeriodicalId":48849,"journal":{"name":"Boletin De La Sociedad Geologica Mexicana","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48560149","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 : 2023-04-15DOI: 10.18268/bsgm2023v75n1a300822
Ehsanollah Nasehi, Mohammad Amin Nasehi
Yazdanshahr No.2 section, which consists mostly of Bahram and Sibzar formations is located in the Zarand city, northern Kerman province (Central Iran). Five biozones have been identified based on the conodont community. The first biozone, which includes Padehat (15 meter) and Sibzar formations (75 meter), was distinguished based on genera Bipennatus and Icriodus and the probable corresponding age was considered to span Emsian to Eifelian. The second biozone is recognized by the first appearance of index taxon Polygnathus varcus (varcus Zone: early to middle Givetian). The third biozone starts with the firth appearance of the index genus Icriodus expansus (expansus zone: middle Givetian). The base of the Fourth biozone is recognized by the first appearance of the genus I. subterminus (subterminus Zone: middle to late Givetian) and the last biozone was distinguished with the first appearance of genera Ancyrodella and Polygnathus incompletes in the Givetain-Frasnian boundary (falsiovalis to crepida Zone?: Frasnian to Famenian?). Bahram Formation (94 meter) consists of Fossiliferous limestone (varcus to subterminus Zone) at the lower part, and alternation of dolomite and sandstone (falsiovalis to crepida Zone?) at the upper part. Sibzar Formation consists of Middle Devonian dolomite and limy dolomite containing intercalation of sandstone and limestone layers.
{"title":"Biostratigraphy of Yazdanshahr No.2 section in Kerman area, Central Iran, based on conodont communities","authors":"Ehsanollah Nasehi, Mohammad Amin Nasehi","doi":"10.18268/bsgm2023v75n1a300822","DOIUrl":"https://doi.org/10.18268/bsgm2023v75n1a300822","url":null,"abstract":"Yazdanshahr No.2 section, which consists mostly of Bahram and Sibzar formations is located in the Zarand city, northern Kerman province (Central Iran). Five biozones have been identified based on the conodont community. The first biozone, which includes Padehat (15 meter) and Sibzar formations (75 meter), was distinguished based on genera Bipennatus and Icriodus and the probable corresponding age was considered to span Emsian to Eifelian. The second biozone is recognized by the first appearance of index taxon Polygnathus varcus (varcus Zone: early to middle Givetian). The third biozone starts with the firth appearance of the index genus Icriodus expansus (expansus zone: middle Givetian). The base of the Fourth biozone is recognized by the first appearance of the genus I. subterminus (subterminus Zone: middle to late Givetian) and the last biozone was distinguished with the first appearance of genera Ancyrodella and Polygnathus incompletes in the Givetain-Frasnian boundary (falsiovalis to crepida Zone?: Frasnian to Famenian?). Bahram Formation (94 meter) consists of Fossiliferous limestone (varcus to subterminus Zone) at the lower part, and alternation of dolomite and sandstone (falsiovalis to crepida Zone?) at the upper part. Sibzar Formation consists of Middle Devonian dolomite and limy dolomite containing intercalation of sandstone and limestone layers.","PeriodicalId":48849,"journal":{"name":"Boletin De La Sociedad Geologica Mexicana","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46927715","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 : 2022-12-13DOI: 10.18268/bsgm2022v74n3a200722
J. González-Jiménez, I. Sergeeva, T. Kerestedjian, F. Gervilla
Spherules are documented in ophiolitic mantle rocks such as peridotites and associated chromitites. They consist of: (1) native iron having variable amounts of Ni with/without inclusions of silicate glass or oxides (wüstite), (2) dendritic intergrowth of oxides (magnetite, wüstite and hematite) with/without silicate glass and, (3) silicate glass. Consensually, they are interpreted as indigenous to chromitites and related with high-temperature processes operating in the Earth’s upper mantle. However, their similarity with terrestrial and extraterrestrial spherules found in other settings of the geological record is remarkable. We raise the question on such indigenous origin, relating them to volcanic and cosmic material recycled back to the mantle wedge where chromitites form during subduction.
{"title":"Subducted iron and glassy spherules in the upper mantle?","authors":"J. González-Jiménez, I. Sergeeva, T. Kerestedjian, F. Gervilla","doi":"10.18268/bsgm2022v74n3a200722","DOIUrl":"https://doi.org/10.18268/bsgm2022v74n3a200722","url":null,"abstract":"Spherules are documented in ophiolitic mantle rocks such as peridotites and associated chromitites. They consist of: (1) native iron having variable amounts of Ni with/without inclusions of silicate glass or oxides (wüstite), (2) dendritic intergrowth of oxides (magnetite, wüstite and hematite) with/without silicate glass and, (3) silicate glass. Consensually, they are interpreted as indigenous to chromitites and related with high-temperature processes operating in the Earth’s upper mantle. However, their similarity with terrestrial and extraterrestrial spherules found in other settings of the geological record is remarkable. We raise the question on such indigenous origin, relating them to volcanic and cosmic material recycled back to the mantle wedge where chromitites form during subduction.","PeriodicalId":48849,"journal":{"name":"Boletin De La Sociedad Geologica Mexicana","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2022-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47927669","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 : 2022-12-13DOI: 10.18268/bsgm2022v74n3a010422
M. J. Puy-Alquiza, Velia Yolanda Ordaz-Zubia, Omar Cruces-Cervantes, Antonio Bello-Sandoval, R. Miranda-Avilés, M. D. C. Salazar-Hernández, G. Carreño-Aguilera, G. Zanor, Yanmei Li
The characterization of the pre-Hispanic and colonial adobes used in the construction of buildings in Mexico was carried out to know the differences between their processes and manufactures. The eight samples obtained correspond to adobe blocks 0.45 m long x 0.35 m wide and 0.12 m thick, which were part of the interiors of houses, the structure of fences, and hacienda galleys. These samples were investigated using X-ray Diffraction, X-ray Fluorescence, and Scanning Electron Microscopy techniques to determine the morphometry of the material and its chemical and mineralogical composition. Likewise, some analyzes were performed to determine their mechanical properties (simple compressive strength), physical properties (granulometry, solid density, cohesion, plasticity index, porosity, and moisture content), and biological (organic matter content). The results obtained in terms of the granulometric distribution indicate that pre-Hispanic adobe has a higher content of sand than silt-clay and gravel, while the colonial adobes present a low or null content of gravel with a higher content of silt-clays. Regarding the organic matter content, the colonial adobe presents the highest percentages compared to those of the pre-Hispanic adobes. Taking into account the above the pre-Hispanic adobes have better resistance and durability than colonial adobes due to their granulometric distribution, low organic matter content, good cohesion, high plasticity index, and the use of materials found in their natural environment, while the colonial used recycled materials, coming from the economic activity to which the hacienda was dedicated, for example, agriculture, mining, livestock, this has given rise to different manufacturing techniques and construction styles that reflect the state of conservation of buildings throughout the pre-Hispanic and colonial times. The granulometric distribution that pre-Hispanic adobe provides favorable physical and mechanical qualities for any construction technique, so it is recommended to use this formula to manufacture resistant and durable adobe.
{"title":"Comparative study of pre-Hispanic and colonial adobes in Mexico. Preliminary inferences on the effects of the granulometric distribution and used recycled materials in the state conservation of earth architecture","authors":"M. J. Puy-Alquiza, Velia Yolanda Ordaz-Zubia, Omar Cruces-Cervantes, Antonio Bello-Sandoval, R. Miranda-Avilés, M. D. C. Salazar-Hernández, G. Carreño-Aguilera, G. Zanor, Yanmei Li","doi":"10.18268/bsgm2022v74n3a010422","DOIUrl":"https://doi.org/10.18268/bsgm2022v74n3a010422","url":null,"abstract":"The characterization of the pre-Hispanic and colonial adobes used in the construction of buildings in Mexico was carried out to know the differences between their processes and manufactures. The eight samples obtained correspond to adobe blocks 0.45 m long x 0.35 m wide and 0.12 m thick, which were part of the interiors of houses, the structure of fences, and hacienda galleys. These samples were investigated using X-ray Diffraction, X-ray Fluorescence, and Scanning Electron Microscopy techniques to determine the morphometry of the material and its chemical and mineralogical composition. Likewise, some analyzes were performed to determine their mechanical properties (simple compressive strength), physical properties (granulometry, solid density, cohesion, plasticity index, porosity, and moisture content), and biological (organic matter content). The results obtained in terms of the granulometric distribution indicate that pre-Hispanic adobe has a higher content of sand than silt-clay and gravel, while the colonial adobes present a low or null content of gravel with a higher content of silt-clays. Regarding the organic matter content, the colonial adobe presents the highest percentages compared to those of the pre-Hispanic adobes. Taking into account the above the pre-Hispanic adobes have better resistance and durability than colonial adobes due to their granulometric distribution, low organic matter content, good cohesion, high plasticity index, and the use of materials found in their natural environment, while the colonial used recycled materials, coming from the economic activity to which the hacienda was dedicated, for example, agriculture, mining, livestock, this has given rise to different manufacturing techniques and construction styles that reflect the state of conservation of buildings throughout the pre-Hispanic and colonial times. The granulometric distribution that pre-Hispanic adobe provides favorable physical and mechanical qualities for any construction technique, so it is recommended to use this formula to manufacture resistant and durable adobe.","PeriodicalId":48849,"journal":{"name":"Boletin De La Sociedad Geologica Mexicana","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2022-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48067125","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 : 2022-12-13DOI: 10.18268/bsgm2022v74n3a040422
A. Kurgaeva, S. Khamnueva-Wendt, H. Bork
The protected status of archaeological sites requires using minimally invasive methods of material investigation such as coring. In contrast to excavations, the coring method does not present a complete view of the inner structure, and the limited amount of material in cores represents a small portion of the study object. This complicates the interpretation of material genesis. This problem is particularly relevant for complex structures such as earthworks. Nonetheless, the proper interpretation of the construction materials in earthworks is crucial for geoarchaeological investigations of the anthropogenic transformation of landscapes. We proposed a method for classifying and identifying the earthwork materials, sampled by the coring technique. It was developed using an example of the semi-circular fortification rampart around the former Viking settlement Hedeby, which was an important early medieval international trading center and today is a UNESCO world heritage site. Materials from the coring transect across the semi-circular rampart were described. The physicochemical properties of 139 samples from three cores were determined: grain size distribution, weight percentages of gravel, artefacts, bones, and charcoal, loss on ignition, magnetic susceptibility, and element concentrations. The statistical methods (normalization, correlation, standardization, principal component analysis, cluster analysis) were applied to distinguish and group materials according to their physicochemical properties. The resulting clusters were used as a basis for material classification. Some clusters were mildly transformed according to the morphological properties of the material. Consequently, 20 groups were distinguished based on the physicochemical and morphological properties of the material. The rampart was constructed from soil horizons, cultural deposits, and Pleistocene material, which were used in different proportions along the investigated transect. In addition, the constituents of mixed layers were identified. Overall, the presented method for the statistical classification of the material considerably facilitates and objectifies the identification of material genesis. This is particularly valuable in tackling the challenges of coring-based investigations of earthworks.
{"title":"Identification of materials used for earthwork construction: the semi-circular fortification rampart of Hedeby, Northern Germany","authors":"A. Kurgaeva, S. Khamnueva-Wendt, H. Bork","doi":"10.18268/bsgm2022v74n3a040422","DOIUrl":"https://doi.org/10.18268/bsgm2022v74n3a040422","url":null,"abstract":"The protected status of archaeological sites requires using minimally invasive methods of material investigation such as coring. In contrast to excavations, the coring method does not present a complete view of the inner structure, and the limited amount of material in cores represents a small portion of the study object. This complicates the interpretation of material genesis. This problem is particularly relevant for complex structures such as earthworks. Nonetheless, the proper interpretation of the construction materials in earthworks is crucial for geoarchaeological investigations of the anthropogenic transformation of landscapes. We proposed a method for classifying and identifying the earthwork materials, sampled by the coring technique. It was developed using an example of the semi-circular fortification rampart around the former Viking settlement Hedeby, which was an important early medieval international trading center and today is a UNESCO world heritage site. Materials from the coring transect across the semi-circular rampart were described. The physicochemical properties of 139 samples from three cores were determined: grain size distribution, weight percentages of gravel, artefacts, bones, and charcoal, loss on ignition, magnetic susceptibility, and element concentrations. The statistical methods (normalization, correlation, standardization, principal component analysis, cluster analysis) were applied to distinguish and group materials according to their physicochemical properties. The resulting clusters were used as a basis for material classification. Some clusters were mildly transformed according to the morphological properties of the material. Consequently, 20 groups were distinguished based on the physicochemical and morphological properties of the material. The rampart was constructed from soil horizons, cultural deposits, and Pleistocene material, which were used in different proportions along the investigated transect. In addition, the constituents of mixed layers were identified. Overall, the presented method for the statistical classification of the material considerably facilitates and objectifies the identification of material genesis. This is particularly valuable in tackling the challenges of coring-based investigations of earthworks.","PeriodicalId":48849,"journal":{"name":"Boletin De La Sociedad Geologica Mexicana","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2022-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49130397","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 : 2022-12-13DOI: 10.18268/bsgm2022v74n3a200622
T. Cruz-y-Cruz, Alejandro Terrazas-Mata, L. Pogosyan, S. Sedov, T. Pi-Puig, Irán Rivera-González, Beatriz Menéndez-Iglesias, Jorge Rodríguez-Rivas, H. Cabadas-Báez
Key evidence of human occupation in Africa during the Middle Palaeolithic (Middle Stone Age [MSA]) is available from the south and east of the continent, where semi-arid climate prevails. Rare evidence of MSA human occupation in the humid tropical region was recently reported from Equatorial Guinea. To identify if paleolithic human occupation occurred in the tropical forest, the stratigraphy of the recently discovered archaeological site “Mabewele I” was analyzed using a paleopedological approach. The properties evaluated along a vertical profile are: granulometry, magnetic susceptibility (K), free iron extractable with sodium dithionite (Fed), total organic carbon (TOC), chemical composition by X-ray fluorescence (XRF), X-ray diffraction mineralogy (XRD), ternary plot of the three main oxides (SiO2-Al2O3-Fe2O3), phytoliths and micromorphology. The predominant fraction is sand, with a significant clay content (> 30 %). The K and the Fed presented low values, as well as the TOC. XRF showed few variations along the sequence and XRD showed that the clays are mainly kaolinites, with a very low component of vermiculites. The phytoliths correspond to tropical vegetation with few changes in the vegetal composition between the deep and superficial zones. A charcoal from the lower part of the profile was dated between 12.57-12.24 ka cal BP, while the main artifact horizon was located at the bottom. The analytical results appear contradictory: on the one hand, there is evidence of intense chemical weathering under a humid tropical climate, but the clay cutans in the pores are very scarce and incipient and the iron nodules are mostly anorthic. This indicates that the sequence is composed of pedosediments associated with a high environmental dynamism, with short periods of erosion-sedimentation-pedogenesis. The results allow us to propose that humans inhabited the tropical forest during the MSA and that erosion-sedimentation processes could be related to anthropization processes.
人类在旧石器时代中期(中石器时代[MSA])居住在非洲的关键证据来自非洲大陆的南部和东部，那里普遍存在半干旱气候。最近从赤道几内亚报告了湿润热带地区MSA人类活动的罕见证据。为了确定旧石器时代的人类是否曾在热带森林中居住过，研究人员使用古学方法分析了最近发现的考古遗址“Mabewele I”的地层学。沿着垂直剖面评估的性质是:粒度测定、磁化率(K)、二亚硫酸钠(Fed)可提取的游离铁(游离铁)、总有机碳(TOC)、x射线荧光(XRF)化学成分、x射线衍射矿物学(XRD)、三种主要氧化物(SiO2-Al2O3-Fe2O3)的三元图、植物岩和微观形貌。主要组分为砂，粘土含量显著(约30%)。K和Fed的值较低，TOC也较低。XRF沿序列变化不大，XRD显示粘土以高岭石为主，蛭石含量极低。植物岩与热带植被相对应，深层和浅层植被组成变化不大。剖面下部的木炭的年代在12.57-12.24 ka cal BP之间，而主要的人工制品层位于底部。分析结果似乎是矛盾的:一方面，在潮湿的热带气候下，有强烈的化学风化的证据，但孔隙中的粘土岩屑非常稀少且处于初期阶段，铁结核大多是植物性的。这表明该层序是由具有高环境动力的土壤沉积物组成，具有短时间的侵蚀-沉积-成土作用。这些结果使我们能够提出人类在MSA时期居住在热带森林，并且侵蚀-沉积过程可能与人类化过程有关。
{"title":"Late Pleistocene paleoenvironment at a Middle Stone Age archaeological site in Equatorial Guinea: a paleopedological approach","authors":"T. Cruz-y-Cruz, Alejandro Terrazas-Mata, L. Pogosyan, S. Sedov, T. Pi-Puig, Irán Rivera-González, Beatriz Menéndez-Iglesias, Jorge Rodríguez-Rivas, H. Cabadas-Báez","doi":"10.18268/bsgm2022v74n3a200622","DOIUrl":"https://doi.org/10.18268/bsgm2022v74n3a200622","url":null,"abstract":"Key evidence of human occupation in Africa during the Middle Palaeolithic (Middle Stone Age [MSA]) is available from the south and east of the continent, where semi-arid climate prevails. Rare evidence of MSA human occupation in the humid tropical region was recently reported from Equatorial Guinea. To identify if paleolithic human occupation occurred in the tropical forest, the stratigraphy of the recently discovered archaeological site “Mabewele I” was analyzed using a paleopedological approach. The properties evaluated along a vertical profile are: granulometry, magnetic susceptibility (K), free iron extractable with sodium dithionite (Fed), total organic carbon (TOC), chemical composition by X-ray fluorescence (XRF), X-ray diffraction mineralogy (XRD), ternary plot of the three main oxides (SiO2-Al2O3-Fe2O3), phytoliths and micromorphology. The predominant fraction is sand, with a significant clay content (> 30 %). The K and the Fed presented low values, as well as the TOC. XRF showed few variations along the sequence and XRD showed that the clays are mainly kaolinites, with a very low component of vermiculites. The phytoliths correspond to tropical vegetation with few changes in the vegetal composition between the deep and superficial zones. A charcoal from the lower part of the profile was dated between 12.57-12.24 ka cal BP, while the main artifact horizon was located at the bottom. The analytical results appear contradictory: on the one hand, there is evidence of intense chemical weathering under a humid tropical climate, but the clay cutans in the pores are very scarce and incipient and the iron nodules are mostly anorthic. This indicates that the sequence is composed of pedosediments associated with a high environmental dynamism, with short periods of erosion-sedimentation-pedogenesis. The results allow us to propose that humans inhabited the tropical forest during the MSA and that erosion-sedimentation processes could be related to anthropization processes.","PeriodicalId":48849,"journal":{"name":"Boletin De La Sociedad Geologica Mexicana","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2022-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45448722","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 : 2022-12-13DOI: 10.18268/bsgm2022v74n3a060622
M. Courty
The effects of environmental events on living conditions during occupation periods are studied by comparing alluvial soils and occupation floors that formed during the late Holocene in the Moche valley (North Peruvian coast). The microcontextual study comprises (1) microsurface identification in the field; (2) micromorphological analysis of thin sections; (3) multi-scale characterization of soil components based on digital stereo microscope and scanning electron microscope analysis. The alluvial sequence consists of a 6 m thick alternation of organic silty-clay, fine sandy strata with well-preserved ashy charcoal strata and massive grey sandy beds. This cyclical pattern reflects alternation of stable episodes with a dense reed-bed vegetation, regularly affected by wildfires and drought marked by sand invasions from coastal dunes during El Niño events. The 14C dates show that these contrasting conditions lasted for one millennium up to establishment of the Mochica empire at the Huaca at 300 years cal. BC. Vesicular slags produced by flash-melting of the soil components, biosourced quartz and nanostructured polymers formed from flash-ionization of the reed vegetation, all with FeCrNi metals coatings, were retrieved in the fired surfaces. They trace impact at the soil surface of electrically charged particles, lightning-flashes, nanoaerosol production by enhanced atmospheric electrification, i.e., flash-heating, shock vaporization, plasma-polymerization of the vegetation and the host matrix. The study shows the occurrence in the basal Uhle platform occupation deposits at the foot of the Huaca de la Luna of similar cemented ashy microfacies associated with a funerary deposit with food offerings in ritual vessels and an intriguing scoriaceous slag. The evidence for ritual disposal of imperishable offerings to deaths is interpreted as the memorial record of the Mochica knowledge of long-lived materials produced by lightning-triggered plasma processes. This integrated study of the environmental and cultural contexts refutes previous assumptions of long-term engineering of the arable alluvial plain to counteract sand invasion and torrential floods. In contrast, the establishment of the Moche pyramids is shown to have occurred during a period of floodplain stability marked by high-energy natural events and lightning processes that offered access to durable soil resources of important social values.
通过比较莫切河谷（秘鲁北部海岸）全新世晚期形成的冲积土和占领层，研究了占领期间环境事件对生活条件的影响。微观上下文研究包括（1）现场微观表面识别；（2） 薄片的微观形态分析；（3） 基于数字立体显微镜和扫描电子显微镜分析的土壤成分多尺度表征。冲积序列由6 m厚的有机粉质粘土、细砂质地层和保存完好的灰炭层以及块状灰色砂层组成。这种周期性模式反映了稳定期的交替，芦苇床植被茂密，经常受到野火和干旱的影响，在厄尔尼诺事件期间，海岸沙丘的沙子入侵是其特征。公元前14世纪的日期表明，这些对比鲜明的条件持续了一千年，直到公元前300年在华卡建立了莫奇卡帝国。在烧制表面回收了土壤成分闪速熔化产生的气泡状炉渣、生物源石英和芦苇植被闪速电离形成的纳米结构聚合物，所有这些都带有FeCrNi金属涂层。它们追踪了带电粒子对土壤表面的影响、闪电、通过增强大气带电产生的纳米气溶胶，即闪光加热、冲击蒸发、植被和宿主基质的等离子体聚合。研究表明，在Huaca de la Luna山脚下的基底Uhle平台占用矿床中，出现了类似的胶结灰微相，与带有礼器中的食物和有趣的焦渣的陪葬矿床有关。仪式上处理不朽的死亡祭品的证据被解释为莫奇卡人对闪电触发等离子体过程产生的长寿材料的认识的纪念记录。这项对环境和文化背景的综合研究驳斥了以前对可耕地冲积平原进行长期工程以抵御沙子入侵和暴雨的假设。相比之下，Moche金字塔的建立被证明是在洪泛平原稳定时期发生的，其特点是高能自然事件和闪电过程为获得具有重要社会价值的耐用土壤资源提供了途径。
{"title":"Fire microfacies and pyroresidues tracing atmospheric electrification impacts on the Moche Valley and on the Mochica (North Peru)","authors":"M. Courty","doi":"10.18268/bsgm2022v74n3a060622","DOIUrl":"https://doi.org/10.18268/bsgm2022v74n3a060622","url":null,"abstract":"The effects of environmental events on living conditions during occupation periods are studied by comparing alluvial soils and occupation floors that formed during the late Holocene in the Moche valley (North Peruvian coast). The microcontextual study comprises (1) microsurface identification in the field; (2) micromorphological analysis of thin sections; (3) multi-scale characterization of soil components based on digital stereo microscope and scanning electron microscope analysis. The alluvial sequence consists of a 6 m thick alternation of organic silty-clay, fine sandy strata with well-preserved ashy charcoal strata and massive grey sandy beds. This cyclical pattern reflects alternation of stable episodes with a dense reed-bed vegetation, regularly affected by wildfires and drought marked by sand invasions from coastal dunes during El Niño events. The 14C dates show that these contrasting conditions lasted for one millennium up to establishment of the Mochica empire at the Huaca at 300 years cal. BC. Vesicular slags produced by flash-melting of the soil components, biosourced quartz and nanostructured polymers formed from flash-ionization of the reed vegetation, all with FeCrNi metals coatings, were retrieved in the fired surfaces. They trace impact at the soil surface of electrically charged particles, lightning-flashes, nanoaerosol production by enhanced atmospheric electrification, i.e., flash-heating, shock vaporization, plasma-polymerization of the vegetation and the host matrix. The study shows the occurrence in the basal Uhle platform occupation deposits at the foot of the Huaca de la Luna of similar cemented ashy microfacies associated with a funerary deposit with food offerings in ritual vessels and an intriguing scoriaceous slag. The evidence for ritual disposal of imperishable offerings to deaths is interpreted as the memorial record of the Mochica knowledge of long-lived materials produced by lightning-triggered plasma processes. This integrated study of the environmental and cultural contexts refutes previous assumptions of long-term engineering of the arable alluvial plain to counteract sand invasion and torrential floods. In contrast, the establishment of the Moche pyramids is shown to have occurred during a period of floodplain stability marked by high-energy natural events and lightning processes that offered access to durable soil resources of important social values.","PeriodicalId":48849,"journal":{"name":"Boletin De La Sociedad Geologica Mexicana","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2022-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47397096","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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