Boletín de la Sociedad Geológica Mexicana最新文献

{"title":"The Hettangian-Bajocian flora of the Shemshak group, Kerman, Iran","authors":"H. Ameri, Parisa Shaghayeghi","doi":"10.18268/bsgm2023v75n3a110923","DOIUrl":"https://doi.org/10.18268/bsgm2023v75n3a110923","url":null,"abstract":"Numerous examples of macro plant fossils can be found in the Kerman region’s Early and Middle Jurassic successions. The Ab-e-Haji, Badamu, and Hojedk formations were among these patterns. One of the suitable regions for paleobotanical study is the Chatroud section. In this region, the Lower-Middle Jurassic is approximately 210 meters thick. 18 species of macro plant fossils from 14 genera, including Nilssonia polymorpha, Pterophyllum nathorsti, Podozamites distans, Elatocladus zamioides, Elatides thomasii, Nilssonia feriziensis, Nilssonia herriesi, and Beania sp., which are identified and described in this study, along with Pterophyllum schenki, Anomozamites marginatus, and Klukia exilis. In this region, there are two plant assemblage zones known as Anomozamites marginatus-Pterophyllum schenki Zone and Klukia exilis Zone. The Hettangian-Bajocian age is preserved at the Chatroud section.","PeriodicalId":9315,"journal":{"name":"Boletín de la Sociedad Geológica Mexicana","volume":"30 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139205265","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modelamiento análogo de la tectónica salina asociada a ambientes compresivos y zonas transversales en la zona axial de la Cordillera Oriental, Colombia","authors":"Carlos Andrés Escalante Cárdenas, Dilan Arturo Martinez-Sánchez, Giovanny Jiménez","doi":"10.18268/bsgm2023v75n3a070623","DOIUrl":"https://doi.org/10.18268/bsgm2023v75n3a070623","url":null,"abstract":"Las secuencias sedimentarias con niveles evaporíticos presentan estructuras tridimensionales complejas debido a movimientos halocinéticos (tectónica salina). En el Anticlinal de Zipaquirá, ubicado en la Cordillera Oriental de Colombia, se reportan niveles salinos en las unidades del Cretácico Temprano. Este trabajo analizó estructuralmente el Anticlinal de Zipaquirá, basado en modelos análogos que simulan la relación entre la tectónica salina y las zonas trasversales que limitan y segmentan esta estructura. Los modelos se realizaron en una mesa de deformación tipo seducción con velocidad constante de desplazamiento. Los mismos simulan anisotropías de basamento mediante un bloque rígido de madera constituido por dos rampas frontales de 30° de inclinación conectadas por una rampa lateral. Adyacente, se dispone una capa de fluido no-newtoniano y capas de arena cuarzosa fina de color variable. Se efectuaron tres configuraciones con diferentes distribuciones de la capa de fluido no-newtoniano: A) continua delgada, B) discontinua y C) continua espesa. Para cada configuración se llevaron a cabo al menos 15 experimentos. Los resultados del modelamiento análogo mostraron un cuerpo salino en el núcleo del anticlinal que es cortado por fallas inversas, formando una estructura de lámina de sal paralela a la estratificación. Las estructuras observadas, como almohadas de sal, glaciares de sal, láminas de sal y lenguas de sal, indican estilos estructurales compresivos de madurez intermedia a alta. El modelo discontinuo resultó ser el más coherente, ya que la rampa lateral no presentaba niveles evaporíticos, lo cual coincide con la observación en la naturaleza. La Falla transversal del Neusa se representó en el modelo como la rampa lateral, explicando la localización de los niveles salinos en la zona sur del Anticlinal de Zipaquirá. Por último, la evolución de los modelos mostró rotaciones horarias cercanas a la rampa lateral, consistentes con los patrones de rotaciones horarias reportados en la zona axial de la Cordillera Oriental.","PeriodicalId":9315,"journal":{"name":"Boletín de la Sociedad Geológica Mexicana","volume":"319 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139207785","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Invertebrate fauna of the Albian–Lower Cenomanian deposits in the Fars and Isfahan provinces (Firuzabad and Fasakhod sections), Zagros Basin, Central Iran","authors":"Babak Sedghi, A. Bahrami, M. Yazdi, Francisco J. Vega","doi":"10.18268/bsgm2023v75n3a220623","DOIUrl":"https://doi.org/10.18268/bsgm2023v75n3a220623","url":null,"abstract":"The Albian- Cenomanian deposits of the Kazhdumi Formation at Zagros Basin (Firuzabad section and Central Iran (Fasakhod section), represents a carbonate sedimentary succession and contain rich and diverse invertebrate macro fauna. Detailed studies on about 200 specimens of invertebrate macro fauna revealed from two stratigraphic intervals led to recognition of 5 species of gastropods; (Liopeplum? sp., Columbellina sp., Cryptaulax? sp., Turritella? sp., Pleurotomaria sp.), 3 species of ammonites; (Knemiceras duberterti, Sphenodiscus sp., Knemiceras persicum), 10 species of bivalves assemblages; (Ceratostreon flabellatum, Cardium? sp., Exogyra (Costagyra) olisiponensis, Neithea (Neithea) quinquecostata, Trigonia sp., Buchia? sp., Cardium? sp., Pseudogyra sp., Ontaria? sp., Nucula? sp., Pleuromia? sp., 1 species of echinoids; Dorocidaris taouzensis with a prolific horizon of Notopocorystes xizangensis of raninoid crabs. The absence of large gastropods and bivalves fauna and abundance of suspension-feeders indicated instability of the substrate, shallow marine paleoenvironment.and a medium energy condition.","PeriodicalId":9315,"journal":{"name":"Boletín de la Sociedad Geológica Mexicana","volume":"87 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139201969","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fossil freshwater gastropods from northern Mexico – A case of a “silent” local extirpation, with the description of a new species","authors":"A. Czaja, A. Covich, J. L. ESTRADA-RODRÍGUEZ, Ulises Romero-Méndez, J. Sáenz-Mata, Iris Gabriela Meza-Sánchez, Verónica Ávila-Rodríguez, orge Luis Becerra-López, David Ramiro Aguillón Gutiérrez, J. G. Castañeda-Gaytán","doi":"10.18268/bsgm2019v71n3a2","DOIUrl":"https://doi.org/10.18268/bsgm2019v71n3a2","url":null,"abstract":"espanolEl declive de la diversidad de especies dulceacuicolas es un fenomeno mundial, pero es especialmente pronunciado en las regiones aridas como en el Desierto Chihuahuense de Coahuila y Durango, norte-centro de Mexico. Existen pocos datos historicos sobre la distribucion y ninguna informacion sobre extinciones de gasteropodos dulceacuicolas mexicanos. En tales casos, los datos paleontologicos pueden ser muy utiles y, a menudo, son la unica forma de documentar las distribuciones pasadas y los eventos locales de extincion u extirpacion. Este nuevo enfoque paleoecologico, llamado Paleobiologia de Conservacion, puede proporcionar perspectivas importantes para los esfuerzos de conservacion de ecosistemas analogos recientes. El sitio de estudio contiene depositos fosiles (Holoceno Tardio) del Distrito Laguna, un area pequena en Coahuila y Durango. De estos depositos fosiles describimos una nueva especie y reportamos varios registros nuevos de gasteropodos cochliopidos, hidrobidos, planorbidos y neritidos. La mayoria de estas especies y algunos generos no se conocen como fosiles de Mexico y todos ellos desaparecieron en tiempos muy recientes. En conjunto con datos de nuestros estudios paleomalacologicos anteriores, presentamos aqui un ejemplo de una extirpacion local “silenciosa” en el norte de Mexico la cual comenzo en el Holoceno Medio. Esta perdida de especies aumento rapidamente en la segunda mitad del siglo XX. De las 32 especies de caracoles dulceacuicolas presentes en el area de estudio durante el Holoceno, solo 4 (12.5%) aun existen. Al menos 24 (75.0%) de ellos desaparecieron del area en el siglo XX debido a la perdida de habitat causada por actividades antropogenicas. Nuestros resultados muestran que especialmente los hidrobidos con intervalos geograficos pequenos (especies endemicas locales) son altamente sensibles y vulnerables a tales acontecimientos de extirpacion. La extirpacion de los caracoles dulceacuicolas en el area de estudio ocurrio silenciosamente (sin registros), mientras que al mismo tiempo unos doscientos kilometros mas al norte, uno de los mayores focos de diversidad de gasteropodos en America del Norte permanecio en la cuenca de Cuatrocienegas. Las mismas amenazas que llevaron a la extirpacion local en nuestra area de estudio aun amenazan a las comunidades de caracoles dulceacuicolas del valle de Cuatrocienegas. EnglishThe decline of freshwater species diversity is a worldwide phenomenon but it is especially pronounced in arid regions such as in the Chihuahuan Desert of Coahuila and Durango, Northern Mexico. There are few historical data on the distribution but no data on extinctions of Mexican freshwater gastropods. In such cases, paleontological data can be very helpful and are often the only way to document past distributions and local extinction or extirpation events. This new paleoecological approach, called Conservation Paleobiology, can provide important perspectives in favor of conservation of recent analogue ecos","PeriodicalId":9315,"journal":{"name":"Boletín de la Sociedad Geológica Mexicana","volume":"12 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73050132","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mid-late Cenomanian larger benthic foraminifers from the El Abra Formation, Valles-San Luis Potosí Platform, central-eastern Mexico: Taxonomy, biostratigraphy and paleoenvironmental implications","authors":"Lourdes Omaña, Rubén López Doncel, J. R. T. Hernández, Gloria Alencáster, Iriliana López Caballero","doi":"10.18268/bsgm2019v71n3a5","DOIUrl":"https://doi.org/10.18268/bsgm2019v71n3a5","url":null,"abstract":"espanolThe Valles-San Luis Potosi Platform is part of an extensive carbonate platform system that rimmed the ancestral Gulf of Mexico during the middle (Albian) through Upper Cretaceous. The El Abra Formation consists of a shallow-water deposit; it contains a benthic foraminiferal assemblage that includes 18 species, which are described and illustrated in this paper. The studied successions from the upper part of the El Abra Formation were dated as mid-late Cenomanian. On the basis of these findings, two zones are proposed Pseudolituonella reicheli Assemblage Zone and Nezzazatinella picardi Interval Zone. The first Assemblage Zone is characterized by an abundant benthic foraminiferal association. It is overlain by the Nezzazatinella picardi Interval Zone where the species richness of the fora-miniferal assemblage is reduced and later disappears. The benthic foraminiferal demise is coincident with major sea-level changes and an increase in siliciclastic input from the hemipelagic deposit of the Soyatal Formation, which contains abundant pithonellids and r and r-k strategist planktic foraminifera (Whiteinella archaeo-cretacea Partial Range Zone). Two stratigraphically correlative facies have been recognized in the El Abra Formation: the Taninul and the El Abra Facies. A warm, shallow-water, open marine platform deposit (Taninul Facies) is inferred. It includes peloidal-foraminiferal packstone, packstone-grainstone, and packstone- wackestone. A restricted environment (El Abra Facies) can be deduced from the abundant miliolids and ostreids. The texture is a wackestone-packstone. Another microfacies (Soyatal Formation) consists of wackestone-packstone with an acme of pithonellids and the occurrence of r and r-k strategist planktic foraminifers deposited during the platform drowning. EnglishLa Plataforma Valles-San Luis Potosi es parte de un sistema de plataformas extenso que se encontraba bordeando el antiguo Golfo de Mexico en el Albiano hasta el Cretacico Superior. La caliza El Abra es un deposito de aguas poco profundas; esta contiene un conjunto de foraminiferos bentonicos que incluye 18 especies, que se describen e ilustran en este documento. Las sucesiones estudiadas de la parte superior de la Formacion de El Abra fueron datadas como del Cenomaniano medio- tardio; se proponen dos zonas (Zona de Conjunto Pseudolituonella reicheli y Zona de Intervalo Nezzazatinella picardi). La primera Zona de Conjunto se caracteriza por una asociacion abundante de foraminiferos bentonicos. Esta sobreyacida por la Zona de Intervalo Nezzazatinella picardi donde se reduce la riqueza de especies de las asociaciones de foraminiferos y luego desaparece. La desaparicion de foraminiferos bentonicos es coincidente con grandes cambios de nivel del mar y un aumento en el aporte de sedimentos desde el deposito hemipelagico de la Formacion Soyatal que contiene abundantes pithonelidos y foraminiferos planctonicos de estrategia r y r-k (Zona de Alcance Parcial (Whiteinella arch","PeriodicalId":9315,"journal":{"name":"Boletín de la Sociedad Geológica Mexicana","volume":"11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84902763","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Clypeasteroids (Echinodermata: Echinoidea) from the Cretaceous in Mexico","authors":"A. Martínez-Melo","doi":"10.18268/bsgm2019v71n3a11","DOIUrl":"https://doi.org/10.18268/bsgm2019v71n3a11","url":null,"abstract":"Alejandra Martínez-Melo Short note Clypeasteroids (Echinodermata: Echinoidea) From the Cretaceous In","PeriodicalId":9315,"journal":{"name":"Boletín de la Sociedad Geológica Mexicana","volume":"37 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90951185","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Systematic paleontology and taphonomic studies of Ypresian mollusks at the Kopet-Dagh Basin, NE Iran","authors":"A. Salahi, A. Ghaderi, A. Ashouri, Alejandro Cristín, S. Senemari","doi":"10.18268/bsgm2019v71n3a9","DOIUrl":"https://doi.org/10.18268/bsgm2019v71n3a9","url":null,"abstract":"espanolLos fosiles de invertebrados marinos se han considerado herramientas importantes para la recolecta de datos por edades y la interpretacion estratigrafica de los depositos de paleogenos de Asia Central, sin embargo, aun no se ha proporcionado informacion de la cuenca de Kopet-Dagh (NE Iran). En esta investigacion, se discuten los horizontes fosiliferos de la Formacion Chehelkaman en las secciones Sheikh y Ghaleh-Zou (que nunca antes se habian reconocido), ambos en el area Sheikh Syncline. Estos lechos sedimentarios se superponen a la Formacion de Pesteligh siliciclastica terrestre y son la primera evidencia de inundacion marina de la transgresion del Paleogeno en el centro de Kopet-Dagh. Los estudios paleontologicos sistematicos de fosiles de moluscos en esta sucesion condujeron a la identificacion de: diez generos, doce especies, dos subespecies de bivalvos, cinco generos y cinco especies de gasteropodos. El conjunto pertenece a cuatro horizontes fosiliferos diferentes: (1) Conjunto Dominado por Turritellidae (TDA), (2) Pycnodonte-Turkostrea horizonte, (3) Cordiopsis - Cardium horizonte, (4) Camas de concha Globularia en la seccion Sheikh y solo horizonte TDA en la seccion de Ghaleh-Zou. La edad de toda la sucesion es Ypresian tardio (Cuisian medio temprano). Esta edad esta basada en Cordiopsis subathooensis - Turritella subathooensis co-ocurrencia de la zona con las zonas de nannofosiles NP12 y NP13. El TDA en ambas secciones confirma la abundancia de nutrientes y su orientacion bimodal demuestra los efectos de las ondas oscilatorias en lugar de las paleocorrientes unidireccionales. Las altas tasas de bioerosion, incrustacion, fragmentacion, desarticulacion y corrosion de las conchas en Pycnodonte - Turkostrea horizonte revela altos volumenes de nutrientes y condiciones ricas en energia. Este intervalo, cubierto por la Cordiopsis - Cardium horizonte en una disposicion de pavimento, representa las condiciones estables despues de una tormenta. Los lechos de conchas de Globularia intercalados con lechos de marga, indican estabilidad y una tendencia cada vez mas profunda del medio ambiente terminando en lutitas y margas mas profundas de la Formacion Khangiran. EnglishMarine invertebrate fossils have long been considered important tools for age dating and stratigraphic interpretation of the Paleogene deposits of Central Asia, however information has not yet been provided from the Kopet-Dagh Basin (NE Iran). In this research, fossiliferous horizons of the Chehelkaman Formation at the Sheikh and Ghaleh-Zou sections (which have never been recognized previously), both in the Sheikh Syncline area, are discussed. These sedimentary beds overlay the terrestrial siliciclastic Pesteligh Formation and are the first evidence of marine flooding of the Paleogene transgression in the central Kopet-Dagh. Systematic paleontological studies of molluscan fossils in this succession led to the identification of ten genera, twelve species and two subspecies of biva","PeriodicalId":9315,"journal":{"name":"Boletín de la Sociedad Geológica Mexicana","volume":"12 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88798421","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Nueva especie de Laurinoxylon (Lauraceae) de la Formación El Bosque (Eoceno), Chiapas, México","authors":"Diana Karen Pérez-Lara, Emilio Estrada-Ruiz, Carlos Castañeda-Posadas","doi":"10.18268/bsgm2019v71n3a8","DOIUrl":"https://doi.org/10.18268/bsgm2019v71n3a8","url":null,"abstract":"We describe a new species of the fossil genus Laurinoxylon from the El Bosque Formation (Eocene), Chiapas, Mexico. The new species is characterized by: diffuse porous wood with indistinct growth rings; solitary vessels and in radial multiples of two to three vessels per radial multiple; simple perforation plates; alternate intervessel pits: septate and non-septate fibers; round vessel-ray parenchyma pits, horizontally and verti-cally elongated with reduced borders; axial parenchyma scanty paratracheal, vasicentric, apotracheal diffuse; heterogeneous rays, and oil cells associated to the ray parenchyma and among the fibers. This fossil genus has been described before from the Cretaceous to the Neogene, worldwide. This is the first formal record of Laurinoxylon and the first Eocene macrofossil report of Lauraceae from Mexico. This new species supports the hypothesis that the Lauraceae had a wide distribution during the past and that Mexico may be an important region for the diversifi-cation of the family as evidenced by its fossil record dating from the Late Cretaceous and by the high number of genera and species that currently grow in Mexico.","PeriodicalId":9315,"journal":{"name":"Boletín de la Sociedad Geológica Mexicana","volume":"31 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86359304","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evolución del relieve en las fallas San Marcos, El Madroño y Las Vigas, norte de la junta triple del bloque Jalisco, México","authors":"Miguel Castillo, José Luis Álvarez Arce, Esperanza Muñoz-Salinas","doi":"10.18268/bsgm2019v71n3a3","DOIUrl":"https://doi.org/10.18268/bsgm2019v71n3a3","url":null,"abstract":"espanolLa evolucion del relieve en la zona de la junta triple del Bloque Jalisco esta condicionada por procesos tectonico-volcanicos del Plioceno y Cuaternario que han dado lugar a la formacion a depresiones tectonicas ocupadas por lagos. La edad del fallamiento en esta zona no se conoce con detalle. El uso de indices morfometricos ha demostrado ser una tecnica eficaz para evaluar la actividad tectonica en relieves jovenes, a pesar de ello, pocos estudios han utilizado este enfoque para precisar la evolucion del relieve en la porcion centro-occidente de Mexico. En este estudio se analizan los perfiles longitudinales de los rios que inciden oblicuos al rumbo de las fallas San Marcos, Las Vigas y El Madrono, localizadas al norte de la zona de la junta triple del bloque Jalisco, y se analiza la morfometria de los abanicos localizados al pie de los escarpes de falla. Se estima la edad de retroceso de knickpoints y se analizan muestras de roca (n = 6) para la caracterizacion quimica de las distintas unidades volcanicas. Los circones del domo riolitico La Coronilla, el cual se emplaza sobre la falla El Madrono, arrojaron una edad de 0.66 ± 0.06 ka lo cual permite constrenir la edad minima del fallamiento. Los resultados obtenidos revelan que los indices ksn y kL son los que mejor reproducen la topografia resultante del levantamiento a lo largo de las fallas. El tiempo en que comenzaron a retroceder los knickpoints es de entre 0.7 a 1 Ma. El volcanismo del Plioceno es principalmente de afinidad calci-alcalina y de composicion andesitico-basaltica a andesitica, estos productos contrastan con el volcanismo asociado al fallamiento el cual tiende ser relativamente acido (dacitas y riolitas). La concordancia entre la edad del retroceso de los knickpoints, la edad relativa de los abanicos aluviales y la edad del volcanismo del Pleistoceno son evidencias que sugieren que el relieve y los patrones de erosion al norte de la de la junta triple del bloque Jalisco tuvieron una importante actividad en el Cuaternario. EnglishThe landscape evolution of the region of the triple junction of the Jalisco Block is the result of Pliocene and Quaternary tectonic and volcanic processes which have produced the formation of tectonic depressions now occupied by lakes. The age of faults for this zone is not known in detail. The use of morphometric indexes. proved to be useful to detect the tectonic activity in young landscapes settings, however, few studies have used such approach to constrain the landscape evolution for west-central Mexico. In this study we analize the stream long profiles of rivers incising across the strike of the faults of San Marcos, Las Vigas and El Madrono, which are located north of the triple junction of the Jalisco Block. The morphometry of alluvial fans at the base of the fault scarps is also analyzed. The knickpoint recession age is estimated as well as the analysis of rocks (n = 6) to characterize the chemical composition of different volcanic units.","PeriodicalId":9315,"journal":{"name":"Boletín de la Sociedad Geológica Mexicana","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77516747","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Schlueterella stinnesbecki n. sp. (Ammonoidea, Diplomoceratidae) from the Turonian-Coniacian of northeastern Mexico","authors":"C. Ifrim","doi":"10.18268/bsgm2019v71n3a13","DOIUrl":"https://doi.org/10.18268/bsgm2019v71n3a13","url":null,"abstract":"espanolSe describe una nueva especie del genero Schlueterella Wiedmann, 1962. Los veinte ejemplares de este ammonoideo heteromorfo fueron colectados en el norte de Coahuila, Mexico. Parece que Schlueterella stinnes-becki n. sp. fue una especie endemica en el Turoniano tardio-Coniaciano temprano. Con total certeza se trata del registro mas antiguo de este genero y una forma basica en su evolucion desde Neocrioceras. EnglishA new species of the genus Schlueterella Wiedmann, 1962 is here described. Twenty specimens of this heteromorph ammonoid were collected in northern Coahuila, Mexico. Schlueterella stinnesbecki n. sp. seems to have been an endemic form in the late Turonian-early Coniacian. This is the oldest definite record of the genus and a basal form in its evolution away from Neocrioceras.","PeriodicalId":9315,"journal":{"name":"Boletín de la Sociedad Geológica Mexicana","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80182429","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}