Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

Afín de clarifier certaines caractéristiques essentielles de l'histoire terciaire de l'Axe Néovolcanique, ce texte analyse plusieurs références graphiques relatives a des zones proches de cette région dans les états de Michoacán, Guerrero, Morelos, Puebla et Hidalso, en fonction de critères strietement structurels, tels ceux qui établissent la disharmonie entre couches cénozoiques et mésozoiques, sans superposition des traits structurels des unes sur les autres, et ceux qui se basent en simples concepts sur le comportement géométrique et topographique de contacts géologiques. Il etablit l'existence de plusieurs écailles et fenêtres tectoniques qui semblent definir une seule surface régionele de cheyauchement, surface sur laquelle des calcaires du Crétacé Inférieur vinrent a couvrir les molasses terciaires et les roches sousjacentes. Ce trait structurel met en évidence une forte composante tangentielle de la phase tectonique de paroxysme probablement du Miocene en cette région.

This study comprises the description of the fossil alga Goniolina geometrica (Römer) Buvignier collected from the western part of Chiapas near the Oaxaca State boundary. A Late Jurassic age is assigned to this form, which is based on its occurrence together with other Late Jurassic fossils in well established sequences in France and Switzerland.

This paper is a taxonomic revision of the late Tertiary equid species, known so far from the Zacualtipán basin in the State of Hidalgo. The studied material includes the equids from the Tehuichila fauna housed in the Museo de Geología, UNAM, as well as the species Calippus (Grammohippus) castilli and Dinohippus interpolatus, collected (in situ) in the Zietla locality. Based on the presence of these two species, the age of this fossil site is assigned to the early Hemphillian. The mastofauna of Zietla is the only known reference in which a fossil assemblage is reliably tied into the stratigraphical sequence of the Zacualtipán area (from which the Tehuichila fauna is derived)... In order to continue, download full text in PDF.

Plusieurs phases tectoniques superposées dans le temps et dans l'espace, affectent le secteur d'Agua Prieta - Naco (Sonora Septentrional). Une phase albo-cenomanienne est responsable de la discordance présente á la base du Crétacé Superieur et constitue l'echo de deformations plus intenses se manifestant dans des zones plus internes (Sinaloa-California). Une phase Crétacé Supérieur a Tertiaire basal parait responsable du chevauchement d'une unité septentrionale sur le bassin de type molassique de Cabullona. Finalment, des mouvements á grand rayon de courbure affectent les series paloiques et mesozoiques et leur couverture volcanique tertiaire. Ces mouvements sont suivis ou accompagnés par plusieurs réseaux de failles normales recoupant de maniere independante les structures anterieures.

  The typification of concepts resulting in formal stratigraphic units, rests upon outcrops or cores, not upon strata, because of the very nature of Stratigraphic Taxonomy… In order to continue, download the full paper in PDF.  

The studied area, about 2000 km2, is covered in its central part, by the Las Estacas Formation from the late Pleistocene (Qpe). These rocks consist mainly of anhydrites and "caliche". They are surrounded by mountain ranges of Cretaceous limestones and sandstones. The hydrogeological characteristics of the exposed areas and from a hydrogeochemical point of view, three aquifers can be detected. The first one is developed in evaporites and debris. The second formed by the interdigitation of sandstones and limestones, generating less salty water; and finally the third is emplaced in the Cretaceous limestones and sandstones. The water from the Las Estacas Formation is supplied by the underlaying Cretaceous rocks and by direct infiltration of pluvial precipitation. This formation has several small depressions that contribute to an effective reload and prevent the active erosion of the area. This fact is proved by the lack of gullies and by the insignificant depth of the existing ones. This fact is believed to be important considering the lack of cohesion of this formation. The maximum thickness of the evaporites of the Las Estacas Formation is about 30 m it pintches out along the borders of the basin and towards the topographic highs. The existence of evaporites certifies the endorreic character of the basin and the dry climate during the late Pleistocene. Bassed upon 54 chemical analyses of water samples, the existence of four different families of water was established. This interpretation is supported by semilogarithmic diagrams.

 A Middle Jurassic-Early Cretaceous? Volcanosedimentary sequence crops out in the Playa Azul áreas, Michoacan State. It consists of andesitic lavas, rhyolitic pyroclastics, shallow near-shore marine biomicrites and red, immature phyllovocarenitic sandstones, containing dinosaur footprints… In order to continue, download the full paper in PDF.

This preliminary report, based upon an extensive fossil collection, adds the following to the Rancho El Ocote local rauna… In order to continue, download the full paper in PDF.

Présentation d'un programme (FORTRAN IV) pour l'interprétation qualitative des difractogrammes de fluorescence "X" employés dans les laboratoires d'analise. L'utilisation de cette technologie appliqué permet d'une part un gain de temps, et d'autre part de favouriser les travaux routiniers des analistes.

A species of the genus Bellerophon Monfort, 1808, is described from the Paso Hondo Formation (Middle Permian) from a locality along the Comalapa River, near the town of the same name in the southeastern of Chiapas. The species was found associated with the fusulinids Schwagerina, Eoverbekina, Stafella and Nankinella, ostracods, corals, braquiopods, crinoids and marine (Tubiphytes) and continental plants.