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This paper is a revised version of previous interpretations of the Caribbean structure submitted by the authors to various geological conferences and meetings (mostly unpublished). The fundamental idea consists in postulating a maximum thickness of 5.000± m. of Cretaceous-Tertiary sediments, in an essentially geosynclinal basin, some 100 km, off shore, in approximate coincidence with the free-air gravity minimum and the magnetic anomaly maximum. The stratigraphic and structural interpretation is based on the correlation originally proposed with the Salamanca drill-hole and available surface gravity and geology information (DURÁN,1964), but corrected with recent JOIDES' Program data. For the isostatic anomaly a different generalized interpretation is suggested instead, in terms of the new plate tectonics ideas. It is believed that oil-bearing structures may be present off shore, in spite of the negative results obtained heretofore in land, or on shallow shelf. This reinterpretation (still tentative) is mainly based on partial recent Infermation from R/V Trident (Rhode Island Univ.) and R/V Conrad (Lamont-Doherty, Columbia Univ.) cruises; on publications and recent discussion and communications,principally with Drs. M. Ewing, M. Talwani, D. Krause and E. Christofferson. El presente trabajo es una interpretación revisada de la que fue sometida por los autores, en mayo del año en curso, al I Congreso Colombiano sobre Recursos Naturales (Bogotá), acerca de la Geología del Caribe. La idea fundamental de la interpretación consiste en postular un máximo espesor de sedimentos cretácico-terciarios de unos 5.000 metros, aproximadamente a 100 kilómetros mar adentro, en coincidencia aproximada con el mínimo gravimétrico de aire libre y el máximo magnético, correlacionados con la estructura y la estratigrafía continentales, en la Isla de Salamanca. La reinterpretación mantiene la modificación esencial a la sugerencia anterior (DURÀN,1964) sobre el significado de la anomalía isostática negativa, que señalaba el máximo espesor de la columna sedimentaria en coincidencia con aquella. Para la anomalía isostática se sugiere, en cambio, una interpretación diferente, en relación con la tectónica de placas en la comarca, y se corrige la columna de conformidad con los datos de las perforaciones recientes (JOIDES, 1970-71). El trabajo se basa en los datos de los últimos cruceros del R/V Trident (Universidad de Rhode Island) y del R/V Conrad (Lamont-Doherty, Universidad de Columbia), en los cuales los autores tuvieron la oportunidad de participar, en publicaciones, y en comunicaciones personales de los doctores Talwani, Krause y Christofferson, principalmente.

Los autores han viajado por los Andes (1965) y los Alpes (1966) a fin de tener una idea conjunta de Índole geotectónica que permita brindar los resultados de una comparación reciente sobre la organización y desarrollo de ambas estructuras. Los Alpes se adecúan al régimen ortogeosinclinal clásico por su evolución y magmatismo. Los Andes en la Argentina central y Chile, vecino, aparecen como un marginal ambiente liminar (Argand), pericratónico. Una afinidad es evidente entre ambas cadenas especialmente en lo que concierne a la deformación pliocuaternaria que afectara a las mismas con la formación de cuencas falladas rellenadas con series terrígenas potentes. Son analizados los aspectos estructurales de la región andina de Mendoza y Neuquén correspondiente a la Cordillera Principal y expuestos los caracteres salientes de su tectónica de zócalo con sistemas de fallas en compresión (Paleógeno-Mioceno) y sistemas similares en extensión (Plio-Cuaternario). Una rápida visión de la estratigrafía sirvió de base a la exposición tectónica. Fueron señalados los rasgos geológicos de la Precordillera, Cordillera Frontal y Cordillera Costanera de Chile que se asocian al substratum de la Cordillera Principal. Se analizan en el trabajo paralelamente algunos caracteres paleogeográficos que interesan para la historia del continente sudamericano. The present authors have visited the Andes (19651 and the Alps (1966), in search of the geotectonical data necessary for the comparison of the evolution and development of these structures. Taking into account the evolution and magmatiam, the Alps pertain to the classical orthogeosyncline regime. While the Andes, in central Argentina and neighbouring Chile appear as a pericratonic, marginal, liminal environment (Argand). These two mountain chains show certain ressemblances, especially concerning the plio-quaternary deformation that effected both with the development of fault basins filled with thick terri- genus series. A structural analysis has been made in the Andean región of Mendoza and Neuquen which belongs to the Cordillera Principal and the salient features, regarding the substratum’s tectonic with its corresponding com- pression (Paleogene-Miocene) and extensión (Plio-Cuaternario) fault Systems, are put forward. The tectonic exposition is based on a rapid strati- graphical observation. The geological features that associate the Precordillera, Cordillera Frontal and Cordillera Costanera with the substratum of the Cordillera Principal, are pointed out. This paper also deais with certain paleogeographical aspects that are important for the Southamerican continent’s history.

En este trabajo se estudia la sedimentología de la laguna de Chascomús (provincia de Buenos Aires), uno de los tantos cuerpos de agua poco profundos típicos de la planicie aluvial del río Salado. Además de consideraciones hidrológicas, morfológicas y estratigráficas, se describen los aspectos morfológicos, topografía del fondo y propiedades físico-químicas del agua de la laguna. El estudio sedimentológico de muestra de fondo incluye determinaciones químicas (CaCOs, materia orgánica, fosfatos, sulfuros y cloruros, etc.), análisis mecánico, determinación de la composición mineralógica (incluye minerales de las arcillas). De esta manera, los sedimentos de fondo (limos arenosos y limos) son caracterizados y comparados con los sedimentos cuaternarios vecinos. En el último capítulo se analiza la génesis de la laguna. The present paper deals with the sedimentology of the “laguna” of Chascomús tBuenos Aires Province), one of the many shallow bodies of water which are typical of the Salado river flood-plain. After hydrological, morphological and stratigraphical considerations, the “laguna” is described (morphology, botton topography and physics-chemical properties of the water). The sedimentólogical study of the bottom samples includes chemical determinations (CaCO.i, organicic matter, phosphates, sulphides and chlorides, etc.), mechanical analysis and determination of the mineralogical composition, clay minerals included. In the way, the bottom sediments (sandy silts and silts) are characterized and compared with neighbouring Cuaternary sediments. A final chapter in devoted to the genesis of the “laguna”.

The main results of the geological study of folded Pre-pyrenean Eocene (Ripollés Oriental area, Gerona and Barcelona piovinces) are presented in this paper. An interpretative section of the sedimentary basin as well as the age and genesis of the different litliological units are given. It is also discussed the origin of the tectonic structures.

El presente trabajo tiene por finalidad considerar los siguientes puntos: a) El proceso natural de bituminización del carbón. b) La relación entre bitúmenes y propiedades coquizantes del carbón. c) Características bitumínicas del carbón de Río Turbio y perspectivas para su coquización. A los efectos de facilitar el desarrollo del tema, primeramente consideraré algunas generalidades referentes a los carbones desde el punto de vista de su génesis y constitución., In this paper the author explains the now admitted ideas about the formation of bitumens in mineral coal. According with these ideas, there are humic and liptobiolitic bitumens. The humic ones condition principally the coking properties of coal in connection with other physical and petrographical factor s. It is possible to accept that in the Rio Turbio coal both, humic and liptobiolitic bitumens, are present in different proportions. For this reason it would be possible to localize, within such coal basin, partial reserves of mineral with higher coking qualities than those known at the present time., Facultad de Ciencias Naturales y Museo

This paper presents a study of the geology of the alkaline complex of Pocos de Caldas. This massif judging from its area which is in the order of 800 square kilometers, is considered to be one of the greatest complexes formed exclusively by nephelinic rocks. Of an elliptic shape, w ith 35 km in the NESW direction and 30 km in the NW-SE direction it possesses in addition, a stock of foyaite of about 10 square kilom eters. The Parana sedimentary basin forms its western boundary, whilst the foothills of the Serra da Mantiqueira form the eastern boundary The complex is emplaced between granite and gneisses which, in the SE quadrant and to a lesser extend in the NW quadrant were metasomatically affected, mainly along the direction of schistosity, by the process of fenitisation. In the northw estern area the fenite is of a greenish grey colour while in the southeastern area it is red in colour The complex consists mainly of nephelinic rocks: tinguaite and foyaite, containing however, in its interior rocks which are older than the alkaline intrusion. They are sediments and volcanic rocks formed by tuffs, breccias, agglomerates and ankaratritic lavas. The sediments accompany the contact with the gneiss. Their largest outcrops are found in the western and southern portions of the complex. The basal members of the sedimentary sequence consist of sandy shales, with horizontal bedding and the top is formed by sandstone with cross lamination. They are disturbed and usually dip towards the center of the complex. Breccias, tuffs and lavas w Tere deposited over the sediments and form a continuous band along the N-W border The breccias are formed chiefly by fragments of sediments, gneiss, diabase and la v a . The m atrix is rich in detritic well rounded quartz. The action of hydrothermal solutions, during the metasomatic process, is indicated by the appearence of autigenic biotite, microcristals of aegerine and apatite. In the matrix, secondary calcite is very common and often substitutes partially of totally the quartz. The ankaratritic lavas frequently form agglomerates. Products of the volcanic activity are found along the whole internal border, indicating that the volcanic activity covered a large a r e a . A fter this activity phonolites, tinguaites and foyaites were formed, with frequent changes from one type of rock to another. The tinguaites constitue the major area of the complex and reveal great uniformity In some areas, especially in the neighbourhood of Cascata varieties of pseudoleucite and analcite appear The foyaites are intrusive in the tinguaites, but the emplacement occured more or less contemporaneously as is suggested by the change of one type of rock into the other Besides the various types of foyaites, with equigranular and trachitoidal textures, lujaurite and chibinite appear in a small area at the northern part of the massif. The initial stages of the intrusion seem to have been accompanied by the up-rising of blocks of the cristalline basement, which preceded the volcanic activity Either during or after the volcanic activity the subsidence of the central part occured, with the formation of radial and circular faults, which permited the up-rising of the magma. The existence, even at the present level of erosion, of small areas of volcanic material, disturbed by the intrusion, indicates that the subsidence was not total, but that parts of the volcanic cover served as a roof for the emplacement of the tinguaite and the differentiation of foyaite. The great annular dike of tinguaite was emplaced along the periphery, forming a nearly complete ling of varying thickness, with vertical or nearly vertical dips. The deduction of the geometrical form of the tinguaitic in trusion, in the central part of the massif is made difficult by the great mineral and textural homogeneity of the rocks. The subsidence must have started in the center, where it was most pronounced and it must have preceeded the formation of the annular dike. This is proved by the observation of many xenoliths of rocks belonging to the interior of the massif occuring in the ring-dike. The last events of the magmatic action are represented by foyaitic intrusions in the form of smaller dikes cutting the great annular dike. The sequence of the different intrusions seems to be from the centre to the periphery The topography shows two areas with different geomorphological features: the major area, with annular drainage and the smaller with a relief between youth and maturity, in which the radial drainage predominates. It is probable that the drainage system is controlled by the main system of joints. After the activity of the alkaline magma faulting occured over a large area. The main faulting system formed the E-W “graben" which touches the southern border of the complex. The mineral resources consist of bauxite ores, zirconiferous minerals, as zircon, “caldasitev, baddeleyte which have variable content of uranium, and deposits of thorium and rare earths. The minerals with zirconium and thorium were formed by phenomena related to hydrothermal processes, which distroyed the primary minerals and caused precipitations along joints

Los autores han viajado por los Andes (1965) y los Alpes (1966) a fin de tener una idea conjunta de Índole geotectónica que permita brindar los resultados de una comparación reciente sobre la organización y desarrollo de ambas estructuras. Los Alpes se adecúan al régimen ortogeosinclinal clásico por su evolución y magmatismo. Los Andes en la Argentina central y Chile, vecino, aparecen como un marginal ambiente liminar (Argand), pericratónico. Una afinidad es evidente entre ambas cadenas especialmente en lo que concierne a la deformación pliocuaternaria que afectara a las mismas con la formación de cuencas falladas rellenadas con series terrígenas potentes. Son analizados los aspectos estructurales de la región andina de Mendoza y Neuquén correspondiente a la Cordillera Principal y expuestos los caracteres salientes de su tectónica de zócalo con sistemas de fallas en compresión (Paleógeno-Mioceno) y sistemas similares en extensión (Plio-Cuaternario). Una rápida visión de la estratigrafía sirvió de base a la exposición tectónica. Fueron señalados los rasgos geológicos de la Precordillera, Cordillera Frontal y Cordillera Costanera de Chile que se asocian al substratum de la Cordillera Principal. Se analizan en el trabajo paralelamente algunos caracteres paleogeográficos que interesan para la historia del continente sudamericano., The present authors have visited the Andes (19651 and the Alps (1966), in search of the geotectonical data necessary for the comparison of the evolution and development of these structures. Taking into account the evolution and magmatiam, the Alps pertain to the classical orthogeosyncline regime. While the Andes, in central Argentina and neighbouring Chile appear as a pericratonic, marginal, liminal environment (Argand). These two mountain chains show certain ressemblances, especially concerning the plio-quaternary deformation that effected both with the development of fault basins filled with thick terri- genus series. A structural analysis has been made in the Andean región of Mendoza and Neuquen which belongs to the Cordillera Principal and the salient features, regarding the substratum’s tectonic with its corresponding com- pression (Paleogene-Miocene) and extensión (Plio-Cuaternario) fault Systems, are put forward. The tectonic exposition is based on a rapid strati- graphical observation. The geological features that associate the Precordillera, Cordillera Frontal and Cordillera Costanera with the substratum of the Cordillera Principal, are pointed out. This paper also deais with certain paleogeographical aspects that are important for the Southamerican continent’s history., Digitalizado en SEDICI-CIC Digital., Facultad de Ciencias Naturales y Museo (FCNM)

En este trabajo se estudian la composición mineralógica esencial y la fábrica de las sedimentitas psefíticas que integran, en parte, los grupos de La Lola (Silúrico) y Bravard (Eodevónico), y la serie de Sauce Grande (Carbónico superior), en las Sierras Australes de la provincia de Buenos Aires. Estos depósitos son considerados como ortoconglomerados (La Lola y Bravard) y paraconglomerados (Sauce Grande), reconociéndose la naturaleza cuarzosa de los primeros y cuarzo-feldespática de los segundos. La deformación tectónica observada varía en sus características, según la intensidad de la misma y la competencia de las sedimentitas afectadas y ha modificado parcialmente la fábrica sedimentaria, especialmente en los conglomerados de La Lola y Bravard. Como complemento, se analizan la génesis, condiciones ambientales y, en el caso de Sauce Grande, la procedencia del material lítico. Se señala además la posible existencia de una discordancia angular entre el grupo eodevónico de Lolén y la serie de Sauce Grande, y se sugiere la unión de la serie de Piedra Azul con la de Sauce Grande. This paper deais with essential mineralogical composition and fabric of the psephitic rocks which partially make up the La Lola (Siluriana and Bravard (Eodevonian) Groups and the Sauce Grande Series (Upper Carboniferous), all in the Sierra de la Ventana range in Southern Buenos Aires Province. The La Lola and Bravard psephites are shown to be orthoconglo- merates on the basis of their quartzose nature, whilst the Sauce Grande ones, on the main quartz-felspathic, are classified as paraconglomerates. Depending on the intensity of deformation and competence of the sedi- ments, the tectonic deformation has partially altered the original depo- sition fabric and imposed a grain orientation, specially in the La Lola and Bravard conglomerates. The study also ineludes provenance of lithic fragments (Sauce Grande Series), enviromental conditions and génesis of the rocks. The presence of a probable angular unconformity between the Lolén Group (Eodevonian) and Sauce Gande Series is mentioned, and the reunión of the Piedra Azul Series to Sauce Grande is suggested.

Se presentan los lineamientos generales de la estratigrafía del Cenozoico superior pedemontano de un sector de la. Sierras Septentrionales de la Provincia de Buenos Aires. Sobre la "roca de base" (Basamento Cristalino + Grupo Tandil) se disponen las Formaciones Barker, Vela y Las Animas, entidades preferentemente loéssicas con facies fanglomerádicas proximales a los cuerpos serranos. Se describe una unidad de origen fluvial, la Formación Tandileofú, para el valle del arroyo homónimo. Todas estas entidades están separadas por discordancias erosivas observadas regionalmente. Se intenta una caracterización sedimentológica de las unidades litoestratigráficas descriptas, reconociéndose la existencia de dos generaciones de tosca. Los depósitos estudiados representan al Holoceno, la mayor parte del Pleistoceno y quizás el Plioceno superior. This paper deals with the stratigraphy of Upper Caeno- zoic piedmont deposits of the Northern Hills (Sierras Septen- trionales), Buenos Aires Province, Argentina. Three loessic formations and a sandy, fluvial one, have been described over an 1 600 km^ area according to field data and sedimentologica1 studies. Sandy and clayey silts are the most important petrographic types of these units, but gravels and sedimentary breccias were found close to the mountain front. Erosional uncomformities and caliche deposits were regionally recognized. Middle and Upper Pleistocene fossil mammals were found in the younger deposits. The oldest formation is considered to be of Pliocene or Lower Pleistocene age.

ADEGOKE,O. S., 1967.- Wyattella, a new turritellid genus from the Eocene of Colombia, South America, Journal of Pal., v. 41, n. 5, pp. 1095-llOO, 3 fs., 1 lam., Menasha. / BUCHWALD,V. F., WASSON, J. T., 1968.- The two Colombian iron meteorites Santa Rosa and Tocavita, Analecta Geologica, n, 3, pp. 29, 20 ls., Mineralogisk Museum, Københaun. / BUENO, S. R., 1965. (Ap. 1968). - Ocurrencia y litología del "Toro Shale", Boletín de Geología, n, 21, pp. 33.41, 5 fs., Bucaramanga. / BUTTERLIN, J., 1966. Macroforaminifères de I'Eocène de Colombie, Bull. Soc. Géol. de France, s. 7, t. 8, pp. 627.629, 1 fig., 1 lám., Paris. / BUTTERLIN,J., 1968.- Asterocyclina cruzi, espèce nouvelle de l'Eocène moyen de Colombie, Eclogae Ceol. Helv., v, 61, n, 1, pp. 225.228, 3 ls., Bale. / CEDIEL,M. F., 1968. - El Grupo Girón, una Molasa Mesozoica de la Cordillera Oriental, Boletín Geológico, vol. 16, ns. 1- 3, pp. 5 - 96, 18 fs., 2 ls., Bogota. / CUCALÓN, H., 1967. - Litología y Tectónica de un área en el borde este del cañón del rio Chicamocha (Boyaca ) ; Revue Photo-Interpretation; n. 5, fasc, 1; pp. 1 - 7, 2 fotos, París. / DUQUE,H., 1967. (Ap. 1968). - Observaciones generales a la Bioestratigrafía y geología regional en los Departamentos de Bolívar y Córdoba, Bol. Geol., Univ. Ind. Santander. n, 24, pp. 71- 87, 3 fs., Bucaramanga. / ETAYO· SERNA, F., 1965. (Ap. 1968). Sinopsis estratigráfica de la región de Villa de Leiva y zonas próximas, Boletín de Geología, n. 21, pp. 19.32, 4 fs., 1 mapa, Bucaramanga. / ETAYO • SERNA, F., 1968.- Apuntaciones acerca de algunas amonitas interesantes del Hauteriviano y del Barremiano de la región de Villa de Leiva (Boyacá, Colombia, S. A.), Boletín de Geología, n, 24, pp. 51- 70, 4 fs., 7 ls., Bucaramanga. / GEYER,O. F., 1967. - Das Tipus - Profil der Morrocoyal Formation (Unterlias; Dpto. Bolivar, Kolumbien) , Mitt. Inst. Colombo-Alemán Invest. Cient., n, 1, pp. 53.63, 3 fs., Santa Marta. / GEYER,O. F., 1968. - Nota sobre la posición estratigráfica de la fauna de cor ales del Jurásico superior de la península de la Guajira (Colombia), Boletín de Geología, n, 24, pp. 9 - 22, 4 fs., 2 ls., Bucaramanga. / GEYER,O. F., 1968. - Über den Jura der Halbinsel la Guajira (Kolumbien), Mitt. Inst, Colombo- Aleman Invest. Cient.; n, 2, pp. 67-83, 2 fs., Santa Marta. / GONZÄLEZ GUZMAN, A. E., 1967. - A palinological study of the Upper Los Cuervos and Mirador Formations (Lower and Middle Eocene; Tibú Area, Colombia), pp. 68, 10 fs., 30 ls., Leiden. / GREEN,D. H., LOCKWOOD, J. P., and KISS, E., 1968. - Eclogite and Almandine-Jadeite-Quartz rock from the Guajira Península, Colombia, South América. Amer. Mineralogist, Vol. 53, pp. 1320.1355, 4 figs., 2 tabls. / FEININGER,T., Y GOMEZ,M. B., 1968. - La Caverna del Nus, Departamento de Antioquia, Boletín Geologico, vol. 16, ns. 1- 3, pp. 97- 111, 7 fs., Bogotá. / FEYS, R., GEFFROY,J., VETTER,P., 1967. - Un cas nouveau de graphitisation du charbon par une intrusion éruptive à Cali (Colombie). (Observation de M. Lambrecht), Annales de la Societe Geologique du Nord, t. 87, n, 3, pp. 145 - 150, 4 fs., láms. XI - XV, Lille. / FORERO,A., 1967.- Notas preliminares sobre la estratigrafía del Paleozoico en el Norte de los Andes de Colombia, Mitt. Inst, Colombo - Aleman Invest. Cient., n. 1, pp. 31- 37, 1 fig., Santa Marta. / HOFFSTETTER,R., 1967. - Remarques sur les dates d'implantation des différents groupes de Serpents terrestres en Amérique du Sud, Compte Rendu Som, Séances Société Géol. de France, fasc. 3, pp. 93 - 94, Paris. / HOFFSTETTER, R., 1967. - Observations additionelles sur les Serpents du Miocène de Colombie et rectification concernant la date d'arrivée des Colubridés en Amérique du Sud, Compte Rendu Som. Séances Société Géol. de France, fasc. 5, pp. 209 - 210, Paris. / JULIVERT,M., 1968. - La obra de Hans Bürgl en Colombia, Boletín de Geología, n. 24, pp. 5 - 8, Bucaramanga. / LATARCHE, CH. H. y OSPINA, I., 1967. - Manera de interpretar un valle. Datación relativa de las terrazas; Revue Photo Interprétation, n, 5, pp. 8-14. / PORTA, J. DE, 1966. (Ap, 1968). - La Geología del Extremo S. del Valle Medio del Magdalena, Bol. de Geol., Univ. Ind. de Sant., ns. 22-23, 347 pp., 37 fs., 48 fotos, 23 tbls., 4 mapas, Bucaramanga. / RADELLI, L., 1967. - Géologie des Andes Colombiennes, Trauaux du Laboratoire de Géologie de la Faculté des Sciences de Grenoble, n. 6, pp. 457+ 13, 162 fs., Grenoble. / RICHARDS,H. G., 1968. - Cretaceous Section in Barco area of northeastern Colombia, Bull. Am. Assoc. Petro Geol., V. 52, n. 12, pp. 2, 324 - 336, 4 figs. Tulsa. / SHEPARD, F. P., DILL, R. F. y HEEZEN, B. C., 1968. -Diapiric Intrusions in Foreset Slope Sediments of Magdalena Delta, Colombia. Bull. Amer. Assoc. Petrol. Geol., V. 52, n. II, pp. 2197 - 2207, 10 figs., Tulsa. / SCHRAM, F. R., 1968. - Paleosquilla Gen. Nov., A Stomatopod (Crustacea) from the Cretaceous of Colombia, Journal of Pal., v. 42, n. 5, pp. 1297 - 1301, 2 fs., Menasha. / STIBANE, F. R., 1966. Paläogeographie und Tectogenese der Kolumbianischen Anden, Geol. Rdsch, v. 56, pp. 629 - 642, 5 fs., Stuttgart. / STIBANE, F. R., 1966. - Orogenese und Epirogenese in den Anden Kolumhiens, Südamerika, Natur u. Museum, v. 96, n, 2, pp. 69 - 73, 2 fs., Frankfurt. / STIBANE, F., 1967. - Conodonten des Karbons aus den nördlichen Anden Südamerikas, N. Jb. Geol. Paläont. Abh., v. 128, n, 3, pp. 329 - 340, ls. 35 - 37, 1 fig., Stuttgart. / STIBANE, F. R., 1967. - Devonian of the Cordillera of Colombia, Internat.Symposium on the Devonian System, pp. 209 - 213, l fig., Calgary. / STOUGH, J. B., 1968. - Palynomorphs from South America, Part. 4, Palynomorphs from the Zipaquirá Salt, Colombia. The University of Kansas Paleontological Contributions, paper 32, pp. 11-12, Lawrence.

[ES]Se describen detalladamente en este trabajo los escarpes paleógenos que se encuentran al norte del río Tormes, entre Salamanca y Babilafuente, estableciéndose tres unidades estratigráficas netamente diferentes que hemos llamado "areniscas de Salamanca", "de Cabrerizos", y "de Aldearrubia" y que corresponden al Pre-Luteciense, Luteciense y Ludiense respectivamente. Un intento de correlación secuencial ha dado resultados positivos en las dos primeras. Sus constituyentes minerales y los fósiles encontrados muestran que el clima durante el Eoceno fue húmedo, tropical, con tendencia paulatina hacia la aridez. El conjunto ha sido afectado por la orogenia alpina, que ha producido una tectónica de fracturas., [EN]Are described in detail in this paper the Paleogene escarpments that lie north of the river Tormes, between Salamanca and Babilafuente, establishing three distinctly different stratigraphic units we have called "Salamanca sandstone," of Cabrerizos ", and" Aldearrubia "and correspond to pre-Lutetian, Lutetian and Ludiense respectively. An attempt to correlate sequence has yielded positive results in the first two. Its constituent minerals and fossils found show that the Eocene climate was humid, tropical, with a gradual trend towards aridity. The group has been affected by the Alpine Orogeny, which produced a tectonic fractures.

The present paper deals with some petrographical observations on a lamprophyre taht occurs in the vicinity of outerops of acid volcanic rocks – Cerro Tupanci. The geographical setting is to the north of Arroio São Sepé Quadrangue. With the exception of texture detaisl the rock is composed fundamentally by hornblende and plagioclase within a mesostasis of plagioclase, hornblende, quartz a apatite. The secondary formation of chlorite, carbonate, sphene, epidote and opaque minerals was observe., Neste trabalho são descritos alguns aspectos petrográficos de lamprófiros das proximidades de afloramente de rochas vulcânicas ácidas – Cêrro Tupanci. A ocorrência localiza-se no norte da Quadrícula Arroio São Sepé. Afora detalhes texturais a rocha é constituída fundamentalmente por fenocristais de hornblenda e plagioclásio numa mesóstase de plagioclásio, hornblenda, quartzo e apatita. Observou-se a formação secundária de clorita, carbonato, esfeno, epidoto e minerais opacos.