Dmitrenko, O.B. (1996): Some features of Nannoflora development in the Cenozoic Atlantic and Indian Oceans. Stvd.Geol.Salmant., 32: p. 3 14.

Key words: Paleogene, Neogene, Quaternary, Calcareous nannoplankton variations, Paleoceanography.

ABSTRACT: Specific and generic compositions of Cenozoic Calcerous Nannoplankton from bottom sediments of the Atlantic and Indian oceans are analyzed, based on deep waters drilling data. Eleven stages in the development of the Nannoflora are recognized, based on changes in generic composition through time. Rates of evolution in the Paleogene, Neogene and Quaternary periods were counted. It was found that rates of evolution of Calcareous Nannoplankton varied: the intervals between 60 45 and 20 4 million years ago (m.a) were characterized by accelerated evolution, indicating favorable conditions for the development of nannoplankton. The marked worsening of conditions, retarded rates of evolution and reduced tempo of evolution were 65 and 40 15 m.a. The most abrupt changes in species and genus composition occurred 65 and 1,8 m.a. and less pronounced changes occurred 18 17, 15 14 and 5 4 m.a.

Fuentes Vidarte, C. & Meijide Calvo, M. (1996): Restos de Pterosaurios en el "Weald" de Soria (Espa±a). Stvd.Geol.Salmant., 32: 15 22.

Key words: Pterosaurs, Weald, Soria (Spain).

[Skeletal remains of Pterosaurs in "Weald" in Soria (Spain)].

ABSTRACT: We make an appointment, in first time, about skeletal remains of Pterosaurs in Weald in Soria province (Spain). We attibute them Titonico Berriasiense age.

Andrés Sánchez, M. F. (1996): Elaboración de funciones. Objetivo y restricciones para la optimización de explotaciones de agua subterránea en régimen permanente mediante técnicas de programación lineal. Stvd.Geol.Salmant., 32: 23 38.

Key words: Groundwater, Management, Optimization, Linear programming, Objetive functions, Constraints.

[Elaboration of objetive functions and constraints for the optimization of groundwater steady flow exploitation through linear programming techniques].

ABSTRACT: The optimization of exploitations of groundwater treated with linear programming methods requires joint evaluation of the data on pumping and variation of potentials, in order to draw conclusions on the values of the one with respect to the other, hence it is necessary that they appear as variables in the objective function. For this reason the simple approaches of maximization or minimization of hidraulics potentials or extractions must be transformed into functions suitable for treatement by linnear programming. The object of this paper is to demonstrate the elaboration of some of these objective functions, as well as of the restrictions arising from the flow equation treated by finite differences, and of those related to the surrounding conditions and other auxiliary restrictions, for the optimization of exploitations of groundwater, using diverse exemples developed on generic hydrogeological typologies. The problems of optimizations contemplated are of two types: the maintaining of the sum of the hydraulics potentials at the maximum possible or, what amounts to the same thing, the maintaining of the decreases at the minimum possible, for given extractions from the acuifer and the obtaining of maximum extractions for limited decreases. In both cases the result is the assignement of the pumping points and extraction volumes of each well whit these requirements. The different cases have been dealt whit for a water table aquifer or a confined aquifer, steady state unidimensional flow and for different environmental conditions, by discretization of the aquifer type in cells and treating of the flow equation by finite differences whit centered block criterion.

Cuesta Ruiz Colmenares, M.A. (1996): Primeros hallazgos de Lophiodontidae (Perissodactyla, Mammalia) en el yacimiento eocénico de Mazaterón (Cuenca del Duero, España): Implicaciones bioestratigráficas. Stvd.Geol.Salmant., 32: 31 49.

Key words: Lophiodon, Lophiodontidae, Perissodactyla, Eocene, Duero basin, Castilla y León, Spain.

[First findings of Lophiodontidae (Perissodactyla, Mammalia) in the eocenic bed of Mazaterón (Duero basin, Spain): Biostratigraphic consequences]. ABSTRACT: In this paper it is described a fragment of maxillary with D2/, wich belonged to a Lophiodontidae (Mammalia, Perissodactyla) from the Mazaterón bed (Eocene, the Duero Basin, province of Soria, Castilla y Le_n, España). This finding only permits its classification as a Lophiodon sp. from the named Giant species. The presence of Lophiodontidae in association with the rest of Perissodactyla allow us to determine the biostratigraphic position of this bed, wich correspond to the upper Rhenanian (MP 16 15).

Gutiérrez Maroto, A; Navarrete, J.; García Giménez, R. & Jiménez Ballesta, R.(1996): Contaminación potencial de suelos por la dispersión secundaria de las escombreras de una antigua mina en el zócalo de la rama occidental de la Cordillera Ibérica (Bubierca Zaragoza). Stvd.Geol.Salmant., 32: p. 49 61.

Key words: Heavy metals, Mining area, Soils, Iberian System.

[Potencial pollution of the soil by secondary dispersion from the rubble dumps of one old mine on the basement of the western branch of the Iberian Massif (Bubierca Zaragoza. Spain)].

ABSTRACT: There are many abandoned mines, rubble dump, test pits, etc., in the Iberian System that behave as true sources of dispersion and potential sources of pollution.To check this hypothesis, the contens in different heavy metals were investigated, taking the La Pedraza Mine (Bubierca Zaragoza) as the primary effluent source. The analysis included 45 samples from surface soil horizons, some of them corresponding to true alluvions. The elements determined were Cu, Pb and Zn, which are elements present in the paragenesis of the mineralization; Cd, with concentrations below 2 ppm in all the soils, and Ba, Cr, Co and Ni. Cupper was found reach background values between 26 and 36 ppm; Zn between 36 and 60 and Pb between 24 and 32 ppm. From these background they show populations of up to 20% for Cu and Zn and 10% for Pb with positive anomalies in de soils.

Gutiérrez Alonso, G. (1995): La estructura del antiforme del Narcea y su relación con los Mantos Occidentales de la zona Cantábrica. Parte I: El Sector Occidental. Stvd.Geol.Salmant., 32: 63 128.

e-mail Gabriel Gutiérrez-Alonso

Key words: Variscan Belt, Iberian Massif, Narcea Antiform, shear zones, foliation, mylonites, phyllonites, quarzt petrofabrics.

[The Narcea Antiform Structure and its relation to the western Cantabrian Zone thrust sheets. Part I: The Western Sector.].

ABSTRACT: At the studied area, in the Variscan Belt of NW Spain, the limit between the Cantabrian Zone (CZ) and the West Asturian Leonese Zones (WALZ) outcrops; it is constituted by precambrian rocks and is known as the Narcea Antiform. In this antiform, two sectors are distinguished due to diferences in rock deformation record at each sector. The western sector of the Narcea Antiform is characterized by the superposition of structures, among which the presence of ductile shear zones is remarkable. These ductile shear zones cleaves a previous foliation, generating several different microestructures as crenulation, crenulation cleavage, and mylonitic or phyllonitic foliations, usualy acompained by mineral lineation. The limit between these western and the eastern units is a major thrust.

Ruiz Muñoz, F.; Clauss Klamp, F.L. & González Regalado Montero, Mª. L. (1996): Primeras consideraciones sobre los Condrichtios de la Formación "Arenas de Huelva". Stvd.Geol.Salmant., 32: p. 129 139.

Key words: Selachians, Batoids, Taxonomy, Palaeoecology, Pliocene, SW Guadalquivir Basin..

[First considerations about the Condrychthyes of the "Huelva sandstones Formation"].

ABSTRACT: A rich fauna of selachians and batoids is recorded from the glauconitic level of the section type of the "Sands of Huelva" Formation. Sixteen types were recognized in the unit studied, which indicate both a temperate climate and a moderate depth (50 to 150 m) during the Lower Pliocene in this sector of the Guadalquivir Basin.