Armenteros, I. (1989): Alteración del sustrato y encostramientos carbonáticos ligados a la discontinuidad Cretácico-Terciaria en el borde Este del Sistema Ibérico. Stvdia Geologica Salmanticensia,Vol.Espec. 5 (Paleogeografía de la Meseta Norte durante el Terciario) (C.J.Dabrio, Ed.): 3-54.
ABSTRACT: The top of the terminal Cretaceous (? Paleocene) regressive deposits of the Iberian Range (boundary with the Almazán Basin) a sedimentary discontinuity marked by incipient karstification and, mostly, by alteration of the carbonate subtratum and generation of complex layers of edaphic caliches is described. Weathering was promoted by meteoric waters near the discontinuity and resulted in several processes: dedolomitization, micritization and organic activity around roots. Milimetric to decimetric sized cavities filled up with crusts (speleothems), detrital carbonate sediments and terra rosa witness karstification. Isolate or alternating massive (croûte en dalle, massive hardpan) and laminated (croûte zonaire, laminar hardpan) caliches are found both on top and inside the substratum. Four microtructures can be recognized: {a) crumbly, {b) intergrain aggregate, (c} single grain structure, (d) vertical or horizontally laminated, which can form gradual transition ot the type a --> b --> c. Locally also crumbly fenestral microstructures are found. Distinguishing features of these edaphic caliches include the abundance of pedorelicts, ooids. peloids, ubiquitous in situ Microcodiun and root tubules with associated calcite meedles and alveolar texture. Vadose diagenesis is inferred from a variety of features such as porosity in flat voids due to deliccation, gravitational and meniscus cementation with a complex succession of encrustig phases. During the time span corresponding to the development of the discontinuity a warm climate with progressive reduction of rain is assumed from the various features observed and the substitution of karstic by caliche forming processes.
Olmo Sanz, A. del & Martínez-Salanova Sánchez, J. (1989): El tránsito Cretácico-Terciario en la Sierra de Guadarrama y áreas próximas de las Cuencas del Duero y Tajo. Stvdia Geologica Salmanticensia,Vol.Espec. 5 (Paleogeografía de la Meseta Norte durante el Terciario) (C.J.Dabrio, Ed.): 55-69.
ABSTRACT: Two depositional sequences (Mitchum et al., 1977) separated by a prominent unconformity are decribed in the detritic sediment placed between the Late Cretaceous and Miocene deposits in both sides of the Guadarrama Range (Central Spain). The mostly siliciclastic, lower sequence considered ot Cretaceous age (contrarily to the Paleogene age dominantly invoked by previous authors) was deposited in fan delta settings. The upper, polymictic, sequence is of Paleogene age and correponds to alluvial fan deposits.
Montes Santiago, M.J., Alonso Gavilán, G. & Dabrio, C.J. (1989): Estratigrafía y Paleogeografía del Cretácico terminal-Paleógeno del borde suroeste de la Cuenca de Villarcayo (Burgos). Stvdia Geologica Salmanticensia,Vol.Espec. 5 (Paleogeografía de la Meseta Norte durante el Terciario) (C.J.Dabrio, Ed.): 71-87.
ABSTRACT: Two informal lithostratigraphic units have been distinguished in the Late Cretaceous to Paleogene deposits of southwestern Villarcayo Basin (Burgos province, Northern Spain). The LOWER UNIT includes four subunits made up of carbonate (limestone and dolostone) rocks with marine fossils, lagoonal mudstones, sandstones with herringbone cross stratification, etc, which were deposited in shallow marine to transition realms which alternate vertically in response to sea level oscillations. The UPPER UNIT comprises two terrestrial (lacustrine and fluviatile) subunits genetically related to tectonic movements along the margins of the basin, which produced shifting of depocenters, and a seasonal climate that induced notable changes of water level of lakes. The main controls of sedimentation recognized are: (1) oscillations of sea level; (2) the upward~movement of the Rosio diapir placed to the north; (3) folding of the substratum of the basin and generation of the Sierra de 1a Tesla anticline and (4) the general uplifting of the region which eventually induced the retreat of marine environments and the passage to terrestrial realms.
Corrochano, A. (1989): Facies del Cretácico terminal y arquitectura secuencial de los abanicos aluviales terciarios del borde Norte de la Depresión del Duero (Valle de las Arrimadas, León). Stvdia Geologica Salmanticensia,Vol.Espec. 5 (Paleogeografía de la Meseta Norte durante el Terciario) (C.J.Dabrio, Ed.): 89-106.
ABSTRACT: In the northern margin of the Duero Basin the Tertiary sediments are separated from those of the Cretaceous cycle by a stratigraphic unconformity. The topmost part of the Cretaceous sediments is interpreted in this paper as a shallowing upwards sequence including facies deposited in open shelf, lagoon and inner tidal flats with oolitic shoals. Three formations bounded by unconformities have been identified in the Tertiary: Barrillos Formation, Vegaquemada Formation and Candanedo Formation, each representing alluvial fan systems with clearly identified geometry and spacial place. The first is filling the paleotopography created by the first relief forming tectonic movements. The others are also alluvial fans placed one in the eastern side (Vegaquemada) and the other (Candanedo) overlaping the former in the western side. They represent the maximum diastropbism of the basin margin. Progradation of alluvial fans resulted in an architectural sequence of the different hierarchies. The more basic are related wich autocyclic processes whereas the thicker ones with alocyclic processes.
Armenteros, I., Dabrio, C.J., Guisado, R. & Sánchez de Vega, A. (1989): Megasecuencias sedimentarias del Terciario del borde oriental de la Cuenca de Almazán (Soria-Zaragoza). Stvdia Geologica Salmanticensia,Vol.Espec. 5 (Paleogeografía de la Meseta Norte durante el Terciario) (C.J.Dabrio, Ed.): 107-127.
ABSTRACT: Lithostratigraphic and sedimentological studies of Tertiary sediments filling the Almazán Basin along the sierra front of the Iberian Range led to distinguish 19 lithostratigraphic units included into 5 Tectonosedimentary Units (TSU). Facies associations along the stratigraphic succesion correspond to alluvial and lacustrine sedimentary environments that evolved in space and time in response to the changing distrophism of the margin of the basin. Several main facts are deduced: (a): there is a major sedimentary discontinuity that lasted since (approximately) the limit Cretaceous-Tertiary until Middle-Upper Eocene when sedimentation of TSU 1 began. (b) TSUs 2 and 3 are separated by a large discontinuity punctuated by reactivation of the alluvial systems along the sierra front. It is correlated to the Intra-Oligocene Castillian tectonic phase. (c) TSUs 4 and 5 are separated by another major discontinuity correlated to the Neocastillian (post Upper Agenien) tectonic phase.
Jiménez Fuentes, E., Cuesta, M.A., Martín de Jesús, S., Mulas, E., Pérez Ramos, E. & Jiménez García, S. (1989): Primera nota sobre los vertebrados del Eoceno superior de Mazaterón y Deza (Soria). Stvdia Geologica Salmanticensia, Vol.Espec. 5 (Paleogeografía de la Meseta Norte durante el Terciario) (C.J.Dabrio, Ed.): 129-133.
ABSTRACT: The gisements of Mazaterón and Deza (Soria Province, Spain) supplied a rich fauna of fossil Perissodactyla (Palaeotheridae), Artiodactyla, Carnivora, Chelonia (Testudinidae. Pelomedusidae, Tryonichidae), Crocodylia (Sebecidae, Alligatoridae), lacertids and fishes. All this fauna suggests an Upper Eocene age.
Peláez-Campomanes, P., Peña, A. de la & López Martínez, N. (1989): Primeras faunas de micromamíferos del Paleógeno de la Cuenca del Duero. Stvdia Geologica Salmanticensia,Vol.Espec. 5 (Paleogeografía de la Meseta Norte durante el Terciario) (C.J.Dabrio, Ed.): 135-157.
ABSTRACT: Five gisements of Eocene micromammals of Duero Basin in the Zamora (Jambrina, Santa Clara, Babilafuente and Sanzoles) and Almazán (Miñana) areas are studied. The association of micromammals found can be placed in the Chronologic scale for the European Paleogene (as stablished by SCHMIDT KITTLER, 1987) and, as a consequence, the deposits they occur in have bheen dated with certain accuracy. The deduced ages are: Zamora: Neustrian Rhenanian; Santa Clara: Middle Rhenanian (Middle Eocene); Salamanca: Upper Rhenanian (Uppermost Middle Eocene), and Almazán: Upper Eocene. The similitude of some faunistic elements found in Zamora with asiatic faunas are thought to be of biogeographical importance as far as the relationships between Europe and Asia during the Eocene times are concerned.
Alonso Gavilán, G., Dabrio, C.J., Mediavilla, R.M. & Armenteros, I. (1989): Procesos sedimentarios y desarrollo de sand flats en ríos arenosos del Eoceno del Suroeste de la depresión del Duero. Stvdia Geologica Salmanticensia,Vol.Espec. 5 (Paleogeografía de la Meseta Norte durante el Terciario) (C.J.Dabrio, Ed.): 159-176.
ABSTRACT: The Cabrerizos Sandstone Formation (Middle Upper Eocene) was deposited by braided f1uvial systems with broad, shallow channels (high values of the width/depth ratios, flowing towards the NE, N and NW after draining metamorphic and granitic source areas. Sedimentation occurred under autocyclic (the early hardening of the surficial sediments due to processes of calcrete formation, and the existence of obstacles in the course of the channels) and allocyclic (the seasonality of a semi arid climate although the water courses lasted over the whole year) factors. Channels were able to erode the substratum but, as far as it was resistent, most of the erosion concentrated along the margins. In some moments of the history of the channels sand flats developed which underwent partial subaerial exposure during low water satges.
Molina, E., Vicente, A, Cantano, M. & Martín Serrano, A. (1989): Importancia e implicaciones de las paleoalteraciones y de los sedimentos siderolíticos del paso Mesozoico-Terciario en el borde Suroeste de la Cuenca del Duero y Macizo Hercínico Ibérico. 177-186.
ABSTRACT: In the contact of the Iberian Hercynian Massif with the Tertiary or Mesozoic coverings it is common to find the remnants of old weathering mantles. In the southwestern border of the Duero basin these alterites appear fossilized by Tertiary series of different ages. The oldest one, having a siderolithic nature, has been lately attributed to a Paleocene age. After the sedimentation of the siderolithic serie, the Alpine movements fractured and tilted the blocks of the Hercynian Massif. In one of the bordering grabens several weathering profiles have been studied. They are fossilized by sediments of different ages, probably various Tertiary alterites, but usually lay on top of an older Mesozoic correlative to the siderolitic sediments. A weathering sequence with Ioss and ganance of elements both in the sediment and the socle has been established. A critical analysis of several aspects of the siderolitic deposits, for example their association to Cretaceous deposits of the Central System, leads to assume that they have a very important role in the Iberian Massif during the Mesozoic Tertiary transition. Moreover, this implies that the siderolitic is outside the sedimentary basin sensu stricto and it is considered as a polichronic deposit linked to the Mesozoic.
Alonso Gavilán, G., Blanco Sánchez, J.A. & Sánchez Macías, S. (1989): Alteraciones asociadas a los paleosuelos de las areniscas de Villamayor (Salamanca). Stvdia Geologica Salmanticensia, Vol.Espec. 5 (Paleogeografía de la Meseta Norte durante el Terciario) (C.J.Dabrio, Ed.): 187-207.
ABSTRACT: The Villamayor Sandstones consits of fining upwards sequences which, in turn, form a coarsening upwards megasequence. Scdimentological arguments point out to a genesis related to a sandy braided fluvial system with cyclic variations of flow velocity, avulssions and infilling of abandoned channels with development of paleosoils between different stages (grained terms). The pattern of paleocurrents and heavy minerals indicate drainage of low range metamorphic and granitic source area placed toards the SE which produced arkosic sediments. Each lithologic sequence shows an alteration profile confined by: (a) crusting processes at the top of the sequence (with grouped and scattered nodules and diffuse cruting); (b) reorientaton of clay plasma accompanied by clay neoformations and (c) biological activity (burroging). The profile is characterized, from bottom to top, by: 1º. decrease of the percentage of feldspar; 2º.- accumulation of dolomite as crust replacing arkosic sediment and 3º. increase of palygorskite, with a maximum matching the one of dolomite. All these feature indicate that the genesis of the weathering profile probably related to oscillations of phreatic water table through the coarse sediments filling the narrowly spaced active channels which produced transformations due to water circulation and, independently, pedogenic plocesses related to a climatic seasonality.
Blanco, J.A., Alonso Gavilán, G., Fernández Macarro, B. & Sánchez Macías, S. (1989): Alteración roja miocena sobre las areniscas de Villamayor. Stvdia Geologica Salmanticensia, Vol.Espec. 5 (Paleogeografía de la Meseta Norte durante el Terciario) (C.J.Dabrio, Ed.): 209-222.
ABSTRACT: The arkosic Villamayor Sandstone was deposited by a sandy braided fluvial system which drained a low range metamorphic and grantic source area in a semiarid climate. After deposition, and before the deposition of the Teso de la Flecha Conglomerates, a stage of no sedimentation is assumed with development of an edaphic profile characterized by: (a) generalized neoformation of palygorskite after arkosic sediments, (b) strong calcitic epigenesis at the top, (c) separation between calcium, in carbonate phase, ad magnesium, in silica phase, and (d) rubefaction of the profile. These features indicate that the edaphic profile developed of a poorly drained, stabilized surface, but with strong weathering reactions. All this points out to a mediterranean climate with dry and wet alternating seasons.
Blanco, J.A., Cantano, M., Armenteros, I., Fernández Macarro, B. & Sánchez Macías, S. (1989): Superposición de procesos de alteración en la serie roja miocena de la Fosa de Ciudad Rodrigo. Stvdia Geologica Salmanticensia, Vol.Espec. 5 (Paleogeografía de la Meseta Norte durante el Terciario) (C.J.Dabrio, Ed.): 223-238.
ABSTRACT: The red Miocene Series of the Ciudad Rodrigo basin exhibits an emsemble of massive structure made up of red lutite sands at the base of the series that become coarser towards the top. The sedimentological characteristics point to sedimentation in the medial distal parts of an alluvial fan ssstem. During periods of sedimentary interruption processes of alteration associated with colonization by soils took place. These resulted in the neoformation of palygorskite on the top of each sequence, accompanied by nodules or small discontinuous carbonate crusts. In places where the red series overlies the hercynian basement, it fossilizes a small alteration profile also characterized by the presence of palygorskite on the top. In the Ciudad Rodrigo basin, unlike in the surroundings of Salamanca where it was defined, the red Series was not covered by younger deposits and hence underwent processes of climatic alteration towards the end of the Neogene that led to both mineralogical and textural changes. A decreasing kaolinization occurred that affected the whole series an the underlying basement, although to a lesser extent. The massive destabilization of the pre existing palygorskite under the new climatic conditions favoured the progressive kaolinization in these impermeable lutitic sediments.
Martín Serrano, A. (1989): Características, rango, significado y correlación de las series ocres del borde occidental de la Cuenca del Duero. Stvdia Geologica Salmanticensia, Vol.Espec. 5 (Paleogeografía de la Meseta Norte durante el Terciario) (C.J.Dabrio, Ed.): 239-252.
ABSTRACT: All Appalachicn basin in the northwestern border of the Duero Meseta were finally filled up with similar materials which in the Tera Valley, the largest basin. are commonly referred to as "Series Ocres" (Ochre Series). Detailed study of the sedimentological and stratigraphic features of the Series Ocres permitted to establish their defining characteristics but, due to their homogeneous aspect, a careful research on the petrology and mineralogy of these materials was necessary to correlate them with the "alterites" developed into the socle of the surrounding areas. The "Series Ocres" integrate a well defined lithostratigraphic formation, but its morpho-climatic meaning can be extended to include even the oldest stages of the actual "fluvial network". It also enlights how this formation laterally changes into the Upper Miocene "Tierra de Campos facies" but, at the same time, it is also correlated with the upper lacustrine unit, the widespread presence of "Series Ocres" like materials in the Tertiary piedmonts of the Hesperian Massif strongly remarks its morpho climatic character.
Pena dos Reis, R.P.B. & Proença Cunha, P.M.R.R. (1989): Comparación de los rellenos terciarios en dos regiones del borde occidental del Macizo Hespérico (Portugal central). Stvdia Geologica Salmanticensia, Vol.Espec. 5 (Paleogeografía de la Meseta Norte durante el Terciario) (C.J.Dabrio, Ed.): 253-272.
ABSTRACT: The analysis of the sedimentary succesion in two regions belonging to two big Tertiary basins (North and South of the Central Portuguese Range), led to the definition of several infill episodes. From the comparison of the episodes the chronic of the regional evolution of Central Portugal during Tertiary time was deduced.
Mediavilla, R.M. & Dabrio C.J. (1989): Las calizas del Páramo en el Sur de la provincia de Palencia. Stvdia Geologica Salmanticensia, Vol.Espec. 5 (Paleogeografía de la Meseta Norte durante el Terciario) (C.J.Dabrio, Ed.): 273-291.
ABSTRACT: Towards the top of the Neogene succession in Central Sector of the Duero Basin there are fluvial and paludal deposits (Unit 4) with a facies pattern strongly controlled by a juxtaposition of tectonics and paleomorphology of the lacustrine basin where the underlying deposits (Unit 3) formed. From these data a revision of the stratigraphy of the topmost Neogene and the use of the term "Páramo limestone" is proposed. There exist two limestone layers that can be identified as "Páramo limestone" separated by an unconformity and, locally, fluviatile coarse deposits. The lower layer (top of Unit 3) is the one originally named "Páramo limestone" by HERNÁNDEZ PACHECO (1915), it is not homogeneous (laterally it merges into marlstones) and it does not represent the end of the Neogene sedimentation. The upper layer (top of Unit 4) is related to the top ot the fluviatile dcposits. The uppermost Neogene rocks have been affected by diagenetic processes (incrustation, karstification) related to a polygenic erosional surface which resulted in an homogenization of the originally different lithologies and textures. Consequently it is very easy to miss both members (and even some older layers interlayered into the marly Unit) naming all them in the same way. We propose that the term "Páramo limestone" be used only to refer to the materials culminating Unit 3 which are overlaid by the detritic carbonate deposits of Unit 4.
Mediavilla, R.M. & Dabrio C.J. (1989): Análisis sedimentológico de los conglomerados de Tariego (Unidad 4, Neógeno de la Depresión del Duero). Stvdia Geologica Salmanticensia, Vol.Espec. 5 (Paleogeografía de la Meseta Norte durante el Terciario) (C.J.Dabrio, Ed.): 293-310.
ABSTRACT: The Tariego conglomerates record several mechanisms of deposition of gravel in fluvial channels. srom detailed studies of geometries, lateral and vertical facies relationships and primary sedimentary structures three members were differentiated. The lower Gt dominated member represents a channel filled up with gravel moved by megaripples. Two depositional episodes are distinguished in he intermediate member (the one studied in detail in this paper): the lower one made up of Gp/Sp facies records downcurrent migration of gravelly bars in a low sinuosity ("straight") channel; the upper episode, with large scale epsilon cross stratification (lateral accretion~ and fills of Gp and Sp, is interpreted as point bar deposits of a low sinuosity fluvial system. The uppermost member was deposited by a single point bar of a meandering river.
Sánchez Benavides, F.J., Dabrio, C.J. & Civis, J. (1989): Interpretación paleoecológica de los depósitos lacustres neógenos de Castrillo del Val (Noroeste de la Depresión del Duero). Stvdia Geologica Salmanticensia, Vol.Espec. 5 (Paleogeografía de la Meseta Norte durante el Terciario) (C.J.Dabrio, Ed.): 311-331.
ABSTRACT: Three lithostratigraphic units can be differentiated in the Neogene rocks of the northeastern Duero Basin. The upper unit include marly and silty calcareous sediments deposited in marginal lacustrine and deltaic environments. The study of the fossil fauna, in close relationship with the sedimentary facies they occur in, allows the interpretation of the environmental condition during deposition and the succesive changes of water salinity as due to the repeated influxs of fresh water from a deltaic distributary located nearby. In this context the palaeoecology of the association is~ deduced and a local scale of paleosalinities based on the relative percentage of the various taxa can be elaborated.