NÚMERO EXTRAORDINARIO DEDICADO AL TERCIARIO DE LA CUENCA DEL DUERO
Pol Méndez, C. & Carballeira Cueto, J. (1986): El sinclinal de Santo Domingo de Silos: Estratigrafía y paleogeografía de los sedimentos continentales (Borde Este de la Cuenca del Duero. Stvdia Geologica Salmanticensia, 22: 7-35.
ABSTRACT: The materials of continental origin (Upper Cretaceous to Miocene) which constitute the Eastern area of the Duero Basm and its contact with the northern branch of the Iberian Massif (Province of Burgos) define two large sedimentary cycles temporally separated by tectonic and erosive processes. These began in the Upper Cretaceous (Senonense) and are represented by three depositional sequences (closely related to episodes of Alpine orogeny): pre , sin and post tectonic. In them have been defined l4 lithostratigraphic Units (Pol, 1985), with are range of Formations.
The syncline of Santo Domingo de Silos constitutes one of best outcrops of the first depositional sequence, owing to the existence of a continuous Upper Cretaceous (Senonense) Paleogene continental series resting by net contact on the shallow marine sediments (barlagoon corresponding to the end of the marine cycle of the Upper Cretaceous.
These materials of the first deposition sequence, represented by the seven units described, are composed of sediments of fluvio lacustrian palustrian origin which define a large negative megasequence mainly characterized by its alluvial members. This in turn is composed of four minor alluvial/lacustrian megasequences.
The alluvial systems come from the N and NE and increase their proximity with time, pointing to several tectonic pulses. Among thee detritit units there are generalized rapid installation carbonated lacustrian episodes throughout the area, indicating the intervals of greatest stability.
Alonso-Gavilán, G., Recio, C., Fernández Macarro, B. & Blanco, J.A. (1986): Control sedimentológico de los procesos de alteración y rubefacción en la Formación Areniscas de Aldearrubia (Eoceno Superior, Salamanca). Stvdia Geologica Salmanticensia, 22: 37-59.
ABSTRACT: The present work is a contribution to the study of the alteration and rubefaction processes in the Aldearruhia Sandstone Formation whose sedimentological characteristics have been dealt with in previous works. Rubefaction is more or less generalized throughout the unit, though with important variations in intensity. It is manifested by a reddish tinge in the scarce clay matrix, the precipitation of Fe oxyhydroxides around the grains and the direct precipiation of oxides into small pores, Alteration has led to an important replacement of feldspar grains, micas and chlorites by smectites.
The findings reported reveal the existence of a perfect correlation between the alteration and rubefaction processes, both of them being maximal in the porous channel beds and minimal in the muds of the flood plain formed of paleosoils such that the greater the porosity and the greater the lateral proximity of the bed to active channels, the greater the intensity of both processes. This arrangement is anomalous with respect to similar series, where at least the strongest alteration processes are found associated with the sedimentary interruptions representing the paleosoils. Such a discrepancy is interpreted as a function of the dynamics of water fluctuations in the active channel and its interaction in the water table levels of the lateral porous beds.
Jiménez Fuentes, E. (1986): Redescubrimiento de unos fósiles hallados por J.Royo Gómez en Corrales (Zamora) en 1922. Stvdia Geologica Salmanticensia, 22: 61-70.
ABSTRACT: A description is made of certain fossils kept in the Natural Science Museum of Madrid (Spain) since 1922; these fossils are hitherto undescribed. The were originally found by J, Royo Gomez in subterranean cellars at Corrales del Vino (province of Zamora, Spain) and correspond to fish, crocodiles. (Iberosuchus, Diplocybodon) and chelonians (Neochelys, Allaeochelys) from the lower middle Eocene.
Alonso Gavilán, G. (1986): Paleogeografía del Eoceno Superior -Oligoceno en el SO de la Cuenca del Duero (España). Stvdia Geologica Salmanticensia, 22: 71-92.
ABSTRACT: Large fluviatile systems related to the erosion of the SE and SW borders (edges) of the Duero Basin flowed during the Late Eocene. The alluvial system attached to the W/NW areas laid down white sandstone, microconglomerate and conglomerate that slow, but continuously, prograded towards the SE and E changing in the process the channel pattern from sandy braided to proximal conglomerated braided.
The fluvial system draining the metamorphic areas placed towards the SE and E laid down the rcddish median to fine sands referred to as Aldearrubia Sandstone Formation. At first the channel pattern of the system was of median to high sinuosity, with large flood plain areas under pedogenic processes, but a change to sandy distal braided took place along with time.
By the Uppermost Eocene, both systems coalesced around the present day Vallesa de Guarena area, generating a mixed, indented white/reddish succession. Eventually, the unstable balance broke down under the effects of the Pirenaic (?) orogeny, which strongly favoured the enlargement of those systems flowing from the northwestern edges of the basin. Consequently, the Aldearrubia fluvia1 system was pushed toards th and, eventually, became inactive.
The southwestern areas of the basin also suffered the effect of the unstabilit large alluvial systems (Teso de la Flecha Conglomerates) brought down quartzitic sediments eroded away from the Peña de Francia Mountains (Early Ordovician).
As a conclusion, it is assumed that the sedimentation during Late Eocene was of fluvial origin, whereas large alluvial systems prograded in the Oligocene in responde to tectonisn.
Corrochano, A., Fernández Macarro, B., Recio, C., Blanco, J.A. & Valladares, I. (1986): Modelo sedimentario de los lagos neógenos de la Cuenca del Duero. Sector Centro - Occidental. Stvdia Geologica Salmanticensia, 22: 93-110.
ABSTRACT: In the inner neogene sediments of the Duero Basin, three facies associations have been identified: A, B and C. Their vertical siicession establihes a sedimentary pattern of evolution in the Basin, which begins with fluvial facies and finishes with lacustrine facies. The latter have post sedimentary processes superpose due to palustrine conditions.
The association A was deposited in fluvial channels of high sinuosity and flood plains with thick calcretes.
The association was deposited in a mud flat. The main processes were: mud accumulation, freatic level oscillations and long periods of subaereal exposures. Two areas have been identified in this mud flat: one is quite well drained and the other is not drained in the least.
The association C belonged to broad lakes, which were very shallow and which had strong oscillations of the water level. The nearshore zone is formed by two lithofacies detrital and calcareous (wackestone). The central area is dominated by marles sedimentation. The above mentioned conditions in the central zone are only interrupted by thin beds of packstone, which are interpreted as channel coming from the nearshore.
On this depositional context palustrine facies are placed. These are characterised by vegetation colonization over nearshore lacustrine lithofacies (wackestone with roots) and by the development of intense pedogenetic processes, accompanied by the sedimentation of black claystones. With the exception of packstones, the other lacustrine lithofacies are affected by pedogenetic processes.
Mediavilla, R.M. & Dabrio, C.J. (1986): La sedimentación continental del Neógeno en el sector centro - septentrional de la Depresión del Duero (provincia de Palencia). Stvdia Geologica Salmanticensia, 22: 111-132.
ABSTRACT: Neogene deposits are well exposed around Palencia (Duero Basin, Spain). From the study of ten sections, up to four informal lithostratigraphic units were recognized including siliciclastic, carbonate and gypsiferous facies that were recorded and interpreted.
The BASAL UNIT (Astaracian) is made up of red to brownish mudstone with interlayered bodies of sandstone, limestone and marl. It was aid down by fluviatile systems of high sinuosity channel pattern and complex flood plain including backswamp and lacustrine realm.
The LOWER UNIT (Middle Astaracian) consists of mudstone and carbonate deposits with pedogenic layers both as rooted carbonate and black shale horizons. Two informal members can be separated: the lower one corresponds to palustral, fluviatile and lacustrine sediments, whereas the upper one was laid down in lakes with fluctuating water level and localized fluviolacustrine influx from the northern edge where flood plain facies are found.
The MIDDLE UNIT (Upper Astaracian to Upper Vallesian) consists of marly sediments with large crystal of gypsum and interlayered turbidite like clastic gypsum, limestone and dolostone in the eastern sector, and interbedded green mudstone and carbonates in the western sector. All them are the result of deposition in arid lacustrine environments. In the central part, a mixed terrigenous-gypsiferous assemblage is found: units of lenticular shape displaying coarsening upwards sequences are interpreted as lacustrine deltas. The source area of the remobilized gypsum should be placed towards the NE and that of siliciclastics, towards the NNW.
The badly preserved sediments of the UPPER UNIT (Upper Vallesian Turolian Pliocene?) consist of lacustrine limestone and mudstone, very much alike those of the lower unit: shallow lakes of fluctuating water level are assumed as well. The lack of gypsum and the commom calcification of the underlying sediments of the Middle Unit, suggest that the salinity of the water was not too high.
The shematic palaeogeographical evolution has been expresed graphically for better understanding.
Rivas Carballo, R. & Valle, M.F. (1986): Nuevas aportaciones a la palinología del Terciario de la Cuenca del Duero. Torremormojón (Palencia). Stvdia Geologica Salmanticensia, 22: 133-143.
ABSTRACT: The present work describes the palinological study of the Torremormojón section (Palencia) of the upper Pliocene of the Duero Basin.
Pollen analysis reveals a slight predominance of Gymnosperms over Angiosperms. Within these latter, two families, Arecaceae (= Palmae) and Fagaceae, are outstanding, followed in predominance by Ericaceae and Oleaceae (Fraxinus and Phillyrea). Regarding the pollen from sources other than trees, the Family Poaceae (= Gramineae) is noteworthy in the pollen spectrum, followed to a lesser extent by Amaranthaceae Chenopodiaceae, wich are always present.
Pteridophyta are very scarce and yet the presence of Zygnemataceae, Dinoflagellates and other non palinomorphic organic remains are very abundant.
These data point to the existence at Torremormojón of a lake environment which underwent expansions and contractions possibly due to local climatic changes. Suc changes would have modified the plant layer. The warm and humid tertiary elemen alternating with the temperate Mediterrenean like elements (humid or dry).
Álvarez Sierra, M.A. & García-Moreno, E. (1986): New Gliridae and Cricetidae from the Middle and Upper Miocene of the Duero Basin, Spain. Stvdia Geologica Salmanticensia, 22: 145-189.
ABSTRACT: In this paper a new genus (Myolidus, Gliridae) and four species (Ramys perezi, Peridyromys rex, Gliridae; Megacricetodon lopezae, Megacricetodon freudenthali, Cricetidae), are described from the upper Aragonian and lower Vallesian of the Torremormojón and Ampudia sections. These sections contain six three superposed localities respectively.
López Martínez, N., García Moreno, E. & Álvarez Sierra, M.A. (1986): Paleontología y bioestratigrafía (Micromamíferos) del Mioceno Medio y Superior del sector central de la Cuenca del Duero. Stvdia Geologica Salmanticensia, 22: 191-212.
ABSTRACT: In the central area of the Duero Basin, 14 micromammal associations have been elected over a total of 80 fossil bearing localities, and a 4 biozone sequence has been established for the Middle Late Miocene transit, on a sedimentary sequence about 200 m thick. The four assemblage zones are:
a) at the bottom, the Megacricetodon lopezae zone. This zone also contains M. minor, M. crusafonti, Peridyromys rex, Chalicomys jaegeri and Prolagus major.
b) the Megacricetodon ibericus zone. Other taxa present in this zone are Microdyromys koenigswaldi and Ramys perezi.
c) the Cricetulodon hartenbergeri zone. It also contains Megacricetodon freudenthali, Ramys perezi and Eomyops catalaunicus. Progonomys hispanicus is present in small number.
d) the Progonomys hispanicus zone. This zone also contains Myolidus sinuosus, Ramys cf. multicrestatus and Rotundomys montisrotundi.
Carballeira Cueto, J. & Pol Méndez, C. (1986): Características y evolución de los sedimentos lacustres miocenos de la región de Tordesillas ("Facies de las Cuestas" en el sector central de la Cuenca del Duero). Stvdia Geologica Salmanticensia, 22: 213-246.
ABSTRACT: In the central sector of the Duero Basin, the region situated to the north of the town of Tordesillas (National Topographic Map Sheet Nº 371, Spain) exhibits the presence of detritic and carbonated materials of Miocene age represented by four major lithostratigraphic Units.
The present work focuses on the stratigraphic and sedimentological aspects of one such unit known as the "Facies de las Cuestas" which has a clear lacustrian character. The correlation of the different uplifted sections by guide levels characterized by accumulations of Gasteropods, points to the existence of three lesser Lithostratigraphic Units (III A, III B and III C) valid for the region and neighbouring sectors, corresponding to a further three positive megasequences. The basal part starts in the infradjacent fluvial sediments.
The facies of these Units define several lacustrian subenvironments: marginal lacustrian (litoral and sublitoral) and open lacustrian, which have been sporadically subjected to process of palustrian and pedogenetic diagenesis.
The facies, geometry of the lithofacies, associations and sequences are suggestive of a lacustrian sedimentation model and of its evolution as time progressed from freshwater to salt water conditions.
Armenteros, I., Fernández Macarro, B., Recio, C. & Blanco, J.A. (1986): Análisis sedimentológico y paleogeografía en el Mioceno del sector Sacramenia (Segovia) - Peñafiel (Valladolid). Stvdia Geologica Salmanticensia, 22: 247-262.
ABSTRACT: The present work is a contribution to sedimentological studies on the Miocene facies of the southeastern region on the Duero Basin (Sacramenia -Peñafiel zone).
In this area analyses were made of the clays in three profiles chosen along a study line situated between the marginal facies adjacent to the southern basement on Honrubia and the central facies of the Basin situated towards the N (Peñafiel). The interpretation of these analysis reveals a change in the paleogeographic conditions along the section. In this sense, in the northern zone it is possible to note a predominance of inherited chays (illite, kaolinite-chlorite, smectites), with the localizad appearance of paligorskite linked to the development of carbonated crusts and intertitial gymsum. In the closest zone, an association of clays with sepiolite as the major component predominates; this is accompanied by a highly characteristic mineral grouping: silex (CT opal), dolomite, gypsum and celestine.
The mineralogical set and the remaining sedimentological characteristics of the bed of the first zone (Bocos de Duero profile) point to a distal sinuous fluvial system originating in the East, with marked periods of drought. The lutitic-marly sediments of the area closest to the Honrubia border are characterized by the presence of a confined lacustrine environment which proves to be expansive over the fluvial system situated to the North.
Finally, the results point to the existence of a paleogeographic development where sedimentation took place in subbasins which could have had autonomy during certain stages of their evolution.
Armenteros, I., González Delgado, J.A., Civis, J. & Dabrio, C.J. (1986): El problema del Neógeno Superior en la Cuenca del Duero: Nuevos datos paleontológicos (invertebrados) en el sector Peñafiel - Almazán. Stvdia Geologica Salmanticensia, 22: 263-275.
ABSTRACT: Together with the general lithostratigraphic characteristics of the Neogene of the southeast sector of the Duero Basin, new paleontological data are provided (Gastropoda and Ostracoda) which demarcate a succession of events and changes in the assemblages through out the general stratigraphic column.
There are several outstanding taxons of Gastropoda such as Hydrobia schlosseri, H. gr. deidieri, Valvata, Bithynia, Planorbis, Melanopsis and Theodoxus. Regarding the Ostracoda, the appearence was noted specially of ?Paracandona, Gen. indet. sp. 1, Lineocypris, Subulacypris and Candona aff. bitruncata.
As well as establishing the correlation between the different sections, paleontological group also points to a more modern age than those of the bed situated towards the centre of the basin; this would not conflict with the general deposits of such beds and their relation with the topographic level.
The presence of forms attributable to Cyprideis torosa, in the Valles de Fuentidueña poses a chronostratigraphic problem and suggests the need to revise the age of the bed or the Ostracoda distribution.
González Delgado, J.A., Civis, J., Valle, M.F., Sierro, F.J. & Flores, J.A. (1986): Distribución de los foraminíferos, moluscos y ostrácodos en el Neógeno de la Cuenca del Duero. Aspectos más significativos. Stvdia Geologica Salmanticensia, 22: 277-291.
ABSTRACT: The study of Mollusca, Foraminifera and Ostracoda in the stratigraphic sections representative of three sectors of the Neogene of the Duero Basin (Central sector), Peñafiel Almazán and Castrillo del Val establishes different assembleges and the temporal and spatial changes taking place in them.
in m Regarding the Gastropoda, the abundance of specimens contrasts with the small number of species present; in the central sector the dominant forms correspond to Valvata, Bithynia and Anisus; in the sector of Peñafiel Almazán Hydrobia schloseri is extremely common and at Castrillo del Val, Hydrobia, Melanopsis laevigata and Potamides tricintum.
The Ostracoda are represented mainly by Ilyocypris gibba, Cyprinotus salinus and Cyprideis tuberculata in the central sector; they are represented by different taxons such as Lineocypris and Subulacypris in the Peñafiel Almazán area, and by Cyprideis torosa in Los Valles de Fuentidueña, posing problems regarding chronostratigraphy. The replacement of C. tuberculata by the great predominance of Darwinula is the most salient aspect of Castrillo de1 Val.
The changes appearing in the Ostracofauna are accompanied by the appearance and predominance of Foraminifera in several sections. Ammonia tepida appears as dominant in the central sector whereas in the sector of Castrillo del Val the assemblage of Nonion granosum and Miliolids is outstanding, together with C. tuherculata.
A general scheme is presented for the distribution and changes in the assemblages found in each sector and the paleoenvironmental implications are discussed.
Molina, E. & Armenteros, I. (1986): Los arrasamientos Plioceno y Plio-Pleistoceno en el sector suroriental de la Cuenca del Duero. Stvdia Geologica Salmanticensia, 22: 293-307.
ABSTRACT: In the SE. border of the Duero Basin (central Spain) a set of planation surfaces has been found. These surfaces are the remainds of two pediments developed on Mesozoic and Tertiary series and represent the more important morphological feature of the region.
The oldest pediment is located between 1170 1040 m. height and, owing to its position within the geological and morphological evolution of the region, a Pliocene age is attributed. It is characterized by displaying a karst more than 5 m. deep which holes appear filled up by red clays, traditionally considered as "Terra Rossa", composed by kaolinites and illites micas. The contact between the limestone and the "Terra Rossa" shows reaction borders and recrystallization of calcite within the red clays.
This first surface is eroded by the alluvial fans of the "Raña" formation within which is possible to distinguish two levels. The base of the lower level in the beginning of the new pediment at about 960 m. height close to the sierra of Honrubia Pradales.
This new pediment is located between 960 850 m. height and cronologically represents the Plio Pleistocene transition. It is characterized by displaying a new karst no more than 3 m. deep, their holes being filled up by a new and more sandy material in which clay illuviation processes are very important. The clay fraction is composed of smectite, kaolinite and illite micas and there is not reaction borders with the limestones.
Corrochano, A. & Pena dos Reis, R. (1986): Analogías y diferencias en la evolución sedimentaria de las Cuencas del Duero, Occidental portuguesa y Lousâ (Península Ibérica). Stvdia Geologica Salmanticensia, 22: 309-326.
ABSTRACT: Three sedimentary basins linked to the evolutive history of Hesperic Massif during the Cretaceous and the Tertiary Times are described and contrasted: Duero Basin, Wetern Portuguese Basin and Lousâ Basin.
All of them are filled with continental deposits; alluvial and lacustrine deposits. There only exist shallow marine sediments, of searce importance, in the Western Portuguese Basin.
Although the structural settings of the basins are different they have similar features that give evidence of convergent stages in their sedimentary evolution. These features are: the megasequencial architecture they have in common and the existence of silcretes in equivalent stratigraphic positions.