Tertiary of Central System basins

The rise of the Central System due to reactivation of late Hercynian fault systems during the Alpine Orogeny directly affected the strcture and stratigraphic framework of the basins nearby that were being filled al the same time. The sedimentary record is the essential key to understanding the tectonic and palaeo-morphological history, of the Central Range, and vice-versa. Relating the filling of the basins with the definition of the mountain range, pre-arkosic, arkosic and post-arkosic stages have been proposed. However, it is difficult to support the previous idea that the arkosic stage continued throughout the Late Tertiary to finish in Middle Pliocene.: times withe the deposition of the Paramos(limestone). The arkoscs of the Central System arc of Eocene-Oligocce age and the highest alluvial fan deposits may be of Aragonian age. There is only a poor record of the remaining Tertiary and Quaternary sediments. boeause of active river incision during this lime in the hasins, the ranges and elsewhere in the Spanish Meseta

Sedimentación de plataforma durante el Carbonifero Inferior (Formación Terena) en el área de Santa Olalla del Cala (Huelva, España)

La Formación Terena (Carbonifero Inferior) representa un caso de sedimentación de plataforma en un contexto tectónicamenle activo. La sucesión general está constituida por una unidad basal carbonatada seguida de tres unidades terrígenas de caracter granodecreciente. La unidad basal representa depósitos de plataforma carbonatada estable mientras que las unidades siliciclásticas se interpretan en relación con corrientes de resaca densas y diluidas producidas por oleajes de tormenta. El depósito de la Fomación Terena registra un cambio en la naturaleza de la cuenca, que pasa de carbonatada a siliciclástica, con tres episodios de desestabilización relacionados genéticamente con pulsaciones tectónicas. [ABSTRACT] The Lower Carboniferous Terena Formation records deposition on a tectonically active shelf context. It is composed of a carbonate basal unit followed upwards by three fining upwards silicic1astic units. The basal unit represents sedimentation on a stable shelf. The siliciclastic units record sedimentation from dense and dilute storm surges on an unstable shelf. These deposits record a change in the nature of the basin, from carbonate to silieiclastic realms, with three episodes of reactivation genetically related to three tectonic pulses

Alpine tectonic framework of south-western Duero basin

The tectonic activity in the south-western area of the Spanish Northern Meseta (Ciudad Rodrigo and Duero basins) during most of the Tertiary was determined by u transpressive regime that reactivated Hercynian to Late-Hercynian faults. The record of the Alpine Orogeny is complex because the sedimentary record indicates a compresive regime in the sour e areas coeval with the extensionall to transpresive regime indicated by normal or strike-slip faults. This duality is due 10 the geotectonics position of this area between two compressive areas, the Cantabrian Range and the Central System, and the extensional Atlantic margin

North-western Cainozoic record: present knowledge and the correlation problem

Tertiary deposits of the north-western Iberian Peninsula are heterogeneous because they occur in several morpho-structural positions as isolated and dispersed basins and outerops. The quality of the palaeontological record is usually very poor and there are scarce data. Correlation depends on a wide range of criteria which arc not always equivalent: palaeontology, mineralogy and petrology, geomorphology, tectonics and comparison with better-known and better-dated facies in regions nearby. The results lack homogeneity and there arc notable discrepancie

Introducción a la estratigrafía del Terciario del SO de la Cuenca del Duero

Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEpu

Reconstruction of drought episodes for central Spain from rogation ceremonies recorded at the Toledo Cathedral from 1506 to 1900: A methodological approach

Rogation (ceremonies to ask God for rain: pro-pluvia, or to stop raining: pro-serenitate) analysis is an effective method to derive information about climate extremes from documentary data. Weighted annual sum by levels has been a widespread technique to analyze such data but this analysis is liable to be biased to spring values as these ceremonies are strongly related to farming activities. The analysis of the length of propluvia periods (the time span during which rogations are carried out in relation to a drought event) and the combination of annual and seasonal information offers a more objective criterion for the analysis of the drought periods and an increase in the resolution of the study. Analysis by the pro-pluvia periods method of the rogation series from the Toledo (central Spain) Cathedral Chapter allows a good characterization of the droughts during the 1506–1900 period. Two drought maxima appear during the 1600–1675 and 1711–1775 periods, characterized by rogations during almost all the year, with a middle stage (1676–1710) when droughts were less frequent and their length shortened. Sea level pressure patterns for the instrumental and documentary periods show that droughts were mostly related to a north-eastern position of the Azores High that displaced the Atlantic lowpressure systems towards a northern position. There is a weak relation with the North Atlantic Oscillation but this fact is related to the local character of the series that increases the weight of the local factors. Comparison of rainfall/drought records around Spain and theWestern Mediterranean reveals the heterogeneity of their distribution in time and space as well as stresses the need of more and longer reconstructions. Better knowledge of drought variability would help to improve regional models of climate extremes and the understanding of the atmospheric patterns related to their development

Evolución de eventos climáticos extremos (inundaciones y sequías) para la zona central de la Península Ibérica desde el siglo XVI a partir del registro de rogativas e inundaciones históricas.

En este trabajo se presenta la evolución desde 1500 a 1900 de dos tipos de eventos climáticos extremos característicos de la Península Ibérica, las inundaciones y las sequías. Este estudio se ha llevado a cabo en la meseta sur de la Península. Aprovechando la continuidad del registro documental desde el s. XVI hasta nuestros días para la zona de estudio, hemos utilizado registros de rogativas e inundaciones históricas del rio Tajo, acaecidas en Aranjuez, Toledo y Talavera. En los cuatro siglos estudiados, parece que los periodos en los que hay una alta frecuencia de sequías también existe una alta frecuencia de inundaciones, aunque estos eventos raramente coinciden en un mismo año. En función de la frecuencia y la intensidad de los eventos, se han distinguido seis periods, dos con una alta frecuencia de eventos (1557-1623), (1717-1798), uno con frencuencia media (1624-1716), dos con frecuencias bajas (1500-1556) y (1798-1850), debido probablemente a un aumento de la presión antrópica sobre los cauces y una disminución en la frecuencia de rogativas por motivos sociopolíticos

Cenozoic lacustrine deposits in the Duero Basin (Spain)

Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEpu

South-western Duero and Ciudad Rodrigo basins: infill and dissection of a Tertiary basin

In the soult western sector of the intracontinetal Duero basin, the post-Hercynian sedimentary record consist of Upper Cretaceous to Quaternary terrestrial sediments. Climates shifted from tropical, with poorly defined seansos (end of Cretaceous), to Mediterranean (Neogene). Tertiary deposits are divided into three tectonographic completes. The Late Cretaceous-Paleocene, related to the end of the Mesozoic cycle, is caractericed by a well developed weathering profile that eroded later. The Eocene Oligocene, formed during the morpho-structural definition of the actual basin boundaries, consists of three unconformity-bounded units related to successive tectonic events of the Alpine Orogeny by the cnd of this cycle, progressive incision of the Atlantic nuvial network led to capture of the fluvial systems of the southern Duero basin and degradation (emptying) began. The Miocene-Phocene, related to and extensional tectonic regime represents the spreading of exorheik conditions to the whole basin that marked a complete hydrugraphic reorganisation. Deposition and aggradation continued in more central areas of the basin until the end of the Neogene, coeval with degradation of the south-western corner of the Duero Basin. The coexistence resulted from differential subsidence, hinge lines (uplift zones) separated sub-basins, and the dynamics of capture processes

Lacustrine Neogene systems of the Duero Basin: evolution and controls

Vertical aggradation of Neogene fluvial and lacustrine deposits occurred until the Late Neogene in central and northem areas of the Duero Basin, coeval with river incision in the southwestern corner of the basin. The whole basin became exorheic in the Latest Neogene. We have differentiated five tectonosedimentary units (TSUs) of basinal extent, bounded by unconfonnities or breaks in the sedimentary record. Deposits in each TSU consist of alluvial-fan deposits in areas close to the active northern and eastern margins, and fluvial deposits along the western margin. These systems converged in the lower, subsiding areas of the basin occupied by carbonate-evaporite lacustrine systems. Tectonics and climate controlled sedimentation. The main faults active from the Neogene to the Present reflect Late Hercynian basement fractures that were re-activated during the Alpine Orogeny, both fracturing blocks and modifying landscapes, and creating or modifying the areas of subsidence. Analysis of climatic variations during the Miocene shows that deposition of saline materials occurred in dry TSUs (1, 2) and, particularly, in humid TSUs (3,4). Climate does not seem to have been a determining factor for the formation of evaporites. However, it was a very important factor in determining both the amount of water that reached the basin and, eventually, also the extent of the lacustrine systems