Publication: La sedimentación continental del Neógeno en el Sector Centro-Septentrional de la Depresión del Duero (Provincia de Palencia)
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Publication Date
1986
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Universidad de Salamanca
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Abstract
Alrededor de Palencia (Depresión del Duero) afloran materiales de edad Neógeno (Fig. 1). Del estudio de diez series estratigráficas se han establecido cuatro unidades litoestratigráficas informales (Fig. 2, 3) que incluyen sedimentos siliciclásticos, carbonatados y yesíferos en los que se han diferenciado e interpretado facies sedimentarias (Fig. 4). La UNIDAD BASAL (Astaraciense) consiste en arcillas rojizas o pardas con cuerpos de arenisca, calizas y margas y fue depositada por sistemas fluviales de canales sinuosos y llanuras de inundación complejas incluyendo zonas pantanosas y lagunares (Fig. 5). La UNIDAD INFERIOR (Astaraciense Medio) está formada por arcillas y carbonatos con niveles edáficos tanto en forma de horizontes de calízas de grandes raíces como de arcillas negras (Fig. 6). Pueden distinguirse dos miembros informales: el inferior corresponde a depósitos fluviales, palustres y lacustres, mientras que el superior se depositó en lagos con aportes siliciclásticos localizados f1uviolaustres en el margen norte, donde llegan a encontrarse facies de llanura de inundación (Fig. 9). La UNIDAD MEDIA (Astaraciense superior a Vallesiense superior) consiste en sedimentos margosos con cristales de yeso e intercalaciones de yesoarenitas de tipo turbidítico y carbonatos (calizas y dolomías) hacia el este y de alternancias de arcillas verdes y carbonatos en el oeste. Todos ellos se depositaron en ambientes lacustres en clima árido. En el sector central, se encuentra una sucesión mixta terrígena y yesífera, con unidades lenticulares que muestran megasecuencias granocrecientes, interpretadas como deltas lacustres (Fig. 7). El área fuente del yeso removilizado debía situarse al noreste y la de los siliciclásticos al N/NW (Fig. 8 y 9). Los materiales de la UNIDAD SUPERIOR (Vallesiense superior-Turoliense-Plioceno ?) están mal conservados por el carácter erosivo de la superficie limitante. Consiste en calizas y lutitas lacustres similares a las descritas en la Unidad Inferior: serían sedimentos de lagos someros de nivel fluctuante. La ausencia de yeso y la calcificación de los materiales infrayacentes se suponen signos de que la salinidad de las aguas era relativamente baja. La evolución paleogeográfica de conjunto puede expresarse gráficamente para su mejor comprensión (Fig. 9).
Neogene deposits are well exposed around Palencia (Duero Basin, Spain, Fig. 1). From the study of ten sections, up to four informal lithostratigraphic units were recognized (Fig. 2, 3) including siliciclastic, carbonate and gypsiferous facies that were recorded and interpreted (Fig. 4). The BASAL UNIT (Astaracian) is made up of red to brownish mudstone with interlayered bodies of sandstone, limestone and marl. It was laid down by fluviatile systems of high-sinuosity channel pattern and complex flood plain including backswamp and lacustrine realms (Fig. 5). The LOWER UNIT (Middle Astaracian) consists of mudstone and carbonate deposits with pedogenic layers both as rooted carbonate and black shale horizons (Fig. 6). 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 (Fig. 9). The MIDDLE UNIT (Upper Astaracian 10 Upper Vallesian) consists of marly sediments with large crystal of gypsum and interlayered turbidite-like clastic gypsum, limestone and dolos tone in the eastern sector, and interbedded green mudstone and carbonates in the western sector (Fig. 7). 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 (Fig. 7, 8). The source area of the remobilized gypsum should be placed towards the NE and that of siliciclastics, towards the N/NW. The badly-preserved sediments of the UPPER UNIT (Upper Vallesian-Turolian-Pliocene?) consist of lacustrine limes tone 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 waters was not too high. The shematic palaeogeographical evolution has been expresed graphically for better understanding (Fig. 9).
Neogene deposits are well exposed around Palencia (Duero Basin, Spain, Fig. 1). From the study of ten sections, up to four informal lithostratigraphic units were recognized (Fig. 2, 3) including siliciclastic, carbonate and gypsiferous facies that were recorded and interpreted (Fig. 4). The BASAL UNIT (Astaracian) is made up of red to brownish mudstone with interlayered bodies of sandstone, limestone and marl. It was laid down by fluviatile systems of high-sinuosity channel pattern and complex flood plain including backswamp and lacustrine realms (Fig. 5). The LOWER UNIT (Middle Astaracian) consists of mudstone and carbonate deposits with pedogenic layers both as rooted carbonate and black shale horizons (Fig. 6). 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 (Fig. 9). The MIDDLE UNIT (Upper Astaracian 10 Upper Vallesian) consists of marly sediments with large crystal of gypsum and interlayered turbidite-like clastic gypsum, limestone and dolos tone in the eastern sector, and interbedded green mudstone and carbonates in the western sector (Fig. 7). 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 (Fig. 7, 8). The source area of the remobilized gypsum should be placed towards the NE and that of siliciclastics, towards the N/NW. The badly-preserved sediments of the UPPER UNIT (Upper Vallesian-Turolian-Pliocene?) consist of lacustrine limes tone 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 waters was not too high. The shematic palaeogeographical evolution has been expresed graphically for better understanding (Fig. 9).