This study concerns the facies analysis and the reconstruction of depositional environments of the basal, terrigenous portion of the Upper Cretaceous sedimentary succession, located in the southern margin of the «Sierra the Guadarrama» Mountains (North of Madrid, central Spain), which is a portion of the Spanish central Chain called «Sistema Central». The terrigenous deposits studied, about 90 m tick, are constitued by three formations: the «Arenas the Utrillas», the «Arenas y arcillas de Castro de Fuentidueña» and the «Arenas y arcillas de Segovia» wich age is enclosed between Cenomanian and Early-Middle Coniacian. The «Arenas de Utrillas» (Cenomanian), mainly constituted by sandstones and conglomerates, are related to a braided bedload coarse sand river. Paleocurrent analysis evidences at least, within the “Arenas de Utrillas” formation, the presence of three fluvial systems flowing about side by side. The «Arenas y arcillas de Castro de Fuentidueña» (Early Turonian-Early Coniacian) record a transgressive-regressive sedimentary cycle first characterized by clay and sandstone deposited in a coastal environment dominated by tidal processes. A phase of maximum flooding is evidenced by the development of autochtonous glaucony-rich deposits while the transition to tidal deposits represents the final regressive phase. The «Arenas y arcillas de Segovia» (Early-Middle Coniacian), which lie disconformably above The «Arenas y arcillas de Castro de Fuentidueña», represented the beginning of another sedimentary cycle with a development of another marine transgression. The sedimentary features observed match with coastal tide-dominated depositional environment except for a small area, that was not flooded by marine waters, and where are preserved the laterally equivalent deposits in fluvial facies.
|Autori:||Guidi R.; Mas R.; SARTI G.|
|Titolo:||Analisi di facies dei depositi terrigeni del Cretaceo superiore del versante sud della "Sierra de Guadarrama" (Madrid, Spagna centrale): dati preliminari|
|Anno del prodotto:||2004|
|Appare nelle tipologie:||1.1 Articolo in rivista|