La secuencia deposícional del Turoniense superior en el borde meridional de la Sierra de la Demanda (Cordillera Ibérica septentrional, provincias de Burgos y Soria)

Resumen

In the Northern Iberian Range, the upper Turonian is formed by the Muñecas Fm., a unit composed mainly of bioclastic limestones and characterised by a great stratigraphic homogeneity and a high regional continuity. These sediments are genetically related as a depositional sequence bounded by regional discontinuities. This sequence was originated by a cycle of relative sea level rise and fall located in the base o f an important 2nd order transgressive-regressive cycle. Internally, the sequence is arranged in several 4th order parasequences bounded by minor discontinuities, defining a model of organisation o f the record in which there are a superimposition of several orders of sedimentary cycles. A detailed sequential analysis of the third order sequence has been carried out, describing sequence and parasequence boundaries, which show that sequence boundaries are not exactly coincident with those of the lithostratigraphic unit. On the other hand, the depositional architecture has been reconstructed in the study area, showing the organisation of 3rd and 4th order System Tracts and the location of maximum flooding surfaces (MTS). The MTS for each parasequence is located in the lower part, delimiting a thin TST composed of bioclastic remobilized sediments, and a thick HST with an aggradational tendency.