El Cretácico del borde septentrional de la Rama Castellana de la Cordillera Ibérica

Abstract

Along the northern border of the Castilian branch of the Iberian Ranges, in the boundary with the Almazán Tertiary Basin, several isolated outcrops of Cretaceous sediments exist. The stratigraphy of these outcrops is rather complex due to the absence of long and complete sections, which is caused both by the isolation of the outcrops, covered by Tertiary sediments, and, within each outcrop, by the presence of abundant normal faults. Thus, the correlation of short and incomplete sections is the only way to make an accurate stratigraphy. The age of the studied succession ranges from Upper Cenomanian to Lower Campanian, but its base can reach the Lower Cenomanian or even be older (Lower Cretaceous). The succession starts with littoral and fluvial sandstones and then grades upwards into shallow marine carbonate sediments. Two episodes of hemipelagic marl deposition grading upwards into open platform nodular limestones extended from the uppermost Cenomanian to Lower Turonian times and from the Upper Coniacian to Lower Santonian times. There is an aggradational stacking pattern with a slight truncation at the middle of the sedimentary package. The Cretaceous succession thins both north-westwards and south-eastwards in relation to the transition to continental areas, suggesting that the basin was a broad and shallow trough. The studied area is relevant for the Cretaceous palaeogeography in the Iberian Peninsula because this is an area where lateral facies changes between well-known Cretaceous lithosomes occur, allowing both the establishment of more precise genetic relationships between them and the correlation between Cameros, the Aragonian Iberian Ranges, the rest of the Castilian Iberian Ranges and the Central System. The stratigraphic record is organised into nine lithostratigraphic units and nine 3rd order depositional sequences.