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5.3. Clast provenance
5.4. Transport processes of the MTDs in the Pisuerga area
5.5. Triggering mechanisms of MTD
6. Geometry of the Castillería–Casavegas and Redondo piggy-back basins
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Fig. 11.
Schematic palaeogeographic sketches depicting the basin 10058-F4 in the Pisuerga area during the Pennsylvanian (early Moscovian–early Kasimovian). The three synclines represent two piggy-back troughs (Castillería–Casavegas and Redondo depocentres). These two depocentres represent just a portion of the original wedge-top basin. No scale involved.
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The size distribution of the clasts of MTDs indicates that the western limbs of the three synclines represent the proximal and more unstable sectors of the two depocentres, located in front of the La Pernía and Redondo fault-propagation anticlines, from where the clasts derived. These two anticlines (palaeohighs) would have been the most favourable site for the nucleation and growth of carbonate systems (Dorobek, 1995). In contrast, the Agujas MTD, with the opposite size distribution of the clasts, and an eastward passage into a nearly autochthonous carbonate unit (Fig. 3), would witness the destruction of a carbonate platform located to the east and belonging to the sequence II. These limestones are still preserved in the upper half of the sequence II in the Casavegas and Castillería synclines. It is interpreted mammal-like reptiles the collapse of the Agujas limestone unit would have been provoked by the growth of a fault-propagation anticline bounding the Redondo syncline in the east (Fig. 10).