A coarse-grained delta lobe in the Oligocene conglomerates of the Montsant Formation: initial considerations (Pobla de Cèrvoles, Lleida, Spain).
DOI:
https://doi.org/10.55407/geogaceta95526Keywords:
Montsant Formation, Serra de la Llena, alluvial fan, fan deltaAbstract
The conglomerates of the Montsant Fm have been studied stratigraphically, structurally, and sedimentologically with varying results. We studied a conglomeratic body that has not yet been described in detail. The main aim of the present work is to elucidate the genesis and depositional significance of this body. The conglomeratic lithosome displays large cross bedding (foresets) that extend continuously from the bottom to the top for meters. It could have been generated because of the development of a coarse-grained fan delta lobe in a context of episodic progradation of large alluvial fans. Thus, between the gravel-rich courses that carry huge amounts of rounded clasts due to hydraulic discharges were small, flooded depressions
generating temporary lakes with a predominantly mudrich accumulation. In such scenario, a small fan delta lobe could have developed. The sub horizontal conglomeratic levels located in the upper part of the main conglomeratic lithosome (topsets) indicate the maximum water level reached of the temporary lake. The overlying lutitic materials also represent the mud-rich accumulation led to the decantation of lacustrine waters. The progradation of the coarse- grained lobe and the large alluvial fans occurred in this area along the Oligocene.
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