SEDIMENT TRANSPORT MODEL FOR THE EOCENE ESCANILLA SEDIMENT-ROUTING SYSTEM: IMPLICATIONS FOR THE UNIQUENESS OF SEQUENCE STRATIGRAPHIC ARCHITECTURES

摘要

Stratigraphic architectures are fundamentally controlled by the interplay at different temporal and spatial scales of accommodation and sediment supply, modulated by autogenic responses of the sediment routing system and its constituent segments. The flux and caliber of sediment supply is a function of climate, catchment area, and tectonics in the source regions, and unraveling these forcing mechanisms from the observed stratigraphic architecture remains a key research challenge. The mid-to-late Eocene Escanilla sediment routing system had its source regions in the south-central Pyrenean orogen, northern Spain, and transported sediment from wedge-top basins along tectonic strike to marine depocenters. By constructing a volumetric budget of the sedimentary system, it has been demonstrated that there were marked changes in the grain-size distribution released from the sediment sources and also in the position of the gravel front, across three similar to 2.6 Myr time intervals from 41.6 to 33.9 Ma. Classical sequence stratigraphic interpretations would relate the movement of depositional boundaries such as the gravel front to changes of base level, either in isolation or in combination with sediment supply. Herein, we explore the possibility that the position of the gravel front was primarily driven by variability of grain-size distributions released from the source regions as a result of changes in catchment uplift rate and/or surface run-off.