STRUCTURE-STRATIGRAPHY INTERACTIONS IN A PIGGYBACK BASIN SETTING, AINSA BASIN, SPAIN
The Ainsa unit contains submarine channels that entered the basin from the east and exited the basin to the northwest, although some channels locally transfer to lobes near the northwest end of the basin. The Morillo unit contains submarine channels that entered the basin from the east, dispersed onto the basin floor, then converged at the western end of the basin where they continued onto the longitudinally adjacent Jaca Basin. The Guaso unit contains submarine channels that entered the basin from the east and transfer to a ponded distributive submarine fan at the center of the basin. The Escanilla-Sobrarbe unit contains a linked shelf-to-basin system that prograded from south to north and records the final filling of the basin. Four lines of evidence collectively support the basin-fill succession was deposited during structural growth. First, the depocenter, which is interpreted to reflect the position of maximum subsidence during deposition, of the systems systematically shifted westward as the basin filled. Second, the axial part of the clastic sediment systematically shifted southward as the basin filled. Third, the stratigraphic units are locally separated by progressive unconformities at the Mediano Anticline. Forth, carbonate-clast, sediment-gravity flow deposits were continually sourced off of the Boltana Anticline. The upward succession generally records a shallowing of the basin through time indicating that sediment supply exceeded the rate at which accommodation was created in the basin.