Reinterpretation of the Quaternary sedimentary infill of the Ria de Vigo, NW Iberian Peninsula, as a compound incised valley

Seismic data have been used to investigate the stratigraphy of the Galician rias for more than two decades. Here, we present a new interpretation of the sedimentary infill of an incised valley (Ria de Vigo, NW Iberian Peninsula), based on high-resolution seismic profiles, core sediment analysis, and radiocarbon C-14 data. The new data indicate that the stratigraphic architecture of the Galician rias result from multiple incision/infill phases and, therefore, they are reclassified as compound rather than simple incised valleys. Seven seismic units were identified: one of Tertiary age (U-1), four of Pleistocene age (U-2-U-5) which are interpreted as 4th-order sequences deposited between MIS 11 and MIS 2, and Late Pleistocene (U-6) and Holocene (U-7) units corresponding with post-glacial sedimentation. The sedimentary infill overlies a highly faulted irregular granitic and metamorphic basement; the inherited morphology is shown to be important for controlling the pathway and evolution of the fluvial network as well as preservation of the sedimentary deposits during several glacial/interglacial cycles. The presence of a rocky barrier at the mouth of the ria is a distinctive feature that conditions sedimentation and exchange of sediment between the ria and the adjacent shelf. For the first time, faults and tilted blocks affecting Late Pleistocene (MIS 3) deposits have been identified. The new data presented here provide the opportunity to reconstruct the evolution of the sedimentary infill of a ria, with especially high-resolution during the last post-glacial transgression. (C) 2017 Elsevier Ltd. All rights reserved.