Coastal barriers and transgressive dune fields fronting perched lakes: The Northwest Iberia case study

Rocky and indented coasts host a large number of sedimentary features that typically develop associated with the irregular nature of these coasts, such as small perched lakes and bay-mouth or mid-bay barriers. Besides, the position of these basins relative to mean sea level and the occurrence of infilling transgressive aeolian deposits favor the preservation of valuable sedimentary archives that may contribute to reconstructing the coast evolution over the past, as well as to seed some light over changing regional wind field or storminess regimes. Here, two examples of coastal barriers and transgressive dune fields fronting perched lakes (Traba and Doniños, Galicia, NW Iberia), are investigated to decipher the main processes controlling their evolution. For that, Ground Penetrating Radar and borehole transects were collected to characterize the sedimentary architecture of both systems. Selected samples were dated using both accelerated mass spectrometry radiocarbon and optically stimulated luminescence dating techniques. Five dominant radar facies (Rf) and four radar surfaces (Rs) were identified within the radargrams. The identified Rf fall into two groups: (i) inclined reflections and (ii) horizontal to subhorizontal reflections. These Rf are interpreted as transgressive dunes (Rf-1), foredunes (Rf-2), channel infilling (Rf-3), scour and fill structures (Rf-4) and aeolian dune deposits with vertical aggradation or lateral accretion (Rf-5). The identified Rs are grouped into two main types: (i) erosive surfaces and (ii) boundary surfaces. Rs are interpreted as dune scarps (Rs-1), incised channels (Rs-2), water-table (Rs-3) and centimeter-thick layers of organic-rich sediments (Rs-4). A preliminary conceptual model is suggested to explain their onset and evolution, integrating all available information from both sites. The onset of the system is marked by the anchoring of the barriers ca. 4000 BC and the subsequent formation of a dune field through the inland migrat