Formation and evolution of back‐barrier perched lakes in rocky coasts: An example of a Holocene system in north‐west Spain

Abstract

Coastal back‐barrier perched lakes are freshwater bodies that are elevated over sea‐level and are not directly subjected to the inflow of seawater. This study provides a detailed reconstruction of the Doniños back‐barrier perched lake that developed at the end of a small river valley in the rocky coast of the north‐west Iberian Peninsula during the Holocene transgression. Its sequence stratigraphy was reconstructed based on a core transect across the system, the analyses of its lithofacies and microfossil assemblages, and a high‐resolution radiocarbon‐based chronology. The Doniños perched lake was formed ca 4·5 ka bp. The setting of the perched lake was favoured by Late Holocene sea‐level stabilization and the formation of a barrier and back‐barrier basin, which was contemporaneous with the high systems tract period. This basin developed over marine and lagoonal sediments deposited between 10·2 ka bp and 8·0 ka bp, during rapidly rising sea‐level characteristic of the transgressive systems track period. At 1·1 ka bp, the barrier was breached and the perched lake was partially emptied, causing the erosion of the back‐barrier basin sediments and a significant sedimentary hiatus. Both enhanced storminess and human intervention were likely to be responsible for this event. After 1 ka bp, the barrier reclosed and the present‐day lake was reformed, with the water level reaching as high as 5 m above mean sea‐level. The depositional evolution of the Doniños system serves as a model of coastal back‐barrier perched lakes in coastal clastic systems that have developed over gently seaward‐dipping rugged substrates at small distances from the shoreline and under conditions of rising sea‐level and high sediment supply. A review of estuaries, back‐barrier lagoons, pocket beaches and back‐barrier perched lakes in the rocky coast of north‐west Spain shows that the elevation of the bedrock is the main factor controlling the origin and evolution of these systems.

Mixed siliciclastic–carbonate sedimentation in an evolving epicontinental sea: Aptian record of marginal marine settings in the interior basins of north‐eastern Brazil

“…This facies association is interpreted to have been deposited in a perched ( sensu Sáez et al ., 2018) coastal hypersaline lacustrine system. Different from the lower lacustrine system (FA‐4), this lake had a typical shallowing‐upward pattern, suggesting a progradational architecture.…”

Contribution of GIS and Geochemical Proxies to Improving Habitat Identification and Delimitation for the Natura 2000 Network: The Case of Coastal Lagoons in Galicia (NW Iberian Peninsula)

“…Galicia (NW Iberian Peninsula) has numerous coastal lakes of various sizes, forms, and hydrodynamics (see, for example: [15][16][17][18]). This study focuses on four coastal lakes (Figure 1) with different morphological and hydrodynamics characteristics.…”

Trends in the Recent Evolution of Coastal Lagoons and Lakes in Galicia (NW Iberian Peninsula)

“…The Xuño lagoon, with a 5.28 m elevation asl, is smaller in size and is located on the limit of the dune system associated with the Areas Longas beach (Porto do Son, A Coruña). It can be classified within the type known as cat's eye ponds due to its small size and lenticular shape; alternatively, it could also be classified as a coastal back-barrier perched lake [15]. Its elevation is higher than in the case of the other lagoons and, therefore, seawater never reaches it.…”

“…However, this is not an isolated case. Other lagoons in the Atlantic coast of the Iberian Peninsula, such as the Doniños and Traba lakes (both included in the Spanish Natura 2000 network), were also classified as coastal lagoons, but have recently been considered as coastal back-barrier perched lakes [15,24]. This typology is defined as freshwater bodies that are elevated over sea-level and are not directly subjected to the inflow of seawater, a definition that fits the characteristics of the Xuño lake.…”

“…Ultimately, lagoon classification is not always easy and clear, and neither is their categorization as listed in Annex I of the Habitats Directive, which mixed multidisciplinary information and used various environmental proxies in the majority of cases (see e.g., [15,24,25]).…”