Search

The aim of this paper is to evaluate the position of the Holocene transgression on the coast of the Valencia Gulf. To achieve this goal, a sedimentological and micropaleontological analysis of samples of fossil benthic foraminifera in cores from six boreholes drilled in three different wetlands (Almenara marsh, Moro marsh and Valencia lagoon) was carried out. In order to assess the extent of sea level change, at least three factors must be taken into account: 1) eustatic rise (global scale) 2) neotectonics (regional scale) and 3) the sedimentary factor (local and regional scale). Regarding the first factor, some authors have noted that the Holocene transgression reached +1 m above the current sea level in this area. As for the second factor, while the Valencia lagoon is located on a subsiding coast the northernmost marshes are located on a tectonically stable coast. Finally, sedimentation rates are highly variable depending on the area; whereas in the Valencia lagoon the shoreline generally shifts seawards (progradation) in the northernmost areas the coast is currently undergoing retrogradation, although the anthropic factor clearly interferes with this pattern. One of the main conclusions is that in the Valencian coast the Holocene maximum relative sea level did not exceed the present-day one, except in the case of the subsiding area of the Valencia lagoon. The calculation of sedimentation rates, the relative sea-level curve and the evolution of the water column in the different wetlands seem to corroborate it. Radiocarbon and AAR analyses allowed us to date the maximum extent of the Holocene transgression on the Valencian coast at around 5500 cal yr BP in all cases. Despite the different subsidence the three studied wetlands reflected the predominant marine influence until 5500–5200 BP, which was later followed by a growing fluvial or continental incidence, when glacioeustatic adjustments defined the patterns of coastal progradation. [Display omitted] • Location of the MIS 1 coastline position in three West Mediterranean wetlands. • The global Holocene eustatic rise invaded the three wetlands at least 5300 years BP. • Subsidence rate determined different MIS 1 relative sea-level rise in the wetlands. • Tectonic stability in the northern wetlands involved slower relative sea-level rise. [ABSTRACT FROM AUTHOR]

• A multi-proxy approach of late Holocene evolution from Valencia lagoon is presented. • A transition from coastal to fluvial processes shapes the lagoon morphology. • Between 2.8 and 1.2 ka, cold event is registered as a decline in marine influence. • A brackish marsh around 1.2 ka is contemporary with Medieval Climate Optimum. • In the last 0.8 ka, increased fluvial activity in the Little Ice Age is recorded. This study reconstructs the evolution of foraminiferal assemblages and the environmental variables (type of substrate, content in calcium carbonate and content in organic matter) in the Valencia lagoon (western Mediterranean) in response to changes in the late Holocene. In this area of low tidal range, several multiproxy analyses were carried out to determine which environmental variables influence the distribution of the fossil assemblage, and its association with global, regional or local climatic phenomena. The statistical results show that in environments with higher exposure to marine conditions, the calcium carbonate content is the dominant factor, whereas in more restricted environments the type of substrate (grain size) is determinant. The micropaleontological content reveals the evolution from a saline paleoenvironment with a clear marine influence towards the hyposaline or freshwater conditions, recorded at the top. Three phases were identified in the evolution of this area from 2800 cal yr BP to the present. A brackish lagoon with marine connection at the base, followed by a deposit of brackish lagoon (1232 ± 74 cal yr BP − 791 ± 104 cal yr BP), culminating in a brackish marsh (791 ± 104 cal yr BP to present), interpreted as the definitive closure process of the lagoon, favored by the coastal progradation processes related with an extraordinary input of sediments. These findings reflect the climatic variability of the Medieval Climate Optimum (MCO) (1.05 and 0.65 kcal BP) and the migration of the river Turia mouth, which favored the coastal progradation processes. The flood events registered at this phase, may have coincided with changes in the landscape and greater anthropic influence at the end of the LIA, 150 cal yr BP. Coastal processes are mainly responsible for the evolution of this area during phase I, while the influence of fluvial processes is significant towards the top, especially in phase III. [ABSTRACT FROM AUTHOR]