Palaeoenvironmental evolution from the early Holocene to the present of the Almenara marsh (western Mediterranean)

Abstract

The main aim of this study is to characterize the different stages in the palaeoenvironmental evolution of the Almenara marsh, Spain, from the early Holocene to the present day. This marsh is one of the most important in Castellón province. Five cores extracted from the marsh underwent sedimentological analysis, micropalaeontological study (foraminifera, ostracods and gastropods) and 14C dating. The results show that before the maximum transgression of the Mediterranean during the Marine Isotope Stage 1 (5500 cal yr. BP dating in the Almenara marsh), the area was occupied by a brackish marsh (prior to the 8.2 ka event). During the middle Holocene, the regional sea level rise and later stability caused an oligohaline/freshwater marsh with fluctuating water levels to form. This marsh occupied the entire area of today’s Almenara marsh at least between 7570 and 2780 cal yr BP. The results may indicate a phase of greater contribution of groundwater inputs (and rainfall/riverine discharge) during the middle Holocene as a response to a climatic phase characterized by higher humidity. Today, the marsh is filled with sediments from natural and anthropic processes related to the agricultural activity carried out throughout the area (except for the central part, which has been reclaimed as wetland). The water of the present-day marsh (like that prior to 8.2 ka event) is brackish, as is indicated by the benthic foraminiferal assemblage; this contrasts with the earlier oligohaline/freshwater marsh determined in the survey cores during the middle Holocene until the time of the Iberian culture.

Aridity events during the last 4000 years in Western Mediterranean marshes (Almenara and Benicasim marshes, E Spain)

“…In the Almenara marsh, Blázquez et al (2018) determine that from ca. 4820 yr BP onwards the oligohaline marsh was relatively stable with marine influence.…”

“…For most of the last 4000 years, coastal wetlands have no direct connection to the sea. In the case of the marshes of Almenara and Benicasim, the paleoecological studies (foraminifers and ostracods) show that they were oligohaline marshes only affected by small fluctuations in their water levels (Usera et al, 1996;Mediato, 2016;Blázquez et al, 2017Blázquez et al, , 2018Rodríguez-Pérez et al, 2018). These authors did not reach conclusive paleoecological data that allowed distinguishing relative changes in salinity of wetlands during the period.…”

“…They are typical features of the coastal plain landscapes of the Spanish Mediterranean coast: Mar Menor, Valencia lagoon, Oliva-Pego marsh, Almenara, Benicasim and Torreblanca-Cabanes marshes. Previous sedimentological, geomorphological and paleontological studies focused on their paleoenvironmental reconstruction during the Holocene (Dupré et al, 1988;Usera et al, 1996Usera et al, , 2002Mediato and Santisteban, 2006;Carmona and Ruiz, 2011;Marco-Barba et al, 2013, Carmona et al, 2016Mediato, 2016;Blázquez et al, 2017Blázquez et al, , 2018Rodríguez-Pérez et al, 2018;Ruiz-Pérez and Carmona, 2019;López-Belzunce et al, 2020). These studies concluded that the Holocene paleoenvironmental changes were related to the eustatic variations that took place since the Last Glacial Maximum and climate was a minor forcing of local interest.…”

Natural and anthropic pollution episodes during the Late Holocene evolution of the Tinto River estuary (SW Spain)

“…In the last few decades, numerous investigations have focused on the Holocene paleoenvironmental evolution of coastal areas through multidisciplinary analysis of sediment cores and seismic stratigraphy. In most cases, studying paleoenvironmental evolution involves combining sedimentological, paleontological, geochemical, isotopic and radionuclide techniques (Pascual and Rodríguez Lázaro 2006, Ercilla et al 2010, Blázquez-Morilla et al 2018. These studies are used to determine local geochemical backgrounds, with a subsequent application to detecting environmental pollution episodes caused by mining, industrial waste, urban discharges and agricultural activities (Cearreta et al 2002, Beck et al 2020).…”

Benthic Foraminiferal Salinity index in marginal-marine environments: A case study from the Holocene Guadalquivir estuary, SW Spain

“…Benthic foraminifera are widely used for reconstructing paleoenvironmental changes from marginal-marine to deep-sea environments since they are very sensitive to variations in sea level, organic fluxes, oxygen content, salinity and type of substrate (e.g., Alve and Murray 1999;Jorissen et al 2007;Di Bella et al 2008;Martins et al 2014;Blázquez et al 2017;Pérez-Asensio et al 2014. In coastal settings, it is well known that benthic foraminiferal distribution https://doi.org/10.1016/j.palaeo.2020.110021 Received 3 April 2020; Received in revised form 9 September 2020; Accepted 10 September 2020 and abundance can be influenced by salinity, which is dependent, among other factors, on the geomorphological restriction ; Barbieri and Vaiani 2018;Blázquez-Morilla et al 2019). In fact, benthic foraminifera have been successfully used as proxies of restriction of marginal-marine environments and for developing salinity indices (Debenay 1995;Hayward et al 2004;Debenay and Luan 2006).…”