Browsing by Author "Scheneider, Heike"
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- A multi-proxy reconstruction and comparison of Holocene palaeoenvironmental changes of the Alvor and Alcantarilha estuaries (southern Portugal)Publication . Trog, Carmen; Hofer, Dana; Frenzel, Peter; Camacho, Sarita; Scheneider, Heike; Mäusbacher, RolandThe present study investigates the history of two estuaries on the Algarve coast, southern Portugal, through a multi-proxy approach that links sedimentology, geochemistry, palynology, microfaunal analyses and radiocarbon dating. These analyses provide an overview of the development of these estuaries over the last ∼7500 years. Palynological data reveal climate-driven vegetational shifts over the whole period. Microfauna, which is composed predominantly of foraminifers and ostracods, provides evidence for periods of marine and brackish water conditions, observed in both estuaries. Whereas the sediment record from the Alvor estuary shows a clear, nearly continuous silting-up sequence, the development of the Alcantarilha estuary is characterised by fluvial sedimentation, replaced by a marine environment at about 7300 yr calBP. Marine transgression is indicated by marine-brackish foraminifera and ostracod assemblages, while upper-marsh pollen decreased and wetland communities increased at the same time. A continuous shallowing of the estuaries followed between ∼6700 yr calBP and ∼5700 yr calBP in Alvor and 4500 yr calBP in Alcantarilha. This was interrupted by a distinct high-energy event, possibly a storm or tsunami, between 6400 and 5800 yr cal BP in Alvor; the event was not recorded in the Alcantarilha estuary. Afterwards, the silting-up restarted with clear similarities to the pre-event situation and continued until ∼3500/2000 yr calBP. This process wasinfluenced by the build-up ofsand barriersin front of the estuaries. Thisis also documented by a higher percentage of upper-marsh vegetation. The core from Alcantarilha estuary shows another layer of high-energy deposits, with mainly marine foraminifers and ostracods after 4500 yr calBP. The youngest parts of the two records are characterised by decreasing tidal influence and increasing anthropogenic impact, indicated by increasing values of cultivated plants and other human-induced changes of vegetation cover.