Stratigraphic analyses of late-quaternary sediments from S’Albufera, North East Mallorca, Spain

Abstract

1. Much of the environmental history of the western Mediterranean has been inferred from records obtained throughout a wider region. Very little work has been conducted on Mallorca. Sediments suited to palaeoenvironmental studies are of limited extent within the Balearic Islands, principally as a result of climatic factors. Stratigraphic cores were collected from two sites (Es Colombar, Amarador) on S'Albufera marsh, Mallorca, in the hope that the sedimentary records could provide source material for interpreting environmental history. In order to develop an understanding of past environmental conditions at S'Albufera, and to asses the potential for future studies of this nature, lithological, geochemical and micropalaeontological (pollen and foraminifera) analyses were conducted upon the sediments. Pollen data were explored using the constrained incremental sum of squares (CONISS) multivariate technique. Through these investigations, an understanding of the geomorphological and vegetation history of S'Albufera has been achieved. 3. All data suggest that S'Albufera was a saline lagoon system throughout the period reflected in these sediments. Progressive sea level rise facilitated an areal expansion of this lagoon. Periods of reduced mean water level have also been identified, one of which was initiated in 1856 during drainage of the lagoon, and is still apparent today. In the absence of absolute dates, it is proposed that earlier phases of lower mean water level occurred during the historical period, in response to the influence of anthropogenic disturbance, eustatic flux or climatic shifts. A relative chronology has been inferred from Corylus pollen data. Amarador is believed to have been a lagoon since ca. 8000 yr. B P., whilst Es Colombar became inundated ca. 3000 yr. B P.4. Pollen assemblages suggest the vegetation of S'Albufera has varied little throughout the lagoonal period. Local vegetation, dominated by salt-tolerant, semi-aquatic Chenopodiaceae and Gramineae, has only grown at the coring sites during periods of reduced mean water levels. At other times local pollen contributions were derived from marsh vegetation at the lagoon periphery. Regional pollen signals are dominated by arboreal inputs e.g. Pinus and Quercus. Regional trends are obscured by low pollen sums and aquatic deposition, which affords highly-mixed assemblages.5. As a relatively undisturbed sedimentary environment, S'Albufera displays great potential as a site for palaeoenvironmental reconstruction work. The nature of the deposits exerts some influence over the suitability of some lines of investigation, pollen included. It is proposed that maximum gains from future studies would be derived from the study of other assemblages, such as ostracods, diatoms and charophytes. All of these groups are believed to be well-represented within the sedimentary record.