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| Birth, Evolution and Death of a Lagoon: Late Pleistocene to Holocene Palaeoenvironmental Reconstruction of the Doñana National Park (SW Spain) |
$100.00 |
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Authors: (F. Ruiz, M. Pozo, M.I. Carretero, M. Abad, M.L. González-Regalado, J.M. Muñoz, J. Rodríguez-Vidal, L.M. Cáceres, J.G. Pendón, M.I. Prudêncio, M.I. Dias, Departamento de Geodinámica y Paleontología, Universidad de Huelva, Huelva, Spain, and others)
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Abstract:
A multidisciplinary study of sediment cores from Doñana National Park (SW Spain), a broad region of wetlands in SW Spain, provides the base for the reconstruction of the main palaeoenvironmental changes that occurred in the Guadalquivir estuary since OIS 3. The facies analysis differentiates six main facies, deposited in freshwater pond and marsh (FA-1: laminated silt), brackish marsh or the periphery of a brackish lagoon (FA-2: greyish silt), a shallow lagoon (FA-3: green silt and clay), the marine connection of this lagoon (FA-4: yellow silt) or sandy spit (FA-6: yellow sand), whereas FA-5 includes bioclastic silt and sand with a tsunamigenic origin.
The vertical arrangement of these facies, their dates and a detailed comparison with previous works permit to delimitate ten phases in the Late Pleistocene to Holocene evolution of this lowland. In the oldest phase (OIS 3), this area was occupied by freshwater marshes. Phase 2 (OIS 2) was characterized by the alternation of freshwater and brackish marshes, partly enclosed by aeolian units. During the third phase (Early Holocene), the brackish marshes constituted the northern limit of a broad lagoon that extended along the present-day inner shelf. The sea-level highstand of the Present Interglacial (Flandrian transgression, phase 4: ~6.5 cal BP) caused the inundation of this area, occupied by an open lagoon. Between 6.5 and 4.6 cal ka (phase 5), incipient brackish marshes emerged along the margins of this lagoon and a first tsunamigenic event (5100-4800 cal BP) eroded partially the Doñana spit. The following phase (4.6-3.7 cal ka) was relatively quiet, with predominance of infilling processes. This calm scenario was interrupted by a new period of instability (phase 7: 3.7-3 cal ka), with two new high-energy events. The progressive infilling is the main feature of phase 8 (3-2.2 cal ka), with the emersion of new brackish marshes and a decreasing depth in the adjacent lagoon. The first historical tsunamis (phase 9: 2.2-1.9 cal ka) induced the creation of washover fans and bioclastic ridges overlying the previous marshes. Since 1.9 cal ka (phase 10), the growing of the Doñana spit and the fluvial-tidal sediment inputs caused an important filling of the Guadalquivir estuary (Doñana National Park), only interrupted by new tsunami records (~1.8-1.5 cal ka). |
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