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Depositional history of estuarine infill during the last postglacial transgression (Gulf of Cadiz, Southern Spain)

Dabrio, Cristino J. and Zazo Cardeña , Caridad and Goy Goy, José Luis and Sierro, Francisco Javier and Borja, Francisco and Lario, Javier and González Delgado, José Ángel and Flores Villarejo, José Abel (2000) Depositional history of estuarine infill during the last postglacial transgression (Gulf of Cadiz, Southern Spain). Marine Geology, 162 (2-4). pp. 381-404. ISSN 0025-3227

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Abstract

The Late Pleistocene and Holocene evolution of the estuaries in the Gulf of Cadiz is interpreted for the first time using
drill cores, logs, trenches, and 38 new radiocarbon data, and the results compared with the shelf. The Odiel, Tinto and
Guadalete Rivers deposited conglomerates during a highstand that did not reach the present sea level dated at ca. 25–30 ka
(Isotopic Stage (IS) 3), corresponding to a relatively humid period in the area. Rivers incised these coarse-grained deposits
during the last main lowstand at ca. 18 ka, when sea level dropped to -- 120 m and the coastline lay 14 km seawards from
the present. The erosional surface is a sequence boundary and the flooding surface of the postglacial eustatic rise, overlain
by the valley fill deposits of the transgressive and highstand phases of the last fourth- and fifth-order depositional sequences
recognised in the shelf. The first marine influence in the estuaries during the transgression occurs at -25/-30 m at. ca.
10,000 years BP. According to fossil assemblages, the transgressed basins changed from brackish to more open marine as
the sea rose until ca. 6500 years BP, when it reached the maximum flooding and the sandy estuarine barriers ceased to
retrograde toward the muddy central basins. Then, the rate of eustatic rise decreased drastically, and the estuarine filling
followed a two-fold pattern governed by the progressive change from vertical accretion to lateral (centripetal) progradation.
At ca. 4000 years BP the fluvial input surpassed the already negligible rate of rise, causing partial emergence of tidal flats
and spit barriers in the largely filled estuarine basins. Prevalence of coastal progradation upon vertical accretion at ca. 2400
years BP caused accelerated expansion of tidal flats and rapid growth of the sandy barriers. Further changes since the 16th
century reflect widespread anthropic impacts. q2000 Elsevier Science B.V. All rights reserved.


Item Type:Article
Uncontrolled Keywords:Incised-valley fill; Estuary; Flandrian transgression; Late Pleistocene–Holocene; Radiocarbon data; Coastal evolution
Subjects:Sciences > Geology > Stratigraphic geology
ID Code:11355
Deposited On:20 Oct 2010 11:07
Last Modified:20 Oct 2010 11:07

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