Chronology and tectono-sedimentary evolution of the Upper Pliocene to Quaternary deposits of the lower Guadalquivir foreland basin, SW Spain

Abstract

This paper presents new litho, chrono and magnetostratigraphic data from cores of 23 exploratory boreholes drilled in the Abalario and marshlands areas of the lower Guadalquivir basin (the western sector of the Guadalquivir foreland basin, SW of Spain). The lithologic logs of these boreholes identify four main sedimentary formations, namely: Almonte Sands and Gravels, Lebrija Clays and Gravels, Marismas Clays and Abalario Sands, respectively interpreted as proximal-alluvial, distal-alluvial, alluvial-estuarine and aeolian. From radiocarbon and magnetostratigraphic data, these formations were dated as Late Pliocene to Holocene. In the marshlands area, three main sedimentary sequences are present: a Late Pliocene-Early Pleistocene sequence of the Almonte and Lebrija (lower unit) formations, a Late Pleistocene-Early Holocene sequence of the Lebrija (upper unit) and Marismas formations, and a middle Holocene to present-day sequence of the upper Marismas Formation. The three sequences began as a rapid alluvial progradation on a previously eroded surface, and a subsequent alluvial retrogradation. In the third sequence, shallow estuarine and marsh sediments accumulated on top of the alluvial sediments. The aeolian sands of the Abalario topographic high developed coeval to alluvial and estuarine sedimentation after the first alluvial progradation, and continuously until the present. Correlation with the surrounding areas show that the sequences are the result of the forebulge uplift of the northern margin of the basin (Sierra Morena) and the adjacent Neogene oldest sediments of their northern fringe, both form the main source area of the study formations. This uplift occurred simultaneous to the flexural subsidence (SSE tilting) of the southern part of the basin, where sedimentary aggradation dominated.

The role of neo-tectonics in the sedimentary infilling and geomorphological evolution of the Guadalquivir estuary (Gulf of Cadiz, SW Spain) during the Holocene

“…Significant contributions have only been a fragmentary analysis of a long core (Zazo et al, 1999a;Lario et al, 2001;Pozo et al, 2010) and research on the period between the Upper Pliocene and the Quaternary which has failed to concentrate on the evolution during the Holocene (Salvany et al, 2011).…”

“…No remains of macrofauna were encountered. On a regional scale, the sequence has a thickness of as much as 100m (Salvany et al, 2011).…”

“…It is commonly accepted that on the coast of the province of Huelva a number of orthogonal fault systems (following NW-SE, NE-SW and E-W directions) outline individual blocks that control swamped areas and elevated areas (Flores-Hurtado, 1993). The received literature (e. g., Zazo et al, 2005;Salvany et al, 2011) registers no indications that such neotectonics could affect formations that are so recent, however.…”

Sedimentological and geomorphological imprints of Holocene tsunamis in southwestern Spain: An approach to establish the recurrence period

“…3A), with a marine sector constituted by two main channels that separate salt-marsh deposits; (3) the Guadalquivir Estuary ( Fig. 4A), partially closed by two spits (Doñana and La Algaida) that protect the Doñana National Park, a Biosphere Reserve (>50,000 ha) with a sedimentary record from the Lower Pliocene to the Late Holocene (Salvany et al, 2011); and (4) the Guadalete Estuary (Fig. 4F), roughly circular and separated from the sea by a sedimentary spit (Dabrio et al, 2000).…”

Evolución paleoambiental del sector meridional del Parque Nacional de Doñana desde el Plioceno Inferior a la actualidad

“…La mayoría de estas investigaciones se han centrado en los materiales holocenos de este registro, y especialmente aquéllos depositados desde la Transgresión Flandriense, que tuvo lugar en esta área hace unos 6.500 años aproximadamente (Zazo et al, 1994).Recientemente, Salvany et al (2010Salvany et al ( , 2011 han diferenciado las distintas formaciones que componen el relleno del Parque desde el Plioceno Inferior, basán-dose en el estudio de numerosos testigos continuos. En este trabajo, se analizan los ostrácodos de uno de ellos, obtenido en la flecha de Doñana.…”