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Datos geofísicos y evolución sedimentaria de la Depresión de la Janda (Cádiz)

Luque, Luis de and Silva, P.G. and Zazo Cardeña , Caridad and Recio, J.M. and Carrasco, P. and Goy Goy, José Luis and Dueñas, M.I. and Lario, Javier and Dabrio, Cristino J. and González Hernández, F.M. and Poza, L. (2001) Datos geofísicos y evolución sedimentaria de la Depresión de la Janda (Cádiz). Geogaceta, 29 . pp. 69-72. ISSN 0213-683X

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Abstract

La Janda lake is located into a tectonic graben filled by Pleistocene and Holocene f1uvio-marine sediments.
Geophysical survey consisting on Electric-Iogs and seismic refraction profiles aimed to determining the
thickness of Quaternary sediments infilling the graben. Nevertheless, the results are significantly distorted
by a saline aquifer that occupies most of the sedimentary filling. In any case it is possible to identify an
assymetric subsident area reaching up to 300 m depth, characterised by very low apparent resistivities
(1.5-2.4 W/m). This thick geoelectrical unit can be preliminary subdivided into 3 different subunits here
called A, B 1, B2, characterised by resistivity differences. The shallow 4-6 m thick Unit A consists of a thin
lacustrine and alluvial e/ay and silts of Holocene age easily recognized in seismic refraction profiles and
drill cores. Unit B can be separated in two subunits; Both are saturated in brackish or saline waters; B1 is
a 20-40 m thick unit that thins northward and correspond to the Plio-Pleistocene, B2 is a slightly more
resistive unit that extends from this depth to 352 m and corresponds to deeply weathered mio-pliocene
sandstones. The upper part of Sub-unit B1 correspond to estuarine sands recorded in a previous core
which deposition finishes at ca. 3810 cal BP. A sharp normal fault limits the southern part of La Janda
assymetric graben.

Item Type:Article
Uncontrolled Keywords:La Janda Graben, Geophysical data, Quaternary sedimentation
Subjects:Sciences > Geology > Stratigraphic geology
ID Code:10942
Deposited On:30 Jun 2010 07:58
Last Modified:31 Aug 2010 08:11

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