Datos geofísicos y evolución sedimentaria de la Depresión de la Janda (Cádiz)
- Luque Ripoll, Luis de
- Silva Barroso, Pablo G.
- Zazo, Caridad
- Recio Espejo, José Manuel
- Carrasco García, Pedro
- Goy Goy, José Luis
- Dueñas López, Manuel Angel
- Lario, Javier
- Dabrio González, Cristino José
- González Hernández, Francisco Miguel
- Poza, L.
ISSN: 0213-683X
Argitalpen urtea: 2000
Zenbakia: 29
Orrialdeak: 69-72
Mota: Artikulua
Beste argitalpen batzuk: Geogaceta
Laburpena
La Janda lake is located ¡rito a tectonic graben filled by Pleistocene and Holocene fluvio-marine sediments. Geophysical survey consisting on Electric-logs 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, 67, B2, characterised by resistivity differences. The shallow 4-6 m thick Unit A consists of a thin lacustrine and alluvial day 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 87 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