Reconstructions of the Mediterranean Outflow Water during the quaternary based on the study of changes in buried mounded drift stacking pattern in the Gulf of Cadiz |
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| Authors: | Estefania Llave Francisco J Hernández-Molina Dorrik A V Stow Mari Carmen Fernández-Puga Margarita García Juan T Vázquez Adolfo Maestro Luis Somoza Victor Díaz del Río |
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| Institution: | 1.Instituto Geológico y Minero de Espa?a,Madrid,Spain;2.Instituto Geológico y Minero de Espa?a, Servicio de Geología Marina,Tres Cantos,Spain;3.Facultad de Ciencias del Mar,Universidad de Vigo,Vigo,Spain;4.National Oceanography Centre, Southampton (NOCS),Southampton,UK;5.Instituto Espa?ol de Oceanografía,Fuengirola,Spain;6.Instituto de Ciencias del Mar, CSIC,Barcelona,Spain;7.Facultad de Ciencias del Mar,Universidad de Cádiz,Puerto Real,Spain |
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| Abstract: | Contourite deposits in the central sector of the middle slope of the Gulf of Cadiz have been studied using a comprehensive
acoustic, seismic and core database. Buried, mounded, elongated and separated drifts developed under the influence of the
lower core of the Mediterranean Outflow Water are preserved in the sedimentary record. These are characterised by depositional
features in an area where strong tectonic and erosive processes are now dominant. The general stacking pattern of the depositional
system is mainly influenced by climatic changes through the Quaternary, whereas changes in the depositional style observed
in two, buried, mounded drifts, the Guadalquivir and Huelva Drifts, are evidence of a tectonic control. In the western Guadalquivir
Drift, the onset of the sheeted drift construction (aggrading QII unit) above a mounded drift (prograding QI unit) resulted
from a new Lower Mediterranean Core Water hydrodynamic regime. This change is correlated with a tectonic event coeval with
the Mid Pleistocene Revolution (MPR) discontinuity that produced new irregularities of the seafloor during the Mid- to Late-Pleistocene.
Changes in the Huelva Drift from a mounded to a sheeted drift geometry during the Late-Pleistocene, and from a prograding
drift (QI and most part of QII) to an aggrading one (upper seismic unit of QII), highlight a new change in oceanographic conditions.
This depositional and then oceanographic change is associated with a tectonic event, coeval with the Marine Isotope Stage
(MIS) 6 discontinuity, in which a redistribution of the diapiric ridges led to the development of new local gateways, three
principal branches of the Mediterranean Lower Core Water, and associated contourite channels. As a result, these buried contourite
drifts hold a key palaeoceanographic record of the evolution of Mediterranean Lower Core Water, influenced by both neotectonic
activity and climatic changes during the Quaternary. This study is an example of how contourite deposits and erosive elements
in the marine environment can provide evidence for the reconstruction of palaeoceanographic and recent tectonic changes. |
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| Keywords: | Contourite deposits Gulf of Cadiz Mediterranean Outflow Water Quaternary Seismic stratigraphy Neotectonics Diapirism Palaeoceanography |
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