Bao R., Saez A., Servant Vildary Simone, Cabrera L. (1999). Lake-level and salinity reconstruction from diatom analyses in Quillagua formation (late Neogene, Central Andean forearc, Northern Chile). Palaeogeography, Palaeoclimatology, Palaeoecology, 153, p. 309-335. ISSN 0031-0182.
Titre du document
Lake-level and salinity reconstruction from diatom analyses in Quillagua formation (late Neogene, Central Andean forearc, Northern Chile)
Année de publication
1999
Type de document
Article
Auteurs
Bao R., Saez A., Servant Vildary Simone, Cabrera L.
Source
Palaeogeography, Palaeoclimatology, Palaeoecology, 1999,
153, p. 309-335 ISSN 0031-0182
A sedimentary and micropaleontological study of the Quillagua formation provides a detailed paleohydrological reconstruction of the lacustrine system which occupied the present-day hyperarid Quillagua-Llamar fore-arc Basin (Northern Chile) from lattermost Miocene (5.8 plus or minus 0.4 Ma) to Early Pliocene times. Diatom and lithofacies analyses were carried out in two correlated stratigraphic sections of the lacustrine system. The Quebrada Temblor section is located at the southern margin of the ancient lake and is directly influenced by the freshwater inputs of a northward flowing fluvial system draining the Precordillera and Calama regions. The Cerro Mogote section occupies a western marginal location in the northern zone sheltered from direct fluvial inputs from the south but subjected to the activity of the alluvial fan systems of the Coastal Range. A mostly shallow oligosaline waterbody occupied the basin during the interval studied, though with fluctuations in salinity and the extent of the inner, open waters. The southern margin sector - represented by Quebrada Temblor - had, in general terms, a plaustrine oligosaline character with almost freshwater pulses mediated in this case by the activity of the terminal alluvial fan zones. Paleohydrological evolution of the basin was strongly conditioned not only by shifts in the climatic-tectonic system but by variatins in the local hydrological parameters. Four hierarchical orders of variability in the lake level of the basin were distinguished both by stratigraphic analysis of lithofacies and from changes undergone by the diatom record. Strong intrasample mixing of diatoms of incompatible salinity spectra and the presence of fine laminated lacustrine facies in some terms define the highest order short-term intra- or inter-annual pulses experienced by the lacustrine system (higher than 6th order)... (D'après résumé d'auteur)
