PERSONAL DE APOYO
GARCIA Pablo Javier
congresos y reuniones científicas
Título:
X-Ray Diffraction mineral analysis of continental moderm stromatolites from the Socompa Lake, Argentina Puna
Autor/es:
POIRÉ, DANIEL G.; GENAZZINI, CECILIA I.; LOPEZ AGOSTI, VERÓNICA; ARROUY, M. J.; GARCIA, PABLO J.; FARÍAS, M. E.
Reunión:
Congreso; 6th Latin American Congress of Sedimentology; 2013
Resumen:
Stromatolites forming at an altitude of 3570 m at
the shore of a volcanic lake Socompa, Argentinean Andes, have been reported in
the last three years.The water at the site of stromatolites formation is
alkaline, hypersaline, rich in inorganic nutrients, very rich in arsenic, and
warm (20-24 ºC) due to a hydrothermal input. The stromatolites do not lithify,
but form broad, rounded and low-domed bioherms (up to 24x80 cm in size)
dominated by diatom frustules and aragonite micro-crystals agglutinated by
extracellular substances. Neighbouring domes tend to coalesce into bigger domed
biostromes. Vertical sections display visually clear stratification. The
surface continuously exposed to air is covered by a white-pinkish crust,
whereas the surface intermittently exposed to water due to waves is
green-yellow. Below this cover is a 0.5-1.5 mm thick dark-green layer, which
gradually fades away and disappears at depths of 3-5 mm. Deeper parts are
characterized by alternating light-brown (5-20 mm thick) and dark-brown
(0.5-1.5 mm thick) layers. A 91 centimetres core token from the top-surface of
this stromatolites shows e very complete growing record of the stromatolites
layers along the core just interrupted between 9 cm and 26 cm by ash fall
depositation. XRD mineral analyses have allowed recognising aragonite, calcite,
quartz, feldspars and amorphous silica. From the top to the bottom a very clear
trend of the transformation from aragonite to calcite has been recognise. We
are trying to carry out isotopic analyses in order to date this transformation
and also get the stromatolite growing rate.