HR: 17:20h
AN: GP24A-05 INVITED     [Abstracts]
TI: ENVIRONMENTAL MAGNETISM STUDIES IN SOUTH AMERICAN SOILS AND PALEOSOLS DEVELOPED IN LOESS AND LOESSIC SEDIMENTS
AU: * Orgeira, M J
EM: orgeira@gl.fcen.uba.ar
AF: Universidad de Buenos Aires- Consejo Nacional de Investigaciones Científicas y Técnicas de Argentina, Instituto de Geofísica y Departamento de Ciencias Geológicas. FCEyN Ciudad Universitaria Pab II., Buenos Aires, 1425, Argentina
AB: A summary of results of magnetic measurements of loess and loessic sediments-paleosol sequences from South America is presented. Most of them were carried out in pampean plain (Argentina). The main objective in the selection of the studied Argentinian units was to cover the widest possible temporal interval. Pure loess deposition was interrupted at the end of the Pleistocene, given place to the deposition of reworked loess mainly due to the fluvial action. Unlike in China, the paleosols are not characterized by a systematic magnetic enhancement. The magnetic mineralogy of Pampean Plain loess reflects its volcanic origin, marked by the abundance of volcanic glass. The magnetic signature of these loesses is dominated by low-Ti titanomagnetites. Finally, according to a comparison of an index of potential water storage (PWS) with the magnetic signal of soils and paleosols from Pampean plain and others regions of the world, the existence of climatic thresholds that affect the forma¬tion, preservation or depletion of ferrimagnetic minerals could be suggested. Soils characterized by a positive PWS (as those studied in pampean plain) are wetted during an important part of the year, creating an appropriate environment that favors the depletion of ferrimagnetic minerals due to mainly reductive dissolution. Such soils are characterized by a depletion of detrital ferrimagnetic minerals.
DE: 1512 Environmental magnetism
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Joint Assembly