CIG   05423
CENTRO DE INVESTIGACIONES GEOLOGICAS
Unidad Ejecutora - UE
artículos
Título:
Lateritized tephric palaeosols from Central Patagonia Eocene, Argentina: a southern high-latitude archive of Palaeogene global greenhouse conditions.
Autor/es:
KRAUSE, J.M.; BELLOSI, E; RAIGEMBORN, M.S.
Revista:
SEDIMENTOLOGY
Editorial:
Wiley-Blackwell
Referencias:
Lugar: Oxford, UK; Año: 2010 vol. 57 p. 1721 - 1749
ISSN:
0037-0746
Resumen:
Palaeosols of the Koluel-Kaike Formation, a red colour-banded, pyroclastic
succession from southern Argentina, constitute a proxy for Eocene climate
changes. Reticulated and vertically elongated ferric mottles, along with iron and
manganese nodules are the most significant climate indicators, which
originated by alternating cycles of waterlogging and drying conditions
causing Fe-Mn mobilization and fixation. Clay minerals vary from a
kaolinite > smectite suite in the lower and middle sections, to a
smectite > kaolinite one in the upper part. High concentrations of iron
oxides/hydroxides and kaolinite, lack of exchangeable bases, absence of
carbonate cement, presence of ironstone and redness of hue in most of the
palaeosols suggest intense chemical weathering related to leaching and
lateritization processes. Five pedotypes, ordered in a stratigraphic sense, were
identified. Strongly developed, red to orange Chornk (Fragiaquult) and Ka´penkChornk (Fragiaquult) and Ka´penk
(Plinthaquult) pedotypes display argillic horizons, abundant ferric nodules and
slickensides; they are dominant in the lower and middle sections, and formed in
seasonal humid and megathermic (tropical) conditions with a mean annual
precipitation of 1200 to 1300 mm and a mean annual temperature of 15 C.
Weakly developed, less structured Ornek (Vitrand) and Po´ lnek (Placaquand)
pedotypes occur in the middle and upper sections, and originated in sub-humid
and mesic-megathermic conditions with a mean annual precipitation around
1000 mm and a mean annual temperature around 12 C. The brownish Soorsh
pedotypes occur in the middle and upper sections, and originated in sub-humid
and mesic-megathermic conditions with a mean annual precipitation around
1000 mm and a mean annual temperature around 12 C. The brownish Soorsh
Ornek (Vitrand) and Po´ lnek (Placaquand)
pedotypes occur in the middle and upper sections, and originated in sub-humid
and mesic-megathermic conditions with a mean annual precipitation around
1000 mm and a mean annual temperature around 12 C. The brownish SoorshSoorsh
(Argialboll) pedotype exhibits a granular structure and is present at the
uppermost part of the unit. It developed in sub-humid/semi-arid and mesic
conditions, with a mean annual precipitation of 600 to 700 mm and a mean
annual temperature around 10 C. This pedotype succession and clay mineral
distribution indicates a decrease in chemical weathering and degree of soil
development with time. Koluel-Kaike palaeosols from Central Patagonia are
some of the first continental non-palaeobiological data linked to the Early
Palaeogene global warming in South America; they show an especially close
relationship with the Early Eocene Climatic Optimum and the following longterm
cooling and drying initiated by Middle to Late Eocene time.
Keywords Central Patagonia, Early Palaeogene global warming, EECO,Central Patagonia, Early Palaeogene global warming, EECO,