INVESTIGADORES
RABASSA Jorge Oscar
capítulos de libros
Título:
Middle Pleistocene Glaciations in the Southern Hemisphere.
Autor/es:
A. CORONATO; RABASSA, J
Libro:
The Encyclopedia of Quaternary Science
Editorial:
ELSEVIER SCIENCE BV
Referencias:
Lugar: Amsterdam; Año: 2013; p. 187 - 190
Resumen:
Introduction
Middle Pleistocene glaciations are understood to be one of the
consequences of climatic cooling forced by solar radiation
variation during the 100-ka period cycles driven by Earth?s
orbit eccentricity.
The marine isotope stage (MIS) curves reflect high frequency
and intensive periods of low d18O since 0.88 Ma (MIS
22) and throughout the subsequent Brunhes Normal magnetic
polarity chron. According to Ehlers and Gibbard (2007), MIS
22 is the first of the colder events in which critical d18O values
(5.55%) were reached, which allowed continental ice cap
formation in mid-latitudes, thus defining the critical conditions
during the following middle Pleistocene times. This
time spans the period between 780 ka, when the magnetic
polarity changed from reverse to normal, and 130 ka, when
the last interglacial period began.
Although there are fewer land masses in the Southern
Hemisphere in comparison to the Northern Hemisphere,
evidence for the middle Pleistocene glaciations has been recognized,
mostly through geomorphological mapping and cosmogenic
exposure dating. The latter uses 10Be, 26Al, and 36Cl,
as well as 39Ar?40Ar incremental heating techniques on basaltic
rocks related to till units. The dates obtained have been correlated
with the d18O MIS or with Antarctic temperature curves,
depending on the author?s decisions. This work shows how the
cosmogenic and 39Ar?40Ar dates presented herein correspond
to the cold periods in the MIS curve produced by Lisiecki
and Raymo (2005), in which the benthic d18O records of
57 globally distributed sites were averaged.
Knowledge of these glaciations has been improved by
recent work in the Central Andes (Bolivia and Peru), as well
as on the eastern slope of the Southern Andes (Patagonia,
Argentina), in the New Zealand Alps, and in the western ranges
of Tasmania. As this contribution is an updated review of
Coronato and Rabassa (2007), only post-2005 findings and
the literature not previously considered is presented herein. For
previous work and other references, the reader should consult
the authors? article in the first edition of the Encyclopedia of
Quaternary Science.