Open AccessStrategies for successful U‐Th dating of paleolake carbonates: An example from the Bolivian Altiplano
Author(s) -
Placzek Christa,
Patchett P. Jonathan,
Quade Jay,
Wagner Jennifer D. M.
Publication year - 2006
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2005gc001157
Subject(s) - geology , carbonate , petrography , tufa , isochron , siliciclastic , geochemistry , silicic , mineralogy , paleontology , sedimentary depositional environment , basalt , materials science , structural basin , metallurgy
We report over 90 U‐Th dates from carbonates deposited around paleolakes on the Bolivian Altiplano. Petrographic and chemical data for tufas and the siliciclastic detritus contained within them allow (1) assessment of possible diagenetic effects, (2) a development of a strategy for selection of carbonate samples with low initial Th contents, and (3) assessment of the uncertainty due to initial Th. This strategy allows us to produce precise U‐Th dates from lacustrine carbonates. The principal consideration in dating such carbonates is the composition and quantity of initial Th incorporated into the carbonate, and additional uncertainty is introduced because this initial Th may have two sources in lacustrine deposits. Isochron plots, measured ( 230 Th/ 232 Th), and X‐ray diffraction and trace element chemistry of silicic residues all favor regional soil and dust as the sole source of initial Th in carbonates from the Bolivian Altiplano, a situation that simplifies single‐sample dating of Altiplano carbonates.