Hain, M., Strecker, M.R., Bookhagen, B., Alonso, R.N., Pingel, H. and ...

TC2006
HAIN ET AL.: SALTA FORELAND FRAGMENTATION
TC2006
Figure 3. Compilation of Neogene stratigraphy and chronologic constraints for the three principle intermontane
basins east of the Puna margin. The thicknesses of the formations are not shown to scale as they
have been aligned to a generic time scale that also corresponds to megasequences II to IV of Starck and
Vergani [1996]. Note that, especially at the Piquete/La Troja contact, diachronous onset of deformation/
syntectonic deposition is implicated. Deposits in the Calchaquí Valley equivalent to the La Troja Formation
have not been investigated herein, but Carrera and Muñoz [2008] and Salfity et al. [2004] reported Quaternary
strata closely associated with neotectonic compressional structures. Compilation based on the following:
a, Marshall et al. [1983]; b, Grier and Dallmeyer [1990]; c, Coutand et al. [2006]; d, M. R. Strecker
(unpublished data, 2001); e, Reynolds et al. [1994]; f, Reynolds et al. [2000]; g, Viramonte et al. [1994]; h,
Viramonte et al. [1984]; i, Malamud et al. [1996]; j, Galli et al. [1996]; k, Grier [1990]; l, Vergani and
Starck [1988]; m, Gebhard et al. [1974]; n, Gonzalez Villa [2002]; x, this study.
Quaternary deposits [Hain, 2008] and suggest the adoption
of the name “La Troja Formation.”
3. Methods
3.1. U‐Pb and U‐Th Zircon Geochronology
[19] It is important for our assessment of the stratigraphic
record of the poorly exposed, heavily vegetated eastern
sector of the Salta foreland that we assign our observations
to the correct formations. For this reason we radiometrically
dated zircons from five volcanic ash samples, one pertaining
to the inferred megafan deposit (Guanaco Formation) and
four pertaining to the sediments deposited during and after
the latest stage of intrabasin deformation (La Troja Formation;
sample sites marked as yellow stars in Figure 2b). U‐Pb
and U‐Th zircon ages were obtained using the CAMECA
IMS 1270 ion microprobe at UCLA (Tables 1 and 2). Instrument
setup and relative sensitivity calibrations for U‐Pb
and U‐Th analysis are described by Grove et al. [2003] and
Schmitt et al. [2006]. U‐Pb age uncertainties estimated from
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