Figure 1.

Stratigraphic profile of the west end of the Gran Barranca, south of Lake Colhué-Huapí, Chubut Province, Argentina, indicating MZ levels, lithostratigraphy, stratigraphic nomenclature (7, 8), dated levels, magnetostratigraphy, Simpson’s informal stratigraphic terminology, and the Barrancan faunal zone. The profile on which the figure is based is 0.5 km east of Cifelli’s (9) Section I. MZ levels sampled for magnetic polarity stratigraphy, radioisotopic dating, lithostratigraphy, and phytolith stratigraphy. Radioisotopic dates are from this paper and refs. 11, 12, and 44. ⁴⁰Ar/³⁹Ar and ⁴⁰K–⁴⁰Ar dates are given in Ma.