Abstract

M. Gaetani writes: Every structural analysis of a mountain range should include a careful, up-to-date analysis of the stratigraphic succession involved in the deformation, especially during the construction of balanced structural cross-sections.

One of the three main conclusions of McElroy et al. (1990, p. 996) is that the Karsha Formation should be Late Ordovician-Silurian in age, on the basis of fragmentary brachiopods identified at the family level. However, Whittington (1986) has reported late Mid-Cambrian trilobites above the Karsha Formation in SE Zanskar. Without this information, McElroy et al. were unable to introduce, into the evolutionary scheme of the Himalayan Palaeozoic, the regional unconformity that exists between the Kurgiakh and Thaple Formations. Instead, they postulated an early Devonian rifting phase. Consequently, they considered the Caradoc fossils, found in Spiti at the top of the Thaple Formation by Hayden (1904), as reworked. The comprehensive paper of Garzanti et al. (1986) offers a much more convincing geohistory; it also takes into account the widespread occurrence, in the north Himalaya, of the 500Ma granitoids (Frank et al. 1977; Le Fort et al. 1986). This igneous episode fits well with the stratigraphic age of the unconformity.

Further details are also available concerning the Permian and Jurassic stratigraphy (Jadoul et al. 1985; Gaetani et al. 1990; Garzanti et al. 1989).

Finally, it is suprising that McElroy et al. give credit to Gupta & Shaw (1982), when from April 1989 onwards, several notes were issued in Nature and other journals, dealing with the Gupta affair (e.g. Talent

First Page Preview

First page PDF preview
You do not currently have access to this article.