New suborder of bryozoans: Order Cryptostomata (late Paleozoic) |
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| Abstract: | Bauxite occurrences of the Lower Cambrian carbonate complexes have been reviewed for the first time. Five Lower Cambrian bauxite shows have been geologically defined: in the southwestern part of Gornaya Shoriya, in Salair, and in the Kuznets Alatau. The distribution of the bauxite-bearing horizons in the stratigraphic range from the base of the Aldan stage to the top of the Lena stage has been faunally defined; the most significant of them (the Kayashkan show) lies on the boundary between the stages. Most of the bauxite shows display a number of common features of ore localization: association with thick (500–1500 m) sequences of arch aeocyathid-algal limestones of coastal-marine facias, a repetition of manifestation of bauxite-bearing horizons in the section of the surrounding carbonates, and geologic environments that controlled the juxtaposition in plan of the productive carbonate sequences and the outcrops of the earlier. often volcanogenle, aluminosilicate rocks, which could be formed during the bauxite-ore epochs of the source of supply of aluminum. Allites, slallites, and low-module bauxites predominate in the shows. Indirect features of bauxite occurrence in poorly outcropping regions are: the presence of dissemination halos of diaspore and fragments of brown ironstone (varieties of ferruginous bauxites) in the friable cover above the bauxites. A number of promising areas in the Kuznets Alatau, Gornaya Shoriya, Salair, and the Altay have been recommended for reconnaissance exploration of the Lower Cambrian bauxites.—Author |
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