Volcanic activity of the North-Western Tian-Shian
Abstract
As a petrologist of the geological expedition of the Central Asian Geological Administration, the author studied the Kirghiz and Talas Ala‑Tau ranges from the meridian of the village of Dmitrievskoye in the west (72°15′ east longitude from Greenwich) to the meridian of 73°45′ in the east. The region of the Kirghiz and Talas Ala‑Tau mountain ranges from the meridian 72°15′ east longitude from Greenwich in the west to the meridian 73°45′ in the east consists chiefly of various Proterozoic and Lower Paleozoic metamorphic shales, quartzites and marble limestones. Less developed are the Lower Silurian limestones and the so‑called “Toluk” tuffaceous‑limestone sequence of the Lower and partly Upper Silurian. The enumerated sequences are intensely dislocated and cut by enormous granite, diorite and other intrusions. On the above‑mentioned rocks, unconformably with them, lies the Lower Carboniferous sequence of red‑colored sandstones and conglomerates, containing in its lower part a limestone bed 70–500 m thick with abundant fauna. Above this lies the red‑colored sequence of arkose and tuffaceous sandstones and conglomerates — the so‑called “Aramin” sequence. All the above‑mentioned sequences are covered, unconformably with them, by Tertiary variegated formations.
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