Abstract

R.Ya. Koldysheva and K.A. Chernyavskaya The Upper Chara artesian baSin is located Aldanian (sub-Aldanian) type. The Cenozoic amid the high mountain Kodar and Udokan ridges development stage of the depression, which took within the northeastern part of the Stanovoye up- place under conditions analogous to those of the land. It is named after the Upper Chara depres- Baykal ones, has determined coincidence of both sion, which occupies the central portion of the (4). basin. The depression, with an area of 2,300 km 2 , 130 km long, and 10 to 30 km wide (see figure), In the structure of the mountainous framing has a pronounced assymetric structure: its and bed of the depression are Archean gneisses northwestern slope is much steeper than the and crystalline schists, among which prevail southeastern one. The floor of the depression basic rocks, acid intrusions of different age, lies 610 to 820 m above sea level, and the sur- and also weakly metamorphosed sandstones and rounding high mountains of the Kodar and the shales of the lower Proterozoic Udokan series. Udokan lie 1, 300 to 1, 700 m above it. The basin blanket is composed of Meso-Cenozoic deposits. Middle Jurassic rocks on the Kodar