Figure 1. Schematic map for the locations of the sections: 1 - cities, 2 - natural outcrops, 3 - boreholes. Cross-sections: (1) Zakharievskii Mine, (2) Polivna Settl., (3) Uliyanovsk City [Baraboshkin et al., 1999], (4) Kremenki Vil. [Baraboshkin et al., 1999], (5) Kremenki Vil., (6) Sengiley Town, (7) Russkaya Bektyashka Vil. (all of the Uliyanovsk region), (8) Novokashpirskii Stl., (9) Forfos Mt. (both (8) and (9) are in the Syzran district of the Samara region), (10) Chernyi Zaton Vil., (11) Fedorov Site, (12) Mark 246 m, (13) Ershov Site (all in the Khvalyn district of the Saratov region), (14) Ust-Kurdyum Vil., (15) Dubki Stl. (both in the Saratov region), (16) Sokolov Mt., Saratov City [Grishanov, 1984], (17) Hole 120 (Pugachev area), (18) Hole 204 (Ozinki area) (both in the Saratov region).