Abstract The Zaysan Basin of northeastern Kazakhstannorthwestern China (Figure 1) is a collisional successor basin that formed during the Late Cretaceous (Grahamet al., 1993;Allen et al., 1995). Beginning during the late Campanian-Maastrichtian, a lake basin developed in the Zaysan depression and has been there until the present. Lake Zaysan is now one of the large fresh water lakes of central Asia. Located between the Altai and Tarbagatay ranges at an altitude of 386 m, it is fed by the Cherny Irtysh River to the east and historically was about 100km long, 32 km wide, and 8 m deep. Its original surface area of 3200 km", however, was enlarged,and the lake was deepened (to 14 m) in the 1980s when Lake Zaysan became part of Bukhtarma Reservoir to the west. The new water body is 440km long and has a total area of 5504 km". Here, we present a brief overview of the lithostratigraphy, paleontology, and depositional335history of the Zaysan lacustrine basin, the majority of which is located in eastern Kazakhstan (Figure 1).

The first Eocene vertebrate assemblage known from the Great Basin, the Elderberry Canyon Local Fauna, occurs in rocks referred to the Sheep Pass Formation near Ely, Nevada. Approximately 40 taxa are now known, including small anuran amphibians, small reptiles, birds, and mammals. The mammalian component consists of: the insectivorans Apatemys bellus, Pantolestes longicaudus, a tiny apternodont, at least one nyctitheriid, and at least four other taxa representing dormaalid and/or erinaceid erinaceomorphs; an epoicotheriid palaeanodont, cf. Tetrapassalus mckennai; the primates Notharctus tenebrosus, Trogolemur myodes, and two species of uintasoricines; the rodents Reithroparamys delicatissimus, R. cf. R. huerfanensis, Sciuravus sp., Microparamys sp., Pauromys sp., Mattimys sp., and two new genera; the hyaenodont Sinopa minor; two viverravid carnivores including Viverravus; the condylarth Hyopsodus paulus; the perissodactyls Hyrachyus modestus, Hyrachyus affinis, Helaletes nanus, Isectolophus latidens, and a new genus and species; and the artiodactyl Antiacodon pygmaeus. Greatest faunal similarity is with the Black’s Fork Member (or lower), Bridger Formation, and other early Bridgerian localities such as Powder Wash in the Douglas Creek Member of the Green River Formation in northeastern Utah. The age of the Elderberry Canyon Local Fauna can confidently be called early Bridgerian. The Elderberry Canyon Fauna is preserved in carbonate rocks believed to have been deposited in a shallow, warm, heavily vegetated, permanent, hardwater lake. The mammals lived on marshy wetland terrain adjacent to the lake, although some faunal elements may have been transported in from more distant habitats.