iron, as well as large oil fields. Dzungarian Basin The core of Dzungaria is the triangular Dzungarian Basin, also known as Junggar Basin (), with its central Gurbantünggüt Desert. It is bounded by the Tarbagatai Mountains to the northwest, the Altai Mountains to the northeast, and the Tian Shan mountains to the south. The three corners are relatively open. The northern corner is the valley of the upper Irtysh River. The western corner is the Dzungarian Gate, a historically important gateway between Dzungaria and the Kazakh Steppe; presently, a highway and a railway (opened in 1990) run through it, connecting China with Kazakhstan. The eastern corner of the basin leads to Gansu and the rest of China. In the south, an easy pass leads from Ürümqi to the Turfan Depression. In the southwest, the tall Borohoro Mountains branch of the Tian Shan separates the basin from the upper Ili River. The basin is similar to the larger Tarim Basin on the southern side of the Tian Shan Range. Only a gap in the mountains to the north allows moist air masses to provide the basin lands with enough moisture to remain semi-desert rather than becoming a true desert like most of the Tarim Basin and allows a thin layer of vegetation to grow. This is enough to sustain populations of wild camels, jerboas, and other wild species. The Dzungarian Basin is a structural basin with thick sequences of Paleozoic-Pleistocene rocks with large estimated oil reserves. The Gurbantunggut Desert, China's second largest, is in the center of the basin. The Dzungarian basin does not have a single catchment center. The northernmost section of Dzungaria is part of the basin of the Irtysh River, which ultimately drains into the Arctic Ocean. The rest of the region is split into a number of endorheic basins. In particular, south of the Irtysh, the Ulungur River ends up in the (presently) endorheic Lake Ulungur. The Southwestern part of the Dzungarian basin drains into the Aibi Lake. In the west-central part of the region, streams flow into (or toward) a group of endorheic lakes that include Lake Manas and Lake Ailik. During the region's geological past, a much larger lake (the "Old Manas Lake") was located in the area of today's Manas Lake; it was fed not only by the streams that presently flow toward it but also by the Irtysh and Ulungur, which too were