Archaeologists have unearthed thousands of stone implements dating back about 40,000 to 70,000 years in north China\'s Inner Mongolia Autonomous Region, sources said Thursday. Archaeologists from the Chinese Academy of Sciences and the Erdos Bronzeware Museum started excavating an area in the basin of the Ulan Mulun River in April, discovering more than 4,200 stone implements, including stone flakes, saw-shaped tools and remnant stones, according to Hou Yamei, the leader of the excavation team. The river is a seasonal river near the city of Erdos and is believed to have been a primary location for stone tool production in ancient times, Hou said. The large number of relics uncovered near the river proves that the region was a main living area for people living during the Stone Age, Hou said. About 3,400 animal fossils have also been discovered in the area, with experts concluding that the animals lived in nearby grasslands. The discovery of the tools and subsequent research will help to shed light on the study of Stone Age culture, Hou said.