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The Ordos Block is located northeast of the Tibetan Plateau (Figure 1a; Deng et al., 1999). Since the Cenozoic, due to the rapid expansion of the Tibetan Plateau to the northeast (Gaudemer et al., 1995;Tapponnier et al., 1982Tapponnier et al., , 1986 and subduction of the Pacific plate to the west (Northrup et al., 1995;Uyeda & Kanamori, 1979), at least four M ≥ 8 large earthquakes have been triggered in the basin on the periphery of the Ordos Block. These earthquakes were the 1303 Hongdong M 8.0 earthquake in the Shanxi Basin in the eastern block

The calcium carbonate coats on stones developed in soil on the geomorphic surfaces of coarse clastic sediments in arid-semiarid regions contain evident information of age. The thickness of coats can be used not only as a good age indicator for the geomorphic surfaces but also coats themselves can be directly used as dating materials in the ESR method. Through measuring the thickness of carbonate coats on stones in soils on the alluvial terraces in the mouth of the Heishanxia gorge of the Yellow River and ESR dating of layers separated from the carbonate coats, the average of accumulation rates of the thickness of carbonate coats on stones since 1.57 Ma was calculated to be 0.10 mm/ka in the studied area, and a regression equation between carbonate coat thickness and age was also generated. From these research results, ages of T2-T11 terraces of the Yellow River in the studied area were systematically determined, and their values are in tum 18 ka, 94 ka, 139 ka, 215 ka, 305 ka, 410 ka, 495 ka, 742 ka, 1072 ka and 1570 ka. The reliability of all these age data is confirmed by the obtained 14C, OSL ages (T 2 , T 3 and T 4 ) and ESR ages of neighbor terraces, and they are completely consistent with the geological epochs estimated by geological and geomorphologic comparison and analysis.

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