Paleo-sandblows and Their Represented Paleoseismic Events in the Taoyuan Basin, Yunnan Province
Based on the results of field geological surveys and stratigraphic dating data, the paleo-sandblows and their represented paleoseismic events developed in the upper strata of the Taoyuan Basin were analyzed. More than ten paleo-sandblow traces were outcropped in the 7-km-range from Taoyuan to Xialinong region in the Taoyuan Basin. The sandblows and their deposits are featured by mushroom-shape, umbrella-shape, sac-shape and skewed cup shape. Their large scale and wide distribution indicated that there was a strong sandblow eruption events related to paleoearthquake. The width of sandflow depositsis several meters, and the thickness is tens of centimeters to one meter. The largest one is 8 meters wide, and 1-1.5 m in the thickness. It is common to observe 1.0-4.5 m long, 0.25-0.35 m in diameter, and 0.8 m in width sand veins. The paleosol layer with good continuity is generally developed at the depth of 1.5-3.0 m below the ground, which is the ground surface at that time. These sand veins and sandflow deposits are generally developed above and below this layer. According to the 14C dating results of the top of the paleosol layer and the bottom of the overlying strata of the sandflow deposits, it is speculated that the time of the paleoseismic event forming the sandblows is 13030±40-12120±40 aBP, and its magnitude is at least greater than 7. The Chenghai-Binchuan fault was a strong active fault in the late Quaternary period, which triggered this Taoyuan earthquake.
万方数据
维普
