广州番禺眉山阶地第四系剖面的年代学框架及构造学意义

Chronological framework and tectonic significance of the Quaternary section of the Meishan terrace in Panyu, Guangzhou

眉山阶地第四系剖面地处番禺断隆区的边缘,毗邻狮子洋断陷区,是珠江三角洲第一次海侵所到达的区域,附近的断裂包括文冲断裂、化龙—黄阁断裂、新会—市桥断裂等三角洲内典型断裂。发育于网纹红土基座上的堆积阶地,自下而上大致分为杂色砂层、白色砂层、淤泥质层3层,构成一个完整的从动水环境到静水环境的沉积旋回。野外调查及^(14)C测年和光释光(OSL)测年结果表明,眉山第四系剖面年龄约在70～30 ka B.P.之间,相当于深海O同位素4—2阶段。结合前人的研究资料,认为阶地面与沉降区的下旋回原本在同一高度,但自晚更新世以来,在断块差异升降中被错开,垂直距离在20 m以上,直观地指示了断隆区与断陷区的运动特征。

The Meishan Quaternary depositional terrace section is located at the east edge of Panyu uplift block, adjoining the Shizi-yang subsidence block, where the first transgression of the Pearl River Delta could be reached. This area is confined by the Wenchong Fault, Hualong-Huangge Fault and Xinhui-Shiqiao Fault, which are all typical faults in the Pearl River Delta. This terrace is an accumulation terrace developed on reticulated laterite bedrock, and can be roughly divided into three layers of variegated sand layer, white sand layer and silt layer, which constitute a complete depositional cycle from dynamic river environment to hydrostatic one. Detailed field investigation near the Meishan terrace section and indoor tests suggest that: OSL and 14C dating reveal that the age of the Meishan terrace deposits is about 70-30 ka B.P., which is equivalent to MIS4 to MIS2;Combined with previous research, it is shown that the lower cycle of the terrace and subsidence area was originally at the same height. Since the Late Pleistocene, it has been staggered to a vertical distance of more than 20 m in the differential uplift and subsidence of fault blocks, which directly indicates the dynamic characteristics of fault uplift area and fault subsidence area.