粤北地区的河流阶地——广东河流阶地研究之三

The River Terraces in North Guangdong

依据粤北至少16条河流、34处河流阶地、30个14C或热释光测龄数据等情况,探讨该区阶地的分布与特征：粤北最多有6级河流阶地,其最大阶地高度60m,低于粤东和粤西5~16m;第一级阶地变形最明显：乐昌峡以上属于常态阶地,乐昌峡以下属于半埋藏阶地;三水以下进入珠江三角洲属于埋藏阶地。第一级阶地冲积物时代为晚更新世至中更新世晚期,最老测龄达TL206.000±13.500kaBP。坪石向下游第一级阶地冲积物的年龄有渐新趋势。坪石第六级阶地与英德宝晶宫储存早更新世信息：该阶地属于早更新世晚期,最老测龄达TL819.000±57.000kaBP,据此计算近百万年来粤北地壳构造抬升速度为0.73m/10ka,由此推算,英德宝晶宫高出北江111m的地下河阶地砾石层年龄为1520kaBP。

In this paper 34 terraces along 16 rivers in north Guangdong and at least 30 data of the 14C and TL ages of their alluvium are studied to understand their distribution and characteristics. There are at most 6 stages of river terraces in the region, of which the highest is 60m, 5~18m lower than that in west and east Guangdong; the deformation of the first stage terraces is the most evident： those at upper Lechang Gorge are normality terraces, at lower Lechang Gorge semi-buried terraces, and those at the reaches below Sanshui, which are parts of the Pearl River Delta, are buried terraces. The first stage terraces formed in the period from Late Pleistocence to late Middle Pleistocence, the oldest age is TL206.000±13.500kaBP. The information of Early Pleistocence is accumulated in the sixth stage terraces in Pingshi and the Baojing Palace in Yingde, belonging to late Early Pleistocence, whose oldest age is TL819.00±57.000kaBP. It is estimated that the speed of the tectonic uplift in north Guangdong was 0.73m/10ka in last million years, and according to calculation, the age of the upper-gravel bed of the ground river terrace in Baojing Palace, which is 111m higher than the Beijiang River, is 1.52MaBP.