EVOLUTION OF SEDIMENTARY ENVIRONMENT IN THE NORTH HETAO BASIN SINCE 344 Ka
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摘要: 通过对河套盆地北部获取的377 m钻孔岩芯进行沉积相及粒度特征分析,并结合多种测年手段,揭示了河套盆地北部中更新世晚期以来的沉积环境演变过程。根据粒度参数特征变化把钻孔划分为6个沉积环境阶段:344~326 ka为滨湖相沉积环境;326~165 ka为半深湖相沉积环境;165~130 ka为滨湖三角洲相沉积环境;130~100 ka为浅湖相沉积环境;100~10 ka为滨湖—河流相沉积环境;10 ka~今为河漫滩相沉积环境。河套盆地中更新世晚期到晚更新世期间存在统一的古大湖,晚更新世以后古大湖分解并消失。Abstract: Through analysis of sedimentary facies and grain size characteristics from 377 m drilling cores in the north Hetao Basin, combined with different dating methods, the evolution of sedimentary environment in the north Hetao Basin since late Middle Pleistocene is revealed. According to the characteristics of grain size parameters, sedimentary environment can be divided into 6 stages:lakeshore (344~326 ka)-semi-deep lake (326~165 ka)-lakeshore delta (165~130 ka) -shallow lake (130~100 ka)-lakeshore-fluvial (100~10 ka)-washland (10 ka~now). Comprehensive research shows that a unified paleo-megalake has been existed in the Hetao Basin from middle Pleistocene to late Pleistocene. After late Pleistocene, the paleo-megalake disintegrated and disappeared.
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Key words:
- grain size /
- sedimentary environment /
- paleolake evolution /
- the Hetao Basin
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表 1 钻孔光释光年代数据
Table 1. OSL dating data of the drilling core
原始编号 埋藏深度/m 含水率/% U/×10-6 Th/×10-6 K/% 剂量率(Gy/ka) 等效剂量(Gy) 年龄/ka C2-29 45.54 11±5 1.82±0.03 8.87±0.03 1.57±0.01 2.45±0.09 70.67±3.46 28.83±1.77 C2-44 79.98 13±5 2.77±0.04 13.16±0.32 1.93±0.04 3.89±0.23 307.63±11.40 79.16±5.60 C2-53 96.18 32±5 1.31±0.02 6.36±0.06 1.93±0.05 2.04±0.08 168.55±2.15 82.70±3.34 C2-64 118.78 20±5 2.57±0.06 14.02±0.11 2.09±0.03 3.76±0.22 382.15±20.35 101.61±8.02 C2-75 145.12 26±5 2.22±0.02 11.63±0.14 1.98±0.02 2.65±0.09 354.37±11.65 133.62±6.35 C2-92 187.61 24±5 1.13±0.01 5.95±0.04 2.10±0.01 2.26±0.09 356.93±2.61 158.00±6.68 表 2 钻孔14C年代数据
Table 2. 14C dating results of the drilling core
原始样号 测年材料 深度/m AMS14C年代/a BP 13C/‰ 校正年代/a BP 日历年代/Cal a BP HL-223 有机质全样 5.57 4470±30 -24.2 4480±30 4995±20 HL-1028 有机质全样 25.9 13790±50 -24.1 13800±50 14747±172 表 3 钻孔230Th年代数据
Table 3. 230Th dating results of the drilling core
样号 238U/×10-9 232Th/×10-12 230Th/232Th δ234U* 230Th Age/yr(校正) δ234UInitial**(校正) 230Th Age/yr BP zk1 2886±4 2251524±45118 24.8±0.5×10-6 170.2±1.8 319945±13649 420±17 319880±13649 -
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