苏北老黄河三角洲北部末次冰盛期以来沉积序列研究

RESEARCH OF THE SEDIMENTARY SEQUENCES IN THE NORTHERN OLD YELLOW RIVER DELTA SINCE THE LAST GLACIAL MAXIMUM

ZK14孔是位于苏北老黄河三角洲北部地区的1个50m全取心钻孔,对其上部（1.0~22.0m）岩心沉积物的沉积特征分析,结合AMS14 C测年结果,表明末次冰盛期以来该地区主要沉积了硬黏土层和河流沉积（末次冰盛期至全新世早期,22.00~16.63m）、潮坪—浅海—老黄河三角洲沉积（全新世早期至公元1855年,16.63~1.00m）,沉积物主要以黏土质粉砂和粉砂为主,夹少量细砂薄层。沉积物粒度频率曲线在16.63m以上为单峰-双峰分布交替出现,而在16.63m以下则出现三峰分布,向下过渡为双峰和单峰分布。沉积物粒度参数（分选系数、偏态和峰度）变化频繁,表明了物源（河流和海域来源）和沉积动力环境（径流、潮汐及波浪作用）的复杂性。ZK14孔末次冰盛期以来沉积序列的形成,受到海平面与物源变化以及沉积动力条件的共同影响。

This paper focuses on the sedimentary features of the upper part （1.0~22.0 m） of the core ZK4, which is located in the northern Old Yellow River Delta, northern Jiangsu Province. The results, together with AMS 14C dating, suggest that a hard clay bed and fluvial sediments （ between the core depth 22.00 and 16.63 m） be deposited during the Last Glacial Maximum （LGM） and the early Holocene, overlaid by the sediments （16.63~1.00 m） of tidal flat, shallow sea and Old Yellow River Delta from early Holocene to AD 1185. The core consists largely of clayey silt and silt intercalating a small number of thin layers of fine-grained sands. The grain-size frequency curves of the core sediments above 16.63 m are char- acterized by the alternation of unimodal and bimodal distributions, while the deposits under 16.63 m show a pattern of trimodal distribution, which changes to unimodal and bimodal distributions downwards. The sediment grain-size parameters fluctuate frequently in the core, indicating the complexity of the sediment sources （fluvial and marine） and sedimentary dynamics （freshwater runoff, tide and wave）. The sedimentary sequence since the LGM, as revealed by the core ZK14, was developed under the joint interaction of sea level, sediment source and sedimentary dynamics.