辽河三角洲大凌河河口湿地沉积物晚更新世以来的矿物特征及其物源、气候意义

对辽河三角洲大凌河河口湿地地区ZK3钻孔的58个沉积物样品中碎屑矿物和黏土矿物进行鉴定和分析,结果显示:碎屑矿物中轻矿物占比大,平均含量为95.7%,主要包括斜长石(43.89%)、钾长石(28.10%)和石英(22.45%);重矿物平均含量仅为4.3%,主要为普通角闪石(38.03%)、绿帘石(27.51%)和自生重晶石(12.01%)。黏土矿物中伊利石平均含量(50.3%)最高,其次为蒙脱石(24.5%)、绿泥石(12.7%)和高岭石(12.6%),黏土矿物组合为伊利石-蒙脱石-绿泥石-高岭石型。ZK3孔晚更新世以来沉积物的物源有所差异,但总体上来说,除河道和湖相沉积时期物源主要来自大凌河外,其它沉积环境中沉积物主要来自辽河和大辽河,物源相对稳定。黏土矿物组合特征所指示的气候变化过程与本区域的孢粉数据有很好的对应关系:45~31 ka BP处于庐山—大理的间冰期阶段,蒙脱石/(伊利石+绿泥石)比值较大,指示气候温和湿润;31~11 ka BP为大理冰期阶段,蒙脱石/高岭石比值较低,指示气候寒冷干燥;11 ka BP至今为冰后期阶段,随着新仙女木事件(YD)的结束,温度逐渐回升,蒙脱石/(伊利石+绿泥石)比值升高,指示气候温暖湿润。

Mineral Characteristics,Provenance and Climatic Significance of Wetland Sediments from Dalinghe River Estuary in Liaohe Delta Since Late Pleistocene

A total of 58 samples were collected and analyzed for detrital minerals and clay minerals in drillhole ZK3 in the Dalinghe River Estuary.The research reveals that the light minerals account for the majority(average 95.7%)of the sediments,and include mainly plagioclase(43.89%),K-feldspar(28.10%)and quartz(22.45%).Heavy minerals only account for 4.3%of the sediments,and consist mainly of hornblende(38.03%),epidote(27.51%)and authigenic barite(12.01%).Clay minerals comprise mainly illite(50.3%),followed by smectite(24.5%),chlorite(12.7%)and kaolinite(12.6%),constituting an illite-smectite-chlorite-kaolinite assemblage.The sediment provenance of core ZK3 is quite complicated across the geological history.However,except the provenance of the river channel and lacustrine sediments may come from the Dalinghe River,the sediments of other facies were derived mainly from the Liaohe and Daliaohe rivers.Paleoclimatic change,inferred by comprehensive analysis of clay minerals,corresponds well with pollen studies in the Liaohe Delta:in 45~31 ka BP,the smectite/(illite+chlorite)ratios are relatively high,implying a warm and wet climate;in 31~11 ka BP(Lushan inter-glacial stage),the smectite/kaolinite ratios are low,indicating a cold and dry climate during the Dali ice age stage;from 11 ka BP to present(after the end Younger Dryas(YD)),the temperature gradually rises with rising smectite/(illite+chlorite)ratio,which reveals a post-glacial hot and wet climate.