【摘要】 通过对里下河南部泰州地区PM4剖面样品的微体古生物鉴定及粒度分析,结合AMS14 C测年,探讨了该地区全新世以来沉积环境的演化。研究结果表明,全新世以来,该地区的沉积环境经历了湖相、滨海沼泽、海湾、瀉湖、湖相5个阶段。11900～4850cal.aBP:沉积物颜色为灰色-灰黑色,颗粒较细,为极正偏的尖峰态,水动力条件较弱,不含有孔虫和介形虫,为湖相沉积;4850～4250cal.aBP:水动力增强及粗颗粒沉积物增加,含有少量有孔虫,为滨海沼泽;4250～4050cal.aBP:砂质成分急剧增加,含有大量有孔虫,位于黄桥沙坝的北汊道内,为海湾沉积;4050～1850cal.aBP:粒度变细,水动力减弱,含有少量有孔虫及介形虫,为瀉湖沉积;1850～0cal.aBP:粒度变细,分选变好,水动力条件较弱,不含有孔虫,含有少量介形虫,为湖相沉积。更多还原

【Abstract】 The PM4 section,3.4 m in thickness,occurs in the south of the Lixiahe Plain(32°34′N,119°56′E).The section lithologically consists of silt,clay and sand.170 samples every2 cm are taken for grain size analysis in addition to7 samples for AMS 14 C dating and86 samples every 4 cm for determination of foraminifera and ostracoda species.5 stratigraphic units are identified from bottom to top according to the foraminifera and ostracoda assemblages,median grain size and other grain size parameters.The sediments from depth of 1.4～3.4 m or 11900～4850 cal.aBP are dominated by gray-black lacustrine deposits consisting mainly of silt,83.9% on average.Clay and sand concentrations are 14.9% and1.2%,respectively on average.Neither foraminifera nor ostracoda has been found.From the depth range of 1.1～1.4 m or 4850～4250 cal.aBP in age,the increase in silt and sand content indicates that water dynamics was intensified comparing to that in previous stage,suggesting an environment of coastal swamps.From4250～4050 cal.aBP(1.14～0.98 m),sand sharply increased to 11.7%～15.3%,or 13.9% on average,indicating that the depositional environment was a bay behind the north branch of the Huangqiao sand bar.From4050～1850 cal.aBP or from0.98～0.68 m in depth,silt increased to 82.9%～88.6%,86.3% on average,indicating that the hydrodynamics was weakened in that region.Foraminifera was rare,suggesting a lagoonal facies.During the period of 1850～0 cal.aBP(0.68～0 m):sand input was reduced to1.0%～11.1%or 3.2%on average.No foraminifera is observed excluding small amount of ostracoda,suggesting a lacustrine environment.更多还原