珠江三角洲中山横栏地区晚第四纪以来的沉积特征

中山横栏地区在珠江三角洲第四纪地层研究中具有代表性。本文通过对该地区第四纪Ⅳ01钻孔岩性、粒度及地球化学特征的综合研究,探讨珠江三角洲晚第四纪以来的沉积特征。结果表明,珠江三角洲晚第四纪沉积物自下而上包含三次沉积旋回:一次晚更新世海侵旋回和两次全新世的海侵旋回,其形成的下粗上细正向序列在进积型三角洲中具有一定的特殊性;在沉积学分析的基础上,结合粒度和微量元素B、Ba、Sr的指相特征,探讨珠江三角洲晚第四纪以来的海侵-海退旋回,揭示在中全新世中晚期(约5~2.5 kaBP)发生了海退过程,进一步印证中山横栏地区晚第四纪以来存在三次海侵事件的认识。

Sedimentary characteristics in Henglan area,Zhongshan city of the Pearl River delta since the Late Quaternary

Henglan area, Zhongshan area of the Pearl River Delta has special significance to research of the Qua-ternary strata in the region of the South China. The Henglan Formation of Holocene was defined due to its excel-lent representative of the area. Based on comprehensive analysis on lithologic feature, grain size and geochemical of the coreⅣ01 in Henglan area, the sedimentary characteristics in this area since the late Quaternary was stud-ied. It is suggested that since the Late Quaternary, there were three sedimentary cycles in the study area:one in the late Pleistocene and two in the Holocene. Because of the distinctive sedimentary environment of the Pearl River Delta, the sedimentary cycles of the delta were particular by the positive sequential patterns (the coarser sediments at lower layer and becoming finer upwards) of the Progradational delta. Based on the above research, the analysis of grain size and the trace elements contents of B, Ba and Sr in the sediments, the paper further dis-cussed the processes of transgression and regression since Late Quaternary in the study area. Three regres-sion-transgressions cycles could be recognized: the earliest transgression happened in middle-late Late Pleis-tocene, while the others followed until the Holocene. The latter two transgression, began about 7.5 ka B P, were separated by the regression appeared in middle-late middle Holocene (5~2.5 ka B P).