河北唐山西部PZK14孔晚新生代沉积演化特征

Sedimentary evolution of borehole PZK14 in western Tangshan area during Late Cenozoic

为查明唐山西部平原区晚新生代以来松散堆积物的沉积演化特征,依托鸦鸿桥幅1∶5万区域地质调查工作,对唐山西部PZK14孔进行色度、粒度、视电阻率测井、自然伽马测井等研究,划分沉积相并计算各时段的沉积速率,结果表明该地区新生代晚期主要发育湖泊相、三角洲相和河流相。早更新世初始发育三角洲相,随着气候转暖,古滦河冲积扇退积,三角洲相转变为河流相;早更新世中—晚期,发育3个湖泊-三角洲相沉积旋回;中更新世发育一个湖泊-三角洲相沉积旋回;晚更新世初沉积了巨厚的湖相层,随着气候转冷,渤海湾沿岸海侵结束,湖盆开始萎缩,转变为河流相;全新世则以河间洼地沉积为主。沉积速率-年龄曲线表明第四纪以来构造作用对该地区沉积速率控制较弱,气候为影响沉积相发育的主要因素。第四纪各个时期的沉积速率均较快,奥杜威极性亚时(1.95~1.77 Ma)沉积速率最大,约为194.0 m/Ma;2.52~1.95 Ma沉积速率最小,约为111.2 m/Ma。研究成果对恢复该区域古地理演化、水工环地质勘查等具有重要意义。

In order to find out the sedimentary evolution characteristics of loose deposits in the western plain of Tangshan since the Late Cenozoic,the authors in this paper studied the color,particle size,apparent resistivity logging and natural gamma logging of the borehole PZK14 in western Tangshan and divided the sedimentary facies with the calculation of deposition rate of each period,based on the 1∶50,000 regional geological survey in Yahongqiao area.The results show that lacustrine facies,delta facies and fluvial facies are mainly developed in this area during the Late Cenozoic.The delta facies was developed at the beginning of the Early Pleistocene,while the delta facies was transformed into fluvial facies with the retrogradation of alluvial fan in the ancient Luanhe River when the climate began to become warming.Three lake-delta sedimentary cycles developed during middle to late Early Pleistocene.A lake-delta sedimentary cycle developed in the Middle Pleistocene.At the beginning of Late Pleistocene,a thick lacustrine layer was deposited.As the climate became cold,the transgression along the coast of Bohai Bay ended and the lacustrine basin began to shrink and transformed into fluvial facies.The Holocene was dominated by interfluvial depression.According to the sedimentation rate-age curve,tectonic control of the sedimentation in this area has been weak since the Quaternary,and the climate is the main factor affecting the development of sedimentary facies.The sedimentation rate of the Quaternary was relatively fast,and the Olduvai polarity subchron(1.95~1.77 Ma)had the highest sedimentation rate of 194.0 m/Ma.The deposition rate of 2.52~1.95 Ma is the smallest,which is about 111.2 m/Ma.This achievement is of great significance to the restoration of paleogeographic evolution and the geological exploration of hydraulic environment in this region.