摘要
现今南京秦淮河横贯市区南部,到城西经三汊河入长江。前人一直把市区城南和城北分属秦淮河流域和金川河流域。我校承担市建委下达的古河道地质调查任务,经三年工作,搜集了810个钻孔资料,作了6条钻孔地质剖面,共测8条物探剖面,有效测点139个,还做了粒度、重砂、差热及^(14)C分析,发现市区埋藏型秦淮河古道由城南纵贯到城北。文中论证了古河道存在的依据,阐明了古河道埋藏的原因,并对古河道中沉积物的地质时代提出了与前人不同的看法。
The city of Nanjing is located at the zone of the Qinhuai River outlet where it empties its flow into the Changjiang River.Today the Qinhuai River runs through the southern part of the urban district,flows into the Sancho River at the west of the city and then pours into the Changjiang River.However,a southeast-northwest trend trough valley beneath the land surface shows itself clearly by the isobathic concurs of bedrock of-20 to-25 meters derived from a vast amount of drill logs.The accumulated materials within the trough valley are of sedimentary characters and facies of alluvial texture.The analysis of 99 drill logs within the ancient channel has proved that the extension of sand badies is banded in shape and coincides with the extensional orientation of the trough valley.All of the 8 apparent resistivity curves obtained by geophysical method are of K-type.The traces of the ancient channel are reflected also in landforms and hydrologic circumstances.In view of the above facts,it can be determined that the ancient Qinhuai River was flowing frown southeast to northwest across the urban district and reached to the foot of the Shizishan Hill,and then poured into the Changjiang Rver.The ancient channel of the Qinhuai River is of a shallow-buried type,which is filled with the alluvial materials and the depth of its bottom(bedrock)is 30-40 meters below ground level.According to the calculation by 20m.isopach of sand bands of the ancient channel,the valley was 500-800 meters wide,and its maximum width was about 1300 meters.The curvature of the ancient channel is 1.20 which shows that the channel is of the straight-with slightly meandering type,and shows the characteristic of being controlled by the bedrock structure.According to the statistical data and the analytical results of the alluvial materials,their sorting coefficient(QDφ),Skewness(SKφ)and kurtosis(KG)all have the sedimentary features of river bed facies.The age of alluvial materials of the ancient channel had been classified under Lower Pleistocene epoch by the research workers of early years,and later on it was incorporated into the Holocene epoch.But through the present investigation,and the synthetical studies on centrasting the evolution of physiographic stages and the variation of Quarternary climate with the data of fluctuation of sea level of China,as well as on the geochronological data of ^(14)C of some samples concerned,We are convinced that the climate stage of the alluvial materials of the ancient channel should correspond to the Atlantic,prolonged from the last glacial stage of Late Pleistocene to the post-glacial period.Its geological age should correspond to the last stage of Late Pleistocene to the middle stage of the Holocene epoch.
作者
蒋斯善
昂潮海
杨惠成
费锡铨
Jiang Sishan;Ang Chaohai;Yang Huicheng;Fei Xiquan(Nanjing Geological School)
出处
《地质学报》
1986年第1期89-101,共13页
Acta Geologica Sinica
