地质学报2024，Vol.98Issue(2)：494-510,17.DOI:10.19762/j.cnki.dizhixuebao.2023281
柴达木盆地南八仙地区渐新世浅水三角洲物源及沉积演化
Provenance analysis and sedimentary evolution of Oligocene shallow water delta in the Nanbaxian area,northern Qaidam basin
摘要
Abstract
This paper focuses on studying the upper member of the Xiaganchaigou Formation(E2)in the Late Oligocene of the Paleogene.The research objective is to deeply examine the provenance direction,sand body distribution law,and sedimentary microfacies development and evolution of the weak regressive shallow water delta in the expansion period of the E2 in the Nanbaxian area.To achieve this,a comprehensive analysis was conducted using fine core observation,drilling(logging)data,heavy mineral assemblage,ZTR index,sandstone clastic composition,grain size accumulation probability map,and sand-land ratio.The results show that:① The provenance of the E2 sedimentary period in the Nanbaxian area mainly comes from the southern Qilian Mountains,which consist of intermediate-acid magmatic rocks and intermediate-high-grade metamorphic rocks.The provenance direction is almost northeast-southwest.The stable heavy minerals(magnetite,garnet,ilmenite,and zircon)have a high content(ranging from 81.0％to 99.9％),while the unstable heavy minerals(epidote and amphibole)show low content.② The E2 sedimentary period in the Nanbaxian area is characterized by the development of a shallow delta-shallow lake sedimentary environment,primarily featuring underwater distributary channel sand bodies.The predominant lithology is lithic feldspathic sandstone,followed by feldspathic lithic sandstone.The composition maturity and sorting roundness are categorized as medium-poor.The particle size probability curve is mainly one jump and one suspension type,reflecting the influence of river action.Various sedimentary structures are present,including block bedding,normal sequence bedding,parallel bedding,and trough cross-bedding.③ During the E2 sedimentary period,three NE-SW trending sand body enrichment zones were inherited in the Nanbaxian area(sand to ground ratio ranging from 35％to 65％).The degree of sand body development increased from the early to the middle stage,showing a progradation trend.However,the development of sand bodies weakened from the middle to the late stage,showing signs of weak retrogradation.④ The shallow water delta front sedimentary subfacies were inherited in the Nanbaxian areaduring the E32 sedimentary period,with the continuous development of three sedimentary lobes.The underwater distributary channel microfacies are mainly developed,followed by the underwater interdistributary bay microfacies.The development scale of the shallow water delta front increases from the early to middle stage and decreases from the middle to late stage.关键词
浅水三角洲/物源方向/下干柴沟组上段/渐新世/南八仙地区/柴达木盆地Key words
shallow water delta/provenance direction/upper member of Xiaganchaigou Formation/Oligocene/Nanbaxian area/Qaidam basin引用本文复制引用
易定红,石亚军,刘俊丰,刘应如,李积永,王爱萍,马元坤,李红哲,贾正良..柴达木盆地南八仙地区渐新世浅水三角洲物源及沉积演化[J].地质学报,2024,98(2):494-510,17.基金项目
本文为中国石油重大科技项目(编号 2021DJ08,2021DJ1705,2016E-01)和国家重大科技专项(编号 2016ZX05003-006)联合资助的成果. （编号 2021DJ08,2021DJ1705,2016E-01）
