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陕西陇县位于西安西北约200公里处,属鄂尔多斯地台的西南缘,地层区划归陕、甘、宁盆缘分区平凉—永寿小区(图1).该区奥陶系发育,上、中、下三统俱全.中奥陶统在这里相当于胡乐期和(氵韩)江期的地层,全为笔石相沉积.在前人工作的基础上,傅力浦(1975)、陈均远等(1978)先后对本区中奥陶统笔石带作了进一步的划分.傅力浦根据陇县龙门洞剖面完整、笔石带齐全以及全为笔石相沉积诸特点,修订了原平凉组的含义,其范围相当于从Glyptograptus teretiusculus带—Dicranograptus clingani带的沉积.而陈均远等将这一部分地层重新命名为“龙门洞组”.西北区区域地层表陕西省分册使用了“平凉群”.笔者同意修订后的平凉组,理由将
Long County, Shaanxi Province is located about 200 kilometers northwest of Xi’an, which belongs to the southwestern margin of the Erdos platform. The strata are classified into the Pingliang-Yongshou district of the basin margin of Shaanxi, Gansu and Ningxia (Figure 1) , Under which the Ordovician system is equivalent to the Holocene and (Han-Han) Jiang period strata, all of which are lithic and lithofacies sediments.On the basis of previous work, Fu Li Pu (1975), Chen Junyuan et al. (1978) Successively divided the Ordovician petroglyphs in this area.Fulipu revises the meaning of the original Pingliang Formation according to the complete profile of the Longmen Cave in Long County, From the deposition of -Dicranograptus clingani belt from Glyptograptus teretiusculus, while Chen Junyuan renamed this part of the stratum “Longmendong Formation.” The Northwest Regional Stratigraphic Table used “Pingliang Group” in the Shaanxi Provincial Section. The author agrees to amend Pingliang after the group, reason will be