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本文对山西偏关地区中奥陶统地层进行了牙形石动物群的系统研究,根据牙形石动物群的发展演化、垂直分布、形态特征及组合面貌,将区内中奥陶统地层由老至新划分为四个牙形石组合(带):1、Scolopodus flexilis带 (Basilicus (Basileilla)—Eoisotelus组合);2、Tangshanodus tangshanesis带;3、Scolopdus mandalensis—Belodella rigida-A(?)rilobodus simplex组合;4、Paraozarkodina asymmetricus—Microcoelodus asymmetricus—badoud(?)s badouensis带。结合中奥陶统地层的岩性岩相、沉积旋回及地层接触关系,并与国内外同期同层位牙形石动物群对比,将该套碳酸盐岩沉积地层,划分为下马家沟组(1—2化石带)、上马家沟组(3化石组合)及上马家沟组上部(4化石带)。从上马家沟组上部所含牙形石动物群组合特征的分析,显然与下伏上马家沟组牙形石组合面貌不同,独具特色,而与邻区峰峰组牙形石组合面貌相似。为此,笔者将上马家沟组上部层位首次建立一独立地层单位一峰峰组。
In this paper, we systematically studied the conodont fauna in the Middle Ordovician strata in Shanxi Province. According to the evolution, vertical distribution, morphological characteristics and assemblage of the conodont fauna, the Middle Ordovician strata There are four new types of conodont assemblages in the past: 1. Scolopodus flexilis zone (Basilicus (Basileilla) -Eoisotelus combination); 2. Tangshanodus tangshanesis zone; 3. Scolopdus mandalensis-Belodella rigida-A (?) Rilobodus simplex Combination; Paraozarkodina asymmetricus-Microcoelodus asymmetricus-badoud (?) S badouensis zone. Combined with the lithologic facies, sedimentary cycles and strata contact in the Middle Ordovician strata, and compared with the same-level conodont fauna at home and abroad during the same period, the carbonate sedimentary formations are divided into the Lower Majiagou Formation (1-2 fossil zones), Majiagou Formation (3 fossil assemblages) and Shangjiajagou Formation (4 fossil zones). The analysis of the characteristics of the association of the conodont fauna assemblages in the upper part of the Shangjiagou Formation clearly shows that it has a distinctive appearance with the conodont assemblage of the Shangmajiagou Formation, . To this end, the author will be the first layer of Majiagou set up an independent strata unit a peak group.