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为了研究奥陶系宝塔组灰岩网状裂缝的形成原因,利用古生物鉴定、野外露头对比及镜下薄片观察等方法进行分析.古生物以头足类、三叶虫、介形类和棘皮类为主,偶见腕足类,未见藻类.裂缝延伸到生物化石时停止,贯穿地层顶底面但未穿透相邻地层,平面呈瘤状、龟裂纹和S曲线等,锯齿状缝合线切穿裂缝.镜下发现灰质基块内散布着泥质团块,泥质团块通过微裂隙互相连通或连通主裂缝,泥质内夹的灰质碎屑长轴沿裂缝展布,新鲜剖面灰质基块与泥质裂缝无明显界限.提出宝塔期扬子板块处于稳定克拉通沉积环境,网状裂缝是在较深水缓慢沉积的低能开阔台地环境下,由于化学分异作用灰质质点聚集、压实作用胶态粘土矿物脱水收缩、泥质随水排出时充填裂缝而形成的,为非构造成因裂缝.
In order to study the formation reason of the limestone net fracture in Ordovician pagoda, the paleontology was analyzed by means of palaeontological identification, field outcrop contrast and microscopic observation of thin slices, etc. The paleontology was identified as cephalopods, trilobites, ostracods and echinoderms The main and occasional brachiopods, no algae.Fractures extending to the fossil stop, through the top and bottom of the formation but did not penetrate the adjacent strata, the plane was tumor-like, crack and S-curve crack, serrated sutures cut through Cracks.It is found by microscope that the muddy mass is scattered in the gray mass base, the muddy mass is connected to each other through the micro-crack or communicated with the main crack, the long axis of the gray mass in the muddy mass is distributed along the crack, And no obvious boundary between shale and fissure.It is suggested that the Paleoteric Yangtze Plate is in stable craton depositional environment and the reticular fissure is in a low-lying and open platform with slow deposition of deeper water. Due to the chemical differentiation, Dehydration and shrinkage of clay minerals, mud with water discharge filled cracks formed, non-structural causes of cracks.