广泛发育于中、上扬子地区的宝塔组是中奥陶顶部地层,代号O2b。由李四光（1924）在长江三峡建立。层型剖面在湖北省宜昌县乡镇北普溪河桥南端。 为一套灰色厚层泥质龟裂纹灰岩。富含头足类化石。
川南地区中奥陶统宝塔组储层具低孔低渗特征，属裂缝性储集类型。
The reservoirs in Baota Formation of Middle Ordovician in South Sichuan are characterized by low porosity and low permeability and belong to a fractured type.
网纹构造是宝塔组石灰岩地层中非常发育且分布广泛的一种构造形态 ，其成因一直存在争论和疑问。
The polygonal reticulate structure is well developed and wide spread in the Pagoda Formation limestones in the whole Yangtze region.
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