笔者1992年在汶川下庄的结晶灰岩中采到了海百合茎化石，证实其时代属奥陶纪。
In 1992, the author found fossil crinoid stems in crystalline limestone at Xia-zhuang, Wenchuan, which were determined to be of Ordovician age.
华北石炭纪岩溶型铝土矿的主要物质来源为下伏的晚寒武世—中奥陶世碳酸盐岩。
The material source of the Carboniferous karst type bauxite in North China mainly came from the underlying Late cambrian-middle Ordovician carbonate rock.
华北石炭纪岩溶型铝土矿的主要物质来源为下伏的晚寒武世—中奥陶世碳酸盐岩。
The material source of the Carboniferous karst type bauxite in North China mainly came from the underlying Late cambrian-middle Ordovician carbonate rock.
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