新疆塔里木盆地塔中中2井上奥陶统牙形刺化石及生物礁发育时代

CONODONTS FROM THE UPPER ORDOVICIAN IN WELL Z2 OF THE CENTRAL TARIM BASIN AND THE AGE OF CONODONT-BEARING REEFAL BEDS

首次在新疆塔里木盆地塔中地区中2井上奥陶统良里塔格组礁岩中发现保存精美的牙形刺化石,包括6属13种和未定种,含一个新亚种Belodina longxianensis minor subsp.nov.。根据牙形刺化石确定,良里塔格组上部属于上奥陶统中部的Belodina confluens带。中2井良里塔格组第2—4层生物礁发育的精确时代是Belodina confluens带。

Conodonts including 13 species in 6 genera are described from the Lianglitag Formation in Well Z2 of the central Tarim Basin, which ranges from 5 474 to 6 284 m. They are Aphelognathus pyramidalis？, Aphelognathus divergens？ ,Belodina confluens, Belodina baiyanhuaensis, Belodina longxianensis, Belodina longxianensis minor subsp, nov. , Belodina sp. A, Belodina sp. B, ？ Microzarkodina sp. , Panderodus gracilis postoscrobus, Plectodi- nacf. bidentata, Plectodina sp. , Yaoxianognathus lijiapoensisV and Yaoxianognathus yaoxianensis ？. Occurrence of Belodina confluens at 5 522-5 531.6 m indicates that this interval belong to the Belodina confluens Zone. Depth of 5 531.6-6 197.3 m probably belongs to the Belodina confluens Zone, and this needs more study to confirm. Five beds of reef-facies occur in the Lianglitag Formation. The reefal beds 2 to 5 belong to the Belodina confluens Zone.