吐鲁番盆地桃树园剖面三叠系与侏罗系生物地层界线

BIOSTRATIGRAPHIC BOUNDARY OF JURASSIC AND TRIASSIC AT THE TAOSHUYUAN SECTION OF TURPAN BASIN.

通过研究吐鲁番盆地桃树园剖面八道湾组下部的孢粉、植物化石，确认层５～８含有孢粉Ａｒａｔｒｉｓｐｏｒｉｔｅｓ，ｐａｒａｔａｅｎｉａｅｓｐｏｒｉｔｅｓ，Ｔａｅｎｉａｅｓｐｏｒｉｔｅｓ等三叠纪的重要分子，同层共生植物有Ｃｌａｔｈｒｏｐｔｅｒｉｓｐｌａｔｙｐｈｙｌａ晚三叠世常见分子；层９出现了孢粉Ｃｙａｔｈｉｄｉｔｅｓｍｉｎｏｒ，Ｃｌａｓｏｐｏｌｉｓａｎｎｕｌａｔｕｓ，Ｑｕａｄｒａｅｃｕｌｉｎａａｎｅｌａｅｆｏｒｍｉｓ等侏罗纪常见分子，同层产有植物Ｐｉｔｙｏｐｈｙｌｕｍｌｏｎｇｉｆｏｌｉｕｍ和Ｂａｉｅｒａｃｆ．ｇｒａｃｉｌｉｓ等具侏罗纪特征的分子。因此认为桃树园剖面三叠系与侏罗系的生物地层界线应划在八道湾组下部的层８与层９之间，在这一界线上下的孢粉植物群主要特征既具有明显的区别，又具有承前启后的连续性和过渡性。

This paper presents the result of the study on the biostratigraphic boundary between the Jurassic and Triassic sediments at the Taoshuyuan Section of Turpan basin. The sporopollen and leave fossils for this study are from the lower part of the Badaowan formation at the Taoshuyuan section. Some important Triassic sporopollen members of Aratrisporites, Parataeniaesporites, Taeniaesposrites are found from bed 5 through bed 8 of the lower Baodaowan formation, together with the leave fossils of Clathropteris platyphylla. While in bed 9 of the same formation appear rich Jurassic sporopollen types of Cyathidites minor, Classopollis annulatus, Quadraeculina anellaformis, associated with the leave fossils of Pityphyllum longifolium and Baiera cf. gracilis. Therefore, the biostratigraphic boundary between Jurassic and Triassic should be between bed 9 and bed 8 of the lower part of the Badaowan formation at the Taoshuyuan section. This biostratigraphic boundary is 30.95 m higher than the lithologic boundary between the Badaowan formation(Early Jurassic) and the Haojiagou formation(Late Triassic) at the same section.