浙江长兴煤山二叠-三叠系界线剖面磁性地层特征

煤山二叠-三叠系剖面(31.1°N,119.7°E)包括晚二叠世长兴组和早三叠世青龙组,厚约60m,共采集古地磁样品111块。测量结果表明该剖面存在6个正、反极性带,它们都属于Illawarra混合极性间隔。二叠-三叠系界线位于正极性带V底界以上1.2(2.7)m,实验证明,长兴组下段岩石中磁性矿物主要为针铁矿、赤铁矿和含钛磁铁矿;上段岩石中以含钛磁铁矿和磁铁矿为主,部分岩石也含较多的针铁矿。青龙组灰岩和泥灰岩中主要含磁铁矿和赤铁矿。根据磁性稳定样品结果,获得三叠纪初期古地磁极位于50.7°N,230.3°E,采样地区古纬度为12.3°N。     

MAGNETOSTRATIGRAPHY OF PERMO-TRIASSIC BOUNDARY SECTION OF MEISHAN OF CHANGXING,ZHEJIANG

A hundred and eleven samples were collected from the Permian-Triassic boundarysection of Meishan (31.1°N, 119.7°E) which includes the Changxing Formation of thelate Permian and the Qinglong Formation of early Triassic. The thickness of the sectionis about 60 m. Paleomagnetic results indicate that six normal and reversed polarity zoneswere recorded in the section which all belong to the Illawarra mixed interval. Theboundary of Permo-Triassic lies at 1.2 m (or 2.7 m) above the bottom of normal polarityzone V. The magnetic minerals in the rocks of the lower part of the Changxing Forma-tion mainly are goethite, haematite and titaniferous magnetite while in the upper part ofthe formation are chiefly titanomagnetite and magnetite, goethite is secondary. Magne-tite and haematite as the main magnetic minerals were included in marl and mudstone ofthe Qinglong Formation. Based on the results of the magnetically stable samples thepaleopole position of 50.7°N, 230.3°E was obtained, meanwhile, the paleolatitude