Late Ordovician (late Katian) cryptospores and chitinozoans from the Mannan-1 borehole, south Tarim Basin, China

Abstract

Well-preserved cryptospore and chitinozoan assemblages were recovered from the Tierekawati Formation (late Katian, Late Ordovician) of the Mannan-1 borehole, south Tarim basin (Tarim Block), China. The chitinozoan assemblage is low in abundance and diversity (two genera, five species), and its age is restricted to the late Katian (Late Ordovician). The cryptospore assemblage consists of the tetrads (three genera, five species) and dyads (three genera, four species), with a low abundance and diversity. It has similarities to the previous records from the coeval deposits around the world. Comparison of two coeval cryptospore assemblages from two boreholes more than 300km apart within the Tarim Block shows the separate landmasses of the south and north Tarim Block were covered with much the same cryptophyte vegetation. The different elements in the vegetation might be caused by the local palaeogeography and palaeoenvironment.