Findings of Paleozoic conodonts in xenoliths from kimberlite pipes on the Siberian Platform

Xenoliths of sedimentary rocks are common in kimberlite pipes of the Siberi an Platform. These xenoliths contain well-preserved organic remains, mainly macrofauna (brachiopods, trilobites, etc.). This paleontological evidence is of great importance for geological dating of kimberlite pipes and paleon tological reconstructions of the region where they occur, particularly if d eposits of corresponding age were destroyed by subsequent geologic processe s. Special studies have first revealed rich assemblages of conodonts in xen oliths from kimberlite pipes. This taxon has unique indicative features for stratigraphic correlations and paleogeographical reconstructions. In addit ion, conodonts have a fluorapatite composition of skeleton elements differe nt from that of other fossils and, therefore, have been well preserved in g eologic settings. Sixty five xenoliths from 12 kimberlite pipes were studie d. They contained conodont assemblages from different stratigraphic units - from Lower Ordovician to Jower Carboniferous. The composition of the assem blages allows a reliable dating: of xenoliths with a precision of conodont zones, regional horizons, and stages of the general stratigraphic scale.