Cambrian in the General Stratigraphic Scale of Russia

The Cambrian Standard Scale of the General Stratigraphic Scale (GSS) of Russia is presented, which has been inspected by the Interdepartmental Stratigraphic Committee of Russia. The key principles for the updated Cambrian Standard Scale are: 1) all Stages must have stratotypes; 2) the limitotypes of the Stages should be established in the stratotypes of these Stages; 3) the stratotypes of the Stages should be characterized by excellent outcrop, have underlying and overlying sediments in the same section or in several, uniquely correlated outcrops. This is necessary to ensure that the volume of the Stage is complete. In the GSS the Cambrian is divided into three divisions. The stratotypes of all Cambrian Stages are located on the Siberian Platform. The Lower Cambrian includes four Stages: Tommotian, Atdabanian, Botomian, Toyonian. The Tommotian stratotype is located in the Aldan River. Three archaeocyathid Zones are distinguished: Nochoroicyathus sunnaginicus, Dokidocyathus regularis, Dokidocyathus lenaicus – Tumuliolynthus primigenius. The Atdabanian stratotype was established in a series of outcrops of the Lena River. It includes parallel archaeocyathid and trilobite zones. Archaeocyathid Zones: Leptosocyathus polyseptus – Retecoscinus zegebarti, Carinacyathus pinus, Nochoroicyathus kokoulini, Fansycyathus lermontovae; trilobite Zones: Profallotaspis jakutensis, Repinaella, Delgadella anabara, Judomia – Uktaspis. The Botomian hypostratotype is a series of outcrops on the Lena River, directly overlying the Atdabanian stratotype. Five Zones are distinguished: Triangulaspis annio – Bergeroniellus micmacciformis – Erbiella, Bergeroniellus gurarii, Bergeroniellus asiaticus, Bergeroniaspis ornata, Bergeroniellus ketemensis. The Toyonian stratotype is a continuous series of outcrops on the Lena River, where it directly overlies the Botomian. Two Zones are distinguished: Lermontovia grandis, Anabaraspis splendens. The Middle Cambrian includes four Stages: Molodian (Amgaian), Chayian, Tiksian, Chomurdakhian. The stratotype of the Molodian is located in the Molodo River. It includes three Zones: Ovatoryctocara granulata, Kounamkites, Triplagnostus gibbus. The Chayian stratotype is established in a series of outcrops of the Yudoma and Maya Rivers. Two Zones are distinguished: Tomagnostus fissus – Ptychagnostus atavus, Ptychagnostus punctuosus – Linguagnostus grönwalli. The Tiksian stratotype is the Khos-Nelege River Section. It includes two Zones: Centropleura loveni – Anomocarioides limbataeformis, Lejopyge laevigata – Aldanaspis truncata. The Chomurdakhian hypostratotype is located in the same Khos-Nelege River Section. Three Zones are distinguished: Proagnostus bulbus, Clavagnostus spinosus, Glyptagnostus stolidotus. The Upper Cambrian includes four Stages: Omnian, Mokuteian, Novotukalandian, Khantaian. The three lower Stages have stratotypes in the Chopko River Section and sequentially build upon each other. The stratotype of the uppermost Khantaian Stage was established in the Kulyumbe River Section. The Omnian includes three Zones: Glyptagnostus reticulatus, Stigmatoa destructa, Erixanium sentum. The Mokuteian includes three Zones: Pseudoglyptagnostus clavatus–Irvingella angustilimbata, Mokutella mokuteica, Irvingella cipita. The Novotukalandian includes three Zones: Irvingella norilica, Tukalandaspis egens, Ketyna ketiensis–Monosulcatina laeve. The Khantaian includes two Zones: Dolgeuloma abunda–Dolgeuloma dolganensis, Loparella loparica–Plethopeltides magnus. The overlying deposits in the same Kulyumbe River Section are Ordovician. The Ordovician base is proposed to be defined by the FAD of the trilobite Eoapatokephalus antiquus Rosova and Makarova, which is found together with graptolite Dictyonema intermedium Prantl et Pribyl and on a close level with the conodont Cordylodus proavus Müller. This boundary is clearly marked across the Siberian Platform and adjacent areas.