NEW BIOSTRATIGRAPHIC AND PALEOMAGNETIC DATA ON THE DEVONIAN IN THE WESTERN MONGOL-OKHOTSK FOLD BELT

Abstract

Crinoids of the Lower-Middle Lochkovian were first determined for the Devonian deposits of the Mongol-Okhotsk fold area, and also first preliminary paleomagnetic data were obtained for these deposits. Lithological and paleontological distinctions were defined regarding the character of sections of the left and right banks of the Onon River (eastern Transbaikal region) assigned earlier to the Makarov unit of the Middle-Upper Devonian. These data allow us to divide the Makarov unit into two different-age stratigraphic units. One of them, located on the right bank, is suggested to be reckoned as the Makarov unit of the Lower Devonian. The left-bank deposits are distinguished as a new, Aratungin unit of the Middle-Upper Devonian. High temperature characteristic components of In natural remnant magnetization have been established basing on temperature cleaning with employment of graphic analytical testing methods. Low (near-equator) paleolatitudes of formation of terrigenous rocks of the Argun terrane in the Devonian have been recognized. The computed position of the paleopole coincides with the trajectory of its seeming movement for the North China geoblock in the Middle Paleozoic.