Paleogeography of microcontinents in northeastern China in view of macroplant Leclercqia (Lycopsida) records during Middle to Late Devonian

Abstract

Paleogeography of the microcontinents in northeastern China is essential to understanding tectonic and dynamic evolution of the Central Asian Orogenic Belt (CAOB). Studies using a variety of scientific and technical means have been carried out on materials ranging from the Late Neoproterozoic to the early Mesozoic of the CAOB. However, evidence from macroplant fossils is rare, and its Devonian-related paleogeography issues await details. In this study, we infer the paleogeography of several microcontinents in NE China based on macroplant fossil records from Middle to Late Devonian. A widely-distributed herbaceous lycopsid macroplant, Leclercqia complexa, is newly identified through re-examinations to specimens collected in the 1980 s from the Middle Devonian of Harbin, Heilongjiang Province, NE China, which paleogeographically belongs to the Songliao-Xilinhot microcontinent. Leclercqia, Archaeopteris and Barsassia macroplants are evidently terrestrial and of inter-land dispersal, and their occurrence data provide distinct evidence for reconstructing relative position between paleo-terranes. Our integrated paleobotanical analysis suggests that the Songliao-Xilinhot and Jiamusi microcontinents were in close proximity to Xing’an, West Junggar, and Kazakhstan blocks other than the North China Craton (NCC) during Middle to Late Devonian. The NCC is the only terrane without the macroplant Leclercqia occurrence and it might be a huge highland where almost all deposits and fossil records were eroded, or an isolated island of plant dispersal in the open Panthalassic ocean during the Devonian Period.