Abstract:
During the Silurian–Devonian Boundary (SDB) interval, in contrast to the predominantly carbonate facies
observed in Europe and North America, China was composed of several plates/terranes dominated by clastic and
pyroclastic rocks. Continuous sections across the SDB have been only sporadically reported from the orogenic
belts and southwestern margin of South China. In many regions or sections in China, the identification of the SDB
is based solely on fossil assemblages or non-index fossils, which results in only a rough approximation of the
position of the boundary. This study focuses on the Junggar area in the Central Asian Orogenic Belt, characterized by pyroclastic rocks and scarcity of fossils compared to regions with carbonate dominated successions.
This paper summarizes previous research findings and discusses the SDB in northern Xinjiang, China, integrating
new data on Devonian conodont Caudicriodus hesperius, the presence of benthic organisms represented by
encrinurid trilobites and crinoids, and the occurrence of late Silurian graptolites, along with the first organic
carbon isotope curve around the SDB for the Central Asian Orogenic Belt, and provided crucial evidence for the
recognition of the SDB in the orogenic belt area of China, consindering the SDB in Northern Xinjiang is located
within the Utubulag Formation in the western Junggar and the presence of the SDB in the Kaokesaiergai Formation of the eastern Junggar has also been confirmed. The age of the corresponding strata: Utubulag, Manger,
Kaokesaiergai formations are revised, and a more detailed description of the classic sections of the SDB in
northern Xinjiang is provided. The new fossil and geochemical data serve as basis for recognition of the Silurian–Devonian boundary in northern Xinjiang, and also contribute to a more comprehensive understanding of
paleoenvironmental events at the Silurian–Devonian transition in the northern hemisphere and the orogenic belt
areas.
