Ediacaran large acanthomorphic acritarchs from the Zavkhan terrane of Mongolia reveal a close paleogeographic affinity with Yangtze block and Lesser Himalaya (India)

Abstract The Zavkhan terrane (western Mongolia) sits in the core of the Central Asian Orogenic Belt and holds the key to understanding the evolution of the belt. However, the Neoproterozoic position of the Zavkhan terrane has remained contentious for a long time. Current models propose either a Siberian affinity, a peri-Siberian location, or an isolated paleogeographic position in the Paleo-Asian Ocean. These competing interpretations rely predominantly on tectonic and sedimentary evidence, with a notable lack of paleontological constraints. Here, we report Ediacaran large acanthomorphic acritarchs (LAAs) from the Shuurgat Formation at three sections in the Duruvlgin and Aldarkhaan areas of the northern Zavkhan terrane. Integrated with carbon isotope data from the same formation, these acritarchs support a stratigraphic correlation with the lower Doushantuo (Yangtze block) and Krol A (Lesser Himalaya) formations, indicating an early Ediacaran age. The Shuurgat LAA assemblage, comprising 24 species, shows high similarity to those of Yangtze block (South China) and Lesser Himalaya (northern India), and it shares a number of taxa that are common to, or even restricted to, these two blocks. Quantitative bioprovincial analysis of a global Ediacaran LAA database further confirms their inclusion within a single bioprovince. Together with comparable detrital zircon age spectra and stratigraphic sequences, these results support a close paleogeographic affinity of the Zavkhan terrane with the Yangtze block and Lesser Himalaya in the Ediacaran, challenging models invoking a Siberian connection.