A research team led by Prof. XU Honghe and Prof. WANG Yi from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences (NIGPAS) revealed the age and stratigraphical sequence of ancient petroleum reservoir (APR) in West Junggar, northern Xinjiang, China. 

Their findings were published in Journal of Stratigraphy. 

Devonian witnessed the first forest on the Earth and the earliest coal formed by land plants. Abundant plant fossils, hydrocarbon source rocks and ancient petroleum reservoirs were found in the Middle to Upper Devonian of West Junggar. 

Based on detailed study of the Devonian paleosol section and the lithostratigraphical of the upper and lower strata, the researchers found that the ancient petroleum reservoir belong to the Upper Member of the Hujiersite Formation, with the following stratigraphic sequence: the underlying unconformable is Lower Jurassic Badaowan Formation, and the overlying the Upper Devonian is Zhulumute Formation, and then the Upper Devonian is Honguleneng Formation.

The core layer is 2 m thick, and the lithology is dominated by sandstone and mudstone. The plant fossil Barsassia sibirica and Hoxtolgaya sp., produced in the outcrop of the ancient reservoir, are the index and representative fossils of Middle Devonian terrestrial strata in North Xinjiang. Hence, the age of the reservoir is determined as Middle Devonian (Givetian).  

The researchers also systematically investigated the Devonian lycopsid Barsassia based on the new materials in APR. Related findings were published in Plants. 

Barsassia ornata is determined as the type species of the genus. It is a herbaceous lycopsid consisting of easily recognized and characteristic step-like stem and tight, pseudowhorls, and imbricate fan- or rectangular-shaped leaves.