Palynological analysis of the lower member of the Hongguleleng Formation and discussion of the Frasnian/Famennian boundary in Western Junggar, NW China

Abstract

Palynological investigations have been carried out on samples from the Upper Devonian Hongguleleng Formation of Western Junggar, Xinjiang, NW China. In total, 28 miospore species belonging to 19 genera and 28 acritarch species assigned to 17 genera have been recognized from the Lower member of the Hongguleleng Formation in the Bulongguoer section. The palynofloral assemblages, in particular the miospore taxa, are similar to those from the eastern European early Famennian Cyrtospora cristifer -Diaphanospora zadonica (CZ) miospore Biozone, albeit quantitatively and qualitatively depauperate. The miospore assemblage zone is also consistent with the previous zonal schemes in light of brachiopod and conodont fauna assemblages, as well as carbon isotope geochemistry, that indicates a correspondence to the Palmatolepis crepida conodont Biozone. The earliest Famennian Corbulispora vimineus -Geminospora vasjamica (VV) (more or less equivalent to the Palmatolepis triangularis conodont Biozone) miospore Biozone is most likely to be missing in the Hongguleleng Formation of the Bulongguoer section . The palynostratigraphy and sedimentary sequence in Western Junggar are very similar to those from some other regions of South China, western and eastern Europe, which increases the knowledge of the evolution of the palaeoclimate, palaeogeography and regional sedimentary environment of the Central Asian Orogenic Belt (CAOB), Eastern European Platform, and Laurussia.

Malformations in Late Devonian brachiopods from the western Junggar, NW China and their potential causes

“…The formation is divided into three members: the Lower Member is composed of thin bioclastic limestones, muddy limestones and shales; the Middle Member is mainly made up of fine pyroclastic rocks with a few sandy and muddy limestones; and the Upper Member consists of calcareous clastic rocks with a small amount of bioclastic limestones ( Hou et al, 1993 ). The formation is mostly Famennian in age ( Ma et al, 2017 ; Zong et al, 2020 ; Shen et al, 2021 ; Stachacz et al, 2021 ). The Hongguleleng Formation is very rich in many types of the early Famennian fossils, such as acritarchs, bivalves, brachiopods, bryozoans, cephalopods, chondrichthyans, conodonts, conulariids, corals, echinoderms, gastropods, ostracods, plants, radiolarians, spores, trace fossils, and trilobites ( Liao, 2002 ; Zong R W, 2021, unpublished specimens).…”