A diverse trackway-dominated marine ichnoassemblage from the Lower Triassic in the northern Paleotethys: Ichnology and implications for biotic recovery

Abstract

Here, we document a diverse ichnoassemblage from the marine interbeds of the Lower Triassic terrestrial succession in the Houzhougongmiao (HZGM) section of Shaanxi Province, western North China. The integrated biostratigraphic data (bivalve, palynology and conchostracan) reveals that the ichnofossil-bearing marine beds are Griesbachian (Induan, Early Triassic) in age. The marine interbeds are interpreted as the result of the earliest Triassic transgression of the Paleo-Tethys Ocean northward to the southern margin of North China Craton. The HZGM ichnoassemblage includes 17 ichnospecies in 16 ichnogenera and is dominated by the shallow-tier Asteriacites and Biformites produced by ophiuroids, the scratch marks or trackways Dimorphichnus, Diplichnites, and Monomorphichnus produced by arthropods, with a minor constituent of the fish swimming trace Undichna. Of these, the hook-shaped imprints Biformites, representing the arm moving impressions of ophiuroids, are reported for the first time from the Lower Triassic. These trace-makers are interpreted to have lived in a low energy, semi-restricted, but oxygenated, shallow embayment environment. Although possessing relatively high ichnodiversity, the HZGM ichnoassemblage differs clearly from other coeval diverse ichnocoenoses in the lack of complex burrow forms (i.e. Thalassinoides, Diplocraterion, or Rhizocorallium) and mixed layer, and in having abundant shallow tiers. Accordingly, the resting trace or trackway-dominated ichnoassemblage from the HZGM section may represent an exceptional ichnofauna, an initial recovery of the trace-maker ecosystem after the Permian-Triassic mass extinction. The trace-makers such as arthropods and ophiuroids perhaps were opportunistic organisms that proliferated in marginal marine settings when other biota were still suffering post-extinction biotic depletion and environmental stresses.

Intensifying aeolian activity following the end‐Permian mass extinction: Evidence from the Late Permian–Early Triassic terrestrial sedimentary record of the Ordos Basin, North China

“…The Liujiagou Formation has an extremely sparse fauna and flora, but an Early Triassic age is supported by common microbially induced sedimentary structures (MISS) in the mudstones, which globally are a common feature formed after mass extinctions (Bottjer & James, 1999;Sheehan & Harris, 2004;Chu et al, 2015aChu et al, , 2017Tu et al, 2016) , 1980a,b;Shu & Norris, 1988). These fossils are part of the gradually recovering ecosystem after the PTB extinction and confirm its age as late Early Triassic (Institute of Geology, Chinese Academic of Geological Sciences, 1980a,b;Shu & Norris, 1988;Ouyang & Norris, 1999;Nesbitt et al, 2010;Feng et al, 2017;Shu et al, 2018).…”

AQUARIA-BASED OBSERVATIONS OF THE OPHIUROIDOPHIOLEPIS SUPERBAAND THE TRACKWAYS IT PRODUCES

“…Trace fossils in the ichnogenus Biformites are most commonly attributed to ancient ophiuroid movement (Schlirf 2012; Feng et al 2019). Lower Triassic traces from central China, which resemble some of the traces produced in our study, were identified as Biformites zhadaensis (Feng et al 2019) (Fig. 6).…”

“…Comparison of a fossil trackway to trackways produced in lab setting. A ) Modified from Feng et al (2019). Biformites in the Triassic Sunjiagou Formation of Shaanxi Province, northwestern China preserved as convex epirelief.…”

“…Although fossil evidence of ophiuroids is abundant, their tendency to disarticulate makes meaningful interpretation of their role in ancient systems difficult (Kerr et al 2004; Fernández et al 2019). In contrast, trace fossils attributed to ophiuroids are common and diverse (Yang and Song 1985; Wilson and Rigby 2000; Bell 2004; Schlirf 2012; Knaust and Neuman 2016; Belaústegui et al 2017; Feng et al 2019) and provide clear evidence of occupation of a particular depositional setting if the trace fossils are demonstrated to have indeed arisen from ophiuroid activity (Frey and Seilacher 1980). Trace fossil evidence can be used to analyze behavior of animals that have poor fossil records and would otherwise be overlooked in paleoecology.…”

The variations of terrestrial trace fossils and sedimentary substrates after the end‐Permian extinction in the Dengfeng area, North China

“…Trace fossils were first applied to the analysis of the causes of the end‐Cretaceous mass extinction (Savrda, 1993). Subsequently, more and more ichnologists employed the marine ichnological records across the EPME to assess the pattern of marine ecosystems (Beatty et al, 2008; Cao & Zheng, 2009; Chen et al, 2011, 2012, 2015; Cribb & Bottjer, 2020; Dineen et al, 2019; Feng et al, 2018, 2022; Feng, Chen, Benton, et al, 2019; Feng, Chen, Bottjer, et al, 2019; Feng, Chen, Woods, & Fang, 2017; Feng, Chen, Woods, Wu, et al, 2017; Guo et al, 2019; Hofmann et al, 2015; Knaust, 2010; Luo et al, 2016, 2017, 2019, 2020, 2021; Pietsch & Bottjer, 2014; Rodríguez‐Tovar & Uchman, 2006; Savrda, 2018; Shi et al, 2015, 2019; Twitchett, 2006; Zhang et al, 2018; Zonneveld et al, 2010) through analysing different ichnological parameters (e.g., bioturbation index, abundance, ichnodiversity, burrow sizes, tiering level). However, understanding the variation of terrestrial trace‐making animals is far behind the marine records around the EPME (Hasiotis, 2002).…”