Biotic recovery after the Late Ordovician Mass Extinction Event: insights from ichnofossils of the middle–upper Yangtze Block, South China

ABSTRACT

The timing and pattern of biotic recovery after the Late Ordovician Mass Extinction (LOME) are highly controversial. Here, we conducted a systematic investigation on ichnofossils from the lower Silurian succession of the northwestern Hunan province, middle-upper Yangtze Block, South China. Biotic recovery of marine benthic ecosystems after the LOME was analysed and discussed for the first time using multiple ichnofossil proxies. The vertical distribution and evolutional trends of trace fossil assemblages suggest that biotic recovery was significantly delayed by the widespread anoxia during the latest Hirnantian to middle Aeronian. The recovery displays a stepwise pattern and reached a relatively high stage during the late Aeronian, although a full recovery was generally not achieved during this interval as proposed elsewhere before. There is a sharp decrease in all trace fossil proxies across the Aeronian-Telychian boundary, indicating a resetting of biotic recovery back to initial stages, most likely linked to a re-onset of anoxia in shallow marine settings during the late Aeronian Event. Subsequent recovery generally followed the patterns of late Aeronian, but was hampered by a low nutrient supply during early Telychian. By the beginning of middle Telychian, a full recovery was achieved, ca. 8.8 Ma after the second pulse of the LOME.

KEYWORDS:

• Early Silurian
• benthic ecosystems
• trace fossils
• anoxia
• the late Aeronian Event

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This study is financially supported by [the National Key Research and Development Program] under grant [number 2022YFF0800200]; [State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan] under grant [number GBL22002]; [Strategic Priority Research Program of Chinese Academy of Sciences] under grant [number XDB26000000]; and [National Natural Science Foundation of China] under grant [number 42172003]. The comments from the reviewers (Professor Jisuo Jin of Western University and an anonymous reviewer) greatly helped improve this contribution.