The Middle and Late Devonian period developed the largest lameropodium, the Coral Reef Ecosystem, covering about ten times the area of today's biological reefs. With the Extinction Events of Kellwasser at the turn of the Late Devonian and Famen Periods (F-F) and the Hangenberg extinction events at the end of the Famen period, the lameroproma-coral reef ecosystem collapsed and disappeared, respectively. The Mississippi period has long been thought to be dominated by microbial reefs, lacking the development of post-animal reefs. At present, scientists have paid attention to the recovery and evolution of Mississippiian biological reefs, the comparison of the evolutionary processes of biological reefs in different plates, and the earliest recovery time of post-mezoan reefs.
Yao Le, associate researcher of the Late Paleozoic research team at the Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, and Markus Aretz, associate professor of the University of Toulouse III in France, conducted detailed research on the late Devonian mass extinction and the evolution of biological reef ecosystems, and achieved a series of results in the composition of Mississippinian biological reefs, the process of recovery and evolution. The results were published in Earth-Science Reviews, Palaeogeography, Palaeoclimatology, Palaeoecology and The Geologic Journal.
Based on the systematic summary and study of global Late Devonian-Mississipbian biological reefs, the study reveals that after the disappearance of post-Devonian archaezoic reefs, the recovery of Mississippiian post-existing animal reefs went through three stages: the deletion stage of post-existing animal reefs in the Dune period, the reconstruction stage of epizoostem reefs from the early To early Viscien period, and the stage of coral reef ecosystem prosperity in the late Middle Viscien period (Yao et al., 2020a).
At the same time, in order to reveal whether the recovery and evolution process of The Mississippiian biological reef in China is consistent with the world, Yaole and domestic and foreign collaborators have studied in detail the stromatolites of the Montenegro Formation in front of the Pingchuan Dashuigou section in Gansu Province and the Du'an Formation of the Du'an Formation of Tianlin Ganzi in Guangxi.
Gansu Pingchuan Dashuigou laminated stone, exposed thickness of about 22.5 meters, horizontal distribution of at least 200 meters. Fossils such as ammonites, mesozoites, and pollen can determine that the age of stromatolites is early Dunet (equivalent to the lower part of the International Tooth-shaped Stone Belt Siphonodella sulcata). Stromatolites develop different morphologies such as striated, wavy and domed. The microphase technology method shows that the stromatolite is mainly composed of mud crystals, mud particles, core stones, silt and brilliant calcite, containing a small amount of coarse sand and biological detritus; three types of grain layers are developed: mud crystal layer, particle-based mixed grain layer and mud crystal-based mixed grain layer, and two forms of grain layer accumulation: repeated grain layer accumulation and alternating grain layer accumulation. The presence of granular and mud crystal-based layers in stromatolites indicates that they may be formed by the bonding, trapping, and calcification of microorganisms. It can be seen from the morphological changes of sedimentary lithofacies, microfacies and stromatolites that stromatolites are formed in the phase of relative sea level elevation and disappear due to a sharp decrease in relative sea level and enhanced land source clastic input (Yao et al., 2020b). Guangxi Tianlin Ganzi has developed a rich metaphyte-microbial reef, with a size of a few meters to tens of meters, with obvious positive uplift. The reef age was determined by foraminifera fossils as the late Viscien (equivalent to MFZ14-15 in the foraminifera belt in Western Europe). Combined with field observations and quantitative statistics of organisms and sedimentary components in indoor flakes, four reef types can be identified: coral reef, coral-microbial-question microfolium-moss reef, coral-microbial-moss reef, and microbial-lichen moss-coral reef. Reef-building organisms of reef bodies mainly include diphyphyllum , Siphonodendron ) , multithecopora ( Syringopora ) , Fistulipora , and microorganisms ( e.g. Garwoodia , Renalcis ) . After lithographic and microphysic studies, the well-developed skeleton rocks and bonded rocks in the reef body can be distinguished from the accumulated limestone, granular limestone and mud-grained limestone between the reef wing and the reef. Changes in the biological and sedimentary components of the reef and its upper and lower strata indicate that they formed during periods of relative sea level rise, and that the development of reef bodies is closely related to changes in relative sea level. The reef-building organisms and sedimentary composition of the Ganquzi reef body have similar composition to that of other plate contemporaneous reefs around the world, especially the extensive development of coral reefs (Yao and Aretz, 2020).
The emergence of early stromatolites in Dune, Pingchuan, Gansu, and late coral reefs in Tianlin Weixian in Guangxi correspond to the missing stage of animal reefs in the Dune period and the flourishing stage of coral reef ecosystems in the late Middle Weixian period, respectively, reflecting that the recovery and evolution process of china's biological reefs after the mass extinction of late Devonian organisms is consistent with the world.
Chen Jitao and Qi Yuping, researchers of the late antiquity team of nanjing institute of paleontology, Paul B. Wignall, professor of the University of Leeds, and Professors Wang Xiangdong and Shen Shuzhong of Nanjing University participated in the above research work. The research work has been funded by the National Natural Science Foundation of China, the Strategic Pilot Science and Technology Project of the Chinese Academy of Sciences (Category B), the Natural Science Foundation of Jiangsu Province and the State Key Laboratory of Modern Paleontology and Stratigraphy.
Source: Nanjing Institute of Geology and Paleontology