Respiratory protein-driven selectivity during the Permian-Triassic mass extinction

Extinction selectivity determines the direction of macroevolution,especially during mass extinction;however,its driving mechanisms remain poorly understood.By investigating the physiological selectivity of marine animals during the Permian-Triassic mass extinction,we found that marine clades with lower O2-carrying capacity hemerythrin proteins and those relying on O2 diffusion experienced significantly greater extinction intensity and body-size reduction than those with higher O2-carrying capacity hemoglobin or hemocyanin proteins.Our findings suggest that animals with high O2-carrying capacity obtained the necessary O2 even under hypoxia and compensated for the increased energy requirements caused by ocean acidification,which enabled their survival during the Permian-Triassic mass extinction.Thus,high O2-carrying capacity may have been crucial for the transition from the Paleozoic to the Modern Evolutionary Fauna.

Phanerozoic oceanic and climatic perturbations in the context of Tethyan evolution

Climatic and environmental conditions play a pivotal role in the evolution of the biosphere,serving as the primary natural factors influencing biological evolution and the development of human civilization.The study of the evolution of Earth's habitability primarily revolves around the reconstruction of climatic and oceanic conditions in geohistorical periods,shedding light on their dynamic changes.This paper collates classic geological indicators and geochemical proxies associated with paleoclimatic and oceanic environmental conditions.The latest“big data”analyses and simulations made possible by the availability of previously unimagined massive datasets reveal several key findings:During the early Paleozoic,atmospheric oxygen levels were low,and widespread oceanic anoxia was prevalent;the Devonian era witnessed a greenhouse climate,followed by the Carboniferous ice age characterized by higher oceanic oxidation levels and alkalinity.The latest Paleozoic deglaciation occurred under high pCO_(2) conditions,extending into much of the Mesozoic and early Cenozoic,marked by multiple hyperthermal and anoxia expansion events,until the resurgence of global glaciation in the middle-late stages of the Cenozoic,ultimately bringing environmental and climatic conditions closer to modern levels.By correlating the aforementioned long-term trends with major geological events,we can delineate the co-evolution of paleoclimate and oceanic environments in tandem with the development of Tethys tectonics as follows.(1)During the Proto-Tethys stage,global paleo-elevations were relatively low,and atmospheric oxygen levels were also relatively modest.Despite the occurrence of significant tectonic movements that led to noticeable transgressive-regressive cycles,their effects on climate and oceanic environments were somewhat limited due to the relatively weak interactions.(2)The emergence of the Paleo-Tethys was a significant event that coincided with the formation of the supercontinent Pangaea.Intensive orogenic movements during this period increased the global land area and elevation.This,in turn,led to enhanced terrestrial weathering,which elevated sea surface productivity and resulted in massive nutrient input into the oceans.Consequently,this process contributed to the rise of oxygen levels in the atmosphere and a decrease in atmospheric pCO_(2).These changes are considered potential driving mechanisms for late Paleozoic glaciation and oceanic oxygenation.(3)The transition from the Paleo-Tethys to the Neo-Tethys was closely linked to the breakup of Pangaea.During this period,the terrestrial weathering processes were relatively weak due to decreased continental elevations.This resulted in a long-term greenhouse climate and intermittent global oceanic events,which were responses to the high atmospheric pCO_(2) levels during the Mesozoic and early Cenozoic eras.(4)The Neo-Tethys stage ended with the dramatic uplift of the Alps-Himalaya Mountain ranges due to the collision of India and Asia.This uplift had a profound global impact,significantly increasing continental elevations.As a result,weathering and carbon burial processes intensified,leading to a reduction in atmospheric pCO_(2).Concurrently,this uplift played a crucial role in the establishment of the East Asian monsoon and North Atlantic deep-water circulations,both of which played a part in triggering the late Cenozoic ice age.These models suggest that the teleconnections between land and sea(orogeny-terrestrial weathering-marine carbon burial)span over the whole Phanerozoic and might have played a key role in balancing the Earth surface system.Combined,the tectonic,volcanic,paleo-climatic,as well as paleoenvironmental events recorded in the Tethys oceans and adjunct continents represent valuable natural experiments and lessons for understanding the present and the future of Earth's habitability.

Triassic integrative stratigraphy and timescale of China

The Triassic rocks are widespread in China, and both marine and terrestrial strata are well developed. The Triassic stratigraphic architecture of China is very complex in both spatial variation of the so-called "South Marine and North Continental", i.e. the southern areas of China occupied mostly by marine facies while the northern China by terrestrial facies during the Triassic Period, and temporal transition of the "Lower Marine and Upper Continental", i.e. the lower part of the Triassic System composed mainly of marine facies and the upper part of terrestrial strata especially in South China. Although the Global Stratotype Section and Point(GSSP) of the Permian-Triassic boundary is located in South China, the Triassic of China except for some marine Lower-Middle Triassic depositions shows significantly local characteristics and is hardly correlated with the global chronostratigraphic chart. Consequently, the Triassic of China contains not only the international research hotspots but also difficult points in stratigraphic study. This paper aims to present a brief review of the Triassic in China, including chronostratigraphy, biostratigraphy, magnetostratigraphy and chemostratigraphy, and summarize an integrated Triassic stratigraphic framework of China. Accordingly, a stratigraphic correlation is proposed for the lithostratigraphic sequences among the three tectono-paleogeographic stratigraphic regions. The comprehensive study indicates that ammonoids are the classic index fossils in Triassic biostratigraphy but conodonts are more advantageous in the study and definition of the Triassic chronostratigraphic boundaries. China still has the potential to optimize the GSSPs of the Induan-Olenekian boundary and Olenekian-Anisian boundary. The correlation of the Permian-Triassic boundary between marine and terrestrial facies might be achieved with the help of the Permian-Triassic "transitional bed" and its related biotic and environmental events in association with the biostratigraphic study of conchostracan, vertebrate and plant fossils. In addition, the carbon isotopes have been proved to be one of the powerful methods in marine Triassic stratigraphic study, whereas the oxygen and strontium isotopes may be additional important bridges to establish the correlation between the marine and terrestrial strata, but as yet lacking of relevant studies in terrestrial strata. Considering the most stratigraphic intervals of the Triassic and the terrestrial Triassic in China are difficult to be correlated to the global chart, the proposed Chinese(regional) Triassic chronostratigraphic chart of marine and terrestrial stages would be of importance to the study of Chinese Triassic stratigraphy and related aspects, but the stages must be conceptually in line with international standards and studied as soon as possible in order to finalize the definition.

Seawater Temperature and Dissolved Oxygen over the Past 500 Million Years

Ocean temperature and dissolved oxygen concentrations are critical factors that control ocean productivity, carbon and nutrient cycles, and marine habitat. However, the evolution of these two factors in the geologic past are still unclear. Here, we use a new oxygen isotope database to establish the sea surface temperature(SST) curve in the past 500 million years. The database is composed of 22 796 oxygen isotope values of phosphatic and calcareous fossils. The result shows two prolonged cooling events happened in the Late Paleozoic and Late Cenozoic, coinciding with two major ice ages indicated by continental glaciation data, and seven global warming events that happened in the Late Cambrian, Silurian–Devonian transition, Late Devonian, Early Triassic, Toarcian, Late Cretaceous, and Paleocene–Eocene transition. The SSTs during these warming periods are about 5–30 °C higher than the present-day level. Oxygen contents of shallow seawater are calculated from temperature, salinity, and atmospheric oxygen. The results show that major dissolved oxygen valleys of surface seawater coincide with global warming events and ocean anoxic events. We propose that the combined effect of temperature and dissolved oxygen account for the long-term evolution of global oceanic redox state during the Phanerozoic.

Rapid Carbonate Depositional Changes Following the Permian-Triassic Mass Extinction: Sedimentary Evidence from South China

Various environmental changes were associated with the Permian-Triassic mass extinction at 252.2 Ma. Diverse unusual sediments and depositional phenomena have been uncovered as responses to environmental and biotic changes. Lithological and detailed conodont biostratigraphic correlations within six Permian-Triassic boundary sections in South China indicate rapid fluctuations in carbonate deposition. Four distinct depositional phases can be recognized： （1） normal carbonate deposition on the platform and slope during the latest Permian; （2） reduced carbonate deposition at the on- set of the main extinction horizon; （3） expanded areas of carbonate deposition during the Hindeodus changxingsensis Zone to the H. parvus Zone; and （4） persistent mud-enriched carbonate deposition in the aftermath of the Permian-Triassic transition. Although availability of skeletal carbonate was significantly reduced during the mass extinction, the increase in carbonate deposition did not behave the same way. The rapid carbonate depositional changes, presented in this study, suggest that diverse environmental changes played key roles in the carbonate deposition of the Permian-Triassic mass extinction and onset of its aftermath. An overview of hypotheses to explain these changes implies enhanced terrestrial input, abnormal ocean circulation and various geobiological processes contributed to carbonate saturation fluctuations, as the sedimentary response to large volcanic eruptions.