Volcanism at the Permian-Triassic Boundary in South China and Its Effects on Mass Extinction

This paper discusses the clayrocks widespread at the Permian-Triassic boundary, which are mostly of volcanic origin. Volcanogenetic textures, structures and minerals such as high-temperature quartz are found in clayrocks at the Permian-Triassic boundary in many places. Thousands of microspherules have been collected from the Boundary clayrocks, many of which exhibit the typical features of the process from melting to cooling and solidification. indicating that they were formed by volcanic eruption or extraterrestrial impact. Volcanic effects on the Permian-Triassic mass extinction may be reflected in conodonts, algae and ammonoids. The Boundary clayrocks are found in many Permian-Triassic sections along the coast of Tethys. Their orighin remains to be studied.

Determination of aerosol extinction coefficient and mass extinction efficiency by DOAS with a flashlight source

With the method of differential optical absorption spectroscopy （DOAS）, average concentrations of aerosol particles along light path were measured with a flashlight source in Chiba area during the period of one month. The optical thickness at 550 nm is compared with the concentration of ground-measured suspended particulate matter （SPM）. Good correlations are found between the DOAS and SPM data, leading to the determination of the aerosol mass extinction efficiency （MEE） to be possible in the lower troposphere. The average MEE value is about 7.6m^2.g^-1 , and the parameter exhibits a good correlation with the particle size as determined from the wavelength dependence of the DOAS signal intensity.

Stratigraphical Time——Correlation and Mass Extinction Event Near Permian——Triassic Boundary in South China

Shaw's method used to correlate 40 sections across the Permo-Triassic boundary in South China is applied in the paper. Two steps are adopted to get an Integral Composite Section (ICS) by synthesizing these data : First , South China is divided into five areas and composite section developed for each area . Then the second step . the Changxing composite section is regarded as a composite standard (CSRS) while the ICS is produced by matching the CSRS with composite sections of the other areas. Three biozones in the Changxingian and two biozones in the Griesbachian can be discerned on the basis of computing Z values in the ICS. These biozones are marked by the Z values which quantitatively represent their time ranges ; therefore , they may increase accuracy of stratigraphic time correlation . The mass extinction at the end of the Permian is an abrupt event that is supported by the relative rate of extinction near the P/T boundary . About 90% of invertebrate species died out by the end of the Permian . The duration of the mass extinction is rather short ,approximately 0.018Ma .

Combination Features,Paleobiogeographic Affinity and Mass Extinction of the Latest Ordovician(Hirnantian) Rugosan Fauna from Northern Guizhou,China

The rugosan fauna from the Guanyinqiao Bed （latest Ordovician, Hirnantian） of northern Guizhou, China is known to belong to the cold or cool-water type corals. The components of the fauna are solitary corals only, and corallite septa are generally strongly dilated, especially the streptelasmatid corals are dominant comprising 98% of the whole fauna. The Guanyinqiao Bed is rich in rugosans of 18 genera, which are streptelasnmtid Streptelasma （=Helicelasma）, Brachyelasma, Amplexobrachyelasma, Salvadorea, Grewingkia, Borelasma, CrassUasma, Leolasma, KenophyUum, UUernelasma, Paramplexoides, Siphonolasma, Pycnactoides, Dalmanophyllum, Bodophyllum, Axiphoria, Lambeophyllum and cystiphyllid Sinkiangolasma. Although this fauna was fairly abundant in a confined area （northern-northeastern Guizhou, southern Sichuan） during the Hirnantian age, the rugosan mass extinction （generic extinction rate 81%） happened at the end of the Hirnantian Stage. It is conduded that the mass extinction is related to the ending of maximum glaciation and ice cap melting in Gondwana in the southern hemisphere in the latest Hirnantian, resulting in rapid global sea-level rise in the earliest Silurian. In the Upper Yangtze Basin, the sea bottom environments were replaced by anoxic and warmer water during that time, so that the cool-water type rugosan became extinct. The present paper attempts to revise some already described rugose coral genera and species （He, 1978, 1985） and to supplement a few new forms from the Guanyinqiao Bed. Fourteen species of 12 genera are re-described and illustrated, of which one species- Grewingkia latifossulata is new. As a whole, the rugosan fauna of the Guanyinqiao Bed may be correlated with those contemporaneous of North Europe, Estonia and North America, indicating a dose biogeographic affinity to North Europe.

Late Ordovician mass extinction caused by global warming or cooling?

The Late Ordovician mass extinction(LOME)was the first global extinction with the destruction of 85%of marine species.However,the cause of LOME is still controversial.Most studies attribute it to large-scale volcanism caused by global cooling or warming.Through analyzing the driving difference between global cooling and warming on large-scale magmatism,the perspective is intended to evoke a hot discussion on the cause of LOME.Did global cooling or warming trigger the LOME?

Law of Physics 20^th-Century Scientists Overlooked (Part 4): Mass Extinction by Aether Deprivation

Extreme gravitational collapse is explored by utilizing two fundamental properties and one reasonable assumption, which together lead logically to an end-state gravitating structure. This structure, called a Terminal state neutron star, manifests nature’s ultimate density of mass and possesses the ultimate electromagnetic barrier. It is then shown how this structure is central to the remarkable mechanism whereby the density is prevented from going higher. A simple process assures that such density is not exceeded—regardless of the quantity of additional mass. As an example, the discourse focuses on the expected progression and outcome when a compact star of —far more mass than can be accommodated by the basic Terminal state structure—undergoes total gravitational collapse. An examination of what happens to the considerable excess mass leads the discussion to the principle of mass extinction by the process of aether deprivation and its profound implications for black-hole physics and the current revolution in cosmology.

A Speculation: Avian Migration and the K-T Extinction

One caveat to the dinosaur’s extinction is the conclusion that avian dinosaurs survived and became ancestors of birds. Their mobility enabled them to migrate great distances and find the nutrients needed to survive. Given this scenario, could the current observable migration of birds (the “dinosaurian offspring”) now be related? Migration is the regular seasonal movement undertaken by many species of birds, with the most common pattern, flying north in the Northern spring to breed in the temperate or Arctic summer and returning in the Northern autumn to wintering grounds in warmer regions of the south. The primary motivation for migration appears to be food. None of the major North-South migratory pathways fly over the Caribbean but three main fly ways, past to the west of the theorized K-T impact centre. Due to their ability to fly, the “avian Dinosaurs” adapted and survived very quickly in response to the disaster that marked the K-T boundary. It is an interesting speculation that the avian migration that we witness today is rooted in an event that occurred 66 million years ago! But it does explain why the migratory birds mostly fly from Polar summer to polar summer when they could just be as easily fly from Polar zone to the warmer equatorial region and back. In the recent article in Nature by Melanie During about identifying the late spring timing of the “Astro disaster”, it can be cited as consistent with my speculation. A late April early May Impact as suggested by During would have seen these migrations completely. The western migratory routes would have been found to be “luxurious” in vegetation in that first northern autumn after the “Astro-impact” while all eastern routes would have still been barren.

Permian–Triassic Conodonts from Dajiang(Guizhou, South China) and Their Implication for the Age of Microbialite Deposition in the Aftermath of the End-Permian Mass Extinction

The widespread microbialites deposition that followed the End-Permian mass extinction in the Tethyan realm have been intensively studied because of the evidence they provide on the nature of this crisis and its aftermath. However, the age of the microbialite event remains controversial. New conodont collection across the Permian–Triassic（P–T） transition from Dajiang（Guizhou Province, South China） in this study enable us to discriminate four conodont zones, in ascending order, they are： Hindeodus parvus zone, Isarcicella lobata zone, Isarcicella isarcica zone and Hindeodus sosioensis zone. The age of microbialite in the P–T transition at the Dajiang Section is considered to be within the Hindeodus parvus zone and thus to clearly post-date the main extinction crisis. Reviewing the age of onset of microbialites throughout the Tethyan regions reveals two different ages： a Hindeodus changxingensis zone age is dominant in south-western and westernmost Tethys, whilst most other regions show microbialite deposition began in the Hindeodus parvus zone. Our investigation also indicates that two conodont changes occur at this time： an increase of hindeodid species immediately following a sequence boundary and the mass extinction, and a phase of extinction losses in the earliest Triassic Isarcicella isarcica zone during highstand development.

Mass extinction and Pangea integration during the Paleozoic-Mesozoic transition

The greatest Phanerozoic mass extinction happened at the end-Permian to earliest Triassic. About 95% species, 82% genera, and more than half families became extinct, constituting the sole macro-mass extinction in geological history. This event not only caused the great extinction but also destroyed the 200 Myr-long Paleozoic marine ecosystem, prompted its transition to Mesozoic ecosystem, and induced coal gap on land as well as reef gap and chert gap in ocean. The biotic crisis during the Paleozoic-Mesozoic transition was a long process of co-evolution between geospheres and biosphere. The event sequence at the Permian-Triassic boundary （PTB） reveals two-episodic pattern of rapidly deteriorating global changes and biotic mass ex- tinction and the intimate relationship between them. The severe global changes coupling multiple geospheres may have affect- ed the Pangea integration on the Earth＇s surface spheres, which include： the Pangea integration→enhanced mountain height and basin depth, changes of wind and ocean current systems; enhanced ocean basin depth→the greatest Phanerozoic regression at PTB, disappearance of epeiric seas and subsequent rapid transgression; the Pangea integration→thermal isolation effect of continental lithosphere and decrease of mid-ocean ridges→development of continental volcanism; two-episode volcanism causing LIPs of the Emeishan Basalt and the Siberian Trap （25%251 Ma）→global warming and mass extinction; continental aridification and replacement of monsoon system by latitudinal wind system→destruction of vegetation; enhanced weathering and CH4 emission→negative excursion of δ^13C; mantle plume→crust doming→regression; possible relation between the Illawarra magnetic reversal and the PTB extinction, and so on. Mantle plume produced the Late Permian LIPs and mantle convection may have caused the process of the Pangea integration. Subduction, delamination, and accumulation of the earth＇s cool lithospheric material at the ＂D＂ layer of CMB started mantle plume by heat compensation and disturbed the outer core ther- too-convection, and the latter in turn would generate the mid-Permian geomagnetic reversal. These core and mantle perturbations may have caused the Pangea integration and two successive LIPs in the Permian, and probably finally the mass extinction at the PTB.

The large increase of δ^(13)C_(carb)-depth gradient and the end-Permian mass extinction

Carbonate carbon isotope （δ^13Ccarb） has received considerable attention in the Permian-Triassic transition for its rapid negative shift coinciding with the great end-Permian mass extinction event. The mechanism has long been debated for such a c~ δ^13Ccarb negative excursion through the end-Permian crisis and subsequent large perturbations in the entire Early Triassic. A δ^13Ccarb depth gradient is observed at the Permian-Triassic boundary sections of different water-depths, i.e., the Yangou, Meishan, and Shangsi sections, and such a large δ^13Ccarb-depth gradient near the end-Permian mass extinction horizon is believed to result from a stratified Paleotethys Ocean with widespread anoxic/euxinic deep water. The evolution of δ^13Ccarb-depth gradient com- bined with paleontological and geochemical data suggests that abundant cyanobacteria and vigorous biological pump in the immediate aftermath of the end-Permian extinction would be the main cause of the large δ^13Ccarb-depth gradient, and the enhanced continental weathering with the mass extinction on land provides a mass amount of nutriment for the flourishing cyanobacteria. Photic zone anoxia/euxinia from the onset of chemocline upward excursion might be the direct cause for the mass extinction whereas the instability of chemocline in the stratified Early Triassic ocean would be the reason for the delayed and involuted biotic recovery.

Carbon-Isotope Excursions Recorded in the Cambrian System,South China:Implications for Mass Extinctions and Sea-Level Fluctuations

Cambrian carbonates with abundant fossils of agnostoid trilobites deposited on the southern slope （Jiangnan slope belt） of the Yangtze Platform and in the Jiangnan deepwater basin are well exposed in the Wangeun Section of western Hunan, South China, and in the Duibian A Section of western Zhejiang, southeastern China, respectively. To better understand the response of carbonisotope excursions to depositional environment changes, mass extinctions and eustatic events, we collected 530 carbonate samples in fresh roadcut exposures of the two measured sections for analysis of carbon and oxygen isotopic compositions. Data of δ^13C from the Wangcun Section, western Hunan, South China, demonstrate that the Cambrian carbon-isotope profile includes three remarkable positive excursions CPEwc-1, 2, 3 in the Upper Series 2, in the Lower and in the Middle Furongian Series. Three distinctive negative excursions CNEwc,-1, 2, 3 were separately tested in the Lower Terreneuvian Series, Lower Series 3 and in the Upper Furongian Series. Similarly, in the corresponding horizons in the Duibian A Section, Zhejiang Province, southeastern China, three positive excursions CPEdb-1, 2, 3 and three negative excursions CNEdb-1, 2, 3 also have been discovered. We interpret these significant carbon-isotope excursions as being associated with enhanced biogenic prodnctivity, mass extinctions and eustatic events.

End-Guadalupian mass extinction and negative carbon isotope excursion at Xiaojiaba,Guangyuan,Sichuan

The end-Paleozoic biotic crisis is characterized by two-phase mass extinctions;the first strike,resulting in a large decline of sessile benthos in shallow marine environments,occurred at the end-Guadalupian time.In order to explore the mechanism of organisms' demise,detailed analyses of depositional facies,fossil record,and carbonate carbon isotopic variations were carried out on a Maokou-Wujiaping boundary succession in northwestern Sichuan,SW China.Our data reveal a negative carbon isotopic excursion across the boundary;the gradual excursion with relatively low amplitude(2.15‰) favors a long-term influx of isotopically light 12 C sourced by the Emeishan basalt trap,rather than by rapid releasing of gas hydrate.The temporal coincidence of the beginning of accelerated negative carbon isotopic excursion with onsets of sea-level fall and massive biotic demise suggests a cause-effect link between them.Intensive volcanic activity of the Emeishan trap and sea-level fall could have resulted in detrimental environmental stresses and habitat loss for organisms,particularly for those benthic dwellers,leading to their subsequent massive extinction.

The microfacies and sedimentary responses to the mass extinction during the Permian-Triassic transition at Yangou Section, Jiangxi Province, South China

A Permian-Triassic(P-Tr) boundary section of continuous carbonate facies, which well recorded the biotic and environmental processes through the great P-Tr transition in the shallow non-microbialite carbonate facies, has been studied in Yangou, Leping County, Jiangxi Province. The P-Tr sequence is well correlated with the Meishan section according to the conodont biostratigraphy and the excursion of carbon isotopes. A series of high-resolution thin-sections from the P-Tr boundary carbonate rocks at the Yangou section are studied to explore the interrelation between environmental change and biological evolution during the transitional time. Six microfacies have been identified based upon the observation of the thin-sections under a microscope on the grains and matrix and their interrelation. Combined with the data of fossils and carbon isotopes, Microfacies 4(MF-4), coated-grain-bearing foraminifer oolitic sparitic limestone, and Microfacies 6(MF-6), dark shelly micritic limestone, should be the different responses to the two episodes of mass extinction and environmental events that can be correlated throughout South China and even over the world. The oolitic limestone of MF-4 is the first finding from the latest Permian strata in South China and it might be a proxy of an unusual environmental condition of high pCO2, low sulfate concentration and of microbial blooming in the aftermath of the latest Permian mass extinction. The micritic limestone of MF-6 containing rich micro-gastropods and ostracods probably represents the blooming event of disaster taxa in the earliest Triassic environment. The microfacies analysis at the Yangou section can well reveal the episodic process of the biological evolution and environmental change in the shallow non-microbialite carbonate facies throughout the great P-Tr transition, thus the Yangou section becomes an important complement to the Meishan section.

Coevality of the sea-level fall and main mass extinction in the Permian-Triassic transition in Xiushui, Jiangxi Province, southern China

A continuous Permian-Triassic boundary （PTB） section has been found and studied for the first time in Xiushui, Jiangxi Province, South China. Evidence for a large sealevel fall has been found in the horizon of 0.8 m below the PTB, from the beginning of Hindeodus changxingensis zone （correlatable to Hindeodus typicalis Zone of the Meishan section）. Sedimentary record indicates that the sea level kept at Iowstand, or occasionally rose slowly during the whole Hindeodus parvus zone, except another substantial sea-level fall in early H. parvus zone. It began a quick rise from the beginning of Isarcicella staeschei zone, kept rising for the whole/, staeschei zone, and probably caused the stagnation of sea water. The first severe change in the biota, marked by the sudden disappearance of all steno- tropic organisms such as fusulinids and dasycladacians, happened at the same time as the first sea-level fall, and is regarded as the first and main episode of the end-Permian mass extinction in this area. A microbe-dominated biota followed the first extinction, and spanned the late H. changxingensis zone and the whole H. parvus zone. All the microbes and some other eurytropic organisms including gastropods and ostracods disappeared at the end of the H. parvus zone, and the following biota in the/. staeschei zone is very simple. The coevality of the main sea-level fall and the main extinction episode might be causal： both of them might be caused by a drastic climatic cooling.

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.

Palaeogeographic variation in the Permian-Triassic boundary microbialites:A discussion of microbial and ocean process esafter the end-Permian mass extinction

Shallow marine carbonate sediments that formed after the end-Permian mass extinction are rich in a thin(maximum ca.15 m) deposit of microbialites.Microbial communities that constructed the microbialites have geographic variability of composition,broadly divisible into two groups:1) eastern Tethys sites are calcimicrobe-dominated(appearing as thrombolites in the field),with rare occurrence of sedimentconstructed microbialites and uncommon cements either within microbial structure or as inorganic precipitates,2) other Tethys sites are sediment-dominated structures forming stromatolites and thrombolites,composed of micrites and cements,with some inorganic precipitates.These other Tethys locations include western and central Tethys sites but their palaeogeographic positions depend on the accuracy of continental reconstructions,of which there are several opinions.In contrast to geographic variation of microbialites,the conodont Hindeodus parvus,which appeared after the extinction and defines the base of the Triassic,is widespread,indicating easy lateral migration throughout Tethys.Conodont animals were active nekton,although being small animals were presumably at least partly carried by water currents,implying active Tethyan surface water circulation after the extinction event.Post-extinction ammonoid taxa,presumed active swimmers,show poor evidence of a wide distribution in the Griesbachian beds immediately after the extinction,but are more cosmopolitan higher up,in the Dienerian strata in Tethys.Other shelly fossils also have poorly defined distributions after the extinction,but ostracods show some wider distribution suggesting migration was possible after the extinction.Therefore there is a contrast between the geographic differences of microbialites and some shelly fossils.Determining the cause of geographic variation of post-extinction microbialites is problematic and may include one or more of the following possibilities:1) because calcifying microbial organisms that create calcimicrobes were benthic,they may have lacked planktonic stages that would have allowed migration,2)eastern Tethyan seas were possibly more saturated with respect to calcium carbonates and microbes,so microbes there were possibly more able to calcify,3) significant reduction of Tethyan ocean circulation,perhaps by large-scale upwelling disrupting ocean surface circulation,may have limited lateral migration of benthic microbial communities but did not prevent migration of other organisms,and 4) microbes may have been subject to local environmental controls,the mechanisms of which have not yet been recognized in the facies.The difficulty of distinguishing between these possibilities(and maybe others not identified) demonstrates that there is a lot still to learn about the post-extinction microbialites and their controls.

Thermoluminescence in response to the mass extinction event in Penglaitan Section in Laibin,Guangxi

Thermoluminescence(TL)in marine carbonate has been proposed as a potential proxy for reconstruction of paleoceanography history,and has already been used in defining the Quaternary environment.However,its availability in the geological time scale,such as Permian,is still on debate.The mass extinction event caused by drastic changes of global marine environment in Middle-Late Permian provides a typical example to testify the applicability of this proxy.Here we measured the natural thermoluminescence of the carbonate-dominating marine sediments collected from the strata through the Guadalupian-Lopingian mass extinction boundary(G/LB)in the Penglaitan Section in Laibin,Guangxi,China.Our results reveal that TL intensities of carbonate are much higher than those of siliceous rocks,which indicates that the carbonate is the main contributor to the TL.The variation of TL intensities are related with Mn and Fe contents in the carbonate lattices while high Mn and low Fe(e.g.,high Mn/Fe ratio)in carbonate will release stronger TL.Due to the better storage of carbonate lattices for original information of Mn and Fe in seawater,thermoluminescence of carbonate-dominating sediments/rocks could sensitively reflect marine environment and biological productivity in geological time scale.

Beef and cone-in-cone calcite fibrous cements associated with the end-Permian and end-Triassic mass extinctions： Reassessment of processes of formation

This paper reassesses published interpretation that beef and cone-in-cone （B-CIC） fibrous calcite cements were precipitated contemporaneously just below the sea floor in uncon- solidated sediment, in limestones associated with the end-Permian （P/T） and end-Triassic （T/J） mass extinctions. That interpretation introduced the concept of a sub-seafloor car- bonate factory associated with ocean acidification by raised carbon dioxide driven by volcanic eruption, coinciding with mass extinction. However, our new fieldwork and petrographic analysis, with literature comparison, reveals several problems with this concept. Two key points based on evidence in the T/J transition of the UK are： （I） that B-CIC calcite deposits form thin scattered layers and lenses at several horizons, not a distinct deposit associated with volcanic activity; and （2） B-CIC calcite is more common in Early Jurassic sediments after the extinction and after the end of the Central Atlantic Magmatic Province volcanism proposed to have supplied the carbon dioxide required. Our samples from Late Triassic, Early Jurassic and Early Cretaceous limestones in southern UK show that B-CIC calcite occurs in both marine and non-marine sediments, therefore ocean processes are not mandatory for its formation. There is no proof that fibrous calcite was formed before lithification, but our Early Jurassic samples do prove fibrous calcite formed after compaction, thus interpretation of crystal growth in uncon- solidated sediment is problematic. Furthermore, B-CIC crystals mostly grew both upwards and downwards equally, contradicting the interpretation of the novel carbonate factory that they grew preferentially upwards in soft sediment. Finally, Early Jurassic and Early Cretaceous examples are not associated with mass extinction. Three further key points derived from the literature include： （I） B-CIC calcite is wide- spread geographically and stratigraphically, not clustered around mass extinctions or the Paleocene-Eocene Thermal Maximum （PETM） event; （2） isotope signatures suggest B-CIC calcite formed under high pressure in burial at 70-120℃, incompatible with interpretation of formation of B-CIC calcite at the redox boundary below the ocean floor; and （3） B-CIC calcite reported in P/T boundary microbialites in one site in Iran is the only occurrence known despite extensive published studies of similar shallow marine settings, demon- strating its formation is localized to the Iran site. Based on the above evidence, our opinion is that B-CIC calcite is best explained as a later diagenetic feature unrelated to rapid Earth-surface environmental change associated with mass extinctions; thus a novel carbonate factory is highly unlikely.

Paleoecological Response of Corals to the End-Triassic Mass Extinction： An Integrational Analysis

The end-Triassic （also Triassic-Jurassic） mass extinction severely affected life on planet Earth 200 million years ago. Paleoclimate change triggered by the volcanic eruptions of the Central Atlantic Magmatic Province （CAMP） caused a great loss of marine biodiversity, among which 96% coral genera were get lost. However, there is precious little detail on the paleoecology and growth forms lost between the latest Triassic extinction and the Early Jurassic recovery. Here a new pilot study was conducted by analyzing corallite integration levels among corals from the latest Triassic and Early Jurassic times. Integration levels in corals from the Late Triassic and Early Jurassic were determined through both the Paleobiology Database as well as from a comprehensive museum collection of fossil corals. Results suggest that in addition to a major loss of diversity following the end-Triassic mass extinction, there also was a significant loss of highly integrated corals as clearly evidenced by the coral data from the Early Jurassic. This confirms our hypothesis of paleoecological selectivity for corals following the end-Triassic mass extinction. This study highlights the importance of assigning sim- ple to advanced paleoecological characters with integration levels, which opens a useful approach to understanding of mass extinction and the dynamics of the recovery.

Dependence of Mixed Aerosol Light Scattering Extinction on Relative Humidity in Beijing and Hong Kong

The hygroscopic properties of mixed aerosol particles are crucial for the application of remote sensing products of aerosol optical parameters in the study of air quality and climate at multiple scales. In this study, the authors investigated aerosol optical properties as a func tion of relative humidity （RH） for two representative me tropolises： Beijing and Hong Kong. In addition to the RH data, mass concentrations of PM10 （particulate matter up to 10 utm in diameter） and aerosol scattering extinction coefficient （aext） data were used. The relationship between the mass scattering extinction efficiency （MEE, defined as O＇ext/PMl0） and RH can be expressed by regression func tions asf= 1.52x ＋ 0.29 （re= 0.77）,f= 1.42x ＋ 1.53 （re= 0.58）,f= 1.19x ＋ 0.65 （re= 0.59）, andf= 1.58x ＋ 1.30 （re = 0.61） for spring, summer, autumn, and winter, respec tively, in Beijing. Here, f represents MEE, x represents I/（1-RH）, and the coefficients of determination are pre sented in parentheses. Conversely, in Hong Kong, the corresponding functions are f= 1.98x- 1.40 （r^2= 0.55）,f = 1.32x - 0.36 （r^2 = 0.26）,f= 1.87x - 0.65 （r^2 = 0.64）, and f= 2.39x - 1.47 （r^2 = 0.72）, respectively. The MEE values for Hong Kong at high RHs （RH 〉 70%） are higher than those for Beijing, except in summer; this suggests that aerosols in Hong Kong are more hygroscopic than those in Beijing for the other three seasons, but the aerosol hy groscopicity is similarly high in summer over both cities. This study describes the effects of moisture on aerosol scattering extinction coefficients and provides a potential method of studying atmospheric visibility and ground level air quality using some of the optical remote sensing products of satellites.