The interpretation and highlights on mitigation of climate change in IPCC AR6 WGIII report北大核心CSCD

2022年4月4日,IPCC第六次评估报告第三工作组《气候变化2022:减缓气候变化》报告和决策者摘要发布。报告全面评估了2010年以来减缓气候变化领域的最新科学进展,为国际社会深度认识和理解全球温室气体排放情况、不同温升水平下的减排路径以及可持续发展背景下的气候变化减缓和适应行动等提供了重要科学依据。基于报告主要结论,围绕温室气体排放的区域差异、减缓路径分类、与土地利用相关的排放评估及CO去除技术评估等方面的亮点,文中提出在应对气候变化减缓政策行动中,中国应坚定“双碳”战略目标,在综合考虑经济发展阶段和资源禀赋差异背景下,将可持续发展、公平和消除贫困植根于社会发展愿景中实施减缓路径,并加快提升气候变化综合评估核心科学技术的研发进度,以进一步提升国际影响力和话语权。     

Radio observations of the 1968 September solar eclipse

This paper summarizes the analysis of the radio observations of the solar eclipse at wavelengths 3.2, 11.1 and 21 cm in Xinjiang, on 1968 Sept. 22. From the observations, we have determined the flux densities, angular diameters and heights of the localized radio sources on the solar disk, circumstances of the radio eclipse, equivalent radius of the radio Sun and certain features of a small radio burst that occurred during the eclipse. We have also investigated the correlation between the flux density of the localized sources and the activity of the active regions, as measured by the integrated brightness of plages and the sunspot area.     

辽东半岛早元古宙枕状熔岩特征

辽东半岛枕状熔岩位于辽河群大石桥组底部的变质基性岩中。呈椭球状个体,具白色硅铝质外壳。岩枕分带明显,由外向内可分为枕壳、冷凝边、枕内相。枕状熔岩的岩石学、岩石化学和地球化学研究表明,它是海底玄武岩的产物。枕状熔岩的发现为揭示广泛发育于辽东半岛早元古宙变质基性岩的成因提供了证据。     

黑龙江黄松群碎屑锆石LA-ICP-MSU-Pb定年

对黑龙江省东部敦—密断裂以南的太平岭边缘隆起带上的黄松群杨木组石榴黑云片岩和阎王殿组黑云石英片岩进行了锆石LA-ICP-MS U-Pb测年,结果表明:杨木组石榴黑云片岩中锆石~(206)Pb/~(238)U加权平均峰值年龄分别为281.8 Ma、317.2 Ma、424.7 Ma、529.3 Ma;阎王殿组黑云石英片岩中锆石~(206)Pb/~(238)U加权平均峰值年龄分别为310.4 Ma、384.4 Ma、484.7 Ma;两个组所获得的最年轻的锆石~(206)Pb/~(238)U年龄分别为280±4 Ma和285±8 Ma。此外,前人对黄松群研究结果表明其变质作用时代为晚二叠世—早三叠世。因此,黄松群时代为二叠纪,海西期和加里东期岩浆岩构成了黄松群沉积物源的主体。     

A new bird track,Koreanaornis lii ichnosp. nov., from the Lower Cretaceous Hekou Group in the Lanzhou-Minhe Basin,Gansu, Northwest China,and implications for Early Cretaceous avian diversity

There are a growing number of Early Cretaceous avian tracks and trackways from around the world, with Asia (China and Korea) having the largest reported number and diversity of Mesozoic avian traces to date, and these new discoveries are increasing the Early Cretaceous avian ichnodivesrity of Laurasia. Here we report on a new Lower Cretaceous avian track locality in the Guanshan area, Yongjing County, Gansu Province, northwest China, and on a novel ichnospecies of Koreanaornis, Koreanaornis lii ichnosp. nov. Koreananornis lii is distinct from other Koreanaornipodidae in that it possesses a consistently wider digit divarication than previously described tridactyl tracks, and possess a short, small, posteromedially oriented hallux that displays a different orientation than that seen in Koreanaornis hamanensis. The lack of linear and angular data reported for digit I traces of many avian ichnotaxa has the potential to give misleading results in multivariate statistical analyses. Also, the wide divarication of Koreanaornis lii causes the ichnotaxon to not group with other Koreanornipodidae in multivariate analyses, but with Ignotornidae. Despite the results of the analyses, K. lii is morphologically distinct from these ichnotaxa. The results demonstrate that relying solely on multivariate statistical analyses without careful examination of footprint morphology will result in erroneous ichnospecies groupings. While new vertebrate ichnotaxa discoveries from Asia may support the hypotheses of the presence of a unique and endemic Asian vertebrate ichnofauna during the Cretaceous, the recent discovery of skeletal remains interpreted to be of a volant wading bird from the Early Cretaceous, and recent reports of tracks from volant avians, could suggest that flighted avians of the shore- and wading bird ecotypes could have had a Laurasian-wide distribution during the Early Cretaceous. However, strong convergence in foot morphology of shore- and wading birds suggests that avian ichnotaxa found in both present-day Asia and North America may have been made by birds endemic to eastern and western Laurasia during the Early Cretaceous.     

Taphofacies of Lower-Middle Pennsylvanian marine invertebrates from the Monte Alegre and Itaituba formations,part of the outcropped marine sequence of the Tapajós Group (Southern Amazonas Basin,Brazil) – regional palaeoecological models

One of the most relevant characteristics of the Pennsylvanian shallow-water carbonates of the Amazonas Basin is its diverse and well preserved invertebrate fossiliferous assemblages. In order to better understand the origin of these fossil concentrations, taphonomic data were obtained along well exposed areas of the uppermost part of the Monte Alegre Formation and basal part of the Itaituba Formation, which, based on conodonts, fusulinids and palynomorphs is of Atokan age. The taphonomic data focused on invertebrate organisms were supported by petrographic analysis. The understanding of the stacking pattern of the strata in the studied section allowed the identification of five type taphofacies, which contributed in the development of regional palaeoecological models, expressed as block-diagrams. These characterize the distribution of the environmental parameters, the composition of the faunal associations and the distribution and amplitude of the taphonomic processes that created the taphonomic signatures of the bioclastic elements throughout the supratidal to lower intertidal/deep subtidal depositional environments pertinent to the studied depositional environment. The regional palaeoecological models here presented are related to the particularities of the depositional environments of the studied rocks and are exclusive for the characterization of this intracratonic basin set influenced by high frequency climatic variations. Lithofacies, biofacies and taphofacies associations also reflect depositional conditions pertinent to the studied regional context, differing from the elements observed in modern intracratonic contexts analogous to the one studied, from different sedimentary basins around the world. Therefore, invertebrate taphonomy, supported by the analysis of sedimentary facies, fulfills the purposes recommended in this work, demonstrating its potential as a tool for palaeoecological analysis in the Pennsylvanian outcropping section in the southern platform of the Amazonas Basin.     

Global correlation of the Vazante Group, São Francisco Basin, Brazil: Re–Os and U–Pb radiometric age constraints

The Vazante Group consists of Precambrian carbonate-dominated platform deposits that extend along more than 300 km in the external zone of the Brasilia Fold Belt of the São Francisco Basin in east central Brazil. The sequence is about 4.8 km thick and contains a preserved glaciomarine diamictite unit (containing dropstone) at the top and a lower diamictite unit at the bottom. Previous C- and Sr-isotope profiles suggested the correlation of the upper diamictite unit with the “Sturtian” glacial event (ca. 750–643 Ma). However, new Re–Os isotope data from the shales associated with the upper diamictites yield radiometric age estimates between 993 ± 46 and 1100 ± 77 Ma. U–Pb measurements on a suite of clear euhedral zircon crystals that were separated from the same shales associated with the upper diamictite and from the arkosic sandstone above the lower diamictite yield ages as young as 988 ± 15 and 1000 ± 25 Ma, respectively. Based on the Re–Os and U–Pb ages, the best age estimate of the Vazante Group is constrained to be 1000–1100 Ma and thus the two diamictite units are not correlative with the Sturtian glaciation(s) but most likely are records of glacial events that occurred during the late Mesoproterozoic.     

Geochemistry of fine-grained clastic sedimentary rocks of the Neoproterozoic Ikorongo Group, NE Tanzania: Implications for provenance and source rock weathering

The Neoproterozoic Ikorongo Group, which lies unconformably on the late Archaean Nyanzian Supergroup of the Tanzania Craton, is comprised of conglomerates, quartzites, shales, siltstones, red sandstones with rare flagstones and gritstones and is regionally subdivided into four litho-stratigraphic units namely the Makobo, Kinenge, Sumuji and Masati Formations.We report geochemical data for the mudrocks (i.e., shales and siltstones) from the Ikorongo basin in an attempt to constrain their provenance and source rock weathering. These mudrocks are compositionally similar to PAAS and PS indicating derivation from mixed mafic–felsic sources. However, the siltstones show depletion in the transition elements (Cr, Ni, Cu, Sc and V) and attest to a more felsic protolith than those for PAAS and PS. The Chemical Index of Alteration (CIA: 52–82) reveal a moderately weathered protolith for the mudrocks. The consistent REE patterns with LREE-enriched and HREE-depleted patterns ((La/Yb)_CN = 7.3–38.3) coupled with negative Eu anomalies (Eu/Eu* = 0.71 on average), which characteristics are similar to the average PAAS and PS, illustrate cratonic sources that formed by intra-crustal differentiation.Geochemical considerations and palaeocurrent indications suggest that the provenance of the Ikorongo Group include high-Mg basaltic-andesites, dacites, rhyolites and granitoids from the Neoarchaean Musoma-Mara Greenstone Belt to the north of the Ikorongo basin. Mass balance calculations suggest relative contributions of 47%, 42% and 11% from granitoids, high-magnesium basaltic-andesites and dacites, respectively to the detritus that formed the shales. Corresponding contributions to the siltstones detritus are 53%, 43% and 4%.     

Measuring and adjusting the weathering and hydraulic sorting effects for rigorous provenance analysis of sedimentary rocks: a case study from the Jurassic Ashikita Group,south‐west Japan

The present study examines the provenance of the Jurassic Ashikita Group distributed in south‐west Japan, which is composed of the Idenohana, Kyodomari and Sakamoto Formations. Two geochemical diagrams for provenance analysis were utilized, which incorporate full consideration of compositional modifications resulting from weathering (MFW diagram) and hydraulic sorting processes (SiO₂/Al₂O₃–Na₂O/K₂O diagram). The MFW diagram delineates weathering trends of sedimentary rocks and allows estimation of the original source rock composition by tracing the weathering trends backwards to an unweathered domain. Weathering trends of the Idenohana and Kyodomari Formations extend backward to the domain of intermediate and felsic igneous rocks. In contrast, sediments of the Sakamoto Formation do not fit into a linear weathering trend, indicating that the source rock cannot be approximated to igneous rocks. On the SiO₂/Al₂O₃–Na₂O/K₂O diagram, sediments are organized into compositional trends, in which the range reflects compositional variations induced by the hydraulic sorting effect. On this diagram, sediments derived from the igneous and recycled sedimentary provenances can be distinguished by reading the inclination of the trend. By utilizing this principle, source rocks of the Idenohana and Kyodomari Formations are interpreted as igneous rocks and those of the Sakamoto Formation are interpreted as recycled sedimentary rocks. Therefore, these diagrams concurrently estimate the source rock composition through quantifying and adjusting the weathering and sorting effects, and reveal a systematic transition in the provenance of the Ashikita Group. The Idenohana and Kyodomari Formations were supplied chiefly from an igneous provenance, which shifted from intermediate to felsic compositions in stratigraphic order. Whereas, sediments of the Sakamoto Formation were sourced primarily from a recycled sedimentary provenance.