Based on a nearly complete lower jaw from the Early Cretaceous of Liaoning Province, a new ctenochasmatid pterosaur: Liaoxipterus brachyognathus gen. et sp. nov. is erected. Liaoxipterus brachyognathus is different fr...Based on a nearly complete lower jaw from the Early Cretaceous of Liaoning Province, a new ctenochasmatid pterosaur: Liaoxipterus brachyognathus gen. et sp. nov. is erected. Liaoxipterus brachyognathus is different from any known pterosaurs with skulls preserved from western Liaoning Province and its peripheral areas in that the anterior part of the mandibular symphysis is expanded, being widest between the fourth alveolus of each side. Liaoxipterus brachyognathus is assigned to Ctenochasmatidae based on the following characters: the rounded anterior end of the lower jaw is spatulated and dorsoventrally flattened and marked heterodonty in the dentition is absent. It differs from other ctenochasmatid pterosaurs in having relatively small number of teeth. Liaoxipterus is distinguished from some ornithocheirids, which have expanded anterior parts of the mandibular symphyses, such as Anhanguera piscator, Coloborhynchus robustus in which the teeth of the new pterosaur are not as variable.展开更多
Structural analyses show that the Ailaoshan-Red River shear zone （ASRRSZ） in Ailao Mountain is composed of three different deformational domains. These domains may represent three episodes of left-lateral slip exper...Structural analyses show that the Ailaoshan-Red River shear zone （ASRRSZ） in Ailao Mountain is composed of three different deformational domains. These domains may represent three episodes of left-lateral slip experienced by the ASRRSZ. The first episode of such deformation occurred throughout the eastern high-grade belt of the ASRRSZ under a transtensional regime and produced L- type tectonites of amphibolite grade. The second episode of left-lateral slip formed high strain zones overprinting the high-grade belt. Its deformational mechanism is similar to simple shear and the deformed rocks are L-S mylonites of greenschist grade. The third episode of left-lateral slip took place chiefly in a western low-grade belt of the ASRRSZ. This deformation occurred in a transpressional regime, formed an overall structure pattern of a sinistral thrust system and produced phyllonites of low-greenschist grade. Geochronological data indicated that the three episodes of left-lateral slip happened before ～58-56 Ma, at least from ～27 Ma to 22 Ma and at ～13-12 Ma respectively. The first episode of slip in the ASRRSZ appeared to correspond to the initial collision of India and Asia at ～60 Ma. The second episode took place almost at the same time as the most intensive compression and uplift in Tibet. The latest event might represent a further eastward material flow in Tibet after ～16-13 Ma. Thus, the ASRRSZ of southeastern Asia probably experienced three main episodes of Tertiary left- lateral slip in the course of intracontinental convergence since the India-Asia collision.展开更多
Objective Petrified wood,as an important component of plant fossils,plays a significant role in understanding the floral composition and terrestrial palaeoclimates of the geological past.Though abundant petrified wood...Objective Petrified wood,as an important component of plant fossils,plays a significant role in understanding the floral composition and terrestrial palaeoclimates of the geological past.Though abundant petrified woods have been found from the Mesozoic deposits in the Great Xing’an Range,NE China,it was rare for systematic investigations to be carried out for these fossil wood remains.展开更多
Banded iron formation and Cu-Zn sulfide deposits within volcanic-argillaceous sequences(as volcanogenic massive sulphide deposits(VMS)-like type) occur together in the Qingyuan greenstone belt of the North China Crato...Banded iron formation and Cu-Zn sulfide deposits within volcanic-argillaceous sequences(as volcanogenic massive sulphide deposits(VMS)-like type) occur together in the Qingyuan greenstone belt of the North China Craton,recording the first appearance of oxidized ores and sulfide ores co-existing in the early Earth.The unique metal co-existing deposits should meet two requirements:tectonic setting and sedimentary environment.As regards to tectonic setting,plate-like tectonics might have started since the end of the Neoarchean because continents had grown large enough and there occurred volcanic arcs and backarc basins similar to modern ones in a way.Partial melting of subducted continental crust is conductive to providing ore-forming elements.As for sedimentary environment,late Neoarchean seawater was rich in Fe^(2+) and anoxic.Instantaneous oxidation of the seawater resulted possibly from frequent submarine volcanic eruptions and facilitated precipitation of the banded iron formation.At this point,it is also favorable for the enrichment of Cu and Zn ions in seawater.The VMS-like deposits tended to form when the seawater was reduced again.Studies of isotopic elements like sulfur,oxygen,iron and silicon support the above geological processes.It is shown that the geologic conditions only existed in the late Neoarchean and Paleoproterozoic for a short period of time.The banded iron formations disappeared around 1.85 Ga,and the associated sulfide metal deposits also became dominant sedimentary exhalative deposits in the meso-Neoproterozoic Boring Billion,as a result of increasing oxidation of the oceans and the increasing maturity of the continental crust.This study is significant not only for decoding metallogenic genesis but also helping understand rapid change in Precambrian tectonic regimes and Earth’s environments.展开更多
文摘Based on a nearly complete lower jaw from the Early Cretaceous of Liaoning Province, a new ctenochasmatid pterosaur: Liaoxipterus brachyognathus gen. et sp. nov. is erected. Liaoxipterus brachyognathus is different from any known pterosaurs with skulls preserved from western Liaoning Province and its peripheral areas in that the anterior part of the mandibular symphysis is expanded, being widest between the fourth alveolus of each side. Liaoxipterus brachyognathus is assigned to Ctenochasmatidae based on the following characters: the rounded anterior end of the lower jaw is spatulated and dorsoventrally flattened and marked heterodonty in the dentition is absent. It differs from other ctenochasmatid pterosaurs in having relatively small number of teeth. Liaoxipterus is distinguished from some ornithocheirids, which have expanded anterior parts of the mandibular symphyses, such as Anhanguera piscator, Coloborhynchus robustus in which the teeth of the new pterosaur are not as variable.
基金This work was supported by the National Natural Science Foundation of China （grants Nos. 49802020, 49732100 and 40172074)the Specific Project for Authors of the Best Dissertations of Chinese Universities and Colleges （200022)
文摘Structural analyses show that the Ailaoshan-Red River shear zone （ASRRSZ） in Ailao Mountain is composed of three different deformational domains. These domains may represent three episodes of left-lateral slip experienced by the ASRRSZ. The first episode of such deformation occurred throughout the eastern high-grade belt of the ASRRSZ under a transtensional regime and produced L- type tectonites of amphibolite grade. The second episode of left-lateral slip formed high strain zones overprinting the high-grade belt. Its deformational mechanism is similar to simple shear and the deformed rocks are L-S mylonites of greenschist grade. The third episode of left-lateral slip took place chiefly in a western low-grade belt of the ASRRSZ. This deformation occurred in a transpressional regime, formed an overall structure pattern of a sinistral thrust system and produced phyllonites of low-greenschist grade. Geochronological data indicated that the three episodes of left-lateral slip happened before ～58-56 Ma, at least from ～27 Ma to 22 Ma and at ～13-12 Ma respectively. The first episode of slip in the ASRRSZ appeared to correspond to the initial collision of India and Asia at ～60 Ma. The second episode took place almost at the same time as the most intensive compression and uplift in Tibet. The latest event might represent a further eastward material flow in Tibet after ～16-13 Ma. Thus, the ASRRSZ of southeastern Asia probably experienced three main episodes of Tertiary left- lateral slip in the course of intracontinental convergence since the India-Asia collision.
基金jointly supported by the National Natural Science Foundation of China(Grant Nos.41702032 and 41972022)the Liaoning Revitalization of Talents Program(Grant No.XLYC1907037)the Geological Survey Programs of the Chinese Geological Survey(Grant Nos.DD20160048-4 and DD20190039-06)。
文摘Objective Petrified wood,as an important component of plant fossils,plays a significant role in understanding the floral composition and terrestrial palaeoclimates of the geological past.Though abundant petrified woods have been found from the Mesozoic deposits in the Great Xing’an Range,NE China,it was rare for systematic investigations to be carried out for these fossil wood remains.
基金supported by the Major Project of the National Natural Science Foundation of China (41890834 and 92162323)the Strategic Pilot Technology (B-type) Project of Chinese Academy of Sciences (CAS) (XDB18030205)+1 种基金the Key International Program of CAS (132A11KYSB20180042)the Key Research Program of Frontier Science, CAS (QYZDY-SSW-DQC017)。
文摘Banded iron formation and Cu-Zn sulfide deposits within volcanic-argillaceous sequences(as volcanogenic massive sulphide deposits(VMS)-like type) occur together in the Qingyuan greenstone belt of the North China Craton,recording the first appearance of oxidized ores and sulfide ores co-existing in the early Earth.The unique metal co-existing deposits should meet two requirements:tectonic setting and sedimentary environment.As regards to tectonic setting,plate-like tectonics might have started since the end of the Neoarchean because continents had grown large enough and there occurred volcanic arcs and backarc basins similar to modern ones in a way.Partial melting of subducted continental crust is conductive to providing ore-forming elements.As for sedimentary environment,late Neoarchean seawater was rich in Fe^(2+) and anoxic.Instantaneous oxidation of the seawater resulted possibly from frequent submarine volcanic eruptions and facilitated precipitation of the banded iron formation.At this point,it is also favorable for the enrichment of Cu and Zn ions in seawater.The VMS-like deposits tended to form when the seawater was reduced again.Studies of isotopic elements like sulfur,oxygen,iron and silicon support the above geological processes.It is shown that the geologic conditions only existed in the late Neoarchean and Paleoproterozoic for a short period of time.The banded iron formations disappeared around 1.85 Ga,and the associated sulfide metal deposits also became dominant sedimentary exhalative deposits in the meso-Neoproterozoic Boring Billion,as a result of increasing oxidation of the oceans and the increasing maturity of the continental crust.This study is significant not only for decoding metallogenic genesis but also helping understand rapid change in Precambrian tectonic regimes and Earth’s environments.
