The Port Island Formation(PIF), a typical Cretaceous red bed in Hong Kong, is dominated by non-fossiliferous, reddish clastic rocks, making it difficult to determine the sedimentary age of PIF precisely. Previous stud...The Port Island Formation(PIF), a typical Cretaceous red bed in Hong Kong, is dominated by non-fossiliferous, reddish clastic rocks, making it difficult to determine the sedimentary age of PIF precisely. Previous studies assigned the PIF to Late Cretaceous provisionally only on the basis of its stratigraphic sequence and lithology. This study identified a tuffite interlayer in the PIF and a zircon UPb age of 128.2±2.7 Ma by LA-ICP-MS method was obtained. It’s the first time to date the depositional age of the PIF with a reliable chronological constraint. With the support of stratigraphic evidence, we concluded that the geological age of PIF should be Early Cretaceous rather than Late Cretaceous. Based on the volcanic history of Hong Kong and Southeast China and the distribution of the PIF in Mirs Bay, it is believed that there was no volcanic activity in Hong Kong in ca. 128 Ma. The tuffite interlayer discovered in PIF was formed by the deposition of volcanic ash, which might originate from remote region outside Hong Kong, in an aquatic environment on Port Island. The identification of the tuffite interlayer, as the response to a volcanic event, has great significance not only to the studies of establishment and regional correlation of the strata system and the geological evolution in Hong Kong,but also to the study of volcanic activities in Southeast China.展开更多
The Xiamaling Formation of 1.4–1.35 Ga in Jixian Section and adjoining areas represents a unique Ectasian Period(Mesoproterozoic)sedimentary sequence in the North China Craton(NCC).Studies carried out during the last...The Xiamaling Formation of 1.4–1.35 Ga in Jixian Section and adjoining areas represents a unique Ectasian Period(Mesoproterozoic)sedimentary sequence in the North China Craton(NCC).Studies carried out during the last decade have contributed significantly in improving our understanding about the Ectasian sedimentation tectonics in the NCC during this transitional interval between the breakup of Supercontinent Columbia and the assembly of Rodinia.The present study reports,for the first time,tuffite beds interlayered with carbonaceous-siliceous slate-phyllite in the upper Baishugou Formation(western Henan Province),at the southern margin of NCC.The LA-MC-ICPMS U-Pb geochronology of zircons from two tuffite samples has yielded almost identical ages of 1330±10 Ma(MSWD=0.43,N=38)and 1332±10 Ma(MSWD=0.90,N=24),that constrain a 1.33 Ga depositional age(Ectasian Period)for the Baishugou Formation.A close similarity in lithological characteristics and their respective superimposed lithostratigraphic relationships of the Baishugou and Xiamaling formations,underline a comparable depositional environment for them.The high-precision geochronology data on the Baishugou Formation would stimulate a relook into the Meso-Neoproterozoic chronostratigraphic framework of the NCC,and further research would lead to a comprehensive understanding of the geological evolution of the NCC during Ectasian Period and its correlation with analogous global events.展开更多
The Tezoantla Tuff(«Cantera de Tezoantla»in Spanish)was designated as a‘Heritage Stone’by the International Union of Geological Sciences on October 22,2022,under revised criteria that were approved the sam...The Tezoantla Tuff(«Cantera de Tezoantla»in Spanish)was designated as a‘Heritage Stone’by the International Union of Geological Sciences on October 22,2022,under revised criteria that were approved the same year,being the first in Mexico and the second to be awarded a volcanic tuff.It is a volcanic ash tuff of Miocene age,with lowtemperature argillic hydrothermal alteration(zeolitization),that has been quarried for at least 400 years in the municipality of Mineral del Monte of the Comarca Minera UNESCO Global Geopark.Due to its aesthetic value(in particular,the white variety)and suitable physical properties,this stone has been used as building and sculpture material in notable monuments of Baroque,eclectic and Neoclassical styles of the state of Hidalgo and the historic center of Mexico City,most of which are cataloged in different lists of cultural heritage.In addition,it has been widely used in vernacular architecture and in industrial constructions that are part of the outstanding mining heritage of the geopark,with Cornish engine houses(19th century)standing out.展开更多
This study describes a sequence of microbialites and volcanics of the Lower Cretaceous Shipu Group, an example of microbialites influenced by volcanic activity. It is located at Shipu town in eastern Zhejiang Province...This study describes a sequence of microbialites and volcanics of the Lower Cretaceous Shipu Group, an example of microbialites influenced by volcanic activity. It is located at Shipu town in eastern Zhejiang Province on the coast of southeastern China. Based on macroscopic outcrop observations, microscopic examination of thin sections,electron probe microanalysis(EPMA), field emission scanning electron microscopy(FESEM) imaging analysis, and energy dispersive X-ray spectrometry(EDS) analysis, nine microbialite–tuffite assemblages have been recognized in the section. Their thickness increased gradually upwards as volcanism decreased. There are ooids, bioclastic grains,intraclasts and tuffaceous grains in the grain shoal with local dolomitization. Above the grain shoal, microbial reefs develop either individually or conjoining with adjacent ones, and consist of stromatolites and serpulid tubes with common recrystallization. Tubes of serpulids are calcified and the tube wall is micrite. The tube and intertube parts are filled by sparry calcite. Colonial serpulids are surrounded by microbes to form stromatolites. Black layers of stromatolites contain many calcite crystals with fan-shaped growth pattern and preserved organic matter. Microbes are so well preserved in crystal lattices that the original microstructure of the microbes can be clearly observed by FESEM imaging analysis. Microbial reefs develop at a local high point near or above fair-weather wave-base where waves removed fine volcanic ashes. Interreef deposits are coarse tuffite due to physical differentiation. Volcanic activity could provide rich nutrition for microbes, but too much fine volcanic ash inhibits microbial growth. As a result, a moderate supply of volcanic ash favors the development of microbialites.展开更多
基金supported by the Youth Innovation Promotion Association CAS (2017085)geological survey program of Agriculture, Fisheries and Conservation Department of Hong Kong Special Administrative Region (AFCD/SQ/92/14)
文摘The Port Island Formation(PIF), a typical Cretaceous red bed in Hong Kong, is dominated by non-fossiliferous, reddish clastic rocks, making it difficult to determine the sedimentary age of PIF precisely. Previous studies assigned the PIF to Late Cretaceous provisionally only on the basis of its stratigraphic sequence and lithology. This study identified a tuffite interlayer in the PIF and a zircon UPb age of 128.2±2.7 Ma by LA-ICP-MS method was obtained. It’s the first time to date the depositional age of the PIF with a reliable chronological constraint. With the support of stratigraphic evidence, we concluded that the geological age of PIF should be Early Cretaceous rather than Late Cretaceous. Based on the volcanic history of Hong Kong and Southeast China and the distribution of the PIF in Mirs Bay, it is believed that there was no volcanic activity in Hong Kong in ca. 128 Ma. The tuffite interlayer discovered in PIF was formed by the deposition of volcanic ash, which might originate from remote region outside Hong Kong, in an aquatic environment on Port Island. The identification of the tuffite interlayer, as the response to a volcanic event, has great significance not only to the studies of establishment and regional correlation of the strata system and the geological evolution in Hong Kong,but also to the study of volcanic activities in Southeast China.
基金supported by the National Natural Science Foundation of China(Grant Nos.41630211,41872198,41772028&41890834)。
文摘The Xiamaling Formation of 1.4–1.35 Ga in Jixian Section and adjoining areas represents a unique Ectasian Period(Mesoproterozoic)sedimentary sequence in the North China Craton(NCC).Studies carried out during the last decade have contributed significantly in improving our understanding about the Ectasian sedimentation tectonics in the NCC during this transitional interval between the breakup of Supercontinent Columbia and the assembly of Rodinia.The present study reports,for the first time,tuffite beds interlayered with carbonaceous-siliceous slate-phyllite in the upper Baishugou Formation(western Henan Province),at the southern margin of NCC.The LA-MC-ICPMS U-Pb geochronology of zircons from two tuffite samples has yielded almost identical ages of 1330±10 Ma(MSWD=0.43,N=38)and 1332±10 Ma(MSWD=0.90,N=24),that constrain a 1.33 Ga depositional age(Ectasian Period)for the Baishugou Formation.A close similarity in lithological characteristics and their respective superimposed lithostratigraphic relationships of the Baishugou and Xiamaling formations,underline a comparable depositional environment for them.The high-precision geochronology data on the Baishugou Formation would stimulate a relook into the Meso-Neoproterozoic chronostratigraphic framework of the NCC,and further research would lead to a comprehensive understanding of the geological evolution of the NCC during Ectasian Period and its correlation with analogous global events.
基金Funding is provided by the projects CONACYT FORDECYTPRONACES(315487)PAPIME-DGAPA,UNAM(PE107617).
文摘The Tezoantla Tuff(«Cantera de Tezoantla»in Spanish)was designated as a‘Heritage Stone’by the International Union of Geological Sciences on October 22,2022,under revised criteria that were approved the same year,being the first in Mexico and the second to be awarded a volcanic tuff.It is a volcanic ash tuff of Miocene age,with lowtemperature argillic hydrothermal alteration(zeolitization),that has been quarried for at least 400 years in the municipality of Mineral del Monte of the Comarca Minera UNESCO Global Geopark.Due to its aesthetic value(in particular,the white variety)and suitable physical properties,this stone has been used as building and sculpture material in notable monuments of Baroque,eclectic and Neoclassical styles of the state of Hidalgo and the historic center of Mexico City,most of which are cataloged in different lists of cultural heritage.In addition,it has been widely used in vernacular architecture and in industrial constructions that are part of the outstanding mining heritage of the geopark,with Cornish engine houses(19th century)standing out.
基金National Major Science and Technology Projects (2016ZX05004–002,2017ZX05008–005)PetroChina Major Science and Technology Projects(2018A-01,2019B-0403)PetroChina Science and Technology Project(2019D-5009-16)。
文摘This study describes a sequence of microbialites and volcanics of the Lower Cretaceous Shipu Group, an example of microbialites influenced by volcanic activity. It is located at Shipu town in eastern Zhejiang Province on the coast of southeastern China. Based on macroscopic outcrop observations, microscopic examination of thin sections,electron probe microanalysis(EPMA), field emission scanning electron microscopy(FESEM) imaging analysis, and energy dispersive X-ray spectrometry(EDS) analysis, nine microbialite–tuffite assemblages have been recognized in the section. Their thickness increased gradually upwards as volcanism decreased. There are ooids, bioclastic grains,intraclasts and tuffaceous grains in the grain shoal with local dolomitization. Above the grain shoal, microbial reefs develop either individually or conjoining with adjacent ones, and consist of stromatolites and serpulid tubes with common recrystallization. Tubes of serpulids are calcified and the tube wall is micrite. The tube and intertube parts are filled by sparry calcite. Colonial serpulids are surrounded by microbes to form stromatolites. Black layers of stromatolites contain many calcite crystals with fan-shaped growth pattern and preserved organic matter. Microbes are so well preserved in crystal lattices that the original microstructure of the microbes can be clearly observed by FESEM imaging analysis. Microbial reefs develop at a local high point near or above fair-weather wave-base where waves removed fine volcanic ashes. Interreef deposits are coarse tuffite due to physical differentiation. Volcanic activity could provide rich nutrition for microbes, but too much fine volcanic ash inhibits microbial growth. As a result, a moderate supply of volcanic ash favors the development of microbialites.
