This paper concerns deals with the Mongolian regional stratigraphic classification of sedimentary, sedimentary-volcanogenic sediments, and metamorphic complex spread over the territory of Mongolia according to the new...This paper concerns deals with the Mongolian regional stratigraphic classification of sedimentary, sedimentary-volcanogenic sediments, and metamorphic complex spread over the territory of Mongolia according to the new International Chronostratigraphic Chart [1]. The regional stratigraphy of Precambrian-Cenozoic rocks of the Mongolian territory was studied by Dorjnamjaa et al. [2]. So, this paper provides for the stratigraphy and correlation of key sections through the Archean-Proterozoic-Mesozoic-Cenozoic of various areas of Mongolia. In this paper, the author introduces the most important results indicating the key reference sections for the first time and put into a broad regional context. The characterization and geologic mapping of lithological units provided an essential basis for the lithostratigraphy, biostratigraphy and chemostratigraphy. Especially key biostratigraphic aspects are the phenomenon of faunal succession. The basic lithostratigraphic unit is the formations and groups which have been successful mapped. At present in Mongolia for Precambrian period (systems and series) 30 formations and groups, for Paleozoic—about 250 formations and groups, for Mesozoic—102 formations and groups, for Cenozoic—27 formations, members, and beds are distinguished. The auxiliary stratigraphic units are members, beds which should be mapped depending on great extent of detailed study. In the regional stratigraphical classification, there are two primary kinds of stratotypes [3]: a) unit stratotypes, which serve as the standard of definition for a stratigraphic unit, and b) boundary stratotypes, which serve as the standard of definition for a stratigraphic boundary. These aspects, in particular gradational boundaryas far as possible were examined for example for Archean-Paleoproterozoic (by geochronologic data), Ediacaran-Early Cambrian (by soft-bodied fossils, trace fossils and small shelly fossils), Ordovician-Silurian (by beyrichiidostracodes), Devonian-Carboniferous (by conodonds), Paleocene-Eocene (by mammals), Oligocene-Miocene (by small rodents) systems and series.展开更多
Fossil plants Hedeia sinica Hao et Gensel 1998, Huia gracilis Wang Ct Hao2001 and Guangnania cuneata Wang et Hao are described from the Lower Devonian Xujiachong Formation,the Qujing district, eastern Yunnan, China. T...Fossil plants Hedeia sinica Hao et Gensel 1998, Huia gracilis Wang Ct Hao2001 and Guangnania cuneata Wang et Hao are described from the Lower Devonian Xujiachong Formation,the Qujing district, eastern Yunnan, China. They contribute to our knowledge of the flora in thisdistrict. Based on the occurrence of common plants (Hedeia, Huia, Guangnania and Zosterophyllumaustralianum) and their horizons, it is proved for the first time that the mid-lower assemblage ofthe Xujiachong flora is comparable with the Early Devonian ((late) Pragian) Posongchong flora ofsoutheastern Yunnan and the upper Baragwanathia flora of Australia. In view of this fact and thestratigraphic sequence, the mid-lower part of the Xujiachong Formation is considered to be of (late)Pragian age. Through comprehensive analyses of plant, bivalve and fish assemblages and thelithology, the upper part of the Xujiachong Formation is dated to he of early Emsian age. TheXujiachong flora belonged to the northeastern Gondwana palaeophytogeographic unit during the EarlyDevonian. The early Emsian assemblage of this flora inherited the characters of the Posongchongflora and also exhibited the endemic elements. Belonging to different phytogeographic units, theXujiachong and Posongchong floras differ from the coeval flora of the Laurussian palaeocontinent.The Xujiachong flora is comparatively simple in composition, while the Posongchong flora hasabundant and highly diversified endemics. The disparity between them has resulted from the differentenvironments.展开更多
文摘This paper concerns deals with the Mongolian regional stratigraphic classification of sedimentary, sedimentary-volcanogenic sediments, and metamorphic complex spread over the territory of Mongolia according to the new International Chronostratigraphic Chart [1]. The regional stratigraphy of Precambrian-Cenozoic rocks of the Mongolian territory was studied by Dorjnamjaa et al. [2]. So, this paper provides for the stratigraphy and correlation of key sections through the Archean-Proterozoic-Mesozoic-Cenozoic of various areas of Mongolia. In this paper, the author introduces the most important results indicating the key reference sections for the first time and put into a broad regional context. The characterization and geologic mapping of lithological units provided an essential basis for the lithostratigraphy, biostratigraphy and chemostratigraphy. Especially key biostratigraphic aspects are the phenomenon of faunal succession. The basic lithostratigraphic unit is the formations and groups which have been successful mapped. At present in Mongolia for Precambrian period (systems and series) 30 formations and groups, for Paleozoic—about 250 formations and groups, for Mesozoic—102 formations and groups, for Cenozoic—27 formations, members, and beds are distinguished. The auxiliary stratigraphic units are members, beds which should be mapped depending on great extent of detailed study. In the regional stratigraphical classification, there are two primary kinds of stratotypes [3]: a) unit stratotypes, which serve as the standard of definition for a stratigraphic unit, and b) boundary stratotypes, which serve as the standard of definition for a stratigraphic boundary. These aspects, in particular gradational boundaryas far as possible were examined for example for Archean-Paleoproterozoic (by geochronologic data), Ediacaran-Early Cambrian (by soft-bodied fossils, trace fossils and small shelly fossils), Ordovician-Silurian (by beyrichiidostracodes), Devonian-Carboniferous (by conodonds), Paleocene-Eocene (by mammals), Oligocene-Miocene (by small rodents) systems and series.
基金the Chinese Strafigraphy Project of the Ministry of Science and Technology,China(2001DEA20020-5) the National Natural Science Foundation of China(Grant 49972009).
文摘Fossil plants Hedeia sinica Hao et Gensel 1998, Huia gracilis Wang Ct Hao2001 and Guangnania cuneata Wang et Hao are described from the Lower Devonian Xujiachong Formation,the Qujing district, eastern Yunnan, China. They contribute to our knowledge of the flora in thisdistrict. Based on the occurrence of common plants (Hedeia, Huia, Guangnania and Zosterophyllumaustralianum) and their horizons, it is proved for the first time that the mid-lower assemblage ofthe Xujiachong flora is comparable with the Early Devonian ((late) Pragian) Posongchong flora ofsoutheastern Yunnan and the upper Baragwanathia flora of Australia. In view of this fact and thestratigraphic sequence, the mid-lower part of the Xujiachong Formation is considered to be of (late)Pragian age. Through comprehensive analyses of plant, bivalve and fish assemblages and thelithology, the upper part of the Xujiachong Formation is dated to he of early Emsian age. TheXujiachong flora belonged to the northeastern Gondwana palaeophytogeographic unit during the EarlyDevonian. The early Emsian assemblage of this flora inherited the characters of the Posongchongflora and also exhibited the endemic elements. Belonging to different phytogeographic units, theXujiachong and Posongchong floras differ from the coeval flora of the Laurussian palaeocontinent.The Xujiachong flora is comparatively simple in composition, while the Posongchong flora hasabundant and highly diversified endemics. The disparity between them has resulted from the differentenvironments.
