Feng Qinglai

Middle Triassic radiolarian fauna from southwest Yunnan, China

A highly diverse radiolarian fauna of Anisian age has been recovered from an 11 m continuous succession of siliceous rocks with tuffs and mudstones in the Changning-Menglian belt of southwestern Yunnan, China. Seventy-three radiolarian species and subspecies, among which, six new species, one new subspecies and 36 unidentified species, are included in the investigation. The 6 new species and 1 new subspecies are Triassocampe goricani, Triassocampe dumitricai, Triassocampe coronata inflata, Triassocampe relica, Archaeospongoprunum muyinense, Neopaurinella deweveri and Neopaurinella kozuri. Based on morphological comparison and stratigraphical range, some possible evolutionary relations are suggested. Four radiolarian zones, namely, Triassocampe deweveri Zone (late Anisian), Triassocampe coronata coronata Zone (middle Anisian), Triassocampe coronata inflata Zone (middle Anisian), and Triassocampe dumitricai Zone (early Anisian) are established. The Early Triassic radiolarian fauna in this area has a very low diversity and mainly consists of survivors of the Permian radiolarians. The recovery of the Triassic radiolarian fauna takes place in early Anisian. In this period, the multicyrtid nassellarians are moderately diverse and characterized by having a slender shell with weak constriction among segments; the spumellarian species are characterized by having needle-like main spines. In the middle and late Anisian, the shells of the multicyrtid nassellarians became strong with developed constrictions between segments, and both the spumellarians with needle-like spines and the spumellarians with three-bladed spines are diverse.

Ostracods (Crustacea) through the Permian-Triassic boundary in South China: the Meishan stratotype (Zhejiang Province)

The Global Stratotype Section and Point (GSSP) of the Permian–Triassic boundary, located in Meishan, Zhejiang Province, South China, was sampled bed-by-bed for ostracods. Ninety-eight species belonging to forty-three genera are recognized. Twenty-five new species are described and figured: Bairdia bassoni Crasquin sp. nov., B. broutini Crasquin sp. nov., B. deweveri Crasquin sp. nov., B. fangnianqiaoi Crasquin sp. nov., B. gaelleae Crasquin sp. nov., B. limatusformis Forel sp. nov., B. paussi Crasquin sp. nov., B. pierrevalentini Crasquin sp. nov., B. wushunbaoi Crasquin sp. nov., Baschkirina ballei Crasquin sp. nov., B. huzhouensis Forel sp. nov., Basslerella annesophieae Crasquin sp. nov., Hollinella martensiformis Crasquin sp. nov., Kempfina taihuensis Forel sp. nov., Knightina hongfui Crasquin sp. nov., Liuzhinia praeantalyaensis Forel sp. nov., Microcheilinella rectodorsata Forel sp. nov., M. shicheni Crasquin sp. nov., M.? multinodosa Forel sp. nov., Orthobairdia lemairei Crasquin sp. nov., Paraparchites chenshii Crasquin sp. nov., Praezabythocypris? pulchraformis Forel sp. nov., Samarella meishanella Forel sp. nov., S. victori Crasquin sp. nov., and Silenites? zhejiangensis Forel sp. nov. One new genus name is proposed: Kempfina Crasquin nom. nov. The stratigraphic distribution of all the species is given. Ostracod biodiversity variations are analyzed through the section. The main drop is recorded in bed 22, occurring a little earlier in ostracods than in foraminifers, corals and brachiopods. The decline in ostracod diversity is more progressive than in the other groups. Variations in ostracod biodiversity during the Changhsingian are related to fluctuations in palaeoenvironmental conditions.

Late Palaeozoic and Triassic deep-water deposits and tectonic evolution of the Palaeotethys in the Changning-Menglian and Lancangjiang belts, southwestern Yunnan

Abstract Discontinously exposed deep-water deposits in the Changning-Menglian belt, characterized by terrigenous turbidites, turbiditic marlstones, bedded radiolarian cherts, pelagic radiolarian shales, and some basaltic lavas and pyroclastic rocks, constitute a continous record of Palaeotethys evolution from early Devonian to middle Triassic, and strongly suggest that this belt is the main branch of the Palaeotethyan polyisland ocean in the Hercynian-Indosinian stage. According to the sedimentary history of the Changning-Menglian belt, the main basin of the Palaeotethys after opening for a long period narrowed markedly in the late permian but kept its typical oceanic environment until the end of middle Triassic. In the Lancangjiang belt, deep-water deposits occured mainly during the late Carboniferous to early Permian and are related to the island-arc volcanic activities. These deposits appear to be similar to those from the Petchabun belt of Thailand. Following the emergence of the Lincang magmatic arc in the studied area, which took place in mid-Permian times, the deep-water basin in the Lancangjiang belt between the Lincang and Simao massifs was closed, while the Palaeotethys main oceanic basin, represented by the Changning-Menglian belt to the west of the Lincang arc, hosted diverse pelagic sediments.

Biotic evolution and its relation with geological events in the Proterozoic Yanshan Basin, North China

The Yanshan Basin, located in northern North China, underwent three primary stages in the Mesoproterozoic, and corresponding biotas have been summarized for each stage in the present study. The three stages are stage A (the lower part of the Changcheng Group which dominated by clastic sediments), stage B (the upper part of the Changcheng Group to the Jixian Group which characterized by carbonate sediments), and stage C (the upper part of the Jixian Group which dominated by clastic sediments). This paper will focus on the evolution of biota during stage B. Microbiota of the stage B exhibits a high level of diversity and abundance. Planktonic microfossils have various forms and complex decorations. Most microfossils are generally small. In stage B, there was great variation in the biotic abundance and diversity, the average diameter of spherical benthic microfossils, and the maximum diameter of the spherical microfossils. We analyzed these parameters and identified two typical biotic events, and both biotic events were corresponded with geological events. The first event occurred in the third member of the Dahongyu Formation. In this era, the maximum diameter of the silicified microfossils significantly increased, and large, spherical planktonic specimens are abundant. The flourishing of large organisms in the strata is presumably related to volcanic activity. The second event occurred in the third member of the Gaoyuzhuang Formation. During this era, the microfossil assemblage changed significantly. The changes correspond with a decline in stromatolites as well as the transformations of the carbon isotope ratios and the elemental geochemistry.

A study on the geochemical characteristics of Upper Permian continental marginal arc volcanic rocks in the northern segment of South Lancangjiang Belt

Geochemical characteristics of the Upper Permian (P2) continental marginal arc volcanic rocks are described, which have been found recently around the areas of Xiaodingxi and Zangli on the eastern side of the Yunxian-Lincang granite, in terms of rock assemblage, petrochemistry, REE, trace elements, Pb isotopes, geotectonic environment and so on. The volcanic rock assemblage is dominated by basalt-andesite-dacite, with minor trachyte andecite-trachyte; the volcanic rock series is predominated by the calc-alkaline series, with minor tholleiite series and alkaline series rocks ; the volcanic rocks are characterized by high A12O3 and low TiO2, with K2O contents showing extremely strong polarity; the REE distribution patterns are characterized by LREE enrichment and right-inclined type; trace elements and large cation elements are highly enriched, Ti and Cr are depleted, and P and Nb are partially depleted; the Pb composition is of the Gondwana type; the petrochemical points mostly fall within the field of island-arc volcanic rocks, in consistency with the projection of data points of continental marginal volcanic rocks in the southern segment of the South Lancangjiang Belt and the North Lancangjiang Belt. This continental marginal arc volcanic rock belt, together with the ocean-ridge and ocean-island volcanic rocks and ophiolites in the Changning-Menglian Belt, constitute the ocean-ridge volcanic rock, ophiolite-arc rock-magmatic rock belts which are distributed in pairs, indicating that the Lancangjiang oceanic crust subducted eastwards. This result is of great importance in constraining the evolution of the paleo-Tethys in the Lancangjiang Belt.

High-resolution cyclostratigraphy of geochemical records from Permo-Triassic boundary section of Dongpan, southwestern Guangxi, South China

Spectral analysis is applied to geochemical data from a deep-water Permian-Triassic Boundary (PTB) section across PTB in Dongpan, Guangxi for high-resolution cyclostratigraphic research. The characteristics of the Milankovitch Cycles have been well recorded in the strata of the Dongpan section. Spectrum on Ce/La records shows especially that the ratios among its three preponderant cycles in the section are 5:2:1, which well displays the phenomenon of the sedimentary cycles driven by orbital force. The Milankovitch theory is further confirmed by the Paleozoic records.

Geochemical and Geochronological Constraints on the Origin of the Meta-basic Volcanic Rocks in the Tengtiaohe Zone, Southeast Yunnan

(t) 到 -2.11。他们的岩浆被导出从一充实并且没有重要外壳的污染的深披风来源。在 ELIP 形成的这些元基本的暴烈的岩石。因此， Tengtiaohe 地区不是一个 ophiolite 地区并且能在北越南连接到宋达地区。