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- Li, Li-Qin, et al.
(author)
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Palynofacies analysis for interpreting paleoenvironment and hydrocarbon potential of Triassic–Jurassic strata in the Sichuan Basin, China
- 2021
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In: Palaeoworld. - Nanjing : Elsevier. - 1871-174X .- 1875-5887. ; 30:1, s. 126-137
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Journal article (peer-reviewed)abstract
- The Sichuan Basin is one of the largest petroliferous basins in China. The continental fluvial‒lacustrine sediments of the Upper Triassic Xujiahe Formation and the Lower Jurassic Zhenzhuchong Formation yield diverse fossil organisms and host one of the most important gas reservoirs in thebasin. However, paleontological implication for the paleoenvironment and hydrocarbon source is less documented. Here, we report, for the first time for this basin, results from palynofacies analyses combined with thermal alteration data in the Early Mesozoic deposit of the Qilixia section, northeastern Sichuan Basin. The results show that, organic matters in sediments are dominated by phytoclasts, with less abundant palynomorphs and a few amorphous organic matters (AOMs). Four palynofacies assemblages were identified, reflecting depositional settings in a general proximal and oxicfluvial‒deltaic environment, with two distal-proximal sedimentary cycles. The prominent dominance of opaque phytoclasts within the lower Zhenzhuchong Formation may be related to frequent wildfires across the Triassic-Jurassic transition. Palynofacies data (especially the relative abundanceof opaque phytoclasts) may reflect 405 kyr eccentricity cyclicity pattern. The palynofacies and thermal alteration index (TAI), combined with geochemical data indicate the presence of type III kerogen in mature to post-mature phases, suggesting gas potential of the Xujiahe and Zhenzhuchong formations in the northeastern Sichuan Basin. This study provides significant implications for better understanding the paleoenvironment variationsduring the Triassic-Jurassic transition and the future gas exploration in this area.
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- Pan, Bing, et al.
(author)
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Early Cambrian organophosphatic brachiopods from the Xinji Formation, at Shuiyu section, Shanxi Province, North China
- 2020
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In: Palaeoworld. - : Elsevier BV. - 1871-174X .- 1875-5887. ; 29:3, s. 512-533
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Journal article (peer-reviewed)abstract
- Abundant and diverse small shelly fossils have been reported from Cambrian Series 2 in North China, but the co-occurring brachiopods are still poorly known. Herein, we describe seven genera, five species and two undetermined species of organophosphatic brachiopods including one new genus and new species from the lower Cambrian Xinji Formation at Shuiyu section, located on the southern margin of North China Platform. The brachiopod assemblage comprises one mickwitziid (stem group brachiopoda), Paramickwitzia boreussinaensis n. gen. n. sp., a paterinide, Askepasma toddense Laurie, 1986, an acrotretoid, Eohadrotreta cf. zhenbaensis Li and Holmer, 2004, a botsfordiid, Schizopholis yorkensis (Holmer and Ushatinskaya in Gravestock et al., 2001) and three linguloids, Spinobolus sp., Eodicellomus cf. elkaniiformis Holmer and Ushatinskaya in Gravestock et al., 2001 and Eoobolus sp. This brachiopod assemblage suggests a late Age 3 to early Age 4 for the Xinji Formation and reveals a remarkably strong connection with coeval faunas from East Gondwana, particularly the Hawker Group in South Australia. The high degree of similarity (even at species level) further supports a close palaeogeographic position between the North China Platform and Australian East Gondwana during the early Cambrian as indicated by small shelly fossil data.
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- Wang, Hai-Zhou, et al.
(author)
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Redescription and systematic position of Diandongia pista from the Chengjiang Lagerstätte
- 2023
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In: Palaeoworld. - : Elsevier. - 1871-174X .- 1875-5887. ; 32:3, s. 373-384
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Journal article (peer-reviewed)abstract
- Diandongia pista Rong is the thickest-shelled and strongly mineralized of all the brachiopods that have been recorded from the Chengjiang Fauna. It is also one of the most common species in the biota. Previous accounts have concentrated largely on the exceptionally preserved soft-bodied anatomy of this species. Here its detailed internal and external shell morphologies are described for the first time, based on BSEM and SEM observations. Its general shell morphology, pseudointerareas, and pustulose ornamentation are most similar to those of the Botsfordiidae, where many species have a Diandongia-like rhombic pattern of pustules in the juvenile apical region only. On the other hand, other aspects of the muscle pattern and the partly smooth adult ornamentation of D. pista is more suggestive of species within the Neobolidae, like Edreja. The mantle canal system in sub-adults of D. pista is comparable to that of the Eoobolidae and Obolidae, whereas the adult vascular system branches peripherally in dichotomy. D. pista may be the earliest representatives possessing some plesiomorphic characters of the Botsfordiidae.
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- Xian, Xiao Feng, et al.
(author)
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Growth patterns of palaeoscolecid sclerites from the Furongian (upper Cambrian) Wangcun section, western Hunan, South China
- 2023
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In: Palaeoworld. - : Elsevier BV. - 1871-174X.
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Journal article (peer-reviewed)abstract
- In a strict sense, palaeoscolecids are a group of cycloneuralian worms (ecdysozoans) characterized by the tessellation of trunk sclerites, which are differentiated into plates, platelets, and microplates. The Wangcun section in western Hunan, South China, which represents the Furongian Series (upper Cambrian), has yielded a rich and diverse collection of palaeoscolecids. However, there is uncertainty about how the morphology and arrangement of their sclerites change during ontogeny and the potential taxonomic implications of these changes. Here, we report new phosphatized trunk fragments from the Wangcun section, which are assigned to Dispinoscolex decorus, Hunanoscolex campus (= Ornatoscolex hunanensis), and Schistoscolex hunanensis. Trunk fragments of the same species with different diameter indicate the presence of several ontogenetic stages, and careful assessment revealed two types of sclerite growth patterns. One is represented by D. decorus and possibly also by S. hunanensis, in which the worm growth is accompanied mainly by the enlargement of the plates, with almost no change in the median annular zones and annulation boundaries. The other type is represented by H. campus, in which the worm growth is accompanied mainly by the widening of the median annular zones and annulation boundaries inserted with continuously more platelets and microplates. Because the specimens originally assigned to H. campus seem to represent late ontogenetic stages of O. hunanensis, we propose that H. campus is a senior synonym of the latter. This study underscores the importance of ontogenetic variation of sclerites for the taxonomy of palaeoscolecids, and highlights the significance of Orsten-type fossils in the study of metazoan ontogeny.
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