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《Bulletin of Mineralogy, Petrology and Geochemistry》
JOPC 2023 Vol.25 Number 2
2023, Vol.25 Num.2
Online: 2023-04-01
LITHOFACIES PALAEOGEOGRAPHY AND SEDIMENTOLOGY
BIOPALAEOGEOGRAPHY AND PALAEOECOLOGY
LITHOFACIES PALAEOGEOGRAPHY AND SEDIMENTOLOGY
255
JI Youliang, ZHANG Yue, ZHOU Yong, JI Lulu, REN Hongyan, GUO Shanshan, GAO Chenxi, MA Zhengtao, LIU Xiaoyu, LIU Dawei, DUAN Xiaobing, HUAN Zhijun, GAO Chonglong, GUO Ruijing, PANG Chuanmeng, SUN Jia, YANG Dongji
Architecture of braided river alluvial fan under episodic flood conditions: a case study of modern Baiyang River alluvial fan in northwestern margin of Junggar Basin
The Baiyang River alluvial fan is a composite alluvial fan composed of the debris-flow deposits during the episodic flood period and the braided river sediments during the intermittent flood period. Its architectures are very different from that of debris-flow fans and fluvial fans. The current study selected the modern Baiyang River alluvial fan developed in the arid climate of the northwestern margin of the Junggar Basin as an anatomical example,and conducted detailed measurements on 103 natural profiles and 8 artificial large-scale exploration trenches. On the basis of the observation and analysis,the evolutionary process and sedimentary configuration characteristics of the geomorphic unit of the intermittent braided river alluvial fan under the condition of paroxysmal flood were analyzed,and the paroxysmal flood of different flow states was studied. Various construction and reconstruction mechanisms under different flow regime were analyzed,and the sedimentary characteristics of intermittent braided river alluvial fans controlled by episodic floods were clarified,and their sedimentary architecture models were established. Observations from the current study suggest that in the flood period,the episodic flood formed sheet-like sheet flow(or sheet flood)deposition,and that during the flood retreat period,with the weakening of the flood intensity,it was transformed into braided flow deposition,and that during the inter-flood period,there are still continuous braided fluids(braided rivers)flowing in the restricted channels,resulting in restricted(banded)braided channel deposits. A more complex depositional architectures were seen to occurrence in which the sediments of the two periods were frequently superimposed in space and time. This model has a certain reference value for genetic identification,prediction and comparison of alluvial fan sand-gravel reservoirs in oilfields.
2023 Vol. 25 (2): 255-276 [
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1058
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277
JIAO Yue, WU Chaodong, WANG Jialin, JIAO Guohua, ZHANG Weiping, GUAN Xutong
Comparative study on sedimentary characteristics and palaeoenvironment of the Permian Lucaogou Formation in eastern Tianshan Mountains
The depositional age,sedimentary environment and tectonic setting of the Permian Lucaogou Formation in eastern Tianshan Mountains are controversial. Based on the standard fossil assemblages of
Turfania taoshuyuanensis
and
Tomiella
found in the Lucaogou Formation,the large number of detrital zircons from the sedimentary strata with the youngest peak age of 261 Ma,it is believed that the deposition age of the Lucaogou Formation is Guadalupan(Middle Permian) rather than Uralian(Early Permian). Based on the discovery of typical marine indicator mineral glauconite,the discovery of marine facies or the interactional facies of
Tomiella
and the confirmation of ultra-high salinity saline lake basin,it is considered that the Lucaogou Formation was mainly lacustrine sediments,but some sedimentary periods were affected by transgression(flooding)events. In eastern Tianshan Mountains,the Permian Lucaogou Formaition of Junggar Basin,Santanghu Basin and Tu-Ha Basins has similar rock assemblages,faunal features and tectonic characteristics,but there are differences in paleo-salinity,paleo-water depth,paleo-climate,paleo-redox conditions and primary productivity among different basins,suggesting that the Lucaogou Formation was deposited in a series of dispersed rift basins,and there is no unified depositional center among different basins.
2023 Vol. 25 (2): 277-293 [
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504
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294
LI Fengjie, WANG Jia, MA Xiaokang, LAI Xuelian, ZHANG Pengfei, REN Xuying, CHEN Zheng'an
Mixed sedimentation of the Middle Devonian Jinbaoshi Formation in Longmen Mountain area,Sichuan Province
The Devonian of Longmen Mountain area is an important and highly studied area. The Middle Devonian Jinbaoshi Formation is composed of clastic rocks,carbonate rocks and mixed rocks. In this paper,the sedimentary facies of the Jinbaoshi Formation were studied in detail based on thin section observation and the measured data of the Pingyipu section in Pingwu County and Ganxi section in Beichuan County. The results show that the Middle Devonian Jinbaoshi Formation in Longmen Mountain area has four sedimentary facies,namely fluvial,clastic shore,shelf and carbonate ramp. The sedimentary evolution experienced two cycles. The mixed sedimentation of Jinbaoshi Formation was produced by facies mixing and in situ mixing. The change of relative sea level,terrigenous clastic supply,carbonate production rate and paleoclimate are the main controlling factors for the mixed deposition of facies mixing,while wave and storm waves are the main mechanisms for the mixed deposition of terrigenous clastic and carbonate components. The study on the sedimentary sequence,sedimentary characteristics and sedimentary evolution of the Jinbaoshi Formation is helpful to improve the understanding of the sedimentary paleoenvironment of the Devonian in Longmen Mountain area,Sichuan Basin.
2023 Vol. 25 (2): 294-307 [
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308
MENG Yan, LI Zhuangfu, SHEN Yulin, YANG Tianyang, JING Yuhong, WEN Zuchao, ZHU Yulin, LIU Bingwen
Sedimentary environment evolution and event deposition of the Neopro-terozoic Niyuan Formation of Zhaowei section in Xuzhou, Jiangsu Province,China
The Neoproterozoic Niyuan Formation in Zhaowei, Xuzhou is exposed completely and continuously, with representative lithologic assemblages, abundant sedimentary phenomena, and a large number of typical event deposits, which has been a concern for a long time because of its controversial genesis. Based on the field macro lithologic assemblage and microscopic rock characteristics of the Niyuan Formation, and by means of macro-micro comparison, this paper analyzes the sedimentary environment and event sedimentary characteristics of the Niyuan Formation and discusses the causes of frequent occurrence and diverse types of event deposition. The results show that: (1) The sedimentary environment of the Niyuan Formation from base to top is lagoon-the middle and upper part of the gentle slope-the lower part of the gentle slope-the middle and upper part of the gentle slope-tidal flat or lagoon; (2) The development of event deposits in each section is different. Gravelly limestone and scouring filling structure are developed in each section, but the lower and middle sections are large. In addition, seismic breccia and liquefied diapir structure are seen in some parts of the middle section, molar-tooth structure is developed at the top, while molar-tooth structure is mainly seen at the bottom of the upper section, and soft sediment deformation structure and cross bedding are seen in the middle and upper part. Based on the analysis of sedimentary environment, it is considered that the event sediments mainly occurred in the gentle slope environment, tidal flat and lagoon environment; (3) Synthesizing the above research results, it is concluded that the dynamic mechanism of the special cycle composed of frequent multi-type event sedimentation and normal sedimentation of the Niyuan Formation may be related to periodic earthquake-storm action, that is, it can be the result of multi-factor coupling effect caused by the superposition of extensional regional tectonic movement on the eastern margin of North China platform and the Milankovitch cycle caused by the convergence and fragmentation of the Rodinia paleocontinent.
2023 Vol. 25 (2): 308-322 [
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427
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BIOPALAEOGEOGRAPHY AND PALAEOECOLOGY
323
2023 Vol. 25 (2): 323-326 [
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590
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220
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327
SHAN Xianren, ZHU Min, ZHAO Wenjin, GAI Zhikun
Fossil fishes from the Silurian Lower Red Beds in Wuhan, Hubei and their biogeographic significances
Based on the new findings of fossil fishes from the Silurian shallow marine red beds at the Gumushan section,Wuhan,Hubei Province,the lower Telychian(Llandovery)red beds are confirmed to be developed in southeastern Hubei. The original Fentou Formation in Wuhan area is emended and subdivided into two parts: the upper part is the emended Fentou Formation,while the lower part is called Qingshui Formation. The redefined Fentou Formation is characterized by yellowish-green,gray-green,and gray-yellow mudstones,argillaceous siltstones,and siltstones bearing abundant brachiopods,bivalves,gastropods,trilobites,and trace fossils. The lower part of the Qingshui Formation consists of purple-red,reddish-brown mudstones and argillaceous siltstones intercalated with quartz sandstones,while its upper part is dominated by purple-red and yellowish-green quartz sandstones intercalated with mudstones,argillaceous siltstones and siltstones containing lots of fossil fishes. Fishes from the upper part of the Qingshui Formation include the galeaspids
Hanyangaspis guodingshanensis
,
Hongshanaspis inexpectatus
,
Jiangxialepis retrospina
,and the chondrichthyans
Sinacanthus
and
Neosinacanthus
,all belonging to the Wentang Fish Assemblage of the Zhangjiajie Vertebrate Fauna. The galeaspid
J. retrospina
can be compared directly to
J. jiujiangensis
from the Qingshui Formation in Wuning area,Jiangxi Province,as members of the genus
Jiangxialepis
assignable to the family Shuyuidae,whose members are elements of the Silurian Lower Red Beds in South China. According to comprehensive analysis of the fish assemblage and stratigraphic sequence,the Lower Red Beds in Wuhan,with an age of early Telychian,can be correlated with the Houjiatang Formation in Anhui and Jiangsu,the Tangchiawu Formation in Zhejiang,the Qingshui Formation in Jiangxi,the Rongxi Formation in Hunan,and the Tataertag Formation in Tarim Region. In addition,the distribution pattern of the Silurian Lower Red Beds in the South China Block indicates that the Upper and Lower Yangtze seas were connected by a narrow shallow epeiric water during the early Telychian,which probably provides a precondition for the galeaspids dispersing and communicating between Wuning of Jiangxi and Wuhan of Hubei.
2023 Vol. 25 (2): 327-340 [
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341
ZHANG Shurong, SHAN Xianren, GAI Zhikun
New findings of huananaspid fishes from the Lower Devonian in Nanning, Guangxi and their stratigraphic and biogeographic significances
Two new species of Huananaspidae(Huananaspidiformes,Galeaspida),
Huananaspis cupido
sp. nov. and
Asiaspis liangi
sp. nov.,are described from the lower part of the Nagaoling Formation(Pragian,Early Devonian)in Nanning,Guangxi,China.
H. cupido
sp. nov. differs from
H. wudingensis
in smaller headshield,lacking median dorsal spine,and cornual processes extending beyond the posterior margin of the headshield.
A. liangi
sp. nov. differs from
A. expansa
in headshield length greater than width,cornual processes extending posterolaterally,serrated posterior margin of cornual processes,and longitudinal oval median dorsal opening. The Nagaoling Formation yields reliable index fossils indicating a Pragian age,thus the Xujiachong vertebrate assemblage yielded from this formation can provide a palaeoichthyological standard for stratigraphic correlations of Early Devonian in South China. New findings of
Huananaspis
and
Asiaspis
from the Nagaoling Formation enriches the biodiversity of huananaspids,adds new members to the the Xujiachong vertebrate assemblage,and provides direct fossil evidence for the correlation between the Posongchong Formation in Wuding of Yunnan and the Nagaoling Formation in Nanning of Guangxi. The Xujiachong vertebrate assemblage is the most diversified in the transitional beds between the Lianhuashan and Nagaoling formations,almost containing all genera in adjacent regions,indicating that Naning of Guangxi is one of the centers for galeaspids radiating and dispersing. Fish assemblage displays a similar high level of endemism to that of the vascular plants and brachiopod fauna during the Pragian of Early Devonian,which probably caused by the South China sea,a large semi-closed epicontinental gulf. Because of the effect of a closed sea,fishes show exceptional taxonomic diversity and high levels of endemism,forming an independent biogeographic region known as‘galeaspid-yunnanolepid province’ in South China.
2023 Vol. 25 (2): 341-355 [
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356
JIN Jun, LUO Zhengjiang, WANG Jian, ZHANG Xiaogang, CHEN Jun, LI Changgen, SUN Yucong, HUANG Xing, QIE Wenkun, SONG Junjun
Ostracods from the Upper Carboniferous Qijiagou Formation, Urümqi region,Xinjiang and their implications on palaeoenvironment and palaeobiogeography
The overall occurrence,stratigraphical distribution,palaeoenvironmental and palaeobiogeographical significances of the ostracod faunas from the Upper Carboniferous Qijiagou Formation in the Qijiagou section of the Urümqi region,China,are documented in this study. Nineteen species belonging to 11 genera are identified and figured herein. The ostracod fauna in the Qijiagou Formation indicates an age of the Moscovian-Kasimovian. The ostracod assemblages from the Qijiagou Formation belong to palaeocopid and smooth-podocopid associations,and ecologically equivalent to the OA1-OA3 assemblages in the active plate margin. The changes of ostracod assemblages and sedimentary evidences from the Qijiagou section indicate littoral and shallow sea facies,and there was probably a regression when the Qijiagou Formation were being deposited in the Qijiagou section of the Urümqi region. The ostracods of the Qijiagou Formation have strong affinities with the taxa of Tarim,Junggar,central Tianshan and Urals,and also share some similarities with those from North America,West Europe and North China. This implies that the Junggar and Tarim blocks converged and were relatively close to the Laurasia during the Pennsylvanian(Late Carboniferous),and ostracods experienced faunal exchanges between Junggar-Tarim blocks and Laurentia. The above ostracods, further enriched the fossil materials of Qijiagou Formation, is of great sinificance for exploring the evolutionary characteristics of the acient Asian Ocean and regional mineral devdopment.
2023 Vol. 25 (2): 356-367 [
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368
LI Gang
Clam shrimp fauna of the Jurassic Yanliao Biota: composition and evolution
The well-known Middle-Late Jurassic Yanliao Biota contains abundant and excellently preserved terrestrial fossils. It can be subdivided into the early Yanliao Biota,
i.e.
the Daohugou Biota,and the late Yanliao Biota,
i.e.
the Linglongta Biota,respectively. The Daohugou Biota contains a triglyptids clam shrimp fauna,including
Triglypta haifanggouensis
,
T. luanpingensis
and
T.pingquanensis.
The Linglongta Biota contains a triglyptids-aquilonoglyptids clam shrimp fauna,comprising
Triglypta jianchangensis
,
Liaoxiestheria linglongtaensis
,
Linglongtaestheria daxishanensis
and
Linglongtaestheria qinglongensis.
According to the latest SEM research results,
Qaidamestheria
,
Liaoxiestheria
and
Linglongtaestheria
should be assigned to the family Aquilonoglyptidae.
Punctatestheria
,ornamented with evenly distributed punctae,first occurred in the Lower Jurassic Badaowan Formation in Junggar Basin,and gave rise to
Triglypta
in the late Middle Jurassic.
Qaidamestheria
does not have direct evolutionary relationship with
Triglypta.
2023 Vol. 25 (2): 368-381 [
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382
ZHANG Lijun, PANG Zhichao, YANG Qiqi, FAN Liu, WEI Fan, SONG Huibo, NIU Yongbin
Behavioural evolution pattern and biogeographical migration of the Paleozoic psammichnitids
Psammichnites
and
Dictyodora
are grouped into psammichnitids,representing the typical slug-like bulldozers with a snorkel living in the marine environments during the Palaeozoic. Through the morphological and functional analysis of Paleozoic
Psammichnites
and
Dictyodora
,combining with their spatio-temporal distribution characteristics,it is found: (1)
Psammichnites
generally has short and shallow grooves,and the wall height of
Dictyodora
gradually increased with time. (2)
Psammichnites
is mainly distributed in the shallow-marine environment,whereas
Dictyodora
is mainly distributed in deep-marine environment with occasional occurrences of certain ichnospecies in the shallow-marine environment. (3)The ichnodiversity of
Psammichnites
ichnospecies rapidly increased in the Carboniferous shallow-marine environment,belonging to the top-heavy pattern.
Psammichnites gigas
is distributed widely in the Early Cambrian strata,which is of biostratigraphic importance. The ichnodiversity of
Dictyodora
ichnospecies rapidly expanded in the Ordovician,representing the bottom-heavy pattern. (4)
Psammichnites
and
Dictyodora
were mainly distributed in the Iapetus and Rheic oceans in the middle and high latitudes of the southern hemisphere during the Cambrian to Ordovician. Due to the formation of Laurussia and the closure of Iapetus and Rheic oceans,
Psammichnites
and
Dictyodora
migrated to the new empty ecological niches from the Carboniferous to Permian,indicating that the adaptation and migration of trace makers to new ecological niches might be strongly influenced by environmental changes. Until now
Psammichnites
and
Dictyodora
have not been found in the post-Permian strata,possibly suggesting that their trace markers went extinct in the end-Permian mass extinction. On the basis of the above systematic summary and induction of the behavior habits,biogeographic migration characteristics and evolutionary characteristics of
Psammochnites
and
Dictyodora
,it can provide new data and new understanding of the evolutionary ecology and biogeographic migration characteristics of trace groups reflected by trace fossils from a detailed and profound perspective.
2023 Vol. 25 (2): 382-391 [
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392
ZHANG Xiaole, WANG Yi, LIU Jianbo, HUANG Pu, XU Honghe
Bivalvian trace fossils from the Lower Devonian Pingyipu Formation in northwestern Yangtze Platform
Abundant bivalve trace fossils are found in the Lower Devonian Pingyipu Formation in Guangyuan area,northern Sichuan Province,but systematic ichnological work and behavioral and paleoecological analysis have not been carried out. Close observations on the occurrence,preservation style and morphological features of bivalvian traces provide invaluable information to guide the interpretation of their trace maker,ethological and paleoecological features. Here we carried out sedimentary and systematic ichnology studies on the middle part of the Lower Devonian Pingyipu Formation at the Majia section,Guangyuan area. The results suggest occurrence of bivalvian trace fossils,including
Lockeia siliquaria
,
Protovirgularia rugosa
,
Ptychoplasma vagans
as well as trace fossils of other invertebrate groups such as
Cruziana problematica
,
Dimorphichnus
isp.,and
Lophoctenium
isp. in the lower shoreface to off shore settings. The overall morphological and taphonomic features of the trace fossils suggest that,two major groups,including the cleft-footed(protobranchia)and wedge-footed bivalves occurred in the middle part of the Pingyipu Formation. The protobranchia were deposit-feeding bivalves distributed in the transitional zone and off shore settings. The transition from resting to “escape”state of these bivalves,probably due to erosive events or a higher sedimentation rates,produced the trace fossil
Pro. rugosa.
The wedge-footed bivalves could be further divided into two groups. The vagile,deposit-feeding type occupied the transitional zone and off shore settings. Their crawling behavior,probably linked to an effort to search for edible material from the sediment generated the trace fossil
Pty. vagans.
While in the lower shoreface setting,colonies of suspension-feeding bivalves colonized the sediment during relatively tranquil intervals between erosional events. The vertical transition of trace fossil composition in the middle Pingyipu Formation suggests a substitution of
Cruziana
ichnofacies developed on a relative stiff substrate by the latter
Skolithos
ichnofacies in an upward shallowing succession.
2023 Vol. 25 (2): 392-404 [
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405
DING Yi, ZHANG Lijun
Quantitative characterization of ichnological parameters for indicating palaeo-ocean redox conditions: a case study of the end-Permian mass extinction in South China
Major biotic and environmental events in Earth history are often accompanied by palaeo-ocean redox condition changes,as biogenetic sedimentary structures
in situ
,trace fossils play a significant role in reconstructing palaeo-ocean redox conditions. This study analyzes and summarizes the previous ichnological parameters,and suggests the ichnodiversity,bioturbation degree,burrow size,and key ichnotaxa can be quantitatively used to indicate the palaeo-ocean redox conditions. Additionally,Lopingian trace fossils and bioturbation structures in South China are systematically analysed in order to reconstruct the redox conditions during the end-Permian mass extinction. The quantitative ichnological parameters reveal that the ocean anoxic event occurs in late Wuchiapingian,and the ocean anoxia is not permanent in Changhsingian,instead,obvious periodic fluctuations between anoxic/dysoxic and oxic can be observed. The high-resolution quantitative ichnological proxies at Meishan section suggest that ocean anoxia occurs in the top of Bed 24e in the Changhsing Formation,appears to correlate with the biotic mass extinction. The above examples show that the application of ichnological parameters in the reconstruction of palaeo-ocean redox conditions has broad prospects.
2023 Vol. 25 (2): 405-418 [
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354
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419
XU Xin, XING Zhifeng, ZHENG Wei, QI Yong’an, LI Wanying, WU Panpan, ZHANG Xiangyun, WAN Enzhao, HE Junmiao, LI Da
Ichnonetwork analysis of the Lower-Middle Triassic in Jiyuan area,western Henan Province
The Lower Triassic Heshanggou Formation and Middle Triassic Ermaying Formation in western Henan Province represent terrestrial fluvial-lacustrine deposits. Six ichnospecies/five ichnogenera and nine ichnospecies/seven ichnogenera have been identified in the Heshanggou Formation and the lower-middle members of the Ermaying Formation in the Jiyuan area respectively. Based on ichnonetwork analysis,the ichnonetwork of the Heshanggou Formation and the lower-middle members of the Ermaying Formation was constructed to explore the variety of benthic metazoan after the Permian-Triassic Mass Extinction(PTME). The analysis of ichnonetwork shows that during the depositional period of the Heshanggou Formation to the lower-middle members of the Ermaying Formation,the number of nodes,the diameter,the average clustering coefficient and average path length of the ichnonetwork increase significantly. However,the average degree,average weighting degree and density of the ichnonetwork decrease slightly. The complexity of the ichnonetwork and the enhancement of the adaptability of trace makers to harsh environments of the Early and Middle Triassic ichnonetwork has become a potential sign of biological recovery after the mass extinction. Combined with previous studies,the biological recovery and ecological recovery after PTME may follow the similar pattern in North China, though this pattern still need to be corroborated and supplemented by the follow-up studies with more fossil evidences.
2023 Vol. 25 (2): 419-430 [
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323
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138
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431
XU Qingyang, FAN Ruoying, GONG Yiming
Marine ichnofossils as a record of major biodiversification events in the Phanerozoic
In this paper,we analyzed the trace fossil records of the major Phanerozoic biodiversification events,including the Cambrian Explosion,the Great Ordovician Biodiversification Event,and the Mesozoic Marine Revolution. The ichnodiversity and ichnodisparity of marine trace fossils show a positive correlation with biodiversity during these three biodiversification events. The intensity and depth of bioturbations both increased distinctly. The feeding strategies and the behavior of marine trace-makers became more complex. The most prominent change in the trace-making behavior during the Cambrian Explosion is the appearance of vertical burrows(or vertical elements in burrows). The shallow-marine ichnofauna expanded to the bathyal-marine and deep-marine environments during the Ordovician,as represented by the appearance of morphologically complex deep-marine trace fossils. It shows a further intensification of the exploitation of the marine benthic ecological niches in the Cretaceous. Characteristic change during this period is the significant diversification of deep-marine graphoglyptids,with the development of multiple morphological types and feeding strategies. Under the influences of the environment and biotic changes,marine ichnofaunas became more complicated in morphology and ethology and adopted progressively wider environmental distribution during the Phanerozoic. The marine ichnofaunas displayed increasing penetration depth,transferred from two-dimensional to three-dimensional structures,and radiated from the shallow shelf to the deep sea and continent. These features may be attributed to the process that organisms acquire ecological opportunities.
2023 Vol. 25 (2): 431-450 [
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451
LI Gaorong, WEI Fan, CONG Peiyun
Spatial-temporal distribution and diversity of the Ediacaran-Cambrian macroalgae: insights from fossil records of South China
Numerous Ediacaran-Cambrian Lagerstätten in South China provide important fossil evidence for the understanding of early evolution of life and ecosystems. Macroalgae were abundant,widely distributed,diverse in morphology,and constituted an essential part of ecosystems during the Ediacaran-Cambrian. Previous investigations on the Ediacaran-Cambrian macroalgae in South China focused on morphology,classification and palaeoecology,while their geographical distribution and diversity changes have seldom been studied in detail. In this paper,we summarize the Ediacaran-Cambrian macroalgae from the Ediacaran-Cambrian Lagerstätten of South China. The palaeogeographic distribution and genus/species diversity of macroalgae increased significantly from early to late Ediacaran,and reached the peak in the Age 5. The palaeogeographic distribution and genus/species diversity were extremely low during the Terreneuvian(Cambrian),and increased during the Epoch 2. Thereafter,the palaeogeographic range of macroalgae decreased in the Miaolingian-Furongian,and the genus/species diversity increased significantly and reached the second peak. The increase of regional marine oxygen level,which is suggested to be closely related with the availability of nutrient elements such as N and P,may be the main reason for the flourishing of macroalgae(high genus and species diversity),and the wide distribution of mud shale suitable for the fossilization of soft-bodied organisms might be an important factor controlling the geographic extension of the Ediacaran-Cambrian macroalgae in South China.
2023 Vol. 25 (2): 451-470 [
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471
WANG Xuelian, XIONG Conghui, SUN Bainian
New records of
Sphenopteris
from the Cisuralian of Yongchang,Gansu Province,with a discussion on diversity and palaeogeographic evolution of this genus during the Late Paleozoic
Although
Sphenopteris
species were widespread in the Late Paleozoic around the world,the systematic position and evolutionary characteristics of this genus still need to be addressed,and microstructures such as epidermis and stomata have only been demonstrated in very limited species. We describe two well-preserved fossil species with microstructures from the Cisuralian Shanxi Formation(Early Permian)of Yongchang,Gansu,China,including
Sphenopteris yongchangensis
sp. nov. and
Sphenopteris nystroemii.
Pinnules of
S. yongchangensis
sp. nov. were fan-shaped,with their base connected,lateral veins bifurcate once,and elliptical stomata are amphistomatic. Pinnules of
S. nystroemii
were fusiform with round top,lateral veins bifurcate once and reach leaf margin,and its stomata were distributed in interveinal area. It is more reasonable to assign the present two species of
Sphenopteris
to the order Lyginopteridales by detailed comparative analyses. The diversity and palaeogeographic evolution of
Sphenopteris
species are then considered,based on 269 occurrence records of the genus from the Late Paleozoic,in combination with morphological and anatomical characteristics and biogeographic distribution pattern. The results show that the records of
Sphenopteris
were widely distributed in the middle-low latitudes worldwide from the Pennsylvania to Cisuralian,indicating high variation and differentiation of
Sphenopteris
-type leaves. It is speculated that
Sphenopteris
species migrated from South China to North China during Late Devonian to Permian,and the diversity pattern was not only closely related to humid climate,but also coupled with the palaeogeographic characteristics of this genus.
2023 Vol. 25 (2): 471-484 [
Abstract
] (
287
) [
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1KB] [
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13343KB] (
133
)
485
LI Aijing, DU Baoxia, ZHANG Mingzhen, LIN Shaohua, PENG Jing, ZHANG Jing, LIU Guolong, JIAO-BA Dunzhu, MA Guorong, HUI Jianguo
Podozamites
(Conifers)from the Lower Cretaceous of Beishan, Gansu Province and its palaeoclimatic implications
The extinct genus
Podozamites
belongs to conifers,and is an important component of the Mesozoic flora of the Northern Hemisphere. In this study,three species of
Podozamites
were reported from the Lower Cretaceous of the Beishan area,Gansu Province,China,including
Podozamites
sp.,
Podozamites
aff.
distans
and
Podozamites bullus.
On the basis of the global records and palaeogeographic distribution of the
Podozamites
species,as well as palaeoclimatic zones of the Mesozoic,the palaeoclimatic significance of this genus is addressed. The results show that
Podozamites
were more abundant and mainly distributed in warm and humid climate zones of the northern Hemisphere during Late Triassic to Middle Jurassic. The abundance of
Podozamites
declined,along with the expansion of arid climatic zones,and the distribution also migrated along with warm-humid climatic zones during the Late Jurassic to Early Cretaceous. The palaeogeographic distribution of
Podozamites
species was mainly influenced by shifts of warm-humid climatic zones during the Mesozoic.
Podozamites
might have been more adaptive to warm and moist conditions and thus can serve as an indicator genus of warm-humid climates.
2023 Vol. 25 (2): 485-496 [
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302
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2536KB] (
134
)
497
ZHANG Mingzhen, LIU Guolong, DAI Shuang, CHEN Shiqiaing, LI Aijing, JIAO-BA Dunzhu, ZHANG Jing, LIN Shaohua
New scheme for subdivision and age determination of the Lower Cretaceous of Beishan area near Gansu-Inner Mongolia border,China
Many small inland sedimentary basins,rich in coal,uranium,hydrocarbon and others, developed during the Early Cretaceous in Beishan area at the Gansu and Inner Mongolia border area. However,the chaotic subdivision of lithological stratigraphic systems and unclear age determination have seriously hindered resource exploration in recent years. Based on the stratigraphical and palynological data collected from boreholes and outcrop sections,the Lower Cretaceous Laoshuwo Group of this area was divided into three formations in an ascending order,including the Tuomatan Formation,the Tianshuijing Formation(a new name)and the Mazongshan Formation(a new name). The former two formations are probably in an unconformity contact. The Tuomatan Formation is mainly composed of dark gray,dark gray-green coal-bearing mudstone,siltstone and coarse sandstone,containing
Aequitriradites
that are common in the early Early Cretaceous.
Cicatricosisporites
that are more common in middle Early Cretaceous are rare in the Tuomatan Formation indicating the age of this formation is the earliest Early Cretaceous(probably late Berriasian to early Valanginian). The Tianshuijing Formation is characterized by gray-green fine-grained mudstone and siltstone,and rich in
Ephedripites
and
Cicatricosisporites
,indicating an age of middle Early Cretaceous(probably Hauterivian-Barremian). The Mazongshan Formation is characterized by purple-red,light-gray fine-grained siltstone,in which a few tricolpate pollen records of early angiosperms indicate a late Early Cretaceous age(probably Aptian-Albian). This new stratigraphic system in the Beishan area at the Gansu and Inner Mongolia border area will provide reference for later resource exploration and basic research.
2023 Vol. 25 (2): 497-510 [
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327
) [
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5798KB] (
139
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511
2023 Vol. 25 (2): 511-511 [
Abstract
] (
371
) [
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1KB] [
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4074KB] (
133
)
512
2023 Vol. 25 (2): 512-512 [
Abstract
] (
272
) [
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1KB] [
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325KB] (
154
)
513
2023 Vol. 25 (2): 513-513 [
Abstract
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259
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1KB] [
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250KB] (
150
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