云南东部江川生物群中的香肠状疑难化石——Tawuia化石属性的新解释     

李玉兰  王浩  刘傲然  李明  梁永忠  周颖  唐烽  任留东 《地质论评》2022,68(4):2022082009-2022082009

云南东部伊迪卡拉（震旦）系顶部灯影组旧城段的江川生物群是华南又一大类丰富且多样化的宏体化石群,其以碳质压膜的方式保存。在该生物群中,我们发现大量香肠状碳质压膜的宏体化石,与成冰(南华）纪全球大冰期之前中、新元古代地层中广泛分布的Tawuia碳膜化石的大小、形态非常相似。其最大宽度达4. 5 mm,最大长度可达4 cm,长宽比均>2,膜面光滑,未见其他稳定纹饰,有的化石标本边缘碳质保存较多,可见深黑色边缘环带。但部分化石保存的形态与常见的直棒状I形、U形、C形Tawuia化石相比却较为特殊,呈现直角L形、8字形、宽U形、环状O形等多种保存形态,个别标本弯折部位可见明显的碳质增厚和横脊纹残留,边缘残存有大小不一的刺状突起构造。这类特异形态保存的似Tawuia化石显然不能解释为以往较为公认的浮游型叶状体藻类,而可能与冰期前的新元古代早期鲁西、淮南宏体化石群中的疑似蠕形动物亲缘的化石有传承关系。上述新发现的化石形态表明：似Tawuia的碳膜宏体化石可能是多源属性的早期多细胞生物。其中短带至长带状叶状体,可见短柄突起及疑似固着器构造的化石可确认为底栖宏体藻类;多数的叶状体推测为香肠状或长囊状,生活史中包含远洋浮游的类型,可能归属于原始不分枝的多核体藻类或早期分化出的中空囊状的多细胞藻类;本文展示的部分规则变形的似Tawuia化石,更可能是两侧对称动物亲缘的,生活于近海的底栖生物体发生主动扭曲后,被特异埋藏所呈现出的特殊保存形态,而随机浮游或表栖的多细胞藻类死亡沉积时不会形成类似形态的化石。  相似文献   

New Data of Macrofossils in the Ediacaran Wenghui Biota from Guizhou, South China     

WANG Ye  WANG Yue  DU Wei  WANG Xunlian 《《地质学报》英文版》2016,90(5):1611-1628

The abundance and diversity of macrofossils in the Ediacaran have attracted much attention. The upper Doushantuo macrobiotas in South China, including the Miaohe biota from Hubei and the Wenghui biota from Guizhou, are mainly preserved as the carbonaceous compressions and dominated by macroscopic algae and metazoans. Here, we describe 10 genera and 10 species (including 6 new genera and species) of macrofossils from the Wenghui biota. At present, the Wenghui biota yields macrofossils in more than 31 genera and 33 species, excluding those given no image and established on a few unascertained specimens. Based on the occurrence and distribution of macrofossils in both Miaohe and Wenghui areas, the middle-late Ediacaran (back shales of the upper Doushantuo Formation) in South China can be subdivided into two assemblage biozones in biostratigraphy: (i) the Protoconites–Linbotulitaenia–Eoandromeda–Anomalophton assemblage biozone characterized by abundant and diverse macrofossils and by the ranges of Protoconites, Linbotulitaenia and Anomalophton; and (ii) the Baculiphyca–Gesinella–Cucullus–Beltanelliformis assemblage biozone characterized by the acme of the longer macrofossils Baculiphyca and Gesinella, and by few shorter and discoidal macrofossils.  相似文献   

寒武纪叶足动物:困惑与思考     

欧强 《地学前缘》2020,27(6):47-66

叶足动物在显生宙最早期的海洋中曾一度繁盛,但如今茫茫大海中它们已杳无踪影。不过,学术界主流认为它们并没有绝灭——早期叶足动物的一个分支成功演化出原始的节肢动物,成就了当今地球上最庞大的动物家族(六足类、甲壳类、多足类、螯肢类等);叶足动物另一个分支则离开海洋,保持基本躯体构型,变身为陆生叶足动物,然而历经沧桑后,仅余一两脉(有爪动物及缓步动物)残喘幸存至今。这个史诗般的精彩演化故事,深深吸引了众多学者竞先求索。近30年来,以我国云南澄江生物群为代表的一系列寒武纪特异埋藏化石库中发现了大量叶足动物化石。经研究,学术界迄今似已破解了早期叶足动物重重疑团,足以额手称庆。然而治学须严谨,考证不偏狭。作者认为,围绕早期叶足动物的迷雾尚未消散,许多问题还有待解答,部分观点仍需确证。本文对早期叶足类研究的部分主流观点提出一些不同看法,并对尚未破解的疑难问题提出尝试性的见解和猜想。  相似文献   

Distribution of selenium and arsenic in differentiated multicellular eukaryotic fossils and their significance     

《地学前缘(英文版)》2020,11(3):821-833

We present variation patterns of trace elements within different sequences of the Ediacaran Doushantuo Formation(DST,635-551 million years ago),and inside the cells of the earliest differentiated multicellular eukaryotic fossils of the Weng'an biota in the Weng'an County of Guizhou Province.The results showed that selenium is the most enriched and significantly varied trace element among the 22 trace elements throughout the DST,followed by arsenic.The highest selenium and arsenic content sequences are consistent with the first appeared sequence of the earliest differentiated multicellular eukaryotic fossils Megasphaera at the middle to upper parts of the DST.Nanoman secondary ion mass spectrometry analyses show that selenium and arsenic have an inhomogeneous and punctate distribution in the nucleus and cytoplasm.The nucleus has anomalously enriched levels of selenium and arsenic among the organelles.The selenium and arsenic concentrations exhibit a positive correlation with the diversity of fossilized Megasphaera.These new findings give us a clue that the anomalous enrichment of selenium and arsenic might contributes to the cell differentiation in Ediacaran Doushantuo period.  相似文献   

A rigid-bodied Ediacaran Biota from Upper Cambrian strata in Co. Wexford,Eire     

T. P. Crimes  A. Insole  B. P. J. Williams 《Geological Journal》1995,30(2):89-109

Two typical representatives of the Ediacaran biota, Ediacaria booleyi n.sp. and Nimbia occlusa have been found in deep-water turbidites within the Upper Cambrian Booley Bay Formation at Booley Bay in Co. Wexford, Eire. The examples of E. booleyi were transported over short distances by the turbidity currents and then impacted, in some instances at high angles, into the ocean floor muds where they formed moulds but, as their bodies decayed, these were filled by casting sand from the overlying turbidite. They preserved fine detail during transportation and impaction, thereby indicating the existence of a rigid body wall. The three-dimensional nature of their preservation allows reconstruction, which shows that Ediacaria had a discoid form with prominent relief, particularly on its dorsal side, which was divided into three main concentric zones with thin radial features, more evident at the periphery. The ventral side had lower relief, with alternate areas of coarse and fine concentric markings and numerous fine radial lines, some also thicker at the periphery. Nimbia occlusa are disc-like bodies of low relief and occur in profusion on one sole. Some show a circular outline indicating that they were preserved flat on the bedding plane, but others occur as semicircular reliefs oriented in the palaeocurrent direction. This indicates that they too were moved by the turbidity current, but their abundance and excellent preservation indicate that transport distances were short. There is no evidence in either genus for the coelenterate characteristics of a mouth and a two-layered body wall enclosing a single cavity. This, and the evidence for a rigid outer wall, adds to recent doubt on the concept of the world-wide Ediacaran fauna as dominated by soft-bodied coelenterates.  相似文献   

陕南西乡寒武纪梅树村期微古生物群产出层位的地球化学特征及古环境和古气候条件研究     

刘阳  邵铁全  刘云焕  赵雨豪  张亚楠  秦嘉琛  王琪  李林璐  周星宇  刘明金 《地质论评》2022,68(1):309-322

陕南西乡微体化石对于研究寒武纪大爆发具有非常重要的意义,前人研究大都局限于微体古生物的研究,而化石的成岩背景以及古环境研究尚属空白.因此本文通过测试主微量稀土元素及氧同位素来分析研究区的古沉积环境,在一定程度上填补了这一区域的空白.研究手段虽然在地化领域比较常见,但具有重要的参考价值.本文通过对富含小壳化石的"宽川铺段...  相似文献   

带生物泵三维全球海洋碳循环模式   总被引：10，自引：1，他引：9  

邢如楠 《大气科学》2000,24(3):333-340

建立了一个带生物泵的三维全球海洋碳循环模式,该模式在海气界面上与一个CO2充分混合的大气箱进行CO2交换,模式积分1 200年达到准稳定态的海水总CO2、碱度及溶解氧的浓度、表层新生产力、海气分压差等的分布与实测相接近。通过带生物泵和不带生物泵的对比实验,表明海洋生物过程在海洋吸收大气中CO2能力上起着重要作用。  相似文献   

Compound-specific stable carbon isotope analysis as a tool for correlating coal-sourced oils and interbedded shale-sourced oils in coal measures: an example from Turpan basin, north-western China   总被引：1，自引：0，他引：1  

Yongge Sun  Guoying Sheng  Ping'an Peng  Jiamo Fu 《Organic Geochemistry》2000,31(12)

Molecular geochemical methods have shown that it is often difficult to differentiate between coal- and interbedded shale-sourced oils, even though coals and interbedded shales may exhibit considerable organic influx variation (e.g. land plant vs algal organic matter) due to the changes of depositional setting. However, compound-specific stable carbon isotopic compositions are sensitive to the source input variations. Typically, specific molecules are more depleted in ¹³C with increasing content of aqueous biota. This hypothesis is examined and exemplified by comparing the stable carbon isotopic ratios of n-alkanes from source rock extracts and related oils of the Turpan basin, north-western China. Stable carbon isotopic values of n-alkanes extracted from coals and interbedded shales show that δ¹³C values of n-alkanes with less than 20 carbon atoms vary only slightly. However, there are dramatic changes in the isotopic compositions of higher molecular weight n-alkanes. Furthermore, n-alkanes from coal extracts are enriched in ¹³C relative to that of interbedded shales with excursions up to 2–3‰. This comparison enables the differentiation of coal- and interbedded shale-sourced oils, and provides information useful in assessing the hydrocarbon system of a basin.  相似文献   

贵州瓮安陡山沱期矿化生物群的研究进展和意义   总被引：8，自引：2，他引：8  

尹崇玉  高林志  邢裕盛 《地球学报》2002,23(1):47-54

贵州瓮安陡山沱期矿化（磷酸盐化和硅化）生物群的研究近年来倍受关注，它为研究包括后生动物在内的多细胞生物早期演化提供了十分难得的机遇。最近，由于其中部分磷酸盐化球状化石保存了与某些后生动物胚胎早期发育阶段类似的卵裂特征，被认为是后生动物的休眠卵和胚胎化石。但是，由于至今未发现可靠的囊胚期到原肠胚期和幼体孵化的化石证据，此类化石的动、植物之争一直没有停止。作者近期对该套含磷地层进行了系统的分析研究，除已报道的大量休眠卵和胚胎化石外，还发现保存原肠发育特征的磷酸盐化实体化石、蓝藻细胞集合体、可疑海绵动物化石及类似瓶形的不明化石等。研究表明，陡山沱期矿化生物群具有多样性特征，包含了多种门类的不同类型，是迄今为止全球保存最完好的未元古纪磷质化石库。  相似文献   

陕西新元古代末期奇异骨骼化石新发现及其意义   总被引：4，自引：0，他引：4  

华洪  张录易  谢从瑞 《地球学报》2002,23(5):387-394

陕西宁强新元古代末期灯影组高家山段上部发现与Cloudina,Sinotubulites等管状动物骨骼化石共生的大量微体奇异骨骼化石，其中的一些似与寒武纪早期的小壳化石有一定的亲缘，如形态奇特的铆钉状化石、腹足类化石等，证实寒武纪与前寒武纪生物界之间存在明显的连续性；奇异骨骼与陡山沱期生物也存在一定的相似性，如一些分枝的管状化石，这一化石组合具有承前启后的作用。该组合包含了可能的矿化后生藻类（具各种分枝类型）、矿化的蓝绿藻类化石等。种种迹象表明，在新元古代末期整个生物界发生了一次强烈的生物矿化事件，这一发现弥补了国内外新元古代末期矿化后生植物资料的空缺；磷酸盐化球状化石的研究已成为国内外研究的热点，本文所展示的球状化石由于形态多样，数量众多，内部结构各异，对其进行深入研究，可望在后生动物起源和早期演化研究方面取得突破。  相似文献