Paleoceangraphic significance of redox-sensitive metals of black shales in the basal Lower Cambrian Niutitang Formation in Guizhou Province, South China

TheLowerCambrianblackshalesequenceoccursinSouthChinaalonganarc parallellinearbeltex tendingmorethan 16 0 0km .Theseorganic richblackshalesformedinvariousmarineenvironmentsandtypicallycontainhigheramountsofmolybdenum ,nickel,vanadium ,andanumberofothereconomical lyimportantmetalsthandoanyothersedimentaryrocks[1,2 ] .Therefore ,thestudyoftheseblackshaleshasnotonlypaleoceangraphicimplicationbutalsoe conomicsignificance .Marinesedimentssuchasblackshalearecom plexmixturesofdetritalphasesandseawat…     

Re-Os isotopes and PGE geochemistry of black shales and intercalated Ni-Mo polymetallic sulfide bed from the Lower Cambrian Niutitang Formation, South China

The paleo oceanenvironmentalchangeduringthePrecambrian Cambriantransitionisakeyissuere latedtothecausesforanexplosiveradiationofdiffer entmetazoanphyladuringtheEarlyCambrianera .Thechemicalandisotopiccompositionsofmarinesed iments (carbonates ,phosphorites ,siliceousrocks ,andblackshales)recordthechangingcompositionandphysicalconditionsoftheseawaterinwhichtheserocksaccumulated .Organiccarbon richblackshalesfrommarineenvironmentsarecommonlyenrichedinanumberoftraceelementssuchasNi,Mo ,V ,Co ,…     

Discovery of phosphatized gastrula fossils from the Doushantuo Formation, Weng’an, Guizhou Province, China

Globular fossils from Doushantuo phosphorites at the Weng’an area are for the first time identified as a gastrulation stage of phosphatized embryos. They are got from the fossiliferous remains after acetic acid maceration. The fossils are found together with formerly reported animal resting eggs and embryos of the earlier cleavage stage. The oblate-shaped fossils with the same size as those reported embryos and invaginate at the middle part into the embryos, show the characteristics of the late blastula to the early gastrula stage of the embryo development. This discovery convinces the existence of animal embryos at Doushantuo age and offers new facts for the studying of the affinity of related fossils, which are still controversial at present.     

Stable isotopic geochemistry of organic carbon and pyrite sulfur from the Early Cambrian black shales in Northwestern Hunan, China

The early Cambrian black shale sequence in Northwestern Hunan Province has been investigated for its stable isotopic geochemistry of organic carbon and pyrite sulfur. The relatively low δ 13C values of organic matter, -29.7‰～-34.2‰, are interpreted as caused by the high CO2 concentration in atmosphere/ocean and an anoxic depositional environment in early Cambrian. Variable, but significantly positive δ 34S values, 10.2‰～ 28.2‰, for sedimentary pyrite reveals bacterial sulfate reduction as the pyrite-forming process but under sulfate-limited conditions. A protected anoxic basin, which had very limited access to open ocean, and its sediments, where metabolizable organic matter was rich and bioturbation was absent, are supposed to be the sulfate-limited environments and might have existed in South China in the early Cambrian.     

Discovery of the budding phosphatized globular fossils from the Neoproterozoic Doushantuo Formation at Weng’an, Guizhou Province, China

There is much debate on biological affinities of the phosphatized globular fossils from the Neoproterozoic Doushantuo phosphorites at Weng’an, Guizhou Province. Here we report for the first time the budding structures of some of these globular fossils, which have previously been interpreted as the resting eggs and early cleavage embryos of metazoans. The budding structures are similar to the germinating tubes of the spore and zygote of living algae, suggesting that some globular fossils from the Doushantuo phosphorites bear affinity with algae. The present new information indicated various biological affinity of the phosphatized globular fossils from the Doushantuo phosphorites.     

Lower Cambrian yolk-pyramid embryos from Southern Shaanxi, China

TheCambrianexplosioniswidelyacceptedasthesuddenappearanceofnumerousbilateriananimalphylaatornearthebeginningofCambriantime[1,2 ] .The 5 30 million year oldMaotianshanShalefaunacontainstheoldestgoodwhole bodyfossilsofbilateri ans,documentinganincreasingnumberofpresent dayanimalphyla[3,4 ] orsubphyla[5] (evenincludingvertebrates[6～ 8] aswell)knownfromLowerCambri an .ThebeginningoftheCambrianperiodisdatedat5 43millionyearsago ,whenthefirstlargeandelabo ratefossilburrowstogetherwiththemicrosco…     

Primitive deuterostomes from the Chengjiang Lagerst?tte (Lower Cambrian, China).

Cambrian fossil-Lagerst?tten (sites of exceptional fossil preservation), such as those from Chengjiang (Lower Cambrian) and the Burgess Shale (Middle Cambrian), provide our best window into the Cambrian 'explosion'. Such faunas are known from about 40 localities, and have yielded a widely disparate series of taxa ranging from ctenophores to agnathan fish. Recent excavations of the Chengjiang fossil-Lagerst?tte, known from a series of sites near Kunming in Yunnan, south China, have resulted in the discovery of several new forms. In conjunction with material described earlier, these provide evidence for a new group of metazoans, the vetulicolians. Several features, notably a series of gill slits, suggest that this group can throw light on an early stage of deuterostome diversification.     

Discovery of sponge body fossils from the late Meishucunian (Cambrian) at Jinsha, Guizhou, south China

Here we report discovery of a sponge body fossil Triticispongia sp. from the base of lower Cambrian Niutitang Formation at Jinsha, Guizhou. Stratigraphically, the fossil horizon is located below Ni-Mo ore layer with the Niutitang Biota above, and is equivalent to the late Meishucunian. The species is global in shape with skeletons composed of stauractins and monaxons. Triticispongia sp. reported here may be the earliest sponge body fossils of Cambrian, which provides new information for understanding early evolution and radiation of sponge animals.     

The Balang Fauna―A new early Cambrian Fauna from Kaili City, Guizhou Province

In April 2004, Wu Yishan, a teacher from Kaili No. 4 Middle School, took his students to Wenglingtang to con-duct popular science activities. They found fossils of trilo-bites and eocrinoids in gray and gray-greenish silty shale, and calcareous, silty mudrock in the upper part of the lower Cambrian Balang Formation. In May 2004, we were invited to investigate the new discovery. Through several field investigations, we measured the stratigraphic section and collected numerous trilobite and…     

贵州遵义下寒武统牛蹄塘组生物群中的海绵化石

遵义松林中南村下寒武统牛蹄塘组中下部,特别是下部黑色泥岩中产有大量的海绵骨针,形态多样,初步研究有多达10属以上的海绵动物,与澄江生物群的海绵相比,牛蹄塘组的海绵动物化石其组合特征以六射海绵动物为主,它的发现增添了寒武纪生物组成的信息,为海绵动物从晚新元古代的发生以至穿越寒武纪的演化过程及寒武纪生物大爆发的定性,量度提供了重要信息及资料,描述了4属2个种。1个相似种和1个未定种。Hyalosinica sp.;Saetaspongia densa Mehl et Reitner,1993;Leptomitus teretiusculus CHen,Hou et Lu.1989;Crumillospongia cf.biporosa Righy,1986,它们分属于海绵动物的六射海绵纲和普通海绵纲。     

贵州地区下寒武统牛蹄塘组黑色页岩地质特征及其油气资源意义

贵州地区下寒武统牛蹄塘组黑色页岩发育广泛,并受该区早寒武世岩相古地理类型的控制,主要发育在中、东部地区的页岩盆地相地区中,少部分发育在页岩盆地相和碎屑岩台地相的过渡相中,极少发育在西部的碎屑岩台地相中.研究区牛蹄塘组黑色页岩沉积环境为缺氧还原性沉积环境,有机质母源主要为水生低等菌藻类生物,并混有少部分陆源高等植物.研究区牛蹄塘组黑色页岩具有有机质丰度高、母质类型好、有机质转化为烃类能力强的特征,显示出较大的生烃潜力和油气资源意义.但其高演化阶段作为成油的烃源岩意义不明显,作为成页岩气的源岩则前景乐观.     

黔南下寒武统喳拉沟组黑色岩层风化特征

黑色岩层是一种广泛分布且具有特殊性质的岩石,探讨黑色岩层的风化特征,为黑色岩层边坡治理提供理论依据。选取黔南三都地区下寒武统喳拉沟组黑色岩层为研究对象,利用浸泡试验、水质分析试验模拟黑色岩层的水岩化学作用过程,通过黑色岩层风化中的矿物特征、化学成分特征来确定其风化阶段。研究结果表明:研究区黑色岩层在水岩作用中涉及多个复杂的化学过程,通过溶解、水解、水合作用逐步形成稳定的黏土矿物及次生矿物;黑色岩层的化学风化已完成去Na、Ca阶段,并初步进入中期的去K风化阶段。     

渝东南牛蹄塘组页岩成岩作用及其对孔隙的影响

以渝科1井钻遇的下寒武统牛蹄塘组页岩为研究对象,探讨渝东南地区过成熟页岩中成岩作用对孔隙发育的影响。伊利石结晶度和等效镜质体反射率Ro测定,显示牛蹄塘组页岩处于有机质过成熟的晚成岩阶段。通过场发射扫描电镜和气体吸附实验对页岩孔隙进行了定性和定量表征。页岩孔隙主要由有机质孔隙、粒内孔隙和粒间孔隙组成,以中孔为主,平均直径为4.93nm,总孔体积平均为0.014 3cm~3/g。牛蹄塘组页岩经过强烈的压实作用和胶结作用使得粒间孔隙欠发育。黏土矿物大多已伊利石化,伊利石平均质量分数为86%,伊蒙混层平均质量分数为13%,黏土矿物中的孔隙以伊利石中的粒内孔隙为主。溶解作用使得碳酸盐矿物产生粒内孔隙和粒间孔隙,孔隙直径较大。有机质成熟作用产生了有机质孔隙,随着有机质成熟度的进一步增加,有机质内的有机质孔隙体积和孔隙直径都不断减小。页岩的孔隙因不同成岩作用的共同改造而变化。     

δ13Ccarb and Ceanom excursions in the post-glacial Neoproterozoic and Early Cambrian interval in Guizhou,South China

Secular δ 13Ccarb and Ceanom profiles in the post-glacial Neoproterozoic and Early Cambrian interval are reported from Guizhou on the southeasten border of the Yangtze platform, South China. Overall, the δ 13Ccarb profile drifts to negative values in the post-glacial Nantuo and lower to middle Doushantuo Formations, and then to positive values in the upper Doushantuo and Dengying Formations of Neoproterozoic, followed by negative values in the Lower Cambrian Gezhongwu and Niutitang Formations. A detailed investigation of the relationship between the δ 13Ccarb and Ceanom profiles reveals that the main anoxic and oxic episodes are coupled with negative and positive δ 13Ccarb values, respectively. This may suggest a control of alternation between ocean stratification and mixing on variations in 13C abundance in the ancient ocean of the investigated areas.     

贵州剑河八郎凯里组的顾脱贝Kutorgina Billings,1861

贵州剑河八郎凯里生物群腕足动物分异度大,多达11属12种,包括舌形贝亚门8属及小嘴贝亚门3属。其中小嘴贝亚门中的顾脱贝(未定种)Kutorgina sp.,壳体较大,平凸型,外形正五边形或横椭圆形,最大宽度位于壳体中央,喙部轻微弯曲,同心层最多可多达32层,背壳未见中隆,相似于澄江化石库的澄江顾脱贝Kutorgina chengjiangensis及关山生物群中的Kutorgina.sp。凯里组顾脱贝的产出及研究,丰富了中国及全球寒武纪顾脱贝的信息。