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晚二叠世-中三叠世在中亚造山带东段构造演化过程中是承上启下的关键地质时期,所以晚二叠世林西组沉积环境对研究古亚洲洋闭合这一重大问题具有重要意义。大兴安岭地区晚二叠世林西组曾有双壳、叶肢介、植物及孢粉化石记录,但鲜有介形虫化石报道。在大兴安岭中段林西组研究中首次发现介形虫化石,经初步研究,主要分子有Kemeroviana,Volganella,Iniella,Qitaina,Darwinuloides,Palaeocypridopsis,Tomiella,Darwinula和Urumqiella等,暂划为Volganella-Kemeroviana组合,其时代为晚二叠世。与俄罗斯地台晚二叠世介形虫化石群关系较为密切,部分属种曾见于我国新疆准噶尔盆地和塔里木盆地。从介形虫化石组合特征和保存特点来看,其生存环境为淡水湖泊,故认为这一地区的林西组为陆相沉积。 相似文献
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贵州境内寒武系黔东统都匀阶清虚洞组富含具有重要地层意义的三叶虫莱得利基虫,前人据此将该组由下而上划分为2个三叶虫带:Redlichia(Pteroredlichia)murakamii-Hoffetella-Eoptychoparia组合带和Redlichia(Redlichia)guizhouensis-Redlichia(Redlichia)nobilis富集带。对黔东剑河八郎地区松山剖面非典型的"清虚洞组"中大量的莱得利基虫化石进行了初步研究,根据分类和属种延限,识别出Redlichia(Pteroredlichia)murakamii带和其上的Redlichia(Redlichia)guizhouensis-Redlichia(Redlichia)nobilis组合带。Redlichia(Pteroredlichia)murakamii带的底界可下延至下伏地层杷榔组中上部,但带内未发现常见于黔北地区典型清虚洞组的Hoffetella。剑河八朗松山剖面"清虚洞组"上述两个莱得利基虫化石带可以分别与此前建立的两个掘头虫三叶虫带Arthricocephalus chauveaui带和Protoryctocephalus arcticus带对应,进而为斜坡相区的"清虚洞组"与浅水台地相区同期地层的生物地层对比提供化石依据。 相似文献
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该区晚二叠世分合山和大隆两个组。文章从岩石特征,沉积构造、古生物化石群组和遗迹化石方面论述了其沉积环境特征。合山组在桂中地区为含煤岩系,煤层顶底板是灰岩和硅质岩。古生物化石较单一,以裸松藻科为主,有少量有孔虫、(竹蜓)、介形虫和腕足类海百合的碎屑。遗迹化石以居住潜穴Skolithos为主。研究证明,合山组属低能潮坪环境。大隆组在该区出露不足10m,以凝灰岩、硅质岩和硅质泥岩为主。浊流沉积特征明显以鲍马层序中A.C.E段最为发育。并在硅质泥岩中,发现半深水遗迹化石Chondrites,Planolites和Rind Burrow等,说明大隆组属深水或半深水沉积环境。合山与大隆两组的接触界线不清,尚待研究。 相似文献
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关于安徽贵池地区坟头组的时代 总被引：1，自引：0，他引：1
贵池地区坟头组,以往未发现过鱼类化石,1975年笔者等曾在贵池县杨桥公社铁岭铺,测制了坟头组上段剖面,在其中发现了丰富的鱼类化石,还采得丰富的腕足类、腹足类、双壳类、介形虫、三叶虫、棘皮动物等化石。鱼类化石经南京大学地质系夏树芳鉴定有:江苏鱼、棘鱼等。由于这些化石的发现,对于 相似文献
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1978年,笔者在新疆婆罗科努山果子沟老公路下奥陶统赛里木组底部,发现并采集了一批三叶虫,也就是本文所描述的三叶虫。1979年在果子沟将军沟东侧及精河县科古琴相同层位亦发现了这一新三叶虫。因为化石非常奇特以致难以确定它是否属于三片虫纲,所以一直未进行描述,经请教卢衍豪、张文堂、项礼文、林天瑞等诸教授,都认为它归属应于三叶虫纲。经笔者研究取名为:西城西域盾壳虫(新属、新种)Xiyuaspis xiyuensis(gen.et sp.nov.),并建立西域盾壳虫科(新科)Xiyuaspidae(family nov.)更高一级的分类暂未确定,可能为新目、新亚目。 相似文献
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贵州剑河八郎寒武系黔东统清虚洞组由泥岩和灰岩组成,厚约300m,沉积相属于黔东陆棚深水过渡相区沉积类型,不同于黔西以浅水台地相白云岩和灰岩为主的典型清虚洞组类型。该组三叶虫化石丰富,包括莱德利基虫目Redlichia(Redlichia)guizhouensis,R.(R.)nobilis;褶颊虫目对沟虫科Eoptychoparia jinshaensis,Antagmus dapingensis,褶颊虫科Nangaops brevis;耸棒头虫目叉尾虫科Olenoides hupeiensis,Kootenia sp.,以及掘头虫类中的掘冠虫科Ovatoryctocara sp.,掘头虫科Changaspis elongata,C.cf.elongata和飞龙山虫科Duyunaspis cf.duyunensis;共计9属7种2相似种及2未定种。本文描述了其中具重要地层意义的掘头虫类三叶虫3属4种,包括2未定种。结果表明,在黔东清虚洞组发现的掘头虫类Changaspiselongata和Duyunaspis cf.duyunensis,此前仅报道于该组之下的杷榔组,现这两种的层位可上延至清虚洞组上部;同时显示该组Ovatoryctocara sp.和凯里组下部的Ovatoryctocara granulata比较相似,有可能是Ovatoryctocara granulata的祖先种。掘头虫类三叶虫的新资料将有助于促进国际寒武系第3统底界层型剖面及点位(GSSP)的进一步研究。 相似文献
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石炭纪时期有孔虫具有演化快、分布广、数量丰富、分异度高的特点,对于地层的划分对比具有极为重要的意义。与全球其他重要的石炭纪沉积区相比,华南有孔虫生物地层划分精度相对较低。本文首次较为系统地报道了华南石炭系代表性岩石地层单位旧司组和上司组下部丰富的有孔虫化石及其在剖面上的分布情况,并综合现有关于华南的有孔虫化石资料,将华南维宪阶划分为7个有孔虫化石带,自下而上分别为Eoparastaffella simplex带、Viseidiscus/Planoarchaediscus带、Paraarchaediscus带、Pojarkovella nibelis带、Koskinotextularia带、Bradyina带和Janischewskina带。这些有孔虫带可与全球其他典型的石炭纪沉积区进行很好的对比,从而为相关的研究提供一个较为精细的地层格架。通过对黔南上司地区有孔虫的研究,提议中国石炭系区域性年代地层单位上司阶底界可用有孔虫Bradyina的首现定义,并将上司阶与西欧的Warnantian亚阶中上部和俄罗斯的Aleksinian亚阶—Venevian亚阶对比,对应国际维宪阶上部,为全球石炭系年代地层对比提供了可靠的化石依据。 相似文献
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Distribution, morphology, and origin of sedimentary furrows in cohesive sediments, Southampton Water 总被引：1，自引：0，他引：1
ROGER D. FLOOD 《Sedimentology》1981,28(4):511-529
Patches of sedimentary furrows are developed at several locations in the cohesive estuarine sediments of Southampton Water (water depth 1–12 m). These furrows apparently result from short periods of erosion followed by long periods of deposition. Although all the furrows are similar, regularly spaced, parallel troughs, 0.5–15 m wide aligned with the dominant current, furrows in different patches have different characteristics. In some areas furrow width is 1/5–1/15 of furrow spacing (termed ‘narrow’), whereas in other areas furrow width is about 1/2 of the spacing (termed ‘wide’). Narrow furrows have developed where sediment accumulation rates are greater than 3–6 cm yr?1; wide furrows where accumulation rates are lower. Cockle shells, and other coarse sediments, concentrated on the furrow floors and on floors of smaller (2–10 cm wide) minifurrows, play an important role in furrow formation and evolution as they act to widen the furrows when mobilized during current episodes. Uniform sedimentation across the profile during slack periods tends to narrow the furrow. Some of the larger furrows have remained in the same position for 12 years, while mini-furrows have duration scales of a few months or less. Well-developed furrows are also found in a recently dredged channel. Bedforms similar to those described here may be preserved in the sedimentary record. While no analogues to the larger furrows are presently known, minifurrows may be morphologically similar to the ‘gutter casts’ described from ancient rocks. 相似文献
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Sedimentary furrows in fine-grained sediments have been observed in a variety of settings ranging from the deep ocean and
deep lake bottoms to shallow estuaries and are commonly described as persistent, long-term features of the seabed. A series
of 12 sidescan sonar surveys over the course of three years reveal that transient, longitudinal sedimentary furrows regularly
form and then occasionally dissipate within the middle portion of the York River. Varying furrow morphologies were observed
depending on current conditions, ranging from large regularly space (0.7–7 m) linear furrows during low current conditions
to large patches of meandering furrows as the mean current increases or no bed forms during the higher current conditions.
Based on210Pb and137Cs profiles of kasten cores, differences in physical mixing depths of ∼25 cm between cores collected <2 m apart indicate a
high degree of small-scale spatial heterogeneity within the seabed. By documenting the position of kasten cores using a digital
sidescan sonar system, we showed that a core taken within a furrow had a mixing depth 15 cm shallower than an adjacent core
taken between furrows. A time-series of mixing depths over the 35 mo of the study reveals that, along with the ∼25 cm scale
differences in mixing depths due to the formation and destruction of furrows, there is a longer temporal signal of mixing
producing 100-cm-scale changes in mixing depths on the annual to interannual time frame. Although the formation and destruction
of the furrows appear to be a significant process contributing to decimeter-scale seabed mixing, there is a longer-term unknown
process which is controlling the meter-scale seabed mixing. 相似文献
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Water and water related matters are important issues in water scarce countries like the Republic of South Africa. This is
especially true for the agricultural sector that relies heavily on the availability of water for irrigation to ensure a secure
food supply. In South Africa, present day irrigation projects rely on government subsidies and are usually large undertakings
beyond the reach of individuals or small communities. The sustainability of such large irrigation projects is still a matter
of debate. A 100 years ago a different set of rules applied. Irrigation could only be achieved by hand-dug furrows that supplied
water in relatively small quantities to small farming communities. This paper investigated such a small community, the Leeukloof
farming community in the Western Cape Province of the Republic of South Africa. For the past 93 years this community has maintained
a furrow that supplies water not only to farms bordering the Perdeberg River, which supplies the furrow with water, but also
to farms not bordering the river. The authors try to reconstruct the changes in agricultural practices brought about by the
furrow, methods of water extraction during each phase, as well as the development and role of the furrow system. The perception
by the community of the necessity of this method of water extraction from the river system is also investigated.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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为进一步探明沟灌二维土壤水分运动规律,以非饱和土壤水分运动理论为基础,建立了沟灌土壤水分运动数学模型,用多组试验资料对模型模拟结果进行验证,两者基本吻合,表明模型可用于模拟沟灌二维土壤水分入渗过程.用所建模型对不同因素组合下沟灌土壤湿润体特性进行模拟分析,结果表明:土壤初始含水率、沟间距对沟灌累积入渗量影响较小,土壤质地、容重、沟底宽和沟中水深对其影响较为显著;沟底宽、土壤初始含水率对土壤湿润体水分分布影响较小,土壤质地、容重对其影响较大,沟间距、沟中水深对其影响主要在零通量面附近,当入渗发生交汇后,零通量面处垂向湿润锋运移加快.以此为基础,建立了包含湿周在内的沟灌累积入渗量计算模型. 相似文献
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A new tribe of Diamesinae, Eugenodiamesini tr. nov. (Diptera: Chironomidae), is described based on a single pupa from Khutel Khara (lower part of the Tsagan Tsab Formation, Lower Cretaceous of Mongolia). The most distinctive characters of the new taxon are numerous multibranched lateral setae on tubercles along entire margins of abdominal segments II–VIII, and a unique setation of the anal lobes, with two multibranched anal macrosetae on each side and one simple near the apex. The fossil is the oldest known member of Diamesinae. 相似文献
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本文记述的晚石炭世早期菊石群采自宁夏中卫校育川、下河沿的靖远组.所采菊石经鉴定计有14属,24个种,其中包括2个新属,14个新种.本文对这些化石进行了描述,其中就属而言,以Reticu-loceras,Bilinguites,Gastrioceras,Cancelloceras最为丰富,它们分属本区的Reticuloceras带和Gastrioceras带的Cancelloceras bisati-Gastrioceras wongi 亚带.此二带分别与广西七圩的Retites catinatus带和Branneroceras branneri带相当,与西欧的R带和G1亚带亦可比较. 相似文献
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《International Geology Review》2012,54(8):1108-1113
Three new genera and four species of trilobites are described which include Tchaispis sdzuyi Atopina antiqua, Ivshiniellus nikolaii, and I. patulus. On the basis of their lack of eyes, configuration of cranidium, outline and segmentation of the glabella, very wide fixed cheeks and character of the anterior border they are assigned to the family Conocoryphidae Angelin, 1854. Tchaispis is known from the Middle Cambrian Olenek horizon of the Siberian Platform. Atopina and Ivshiniellus are known from the Lower Cambrian, Aldanian Stage of Tuva. --R. A. Robison. 相似文献
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A pygidium of Brachymetopus ornatus Woodward shows an abnormally developed left side affecting the whole of the pleural area and its rib development. Such an extensive abnormality, which does not extend beyond the axial furrow and shows none of the signs of resulting from injury, is currently unique. It is interpreted as a teratological condition in which a genetic or developmental malfunction resulted in the partial mimicking of thoracic pleurae rather than the construction of the normal pygidial pleural ribs. The effects of this are progressively greater from the posterior to the anterior parts of the affected pleural region. © 1996 John Wiley & Sons, Ltd. 相似文献
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描述了产于黔东南剑河县中寒武统凯里组中上部的19块中寒武统底部标志化石--印度掘头虫Oryctocephalus indicus(Reed,1910)蜕壳标本,其中大部分缺失头盖,其余外壳保存完好.对其蜕壳过程进行了探讨,认为蜕壳程序如下:头甲以小于90°角下弯,导致背壳沿头、胸接合处裂开;面线张开,自由颊与头盖裂开;虫体恢复平伸状态,头盖旋转;三叶虫携老壳向前爬行,并将已与自由颊和胸甲裂开的头盖顶翻于头甲前方;虫体继续向前爬行,并将头盖扒向两侧;虫体向前爬行并不断颤动,最终脱掉老壳.被脱掉的老壳胸尾相连,腹边缘-唇瓣板与自由颊基本位于原位,与"Phacopid式蜕壳"或"Salter式埋藏"明显不同. 相似文献