介形虫壳元素成分的初步测试

用能谱仪初步测试了46个介形虫样品的元素成分,结果表明现代介形虫壳的元素成分变化小,Ca为其主要成分(含Ca94.12—99.8％),Si、Al含量很低。新生代介形虫壳的成分和现代介形虫壳的成分相似.中生代和古生代的介形虫壳含Ca量减少,Si、Al含量增高,还含微量的K、Mn、Fe、S、Mg等元素.介形虫壳成分的变化,推测与地质时期中介形虫的埋藏条件和石化程度等有关.     

长江三角洲第四纪海相介形虫的古环境意义

本文根据长江三角洲地区7个钻孔的介形虫化石群古生态的研究成果,并参考有关资料,讨论了该区第四纪海相介形虫的时、空分布及其古环境。文中指出,海相介形虫的分布与该区第四纪海侵层有关,它在距今约0.30Ma形成的海侵层中富集,上述结论与对中国东部沿海平原海平面研究所取得的认识(第四纪高海面仅在0.30Ma以来才表现明显)相一致。该区介形虫化石群的成分较渤海西岸稍多,可能与该地区易受外海影响有关;而它又比广东、福建、香港的化石群简单,这可能是气候、水温差异的表现。     

安徽五河、河北南皮Propontocypris的发现——兼论2kaB.P.的突然变化事件

继在微山湖西江苏丰县、沛县及安徽萧县上更新亚统见广盐海相介形虫以来，首次在皖苏交界的安徽省五河县２ｋａＢ．Ｐ．以来的河漫滩相粘土层中见广盐海相介形虫ＰｒｏｐｏｎｔｏｃｙｐｒｉｓｅａｒｙｈａｌｉｎａＺｈａｏ，在河北省南皮县２ｋａＢ．Ｐ．西汉遗址文化层中亦见此种。在不能排除鸟类、风暴潮搬运海相介形虫卵的可能时，本文亦考虑其产出层位水化学状况应有较大变化。文内总结了目前对渤海湾两岸２ｋａＢ．Ｐ．“海侵”的研究状况，提出低洼滨海平原当时有地下水位上升或风暴潮加剧的可能，基本确认当时发生过突然变化事件，但不足以称     

松辽盆地上白垩统青山口组介形虫群集性死亡事件成因

松辽盆地上白垩统青山口组发育含大量介形虫化石的介形虫层,介形虫层的单层厚约5～200cm。介形虫层具有低伽马、高电阻、低声波等测井响应特征。以测井资料识别介形虫层为基础,研究了介形虫层在平面上不同相带及其在纵向高频层序格架下的分布规律,探讨了介形虫群集性死亡的原因。介形虫层平面上主要分布在大庆、龙虎泡—红岗阶地、黑帝庙等环坳带,盆地东部相对不太发育,滨浅湖是介形虫生存的有利环境;纵向上主要分布在青一段上部及青二段。高频层序旋回控制了介形虫的繁殖与死亡,介形虫群集性死亡事件主要发生在基准面下降期间。介形虫的群集性死亡与湖泊面积扩大无关,更与海侵事件无关。基准面下降造成水体变浅、矿化度增高以及砂岩进入滨浅湖可能是导致介形虫群集性死亡的直接原因。     

贵州晚二叠世—早三叠世介形虫动物群的演变

贵州有许多二叠系至三叠系的连续剖面，沉积类型多样，生物化石丰富，其中介形虫化石不但类型多，数量也很丰富，保存完好，发展阶段明显。即长兴阶介形虫类型多，数量也多，壳饰复杂，以具瘤刺的为多，早三叠世早期介形虫贫乏，数量及类型都不多，壳饰以光滑或具微细纹饰的为主。根据这些介形虫类型和数量的变化，以及壳饰特征的研究，表明二叠系与三叠系界线附近的介形虫动物群也同其它生物一样发生了重要变化。为二叠－三叠系界线     

沂沭河中下游地区第四纪海相地层的确定

根据笔者在沂沭河中下游地区（临沂—宿迁一带）第四纪地层中所发现的有孔虫、海相介形虫组合及室内外所获其他有关资料,初步确定了区内第四系的海相层及其时代归属。     

地层概况

本区地层区划属于塔里木区莎车分区的喀什和英吉莎两个小区。区内中新生代地层随断陷盆地呈条带状分布,不整合于古生代地层之上,在天山前缘由北向南从老到新依次出露,而昆仑山前缘则与之相反,岩层北倾。本区上白垩统和下第三系为正常海相及滨海泻湖相沉积。含有以海相双壳类、介形虫及有孔虫为主的动物群及孢粉、藻类等化石。上第三系虽以陆相碎屑沉积为主,但下部仍有海陆过渡相的沉积,含有广盐度有孔虫和介形虫化石。上白垩统到第三系总厚4000—9000米,现从老到新将各组地层介绍如下:     

北戴河潮间带现代介形虫的分布

由北戴河潮间带的12个样品分析得到介形虫29属46种。由于具体的小生境,缺少淡水介形虫, 北戴河潮间带底栖动物丰富,介形虫组合的主要特征与胶州湾东北角小海湾及东、黄海潮间带和潮下带介形虫的组合相似。在风化、潮汐和波浪等作用下,潮间带介形虫的壳体表面受机械磨蚀和破坏保存不好,充分反映出其异地埋藏特点。 通过研究北戴河潮间带介形虫,为研究我国辽阔沿海地区潮间带和潮下带介形虫的组合特征、分布范围及地理分区提供了很有价值的资料,并对海洋地质学、古生态学及沉积相等的研究具有重要意义。     

中国东部早第三纪沉积环境探讨

<正> 近年来讨论我国东部早第三纪沉积环境的文章甚多,归纳起来有以下三种观点:(1)我国东部早第三纪许多沉积盆地中发现有孔虫、介形虫、多毛纲龙介类栖管、鱼类、藻类等海相或半咸水动植物群;指相矿物则有海绿石、胶磷石等;微量元素B、Ga 含量和比值及Sr、Ba 含量和比值等都接近于海相,高于陆相,于是产生了“海侵”观点。(2)基于上述海相或半咸水动植物群又常常与淡水动植物群共生,而且淡水动植物群含量又高于海相或半咸水动植物群的情况下,加之微量元素含量、比值均低于海相、高于陆相的特征,于是产生了海陆过渡相观点。     

废黄河三角洲典型钻孔XJ01全新世地层与微体古生物记录

钻孔XJ01位于废黄河三角洲滨淮镇附近,钻孔中上更新统顶部与全新统有4个14C测年数据控制,该孔全新统岩性特征自下而上为潮间带含贝壳砾质砂层、浅海相淤泥质黏土层、三角洲前缘相深灰色粉砂、三角洲平原相黏土质粉砂及粉砂质黏土。全新统微体古生物分析结果详细地反映了废黄河三角洲典型区域各时期的沉积环境,其中,全新统下部见大量的有孔虫与海相介形虫,中部微体古生物略少,上部地层中海相介形虫增多。整个全新世微体生物组合揭示了一个河口变化的水动力控制沉积环境。     

中全新世福建沿海地区海平面波动：基于NDQK5岩芯介形类化石记录

福建沿海地区第四系较为发育,是研究晚更新世以来相对海平面变化的理想区域。本文以福建宁德NDQK5岩芯中产出的高分辨率介形类化石为研究对象,结合加速器质谱法(accelerator mass spectrometry, AMS)14C和光释光测年技术建立岩芯年代框架,重建了中全新世期间福建沿海地区的相对海平面变化。结果显示,NDQK5岩芯中的介形类化石记录主要分布于4~17. 1 m段,对应年代约为8. 2~6. 9 ka BP。岩芯内共计识别出海相介形类23属26种,根据优势种以及特征种的相对丰度变化特征可将岩芯内的介形类动物群划分为3个组合：① 介形类组合A以Bicornucythere bisanensis和Sinocytheridea impressa为主,代表潮下带环境;② 介形类组合B以Sinocytheridea impressa和Neomonoceratina delicata为优势种,指示近岸内陆架的沉积环境;③ 介形类组合C以Sinocytheridea impressa和Loxoconcha ocellifera为主,代表潮间带的沉积环境。基于介形类组合的分布特征,本文推断福建沿海地区海平面约在8. 2~7. 4 ka BP期间持续上升,并在约7. 9~7. 4 ka BP区间达到最高;7. 4~7. 0 ka BP期间海平面下降,随后再次上升。因此,介形类化石记录指示福建沿海地区在全新世高海平面背景下依然存在相对海平面的次一级波动。同时,结合已有福建沿海地区海平面变化驱动机制的研究结果,本研究推断8. 2~7 ka BP期间福建沿海地区的海平面变化可能主要受控于冰盖融水;7 ka BP后该地区的海平面波动可能受控于“冰川- 水均衡调整”作用。     

Middle Miocene ostracods from Wadi Sudr,westcentral Sinai,Egypt: systematic,biostratigraphy and palaeobiogeographic affinity with the Mediterranean realm

The investigation of the exposed middle Miocene strata from Wadi Sudr yielded well-preserved ostracod carapaces. Detailed taxonomic and paleontological studies led to the recognition of 36 ostracod species belonging to 25 genera, 4 species of them were considered new which fully described. Three assemblage biozones were recorded as follows: Actinocythereis spinosa–Actinocythereis hystrix zone, Chrysocythere cataphracta muricata-Cytheretta africana zone, and Disopontocypris schweijeri-Bythocypris tripolensis zone. The recorded biozones were calibrated with the previously studied middle Miocene planktonic foraminiferal biozones on the same samples and also correlated with the Miocene ostracod biozones from the neighboring countries. Our ostracod assemblages present in the lower and upper parts of the studied section (section II) indicated an inner neritic marine environment of moderate energy of currents and rapid sedimentation, while the assemblages in the middle part showed more deeper (outer neritic) environments with low energy of currents and low rate of sedimentation. The palaeobiogeographic distribution of the studied ostracods showed high affinity with the ostracod assemblages of the southern Mediterranean and moderate to low affinities with that of the northern and eastern Mediterranean respectively. The highly ornamented ostracod species with structures on the carapace were recorded from both Northern and Southern Mediterranean, while the smooth ones were found in the Southern Mediterranean only. The highly ornamented species are more widely distributed in both Southern and Northern Mediterranean than the smooth species. This may indicate that the ornamented species are more able to migrate than the smooth ones.     

A microfaunal and sedimentary record of environmental change within the late Holocene sediments of Boca do Rio (Algarve,Portugal)

The foraminifera and ostracods observed in a late Holocene sedimentary sequence within a fluvial valley at Boca do Rio in the coastal zone of the western Algarve, Portugal, reveal a general, though not smooth transition from marine to fluvial conditions. The relative influence of these two environments appears to depend on the degree of permeability of the barrier system at the coast. Optically stimulated luminescence dates and palaeoecological information obtained from the sequence suggest that barrier formation may be related to changes in climate and/or patterns of ocean current circulation. An unusual deposit rich in sand and gravel found within the otherwise mud-dominated sequence has been dated at AD 1801 ± 76 years. This deposit contains foraminifera and ostracods which indicate marine conditions, and which contrast markedly with the brackish-water, estuarine assemblages found in the mud deposits. The rapid transition in the foraminifera and ostracod assemblages indicates a short-lived coastal flooding, which may represent the tsunami associated with the Lisbon earthquake of AD 1755. The variations in the foraminifera and ostracod assemblages also suggest subsidence during the earthquake, with uplift having occurred in the period since then.     

南岭地区上三叠统-下侏罗统双壳类生物地层及三叠-侏罗系界线

南岭地区在晚三叠世-早侏罗世沉积了一套海陆交互相含煤地层,其中双壳类化石十分丰富,对其详细的生物地层 学研究可以为这套地层的划分和对比、识别该区侏罗系与三叠系界线提供重要的古生物资料。本文对湖南浏阳石康、湖南 宜章下坪和广东揭西灰寨三条剖面采集的海相和非海相双壳类化石进行了系统研究。结果显示研究区上三叠统-下侏罗统 具有4个双壳类生物带,即：半咸水相Unionites? emeiensis 顶峰带、海相Retroceramus subinconditus-Hiatella 组合带、海相 Ryderia guangdongensis-Parainoceramus jinjiensis组合带和半咸水相-陆相Kija ovata-Waagenoperna mytiloides组合带。对各生物 带代表化石在区域上的时代延限分析表明,Unionites ?emeiensis 顶峰带时代延限主要为瑞替期, Retroceramus subinconditus-Hiatella 组合带主要为赫塘期,Ryderia guangdongensis-Parainoceramus jinjiensis 组合带主要为辛涅缪尔期,但有 可能向上延伸至土阿辛期。经与海相同类生物带的对比,Kija ovata-Waagenoperna mytiloides 组合带时代延限大致为赫塘期 至土阿辛期。根据综合对比分析认为南岭地区半咸水相-陆相T-J 界线应位于Unionites? emeiensis 顶峰带与Kija ovata-Waagenoperna mytiloides 组合带之间,这与四川盆地陆相T-J界线（位于Modiolus weiyuanensis-Unionites? emeiensis 组合 带与Pseudocardinia （=Kija） kweichouensis-Cuneopsis sichuanensis 组合带之间） 和新疆准噶尔盆地陆相T-J 界线（位于 Waagenoperna-Yananoconcha（=Kija）组合带与下伏郝家沟组之间） 大致相当。     

Ostracods (Crustacea) and their palaeoenvironmental implication for the Solimões Formation (Late Miocene; Western Amazonia/Brazil)

Western Amazonia's landscape and biota were shaped by an enormous wetland during the Miocene epoch. Among the most discussed topics of this ecosystem range the question on the transitory influx of marine waters. Inter alia the occurrence of typically brackish water associated ostracods is repeatedly consulted to infer elevated salinities or even marine ingressions. The taxonomical investigation of ostracod faunas derived from the upper part of the Solimões Formation (Eirunepé; W-Brazil) documents a moderately diverse assemblage (19 species). A wealth of freshwater ostracods (mainly Cytheridella, Penthesilenula) was found co-occurring with taxa (chiefly Cyprideis) usually related to marginal marine settings today. The observed faunal compositions as well as constantly very light δ¹⁸O- and δ¹³C-values obtained by measuring both, the freshwater and brackish water ostracod group, refer to entirely freshwater conditions. These results corroborate with previous sedimentological and palaeontological observations, which proposed a fluvial depositional system for this part of western Amazonia during the Late Miocene. We demonstrate that some endemic, “brackish” water ostracods (i.e., Cyprideis) have been effectively adapted to freshwater conditions. Thus, their occurrence is no univocal evidence for the influence of brackish or marine waters in western Amazonia during the Miocene.     

Ostracods and palaeobotany from the middle Permian of Oman: implications on Pangaea reconstruction

Discovery of a middle Permian ostracod fauna in the marine Khuff Formation (Sultanate of Oman), combined with palaeobotanical data from the immediately underlying continental Gharif Formation, supports new interpretations of the palaeobiogeography of the Tethys during the late Palaeozoic. A mixed ostracod fauna existed on the Arabian platform. This new record of Permian ostracods, combined with recent data obtained in other Tethyan areas, emphasizes the close relationship between the south-western Tethys realm and South China. The macro- and microfloral assemblages of the continental Gharif Formation demonstrate that this palaeoflora represents a true mixed association in which Gondwanan, Cathaysian and Euramerian elements are intermingled. Two main models exist for the reconstruction of Pangaea during the late Palaeozoic. Both ostracods and palaeobotanical evidence favour the reduction of the oceanic area between South China and Arabian plate as in the B Pangaea model favoured by recent palaeomagnetic data.     

A Mutual Temperature Range method for Quaternary palaeoclimatic analysis using European nonmarine Ostracoda

A new Mutual Temperature Range method for estimating past air temperatures is presented, based on European Quaternary nonmarine Ostracoda and using the Nonmarine Ostracod Distribution in Europe (NODE) database and a modern climate dataset in conjunction with DIVA-GIS software. The value of nonmarine ostracods in Quaternary palaeoclimate reconstruction has long been recognised, mainly in terms of the use of indicator species and, more recently, analyses of the trace element and stable isotope chemistry of their calcareous valves. The new Mutual Ostracod Temperature Range (MOTR) method uses a nonanalogue approach based on the presence/absence of species in a fossil assemblage; preliminary testing has yielded good matches with both modern temperatures (using living assemblages not already in NODE) and palaeotemperatures inferred by the Coleopteran Mutual Climate Range method, but further testing and refinement are needed. Assumptions about the climatic tolerances of living and fossil ostracod species, as well as complicating factors (such as the relationship between water temperature and air temperature, habitat preferences and taxonomic errors) require careful examination; nevertheless, the MOTR method shows considerable promise and is a valuable addition to the Quaternary palaeoclimatologist's toolbox.     

Late Weichselian ostracod assemblages from the southern Kattegat, Scandinavia: a palaeoenvironmental study

The ostracods in three vibro cores (representing the time between c . 13000 and 12000 BP) from southern Kattegat were studied to further elucidate palaeoenvironmental conditjons in an area interpreted to be influenced by a Late Weichselian drainage of the Baltic Ice Lake via the Öresund Strait. This time represents an extremely important phase of the deglaciation of the northern hemisphere. It is characterized by rapid climatic change and enormous amounts of meltwater that are drained into the ocean. The ostracod assemblages identified are characterized by a peculiar mixture of marine (arctic and temperate) and freshwater species believed to characterize environments ranging from the tidal zone of an outer estuary (or delta) to fully marine sublittoral conditions in a subarctic climate. Dominant species display autochthonous population structures typical of in situ elements of such environments. Indications of very shallow conditions are, however, difficult to reconcile with palaeobathymetrical inferences from earlier studies of shore-level displacements. It is, therefore, possible that the present assemblages are mainly death assemblages deposited offshore by postmortem meltwater discharge. Rare pre-Quaternary ostracods similar to Mesozoic species previously reported from the Öresund Strait (drill holes) and the Swedish west coast may have been redeposited by outflowing meltwater.