东营凹陷沙河街组介形虫化石保存特征研究及应用

本文对山东东营凹陷沙河街组介形虫化石壳体的保存特征进行了研究。研究结果表明：沙河街组介形虫化石壳体颜色可分为浅色、中色和深色三种类型;按有无充填物,可分为未充填壳和充填壳两种,其中充填壳充填物的成分有方解石、白云石、黄铁矿和泥质四种;按完整程度有双瓣壳、单瓣壳和碎壳。文中对这些保存特征形成的原因进行了讨论,最后以一口井的研究结果为例,探讨了介形虫保存特征在古湖泊学及石油地质方面的应用。     

松辽盆地D80井嫩一段介形类化石壳体特征及生物地层

松辽盆地嫩江组一段富含介形类化石,是系统研究Santonian期陆相介形类的理想层位。论文对中央坳陷区D80井嫩一段的介形类化石进行了系统的分类、生物地层和壳体特征分析。鉴定出介形类化石11属30种,划分出6个介形类化石带,并与前人的研究结果进行了对比;描述了该段介形类化石的壳体结构,共识别出4种壳饰类型,8种壳形结构,基于介形类壳体特征和其他证据,初步探讨了该时期湖盆湖平面的变化特征,显示出嫩一段时期松辽湖盆湖平面经历了由深逐渐变浅的过程。     

甘肃花海盆地早白垩世的介形类

详细研究了首次发现于甘肃花海盆地截大板沟下白垩统下沟组的介形类化石。根据它们的组合面貌及其在国内外分布的主要层位,认为原划归为上侏罗统,并含有丰富介形类和轮藻化石的这套地层应属下白垩统下统下沟组,其时代为早白垩世Ｂｒｒｅｍｉａｎ期。     

柴达木盆地北缘昆特依凹陷始新统下干柴沟组微体古生物研究

昆2井是柴达木盆地北部昆特依凹陷区潜伏Ⅰ号构造上的第一口勘探井,为了建立该地区地层层序,对该井的岩屑及岩芯样品进行了系统的微体古生物学研究,仅在下干柴沟组发现少量轮藻化石和零星的介形类化石。下干柴沟组下段出现的轮藻类Gyrogona qianjiangica和Lamprothamnium? brevis是我国中始新世最常见的化石。该层段的轮藻类可命名为Gyrogona qianjiangica-Lamprothamniumcurta-L. brevis组合,时代为中、晚始新世。本文以Gyrogona qianjiangica分布的顶、底界作为昆2井下干柴沟组下段的标志,划分结果与其它轮藻及介形类化石的对比结果基本一致。氯离子含量分布显示,轮藻类化石产出的下干柴沟组是整个地层剖面中含盐度最低的沉积阶段,表明下干柴沟组沉积时期,该地区处于水域比较广阔的淡水湖泊环境,但在个别层段出现咸化环境,产出以喜盐的Austrocypris为代表的介形类化石。     

鄂尔多斯盆地西缘中石炭世介形类

本文报道了鄂尔多斯盆地西缘,桌子山、贺兰山地区中石炭统羊虎沟组介形类化石10属27种(包括9新种、2未定属种)。化石保存较好,分带明显。自下而上划分了三个组合:Bairdia-Microcheilinella组合Ⅰ;2.Healdio-Bythocypris组合Ⅱ;3.Healdia-Paraparchites组合Ⅲ.化石除地方种外,可与美国南半部密苏里、俄克拉荷马、得克萨斯等诸州之石炭系中所见介形类大致可以对比。     

甘肃靖远下石炭统臭牛沟组介形类记述

本文描记甘肃靖远磁窑地区臭牛沟组的介形类化石,计21属32种(其中1新属、19新种、2未定种),并建立Microcheilinella-Prtjpbaordoa-Healdianella-Grobrpcpmcja介形类组合。根据组合特征及其与国内外对比,将臭牛沟组的时代定为早石炭世。     

甘肃玉门下沟地区早白垩世下沟组介形类

甘肃玉门下沟地区下沟组介形类化石十分丰富,该地区下沟组介形类化石共计9属4亚属,21种,本文描述了其中4新种,即Cypridea(Cyamocypris)xiagouensissp.nov.,Cypridea(Cypridea)subunicostatasp.nov.,Stenestroemiasubpeculiarissp.nov.和Stenestroemiaxiagouensissp.nov.。该介形类化石组合尤以Cypridea最为繁盛,通过分析介形类属种的形态特征和化石组合特征并结合岩性特征,推断下沟组的地质时代为早白垩世巴列姆期;并认为下沟组为水动力较弱的淡水-微咸水河湖相沉积。     

川南马边老河坝磷矿区麦地坪组中管状化石壳体成分特征及与围岩的关系

小壳化石壳体成分的鉴定对于揭露寒武纪早期小壳动物群的演化具有重要意义。本文通过岩石薄片观察,分析了川南马边老河坝磷矿区麦地坪组中不同岩性管状化石壳体成分特征。结果显示,不同围岩中管状化石壳体成分不同:围岩为磷块岩,管状化石中间层保存成分以胶磷矿为主,夹白云石晶体;围岩为白云岩,管状化石中间层保存成分以胶磷矿为主;而围岩为灰岩,管状化石的中间层保存成分以胶磷矿或方解石为主。后期磷酸盐化作用改造明显:壳体内部碳酸盐矿物被胶磷矿或微晶质石英交代、磷质壳内部被白云石或隐晶质燧石交代现象发育,其中以碳酸盐矿物被胶磷矿交代的现象居多;部分管状化石的壳体出现模糊的多圈层结构和壳体增厚的现象;壳体内部填充的胶磷矿在围岩中普遍出现。壳体保存成分与围岩性质密切相关,研究区内保存的管状化石壳体成分绝大部分经历了磷酸盐化作用。     

介形类的形态学及其环境、功能和分类学意义

化石介形类分类依据--壳体形态,包括壳体的大小、形状、装饰和诸如毛孔、叠覆、似犁状构造、喙、铰合构造等构造特征都与介形类的栖息环境,包括地理、气候(季节、纬度等)、水体的深度、化学性质和稳定程度,食物的富集程度和群落的组成及个体数量以及性别息息相关.因此,正确理解介形类的形态学特征及其功能学,不仅能揭示介形类的生活习性,推测化石介形类的生活环境,从而为古环境和古群落生态重建提供依据,而且可以提高化石介形类个体发育、系统分类和演化研究结果的可靠性.     

介形类系统分类与起源演化的形态、分子和化石证据

介形类(Ostracoda)因其丰富的化石记录和广布的海陆现生代表类群,而被认为是进化生物学中研究生物多样性产生机制和演变历程的颇具潜力的重要模式生物。介形类在甲壳亚门中的谱系发生位置、起源及其内部各类群间的系统关系还存在诸多争议。基于其体制构造的形态学特征,介形类被归入甲壳亚门下的颚足纲(Maxillopoda),但来自18S rDNA序列数据分析却显示Maxillopoda不是单系群。基于化石记录和壳体形态特征,高肌虫(Bradoriida)长期以来被认为是介形类的一个祖先类群,但保存有软躯体的早寒武世化石的研究表明,Bradoriida不是介形类甚至可能也不属于甲壳类。不同的研究者所强调的壳体和肢体形态特征各异,导致介形类最大的现生类群速足目(Podocopida)的四个超科之间的关系也存在诸多推测。壳体和肢体特征在系统演化意义上的不兼容,需要分子生物学等证据的介入。分子、形态和化石证据的积累及各种信息整合是系统演化研究的必然趋势。     

Turtle remains from the Middle Jurassic Xintiangou Formation of Yunyang,Sichuan Basin,China

Three turtle shells from the Middle Jurassic Xintiangou Formation of Yunyang (Chongqing, China) are described and assigned to Xinjiangchelyidae (Testudines: Eucryptodira). This is the first report of turtle remains from the Xintiangou Formation, Sichuan Basin and represents the oldest known Xinjiangchelyidae. The assemblage includes two taxa, Protoxinjiangchelys sp. and Xinjiangchelyidae indet. This discovery extends the stratigraphical distribution of Xinjiangchelyidae and improves our knowledge about the early evolution of that family. It demonstrates that by the Middle Jurassic, at the time of deposition of the Xintiangou Formation, the group was already diversified in the Sichuan Basin.     

A new giant cypridid ostracod (Crustacea) from southern Buenos Aires Province,Argentina

Amphicypris argentinensis sp. nov., is described and illustrated from Laguna Caliba, an ephemeral fresh water lake from the southern coast of Buenos Aires Province, Argentina. Specimens were raised from dried sediment recovered from a bank of ostracod shells found at the edges of the lake. Deposition of progressively smaller ostracod valves stacked one into another (cup-in-cup structure) is documented. The geographical distribution and ecology of the genus is briefly discussed.     

A new giant cypridid ostracod (Crustacea) from southern Buenos Aires Province, Argentina

Amphicypris argentinensis sp. nov., is described and illustrated from Laguna Caliba, an ephemeral fresh water lake from the southern coast of Buenos Aires Province, Argentina. Specimens were raised from dried sediment recovered from a bank of ostracod shells found at the edges of the lake. Deposition of progressively smaller ostracod valves stacked one into another (cup-in-cup structure) is documented. The geographical distribution and ecology of the genus is briefly discussed.     

Trace elemental distribution in ostracod valves. From solution ICPMS and laser ablation ICPMS to microprobe mapping: a tribute to Rick Forester

A historical perspective on our understanding of the formation of ostracod valves and what they consist of is presented here, together with the history of investigations on the chemistry of ostracod valves. It is now clear that ostracod valves are made of 3 distinct layers consisting of calcite crystallites/rhombs that are held together by a significant network of organic fibrils which may also contribute to the trace elemental composition of ostracod valves when analysed by solution chemistry. The outer epicuticle of ostracod valves, when well preserved such as in modern material, contributes to an enrichment in magnesium, and this ought to be taken into account when interpreting the Mg/Ca of ostracod valves for use with water temperature reconstructions. Recommendations about the analytical techniques used for chemical analysis of ostracod valves are presented.     

OSTRACODS AS MARKERS OF THE PERMIAN/TRIASSIC BOUNDARY IN THE KHUFF FORMATION OF SAUDI ARABIA

Abstract:  Ostracods are described for the first time from Permian–Triassic shallow marine sediments of the Khuff Formation of central Saudi Arabia. They were collected using a modified acetolysis technique for releasing calcareous shells from limestones that is described herein. Thirty-four species belonging to 17 genera are recognized. Two new species are described: Arqoviella arabica sp. nov. and A. khartamensis sp. nov. The ostracod fauna supports a Late Permian age for the lower Khartam Member and a probable Early Triassic age for the upper Khartam Member of the Khuff Formation of central Saudi Arabia. This suggests that the Permian/Triassic boundary is located within the Khartam Member, rather than at the major lithological break between the Midhnab and Khartam members. Palaeoecological analysis suggests that the palaeoenvironment of the Khuff Formation was shallow marine (between 1 and 50 m deep) on an internal shelf.     

Complex controls on ostracod palaeoecology in a shallow coastal brackish‐water lake: implications for palaeosalinity reconstruction

1. The low‐Mg calcite shells of Ostracoda (Crustacea) are often well preserved in the sediments of alkaline lakes. In coastal waters that have undergone large temporal changes in salinity, ostracod assemblages preserved in the sediment record have been used to reconstruct palaeosalinity, often assuming that salinity is the only significant control on the faunas. 2. We evaluate the performance of ostracods as palaeosalinity indicators in Hickling Broad, a shallow brackish coastal lake in Norfolk, U.K., by comparing fossil ostracod assemblages covering two centuries with geochemical inferences and instrumental records of past salinity and water composition along with other palaeolimnological indicators. 3. Despite large changes in the salinity of the lake and the supposed salinity sensitivity of ostracods, the fossil ostracod assemblages do not clearly reflect the salinity trends inferred from the other independent data. Rather, a complex series of changes has occurred in the lake over the past 200 years and factors other than salinity, including eutrophication, toxicity and associated complex alterations in habitat availability have probably influenced ostracod assemblages. In contrast, there is a good broad agreement between inferred or measured salinity and the trace‐element chemistry of ostracod shells. 4. We conclude that ostracod faunas may not always provide unambiguous palaeosalinity records and should therefore not be used to reconstruct salinity changes except as part of a multi‐proxy investigation that includes other palaeoecological and/or geochemical indicators.     

Late Glacial and Holocene Ostracoda of the Gulf of Gdańsk,the Baltic Sea,Poland

To trace environmental changes in water hydrology and salinity in the Late Glacial to Holocene of the Gulf of Gdańsk, a south‐eastern bay of the Baltic Sea within the maritime zone of Poland, the distribution of ostracod valves was studied in 20 sediment cores collected from both the shallow‐ and deep‐water zones (depth 10.9–67.5 m). The studied sediment sequences yielded ca. 3000 valves of 21 ostracod species, of which only five are known to live today in the Gulf, which has a present maximum depth of 118 m and water salinity up to 7–8‰. The majority of the studied sediment layers that contained ostracod valves corresponded to the period of the Late Glacial to Mid‐Holocene and was dominated by non‐marine species, of which the most common were Candona neglecta (present in 17 cores), Cytherissa lacustris (15 cores) and Candona candida (14 cores). By clustering classification five major ostracod assemblage types were recognised in the studied cores. Initial assemblage types dominated mostly by inhabitants of the profundal/sub‐littoral zones of modern oligo‐mesotrophic lakes (C. lacustris and C. neglecta) in some sediment sequences were replaced in stratigraphical order by the assemblages dominated by brackish‐water species (Cyprideis torosa or Cytheromorpha fuscata). The structure and species composition of the distinguished ostracod assemblage types as well as their successional transitions indicate that the studied sediments were deposited initially in the Late Glacial in freshwater lacustrine conditions, and subsequently, during the Holocene marine transgression, covered by marine sands. The present results confirm and consolidate inferences based on previously published data on ostracods from the western part of the Gulf of Gdańsk as well as on other biotic (molluscs, diatoms) and abiotic (seismoacoustic) indices from this area (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

西藏聂拉木晚奥陶世的介形类

文中首次报道西藏聂拉木地区亚来水厂剖面上奥陶统甲曲组介形类16属30种,介形类以古足介目类和圆足介目类为主,少量速足介目类。根据该剖面介形类时代特征,可以推断甲曲组应属于晚奥陶世早期,大致为Sandbian期—Katian期。该介形类生态组合为艾菲尔生态型,指示甲曲组在沉积时为近岸浅水环境。晚奥陶世喜马拉雅地层区与华南扬子区及塔里木介形类面貌相似,应属于相同的生物地理分区。     

柴达木盆地西部红柳泉地区晚侏罗世介形类动物群及其古环境意义

在柴达木盆地红柳泉地区红探2井红水沟组中识别出介形类化石3属9种(含2个未定种):Cetacella qaidamensis Li et Yang, 1983、Djungarica tracta Li et Yang, 1983、Djungarica sp.、Alicenula incurva (Bate, 1967)、?A.longicylindrica (Qi, 1985)、A. paramagna (Li et Yang, 1983)、A. maanshanensis (Hou et al., 2002)、A. jinhuaensis (Li,1984)、Alicenula sp.。通过介形类化石生物地层对比,明确红水沟组的沉积时代为晚侏罗世。红水沟组介形类动物群指示晚侏罗世柴达木地区发育淡水湖泊、河流以及季节性的小水塘。     

Buried ostracods collected at the location of a nuclear submarine accident in the Chazhma Cove (Peter the Great Bay,Sea of Japan)

In a sample of benthos collected at the location of a nuclear submarine accident in Chazhma Cove (Peter the Great Bay, Sea of Japan), we found remains (valves and shells) of 37 ostracod species, along with living pollution-tolerant organisms. The death of ostracods may be due to the consequences of the nuclear accident, but most likely was caused by domestic and technogenic pollution of the bay by oil products, which are particularly harmful to ostracods. The data provide a vivid example of detrimental anthropogenic impact on the fauna of ostracods, suggesting their increased sensitivity to adverse environmental factors, compared to many other marine organisms.