塔里木板块塔中区上奥陶统良里塔格组的生物礁类型

塔里木板块塔中Ⅰ号坡折带附近上奥陶统良里塔格组取芯井段中可识别多种生物礁灰岩类型,包括珊瑚骨架/障积岩、海绵骨架/绑结岩、苔藓虫绑结岩、钙藻障积岩、钙质菌藻障积/绑结岩等礁灰岩类,藉此可归纳出珊瑚礁、珊瑚-钙藻礁、层孔虫礁、层孔虫-钙藻礁、珊瑚-层孔虫-钙藻礁、苔藓虫礁丘、钙藻礁丘、灰泥丘和微生物礁等生物建造单元。这些礁体的时空分布模式与古环境分异相关联,纵向上具有灰泥丘向珊瑚-层孔虫-钙藻礁至苔藓虫礁丘和钙藻礁的群落结构更替趋势;空间分布则向台地北缘,即I号坡折带延伸显示由低能带灰泥丘向高能带珊瑚-层孔虫-钙藻礁的相变,而且高能带珊瑚-层孔虫-钙藻主体礁和环其周缘相对低能带的钙藻礁丘、灰泥丘等在一定范围内构成造礁群落结构分异。     

塔里木塔中油田上奥陶统良里塔格组滩相

塔里木板块塔中井区上奥陶统凯迪阶良里塔格组的沉积序列由碳酸盐岩台地区礁滩复合体灰岩构成,显示晚奥陶世由高生物多样性形成的暖水浅海域生态组合。根据滩相灰岩的颗粒组成,可次分为生屑为主、生屑-内碎屑混合、内碎屑为主的三大类型,其中灰泥充填和亮晶方解石胶结均有。部分滩相是礁相单元的近源沉积,而内碎屑和生屑经各种营力改造后多以不同比例混合独立形成滩相。滩中的颗粒粒径一般多小于厘米级,仅部分核形石、珊瑚等颗粒可达到砾级,这些滩多堆积于最大风暴浪基面之上的深度。     

新疆塔里木塔中井区上奥陶统良里塔格组的生物绑结岩

塔里木板块塔中井区上奥陶统凯迪阶良里塔格组灰岩中底栖固着型的钙质微生物、钙藻以及动物苔藓虫、珊瑚、层孔虫,可通过障积、盖覆和粘结等方式形成多种类型的生物绑结岩。对15口井部分岩芯以常用的绑结岩分类方案作岩石学微相分析,并描记底栖固着型生物颗粒的形成特征。菌藻类可在内碎屑表面以包结方式形成粘结岩;钙藻,特别是分枝状钙藻可形成障积岩;层孔虫可被隐藻层纹包结,也可单独形成小型盖覆岩;床板珊瑚格架岩可大量障积生屑和灰泥基质;苔藓虫在动物格架岩比例上占优,可与菌藻类粘结岩互相包结生长,也可独立形成局部小型障积岩。对比巴楚露头区同期藻丘中的绑结岩特征,显示塔中良里塔格组代表晚奥陶世由高生物多样性形成的礁滩复合体生态群落。     

塔里木板块塔中上奥陶统良里塔格组的核形石

核形石包壳特征是分类的重要依据,包壳形态在一定程度取决于其生长环境中的水流能量因素.塔中油田3口井上奥陶统凯迪阶良里塔格组礁滩相所显示的生态指标具有差异性,其中核形石形态学与其产出层位沉积时的能量条件具有很大程度的协同.全包裹型圆形或椭圆形核形石多见于颗粒厌岩和泥粒状灰岩,代表中-高能沉积环境;正常核形石在高能环境出现频率较大;薄皮型核形石多为中等能量的产物;半包裹型核形石多见于灰泥基质的粒泥状灰岩-泥粒状灰岩,指示水流能量偏低的环境,复合型核形石具备半包裹型和全包裹型核形石特征,代表水动力条件相对较强、中高等能量相互交替的环境.     

新疆塔里木盆地中部岩心上奥陶统良里塔格组中的变口目苔虫

本文描述了新疆塔里木盆地塔中地区岩心中的上奥陶统良里塔格组的变口目苔虫3科12属16种,包括8个未定种,分别为Prasopora grayae Nicholson et Etheridge,Atactoporella declivis (Hu),Peronopora sp.,Mesotrypa angularis Ul...     

新疆塔里木中央隆起区中2井上奥陶统良里塔格组礁滩沉积相和测井参数

塔里木中央隆起区中2井位于塔中南坡台缘带,上奥陶统凯迪阶良里塔格组频繁出现浅水粒屑滩沉积,以及由蓝藻、钙藻兼以少量珊瑚、苔藓虫等造礁生物以不等含量分别构成生物障积或粘结型礁灰岩,棘皮类、腕足类和三叶虫等壳相生物碎屑丰富。可分出数层典型的生物礁、滩组合序列,总体显示为原地生长和近源搬运的生物礁滩复合体建造。环境的动能条件略有变化,但皆属浪基面之上的沉积深度。礁、滩储层形成模式主要受于沉积相带、成岩改造的控制,储层以生屑灰岩、藻粘结灰岩、障积灰岩及砂屑灰岩为主,储集空间类型包括次生溶蚀孔隙、晶洞与裂缝,同时伴随少量的白云岩化作用,且孔隙以深埋藏溶蚀成因为主,次生胶结作用也十分强烈,礁相储层潜力好于滩相。     

塔中隆起上奥陶统凯迪阶良里塔格组生物群及其古生态特征

塔中隆起区的良里塔格组含菌藻类微生物岩、植物类的钙藻、原生动物中的有孔虫、后生动物中的海绵、珊瑚、苔藓虫、介形类、三叶虫、腹足类、腕足动物、棘皮动物等化石门类。根据其生物成分的埋葬学特征,分为原地或近源成分占优势的群落和远源异地成分占优势的组合,群落和组合的类型展布受水深、水动力、坡折带地貌等因素控制。     

中国新疆塔里木盆地上奥陶统良里塔格组的钙藻化石

钙藻是可以发生生物钙化作用形成钙质"骨骼"的分属多个门类的藻类的俗称。钙藻最早出现于寒武纪,奥陶纪发生第一次辐射演化。本文系统讨论了绿藻门绒枝藻目(Dasycladales)、羽藻目钙扇藻科(Udoteaceae)的科和属级分类标准和红藻门珊瑚藻科、管孔藻科(Solenoporaceae)属级分类标准及其中各属分类中存在的问题。塔里木盆地晚奥陶世在塔中—巴楚台地和塔北台地发育了一套礁滩相良里塔格组碳酸盐岩,其中含有丰富的钙藻化石。本文系统描述了来自塔里木盆地塔中、巴楚、塔北地区取心井上奥陶统良里塔格组岩层中的钙藻化石11个属15个种。包括绿藻门绒枝藻目西莱特藻科(Seletonellaceae)的Dasyporella,Kazakhstanelia,Vermiporella,Aphroporella,Arthroporella,绿藻门的羽藻目Bryopsidales(siphonales)的钙扇藻科的Dimor phosiphon,Palaeo porella,红藻门珊瑚藻目(Corallinales)的管孔藻科的Solenopora,Parachaetetes及Corallinales incertus familiae的Petro-phyton,以及分类位置不明的Monili porella。其中绒枝藻Ajakmalajsoria被视作Kazakhstanelia的同义名。     

新疆塔里木盆地中部和北部台地上奥陶统良里塔格组岩心中的泡孔目、隐口目和窗孔目苔虫

新疆塔里木盆地奥陶系良里塔格组礁滩相非常发育,部分地区泡孔目、隐口目和窗孔目苔虫化石非常丰富,本文首次系统描述了塔里木盆地巴楚-塔中和塔北碳酸盐台地部分取心井上奥陶统良里塔格组的泡孔目、隐口目和窗孔目苔虫7科11属13种,包括1个新种和6个未定种,分别为Lunaferamita nevadensis Utgaard,L. vesicu-larissp.nov.,L.sp.,Graptodictya meneghinii(Vinassa de Regny),Chazydictya sp.,Rhinidictya nicholsoni Ulrich,Metadictyacf.crassa(Hall),Trigonodictya acuta(Hall),Stictoporella sp.,Chasmatopora spatiosa Ariun-chimeg,Ralfinellasp.,Moyerella sp.,Moorephylloporina sp.。其中,隐口目细枝状的Rhinidictya和网状的Chasmatopora,Moorephylloporina在塔中和巴楚地区横向及纵向地层中分布非常广泛。     

皖北地区寒武系芙蓉统炒米店组中上部的索克虫类三叶虫*

塔里木盆地塔中台地奥陶系海百合茎化石丰富。本文通过研究塔中35井上奥陶统良里塔格组和桑塔木组岩芯中的海百合与其共生生物的关系, 讨论了海百合化石的古生态。在塔中35井上奥陶统取芯中识别出7种海百合茎类型: 圆圆茎、星星茎、星圆茎、椭圆圆茎、星椭圆茎、圆角星星茎和不规则星茎, 根据茎板形态划分为五射茎板组(Pentameri)、椭圆茎板组(Elliptici)、圆茎板组(Cyclici)、特殊茎板组(Varii)四种组合类型; 统计了海百合茎化石各种切面的大小和百分含量; 结合岩性分析了每段地层的沉积环境。研究发现, 在局限泻湖环境下, 蓝细菌–四分珊瑚为主的生物组合中不见海百合化石碎片; 仅见腹足类和介壳类化石的细砂屑滩中, 偶见细小的海百合茎化石; 在开阔海环境中, 海百合广泛与苔藓虫、管孔藻、粗枝藻等共生。在海百合–苔藓虫组合中, 海百合茎板的类型最丰富多样, 五射茎板组、椭圆茎板组、圆茎板组、特殊茎板组等四种茎板组合类型都存在; 在管孔藻–海百合组合中, 海百合茎板主要为圆茎板类型, 粗大、密集, 海百合茎碎片含量最高; 在海百合–粗枝藻组合中, 海百合茎板的数量减少、大小变小, 但茎板的类型比较丰富, 四种茎板组合类型都有。由此认为, 塔中台地上奥陶统沉积期, 海百合生长的首选环境为开阔台地, 并受水动力能量和水体清洁度控制: 水动力能量高, 水体清洁, 海百合繁盛; 水动力能量低, 水体动荡浑浊, 海百合可以生存; 水动力能量低、较为动荡、微生物席发育的环境, 不利于海百合生存。     

塔里木盆地塔中台地上奥陶统海百合茎化石及其古生态*

聂拉木是西藏南部志留纪含笔石地层(石器坡组)的主要产地。近期在该地亚来村新发现一批笔石标本, 包括Normalograptus sp.、Glyptograptus sp.、Campograptus lobiferus、C. cf. lobiferus、C. cf. obtusus、C.? circularis、Lituigraptus cf. convolutus、Rastrites cf. perfectus、Stimulograptus sedgwickii、Streptograptus sp.和Torquigraptus decipiens。该组合面貌确定其属于志留系兰多维列统埃隆阶上部Lituigraptus convolutus带至Stimulograptus sedgwickii带。这一新材料的发现, 使西藏南部的志留纪地层得以作全球对比。     

新疆准噶尔盆地周边晚石炭世的珊瑚*

新疆北部准噶尔盆地周边石炭系广泛出露, 其中上石炭统发育海相火山—沉积序列, 包括西准噶尔地区的哈拉阿拉特组、阿腊德依克赛组, 东准噶尔地区的石钱滩组以及盆地南部的祁家沟组、奥尔吐组等。本文研究在上述各地层的灰岩层或夹层、碎屑岩中获得的四射珊瑚9属17种和床板珊瑚2属3种, 对石钱滩组中的3个新种进行了详细的系统古生物学描述。上述珊瑚化石的地质时代主要为巴什基尔期至莫斯科期。在珊瑚动物群的组成上, 哈拉阿拉特组中新发现Caninophyllum属分子, 结合盆地东、西部共同产出的床板珊瑚Cystodendropora 属分子, 说明整个准噶尔盆地周边的动物群面貌大致类似, 而西准噶尔地区的化石丰度、分异度显著低于盆地东部和东南部。综合前人资料, 目前在准噶尔盆地周边发现的珊瑚化石有约一半为地方性分子。本文认为研究区珊瑚化石的分布和组成特征与晚石炭世准噶尔洋走向封闭或半封闭的演化趋势密切相关。     

新疆准噶尔盆地周边晚石炭世的珊瑚*

新疆北部准噶尔盆地周边石炭系广泛出露, 其中上石炭统发育海相火山—沉积序列, 包括西准噶尔地区的哈拉阿拉特组、阿腊德依克赛组, 东准噶尔地区的石钱滩组以及盆地南部的祁家沟组、奥尔吐组等。本文研究在上述各地层的灰岩层或夹层、碎屑岩中获得的四射珊瑚9属17种和床板珊瑚2属3种, 对石钱滩组中的3个新种进行了详细的系统古生物学描述。上述珊瑚化石的地质时代主要为巴什基尔期至莫斯科期。在珊瑚动物群的组成上, 哈拉阿拉特组中新发现Caninophyllum属分子, 结合盆地东、西部共同产出的床板珊瑚Cystodendropora 属分子, 说明整个准噶尔盆地周边的动物群面貌大致类似, 而西准噶尔地区的化石丰度、分异度显著低于盆地东部和东南部。综合前人资料, 目前在准噶尔盆地周边发现的珊瑚化石有约一半为地方性分子。本文认为研究区珊瑚化石的分布和组成特征与晚石炭世准噶尔洋走向封闭或半封闭的演化趋势密切相关。     

Upper Ordovician bryozoans from the Xiazhen Formation of Yushan,northeastern Jiangxi,East China

The bryozoan fauna from the Xiazhen Formation (Katian, Upper Ordovician) of northeast Jiangxi Province, southeast China is reported here. Seventeen species of bryozoans belonging to fifteen genera and four orders are identified: Homotrypa yushanensis, Homotrypa sp., Prasopora yushanensis, Trematopora sp., Monotrypella sp., Rhombotrypa sp., Orbignyella sp., Constellaria jiangxiensis, Constellaria sp., Stictopora nicholsoni, Trigonodictya parvula, Ptilodictya ensiformis, Stictoporella sp., Pseudopachydictya sp., Nematopora sp., Arthrostylidae sp. indet., and Chasmatoporidae sp. indet. Four of these genera have been reported previously but nine genera (Trematopora, Monotrypella, Rhombotrypa, Orbignyella, Trigonodictya, Ptilodictya, Stictoporella, Pseudopachydictya, and Nematopora), one rhabdomesine and one fenestrate are found for the first time in the Late Ordovician strata of South China. Our palaeogeographical analysis suggests that the bryozoan association is typical for the Katian, which is mostly widespread in Laurentia, Siberia, Baltica and Mediterranean, and displays palaeobiogeographical relationships to the Laurentia–Siberia Province.     

Magnetostratigraphy susceptibility of the Upper Ordovician Kope Formation,northern Kentucky

As a test of the utility of magnetic susceptibility (MS) measurements for correlation among lithified marine sequences, samples were collected from well-studied shale and limestone outcrops of the Upper Ordovician Kope Formation, northern Kentucky. The bulk (initial) low-field MS of these samples is compared among two litho- and biostratigraphically correlated sections containing the same beds. The results of this comparison demonstrated an excellent correlation among equivalent beds. Thermomagnetic susceptibility analysis supports previous XRD work indicating that illite is primary and is the main paramagnetic mineral responsible for the MS variations observed in this study. A composite of MS results for a sequence of 31 named shale–limestone couplets is used to build a composite section of Kope sequences for the area. These MS variations permit division of the various sections into a set of 28 MS cycles within the Kope Formation, covering ∼ 50 m of section. These cycles suggest a systematic control by climate on the influx of detrital material that formed these sedimentary sequences, and support other work indicating Kope climate cyclicity.     

Timing and Spatial Distribution of Loess in Xinjiang,NW China

Central Asia is one of the most significant loess regions on Earth, with an important role in understanding Quaternary climate and environmental change. However, in contrast to the widely investigated loess deposits in the Chinese Loess Plateau, the Central Asian loess–paleosol sequences are still insufficiently known and poorly understood. Through field investigation and review of the previous literature, the authors have investigated the distribution, thickness and age of the Xinjiang loess, and analyzed factors that control these parameters in the Xinjiang in northwest China, Central Asia. The loess sediments cover river terraces, low uplands, the margins of deserts and the slopes of the Tianshan Mountains and Kunlun Mountains and are also present in the Ili Basin. The thickness of the Xinjiang loess deposits varies from several meters to 670 m. The variation trend of the sand fraction (>63 μm) grain-size contour can indicate the local major wind directions, so we conclude that the NW and NE winds are the main wind directions in the North and South Xinjiang, and the westerly wind mainly transport dust into the Ili basin. We consider persistent drying, adequate regional wind energy and well-developed river terraces to be the main factors controlling the distribution, thickness and formation age of the Xinjiang loess. The well-outcropped loess sections have mainly developed since the middle Pleistocene in Xinjiang, reflecting the appearance of the persistent drying and the present air circulation system. However, the oldest loess deposits are as old as the beginning of the Pliocene in the Tarim Basin, which suggests that earlier aridification occurred in the Tarim Basin rather than in the Ili Basin and the Junggar Basin.     

新疆柯坪和甘肃平凉上奥陶统底部附近的牙形刺

新疆柯坪大湾沟和甘肃平凉官司庄剖面是Nemagraptusb gracilis带及上奥陶统底界的重要剖面,研究这两剖面的牙形刺具有十分重要的意义。本文描述了采自新疆柯坪大湾沟和甘肃平凉官司庄剖面上奥陶统底界附近的牙形刺共13属18种。     

The palaeoecology of the Upper Ndolanya Beds at Laetoli,Tanzania

The palaeoecology of the fauna from the Ndolanya Beds, Laetoli, Tanzania, has been analysed to reconstruct the environment of this 2.6 Ma site. Community profiles have been constructed in relation to three variables that carry ecological meaning: body weight, locomotor adaptations and feeding preferences. Comparing the similarities and differences in the structure of the fossil faunas with those of modern environments allows us to draw inferences about palaeoenvironmental conditions, and this is based on a comparative dataset of 15 modern environments (44 localities) covering a wide range of climatic and ecological conditions across Asia, Africa and Central America. In addition, 16 fossil sites in East and South Africa have been analysed in the same way, and both sets of comparative data have been used as the basis for comparison with an ecological diversity analysis of the fauna from the Upper Ndolanya Beds. The Ndolanya fauna is characterized by a predominance of medium to large sized terrestrial and herbivorous species.There is evidence of taphonomic bias that eliminated many of the smaller species. A comparison of multivariate analyses of 23 selected modern localities conducted both with and without the small species included, indicates that the loss of these species does not adversely influence the results of an ecological diversity analysis. The evidence suggests that at the time of the deposition of the Ndolanya Beds the Laetoli region was a semi-arid bushland. This is considerably drier and more open than is suggested for the earlier Laetolil Beds.     

Oldest known Dicoelosia and Epitomyonia,deep water brachiopods from the Beiguoshan Formation (Middle Katian,Upper Ordovician), Shaanxi,north China

Abstract: A diverse brachiopod fauna from a relatively deep water carbonate facies of the Upper Ordovician Beiguoshan Formation (uppermost Caradoc – lower Ashgill, middle Katian) is characterized by small shells and contains the oldest known Dicoelosia and Epitomyonia, two diagnostic taxa of deep water brachiopod palaeocommunities during the Late Ordovician and Silurian. Three new species are recognized: Dicoelosia cordiformis sp. nov., Dicoelosia perbrevis sp. nov. and Epitomyonia fui sp. nov. These pioneer forms of the family Dicoelosiidae show a relatively high degree of morphological plasticity. The shells of Dicoelosia from the Beiguoshan Formation range from the typical slender‐lobed form with a concavoconvex profile to the strongly equibiconvex, fat‐lobed morphotype that was not known previously until the late Silurian. The Beiguoshan dicoelosiids point to an important attribute of the deep water brachiopods: small generalists with high morphological plasticity, which make them ideal candidates as progenitors for the evolution of shallow water brachiopod faunas in shelf and platform depositional environments.