Late Quaternary lake evolution in the Gaxun Nur basin,central Gobi Desert,China, based on quartz OSL and K‐feldspar pIRIR dating of paleoshorelines     

《第四纪科学杂志》2017,32(3):347-361

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A complete titanosaur femur from West Texas with comments regarding hindlimb posture     

《Cretaceous Research》2014

An isolated titanosaur femur recovered from the Javelina Formation (Maastrichtian) of Big Bend National Park, Texas is the most complete example yet reported from North America. The specimen is likely referable to Alamosaurus sanjuanensis, the only titanosaur thus far known from Upper Cretaceous strata in North America, but cannot be attributed with certainty to that taxon. Compared to femora from other titanosaurs, the specimen has a relatively reduced abductor crest, a less elevated femoral head, and a distal joint surface that is orthogonal to the long axis of the shaft. These differences suggest that the Big Bend femur pertains to a species where hindlimb stance was closer to vertical, and with a comparatively narrower gait than other titanosaurids.  相似文献   

扎格罗斯前陆盆地晚中新世快速剥露证据——来自磷灰石(U- Th)/He的约束     

李佳纬  孙继敏  吕丽星  张志亮  田晟辰  曹萌萌  李有生  苏柏 《地质学报》2020,94(12):3674-3688

伊朗扎格罗斯造山带是世界上最年轻的造山带之一，前人对其构造演化历史的研究尚存争议。前陆盆地蕴藏着丰富的造山带热史信息，为研究造山带的隆升和剥露历史提供了重要途径。本研究选取位于扎格罗斯前陆盆地前缘中部的Kuh- E Bedush向斜和Kuh- E Murdeh向斜翼部出露的第三纪陆相红层(Agha Jari组)为研究对象，共采集11个粗砂岩样品进行磷灰石(U- Th)/He测试分析。11个样品共得到38个单颗粒年龄，年龄区间为0. 8~79. 9Ma。大部分样品的单颗粒年龄比较分散，表明这些样品没有发生完全热重置。相反，位于Murdeh向斜剖面最底部的样品，(U- Th)/He年龄小于其对应的地层年龄，并且集中分布在8. 3~6. 8Ma，表明该样品发生了完全重置并记录了最后一次剥露事件的时间。因此，我们认为扎格罗斯前陆盆地于晚中新世~7. 5 Ma经历了一期快速剥露事件。此外，我们发现未重置的(U- Th)/He年龄大致分布在四个时间段：晚白垩纪—早古新世、早—中始新世、渐新世、早—中中新世。根据所得热年龄并结合前人研究设定了三种不同的热史，正演模拟结果与实际样品拟合较好，由此推断出前陆中部Agha Jari陆相红层沉积物可能来自于：①晚白垩世以来以蛇绿岩套为主的仰冲体持续剥露；②萨南达季- 锡尔詹变质带(SSZ)渐新世和中新世逐渐加速的剥露；③渐新世末堆积在仰冲体之上的同造山期砾岩，在中新世的大规模逆冲作用下重新剥露。  相似文献   

东天山博格达晚石炭世双峰式火山岩地球化学特征及意义     

刘亮  李江涛  江辉  杨宇东  何文劲  王莲  王傅佳 《岩石矿物学杂志》2020,39(5):525-538

东天山博格达造山带晚石炭世柳树沟组为一套由玄武岩和流纹岩组成的双峰式火山岩,形成于晚石炭世,其Si O_2含量介于46.18%～46.56%和76.06%～76.25%之间,具有明显的Daly成分间断。其中,玄武岩具富Na贫K特征,Ti O_2、Al_2O_3、Ca O和MgO含量均较高,∑REE为75.54×10~(-6)～80.22×10~(-6),LREE/HREE值为3.00～3.12,以富集Ba、Rb等大离子亲石元素(LILE)和不相容元素(P、K),相对亏损Ti、Ta、Nb等高场强元素(HFSE)和不相容元素(U、Th)为特征;流纹岩Na_2O/K_2O值为0.32～0.36,属低Ti、低Mg类流纹岩,∑REE为520.72×10~(-6)～595.26×10~(-6),LREE/HREE值为5.60～6.53,具有Rb、Th、K、La、Ce、Zr、Hf、Sm等元素的富集以及Ba、U、Ta、Nb、Sr、P和Ti元素的亏损特征。柳树沟组双峰式火山岩形成于大陆裂谷环境,具板内成因特征,玄武岩可能为亏损尖晶石相地幔橄榄岩向石榴石相地幔橄榄岩过渡相较高程度部分熔融的产物,受到地壳物质混染;流纹岩具典型的A型花岗岩的地球化学特征。  相似文献   

中国南天山晚石炭世—早二叠世花岗质侵入岩的岩石成因与地壳增生   总被引：9，自引：0，他引：9  

黄河  张招崇  张东阳  杜红星  马乐天  康健丽  薛春纪 《地质学报》2011,85(8):1305-1333

晚石炭世—早二叠世在中亚南天山造山带形成了大量的花岗质侵入岩.中国境内这些岩体以晚石炭世Ⅰ型花岗岩、早二叠世Ⅰ型和S型花岗岩以及最晚期的A型花岗岩为代表.不同类型的岩石在源区特征和岩浆形成的温压条件上存在一定的差异,而这些差异性反映了该时期内构造环境的演化过程.本文选取铁列克岩体、盲起苏岩体、英买来岩体、川乌鲁杂岩体、...  相似文献   

Late glacial and holocene landscapes of central Beringia     

Anatoly V. Lozhkin  Patricia Anderson  Wendy R. Eisner  Tatiana B. Solomatkina 《Quaternary Research》2011,76(3):383-392

New palynological and sedimentological data from St. Lawrence Island present a rare view into late-glacial and Holocene environments of the central Bering Land Bridge. The late glaciation was a time of dynamic landscape changes in south-central Beringia, with active thermokarst processes, including the formation and drainage of thaw lakes. The presence of such a wet, unstable substrate, if widespread, probably would have had an adverse impact on food sources and mobility for many of the large mammal populations. The establishment of Betula shrub tundra on the island suggests late-glacial summers that were warmer than present, consistent with regional paleoclimatic interpretations. However, the increasing proximity to the Bering Sea, as postglacial sea levels rose, modified the intensity of warming and prevented the establishment of deciduous forest as found in other areas of Beringia at this time. The mid- to late Holocene is marked by more stable land surfaces and development of Sphagnum and Cyperaceae peat deposits. The accumulation of organic deposits, decline of shrub Betula, and decrease in thermokarst disturbance suggest that conditions were cooler than the previous. A recent decline in peat accumulation at the study sites may relate to local geomorphology, but similar decreases have been noted for other arctic regions.  相似文献   

Associated terrestrial and marine fossils in the late-glacial Presumpscot Formation, southern Maine, USA, and the marine reservoir effect on radiocarbon ages   总被引：1，自引：0，他引：1  

Woodrow B. Thompson  Carol B. Griggs  Norton G. Miller  Robert E. Nelson  Thomas K. Weddle  Taylor M. Kilian   《Quaternary Research》2011,75(3):552-565

Excavations in the late-glacial Presumpscot Formation at Portland, Maine, uncovered tree remains and other terrestrial organics associated with marine invertebrate shells in a landslide deposit. Buds of Populus balsamifera (balsam poplar) occurred with twigs of Picea glauca (white spruce) in the Presumpscot clay. Tree rings in Picea logs indicate that the trees all died during winter dormancy in the same year. Ring widths show patterns of variation indicating responses to environmental changes. Fossil mosses and insects represent a variety of species and wet to dry microsites. The late-glacial environment at the site was similar to that of today's Maine coast. Radiocarbon ages of 14 tree samples are 11,907 ± 31 to 11,650 ± 50 ¹⁴C yr BP. Wiggle matching of dated tree-ring segments to radiocarbon calibration data sets dates the landslide occurrence at ca. 13,520 + 95/−20 cal yr BP. Ages of shells juxtaposed with the logs are 12,850 ± 65 ¹⁴C yr BP (Mytilus edulis) and 12,800 ± 55 ¹⁴C yr BP (Balanus sp.), indicating a marine reservoir age of about 1000 yr. Using this value to correct previously published radiocarbon ages reduces the discrepancy between the Maine deglaciation chronology and the varve-based chronology elsewhere in New England.  相似文献   

广东连州长兴期含煤地层     

姚兆奇  陈楚震  芮琳  刘陆军 《地层学杂志》2011,(1):55-65

九陂组(亚田煤组)是粤北和湘南晚二叠世重要的含煤地层,其下伏"梅田灰岩"的涵义和(虫筵)化石Gallowayinella meitienensis的层位问题曾长期未得澄清.通过对梅田组剖面的详细工作,建立了下部的Gallowayinella组合和上部的Nanlingella jiaozishanica-Sphaerul...  相似文献   

江苏江都市大桥镇晚更新世晚期—全新世有孔虫动物群的发现及其地质意义     

韦一  韩芳  魏乃颐  于庆文  张智勇  张克信 《地质科技情报》2011,30(3):41-47

在江苏省江都市ZKA4钻孔孔深4.0～42.6 m岩心段中发现有孔虫化石,鉴定识别出有孔虫38属56种,其中9个未定种,根据有孔虫动物群在钻孔剖面上的分布规律,建立了 3个有孔虫化石组合,自上而下为:Ammonia beccarii Linne)vars.-Orbulina universa组合,Ammonia bec...  相似文献   

Description and Phylogenetic Position of Dinosaur Eggshells from the Luanchuan Area of Western Henan Province, China     

Kohei TANAKA  Lü Junchang  Yoshitsugu KOBAYASHI  Darla K. ZELENITSKY  XU Li  JIA Songhai  QIN Shuang  TANG Min’an 《《地质学报》英文版》2011,85(1):66-74

Here, we examine 145 dinosaur eggshells from a new fossil locality in the Qiupa Formation (Upper Cretaceous) of the Luanchuan area in western Henan Province, China. The eggshells display elongatoolithid macro- and microstructures, including ridges and nodes on the outer surface, two ultrastructural layers, and an undulatory boundary between the mammillary and continuous layers. A phylogenic analysis shows that the Luanchuan eggshells belong to the ooclade Elongatoolithidae. Within Elongatoolithidae, the thickness ratio of the mammillary layer to the entire eggshell, and the porosity of the Luanchuan eggshells are comparable to the oogenera Macroolithus and Elongatoolithus. There is no direct evidence for the taxonomic identity of the Luanchuan eggshells; however, they were likely laid by oviraptorids based on their phylogenetic position and their similarities with known oviraptorid eggs.  相似文献