• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文学位 >Stratigraphy, age, and systematics of two new fossil whales from Angola and stable isotope geochemistry of chicken eggshell, dinosaur eggshell, and paleosol carbonates: Early burial diagenesis in late cretaceous sediments of the Gobi basin, Mongolia.
【24h】

Stratigraphy, age, and systematics of two new fossil whales from Angola and stable isotope geochemistry of chicken eggshell, dinosaur eggshell, and paleosol carbonates: Early burial diagenesis in late cretaceous sediments of the Gobi basin, Mongolia.

机译：安哥拉的两种新化石鲸的地层学，年龄和系统，以及鸡蛋壳，恐龙蛋壳和古土壤碳酸盐的稳定同位素地球化学：蒙古戈壁盆地晚白垩世沉积物中的早成岩作用。

获取原文
获取原文并翻译 | 示例
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Ongoing field work in Angola, under auspices of Projecto PaleoAngola, has yielded fossil cetaceans from deposits of Miocene age, providing new insights into the early diversification of cetaceans along the western African coast. Here two new taxa of mysticete whales are described. PA 165 comprises a partial articulated skull, an unfused cervical vertebra, and a partial thoracic vertebra. The skull includes the nasals, proximal premaxillae and maxillae, the supraoccipital shield, left squamosal, exoccipital, periotic, and frontal. Portions of both dentaries are present. PA 166 comprises a partial articulated skull including the region posterior to and including the nasals. The proximal portions of the maxillae and premaxillae are present. Both specimens were recovered from what appears to be the Luanda Formation, a calcareous sandstone of late Miocene age. Phylogenetic analysis indicates these fossils represent two new taxa nested with Caperea marginata, the pygmy right whale, in the Neobalaenidae, a family currently restricted to one living species inhabiting cold temperature Southern Hemisphere waters and one fossil species, Miocaperea pulchra, from South America. Three characters unite the new Angolan taxa with Caperea, including the posterolateral corner of the exoccipital projecting posterior to the occipital condyle, the anterior portion of the supraoccipital articulating with the rostral bones and overlaying the frontal and parietal at the vertex of the skull, and the anterior projection of the parietal dorsal to the supraorbital process of the frontal. Two characters distinguish the Angolan taxa from Caperea , including the lateral and medial margins of the ascending process of the maxilla remain parallel terminating in a squared posterior margin and the ventrolaterally oriented postglenoid process in posterior view. Neobalaenidae is a sister group to Eschrichtiidae and Balaenopteridae. These new taxa are two new fossil representatives of Neobalaenidae and they extend the families range into the Miocene phase of the Benguela Large Marine Ecosystem.;Fragmentary fossil eggshell is often used for isotopic analysis when complete eggshell is not available. These analyses are carried out under the assumption that inorganic eggshell carbonate has a homogenous isotopic composition. Isotopic analyses of three modern chicken (Gallus gallus) eggshells to test the homogeneity of the isotopic composition of the eggshell carbonate. Twenty-five samples were collected along three major axes of all three eggshells for the analyses. Standard deviations for &dgr;13C values are about 0.6‰ and standard deviations of &dgr;18O are about 0.15‰. These low standard deviations suggest that the isotopic composition of the eggshell carbonate is homogenous and that spot sampling fossil eggshell for isotopic analysis produces an isotopic composition representative of the entire eggshell.;Khermeen Tsav, Bugin Tsav, Altan Ula, Nugin Tsav, Narin Bulak, and Gurlin Tsav are fossil-rich localities of southwest Mongolia comprised of Campanian-Maastrichtian strata within the Barungoyot and Nemegt Formations. The light stable carbon and oxygen isotopic compositions of fossil eggshells and paleosol carbonates recovered from these localities were analyzed to evaluate the diagenetic history of this locality and to assess whether an original paleoenvironmental signal is preserved. Fourty-two paleosol carbonate samples and sixty fossil eggshell calcite samples were analyzed petrographically to delineate a paragenetic sequence of diagenetic cementation. Diagenesis was recognized within several generations of luminescent calcite growth. Paleosol carbonate &dgr; 13C and &dgr;18O values range from -0.7 to -8.4‰ and 5.6 to -12.2‰ respectively and eggshell calcite &dgr;13 C and &dgr;18O values range from -14.5 to 2.8‰ and -16.6 to 0.7‰ respectively. The eggshell calcite of both luminescent and non-luminescent samples show isotopic signatures that are similar to those of the paleosol carbonates, suggesting a diagenetic signature affects many of the samples analyzed. Two trends were recognized within the isotopic data, an enrichment of &dgr;18O values due to diagenetic alteration within the vadose zone and and enrichment of &dgr;13C values due to diagenetic alteration within the phreatic zone. The geochemical and petrographic analysis of the paleosol carbonates suggests that meteoric waters are responsible for the secondary diagenetic signature occurring during early burial. &dgr;13C values of these eggshell and paleosol carbonate samples that are least altered confirm the presence of C3 plants upon a semiarid Late Cretaceous landscape. Cathodoluminescence and petrographic analyses revealed that there were varying degrees of secondary alteration within the eggshells. This study provides a record of early diagenesis within the Gobi Basin and will provide a new methodology to determine the extent of alteration within fossil eggshell in general.
机译：在Projecto PaleoAngola的主持下，正在进行的安哥拉野外工作已从中新世时代的沉积物中产出了鲸类化石，这为西非沿海鲸类的早期多样化提供了新见识。这里描述了两个神秘的鲸鱼新分类群。 PA 165包括部分关节的头骨，未融合的颈椎和部分胸椎。头骨包括鼻，上颌前和上颌近端，枕上盾，左鳞状，枕外，腹膜和额叶。存在两个牙齿的部分。 PA 166包括部分铰接的头骨，该头骨包括鼻后部和鼻部。存在上颌骨和前颌骨的近端部分。这两个标本都是从中新世晚期钙质砂岩罗安达组中发现的。系统发育学分析表明，这些化石代表了新鳞翅目科的两个新的类群，它们与海龟边缘的小侏儒右鲸嵌套在一起，该科目目前仅限于一种生活在南半球南半球水域的活生物种，以及一种化石种，来自南美的Miocaperea pulchra。三个角色将新的​​安哥拉分类群与Caperea结合在一起，包括枕骨后突到枕骨con后方的后外侧角，枕上前部与喙骨关节并在头骨顶点处覆盖额叶和顶叶，以及顶叶背的前投影到额眶上突。两个字符将安哥拉分类群与开普雷区分开来，包括上颌骨上升过程的外侧边缘和内侧边缘保持平行，终止于平方后缘，而后视图中腹侧取向的后盂突。 Neobalaenidae是Eschrichtiidae和Balaenopteridae的姐妹群。这些新的分类群是新伞虫科的两个新的化石代表，它们将本族范围扩展到本格拉大型海洋生态系统的中新世相。当没有完整的蛋壳时，碎片化石蛋壳常用于同位素分析。这些分析是在无机蛋壳碳酸盐具有均匀同位素组成的假设下进行的。对三个现代鸡（蛋鸡）蛋壳进行同位素分析，以测试蛋壳碳酸盐同位素组成的均质性。沿所有三个蛋壳的三个主轴收集了25个样品进行分析。 13 C值的标准偏差约为0.6‰，18 O的标准偏差约为0.15‰。这些低的标准偏差表明，蛋壳碳酸盐的同位素组成是均质的，对化石蛋壳进行同位素分析的现场采样会产生代表整个蛋壳的同位素组成。 Gurlin Tsav和Gurlin Tsav是蒙古西南部富含化石的地区，包括Barungoyot组和Nemegt组内的Campanian-Maastrichtian地层。分析了从这些地区回收的化石蛋壳和古土壤碳酸盐的光稳定碳和氧同位素组成，以评估该地区的成岩史，并评估是否保留了原始的古环境信号。岩石学分析了42个古土壤碳酸盐样品和60个化石蛋壳方解石样品，以描绘出成岩胶结作用的亚生序列。成岩作用在几代发光方解石的生长中得到了认可。碳酸古土壤13C和18O值分别在-0.7至-8.4‰和5.6至-12.2‰，蛋壳方解石13C和18O值分别在-14.5至2.8‰和-16.6至0.7‰。发光样品和不发光样品的蛋壳方解石均显示出与古碳酸盐碳酸盐相似的同位素特征，表明成岩作用影响了许多分析样品。同位素数据中确认了两个趋势，是由于渗流区内的成岩作用改变而使18 O值富集，以及由于潜水区的成岩作用引起了13C值富集。对古土壤碳酸盐的地球化学和岩石学分析表明，陨石水是造成早期埋藏期间次生成岩特征的原因。这些蛋壳和古土壤碳酸盐样品变化最小的δ13C值证实了半干旱晚白垩世景观中C3植物的存在。阴极发光和岩石学分析表明，蛋壳内有不同程度的次级变化。这项研究提供了戈壁盆地内早期成岩作用的记录，并将提供一种确定总体上化石蛋壳内部变化程度的新方法。

著录项

  • 作者

    Graf, John F.;

  • 作者单位

    Southern Methodist University.;

  • 授予单位 Southern Methodist University.;
  • 学科 Paleontology.;Geology.;Geochemistry.
  • 学位 Ph.D.
  • 年度 2016
  • 页码 229 p.
  • 总页数 229
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

相似文献

  • 外文文献
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号