Mammalian femora across the Cretaceous–Paleogene boundary in eastern Montana     

《Cretaceous Research》2014

Our understanding of latest Cretaceous and earliest Paleogene mammalian evolution is based almost entirely on the dental fossil record. Mammalian postcranial fossils are rare and mostly found as isolated elements in latest Cretaceous and earliest Paleogene vertebrate microfossil assemblages of North America. Although placing these fossils in a tooth-based taxonomic framework is difficult, they can provide insight into locomotor diversity and habitat preference to complement diet reconstructions and diversity estimates from dental fossils. Here, we describe 64 femora of mammals recovered from latest Cretaceous (Lancian) and earliest Paleogene (Puercan) localities in eastern Montana. We sorted these based on morphology and size (morphotypes). In some cases, morphotypes were tentatively assigned to dentally based taxa that are known from these strata.Although our resulting femoral dataset is small relative to the study area's dental dataset, we show several key findings. First, there is a greater morphological diversity of multituberculate femora than previously recognized, especially in the latest Cretaceous sample. In contrast, metatherians, which have a high relative abundance in Lancian Hell Creek Formation dental assemblages, are absent from our postcranial samples; eutherian femora are only present in the Puercan assemblages. Second, we record a minor decrease in morphotype richness across the K–Pg boundary that is associated with an increase in mean specimen size, due to the appearance of a few significantly larger-bodied, immigrant taxa. Among the eutherians, there are two specimens of larger-bodied early Puercan archaic ungulates, a very large specimen of a middle/late Puercan taeniodont, pantodont, or triisodontid, as well as a specimen possibly attributed to a “plesiadapiform” archaic primate. Third, preliminary functional morphologic analyses of the more complete specimens suggest that locomotor diversity increased from mainly arboreal or terrestrial/saltatorial multituberculates in the latest Cretaceous to include a fossorial multituberculate and potentially an arboreal eutherian in the early Paleocene. These patterns parallel those previously reported from a dental dataset and indicate that postcranial data are valuable as an independent means to test hypotheses of taxonomic and ecomorphological diversity across the K–Pg boundary.  相似文献   

胶西北新城金矿床硫同位素地球化学   总被引：8，自引：6，他引：2  

张潮  刘育  刘向东  冯建秋  黄涛  张庆  王旭东 《岩石学报》2014,30(9):2495-2506

新城金矿床是胶西北金矿集区中典型的破碎带蚀变岩型金矿床,其热液成矿作用可划分为四个阶段:黄铁矿-石英-绢云母阶段(I)、石英-黄铁矿阶段(II)、石英-多金属硫化物阶段(III)和石英-方解石阶段(IV),其中金主要赋存于II和III阶段的黄铁矿内。该矿床赋矿围岩为郭家岭岩体,岩性为石英二长岩和二长花岗岩,主要为胶东群变质基底经部分熔融形成。胶东群变粒岩硫同位素较为均一(δ34S值介于6.9‰~9.4‰,均值为8.0‰);郭家岭岩体的δ34S值介于6.0‰~16.0‰,均值为8.6‰,反映了其硫同位素组成总体上继承了变粒岩的硫同位素特征;长英质脉岩的δ34S值变化范围为0.8‰~8.5‰(均值为6.7‰),其中4件样品的δ34S值变化范围为7.4‰~8.5‰,反映了其硫主要源自于郭家岭岩体,变粒岩可能提供了部分硫源;而其中1件样品的δ34S值仅为0.8‰,符合岩浆硫来源特征,表明深部岩浆可能也提供了部分硫源。新城金矿床矿石中硫化物δ34S值变化范围较大(4.3‰~10.6‰,均值为8.3‰),表明矿石硫可能源于郭家岭岩体、变粒岩和长英质脉岩,最终主要来源于胶东群变质基底。I阶段黄铁矿颗粒较小(5~600μm),晶形主要为立方体,反映其处于温度较高(300~350℃)、成矿流体的过饱和度较低、低氧逸度和硫逸度、冷却快速、物质供应不足的成矿环境;黄铁矿δ34S值变化范围为8.4‰~10.6‰,均值为9.7‰,反映了矿石硫可能源自于δ34S值较高的郭家岭岩体和变粒岩。II和III阶段黄铁矿粒径变化较大(3μm~2.5mm),晶形主要为五角十二面体,反映其处于中-低温度(200~300℃)、成矿流体过饱和度高、高氧逸度和硫逸度、缓慢冷却同时物质供应充分的成矿环境。其中,II阶段黄铁矿δ34S值变化范围为7.7‰~9.7‰,均值为8.7‰,表明矿石硫源除郭家岭岩体和变粒岩外,δ34S值较低的长英质脉岩可能也提供了部分硫源。III阶段硫化物δ34S值变化范围较大(4.3‰~9.4‰,均值为7.1‰),闪锌矿-方铅矿硫同位素热力学平衡温度范围为180~282℃,氧逸度约为10-37.3~10-36.8,反映了矿石硫源自于郭家岭岩体、变粒岩和长英质脉岩,硫化物δ34S值变化范围较大可能是硫同位素分馏达到平衡的结果。IV阶段黄铁矿粒径最小(1~5μm),为晶形完好、表面光滑的立方体晶形,表明其处于较低温度(200℃),成矿流体的过饱和度较低、氧逸度和硫逸度较低、物质供应不足的成矿环境。  相似文献   

新疆及邻区体波震级初步分析研究     

冉慧敏  李文倩  上官文明 《中国地震》2022,38(1):91-101

依据《地震震级的规定（GB 17740—2017）》,分析了2009—2017年新疆地震台网所记录的新疆及邻区476次中深源地震事件,测定了13601个m_b（短周期体波震级）和12035个m_B（BB）（宽频带体波震级）的数据样本,回归分析m_b和m_B（BB）得到回归方程及量规函数,结果显示m_b和m_B（BB）相关系数为0.966,表明两者显著相关。因此,建议对于中强型中深源地震可以直接从原始速度型宽频带数字地震记录上测定长周期体波震级m_B（BB）,提高地震速报测定的速度和精度。通过震级偏差统计和台站场地响应计算,分析新疆地震台网中的XKR、HTA、ATS和KSZ等地震台站震级偏差较大的原因为砂岩、灰岩、砂土层等类型的台基放大了场地响应,说明台基类型对体波震级偏差的影响较大。与NEIC测定的体波震级对比时,发现新疆地震台网测定体波震级平均偏大0.42级,且偏差随着震源深度的增加有增大的趋势。  相似文献   

New material of the large-bodied caenagnathid Caenagnathus collinsi from the Dinosaur Park Formation of Alberta,Canada     

《Cretaceous Research》2015

A reexamination of large caenagnathid material from the Upper Cretaceous (Campanian) Dinosaur Park Formation of Alberta, Canada, reveals undescribed material referable to Caenagnathus collinsi. A femur, two astragalocalcanei, two metatarsals, two unguals, and a caudal vertebra provide anatomical information on Caenagnathus collinsi. Estimates of femoral length based on the proportions of other oviraptorids suggest that the non-femoral material represents a taxon intermediate in size between Chirostenotes pergracilis from the Dinosaur Park Formation and Anzu wyliei from the Maastrichtian Hell Creek Formation. The femur is within the range of predictions, and confirms the body size estimates based on the other material. The large size of the material and a number of morphological characters distinguish the material from Chirostenotes pergracilis and suggest that it is referable to Caenagnathus collinsi. The relative diversity of caenagnathids in the Dinosaur Park Formation is likely underestimated.  相似文献   

Beating words to life: subtitles,assemblage(s)capes,expression     

Giorgio Hadi Curti 《GeoJournal》2009,74(3):201-208

Ostensibly, subtitles in films serve as linguistic approximations of meaning. Expectedly then, much of the debate surrounding subtitling has been concerned with representational accuracy, fidelity and authenticity. In this article I argue that by encountering subtitles as affective bodily expressions, as opposed to approximate representations of pre-existent meanings or intentions, filmic experiences may be(come) transformed and differently transformational. As a result, meaning and accuracy in subtitles as superimposed signifiers or static representations become secondary to subtitles as spatially affective- and expressive-movements intimately part of filmic scapes. The creative use of subtitling in Bekmambetov’s Russian language film Night Watch (Nochnoy dozor; 2006 [2004]) is discussed.

Giorgio Hadi CurtiEmail:

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Research progress on layered seismic anisotropy - A review     

《地震研究进展（英文）》2021,1(1):100005

Seismic anisotropy is an effective feature to study the inner structure of the Earth. In complex tectonic area, the assumption of single-layer anisotropy is sometimes not well consistent with the observed data; thus, the assumption of multi-layered (i.e. stratified) anisotropy should be considered. At present, the main methods to study anisotropy include receiver functions, shear wave splitting from local and teleseismic events (SKS, SKKS, and PKS, hereafter collectively called XKS), P- and Pn wave travel time inversion, surface wave inversion from far-field earthquakes and ambient noise. Each of the above method has its own advantages and limitations. Thus, one or more of the above methods are often combined to characterize multi-layered anisotropy, of which the depth range of anisotropic layers are different. This paper reviews the research progress of multi-layered anisotropy for the purpose of providing a basis for future seismic anisotropy investigations.  相似文献   

1998年1月10日张北-尚义6.2级地震前昌平地震台应变资料的异常变化分析     

王勇  刘福生  张国红  张学政 《地震工程学报》1999,21(3):274-279

分析了昌平地震台体应变、线应变及差应变等观测资料在１９９８年１月１０日张北－尚义６．２级地震前的异常变化。结果表明：该次地震前昌平台的应变观测资料出现了明显的趋势异常;体应变的异常时间与震级有较发的相关性;差应变资料显示了短临异常;由线应变资料计算的主应变方向在地震前逐渐向震中偏转;Ｍ２波潮汐因子也出现了明显的异常变化。  相似文献   

体应变地震波最大振幅与地震震级和震中距的统计关系探讨     

姜佳宁  吴利军 《中国地震研究》2017,31(1):107-115

Based on the body strain record of Tiantanghe station from 2008 to 2014,we make a statistical analysis of the relationship between the maximum amplitude of the body strain record and the surface-wave magnitude,epicenter distance of the earthquakes,which occurred in the Chinese mainland and its surrounding areas with MS≥6. 0 and the rest of the world with MS≥7. 0. According to statistical results,we propose a statistical formula between the surface-wave magnitude of earthquake and the maximum amplitude of the body strain record,the epicenter distance: M_S~*= 0. 37 ln A_max+ 0. 57 ln D + 0. 07. We can also derive a theoretical estimation formula for the maximum amplitude: A_max=e~(2. 7(M_S~*-0. 07))D~(-1. 54). This demonstrates that the maximum amplitude of the body strain record increases exponentially with the increase of the surface-wave magnitude, and decreases with the increase of the epicenter distance,and shows a negative correlation with their product. We further discuss the necessity of adding instruments with high frequency sampling to earthquake monitoring, and dicuss the prospects for precise earthquake prediction in future.  相似文献   

Moment Magnitude and Its Calculation     

Chen Yuntai  Liu Ruifeng 《中国地震研究》2018,32(4):447-455

In this paper, we give a brief introduction to the proposal and development history of the earthquake magnitude concept. Moment magnitude M_W is the best physical quantity for measuring earthquakes. Compared with other magnitude scales used traditionally, moment magnitude is not saturated for all earthquakes, regardless of big and small earthquakes, deep and shallow earthquakes, far field and near field seismic data, geodetic and geological data, moment magnitude can be measured, and can be connected with well-known magnitude scales such as surface wave magnitude M_S. Moment magnitude is a uniform magnitude scale, which is suitable for statistics with wide magnitude range. Moment magnitude is the preferred magnitude selected by the International Seismological community, and it is preferred by the departments responsible for publishing seismic information to the public.Moment magnitude is a uniform magnitude scale, which is suitable for statistics with wide magnitude range. Moment magnitude is a preferred magnitude for international seismology, it is preferred by the agency responsible for providing information about earthquakes to the public. We provide all formulas used in the calculation of moment magnitude, and the calculation steps in detail. We also analyzed some problems and rules to solve these problems by using different formulas and numerical value calculation steps.  相似文献   

川滇地区壳幔地震各向异性研究进展     

张艺  高原  赵镇岭 《中国地震》2018,34(2):207-218

根据川滇地区已有的地震各向异性研究结果,利用体波、面波资料的结果,分析川滇地区不同构造尺度、不同深度的地震各向异性特征。对比不同方法研究川滇地区介质各向异性的特点,探讨了该地区的介质连续性及壳幔耦合状态。分析认为,地壳上地幔各向异性的差异表明,川滇地区具有复杂的地壳及上地幔形变机制。因此,对于川滇地区壳幔地震各向异性的深入理解,需在理论上和高密度数据资料基础上加强量化分析和综合研究。  相似文献