云南元谋古猿动物群化石埋藏学   总被引：2，自引：0，他引：2       下载免费PDF全文

张云翔  郑良等 《地质学报》2002,76(1):45-49

云南元谋小河-雷老一带含古猿新近系（上第三系）是一套紫红色含砾细砂-粉砂岩，夹有多层黄色砂砾石层。化石埋藏学研究及含化石层岩性特征、组合及沉积构造表明，该层以山前洪积堆积为主，并有发育的扇上河道沉积。通过30余个发掘地点化石野外埋藏资料及数千件化石标本的分析鉴定，化石埋藏类型有两种，埋藏Ⅰ型的化石数量稀少、保存完整，赋存在扇体细粒沉积物中；理藏Ⅱ型化石保存丰富但相当残破，赋存在粗粒沉积的扇上河道各个部位。化石埋藏类型与古气候、古生态有着密切的关系，化石埋藏特征表明该区自然环境分带已形成。元谋古猿动物群的生存时代是一个从森林向草原-灌丛环境过渡的动荡时期。  相似文献   

Upright crinoids of the Thornton Reef,Wenlock (Silurian) of Illinois,USA     

Stephen K. Donovan  Ron K. Pickerill  Donald G. Mikulic  Joanne Kluessendorf 《Geological Journal》1996,31(4):369-378

The rare preservation of columns perpendicular to bedding may provide convincing evidence that ancient crinoids adopted an upright attitude during life. However, taphonomic and sedimentological analyses are important in determining whether such occurrences are truly in situ or represent unusual allochthonous accumulations. The Crinoid Biosome of the Thornton Reef Complex, Silurian of Illinois, USA, includes pluricolumnals preserved perpendicular to bedding, in association with more common specimens parallel or angled to bedding. Upright pluricolumnals are relatively shorter (<150 mm) than the longest non-upright specimens; they sometimes occur as imbricate accumulations and lack attachment structures (although these are preserved separately). Brachiopod valves and colonial corals may also be preserved perpendicular to bedding. These features suggest that the Thornton beds were formed as viscous mass flow deposits and that the upright crinoid columns are allochthonous or, at best, parautochthonous. © 1996 John Wiley & Sons, Ltd.  相似文献   

Differential diatom dissolution in Late Quaternary sediments from Lake Manyara,Tanzania: an experimental approach   总被引：3，自引：0，他引：3  

Philip Barker 《Journal of Paleolimnology》1992,7(3):235-251

Diatom dissolution in saline lakes represents an important obstacle to the quantitative reconstruction of water chemistry and climate from lake sediment archives. This problem is here approached experimentally by artificially dissolving diatom-bearing core sediment from Lake Manyara, Tanzania. Manyara holds one of the longest continuous palaeolimnological records from tropical Africa although its interpretation is based on a fragmentary diatom record due to frustule dissolution. These experiments have revealed clear changes in assemblage composition as dissolution operated differentially with respect to diatom taxa. Differential dissolution has considerable impact on the water chemistry estimates derived from transfer functions. Taphonomy, rather than environmental change, may have been responsible for minor fluctuations in the diatom assemblages from Manyara, although major palaeohydrological changes during the Late Pleistocene and Early Holocene can be identified. Particularly well represented by MANE-87 is a period of intermediate lake level between 27 500 and 23 000 ¹⁴C yr BP which has regional palaeohydrological significance.  相似文献   

People and large carnivores as biostratinomic agents in Lateglacial cave assemblages     

T. C. Lord  T. P. O'Connor  D. C. Siebrandt  R. M. Jacobi 《第四纪科学杂志》2007,22(7):681-694

Biostratinomic analysis (processes acting between death and burial) of Lateglacial mammal bone assemblages from three caves in northern England demonstrates the value of re‐examining archived assemblages. With AMS radiocarbon dating of key specimens, these assemblages shed light on the ecology of a region at the northern limit of Lateglacial human activity in Britain. During the Lateglacial Interstadial bears, wolves and humans expanded into the region, bears by around 12 500 ¹⁴C yr BP, and the earliest evidence for human presence is around 12 300 ¹⁴C yr BP. At Victoria Cave, wolf activity included predation and scavenging of large ungulates and scavenging bear carcasses apparently resulting from hibernation deaths. The scavenging of bear carcasses is possibly confined to the first part of the Lateglacial Interstadial, whereas evidence for wolf scavenging large ungulates increases later in the Interstadial, after about 11 800 ¹⁴C yr BP, perhaps reflecting changes in the productivity of the Lateglacial ecosystem, and in human subsistence patterns. The assemblage from Sewell's Cave is wolf den debris from the very end of the Lateglacial Interstadial around 10 800 ¹⁴C yr BP, whilst that from Kinsey Cave is dominated by large‐bodied carnivores, and is argued to have a quite different taphonomic history. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

现代藻类磷酸盐埋藏学实验——对磷酸盐化球状化石研究的启示     

张神功  钟振华  陈雷  刘慧渊  杨锋杰 《地质学报》2023,97(12):4035-4043

产于贵州瓮安埃迪卡拉系陡山沱组磷块岩中的“瓮安生物群”是认识早期生命起源与演化的重要窗口。因为其特殊的磷酸盐化作用,其中的球状化石内部保存了大量精细的细胞甚至亚细胞结构,但保存这些化石的磷酸盐化作用机理尚不清楚。因此,本文采用绿藻门下团藻和空球藻为实验对象,通过改变pH、温度、氧气含量等实验条件,探索藻类在不同埋藏环境下的保存状况,为早期磷酸盐化化石的埋藏机制提供证据。实验结果显示藻类在不同实验条件下的保存潜力差距较大,相同环境下两种藻类所体现的保存潜力也不一致,但都具备足够的保存潜力;空球藻细胞在埋藏过程中出现褶皱变形,但在不同条件下的形态学差异并不明显;团藻的繁殖体形态与瓮安生物群中的一类多细胞球状化石的细胞分裂形式十分相似;早期状态一致的同种藻类不管在相同还是不同的实验条件下其个体直径大小均表现出较强的差异性。本次实验模拟自然状态下的埋藏环境,因此实验现象可能在现实埋藏过程中重现,通过实验得出以下结论：磷酸盐化的埋藏环境中藻类具备足够的保存潜力;磷酸盐化会导致生物获得自身以外的形态学信息;在不同的埋藏学环境下保存的磷酸盐化球状化石的直径大小会有差异;胚胎状化石与磷酸盐化的现生藻类...  相似文献   

河北秦皇岛斑鬣狗巢穴(灵仙洞)及斑鬣狗的集群死亡与埋藏     

刘金毅  Jan Wagner  陈平富  盛桂莲  陈津  江左其果  刘思昭 《第四纪研究》2015,35(3)

河北省秦皇岛灵仙洞发现了一批最后斑鬣狗化石,标本达上千件,至少代表了30个不同个体,包括3具骨架(其中骨架Ⅰ是世界上迄今所发现最完整的1具),还发现了一些其他哺乳动物化石,共计26属27种.根据动物群组成、地质地貌以及堆积物的综合分析判断,它的时代可能属于中更新世晚期至晚更新世早期.动物群的生态组合反映当时处于一个温热偏干、半封闭或开阔的山间草原而周边山上有树林的生态环境.标本(尤其是完整骨架)的保存为典型的原地埋藏,死后未受到包括斑鬣狗自身在内的动物干扰和破坏.斑鬣狗在动物群中占绝对优势以及幼年个体和粪化石的发现,表明灵仙洞是一处斑鬣狗族群的巢穴.与其他斑鬣狗巢穴不同的是:斑鬣狗的猎物稀少,鲜见斑鬣狗的活动痕迹,尤其是幼年斑鬣狗啃咬形成的特定产物“nibbling sticks”,这说明灵仙洞既非用于猎物遗骸的储藏,也非用于幼崽的抚养,而是一处共用巢穴,同时也表明灵仙洞的骨骼聚集与埋藏有着特定的成因和机理.  相似文献   

First fossil primates from Eckfeld Maar, Middle Eocene (Eifel, Germany)     

Jens Lorenz Franzen 《Eclogae Geologicae Helvetiae》2004,97(2):213-220

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A decline in molluscan carbonate production driven by the loss of vegetated habitats encoded in the Holocene sedimentary record of the Gulf of Trieste     

Adam Toma&#x;ových  Ivo Gallmetzer  Alexandra Haselmair  Darrell S. Kaufman  Borut Mavri   Martin Zuschin 《Sedimentology》2019,66(3):781-807

Carbonate sediments in non‐vegetated habitats on the north‐east Adriatic shelf are dominated by shells of molluscs. However, the rate of carbonate molluscan production prior to the 20th century eutrophication and overfishing on this and other shelves remains unknown because: (i) monitoring of ecosystems prior to the 20th century was scarce; and (ii) ecosystem history inferred from cores is masked by condensation and mixing. Here, based on geochronological dating of four bivalve species, carbonate production during the Holocene is assessed in the Gulf of Trieste, where algal and seagrass habitats underwent a major decline during the 20th century. Assemblages of sand‐dwelling Gouldia minima and opportunistic Corbula gibba are time‐averaged to >1000 years and Corbula gibba shells are older by >2000 years than shells of co‐occurring Gouldia minima. This age difference is driven by temporally disjunct production of two species coupled with decimetre‐scale mixing. Stratigraphic unmixing shows that Corbula gibba declined in abundance during the highstand phase and increased again during the 20th century. In contrast, one of the major contributors to carbonate sands – Gouldia minima – increased in abundance during the highstand phase, but declined to almost zero abundance over the past two centuries. Gouldia minima and herbivorous gastropods associated with macroalgae or seagrasses are abundant in the top‐core increments but are rarely alive. Although Gouldia minima is not limited to vegetated habitats, it is abundant in such habitats elsewhere in the Mediterranean Sea. This live–dead mismatch reflects the difference between highstand baseline communities (with soft‐bottom vegetated zones and hard‐bottom Arca beds) and present‐day oligophotic communities with organic‐loving species. Therefore, the decline in light penetration and the loss of vegetated habitats with high molluscan production traces back to the 19th century. More than 50% of the shells on the sea floor in the Gulf of Trieste reflect inactive production that was sourced by heterozoan carbonate factory in algal or seagrass habitats.  相似文献   

Sedimentary history with biotic reaction in the Middle Permian shelly sequence of the Southern Kitakami Massif,Japan     

YUTA SHIINO  YUTARO SUZUKI  FUMIO KOBAYASHI 《Island Arc》2011,20(2):203-220

The transition of sedimentary environments and their organism‐related responses is exemplified in the active margin setting of the Middle Permian in the Southern Kitakami Massif. The transition in the sedimentary environment began with a shallowing‐upward sequence at an upper slope to an outer shelf depositional setting that was associated with a delta system which transported abundant botanic remains in the Hoso‐o Formation. By contrast, the sediments of the overlying Kamiyasse Formation, the base of which is roughly equivalent to the lowermost Capitanian, were deposited at a lower shoreface to the outer shelf setting, which originated from complex depositional sources, including beach, near shore reef mounds and a nearby independent area of shallow and hard substratum with a considerable difference of depth. This unique depositional setting resulted in the seemingly ‘mixed’ fauna associated with this formation. The depositional environment of the overlying Kurosawa Formation is similar to that of the Hoso‐o Formation, but with far fewer monotonous biotic remains. A comparison of lithological characteristics and fossil remains with those of neighboring regions suggests that the independent mounds were generated as if the talus formed elsewhere so as to provide a large amount of skeletal elements to a deeper basin in the earliest Capitanian. Accordingly, the complex sedimentary setting observed in the Kamiyasse Formation occurs widely throughout the South Kitakami Massif, making possible the ‘mixed’ and seemingly diverse fauna from a mixture of multiple allochthonous origins.  相似文献   

Terrestrial arthropods from the Late Pleistocene of Jamaica: systematics,palaeoecology and taphonomy     

Els Baalbergen  Stephen K. Donovan 《Geological Journal》2013,48(6):628-645

The Red Hills Road Cave, Jamaica, is the most important site for terrestrial arthropods in the post‐Miocene of the Greater Antilles. Its fauna includes millipedes, isopods, crabs and insects, in addition to land snails and vertebrates. Arthropods are preserved in three dimensions and delicate structures such as limbs can be recognized. This unusual preservation was favoured by acidic groundwater rich in dissolved calcium carbonate; periods of high rainfall during which the bottle‐shaped cave was filled with water; and any arthropod washed in would have drowned. The absence of spiders, centipedes and most insects is due to the absence of carbonate in their exoskeletons. Millipedes and isopods possess a potential for preservation by carbonate mineralization that does not occur in other groups; they secrete calcium carbonate in the exoskeleton which hardens the cuticle and is water permeable, bringing about mineral replacement of the original structures. Within the cave, fossil millipede taxa include Rhinocricus sp. or spp., Chondrotropis sp., Caraibodesmus verrucosus (Pocock) and Cyclodesmus sp. cf. C. porcellanus Pocock. The isopod fauna includes Pseudarmadillo sp., Venezillo boonae Van Name, and Philoscia spp. 1 and 2. Crab claws belong to Sesarma sp. cf. S. cookei Hartnoll. Millipedes and isopods are particularly complete, representing drowned individuals fossilized soon after death; land crabs occur as fingers and rare chelae, suggesting that they may be exuviae. Only the most robust parts of insects have been discovered, but are particularly rare, consisting of three taxa of fly puparia and one possible beetle elytra. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献