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1.
我国早期后生动物群的特异埋藏机理探讨 总被引：6，自引：3，他引：3
通过对早期后生动物群产出层位的沉积特征、沉积层序和化石埋藏特征的研究,认为在海湾和局限海环境,早期后生动物群往往产于海侵体系中,而陆棚环境则保存在低水位体系;同时提出了两种早期后生动物群埋藏保存机理,一种是沉积事件（风暴流或浊流）破坏了生物生态环境,使生活在正常环境中的生物大量死亡,并被快速埋藏保存;另一种是海平面脉动引起环境变化,使早期后生动物死亡,在还原环境下埋藏保存。因此,认为海平面变化与早期后生动物群的埋藏保存有着密切关系。在提出两种早期后生动物群特异埋藏机理的基础上,并认为由前寒武纪至寒武纪,只要沉积环境、沉积序列类似,就有可能发现早期后生动物群,这对寻找新的早期后生动物群具有重要的指导意义。 相似文献
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衡阳市郊五马归槽始新世鱼化石保存在黑色湖相纹层中。根据纹层序列的对比,发现该地的鱼化石均为同一层位;根据鱼化石在纹层序列中的具体位置及鱼化石的保存状况,笔者推测鱼群的死亡并非由于季节更替,而是由气候干旱引起的湖水盐度升高所控制;黑白纹层的变化是由大气降雨所致。 相似文献
3.
《地学前缘》2017,(2):286-291
随着分子生物学技术的发展,DNA技术的应用逐渐从生物学研究拓展到进化、环境和气候变化等研究领域。因为DNA容易受到水解、氧化、紫外辐射、酶解等过程的破坏,所以人们认为DNA很容易降解,保存时间不长,但是近年来的研究成果显示,古生物和古人类的化石或骨骼、冻土、湖泊海洋沉积物等样品中包含已保存数千年甚至长达数百万年以来的古DNA。古DNA作为重要的信息载体,可以诠释人类、动植物和微生物进化和迁移过程及它们对环境和气候变化的响应。反过来,古DNA在古环境、古气候重建方面也起着重要作用,沉积物样品的古DNA往往保存了历史时期的水体和水体周围环境以及气候变化等信息。通过对沉积物中古DNA的研究,可以获得历史时期的水生生物(包括藻类、水生动植物等)的群落演化,和水体周围岸基生活的动植物群落(植物落叶、动物毛发冲带到水体并沉积下来)演替,进而反演水体和水体周围气候环境以及气候变化信息。通过研究古人类和动物化石中保存的DNA,可以探讨人类的迁徙和进化过程,溯源家畜的驯化历史。本文将介绍环境古DNA的保存和可靠性评价,重点探讨古DNA在古生态以及古环境、古气候重建研究中的优势及应用,并展望古DNA在生物进化和环境研究等领域的应用前景。 相似文献
4.
在内蒙古自治区白彦花车站附近分布的20余个坑塘和1个较大的湖泊中,生活着大量的叶肢介。对该地区叶肢介的生活习性（游动、觅食、交配等）和生存环境（坑塘的大小、水温、水体的pH值和气温）进行的调查显示：叶肢介一般活动在浅水水域,如坑塘和湖泊边缘的浅水地带;他们的游动非常缓慢,大约1cm/s;当他们交配时就停留在某处,雄性用附肢拨动含有其精子的水流,使其流向雌性的壳内（即雌性壳体与软体之间）,以使卵子受精。这些事实表明,叶肢介只能适应于静水或弱流水环境。叶肢介的现代环境与古环境的对比研究显示两者是非常相似的,因此,现生叶肢介生态和环境的研究对恢复他们的古生态与古环境具有重要的意义。 相似文献
5.
粪化石是一类重要的遗迹化石,其内含物常保存被捕食生物的残余及一些微生物、软组织甚至古DNA信息,对解读地质历史时期的湖泊生态信息有重要意义。鄂尔多斯盆地南部铜川地区三叠系延长组长7段下部页岩的鱼粪石,其为略扁平的纺锤形化石,尖而薄,表面有明显的螺旋纹。观察粪化石的内含物情况,发现其主要由未完全消化的动植物残体组成,包括鱼鳞、骨骼碎片,以及以含磷白云岩为生长基的大量矿物聚集体。鱼粪化石形成于开放型淡水湖泊中的半深湖—深湖区,大部分保存完好,属于典型的原地埋葬。该鱼粪的生物源为一种大型的、鱼肠内具有较多螺旋瓣的肉食性鱼类。晚三叠世湖泊中出现了复杂的多层营养系统,主要由生产者、消费者构成,食物链较为复杂。该研究成果表明经历二叠纪末生物大灭绝的晚三叠世多层级营养湖泊生态系统已经基本恢复。另外,微生物的参与及泥质含量较高的厌氧环境使得粪化石保存完好,可为恢复和重建晚三叠世卡尼期湖泊生态系统提供重要依据。 相似文献
6.
豫西济源西部铝土矿成矿地质环境 总被引：17，自引：0，他引：17
文章在对含矿岩系岩石组合、地球化学分析的基础上,认为矿区铝土矿形成于华北地块从早古生代准平原状态向晚古生代陆表浅海过渡时期,早期海侵之后的陆地湖泊环境中.被碳酸盐岩覆盖、较小地形差异的陆地准平原状态,湿热的气候,繁茂的植物使得岩溶湖泊成为铝土矿富集和保存的有利场所. 相似文献
7.
古湖泊学研究——以桦甸断陷盆地为例 总被引：1，自引：0，他引：1
古湖泊学是研究湖泊系统历史演变的科学,是一门综合性很强的地球科学。本文综述了古湖泊学的定义、研究现状及常用的研究方法,并以吉林桦甸古近纪断陷含油页岩湖盆为例进行了应用。桦甸盆地为小型半地堑盆地,盆地南缘F1断裂控制了古近系湖泊演化特征。桦甸盆地富含油页岩资源,具有开展古湖泊学研究的优势条件。桦甸油页岩具明显的黑白相间的双层结构特征,有机质条带和陆源碎屑颗粒呈现良好的韵律互层,有机质呈现褐色或黑色条带,夹杂石英、长石颗粒的粘土矿物呈白色条带。根据泥岩和油页岩的有机碳含量垂向变化特征,桦甸组古湖泊生产力演化趋势为:中部含油页岩段＞上部含煤段＞下部含黄铁矿段,反映油页岩沉积时,湖盆古湖泊生产力最高。根据油页岩岩石学特征、V/(V＋Ni)、Sr/Ba和B/Ga等元素比值分析,中部含油页岩段时期,表现出一种淡水与半咸水—咸水交替变化的沉积演变过程,可以形成一定程度的盐度分层,使底层水处于缺氧环境,有利于有机质的保存。随着古湖泊学的不断发展,它已经在油气资源勘探开发及全球环境与气候变化等领域发挥了重要作用,但仍存在一些理论及方法问题需要湖泊地质工作者的不断努力与探索。 相似文献
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9.
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
10.
晚震旦世陡山沱期后生生物群的古生态环境探讨 总被引：1，自引：0，他引：1
杨瑞东 《沉积与特提斯地质》1999,19(5):53-59
早期后生生物群是当前古生物学研究热点之一。我国上扬子区的庙河生物群和瓮安生物群是震旦纪的重要生物群,而生物群是怎样繁盛和埋藏保存是研究早期后生生物群的一个重要方面。作者研究认为翁安生物群是由于洋流上升提供了大量的ＳｉＯ２和Ｐ２Ｏ５等养分,使生物在台地边缘大规模繁盛,其海水由于富ＳｉＯ２和Ｐ２Ｏ５所引起强烈的磷酸岩化及硅化作用,使大量的生物尸体被快速矿化,形成具有抗水动力强的骨架,避免水动力和氧化作 相似文献
11.
《Geochimica et cosmochimica acta》1999,63(7-8):1083-1095
Carcasses of the shrimp Crangon crangon were incubated in a marine medium under oxic conditions at 15°C which was inoculated with a consortium of sulfate-reducing, sulfide-oxidizing, and fermentative bacteria. These standard conditions were varied by adding sediment, omitting sulfate, adding glucose, omitting the inoculum, adding phosphate, and enhancing the buffer capacity. The chemical gradients generated by decay were monitored over a period of 29 days with O2, pH- and sulfide-microelectrodes. In most of the experiments oxygen was depleted, pH decreased and sulfide accumulated around the carcass within a week, creating steep chemical gradients, and decay was predominantly anaerobic. By 29 days maximum change in O2 concentration was from around 200 to 0 μM, in pH from 7.5 to 6.2, and in sulphide concentration from 0 to 5.6 mM. Although weight loss and general decay were least when only indigenous bacteria were present, only CaCO3 crystal bundles formed and there was no soft tissue preservation. In contrast, where decay and weight loss were more extensive anaerobic sulphate reduction was intense, pH decreased markedly, and some muscle tissue was replicated in CaPO4. The pH close to the decaying carcass seemed to determine whether CaCO3 or CaPO4 formed. Paradoxically, the exceptional preservation of soft-tissues in fossils requires elevated rather than restricted microbial activity as this leads to anaerobically driven authigenic mineral formation. 相似文献
12.
试论动物非矿化组织的保存 总被引：3，自引：0，他引：3
动物非矿物化组织在特异埋葬条件下可保存为化石。缺氧和快速埋葬有利于非矿化组织的保存，但不能阻止微生物的破坏作用。无菌环境下可保存软躯体组织，但在构造变动和古气候变迁等因素的影响下会彻底破坏，不可能在地质历史时期长期存在。最稳定的保存形式是与成岩作用有关的保存类型和以碳化有机质薄膜形式的保存类型。与动物非矿化组织保存有关的常见成岩自生矿物有磷酸盐矿物、碳酸盐矿物和黄铁矿等。其中，磷酸盐矿物在成岩作用过程中结晶最早，可以保存动物的微细构造。这些矿物可以矿化交代动物的肉质和角质使其成为矿化实体；也可以呈假形、铸型或铸模等形式保存。布尔吉斯页岩保存类型中，非矿化组织以碳化有机质薄膜或含水的颧硅酸盐矿物两种形式保存。前可能与粘土矿物吸附有机质、阻止酶的降解作用有关，后可能由自生粘土矿物的交代作用造成。 相似文献
13.
Victor Hugo Dominato Dimila Mothé Rafael Costa da Silva Leonardo dos Santos Avilla 《Journal of South American Earth Sciences》2011,31(2-3):171-177
This study reports implications of different tooth marks left by carnivorous mammals on long bones of Haplomastodon waringi from the Quaternary of Águas de Araxá, Minas Gerais, Brazil. Analyses of gnawing damage by ursids, felids, and canids have shown that these groups produce pits on bone surfaces when the gnawing is superficial, and punctures more often when the prey is intensely consumed. Scratches or scoring marks are most often associated with gnawing by canids, which may spend a long time gnawing the bones, leading to differential tooth marking. The gomphothere bones at Águas de Araxá did not result from predation, but are a consequence of a local mass mortality in a period of low environmental humidity, with little water and a scarcity of food. Canids frequently act as opportunistic scavengers during periods when herbivores face food shortages. Previous studies of necrophagous dermestid larvae indicate that the gomphothere carcasses of Águas de Araxá were exposed for a long period of time after death. These insects are the last consumers of a carcass because they act only when the body fat is completely lost. Thus, the gomphothere carcasses at Águas de Araxá suffered canid necrophagy in the early stages of decomposition, possibly during a drought period. Thereafter, the gomphothere carcasses would have been exposed for a period about 230 days until the final burial event. 相似文献
14.
《Chemical Geology》2002,182(2-4):461-472
Models proposed for authigenic pyritization in the literature provide good indicators of the effect of very high concentrations of available iron on decaying organisms; however, the impact of lower concentrations of iron on an actively decaying system is not so well characterised. Gel-stabilised systems are used to model the effect of extremes of iron concentration on the precipitation of pyrite and the process of organic matter preservation. The experiments show the effect of sulphate reduction decay in an environment where iron is limited or dispersed, and in iron-rich environment where diffusion is limited. The formation of discrete sulphide bands in experiments where iron is limited indicates that negative feedback, or Liesegang, reactions play a role in the development of gaps between sites of organic matter preservation and pyrite precipitation, providing a mechanism for the formation of pyrite halos, concretion rims and overgrowths. In iron-rich environments, pyrite formation is confined to the decaying organism, and the Liesegang effect is limited due to the restricted diffusion of dissolved sulphide. 相似文献
15.
Kenneth F. Rijsdijk Julian P. Hume Frans Bunnik F.B. Vincent Florens Claudia Baider Beth Shapiro Johannes van der Plicht Anwar Janoo Owen Griffiths Lars W. van den Hoek Ostende Holger Cremer Tamara Vernimmen Perry G.B. De Louw Assenjee Bholah Salem Saumtally Nicolas Porch James Haile Mike Buckley Matthew Collins Edmund Gittenberger 《Quaternary Science Reviews》2009,28(1-2):14-24
Although the recent history of human colonisation and impact on Mauritius is well documented, virtually no records of the pre-human native ecosystem exist, making it difficult to assess the magnitude of the changes brought about by human settlement. Here, we describe a 4000-year-old fossil bed at Mare aux Songes (MAS) in south-eastern Mauritius that contains both macrofossils (vertebrate fauna, gastropods, insects and flora) and microfossils (diatoms, pollen, spores and phytoliths). With >250 bone fragments/m2 and comprising 50% of all known extinct and extant vertebrate species (ns = 44) of Mauritius, MAS may constitute the first Holocene vertebrate bone Concentration-Lagerstätte identified on an oceanic volcanic island. Fossil remains are dominated by extinct giant tortoises Cylindraspis spp. (63%), passerines (～10%), small bats (7.8%) and dodo Raphus cucullatus (7.1%). Twelve radiocarbon ages [four of them duplicates] from bones and other material suggest that accumulation of fossils took place within several centuries. An exceptional combination of abiotic conditions led to preservation of bones, bone collagen, plant tissue and microfossils. Although bone collagen is well preserved, DNA from dodo and other Mauritian vertebrates has proved difficult. Our analysis suggests that from ca 4000 years ago (4 ka), rising sea levels created a freshwater lake at MAS, generating an oasis in an otherwise dry environment which attracted a diverse vertebrate fauna. Subsequent aridification in the south-west Indian Ocean region may have increased carcass accumulation during droughts, contributing to the exceptionally high fossil concentration. The abundance of floral and faunal remains in this Lagerstätte offers a unique opportunity to reconstruct a pre-human ecosystem on an oceanic island, providing a key foundation for assessing the vulnerability of island ecosystems to human impact. 相似文献
16.
The Cerro del Pueblo Formation in the state of Coahuila, Mexico is becoming recognized worldwide due to its abundant and diverse fossil material. While most previous paleontological work from this rock unit has been directed towards taxonomic investigation, this study is directed towards the taphonomy of a “duck-billed” dinosaur (Ornithischia: Hadrosauridae). The hadrosaur skeleton is represented by several skull bones, vertebrae and ribs, a scapula, pubis, and various appendicular elements. The following taphonomic parameters were considered: (1) bone frequency; (2) hydraulic equivalence; (3) degree of bone articulation; (4) abrasion; (5) weathering; (6) breakage; (7) tooth marks; and (8) trampling activities. The low degree of weathering and abrasion suggests that the specimen experienced a short time of subaerial exposure and underwent a short transportation distance before deposition. Burial occurred within a perimarine lagoonal environment. Furthermore, the lack of hydraulic equivalence with the rock matrix, a high degree of disarticulation and a chaotic distribution of the bones in the fossiliferous bed, suggest that it was transported as a “bloated carcass”. The finding of distinct types of tooth marks evidence some sort of predator/scavenging activities on the specimen. Finally, an almost vertical orientation of various bones and the presence of spiral fractures may indicate that these elements were trampled by other animals. 相似文献
17.
Richard G. Klein 《Quaternary Research》1978,10(1):69-83
The Cutting 10 site at Elandsfontein (Hopefield), southwestern Cape Province, South Africa, is one of only three sites in southern Africa where bones and Acheulean artifacts have been documented together in primary or near primary context and the only such site where the association is in the open air. The Cutting 10 bones belong to a minimum of 15 mammalian species, which together suggest both a mid-Pleistocene age for the site and a vegetational setting in which grasses played a much more important role than they did historically. The absence of evidence for hearths, windbreaks, and other features, the composition of the artifact assemblage, the relatively sparse scatter of bones and artifacts, the relatively high bone to artifact ratio, the species composition of the fauna, and the numbers of different kinds of skeletal elements represented all indicate that the Cutting 10 occurrence was more a butchering site than a campsite. Although people are probably responsible for most of the bones, some of them probably come from animals that were killed by large carnivores or that died naturally. 相似文献
18.
俄罗斯勘察加半岛热泉的地球化学和微生物学 总被引：3，自引：0，他引：3
勘察加半岛位于欧洲板块、北美板块和太平洋板块交汇的过渡带上,是世界火山活动最活跃的地区之一.其众多的热液系统不断的向地表释放地热气体和流体.以N2和CO2为主的地热气体也经常含有高浓度的H2,CH4和H2S.大气水和熔岩水构成了勘察加热泉水的主要源,水体温度从20
℃到＞90 ℃不等.水化学性质变化同样显著,pH范围从3.1到9.8.热泉水溶解盐以氯化钠为主,同时包括K+,H3BO3,H4SiO4,Ca2+和SO42-等其他多种溶解组分.此区域也有以直链烷烃为主的石油形成.从勘察加的热泉系统中已分离出至少24种嗜热微生物.尽管其中大多数是异养微生物,但根据其生存环境的特点,自养微生物在热泉系统中可能同样很多.这些微生物对碳、硫和铁在热液系统中的生物地球化学循环有着非常重要的作用.目前,非培养的方法和生物定量的手段已用来研究勘察加热泉中微生物生态及其所具有的生物地球化学功能. 相似文献
19.
甘肃武都龙家沟三趾马动物群化石的聚集特点 总被引：1，自引：0，他引：1
龙家沟三趾马动物群中不同类型、不同大小动物的保存量及保存部位相差很大，实际保存量仅为理论保存量的６%左右，其化石材料明显经过水流的搬运作用。搬运过程中的分选作用是造成材料流失的主要原因，其中小型动物的流失最为明显。这是古生态恢复及古环境再造值得注意的问题。 相似文献