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291.
A study of a 1·5 km stretch of a perennial stream in arid northern Oman describes the physical, chemical and faunal characteristics of riffles, runs and pools. Air temperature seems to influence invertebrate recruitment. Flooding is the most important catastrophic event that alters the physical and chemical environment. Current velocity and substrate composition are also probable factors affecting the community structure. All other chemical conditions except nitrate (–N) were significantly similar in all biotopes. Three vertebrate and 33 invertebrate taxa were recorded. The low faunal diversity is a reflection of a physically controlled system. 相似文献
292.
I. C. Potter D. Tiivel F. J. Valesini G. A. Hyndes 《International Journal of Salt Lake Research》1996,5(4):337-358
Leschenault Estuary consists of a large lagoonal-like water body, which opens into Koombana Bay through a short and deep entrance channel at its southern end. Since the only major tributary discharges into the estuary opposite the entrance channel, much of the freshwater discharge in the winter passes directly out to sea. Consequently, during the year of the present study, the mean monthly salinities in the main body of the estuary remained above 20 per mil. This presumably accounts for the fact that the ichthyofaunal composition in the shallows of the estuary did not undergo the type of marked changes that are exhibited in other south-western Australian estuaries, in which salinities often fall below 10 per mil in winter. Despite the maintenance of high salinities in Leschenault Estuary and a close proximity to Koombana Bay, the estuary contained a far greater density and markedly different species composition of fish than that found in that marine embayment. This difference reflected, in part, the high abundance in Leschenault Estuary of some species whose entire life cycle is confined to estuaries,e.g. the atherinidsAtherinosoma elongata andLeptatherina wallacei and the gobiesPseudogobius olorum andAfurcagobius suppositus, and the fact that the juveniles of several marine species,e.g. Hyperlophus vittatus, Sillaginodes punctata, Mugil cephalus andGymnapistes marmoratus were also largely or entirely restricted to the estuary. In contrast,Lesueurina platycephala, which was by far the most abundant species in Koombana Bay, was absent in the estuary. Furthermore, the relatively protected region of Koombana Bay contained a greater density and different composition of fish than the more exposed region of this embayment. This reflected the greater use that was made of the protected region as a nursery area by certain marine species,e.g. Aldrichetta forsten andSillago bassensis. Our data, when taken in conjunction with those collected on the fish fauna in other south-western Australian estuaries, demonstrate that, within this geographical region, some fish species are specifically adapted to the estuarine environment, and that certain marine species apparently have a strong preference for using the highly protected and productive waters of this type of environment as a nursery area. 相似文献
293.
J. Sundaresan 《Environmental Geology》1993,22(3):272-275
Chronic erosion is found along structurally protected beaches of Kerala, viz., Narakkal (17.8 m3/m1) and Munambam (80.36 m3/m–1). The textural characteristics of these beaches are discussed. Observations on the horizontal and vertical distribution of the intertidal fauna of Narakkal beach are presented. The feasibility ofSeaevola taccada as a vegetative beach protective measure is elucidated. The impact of anthropogenically-climatically induced coastal hazards such as sea level rise (SLR) on a typical barrier beach of Kerala is depicted. An alternative beach protective measure to curtail the impact of sea level rise on sandy and atoll beaches of a tropical region is highlighted. 相似文献
294.
狼鳍鱼(Lycoptera)岩层的时代归属 总被引:23,自引:3,他引:23
在燕辽区,狭义的大北沟组产Nestoria-Keratestheria群,Eopa-racypris-Luanpingella-Darwinula组合等化石,白旗组的Rb-Sr等时线年龄为145.2Ma,以及完整的层序关系均证明狼鳍鱼岩层履于上侏罗统之上。热河动物群包括原始Trigonioidids群,Eosestheria群,Lycoptera群…以自身的演化规律阐明其属于白垩系的类群。Eose 相似文献
295.
296.
Stephan Schaal 《东北亚地学研究》2005,8(1):9-14
The paper reports sunthetically the Cocene fauna of the Messel Pit Fossil site of Germany, in detail, including its rich taxanomic composttions, geological and paleogeographic backgroud, and the studying and applying history. 相似文献
297.
Dean R. Lomax Peter Robinson Christopher J. Cleal Alistair Bowden Nigel R. Larkin 《Geological Journal》2016,51(1):42-50
A new fossil‐bearing, Upper Carboniferous (lower Westphalian) locality in Doncaster, South Yorkshire, UK, is reported and an account of the fossils is presented. The diverse flora and fauna consists of plants, bivalves, arthropods (primarily xiphosurans), tentaculitids (microconchids), fish scales, shark egg capsules and coprolites. Fossils are preserved in siderite nodules and shales, and display excellent preservation and detail. Previous collecting of Carboniferous fossils in the Doncaster area has been minimal. The discovery of this locality addresses this deficit and is of further importance as such localities in the UK are diminishing in number with the cessation of coal‐mining and the reclamation of mine dumps, further demonstrating the importance and recognition of the Edlington site. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
298.
通过对山东省淄博地区太原组小有孔虫类动物群的系统研究,共鉴定出小有孔虫11属22种及部分未定种。根据有孔 虫类化石在地层中的分布和垂向变化规律,建立了两个小有孔虫化石组合带:IBradyina-Plectogyra 组合与IITetrataxisNodosaria-Palaeotextularia 组合。通过与邻区及华中华北其它地区的有孔虫进行对比,并结合前人对本区 类化石的研究结 果,确定了各组合带的地质时代:太原组小有孔虫动物群第I组合带地质时代归为晚石炭世,第II组合带地质时代归为早二 叠世,其层位相当于山东地区太原组 类Pseudoschwagerina带之底。 相似文献
299.
文章记述了甘肃临夏盆地晚中新世杨家山动物群的瞪羚(Gazella)化石,将临夏材料归为保德瞪羚(Gazella paotehensis)、高氏瞪羚相似种(G.cf.gaudryi)和瞪羚未定种(G.sp.).G.paotehensis为有效种,与G.gaudryi区别在于G.paotehensis两角心分散度大,表面发育较深纵沟;与G.dorcadoides区别在于G.paotehensis角心向后外方伸出角度较高,侧视倾斜度小,脑颅部从额项缝开始呈弧形向后下方弯曲.依据临夏的瞪羚化石组合推测杨家山动物群的生活环境可能为温带开阔草原,有灌木丛为典型食叶者食用.依据脑颅轮廓,G.paotehensis应归入短头型,验证了G.paotehensis可能是G.blacki祖先的观点. 相似文献
300.
继2000年在南京汤山直立人地点葫芦洞附近的驼子洞堆积(32°03′17.1″N,119°01 ′57.6″E)中发现了大量的哺乳动物化石后,2007年在驼子洞又进行了新的发掘工作,出土了不少新材料.根据对新材料的研究将若干种类的分类位置做了修订,其中将原来鉴定为短角丽牛相似种(Leptobos cf.L.brevicornis)的标本厘定为粗壮丽牛(Leptobos (Smertiobos) crassus).通过对驼子洞动物群性质的综合比较,发现驼子洞动物群的组成成分与安徽繁昌人字洞动物群和重庆巫山龙骨坡动物群最接近.驼子洞动物群的组成具有南、北方类型混合的特点,应该属于过渡型动物群,但以具北方特色的成员偏多,说明在早更新世期间有北方的部分种类向南扩散的事件,范围到达南京一带.这一扩散事件可能与气候变化有关.驼子洞动物群指示在早更新世时期江宁一带的地貌特征与现在的差别不大,气候潮湿,但气温可能比现在的低. 相似文献