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341.
本文依据新发现的晚更新世洞穴地层剖面,进行了年代学及哺乳动物化石方面的研究。年代学综合测定结果为距今12~1.9万年,这是周口店地区迄今发现的最为完整的晚更新世洞穴地层剖面,根据堆积物中所含的哺乳动物化石特征,进行了生态、种类方面的研究,建立了一个新的哺乳动物群─—东岭子动物群。 相似文献
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研究了西藏吉隆—沃马盆地龙骨沟剖面新近纪沉积环境,作了古地磁年代学研究,认为喜马拉雅山北坡新生代断陷盆地发育始于7.2MaB.P., 3.2MaB.P.湖盆萎缩消亡,标志着喜马拉雅山地区在7.2MaB.P.和3.2MaB.P.发生过强烈的隆升事件.沃马盆地龙骨沟剖面所含三趾马动物群化石层年龄大约为7.0~6.7MaB.P.,隐示着此时青藏地区三趾马生活区与当时的华北平原三趾马生活区有着大体相当的地理、气候环境.之后由于喜马拉雅山持续抬升,断陷盆地下沉,并在5.9~3.6MaB.P.期间湖盆面积最为广阔.青藏高原抬升而华北平原沉降, 中国西部地区地形高于东部,东西部气候环境发生重大差异.3.6MaB.P.由于青藏地区持续强烈隆升,西部地区河流切穿古老湖盆,3.20MaB.P.吉隆—沃马湖盆萎缩,于1.7MaB.P.逐渐消失,进入侵蚀切割阶段. 相似文献
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黔西赫章志留纪晚期小莱采贝动物群的发现及其古地理意义 总被引:1,自引:0,他引:1
志留系在黔西的分布范围很小,已知仅限于赫章县境内。赫章的志留系发育不全,由于缺少古生
物证据,其具体时代长期难以肯定。最近在赫章草子坪志留系中发现腕足动物、三叶虫和双壳类化石群。腕足
类研究结果显示,它应属于小莱采贝动物群(Retziella Fauna) 和新建立的Nikiforovaena Retziella组合。该化石层
下伏紫红色泥岩地层。这段近岸、浅水、杂色碎屑岩层在岩性上与滇东曲靖的关底组类同,可部分对比,推测
其时代为罗德洛世晚期(Late Ludlow),但不宜另立新名,仍称关底组为好。在讨论关底组含义之后,笔者赞同
取消岳家山组的意见。对赫章志留系具体时代的确定使对华南志留纪晚期岩相古地理的传统认识得到修正,罗
德洛世晚期的海侵从滇东的曲靖地区扩大到黔西的赫章一带。 相似文献
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Zinc in muscle tissue from 28 species of fish, three species of sharks and rays, two species of squid and cuttlefish, and three species of crustacea collected from Cleveland Bay, together with some measurements made on oysters and mangrove flora and fauna are reported. In the fish species the mean Zn concentration in muscle tissue was 4.83 ± 2.82 μg/g wet weight, slightly lower than zinc measurements (7 μg/g wet weight) made in 14 fish species collected from the bay in 1975. Zinc in sharks and rays ranged from 3.5 to 7.2 μg/g wet wt, in squid and cuttlefish 13–16 μg/g wet wt, and in crustacea levels ranged from 14 to 18 μg/g wet wt. Zinc levels in fish varied between species with concentrations well below the ANZECC Maximum Residue Limit of zinc in seafood (150 μg/g wet wt). Although lower zinc concentrations were found in oysters collected from the Townsville Harbour area (2080 μg/g wet wt), compared with previous measurements made 25 years ago at this site, these levels are still above the Maximum Residue Limit for zinc in oysters (1000 μg/g wet wt). Concentrations of zinc in oysters from Orpheus Island (2547 μg/g wet wt), about 74 km away from industrial and urban activity, are also above the safe guideline values. Horseshoe Bay oysters transplanted to Ross Creek accumulated zinc at a rate of about 100 μg/g of oyster tissue per week, suggesting that dissolved zinc levels at this site are elevated, and that oysters rapidly accumulate zinc. Highest concentrations of zinc in mangrove leaves (30–65 μg/g dry wt) occurred in Osbornia octodonta, Exocaria agalocha, and Aegialitus annulata, compared with Ceriops tagal, and Avicennia marina (5–10 μg/g dry wt). No significant difference in zinc concentration occurred between leaves and litter fall for most of these species, with the sole exception of Exocaria, which showed almost a twofold increase in concentration. In seven species of mangrove fauna levels of zinc were very uniform and close to 50 μg/g (dry wt) Telescopium telescopium from the mouth of the Ross Estuary was the exception with levels at 400 μg/g (dry wt). 相似文献
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Many subsurface waters are considered groundwater but are influenced in shallow depths by hyporheic, parafluvial and/or soil interception water to such a degree that groundwater fauna (stygofauna) communities may be significantly altered. Recharge, even if spatially and temporally distinct, delivers input of dissolved oxygen, organic matter (OM), and nutrients that caters sustainably for ubiquists such as stygophiles and hyporheic fauna, but renders the life of uncompetitive stygobites difficult or impossible. The impact of recharge at shallow groundwater thus needs to be taken into account when determining groundwater fauna reference communities and when evaluating monitoring studies.One of the main characteristics of groundwater is low OM concentration. In contrast, high OM concentrations are typical of hyporheic or parafluvial waters, which are enriched by OM from the river, the riparian soils and from interflow, and which contribute significantly to river OM balance. Consequently, for ecological studies on subsurface waters, both the origin of the water and OM, and the intensity of surface water interactions should be considered. Here, we discuss how groundwater spatial and temporal heterogeneity translates into faunal distribution patterns. In terms of the origin of water and OM, and from an ecological point of view, we need to distinguish between (i) shallow groundwater characterized by infiltrating precipitation and soil recharge, (ii) shallow groundwater interacting with surface water bodies such as continuously flowing and ephemeral streams and rivers, and (iii) “old” groundwater which has no recent connections to the surface and is thus largely secluded from input of nutrients and carbon. Water in the first two groups is characterized by high amounts of OM of varying quality, while water in the third group is characterized by low amounts of low quality OM. Consequently, stygophiles dominate in groups 1 and 2, with hyporheic fauna taking up a considerable proportion in group 2, while stygobites only dominate in group 3. Thus, for studies aiming to assess impacts on groundwater, only sampling sites of the third group should be used for reference sites as these are the most likely sites to have little surface impact and a stygofauna representative of the deeper aquifer. 相似文献
347.
喀斯特高原不同植被演替阶段土壤动物群落特征 总被引:3,自引:0,他引:3
选择贵州喀斯特高原三个典型地貌单元作为研究区,于2009-05对不同植被演替阶段的土壤动物群落进行研究.共获土壤动物3 992只,隶属于5门10纲26目,共31个类群,优势类群为弹尾目(Collembola)、甲螨亚目(Oribatida)、中气门亚目(Mesostigmata);常见类群为前气门亚目(Prostigmata)、膜翅目(Hymenoptera)、鞘翅目(Coleoptera)、半翅目(Hemiptera )、近孔寡毛目(Plesiopora)、双翅目(Diptera)、双尾目(Diplura).研究结果表明,随着喀斯特植被的不断退化,土壤动物数量不断减少,表现为林地>灌丛>草地>石漠化地;类群数亦呈减少趋势.各演替阶段土壤动物表聚性明显,但人为干扰(如翻耕等)可导致土壤动物出现逆分布现象.土壤动物多样性分析表明,中小型土壤动物的多样性指数从林地到石漠化地逐渐减小. 相似文献
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