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  

黄冰  戎嘉余  王怿 《古地理学报》2011,13(1):30-36

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   

内蒙古锡林浩特二叠系哲斯组腕足动物群特征及其意义   总被引：1，自引：0，他引：1  

杨兵  张雄华  杨欣杰  夏浩东 《地质通报》2017,36(10):1683-1690

内蒙古锡林浩特克什克腾旗哈尔呼舒剖面哲斯组灰岩中发现了大量腕足化石,经鉴定计有22属42种,以长身贝亚目和石燕贝亚目为主,化石组合面貌具有典型的哲斯动物群特征。根据其与邻区的腕足生物地层对比,确定该腕足生物群时代为中二叠世Wordian期。哲斯动物群中凉水型分子共计10属26种,约占种级总量的61.9%,暖水型分子仅1种,约占种级总量的2.4%,体现了典型的凉水型动物群特征。古生物地理区划属于北方生物地理大区。此外,哲斯组碳酸盐岩中颗粒组合属于苔藓虫-棘皮动物-腕足动物组合,代表凉水沉积环境,也印证了哲斯动物群的凉水型特征。  相似文献   

What is groundwater and what does this mean to fauna? - An opinion     

Susanne I. Schmidt  Hans Jürgen Hahn 《Limnologica》2012,42(1):1-6

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   

青海湖地区环境变化对动物区系演变影响的探讨   总被引：6，自引：0，他引：6  

陈涛  任杰  王恒山  马世震  李幸福 《湖泊科学》1992,4(4):41-47

青海湖地区近百年来由于气候干暖化趋势增强,湖周植被、土地退化,人类经济活动加剧,湖区青藏高原动物成分的种类和数量减少,但蒙新及华北动物区系成分则有增加趋势,致使该区动物区系成分发生显著变化。从青海湖地区动物区系形成来看,决定动物区系演变的原因主要是气候、生物等生态因子的综合作用,人为因子影响仅在近30年来才日益突出。  相似文献