青海共和盆地达连海晚第四纪高湖面与末次冰消期以来的环境变化

干旱区晚第四纪已有较多高湖面与湖泊演化的报道和研究,对于认识区域环境变化有重要意义,但高湖面出现的时间尚存争议,高分辨率的气候环境记录仍相对缺乏。本文通过青海共和盆地达连海湖岸地貌考察和AMS 14C 年代学研究,讨论达连海古湖晚第四纪高湖面出现的可能时间; 并通过达连海DLH99孔岩芯年代和高分辨率代用指标,讨论高原东北缘末次冰消期以来的气候环境变化。达连海周围存在6级高湖面岸线或台地,14C 测年结果显示,最低的两级湖岸堤形成于全新世,其余湖岸台地年代均老于44cal.kaB.P.,当时在达连海地区形成一个较大的古湖泊。DLH99孔显示达连海近15cal.kaB.P.沉积了40.92m的湖相沉积物,平均沉积速率高达2.7mm/a。孢粉资料揭示出,现代干旱的共和盆地在末次冰消期以来存在两个山地针叶林发育阶段,分别位于末次冰消期和全新世早中期。全新世早中期是适合山地针叶林植被发育的气候最宜期,而晚全新世山地森林植被整体衰退。粒度分析结果显示,达连海全新世低水位时期对应于岩芯中部山地森林植被发育的晚期,出现较强烈干旱事件(岩芯深13～15m段),这种湖泊水位与植被所指示的气候变化不一致现象(即低水位时期盆地内耐旱植物和山地乔木花粉同时增加),可能揭示出干旱区山地与盆地环境对区域气候不同响应。达连海存在的系列高湖面和冰消期以来的完整气候记录,为理解晚第四纪季风边缘区气候变化过程及其机制提供了条件。     

艾比湖区域地表水水化学特征干湿季变化及其控制因素

对2014年艾比湖区域的地表水进行观测和取样,综合运用多元统计、Piper阴阳离子三角图、Gibbs图等方法,对艾比湖区域干湿季地表水化学特征及控制因素进行了分析.结果表明：在湿季5月,Na⁺和Cl^-是占绝对优势的离子,分别占阳离子和阴离子总量的70.34%和52.97%,其次是Mg²⁺和SO₄^2-;在干季10月,Na⁺和Cl^-是占绝对优势的离子,分别占阳离子和阴离子总量的70.57%和66.48%,其次是Mg²⁺和SO₄^2-.进而判断出在湿季,艾比湖区域地表水水化学类型为以碳酸盐岩石和蒸发岩来源为主的HCO₃^--Ca²⁺-Na⁺型;而在干季,艾比湖区域地表水水化学类型为以碳酸盐岩石和蒸发岩来源为主的HCO₃^--Ca²⁺型.此外,探讨了离子控制的因素.就自然因素而言,在干湿季,艾比湖区域地表水化学离子组成受岩石风化作用和蒸发结晶作用的共同影响,大气降水的输入作用十分微弱.就人为因素而言,根据相关研究,干湿季人为活动中的主要因素是人口和地区生产总值,说明该区域受到人为活动的影响.本研究为我国干旱地区对于河水水化学变化、水质特征、水质保护都具有重要的意义.     

赛里木湖沉积物有机质变化特征及其环境信息

在分析赛里木湖湖泊沉积物中氮含量(TN)、有机碳含量(TOC)及其碳同位素(δ~(13)C_(org))以及色素等指标的变化特征的基础上,结合沉积物中有机指标的环境意义的探讨,揭示了新疆赛里木湖湖泊沉积物中有机质所蕴含的环境信息.赛里木湖沉积物中总有机碳含量、总氮含量的变化反映了流域初级生产力的变化,沉积物色素变化是有机质保存条件的指标,间接指示了湖泊-流域水热配置环境.有机碳同位素(δ~(13)C_(org))反映了湖泊内外源的混合信息.结合有序样品聚类分析方法,可以将赛里木湖近代环境划分为四大发展阶段:1、各有机指标相对稳定;2、各有机指标明显波动;3、各有机指标显著增加;4、各有机指标快速增加.     

青海省锡铁山矿区外围异常成矿潜力分析

锡铁山铅锌矿是中国目前铅锌储量最大的矿床。但是由于该区外围地势险要,地形复杂,国内对其外围成矿潜力的研究并不是很多。本次对该矿床外围进行了740 km2面积的1∶5万水系沉积物测量及2053 km2面积的1∶5万高精度磁法测量,最终圈定化探异常18处,物探异常28处。通过后期异常查证工作,笔者对这些异常区的成矿潜力做了具体分析,从中优选出了小柴旦湖南、柳园沟、向南沟、锡铁山站南4处成矿有利靶区。     

青海西部尕斯库勒盐湖沉积物中铀和钍地球化学特征探讨

文章以柴达木盆地西部尕斯库勒盐湖沉积物为研究对象,通过对钻孔沉积物和地表沉积物中铀和钍含量的研究,探讨了盐湖沉积物中铀和钍的地球化学特征。分析表明,钻孔沉积物中铀和钍之间存在明显的正相关关系。在横向上,随地表取样点逐渐远离湖表卤水,沉积物中铀和钍的含量先增高后又急剧降低,且受补给水铀含量影响大;在纵向上,同一个晶间卤水层或者碎屑物沉积层内铀含量垂直分异明显,铀含量随深度增加而递增。就沉积物中铀和钍的赋存形式而言,2/3的铀被黏土质点吸附,1/3的铀夹杂在盐类矿物中;而90%以上的钍被黏土质点吸附,10%以下的钍夹杂在盐类矿物中。干盐滩中毛细蒸发和淋滤等化学沉积分异作用造成盐湖沉积中心的沉积物铀含量相对较高。     

浙江省千岛湖西部地区旅游资源功能分类及开发建议

以１∶５万区域地质调查资料为基础，详细论述了千岛湖西部旅游资源的特点，据其功能划分为水文景观、生物景观、地学景观、地史遗迹、休闲渡假、人文景观和土特产品７大类，并对不同类型的旅游资源提出了开发建议     

Screening Effect of the Diffusive Boundary Layer in Sediments of Lake Aha in the Suburbs of Guiyang City,Guizhou Province

The redox cycle of iron and manganese is a major geochemica process at the boundary layers of lake sediments.Lake Aha,which lies in the suburbs of Guiyang City,Guizhou Province,China,is a medium-sized artificial reservoir with seasonally anoxic hypolimnion,Long-term sedimentary accumulation of iron and manganese resulted in their enrichment in the upper sediments,In the anoxic season,Fe^2 and Mn^2 ,formed by diological oxidation,would diffuse up to overlying waters from sediments.However,the concentration of oxidation,would diffuse up to overlying waters from sediments,However,the concentration of Fe^2 increased later and decreased earlier than that of Mn^2 .Generally,sulfate reduction occurred at 6 cm below the sediment-water interface.Whereas,in the anoxic season.the reduction reached upper sediments,inhibiting the release of Fe^2 ,The Fe concentration of anoxic water is quickly decreased from high to low as a result of reduction of the suplhur system.     

Holocene lake stages and thermokarst dynamics in a discontinuous permafrost affected region,north-eastern Tibetan Plateau

Sediments of a thermokarst system on the north-eastern Tibetan Plateau were studied to infer changes in the lacustrine depositional environment related to climatic changes since the early Holocene. The thermokarst pond with a length of 360 m is situated in a 14.5 × 6 km tectonically unaffected intermontane basin, which is underlain by discontinuous permafrost.A lake sediment core and bankside lacustrine onshore deposits were analysed. Additionally, fossil lake sediments were investigated, which document a former lake-level high stand. The sediments are mainly composed of marls with variable amounts of silt carbonate micrite, and organic matter.On the basis of sedimentological (grain size data), geochemical (XRF), mineralogical (XRD) and micropaleontological data (ostracods and chironomide assemblages) a reconstruction of a paleolake environment was achieved.Lacustrine sediments with endogenic carbonate precipitation suggest a lacustrine environment since at least 19.0 cal ka BP. However, because of relocation and reworking processes in the lake, the sediments did not provide distinct information about the ultimate formation of the lake. The high amount of endogenic carbonate suggests prolonged still-water conditions at about 9.3 cal ka BP. Ostracod shells and chironomid head capsules in fossil lake sediments indicate at least one former lake-level high stand, which were developed between the early and middle Holocene. From the late Holocene the area was possibly characterized by a lake-level decline, documented by a hiatus between lacustrine sediments and a reworked loess or loess-like horizon. After the lake-level decline and the following warming period, the area was affected by thermally-induced subsidence and a re-flooding of the basin because of thawing permafrost.     

Diatoms and ostracods as mid-Holocene palaeoenvironmental indicators,North Stromatolite Lake,Coorong National Park,South Australia ∗

The Holocene carbonate sequence of perennial North Stromatolite Lake, located adjacent to the Coorong Lagoon near Salt Creek, South Australia, includes a prominent sapropelic unit (7 – 12% total organic carbon), in places more than 2 m thick, that was sampled for the purpose of radiocarbon dating and documenting its diatom and ostracod biostratigraphy. The recovered ostracods were also subjected to carbon and oxygen isotopic analysis. The bulk organic matter at the base of the sapropel yielded an uncalibrated ¹⁴C age of 6080 ± 60 y BP. Diatoms, where preserved, are almost exclusively benthic. Stratigraphic variation of the proportions of key indicator species in diatom assemblages records a marked oscillation between oligosaline and eusaline conditions in the hypolimnion during deposition of the sapropel. Ostracod carbon isotope data indicate that the lake at this time was eutrophic, thereby enriching the dissolved inorganic carbon of the hypolimnion in ¹³C. However, the observed secular variation in δ¹³C implies a mid-sapropel drop in productivity, caused by a freshening of the lake. Ostracod δ¹⁸O values display an overall increase through the sapropel consistent with the rising salinity of the hypolimnion. The existence of a flourishing benthic ostracod community, together with the valve ornamentation of Osticythere baragwanathi, indicates that the bottom waters were well oxygenated. Thus, anoxia was not a prerequisite for sapropel accumulation. The biostratigraphy and chemostratigraphy of the sapropel concur in suggesting a lack of climatic uniformity during its deposition, a period of ～1200 years. This study therefore highlights the potential of diatoms and ostracods in shallow perennial alkaline lakes along the Coorong coastal plain as proxies for short-term (10² – 10³ years) Holocene palaeoenvironmental change in southeastern Australia.     

新疆东昆仑阿其克库勒湖西缘地区蛇绿岩的确证

新疆东昆仑阿其克库勒湖西缘出露了一套超基性—基性岩。该蛇绿岩的野外地质、岩石学以及岩石化学特征表明它们是由变质橄榄岩和堆晶岩两大单元组成的蛇绿岩 ,是否存在蛇绿岩的其它单元值得进一步研究。同时 ,这些特征表明其与青海东昆仑清水泉蛇绿岩相似 ,指示它们可能为同一洋壳的残余。