Prediction of episodic acidification in North‐eastern USA: an empirical/mechanistic approach

Observations from the US Environmental Protection Agency's Episodic Response Project (ERP) in the North‐eastern United States are used to develop an empirical/mechanistic scheme for prediction of the minimum values of acid neutralizing capacity (ANC) during episodes. An acidification episode is defined as a hydrological event during which ANC decreases. The pre‐episode ANC is used to index the antecedent condition, and the stream flow increase reflects how much the relative contributions of sources of waters change during the episode. As much as 92% of the total variation in the minimum ANC in individual catchments can be explained (with levels of explanation >70% for nine of the 13 streams) by a multiple linear regression model that includes pre‐episode ANC and change in discharge as independent variables. The predictive scheme is demonstrated to be regionally robust, with the regional variance explained ranging from 77 to 83%. The scheme is not successful for each ERP stream, and reasons are suggested for the individual failures. The potential for applying the predictive scheme to other watersheds is demonstrated by testing the model with data from the Panola Mountain Research Watershed in the South‐eastern United States, where the variance explained by the model was 74%. The model can also be utilized to assess ‘chemically new’ and ‘chemically old’ water sources during acidification episodes. Copyright © 1999 John Wiley & Sons, Ltd.     

Middle pleistocene interglacial sediments at Tye green,Stansted Airport,Essex, England

Interglacial lake deposits at Tye Green, Stansted, resting on unweathered till and overlain by a weathered diamicton are correlated with the temperate Hoxnian Stage. The sediments represent the infilling of an isolated kettle-hole type of lake basin formed at the end of the cold Anglian Stage. Through the temperate period this basin was infilled by inorganic and organic sediments that record the development and decline of deciduous forest. Later periglacial conditions are indicated by the final infilling of the basin by reworked till. The sedimentary sequence and vegetational development recorded in the sediments at Tye Green are compared with other Hoxnian sites in eastern England. Changes in deposition rates are interpreted as representing water-table fluctuations resulting from changes in precipitation. The deposits at Tye Green provide a useful stratigraphical marker in the glacial sequence of the district. Copyright © 1999 John Wiley & Sons, Ltd.     

新疆东昆仑西段黄沙河地区托库孜达坂组地质特征及沉积环境分析

黄沙河地区位于新疆东昆仑西段南缘,属于昆南增生杂岩带,研究区内出露大面积下石炭统托库孜达坂组,为了厘定区内托库孜达坂组时代并对其沉积环境进行分析,本文在详细的野外地质调查基础上,通过地层层序学、岩石学及古生物学研究,将新疆东昆仑西段黄沙河地区托库孜达坂组分为下段碎屑岩段和上段碳酸盐岩段,将其时代厘定为早石炭世,结合区内碎屑岩粒度特征及放射虫化石特征,确定该套地层的沉积环境为半深海滨浅海环境。     

藏东南鲁朗-通麦崩塌滑坡孕灾地质背景特征研究

藏东南的喜马拉雅东构造结地区作为青藏高原隆升最快的地区之一,其复杂的地质背景条件决定了该区工程地质问题具有复杂性和特殊性,并孕育了多种地质灾害。利用测窗、节理裂隙分期配套等野外调查方法以及遥感影像解译,分析总结了藏东南地区鲁朗至通麦不同区段崩塌滑坡地质灾害的孕灾地质背景,据此将研究区划分为四段,分别为鲁朗-东久段、东久-拉月段、拉月-排龙段、排龙-通麦段,每一区段分别对应了不同的孕灾地质条件特征,由此也决定了区段内崩滑地质灾害的性质、变形破坏模式、规模。相关成果可用于藏东南崩塌滑坡地质灾害的早期识别和风险评价。      

黑龙江省东部早古生代晨明组物源区特征及其构造背景

为揭示黑龙江省东部早古生代晨明组沉积物源区特征及其沉积构造背景,对晨明组进行了地球化学特征研究。结果表明：晨明组岩石样品化学蚀变指数（I_CA）值和斜长石蚀变指数（I_PA）值较低、成分变异指数（I_CV）值中等偏高,指示晨明组沉积物来源于不成熟的物质源区,并经历了较弱的化学风化作用和活动构造背景下的初次循环;LREE富集、HREE稳定和明显的负Eu异常,指示沉积物源区物质具有明显的上地壳特征且沉积物源岩为长英质火成岩;主量、微量和稀土元素特征共同指示晨明组形成于活动大陆边缘环境或大陆岛弧环境。结合前人研究成果,判定晨明组沉积物来源于经历了弱-中等程度化学风化作用的早古生代花岗质岩,沉积构造背景可能为靠近大陆岛弧的活动大陆边缘环境。     

西北地区东部夏季水汽输送特征及其与降水的关系

采用ERA Interim 再分析资料和160 站逐月站点降水资料,运用经验正交函数（EOF）分析、合成分析等方法揭示了西北东部3 个分区的水汽输送的区域气候特征、与降水EOF气候模态相对应的整层水汽输送特征以及降水偏多（少）年的水汽输送异常特征。结果表明：西北地区东部夏季经向水汽输送的大值区处于900 hPa~800 hPa 高度上;纬向水汽输送大值位于700 hPa~500 hPa 高度上。对西北东部降水做EOF 分析,第一模态为全区一致型,与降水相对应的西风影响区主要盛行西风水汽输送,季风边缘区的南部盛行西南风水汽输送;第二模态为东南-西北型,东风、东北风水汽输送流入西北东部地区;第三模态为东北－西南型,西风和西北风水汽输送将水汽带到西风影响区内。     

辽东大石桥组蛇纹石化大理岩中铀矿化特征及形成时代

在辽东大石桥组蛇纹石化大理岩中新发现晶质铀矿矿化现象。晶质铀矿呈角砾状发育在蛇纹石化白云石大理岩中,并叠加有辉钼矿、黄铁矿等矿化。U-Pb同位素年龄测定显示,晶质铀矿形成于1763~1794Ma。EPMA U-Th-Pb化学年龄显示,晶质铀矿形成后经历了1512±20Ma的热事件改造,对应一次岩浆侵入事件。辽东地区经历了古元古代的裂谷拉张、碰撞造山、造山后伸展等重大地质事件。大石桥组中蛇纹石化大理岩中的铀矿化,以及连山关铀矿床、翁泉沟地区铁-硼-铀矿床的热液铀成矿作用均形成于古元古代晚期造山后/非造山区域伸展环境,可能与区域伸展体制下的地幔柱活动有关。     

粤东横田花岗斑岩SHRIMP锆石U-Pb年龄、岩石地球化学和锆石Lu-Hf同位素组成及其地质意义

横田花岗斑岩位于粤东田东钨锡多金属矿床的中部。以横田花岗斑岩为研究对象,开展了SHRIMP锆石U-Pb定年、岩石地球化学、锆石Lu-Hf同位素组成特征研究。花岗斑岩多呈岩株产出,灰白色,斑状结构,块状构造,主要由斑晶(10%)和基质(90%)组成,斑晶由斜长石、钾长石、石英、黑云母组成,杂乱分布,粒度为0.6~6mm,基质由长石、石英、黑云母组成,长石粒度为0.02~0.25mm。获得花岗斑岩锆石~(206)Pb/~(238)U年龄加权平均值为142±1Ma,说明岩体形成于早白垩世。主量、微量元素特征显示,花岗斑岩属于高钾钙碱性强过铝质,富集Rb、U、Nd、Hf等元素,亏损Ba、Nb、Sr、P、Ti等,与高分异的S型花岗岩相似。花岗斑岩的锆石ε_(Hf)(t)值均小于0,在t-ε_(Hf)(t)和t-(~(176)Hf/~(177)Hf)_i图上,所有样品点均落在球粒陨石演化线之下和华南中元古代基底演化线之上,二阶段模式年龄变化范围为1.28~1.47Ga,表明成岩物质主要来源于中元古代古老地壳变质泥岩部分熔融。     

Optical dating and soil micromorphology at MacCauley's Beach,New South Wales,Australia

The ability to position landscapes in a context of time and space is a particular goal of Quaternary science research. The lack of context for dating samples published previously for MacCauley's Beach, an important site for the reconstruction of Australian sea levels, warranted a re‐evaluation of both the site stratigraphy and chronology. In this study, we combined optically stimulated luminescence (OSL) dating of sedimentary quartz grains and soil micromorphology of the same samples to improve our understanding of the depositional history and chronology of the sediments. This combination allowed the contextualization of samples not only in time and space, but also in terms of their depositional histories. The latter is important in OSL dating, where pre‐, syn‐ and post‐depositional processes can all influence the accuracy and precision of the final age estimates. The sediment profile at MacCauley's Beach is made up of three major units. The basal mottled mud layer has undergone extensive pedogenesis since deposition, and only a minimum age of 14.7 ± 2.7 ka could be calculated. The overlying grey mud, with OSL ages from the bottom and top of the unit of 10.0 ± 0.7 and 7.7 ± 0.5 ka, respectively, shows evidence of soil structure collapse. This unit correspond to the onset of the mid‐Holocene sea‐level high stand for this region. The overlying sand layer was first deposited at 7.5 ± 0.4 ka, with deposition continuing beyond 6.6 ± 0.4 ka. Not only does the chronology presented constrain the timing of deposition (and the extent of post‐depositional processes) at MacCauley's Beach, but the methodological approach used here can be applied to any site to aid in the interpretation of formation processes and assess their influence on OSL age determination. Copyright © 2014 John Wiley & Sons, Ltd.