早渐新世钙质超微化石演变与营养盐及二氧化碳关系     

马瑞罡  杨海长  金晓波  赵钊  张功成  刘传联 《海洋学报(英文版)》2020,39(10):70-80

南海北部早渐新世发生明显的营养供给和二氧化碳浓度的变化，相关地质记录为研究颗石藻的生理机制提供了理想的自然实验室。在本研究中，我们建立了一个新的颗石藻群落演化的指标，定义为E*比值。该比值由富营养属种和中等-贫营养属种的相对丰度计算而得（E^*=e/(e+c)×100，e代表富营养属种，c代表中等-贫营养属种）。其中富营养属种包括小Reticulofenestra， Reticulofenestra lockeri组，Reticulofenestra bisecta组和Coccolithus pelagicus组，而中等-贫营养属种包括Cyclicargolithus spp.。E^*指标与早渐新世营养盐指标具有较强的相关性，但在不同二氧化碳浓度的条件下表现不同的公变趋势。将群落组合与已发表的二氧化碳浓度数据对比，我们提出颗石藻可能在二氧化碳持续降低的环境下改变其对碳源和营养盐的利用方式，指示颗石藻的碳浓缩机制可能开始于早渐新世。  相似文献   

中国避暑型与避寒型宜人气候的分布特征及差异     

邓粒子  保继刚 《地理研究》2020,39(1):41-52

宜人气候可以分为避暑型和避寒型两种类型,但现有研究鲜有关注国内两类气候的分布特征及差异。本文采用1981—2010年2132个国家气象观测站数据,基于温湿指数、风寒指数和着衣指数计算各个气象站点的气候综合舒适指数,结合协同克里金空间插值方法对全国避暑型和避寒型宜人气候的分布特征进行了研究,并对两类气候的地域差异进行了分析。结果表明：① 中国避暑型气候区包括40°N以北的西北边疆和东北地区、西北中部地区及西南地区三大集中分布区。中国避寒型气候区集中分布在北回归线以南的低纬地区。② 国内夏冬两季的气候不舒适地域广阔,包括环渤海、长三角等经济发达、人口稠密地区,避暑型与避寒型气候资源的开发潜力显著。③ 两类宜人气候呈现明显的地域分离特征,拥有避暑和避寒双重属性的地方极少。④ 国内避寒型气候是稀缺资源,具有垄断性特征;而避暑型气候相对分布广泛,是一种相对遍在性资源。本文不仅丰富了宜人气候分布特征研究的理论成果,而且可为地方气候资源的旅游开发提供科学依据。  相似文献   

Climate driven coevolution of weathering profiles and hillslope topography generates dramatic differences in critical zone architecture     

Robert S. Anderson  Harihar Rajaram  Suzanne P. Anderson 《水文研究》2019,33(1):4-19

Considerable debate revolves around the relative importance of rock type, tectonics, and climate in creating the architecture of the critical zone. We demonstrate the importance of climate and in particular the rate of water recharge to the subsurface, using numerical models that incorporate hydrologic flowpaths, chemical weathering, and geomorphic rules for soil production and transport. We track alterations in both solid phase (plagioclase to clay) and water chemistry along hydrologic flowpaths that include lateral flow beneath the water table. To isolate the role of recharge, we simulate dry and wet cases and prescribe identical landscape evolution rules. The weathering patterns that develop differ dramatically beneath the resulting parabolic interfluves. In the dry case, incomplete weathering is shallow and surface parallel, whereas in the wet case, intense weathering occurs to depths approximating the base of the bounding channels, well below the water table. Exploration of intermediate cases reveals that the weathering state of the subsurface is strongly governed by the ratio of the rate of advance of the weathering front itself controlled by the water input rate, and the rate of erosion of the landscape. The system transitions between these end‐member behaviours rather abruptly at a weathering front speed ‐ erosion rate ratio of approximately 1. Although there are undoubtedly direct roles for tectonics and rock type in critical zone architecture, and yet more likely feedbacks between these and climate, we show here that differences in hillslope‐scale weathering patterns can be strongly controlled by climate.  相似文献   

Pricing Weather Derivatives Index based on Temperature: The Case of Bahir Dar,Ethiopia     

Tesfahun BERHANE  Aemiro SHIBABAW  Gurju AWGICHEW 《资源与生态学报(英文版)》2019,10(4):415-423

In this paper we present a stochastic model for daily average temperature to calculate the temperature indices upon which temperature-based derivatives are written. We propose a seasonal mean and volatility model that describes the daily average temperature behavior using the mean-reverting Ornstein-Uhlenbeck process. We also use higher order continuous-time autoregressive process with lag 3 for modeling the time evolution of the temperatures after removing trend and seasonality. Our model is fitted to 11 years of data recorded, in the period 1 January 2005 to 31 December 2015, Bahir Dar, Ethiopia, obtained from Ethiopia National Meteorological Services Agency. The analytical approximation formulas are used to price heating degree days (HDD) and cooling degree days (CDD) futures. The suggested model is analytically tractable for derivation of explicit prices for CDD and HDD futures and option. The price of the CDD future is calculated, using analytical approximation formulas. Numerical examples are presented to indicate the accuracy of the method. The results show that our model performs better to predict CDD indices.  相似文献   

Hydrological regulation of chemical weathering and dissolved inorganic carbon biogeochemical processes in a monsoonal river     

Jing Liu  Jun Zhong  Hu Ding  Fu-Jun Yue  Cai Li  Sen Xu  Si-Liang Li 《水文研究》2020,34(12):2780-2792

To better understand the mechanisms relating to hydrological regulations of chemical weathering processes and dissolved inorganic carbon (DIC) behaviours, high-frequency sampling campaigns and associated analyses were conducted in the Yu River, South China. Hydrological variability modifies the biogeochemical processes of dissolved solutes, so major ions display different behaviours in response to discharge change. Most ions become diluted with increasing discharge because of the shortened reactive time between rock and water under high-flow conditions. Carbonate weathering is the main source of major ions, which shows strong chemostatic behaviour in response to changes in discharge. Ions from silicate weathering exhibit a significant dilution effect relative to the carbonate-sourced ions. Under high temperatures, the increased soil CO₂ influx from the mineralisation of organic material shifts the negative carbon isotope ratios of DIC (δ¹³C_DIC) during the high-flow season. The δ¹³C_DIC values show a higher sensitivity than DIC contents in response to various hydrological conditions. Results from a modified isotope-mixing model (IsoSource) demonstrate that biological carbon is a dominant source of DIC and plays an important role in temporal carbon dynamics. Furthermore, this study provides insights into chemical weathering processes and carbon dynamics, highlighting the significant influence of hydrological variability to aid understanding of the global carbon cycle.  相似文献   

临沂市地质灾害现状及易发程度分区评价          下载免费PDF全文

祝丽媛  窦连波  李莺宇  陈秀娟  王伟德 《山东国土资源》2019,35(11)

2016年,临沂市地质灾害排查共查明了391处地质灾害隐患点,主要类型为崩塌、滑坡、泥石流、采空塌陷和岩溶塌陷,崩塌数量最多,其次为采空塌陷和岩溶塌陷。地质灾害规模以小型为主。该文详细介绍了临沂市地质环境背景条件,各类地质灾害发育现状及分布特征。在此基础上,采用"地质灾害综合危险性指数法"进行地质灾害易发性评价,运用栅格数据处理方法将临沂市划分成1350个面积相等的单元,对影响地质灾害发育的地质条件、地形地貌条件、气候植被条件、地质灾害隐患点、地质灾害规模、分布密度、活动频次和险情等要素进行量化,根据实际情况对地质灾害易发程度分级进行定性修正,将临沂市地质灾害易发程度划分为高易发区、中易发区、低易发区及不易发区4个区。预测了地质灾害发展趋势,划分了地质灾害防治分区,建议完善地质灾害预警预报系统,为临沂市应急管理局的地质灾害应急救援提供地质灾害基础背景资料。  相似文献   

珠江口盆地荔湾凹陷上渐新统—早中新统物源特征及其对沉积充填的影响     

邢作昌  张忠涛  林畅松  张博  洪方浩  张正涛 《中国地质》2020,47(5):1577-1588

利用化学蚀变指数法恢复物源区的风化历史及沉积物通量是一种经济实用、行之有效的方法。前人对珠江口盆地荔湾凹陷对应物源区的研究相对薄弱。本文通过对区内岩心测试数据进行化学蚀变指数分析，恢复晚渐新世—早中新世物源区的风化历史，并进行沉积物通量的估算，在此基础上探讨物源特征对研究区内沉积充填的控制作用。研究表明，晚渐新世研究区对应物源区经历了强烈风化阶段，该阶段产生的丰富的沉积物供给是研究区西北部快速进积、规模壮观的陆架边缘三角洲及斜坡重力流沉积体系发育的重要控制因素之一；早中新世，西北物源区风化减弱，沉积供给减少，但研究区东部沉积物供应较西部要充分得多，表明早中新世，研究区南部除了来自西北部的主要物源外，局部物源对该时期的沉积具有重要影响；推测东部物源(东部古隆起、兴宁古隆起)的突然复活是促进研究区东部早中新世沟槽形成发育的重要原因之一。在超深水区进行沉积物源区的研究中，这种半定量的方法对盆内局部物源的确定具有重要的指示意义。  相似文献   

岩溶泉补给地表溪流二氧化碳脱气作用研究     

蓝高勇  汪智军  殷建军  唐伟  吴夏  杨会 《岩矿测试》2021,(5):720-730

碳酸盐岩风化作用(即岩溶作用)能够吸收大气二氧化碳(CO_2),形成溶解无机碳(DIC,dissolved inorganic carbon),被认为是一种重要的陆地碳汇,其在全球碳收支平衡和未来陆地增汇中可能会有重要贡献。然而,目前对岩溶碳汇的稳定性还存在争议,一些学者认为岩溶地下水出露地表后会发生CO_2脱气,对岩溶碳汇通量估算带来不确定性。本文以广西桂林长流水表层岩溶泉补给的溪流(约2.7km长)为例,利用水化学和同位素质谱仪测试技术,研究了溪水水化学指标和溶解无机碳同位素(δ~(13)C_(DIC))沿流程变化,探讨了溪流CO_2脱气过程、通量及其影响因素,以更好地了解岩溶碳汇的稳定性。结果表明:从泉口向下游,在陡坡地段(C1～C14段,长约270m,坡度约10°),溪水pH值、方解石饱和指数和δ~(13)C_(DIC)沿流程分别升高了0.9、0.9和1.8‰,而CO_2分压、电导率、Ca~(2+)浓度和DIC浓度分别下降了85%、34μS/cm、0.2mmol/L和0.7mmol/L,说明溪水发生了显著的CO_2脱气,并伴随碳酸钙沉淀。而在平缓地段(C18～C26段,长约2.1km,坡度1°),溪水各水化学指标和δ~(13)C_(DIC)变化较小,指示CO_2脱气作用较弱。这些发现表明溪流CO_2脱气受到了地形决定的水动力条件控制。另外,在下游渠段,受支流汇入影响,溪水pH值和方解石饱和指数有所降低,在一定程度上抑制了CO_2脱气。溪流CO_2脱气能够抵消部分岩溶作用固定的大气CO_2量,但是在长流水这一高地势、低流量且有碳酸钙沉积的环境下,其抵消的量也仅占29%。对于在低缓地区受流量很大的岩溶泉/地下河补给的河流,其CO_2脱气作用对岩溶碳汇的影响有限,加之受可能增强的水生光合生物固碳效应影响,岩溶碳汇应具有很高的稳定性。  相似文献   

蓟县中、新元古界的成岩作用——源于矿物学的数据     

王河锦  陈梦瑶  安佳丽  王冠玉  晏玉 《地质学报》2021,95(5):1469-1480

本文运用系列黏土矿物学和碳酸盐结构占位的方法研究了蓟县中、新元古界剖面出露的碎屑岩和碳酸盐岩.这些方法包括了伊利石结晶度、绿泥石结晶度、黏土矿物组合、粒度分布、多型、有序度、Mg/Ca离子占位以及地质温压计.结果表明:伊利石结晶度Kübler指数范围为0.37°～1.37°Δ2θ,绿泥石结晶度árkai指数范围为0.31°～2.40°Δ2θ,以及1Md的多型,一致指示本区处于晚期成岩作用影响范围,仅非常有限局部达到了初始变质的状态;黏土矿物组合主要是伊利石、伊蒙混层、绿蒙混层和高岭石;粒度分布范围为8～24 nm,其上界(23～24 nm)达到了NEWMOD计算的理论成岩带/近变质带界限,与结晶度数据一致,也表明了本区处于晚期成岩阶段.白云石有序度的数据表明,本区碳酸盐岩白云石的有序度值范围为0.19～0.99,可分为4个带:甚低级有序带、低级有序带、中级有序带、高级有序带.与川东石炭-二叠系碳酸盐岩相比,中低级有序带有一定的油气前景.本区由西向东,由甚低级有序带变化到高级有序带,白云石有序度升高.估计的成岩作用温度为183～200±20℃,压力为330 MPa,古地热梯度为17～21℃/km.  相似文献   

Reservoir Characteristics and Genetic Mechanisms of the Mesozoic Granite Buried Hills in the Deep‐water of the Qiongdongnan Basin,Northern South China Sea     

YOU Li  XU Shouli  MAO Xuelian  ZHONG Ji  JIAO Yaoqi  XIONG Xiaofeng 《《地质学报》英文版》2021,95(1):259-267

Due to its structure,rock and mineral composition,fluid and other factors,the granite Buried Hill Reservoir is highly heterogeneous with a complex longitudinal structure and a reservoir space made up of a combination of dissolution pores and fractures.This paper is based on current understanding of tectonic evolution in the northern part of the South China Sea,in conjunction with the seismic phase characteristics.It is determined that the meshed fault system was formed by three stages of movement-tectonic compression orogeny during the Indochinese epoch,strike-slip compression-tension during the Yanshanian Period,early fracture extension activation during the Himalayan-which controlled the distribution of the Buried Hill Reservoir.Drilling revealed two types of buried hills,faulted anticline and fault horst,their longitudinal structure and the reservoir space type being significantly different.The mineral composition,reservoir space and diagenetic characteristics of the reservoir rocks and minerals were analyzed by lithogeochemistry,micro section and logging etc.,it thus being determined that the Mesozoic rocks of the Songnan Low Uplift in the Qiongdongnan Basin are mainly composed of syenogranite,granodiorite,monzogranite,which is the material basis for the development of the Buried Hill Reservoir.The content of felsic and other brittle minerals is more than 70%,making it easy for it to be transformed into fractures.At the same time,the weathering resistance of granodiorite and monzogranite is weaker than that of syenogranite,which is easily weathered and destroyed,forming a thick sand gravel weathering zone.With increasing depth of burial,weathering and dissolution gradually weaken,the deep acidic fluid improving the reservoir property of internal fractures and expanding the vertical distribution range of the reservoirs.The research results lay a foundation for the exploration of Buried Hill in the deep-water area of the Qiongdongnan Basin.  相似文献