首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到19条相似文献,搜索用时 140 毫秒
1.
通过对山西襄汾东坡沟全新世黄土剖面地层学和土壤学的研究,以及碳酸钙、铁和粒度的测定,发现全新世古土壤中碳酸钙经历了明显的淋溶与淀积,古土壤上部CaCO3平均含量10.58%,下部为18.47%,CaCO3结核的淀积深度约为1.1m,铁在古土壤顶部有微弱的淋移和富集,粘化作用不明显。成壤作用始于全新世大暖期之初,较为强烈的成壤作用发生于大暖期的晚期(4100aB.P~3100aB.P),这一阶段土壤湿度大,气候波动小,CaCO3淋溶较强。大暖期结束后,冬季风在黄土高原占主导地位,土壤的淋溶作用和粘土作用均有一定程度减弱,显示气候干旱的趋势。该剖面位于古山前洪积扇前端,地形较高,降水易分散,淋溶作用总的说来不强烈,土壤上部CaCO3残留较多,CaCO3淀积深度较浅,土壤类型接近黑垆土。  相似文献   

2.
黄土高原全新世黄土-古土壤演替及气候演变的再研讨   总被引:16,自引:5,他引:16       下载免费PDF全文
唐克丽  贺秀斌 《第四纪研究》2004,24(2):129-139,T001
文章从黄土-古土壤的演替规律、黄土再沉积与古土壤埋藏后的次生成壤特殊性,揭示了第四纪生物气候演变的实质。对黄土高原具代表性的现代耕种土壤壤土和黑垆土的研究,揭示了土壤剖面内伏形成环境较现代暖湿的古土壤层;对于土壤剖面上部的覆盖层,证实不仅是人为施加土粪的堆积物,且包含新的黄土沉积物;从土壤发生学观点,埃土与黑垆土称之耕种埋藏型古土壤较合适;通过分辨古土壤剖面层内干旱草原和暖湿型森林植被孢粉共存的矛盾实质,证实黄土高原全新世曾存在茂密的森林和森林草原植被及森林型土壤的发育,并延续到人类历史时期。在第四纪研究中,通常把黑垆土作为全新世代表地层,以S0表示,我们的研究补充提出,根据黄土高原生物气候地带性的分异规律,自南而北,S0应以埃土与黑垆土分别表示,并应在S0层上部划分出Lx,说明气候冷干化的趋向及新一轮黄土沉积期已悄然来临。以上问题的再研讨,对第四纪生态环境演变和当前黄土高原生态环境建设的战略部署,具有重要的理论和实际意义。  相似文献   

3.
长江三角洲晚第四纪古土壤与古环境初探   总被引:9,自引:0,他引:9  
陈庆强  李从先 《沉积学报》1995,13(A01):79-87
长江三角洲地区第一硬粘土层中有植物根、植屑、裂隙、粘粒胶膜、土壤结构体、结核等古土壤特征,系古土壤。料度,化学分析及磁组构分析揭示它为多期成土作用形成的揽合古土壤层。根据硬粘土层与南京下蜀土,黄土高原黄土-古土壤系列及上海亚近代潮坪沉积的磁性参数对比,推断该古土壤的母系系河流冲积物。  相似文献   

4.
晚第三纪以前形成的古土壤可以揭示地质时期的古环境。辨识古土壤的主要标志包括野外形态特征、微形态特征、地球化学特征等。当前古土壤分类一般基于现代土壤的系统分类体系,即采用诊断层和诊断特征,辅之以古土壤总体的化学性质等指标划分古土壤类型。形成于晚第三纪以前的古土壤可以重建全球范围的古气候变化历史,同时揭示前寒武纪时期古大气O2分压以及后寒武纪时期古大气CO2浓度水平的演化过程;古土壤具有空间和时间等多重信息,能反映流域或区域的古景观、古地貌、古水文特征。但目前缺乏一个广为接受的古土壤分类系统,成岩作用对古土壤特征的影响以及古土壤记录的古环境信息机制与解译等方面也还需要深入探讨。今后必须加强成岩作用对古土壤特性的影响以及现代土壤与其环境的对应关系的研究。  相似文献   

5.
本文根据雄县地热田钻孔的古土壤、孢粉分析和地层层序揭示第四纪以来该区土壤层及淋溶淀积作用可划分二大带。0~420m:从上到下土壤颜色加深,淋溶淀积加强,出现团块状钙质,古气候由老至新从温湿转化为现代干冷;420~800m:淋溶淀积作用较强烈,上部地层显示过湿的气候条件,反映古气候从干热向温湿转变。第四纪以来植被发展曾经历了4个大的阶段,冷暖干湿气候交替有16次明显变化。  相似文献   

6.
全新世与上次间冰期气候差异的古土壤记录   总被引:11,自引:2,他引:11       下载免费PDF全文
郭正堂  刘东生 《第四纪研究》1993,13(1):41-55,T000
目前国际上对全新世与上次间冰期的气候差异还存在着较大的争议。对西欧阿晴里姆黄土中全新世和上次间冰期古土壤(埃姆古土壤),中国黄土中S0及S1的对比研究表明,埃姆古土壤和S1是典型的复合土壤,记载了相同的沉积-成壤事件序列,并与深海氧同位素记录有很好的一致性。第一成壤期与氧同位素阶段5e相对应,代表了典型的间冰期气候。西欧在该时期形成的土壤与全新世土壤的成壤过程基本相同,二者反映了类似的气候条件;而中国黄土中S0和S1则具很大差异,这表明我国北方最后两次间冰期的气候条件显著不同。青藏高原在中更新世末期以来的隆升对季风环流的影响是值得注意的原因之一。  相似文献   

7.
伍斌  吴乃琴 《第四纪研究》2008,28(5):901-908
通过对黄土高原西峰黄土剖面S5古土壤层的蜗牛化石组合研究发现,西峰地区在S5形成时(对应海洋氧同位素MIS1513期)气候环境经历了几次显著的波动。MIS15期地层中绝大多数蜗牛壳体被溶蚀,气候非常暖湿,夏季风强盛;MIS14是个弱冰期,蜗牛组合显示气候以凉湿为主,仍然有较强的夏季风影响;MIS13期以暖湿的气候为主,夏季风增强。对温湿蜗牛种类冠状砂螺(Gastrocopta coreana)含量变化的功率谱分析显示出明显的23ka周期,表明岁差轨道驱动的低纬太阳辐射是控制黄土高原夏季风变化的主导因素;冷干种类杂色虹蛹螺(Pupilla aeoli)含量变化具有明显的100ka和弱的43ka周期,说明即使在气候特征总体暖湿的背景下,冬季风仍具有以全球冰量(100ka)为主导周期的变化特征。在海洋和冰芯记录中MIS13和MIS15时期并不是最温暖的间冰期,但在黄土高原受到强夏季风的持续影响,这可能与此时北半球夏季太阳辐射量的增强和北大西洋深层流强度的加强有关。S5中S5SS1与S5SS3两层强烈发育的古土壤可能有着不同的发育机制,S5SS1因其较发育的母质、超长的成壤期,形成了比S5SS3更强的成壤特征。分析认为全球冰量与轨道驱动的北半球太阳辐射对MIS1513时期黄土高原气候环境的演替和冬、夏季风的消长起了主导作用。  相似文献   

8.
西安地区全新世古土壤的研究   总被引:4,自引:1,他引:3  
侯春红 《中国岩溶》1999,18(3):207-212
本文根据磁化率,粒度,CaCO3,Fe2O3和Al2O3含量以及土壤微结构等方面的资料对西安地区的全新世古土壤的性质类型及环境的特点进行了较为全面的论述,各项资料显示,该地区全新世大暖期的古土壤为温湿气候条件下发育的淋溶褐土,而并非过去所称的半干旱条件下发育的“黑垆子”该层古土壤发育时的年均降水量应不小于750mm。一新世古土壤底部之下分布深度达2m多的密集根充填充物,指示当时在聚森林植被。  相似文献   

9.
中国黄土堆积的磁性记录与古降雨量重建   总被引:8,自引:0,他引:8  
概述了中国黄土和古土壤堆积的磁性特征,进而介绍成壤作用磁铁矿成因模式,讨论控制黄土—古土壤层矿物磁性特征的气候参量及其利用土壤成因磁化率重建古降雨量。  相似文献   

10.
运用岩石磁学和地球化学相结合的方法对宝鸡剖面S5和S3古土壤的磁性特征进行了详细对比分析,结果表明S5古土壤层Rb/Sr比值较高,S5古土壤形成期气候温暖湿润,成壤程度比S3时期强.S5层亚铁磁性矿物含量低于S3层,反铁磁性矿物主要为针铁矿;而S3层的反铁磁性矿物主要为赤铁矿.S5层土体表面及土壤空隙中可见大量黑褐色的铁锰胶膜分布,由于沉积后土壤长时期处于偏干或偏湿的氧化、还原交替环境中,细粒的磁铁矿和/或磁赤铁矿、赤铁矿溶解转化成褐铁矿、针铁矿等弱磁性矿物,主要转化成在局域湿润环境下能够稳定存在的针铁矿,这种磁性矿物的转化可能导致了成壤强的S5古土壤超顺磁亚铁磁性矿物含量的减少和磁化率的降低.  相似文献   

11.
中国黄土中古土壤的发生学研究   总被引:4,自引:2,他引:4  
石元春 《第四纪研究》1989,9(2):113-122
应用形态学、微形态学、化学和矿物学研究了中国黄土中古土壤的发生学性状和成土过程。离石黄土(中更新世)中古土壤为发育程度(碳酸盐淋溶和粘化)不同的褐土型土壤。马兰黄土(晚更新世)中为生草过程强和粘化过程稍弱的灰褐土型土壤。全新世黄土中为碳酸盐淋溶和粘化过程均弱的弱度发育的碳酸盐灰褐土型土壤。午城黄土(早更新世)中可能是棕褐土。本文还探讨了黄土中古土壤在时间和空间上的演替和分类问题。  相似文献   

12.
黄土高原红粘土成因及上新世北方干旱化问题   总被引:39,自引:10,他引:39       下载免费PDF全文
本文通过对黄土高原第三纪红粘土的野外观察,以及沉积学和地球化学分析,得到能证明红粘土为风成沉积的新证据。另外,佳县红粘土沉积的土壤学特征表明,上新世时期的东亚夏季风强度总体强于第四纪。  相似文献   

13.
西峰和西安黄土中盐碱化古土壤气候意义的初步探讨   总被引:9,自引:8,他引:9  
郭正堂 《第四纪研究》1992,12(2):107-117,193
对西峰和西安黄土剖面中古土壤的研究揭示出,作为重要气候地层标志的S4和S5古土壤竟有盐化和碱化现象。盐碱化特性直接关系到如何认识这些古土壤的气候意义。土壤化学、微形态及粘土矿物分析表明,上述古土壤以草原土特征为主,并在气候最宜期发育了森林植被。盐碱化特性并非产生于土壤被埋藏以后,而是古土壤发育末期的产物。该时期大气粉尘堆积似乎是可溶盐的来源。  相似文献   

14.
Márton Pécsi 《GeoJournal》1995,36(2-3):117-131
In the process of loessification, the development of loess fabric, the role of zonal, regional and partly of local environmental factors is regarded decisive. In the loess sequences various genetic types of loess pockets and paleosols occur and reflect different climatic and paleogeographical conditions.As a consequence, even within a single profile the colour, grain size and mineral composition, CaCO3 content, degree of weathering and fabric of loess may vary. Zonal, regional or even local variations in such loess properties may equally derive from syngenetic or postgenetic processes. For similar reasons, spatially and temporally different forms, types and subtypes of paleosol also developed.This way, loess and soil formation resulted in various spatial types in the same glacial, interstadial or interglacial phase in the various geographical zones and regions. Although there exist major loess regions where the interglacial soils (eg brown forest soils) are markedly distinct from interstadial steppe soils or from other types of humic soils, continental loess areas can also be observed where the paleosols developed under interglacial and interstadial conditions (eg steppe or forest steppe soils) cannot be referred into different genetic types. In such cases the changes in paleoenvironments are difficult and uncertain to reconstruct.The interregional correlation of paleosols is occasionally hindered by the various terminologies applied to denote them. In addition, there are uncertainties concerning the dating and identification of paleoenvironments of polygenetic soils and of soil complexes consisting of paleosol units: how many soil formation phases they represent and how long erosional gaps can be reckoned with between these phases.  相似文献   

15.
南海诸岛土壤的形成和年龄   总被引:4,自引:1,他引:3  
本文在阐明南海珊瑚诸岛土壤的生物集聚过程、积盐和脱盐过程,以及有关的土壤诊断特性基础上,进一步介绍了那里的磷质石灰土和滨海盐土两大土壤类型,它们的空间分布及其与岛屿结构、地形、植被和鸟类活动之间的关系。最后,作者针对南海珊瑚岛土壤的特征,运用(14)C方法探讨了它的年龄及其与土壤形成、发育之间的相互关系。  相似文献   

16.
灵台黄土-红粘土序列的磁性地层及粒度记录   总被引:64,自引:12,他引:52       下载免费PDF全文
甘肃灵台县任家坡黄土-红粘土剖面的磁性地层学研究表明;中国北方连续的风成堆积可下推到705MdB.P。第三纪红粘土的粒度组成从上到下变化很小,与黄土-古土壤序列的粒度大幅度变化形成强烈的反差,意味着晚第三纪时期的气候总体上要比第四纪时期稳定。在705~2.6MaB.P.的红粘土沉积中,可分出的110~115个土壤B层与钙质结核层的组合,初步表明在这个时期有约110~115次气候旋回。  相似文献   

17.
A study area in an arid region of southern New Mexico is in basin-and-range topography and includes both a river valley and a closed basin. Holocene soils occur in valley fills and low terraces between Pleistocene fans, in and near drainageways on the fan-piedmont, on ridges, and in dunes. Holocene soils suggest the character of initial development in soils that are much older and more complex, and record the beginnings of various soil horizons. Noncalcareous brown or reddish brown B horizons have formed in low-carbonate parent materials of stable sites. Incipient development of the argillic horizon and the Haplargids occurs at stable sites in very gravelly materials that are about 1–2000 yr old. The cambic horizon and Camborthids occur in adjacent low-gravel materials of the same age. The argillic horizon occurs continuously in soils of earliest Holocene, particularly in very gravelly materials. Where soils have been truncated, as in areas affected by landscape dissection, argillic and cambic horizons are usually absent and the soils are Torripsamments, Torriorthents, or Torrifluvents depending on content of sand, gravel, and organic carbon. In high-carbonate parent materials, noncalcareous, reddish brown B horizons have not formed at any time in the Holocene. Most of these soils are Torriorthents or Torrifluvents although an incipient calcic horizon has formed in some of the oldest Holocene soils; the latter are Calciorthids. Horizons of carbonate accumulation are the best and most common pedogenic indicators of soil age. Stage I carbonate horizons are a major feature of pedogenesis in the Holocene. Because of additions of carbonate from the atmosphere, carbonate horizons are morphologically similar whether they have formed in high or low-carbonate alluvium. The carbonate accumulations are illuvial.Some Holocene deposits apparently resulted from changes in climate. Others, such as the youthful deposits of coppice dunes, apparently were caused by man's introduction of cattle and subsequent overgrazing and seed dispersal.  相似文献   

18.
Alluvial fans are one of the most important landforms in geomorphological and paloenvironmental studies. The objective of this study was the application of clay mineral assemblages and micromorphological properties of the studied paleosols in the geomorphic surfaces of an alluvial fan in the eastern Isfahan as proxies for paleoenvironmental and paleoclimatic changes. Micromorphology, X-ray diffraction, and scanning electron microscopy approaches were used to study the representative pedons. The results indicated that the illuviation process in the calcareous soils of the arid regions of the eastern Isfahan was probably in response to Quaternary moist conditions. There was no significant difference between clay coating properties of the studied relict and buried paleosols. Clay mineralogical study suggested that kaolinite and illite were inherited from the parent materials, while smectite and palygorskite were formed in the soil environment. Paleoargillic horizon was characterized by smectite and calcic (especially the calcrete) horizons were dominated by palygorskite. Palygorskite was accumulated by both neoformation and illuviation processes. High clay content, high intensity of smectite peak, and activity of the illuviation process in paleoargillic horizon demonstrated the seasonality of climate (rainfall) even in the moist periods of Quaternary in Central Iran. Clay mineralogical assemblages suggested a trend of increasing environmental aridity in the study area. This study, therefore, highlighted the role of clay mineralogical investigations in arid lands’ geomorphological and paleoenvironmental researches.  相似文献   

19.
Perennially frozen loess deposits in the Klondike goldfields include paleosols formed in full-glacial environments, correlated by Alaskan distal tephra with Marine Isotope Stages (MIS) 2 and 4. Patterns of organic and inorganic carbon and clay distribution, microstructures, and profile morphologies indicate that soil formation occurred in a base-rich environment in which organic matter accreted predominantly as root detritus. At sites approximately 20 km apart, the expression of cryoturbation and ice wedge development decreases in strength upward in loess-paleosol sequences correlated with MIS 4, suggesting increasing aridity. Configurations of cryoturbation features and ice-wedge thaw unconformities, the presence of numerous ground squirrel burrows, and an absence of peat accumulation suggest that these substrates were predominantly well-drained, with active layers of equal or greater thickness than in modern soils on similar sites in the west-central Yukon. Some characteristics of these paleosols are similar to those of modern steppe and tundra soils, consistent with plant macrofossil evidence for local ecological diversity during full-glacial conditions in eastern Beringia.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号