四川盆地中生代古土壤发生学特征及古环境意义

古土壤形成于地质历史时期的地球表面,直接记录了其形成时地球陆地表层的环境信息.以四川盆地中生代古土壤为研究对象,通过古土壤的形态与微形态、矿物组成、颗粒组成以及地球化学等成土特征的观察与分析,开展土壤发生学特征概述与分类研究并探讨古土壤指示的环境意义.结果表明:(1)四川盆地中生代古土壤具有生物遗迹、成壤碳酸盐结核、土...     

黄淮海平原晚第四纪古土壤

本文运用孢子花粉,古生物化石和放射性碳断代等手段,从土壤剖面层段的特征,土壤年龄和环境变化方面证明,分布于黄淮海平原的变性土不是现代土壤,而是古土壤,该古土壤自晚新世晚期以来经历了三次沉积－成土作用旋回,其土壤发育程度较弱,且是由钙质结核土层,暗色土层,表土层和（或）淤土层组成的一个叠置型古土壤。     

Andosol to Luvisol evolution in Central Mexico: timing, mechanisms and environmental setting

Surface and buried Andosols and buried Luvisols of the Nevado de Toluca Late Quaternary tephra-paleosol sequence (Central Mexico) were studied to show whether these soils present an evolutionary sequence and to determine the pedogenic mechanisms and environmental factors involved in the evolutionary process. Micromorphological observations and mineralogical composition of fine sand and clay fractions were used to detect type and succession of soil-forming process. Some of the buried Andosols, defined as “intergrade” Andosols, have a predominantly blocky structure, humus-depleted areas, redoximorphic features and thin clay coatings in Ah horizons. Clay fractions of buried Andosols contain halloysite besides amorphous components, whereas in modern Andosols, allophane is dominant. Luvisols have micro-areas with granular structure and abundant phytoliths in the groundmass of Bt horizons assumed to be the relict Andosol features. Luvisol clay fractions are dominated by halloysite and kaolinite. Primary minerals show micromorphological weathering features in all studied soils being stronger in Luvisols; however, even in Luvisols, sand fractions consist mostly of unstable volcanic silicates. We hypothesise that the studied profiles form an evolutionary sequence: Andosols–“intergrade” Andosols–Luvisols; the soil transformation is supposed to be linked to progressive crystallisation of 1:1 clay minerals. Comparing the Nevado de Toluca paleosol properties with the existing data on volcanic soil climo- and chronesequences and assessing the regional paleopedological and lacustrine records of Quaternary paleoclimates, we concluded that wet/dry climatic oscillations took place during the formation of the studied paleosols. Rapid crystallisation of 1:1 minerals occurred during dry phases, which speeded up the Andosol to Luvisol transformation and made it independent from the primary mineral weathering status. The Andosol to Luvisol transformation accelerated by climatic fluctuations is thought to be a common soil evolutionary pathway in the subtropical and tropical regions of recent volcanism, which suffered contrasting precipitation oscillations in the Quaternary.     

Paleosol identification and soil stratigraphy in South Island,New Zealand

Field and laboratory methods used for the identification of paleosols in New Zealand are discussed, and examples are given of their application to both buried and relict paleosols. Field methods include a pedomorphic index based on the quantitative assessment of four or more selected diagnostic properties for each horizon, which is useful under certain conditions to express the relative degree of development of several profiles.The significance of paleosol identification is only fully appreciated when the paleosol is defined stratigraphically and interpreted in terms of time and environment. The basis for defining soil-stratigraphic units in parts of New Zealand is outlined.     

Landscape evolution in Val Mulix,eastern Swiss Alps – soil chemical and mineralogical analyses as age proxies

Towards the end of the last glacial cycle, repeated re-advances of valley glaciers in the European Alps combined with periglacial processes led to the formation of a variety of climate-related landforms. Independent age measurements of moraines and rock glacier lobes using both in-situ produced and meteoric ¹⁰Be allows for the use of soil formation as an age proxy. In this complementary study we present chemical and mineralogical data from five Podzols from Val Mulix in Eastern Switzerland. Two of them developed on granitic Lateglacial moraines (14.9 ka and 10.7 ka, respectively) and three were sampled on lobes of a morphostratigraphically connected relict rock glacier, covering an age range of approx. 10.7 ka to 8.6 ka. Besides the evaluation of the suitability of selected pedosignatures for a relative age separation, we hypothesised that these pedosignatures should give further information about the evolution of the specific sites. Although the soils had a high skeleton content and the oldest soil started its development in a slightly colder climatic phase, typical weathering trends could still be detected. Whereas weathering indices such as the (K + Ca)/Ti ratio or the B-index reflect time trends reasonably well, the mineralogical composition of the fine earth and clay fraction yielded a slightly more inconsistent picture; to a lesser extent, some inconsistencies were also exhibited when using the weathering mass balance approach. This is especially true for the relict rock glacier and it supports the suggested complex development history of these soils as well as the presence of pre-weathered material. Techniques that include several surface soil horizons and the soil skeleton such as the (K + Ca)/Ti ratio, the B-index and the mass balance approach gave more robust results (in terms of the expected chronology) than the ones that only referred to single horizons (clay mineralogy). Errors or variations due to potential reallocation processes within the soil horizons but without a prominent change of the overall soil characteristics are minimised using such an approach. Weathering indexes and the clay mineral assemblage provided a differentiation of soils even within a relatively narrow time range and gave insight into processes that have occurred at the specific sites. The combined relative-numerical dating approach used here not only enables an extended interpretation and mutual control, but ultimately leads to a better understanding of landscape reconstruction and evolution.     

The Mississippian Paleosols in the Brontsy Quarry,Kaluga region

A chronosequence of five Visean (Aleksinian–Venevian interval, C1v, 326–336 Mya) paleosols on the territory of Moscow calcareous sedimentary basin (Brontsy quarry, Kaluga region) was studied in detail. Two lowermost paleosols are coastal peat-bearing paleosols developed under mangrove vegetation. Three upper paleosols develop pedocomplexes, in which the lower part is the marine limestone altered to different degrees by weathering/pedogenesis with the formation of eroded Rendzina-type soil. It is overlain by paleosols developed from terrigenous sediments of playa origin. They are characterized by elevated concentrations of Fe, Mg, Ti, Ga, and some other elements; the formation of secondary micritic carbonates, iron oxides, and smectites; and increased values of geochemical indexes (such as CIA-K). Smectite (low-charged beidellite) predominates in these paleosols. Iron oxides are represented by goethite and lepidocrocite attesting to the predominance of oxygenic environments. Pedocomplex at the Mikhaylovian/Venevian boundary is overlain by non-marine palustrine deposits known as “black rhizoidal limestone.” The paleoclimate reconstruction based on the chemical composition data attests to its polycyclic character. The Mikhaylovian time was most humid was (~1000 mm/yr). Later, starting from Venevian, gradual aridization of the climate began and annual precipitation decreased to 750 mm/yr and less.     

Some applications of paleopedology in Japan

Paleosols in Japan consist of buried soils and relict soils. The former occur primarily in tephra deposit, whereas the latter occupy old land surfaces in various parts of the country. The buried soils affect construction of highways and urban development. The relict soils pose problems in forestry.The paleosols formed in tephra and buried by subsequent volcanic eruptions are chiefly Andosols with their low bulk densities, low solid ratios, high specific surfaces and high water losses. These characteristics are responsible for poor engineering performance of the paleosols and tephras. These have been especially troublesome in the Kanto plain near tokyo and around the Ashitaka Volcano. Some buried soils in tephra, as for example those in the San'in district, are exceptions to the general rule and have desirable properties for construction. Those tephras have clay fractions low in allophane and high in layer-silicate minerals.The buried soils have provided approximate ages of human artifacts through radiocarbon dating of humic horizons. Conversely, identification of artifacts found in buried soils has helped to bracket their ages.Paleosols that are relicts are chiefly members of a Red-Yellow group, many of which seem to be Udults (Ultisols). The soils apparently began forming in warmer past periods but still persist on the land surface. Such soils are strongly acid and very low in plant nutrients, with resulting low productivity when used for forestry or farming. Moreover, such soils are readily subject to erosion because of their landscape positions and poor plant cover.     

Micromorphological evidence of paleoenvironmental changes in Northern Cilento (South Italy) during the Late Quaternary

Three representative soil profiles developed during the Late Quaternary in Northern Cilento (South Italy) were studied by optical microscopy and SEM-EDS observation of thin sections to examine soil features as evidence for past climatic fluctuations.Two of the profiles are polygenetic and the third monogenetic. All these have a clear interglacial imprint, whereas the polygenetic profiles also contain other features, which can be related to periglacial conditions during the stadial glacial periods although in midlatitude coastal areas. All the paleosols show a strong marine influence during development, which probably resulted from windblown processes or submergence during past interglacial phases.     

Pedostratigraphy of Terra Rossa and Quaternary geological evolution of a lacustrine limestone plateau in central Italy

Pedostratigraphic levels (PLs) are typical assemblages of soil‐genetic horizons, formed by materials having the same degree of weathering. The pedostratigraphic approach can be very useful to comprehend the formation of the Quaternary soil cover, the environmental evolution of a territory, and to estimate the age of paleosols. A pedostratigraphic study of a Terra Rossa was carried out to understand the soil–parent material origin and to estimate the time of the beginning of pedogenesis. Besides soil and geomorphological survey, the Terra Rossa was analyzed for Fe forms, geochemistry, clay mineralogy, micromorphology, and with scanning electron microscope. Optical dating was applied to obtain age estimates for the deposition of the parent material of soil formation. The insoluble residue of limestone was obtained and analyzed for geochemistry and clay mineralogy. The bedrock is constituted by Quaternary lacustrine limestone, showing pronounced karst landforms. The soil profile is situated in a little dissolution doline and was divided into three PLs: PL1 (0–110 cm) is constituted by cambic and ochric horizons, formed during Holocene in a mixture of colluvial soil sediments and fresh limestone, with aeolian components; PL2 (110–290 cm) includes two argic horizons, which began to form during Late‐Middle Pleistocene in colluvial soil sediments, with few aeolian additions; PL3 (290–330 cm) is constituted by a red argic horizon, with nitic properties, which developed from the insoluble residue of the limestone. The age of PL3 was calculated through a mass balance and an estimation of the limestone‐dissolution rate during the Quaternary, which led to an approximate age of Middle Pleistocene, between 250 and 500 ky BP. The time of the beginning of pedogenesis on limestone can be used as a reference for the tectonic uplifting of the area and emersion of the plateau.     

从古土壤看北京环境变迁

古土壤是在古自然环境条件下形的土壤,西胡林黄土剖面位于北京低山丘陵区,埋藏有七层古土壤,根据形态和微形态特征,可以划分出碳酸盐型古土壤、普通褐土型古土壤,淋溶褐土型古土壤和棕壤型古土壤。其地球化学特征和土壤学特性的研究表明,各古土壤类型之间和发生层之间存在着显著差异,通过古城磁测年和地层对比,确定古土壤的年龄。在研究古土壤性状的基础上,配合孢粉分析,可以勾画出北京低山丘陵区的环境变迁,北京地区自50万年前至1万前,交替经历了14次温湿、冷干的气候变化。     

四川盆地晚中生代古淋溶土发生学特征与形成因素研究

[目的]理解和揭示深时古土壤的形成与演化有助于了解地球宜居性的形成与演化、促进土壤发生学理论的发展.[方法]以四川盆地晚中生代侏罗系和白垩系地层发育的古土壤为研究对象,通过对典型剖面的形态与微形态、矿物组成、颗粒组成以及地球化学等发生学特征的观察与分析,开展深时古土壤发生学特征与分类研究,并基于母质、气候、生物、地形和...     

Revealing of directed temporal changes in soils of short-term chronosequences upon the high spatial variability in the background soil properties

The properties of paleosols buried under the Filippovka group of kurgans in Orenburg oblast dating back to the second half of the fifth and to the fourth centuries BC were analyzed with the use of multivariate statistical methods. This made it possible to establish the relative chronology of construction of the kurgans, which was confirmed by the results of radiocarbon dating of the soil humus.     

Upper Permian paleosols of the East European Platform: Diagnostics of pedogenesis and paleogeographic reconstruction

A vertical sequence of seven buried paleosols composing the Klimovsk pedocomplex was studied in the basin of the Sukhona River (Vologda oblast). These paleosols were formed according to the accumulative model of pedogenesis (pedosedimentation model). They had monogenetic profiles with eluvial-gley, structural, and carbonate-illuvial types of differentiation. The set of elementary pedogenic processes responsible for the development of these soils included gleyzation in the surface horizon and around the roots, the inter- and intrahorizon translocation and segregation of iron, structuring, humification, weathering, lessivage, the migration and segregation of carbonates, and the synthesis of palygorskite and analcime. The studied paleosol profiles make it possible to reconstruct seven pedogenetic stages; each of them lasted for about n × 10²–10³ years. The paleosols were formed on a flat lacustrine-alluvial plain with drying lakes and temporary streams. The stages of inundation and water stagnation on the surface alternated with the stages of drying of the territory. The climate was warm, with well-pronounced wet and dry seasons. Against this general climatic background, arid climatic epochs marked by the development of calcic paleosols alternated with humid climatic epochs marked by the development of noncalcareous paleosols.     

Utilization for agriculture and forestry of Graulehme,Tertiary paleosols in central Europe

The Graulehme (grey loams) are relict soils or paleosols formed during the Tertiary or earlier but persisting locally on land surfaces. Thus, for example, the Permotriassic peneplain of the Rhinish Massif in Germany was mantled by deep soils during most of the Tertiary, but these were largely removed during a period of uplift and dissection in the Late Tertiary and the Pleistocene. Graulehme remained on the parts of the massif that lagged behind in the general uplift and therefore suffered little erosion. These paleosols now occupy the flat and low-lying positions in the landscape. Other components of the soil pattern are Rankers, acid brown earths and Rotlehme, the last also being paleosois but of limited extent.The Graulehme are high in silt and clay, plastic, virtually impermeable and low in base saturation and plant nutrients. Consequently, the soils are not suitable for cultivation generally. Exceptions are local bodies of the paleosols where materials from acid brown earths have been mixed with or mantle the Graulehme. The paleosols are suitable for pasture without drainage but require lime, complete fertilizer and modern management. The Graulehme are also suitable for forestry. Spruce is the best adapted species, but beech and oak can also be grown.     

Soil catenas to estimate ages of movements on normal fault scarps, with an example from the Wasatch fault zone, Utah, USA

Trenches excavated across fault scarps on a 13 ka delta surface at Brigham City, Utah, USA, document four types of soil-catena phenomena. First, the relict summit soil is eroded at the scarp crest, and its components incorporated into the accumulating colluvial wedge at the scarp base. Second, the pre-faulting soil weakens laterally as it is traced scarpward beneath the colluvial wedge from a relict position beyond the scarp toe. Third, soils developed on individual colluvial wedges and on the underlying, pre-faulting surface merge downslope to form a cumulative soil profile at the scarp toeslope. Fourth, soil horizons thicken downslope, probably due to the combined affect of more available moisture, water infiltration, and sediment accumulation.Two soil catenas were used to evaluate the applicability of a continuity approach to paleoearthquake dating, by which percentages of total development time represented by each soil at a fault scarp footslope could be estimated. The continuity approach sets total soil development at the scarp footslope, including any buried pre-faulting soil plus the sum development of all colluvial wedge soils corrected by a slope factor (F), equal to total soil development at the scarp summit. Soil development was characterized by Profile Development Index (PDI) and pedogenic clay parameters, using facies models to estimate parent material values for genetically-different colluvial units, and recognizing inherited soil components in colluvial wedges as parent material properties. The F slope factor, used to correct colluvial wedge soils for development attributable to slope position rather than age, was checked by using a nearby fluvial scarp as an independent control. Our soil data, when compared to independent age estimates, imply that rates of soil development have not been constant over the last 13 ka at Brigham City, but rather were considerably higher than average between 13 ka and 8.3 ka. Higher rates are probably due to a relatively high influx of eolian dust during the late Pleistocene to early Holocene following the lowering of Lake Bonneville, a large paleolake in the western USA. These variable rates of soil development preclude using the continuity approach for paleoearthquake dating at Brigham City. However, promising results showing that generally consistent F factors can be calculated for fault and fluvial scarps leave open the possibility that in areas where soil development rates have been relatively constant over the time period in question, the continuity approach may be a broadly applicable method for paleoearthquake dating.     

Geographic variations in particle size distribution of the last interglacial pedocomplex S1 across the Chinese Loess Plateau: Their chronological and pedogenic implications

Due to northwestward attenuation of the summer monsoon and northwestward intensification of loess deposition during the last interglacial, the last interglacial pedocomplex S1 gradually differentiated from the northwest to the southeast. The three paleosols (S1S1, S1S2, S1S3) corresponding to the marine isotope sub-stages 5a, 5c, and 5e and the two intercalated loess units (S1L1, S1L2) corresponding to the marine isotope sub-stages 5b and 5d are completely preserved at northwestern sections. Towards southeast, both the S1L1 and S1L2 were annexed by the subsequent paleosol development (S1S1 and S1S2) and the three paleosols (S1S1, S1S2, and S1S3) were partially welded. At the southeasternmost site, the three soil-forming events (S1S1, S1S2, and S1S3) repeatedly occurred in a single paleosol profile. The three observed orders of particle-size variations are interpreted to have imprinted important chronological and pedogenic signatures. First-order variations, i.e., a remarkable difference between the interglacial pedocomplex S1 and the glacial loess units (L1 and L2), implies that the S1 parent material was considerably finer in the source areas or/and the proximity to the source areas was much farther during interglacial period than during the preceding (L2) and following (L1) glacial periods. Second-order variation, i.e., the parenthetical trends in > 63 μm and < 10 μm fraction curves, might have resulted from the delayed response of the source material supplies to the climate changes. The third-order variations in < 10 μm fraction correspond well to the variations in frequency-dependent magnetic susceptibility, suggesting that pedogenically formed finer particles (i.e., < 10 μm fraction) and the associated ultra-fine paramagnetic minerals as expressed by the frequency-dependent susceptibility occurred only as a minor component of the < 10 μm fraction. The third-order variations seem to be obscured by soil welding and annexation at southeastern sections where the paleosols within the S1 were partially or completely welded. The laboratory data-indicated < 10 μm fraction peaks of the third-order and field-observed clay coatings on ped-faces, together with carbonate leaching and accumulation, in the paleosols within the S1 indicate occurrence of within-S1 material translocation. To sum up, it is unrealistic to reconstruct high-resolution climatic records from the S1 pedocomplex because a number of factors might have undermined the validity of the particle size as a winter monsoon proxy. These factors include weathering in the source areas, in situ post-depositional weathering and fine fraction translocation, and downward penetration of soil formation into underlying previously deposited materials on stable land surfaces.     

The solonetzic process in surface soils and buried paleosols and its reflection in the mineralogical soil memory

The development of the solonetzic process in paleosols buried under kurgans and in the modern surface soils has been studied on the basis of the analysis of the clay (<1 μm) fraction. The revealed changes in the textural differentiation of the soils and the mineralogical composition of the clay fraction during 4500 years are assessed from the viewpoint of the “memory“ of the solid-phase soil components. The mineralogical characteristics show that the solonetzic process in the modern background soil is more developed. The mineralogical approach allows us to reveal the long-term changes in the soil status; it is less useful for studying the effect of short-term bioclimatic fluctuations. In the latter case, more labile soil characteristics should be used. The mineralogical method, combined with other methods, becomes more informative upon the study of soil chronosequences. Our studies have shown that the data on the clay minerals in the buried paleosols may contain specific information useful for paleoreconstructions that is not provided by other methods.     

黄土的连续提取实验及Rb/Sr值意义

通过连续提取实验 ,将黄土和古土壤中元素的赋存状态分成六种形态 :水可溶态、可交换态、碳酸盐结合态、铁锰氧化物结合态、有机物结合态和残留态。结果表明 ,K和Rb等元素 ,主要赋存于残留态中 ,而Ca、Sr等元素主要赋存于碳酸盐结合态和残留态中。Sr在黄土和古土壤中的赋存状态明显与Ca的分布有关。在风化成壤作用中 ,碳酸盐的淋溶和含Ca硅酸盐矿物的分解 ,引起Sr的淋失 ,而Rb保持稳定。因此 ,Rb Sr值指示了黄土和古土壤遭受的淋溶程度 ,反映了黄土高原的降雨量 ,是夏季风强度变化的替代性指标