The influence of vegetation composition on peat humification: implications for palaeoclimatic studies

Peat humification analysis is a widely used palaeoclimate proxy. However, recent studies combining humification with other proxies of mire surface wetness have identified inconsistencies between the records. We illustrate this inconsistency by comparing humification records with plant macrofossil profiles in three ombrotrophic bogs. Peat humification is a measure for organic decay and reflects changing palaeohydrological conditions and former vegetation composition. The resulting signal is considered to be a derived response to climate. However, even minor changes in the botanical composition of the peat may have a significant influence on humification measurements. The implications of this for palaeoclimate studies are discussed. The assumption that climate has been the major influence on variations in humification rests on the botanical composition being relatively homogeneous throughout the peat profile, and is therefore questionable. Consideration should be given to developing species-specific measures of humification and to testing the assumption that the major influence on peat humification is the surface wetness of the bog (and therefore climate).     

Replicability and variability of the recent macrofossil and proxy-climate record from raised bogs: field stratigraphy and macrofossil data from Bolton Fell Moss and Walton Moss,Cumbria, England

Replication of results is a basic tenet of science, but in palaeoecology this is very time-consuming and the ‘signal’ is subject to ‘noise’. The derivation of proxy-climate signals from ombrotrophic peat was carried out originally using samples from open peat faces where the stratigraphic relationships could be easily observed. Now that such sections are rare and often degraded there is a need to demonstrate that data can be replicated from core profiles. Ten short cores taken from two adjacent bogs have been analysed for macrofossils and show a coherent series of changes, which are also similar to previous profiles from the same sites. It is concluded that variation between profiles is slight and less than observations of present vegetation mosaics might suggest. Recommendations for a standard approach to fieldwork on raised bogs that emphasises the utility of subfossil pool layers are proposed and the need for a secure chronology is stressed. © 1998 John Wiley & Sons, Ltd.     

Hydrology and drainage of peatland

Peat is an accumulation of partially decomposed plants, chiefly mosses, herbs, and trees, to form a deposit called bog. Complete decomposition is primarily inhibited by a deficiency of oxygen induced by waterlogging. In the upper layers of raised bogs and in the so-called blanket bogs, acidity and very low levels of phosphorus may also contribute to impairing decomposition. Peat types have been classified into blanket, raised, and fen peat. Further subdivisions have been made on the basis of the plant composition and degree of decomposition. Blanket peat is so called because it covers the landscape, hill and valley. On the other hand, raised peats are confined to low-lying ground and valleys, and higher ground often protrudes through as islands of mineral soil ground. The blanket/raised/fen classification has relevance to hydrology and drainage, in particular to the mode of formation and to the type of drainage solution including outfalls. The nature of the plant composition and degree of humification have relevance chiefly to physical properties but especially permeability, bulk density, and moisture content, which also relate to hydrology and drainage. This article examines the formation of peat in a hydrological context and the drainage of peat deposits through the application of drainage theory to the peat and subpeat deposits, including glacial drift and bedrocks.     

Applications of Remote-Sensing Techniques in Peat Resource Investigations in Zoig■

The paper presents an example of the application of remote-sensing techniques in peat resource investiga-tions. The study was carried out in the Zoige region. The optimal imagery time (during October) and theoptimal band (MSS_7) of Landsat data were selected. The preferred images were processed optically and bycomputer and interpreted in a comprehensive way. And in-situ spectrum measurements and drilling verificationwere carried out.The identification signature of the peat bogs in Zoige was defined. The feature of the identifi-cation signature for peat was that the peat bog area showed a dark tone with lower reflectance in images of thefour MSS bands. The distribution range of peat bogs in the region was exactly located. The types of peat bogswere distinguished. The total peat area of 4038 km~(2) was defined with a total reserve of 5 billion m~3. The resultof the study indicates that the large-area, small-scale investigation of peat resources by use of satelliteremote-sensing data is an advanced method. by which the work efficiency can increase by about 20 times.     

The liquid limit of peat and its application to the understanding of Irish blanket bog failures

Catastrophic failures of blanket bogs, involving the escape and outflow of large volumes of semi-liquid basal peat, are well-known phenomena in Ireland but have only very rarely been reported from elsewhere in the world. Their precise causes and mechanisms are as yet unclear. The liquid limit (w _L) was identified as a potentially useful indicator of the susceptibility of peat to such failure because peat has extremely high natural water contents and, as an index property, w _L takes no account of the properties or structures of highly heterogeneous intact peat. However, the usual procedure for determining the w _L of peat is not fully standardised. Prepared samples will normally include potentially highly reactive particles of disrupted fibres and wood fragments that would not be present in such freshly disintegrated form in the field. This paper presents results from w _L determinations of peat obtained from the scar margins of three bog failures in northwest Ireland, using four different test procedures including a method involving wet-sieving of the peat to separate the humified <425-μm fraction for testing without incorporating artificially fragmented particles of fibres. The sampled peat was classified as H₈–H₁₀ according to the von Post humification scale. The fibre contents varied between the sites, but the ash contents were <3% in all but one test sample, and bulk densities (dry and field-wet) of the peat from all three sites were almost identical. w _L results from the wet-sieving method were 708–785%, compared with 633–980% from the standard method. The highest measured field water contents exceeded the wet-sieved w _L for all three of the field sites. Tests of cone penetration into intact peat cores demonstrated the influence of the reinforcing effect of in situ fibres. The results strongly suggest the need to adopt a fully standardised procedure for determining the w _L of peat. Additional shear vane measurements of intact and remoulded peat from a bog failure in Northern Ireland indicated a very high ‘strength sensitivity’. This leads to the suggestion that a slight disturbance of basal peat can lead to a loss of strength that rapidly propagates as local stresses change and cause further remoulding as water contents exceed w _L.     

Peat/coal type and depositional environment—are they related?

Four bogs in New Zealand were investigated in order to understand the relationship between peat type and depositional environment. This relationship is important because peat type translates into coal type, and coal types can ultimately be used to infer how and under what conditions the original peat bog formed. In our study, no correlation was found between peat type and depositional environment in the four bogs examined. Moreover, no correlation was found between peat type and either tectonic setting or climate. Water table level and degree of fluctuation are the only parameters which seem to have a good causative relationship on peat type.The bogs, Whangamarino, Moanatuatua and Kopouatai in the North Island and Sponge Swamp in the South Island, all have different depositional settings ranging from coastal plain, to fluvial-meandering and fluvial-braided river floodplain. We found no diagnostic peat types that would allow those different environments to be distinguished from studies of the peat. Data from other tropical and temperate climate peat bogs also support our contention that no diagnostic peat types can distinguish particular depositional settings. However, the level and variability of water table does have a correlation, one that is also seen in bogs elsewhere.From our observations, we infer that the validity of using maceral ratios (directly related to coal type) to indicate depositional environment should be questioned. At best, coal type only represents to what degree the original plant components were degraded, but not how they were degraded. To infer other parameters such as depositional environment, tectonic setting or climate, other data (e.g. distribution of surrounding sediment types, palynology, etc.) must be collected and assessed.     

浅钻技术在若尔盖地区泥炭调查中的应用

泥炭是一种具有多种用途的宝贵自然资源,泥炭中的有机碳储量是研究全球碳库变化及碳循环过程的重要参数。由于泥炭多分布于沼泽中,且泥炭松软含水量大的特性,对于泥炭深度的调查、获取用于测试泥炭原状样品的质量不高,导致泥炭碳储量评价仍存在不确定性和偏差。笔者等在典型泥炭形成地若尔盖沼泽湿地地区,开展了浅钻泥炭调查取样工作,通过在泥炭斑块边缘及中心两种不同沼泽湿地地层开展的试验,验证了轻便钻机在难进入的沼泽湿地的适应性,配套的振动冲击工艺可高质量的获得无扰动的泥炭样品,同时查明了泥炭层的厚度。通过试验初步探索了采用轻便钻机配套振动冲击钻进工艺进行泥炭调查取样的有效性。浅层取样钻探作为泥炭调查取样的一种直接有效的技术手段,可以有效地提高泥炭调查效率和精度,为准确评价泥炭储量数据提供可靠的钻探技术服务支撑。     

浅钻技术在若尔盖地区泥炭调查中的应用

泥炭是一种具有多种用途的宝贵自然资源,泥炭中的有机碳储量是研究全球碳库变化及碳循环过程的重要参数。由于泥炭多分布于沼泽中,且泥炭松软含水量大的特性,对于泥炭深度的调查、获取用于测试泥炭原状样品的质量不高,导致泥炭碳储量评价仍存在不确定性和偏差。笔者等在典型泥炭形成地若尔盖沼泽湿地地区,开展了浅钻泥炭调查取样工作,通过在泥炭斑块边缘及中心两种不同沼泽湿地地层开展的试验,验证了轻便钻机在难进入的沼泽湿地的适应性,配套的振动冲击工艺可高质量的获得无扰动的泥炭样品,同时查明了泥炭层的厚度。通过试验初步探索了采用轻便钻机配套振动冲击钻进工艺进行泥炭调查取样的有效性。浅层取样钻探作为泥炭调查取样的一种直接有效的技术手段,可以有效地提高泥炭调查效率和精度,为准确评价泥炭储量数据提供可靠的钻探技术服务支撑。     

10,000 years of climate control over carbon accumulation in an Iberian bog(southwestern Europe)

The northwest region of the Iberian Peninsula is home to a unique ecosystem of bogs,which are particularly sensitive to projected climate cha nge.In this context,the rate of carbon(C)accumulation in Chao de Veiga Mol.an intact raised bog,was analysed.Changes in the accumulation rate over the past10 millennia were determined in a peat core of 847 cm in depth,with a high mean rate of peat growth(11 yr cm^-1,0.09 cm yr^-1).An age-depth model was generated from 22 14C dates and fallout radionuclides.Chronological,stratigraphical and physico-chemical data confirmed the existence of a single cycle of peat formation throughout the Holocene and the formation of ombrotrophic peat 9500 years ago.The total mean C content was 50.2%,and over 10 millennia 583 kg C m^-2 accumulated at a mean rate of 35.3 g C m^-2 yr^-1,with a long-term(apparent)rate of carbon accumulation in the catotelm of59.9 g C m^-2 yr^-1.These values are much higher than reported for other Iberian peatlands and are amongst the highest documented for peatlands in the northern hemisphere.The dynamics of C accumulation and other measured parameters reveals important variations throughout the Holocene.They could be associated with the main climatic events described in the northern hemisphere and are highly consistent with models established for northern latitudes.The Chao de Veiga Mol raised bog is unique and of great potential value for carrying out high resolution palaeoenvironmental studies,especially in relation to regional and Iocal modulations in southern Europe.     

Testate amoebae as a proxy for reconstructing Holocene water table dynamics in southern Patagonian peat bogs

Testate amoebae are abundant and diverse in Sphagnum peat bogs and have been used extensively as indicators of past water table depths. Although these unicellular protists are widely dispersed with globally similar hydrological preferences, regional variations in communities demand region‐specific transfer functions. Here we present the first transfer function for southern Patagonian bogs, based on 154 surface samples obtained from transects in five bogs sampled in 2012 and 2013. Significant variance was explained by pH, electrical conductivity and, in particular, water table depth. Transfer functions for water table were constructed using weighted averaging and evaluated by cross‐validation and independent test sets. The optimal transfer function has predictive ability, but relatively high prediction errors given the wide range in sampled water tables. The use of independent test sets, as well as cross‐validation, allows a more rigorous assessment of model performance than most previous studies. For a subset of locations we compare surface and subsurface samples to demonstrate significant differences in community composition, possibly due to vertical zonation. Our results provide the first quantification of hydrological optima and tolerances for several rare species, which may include Southern Hemisphere endemics and pave the way for palaeohydrological reconstructions in southern Patagonian bogs.     

The occurrence of Laacher See Tephra in Pomerania, NW Poland

A millimetre-thick bed of highly vesiculated pumiceous clasts was found in two peat bogs in Pomerania (NW Poland). Their phonolitic composition confirms the correlation with the Laacher See Tephra (LST). Based on the various CaO-Na₂O-K₂O content, most of these clasts can be linked with the Lower Laacher See Tephra (LLST), and some with the Middle Laacher See Tephra B (MLST-B). ¹⁴C dates obtained on peat samples are in agreement with an Allered stratigraphic position of that tephra. In several localities in NW Poland, it was found that there was no occurrence of tephra in peat bogs. Thus the presence of the LST is restricted to the northwestern fringes of Pomerania.     

Occurrence and morphology of pyrite in Bulgarian coals

Coals with different degrees of coalification (ranging from lignite to anthracite) from seven Bulgarian coal basins have been investigated. The forms of pyrite and their distribution have been established. The types found are: massive pyrite, represented by the homogeneous, cluster-like and microconcretionary varieties; framboidal pyrite, appearing in inorganic and bacterial forms; euhedral pyrite, which is either isolated or clustered; anhedral pyrite, in its infilling and replacement varieties; and infiltrational pyrite, as a replacement or infilling mineral.Most of the forms of the euhedral, framboidal and massive pyrite developed during peat deposition. The anhedral replacement pyrite formed in the peat bed during early diagenesis. Infiltrational pyrite filled fractures and cleats formed during the diagenesis, catagenesis and metagenesis.Both similarities and differences with respect to the distribution of the pyrite types have been determined between coals of different ranks from Bulgarian coal basins. These differences are due to: the presence of Fe and S in the rocks adjacent to ancient peat bogs; the activities of ground and surface waters which brought Fe and S into the peat bogs; the geochemical character (pH and Eh) of the peat bogs and the sulphur bacteria development; and the tectonic situation during diagenesis, catagenesis and metagenesis.     

Late Holocene climatic history of northern Germany and Denmark: peat macrofossil investigations at Dosenmoor, Schleswig-Holstein, and Svanemose, Jutland

Plant macrofossil remains have been analysed from two raised peat bogs in northern Germany and Denmark. The quantified vegetation reconstructions of each profile were subjected to multivariate analyses to extract records of changing bog surface wetness (BSW), which are interpreted in these rain-fed bogs as being proxy climate signals. Age/depth models were constructed using radiocarbon dates and a number of drier and wetter phases were defined. The records both register cooler/wetter conditions around 2700, 1800 and 1400 cal. yr BP, and at the beginning of the Little Ice Age around AD 1250–1350. These rising bog water tables must have been reflected in poorer conditions for agriculture, and in particular near Dosenmoor where the profile records a catastrophic change to such conditions culminating at 2750–2600 cal. yr BP.     

早期煤化作用机制与有机质早期成烃演化

近年来，未熟和低熟油气田的发现、生物气藏的勘探和开发，极大地促进了对有机质早期转变的研究；而有机质早期转变机制的正确认识对于煤和干酪根中显微组分的成因、后期热演化都有着重要的影响。对早期煤化作用机制和有机质早期成烃作用的研究现状、进展及存在的问题进行了综述。     

Holocene fire regime changes from multiple-site sedimentary charcoal analyses in the Lourdes basin (Pyrenees,France)

One lake and three peat bogs from the Lourdes glacial basin (France) were used for macrocharcoal analyses and fire frequency reconstruction over the entire Holocene (11700 years). The chronology was based upon thirty-three 14C AMS dates. Comparison of the distribution of both CHarcoal Accumulation Rate (CHAR) and fire return intervals showed that charcoal accumulation significantly differs between the lake and the peat bogs, but that frequency calculation overcomes the disparity between these site types. A composite frequency was built from the four individual records to assess regional versus local variability and fire regime controls by comparisons with regional fire activity, Holocene climatic oscillations and vegetation history. The millennial variability can be depicted as follows: relatively high frequency between 8000 and 5000 cal a BP (up to 5 fires/500 yrs), relatively low frequency between 5000 and 3000 cal a BP (down to 0 fires/500 yrs), and an increase between 3000 and 500 cal a BP (up to 4 fires/500 yrs). From 8000 to 5000 cal a BP, fire frequency displays strong synchrony between sites and appears to be mostly driven by increased summer temperature characterizing the Holocene Thermal Maximum (HTM). On the contrary, during the last 3000 years fire frequency was heterogeneous between sites and most probably human-driven. However, higher frequency at the millennial scale during the mid-Holocene strongly suggests that the perception of human-driven fire regime depends on the strength of natural controls.     

泥炭沉积中植硅体对环境指示的意义--以吉林敦化泥炭剖面为例

泥炭地作为环境变化的敏感带,成为当前环境气候研究的热点之一.植硅体的抗腐蚀、耐高温、个体小、产量高的特点为第四纪环境变迁的研究提供了有效途径.相比孢粉分析而言,植硅体在提高分辨率和恢复局部区域环境方面体现了其优越性.对泥炭沉积中的植硅体进行了分析,初步证实植硅体对重建泥炭地古环境变迁模式起着重要的作用,对提高古气候变化的分辨率有很大的帮助.     

Some peculiarities of holocene processes in Western SiberiaZur holozängeschichte der westsibirischen torfmooreQuelques singuliarités des processus holocènes sur le territoire de la Sibérie occidentale

The authors deal with problems of the origin of peat in the territory of the West Siberian Lowland where Holocene processes are sufficiently widespread to be representative of this world-wide phenomenon. Here, for example, are found the most extensive peat bogs of the Earth. The authors deal with the stratigraphy of these peat bogs and the reconstruction of Holocene conditions in the West Siberian Lowland. The development of peat bogs has considerably modified landscape features since the retreat of the last glaciation, i.e., during the last 10,000 to 11,000 years. The peat bogs began to develop simultaneously in thousands of depressions after the ice cover had melted. Later they merged into vast peaty bog regions. Without any intervention by man the peat bogs will cover all of Western Siberia in the course of several thousands of years. The development of extensive peat bogs is due to an irregular advance of floods on Siberian rivers which leads to a rise in the water level on tributaries of great rivers and to a retardation of the discharge of flood waves In the conclusion the authors point to the problems of economic use of swampy regions and to questions of land reclamation that must be answered before economic use of the territory (mainly in connection with extensive oil and gas deposits in these regions) can be fully effective.     

泥炭沼泽的演化及其机制

泥炭沼泽的演化普遍存在,演化的实质是在成因因素有利的配合下,沼泽植物群落发生了变化乃至更替。根据泥炭植物残体分析和煤层的煤岩、煤化学研究,可以了解泥炭沼泽的演化和形成煤层的原始泥炭沼泽的演化。      

Geochemistry of Phosphorus and Origin of Phosphorites: Communication 2. Sources of Phosphorus in Continents and Genesis of Marine Phosphorites

It is shown that terrigenous apatite in soil, weathering crusts, and low peat bogs of humid zones is transformed into hydrogenous forms and solutions. In arid environments, apatite is transported to terminal discharge basins and transformed within diagenetic mud. Continental blocks are the main source of phosphorus in epicontinental and marginal seas. It originates from two sources (continents and seawater) in oceans. The role of biogenic factor in phosphorus geochemistry is significant, variable, and manifested at different stages of phoshogenesis.     

新疆准东煤田西黑山勘查区西山窑组煤相特征

以新疆准东煤田西黑山勘查区西山窑组煤层为研究对象,采用成因参数法和煤相图解方法,同时结合沉积学方法进行煤岩、煤相分析,探讨泥炭沼泽类型及其演化规律。煤相参数研究显示,B1、B11、B21和B2煤层煤相总体为偏干燥的湿地森林和湿地森林沼泽,B12、B3和B4-5煤层总体为干燥森林沼泽;垂向上B1、B2、B3、B31和B6煤表现出显著的由湿地森林沼泽或偏干燥的湿地森林沼泽向干燥森林沼泽演化,反映覆水程度逐渐变浅,泥炭沼泽表面逐渐趋于干燥,表明成煤期泥炭堆积速率与基底的相对沉降速率持平或略高于基底沉降速率。