论煤层的加积方式

煤层成因是煤地质学的核心。煤层是一种沉积地层,它遵循沉积学、地层学、岩石学以及矿床学的基本规律,也有其特殊性,其成因并不同于煤的成因。传统煤地质学的核心观点是煤层由泥炭沼泽演化而成,其本质就是成煤物质的垂向加积。通过对煤层垂向和侧向加积的分析对比以及大面积稳定展布的厚煤层低自然伽马多峰现象、层理与条带结构等沉积特征的研究,认为成煤物质是机械沉积的,煤层像大多数沉积岩层一样是侧向加积形成的。对于厚煤层而言,多期侧向加积产生了次生垂向加积,其形成过程不是一个简单的、连续的、线性的垂向累加过程,而是一个复杂的、不连续的、非线性的侧向叠合过程,成煤物质是不连续的、多期多源的,厚煤层中普遍存在的夹矸便是其不连续的证据,同时厚煤层是穿时的。煤层侧向加积与较深水或海相沉积共生,是一个有机连续的整体,符合瓦尔特相律和古生态学原理,符合煤层厚度、形态多变及下伏地层沉积体系多种多样,也符合成煤物质超巨量工业富集、含煤地层灰色灰黑色、煤矿床质量优良的事实。     

Initiation of a multiple peat slide on Cuilcagh Mountain,Northern Ireland

In October 1998 a multiple peat slide occurred on the northern slopes of Cuilcagh Mountain, Co. Fermanagh, in response to a high‐magnitude rainfall event. Few peat slides have been recorded in Ireland, and a detailed field survey and investigation of the failure was undertaken within four weeks of the event. The morphological evidence indicated a distinct sequence of events which appeared to begin with the failure of a small segment of slope above a degraded transverse drainage ditch which was cut less than ten years previously. This segment of slope was no more than 42 m wide and 25 m long, with 0·7 m of peat overlying up to 0·5 m of a pale coloured clay, the latter containing small pipes and resting on the surface of a darker coloured loamy material. The failure surface was located at or near the base of the pale clay layer. Finite element software was used to model hydrological conditions within the upper segment of slope and to calculate factors of safety for different slope configurations including the presence or absence of a drain or a subsurface pipe. Using the peak shear strength of the pale clay, as determined in the laboratory, both the drain and subsurface pipes were required to obtain a factor of safety of 1·0 or less. Allowing for the uncertainties associated with the hydrological modelling of the pipes, it is suggested that the cutting of the drain and the hydrological impacts of its subsequent degradation are ultimately responsible for the failure. Copyright © 2001 John Wiley & Sons, Ltd.     

大气环境变化的泥炭地质档案

雨养泥炭沼泽是一种重要的泥炭沼泽类型,具有全球广泛分布的特点,其养分补给主要源于大气降水(包括雨、雪和空气尘埃).它是一个记录大气环境变化的积极的信息储备系统,记录有大气输入的海盐气溶胶、沙尘颗粒、酸沉降、重金属和有机污染物等信息.采用地质定年技术将泥炭深度剖面转化到年代坐标上,并结合泥炭生物地球化学指标检测分析,提取...     

Coastal Massachusetts pond development: edaphic,climatic, and sea level impacts since deglaciation

Kettle ponds in the Cape Cod National Seashore in southeastern Massachusetts differ in their evolution due to depth of the original ice block, the clay content of outwash in their drainage basins, and their siting in relation to geomorphic changes caused by sea-level rise, barrier beach formation, and saltmarsh development. Stratigraphic records of microfossil, carbon isotope, and sediment changes also document late-glacial and Holocene climatic changes.The ponds are separated into 3 groups, each of which follow different development scenarios. Group I ponds date from the late-glacial. They formed in clay-rich outwash, have perched aquifers and continuous lake sediment deposition. The earliest pollen and macrofossil assemblages in Group I pond sediments suggest tundra and spruce-willow parklands before 12 000 yr B.P., boreal forest between 12 000 and 10 500 yr B.P., bog/heath initiation and expansion during the Younger Dryas between 11 000 and 10 000 yr B.P., northern conifer forest between 10 500 and 9500 yr B.P., and establishment of the Cape oak and pitch pine barrens vegetation after 9500 yr B.P. Sedimentation rate changes suggest lowered freshwater levels between 9000 and 5000 yr B.P. caused by decreased precipitation on the Atlantic Coastal Plain. Lake sediment deposition began in the middle Holocene in Group II ponds which formed in clay-poor outwash. These ponds date from about 6000-5000 yr B.P. In these ponds sediment deposition began as sea level rose and the freshwater lens intersected the dry basins. The basal radiocarbon dates of these ponds and stable carbon isotope analyses of the pond sediments suggest a sea-level curve for Cape Cod Bay. Holocene topographic changes in upland and the landscape surrounding the ponds is reconstructed for this coastal area.Group III ponds in the late Holocene landscape of the Provincelands dunes originated as interdunal bogs about 1000 yr B.P. and became ponds more recently as water-levels increased. Peat formation in the Provincelands reflects climatic changes evident on both sides of the Atlantic region.This is the 8th in a series of papers published in this special AMQUA issue. These papers were presented at the 1994 meeting of the American Quaternary Association held 19–22 June, 1994, at the University of Minnesota, Minneapolis, Minnesota, USA. Dr Linda C. K. Shane served as guest editor for these papers.     

Climatic and topographic limits to the abundance of bog pools

On patterned peatlands, open water pools develop within a matrix of terrestrial vegetation (‘ridges’). Regional patterns in the distribution of ridge–pool complexes suggest that the relative cover of these two surface types is controlled in part by climate wetness, but landscape topography must also be an important controlling factor. In this paper, a functional model that relates relative cover of ridges and pools to climate and surface gradient was developed and tested. The model was formulated in terms of a water budget, based on the differential effects of ridges and pools on losses by evapotranspiration and subsurface flow. It predicts a positive relationship between surface gradient and ridge proportion, with a linear effect related to water supply and ridge hydraulic conductivity, modified at high ridge proportion by differences in evapotranspiration between ridges and pools. The limit to patterned peatland distribution occurs where the surface is completely covered by ridges. The model may be sensitive or insensitive to climate differences between localities, depending on whether hydraulic characteristics of ridge peat co‐vary with water supply. To distinguish between these alternative hypotheses, surface gradient and ridge proportion were surveyed along 20 transects in each of three localities in Scotland that differ threefold in net precipitation to pools. The results of the field survey served to reject the climate‐sensitive hypothesis, but were consistent with the climate‐insensitive hypothesis. Analysis of the residuals suggested that variation within localities was related more to topographic control of water supply than to ridge hydraulic conductivity or developmental stage. Hence, within this maritime climate region, the distribution of ridge–pool complexes and the relative abundance of pools are controlled mainly by topographic variables. Field surveys across both maritime and continental regions are required to confirm a subtle climatic effect that allows pools to occur on higher gradients in drier climates than in wetter climates. Further development and testing of the functional model will provide a stronger basis for assessing potential feedback between climate change, peatland surface structure and methane emission from pools. Copyright © 2006 John Wiley & Sons, Ltd.     

Sources and biodegradability of dissolved organic matter in two headwater peatland catchments at the Marcell Experimental Forest,northern Minnesota,USA

Where they are present in catchments, peatlands are a dominant source of dissolved organic matter (DOM) to surrounding waterways due, in part, to high production rates. Despite the preponderance of peatlands in northern latitudes and expected peatland vulnerability to climate change, little is known about peatland DOM degradation relative to a more comprehensive understanding of degradation when DOM is sourced from upland-dominated catchments. We compared DOM biodegradability of various sources of stream water in two catchments having peatlands (22%–33% of the area) surrounded by upland forests (70%–90% of the area, either deciduous or coniferous). We measured total organic carbon (TOC), and biodegradable dissolved organic carbon concentrations; bacterial respiration rates; streamflow; and upland runoff during and after snowmelt (March to June, 2009–2011). We also explored if DOM in upland runoff stimulated biodegradation of peatland-derived DOM (i.e., a priming effect), and if forest cover type affected DOM biodegradability. As expected, the peatlands were the largest sources of both water (72%–80%) and TOC (92%–96%) to the streams although more area in each catchment was in uplands (70%–90%). Several results were unexpected, yet revealing: (1) DOM from peatlands sometimes had the same biodegradability as DOM from uplands, (2) upland sources of DOM had negligible effects on biodegradability in the peatland and downstream, and (3) upland deciduous cover did not yield more degradable DOM than conifer cover. The most pronounced effect of upland runoff was dilution of downstream TOC concentrations when there was upland runoff. Overall, the effects of upland DOM may have been negligible due to the overriding effect of the large amount of biodegradable DOM that originated in bogs. This research highlights that peatland-sourced DOM has important effects on downstream DOM biodegradability even in catchments where upland area is substantially larger than peatland area.     

大型化综放开采煤层注水方案及参数确定

强调在大型化综放开采煤层中开设抬高中间巷进行煤层注水，其注水效率高，可一巷多用，防灾效果全面。结合算例，用有限元数值模拟方法模拟了在厚煤层中注水的过程，得到最小湿润范围准则为煤层厚度的1．5倍。分析了综放开采煤层注水工艺参数中注水压力、时间和钻孔间距与湿润范围的动态变化关系，给出了选取合理的注水工艺参数的方法。指出在大型化综放开采进行煤层注水，湿润时间充裕，同时，考虑到压裂并软化煤体，应采用较高的压力注水，此时，钻孔间距可扩大至35m。