Tertiary coal geology and stratigraphy of the Port Phillip Basin,Victoria

Results from coal‐exploration drilling in the onshore part of the Port Phillip Basin, Victoria, have established stratigraphic and age correlations of the Lower Miocene Werribee Formation brown coal deposits at Bacchus Marsh to similar brown coals at Altona. The coal deposits occur in a northwest‐southeast structural depression (the Parwan Trough) that appears to be a southeast continuation of the Ballan Graben. Recent drilling for potential coal‐bed methane in the trough has provided new data on the deeper stratigraphy not penetrated by earlier drilling, including recognition of an Upper Cretaceous to Eocene Yaloak Formation coal‐bearing interval, similar to the Anglesea area, Ballan Graben and Lal Lal Basin. Up to 200 m of coal‐bearing sediment and minor volcanics underlie the Miocene coal measures. A marine facies transition takes place between the Miocene coal swamps of the Parwan Trough, through barrier sands west of Werribee, to carbonate facies near Geelong. To the south beneath Port Phillip Bay, a similar transition probably occurs between coal swamps of the Parwan Trough and fully marine carbonate environments of the contiguous Sorrento Graben. The palaeogeographical reconstructions suggest a similar coal‐to‐carbonate facies transition as in the adjacent onshore Gippsland Basin.     

Impact of multi-purpose aquifer utilisation on a variable-density groundwater flow system in the Gippsland Basin, Australia

The Latrobe aquifer in the Gippsland Basin in southeastern Australia is a prime example for emerging resource conflicts in Australian sedimentary basins. The Latrobe Group forms a major freshwater aquifer in the onshore Gippsland Basin, and is an important reservoir for oil and gas in both onshore and offshore parts of the basin. The Latrobe Group and overlying formations contain substantial coal resources that are being mined in the onshore part of the basin. These may have coal-seam-gas potential and, in addition, the basin is considered prospective for its geothermal energy and CO₂ storage potential. The impacts of groundwater extraction related to coal-mine dewatering, public water supply, and petroleum production on the flow of variable-density formation water has been assessed using freshwater hydraulic heads and impelling force vectors. Groundwater flows from the northern and western edges towards the central part of the basin. Groundwater discharge occurs mainly offshore along the southern margin. Post-stress hydraulic heads show significant declines near the petroleum fields and in the coal mining areas. A hydrodynamic model of the Latrobe aquifer was used to simulate groundwater recovery in the Latrobe aquifer from different scenarios of cessation of groundwater and other fluid extractions.     

Inertinite-rich Tertiary coals from the Zeya–Bureya Basin, Far Eastern Russia

Selected Tertiary coals from the Zeya–Buryea Basin, Far Eastern Russia, were investigated for aspects of their coal type, rank, depositional environment and post-depositional history. The coals have been examined in outcrop (lithotype logging), microscopically (maceral, reflectance and fluorescence), and geochemically (proximate analysis).Two laterally extensive coal-bearing horizons occur: one of Palaeocene age and the other of early Miocene age. The Palaeocene coals were investigated in active open-cut mines at Raichikhinsk and Yerkovtsi and the early Miocene deposit in an abandoned open-cut mine at Cergeyevka.Palaeocene coals at Raichikhinsk and Yerkovtsi were indistinguishable from each other macroscopically, microscopically, and geochemically. The deposits were sufficiently coalified that brightness logging could be undertaken. Dull coals, with numerous fusainous wisps, were dominant. Four dulling-up sequences, which represent stacked peat deposits, were observed at Raichikhinsk. At Yerkovtsi, only a small section of the middle of the seam, which was mostly dull and muddy coal, was investigated. Petrographically, these coals were dominated by inertinite group macerals, which is unusual in non-Gondwanan coals and rare in the Tertiary. Rank classification was problematic with volatile matter (VM) content of vitrain (daf), macroscopic appearance, and microscopic textures suggesting subbituminous B rank, but carbon content, moisture content and specific energy indicating a lignite rank.Notwithstanding complications of rank, estimates of the maximum-range burial depths were calculated. Taking the VM (daf) content of vitrain as 48%, burial depth estimates range from 900 m for a high geothermal gradient and long heating time to a maximum of 3300 m for a low geothermal gradient and short heating time. These estimates are maxima as the coal rank may be lower than implied by the VM.The Cergeyevka deposit is a soft brown coal. Limited sampling of the upper-most portion indicated a high moisture content (75% daf) and an unusual, hydrogen-rich geochemistry. Lack of identifiable liptinites using either reflected light or fluorescence microscopy suggested a significant bituminite component. Otherwise, the coals appear to be typical for the Tertiary. An estimate of 125 m maximum burial depth was obtained using the bed-moisture content of the coal, which is around the present burial depth.Comparison of present-day thicknesses with inferred burial depths suggests that at least 500 m of section is missing between the Palaeocene coals and the early Miocene coals.Palaeoenvironmental considerations suggest that fire played a significant role in the accumulation of the peats at Raichikhinsk and Yerkovtsi. At Cergeyevka, peat accumulation ended by drowning of the mire.Two tuff beds were recognised within the seam at Raichikhinsk and one in the seam at Yerkovtsi. Correlation of the tuff beds is uncertain but they should prove useful in regional coal seam correlation and interpreting coal depositional environments. Geochemical analysis by XRF was complicated by high loss-on-ignition (LOI) values. Despite extensive alteration, an acid igneous source is implied from the presence of free quartz and TiO₂/Al₂O₃ ratios of 0.02 to 0.05.     

Geological note: New field evidence resolving the relationship between the Grampians group and the Rocklands Rhyolite,western Victoria

The Rocklands Rhyolite is a latest Silurian to Early Devonian sequence of silicic ignimbrite, lava, volcanic sedimentary rocks and dykes in western Victoria. These volcanic rocks lie west of the Grampians Ranges, which consist of a thick succession of quartz sandstone of presumed Silurian age called the Grampians Group. The previously unresolved stratigraphic relationship between these two sequences of rocks is clarified by an exposed contact between steeply dipping Grampians Group cut by quartz veins, and overlying undeformed rhyolite. The implications of this relationship are that the Grampians Group is older than the Rocklands Rhyolite and that parts of the sandstone succession were locally deformed prior to volcanism. Furthermore, other outlying areas of sandstone and rhyolite, previously correlated with the Grampians Group and Rocklands Rhyolite, respectively, display different timing relationships and are proposed to be significantly younger.     

ON MANGANIFEROUS FORMATIONS AND THE METALLOGENY OF MANGANESE,PAPER I. VOLCANOGENIC-SEDIMENTARY MANGANIFEROUS FORMATIONS

The article describes Carboniferous and Lower Liassic coal measures in Franz Josef Land, and a "2-ft coal bed" at the base of the Carboniferous motley sandstones observed by Fisher in Cook Cliffs at the south end of Prince George Land. Until recently the Cook Cliffs coal was identified by Dibner as "Paleozoic redeposited in Upper Triassic time." Later Dibner reassigned the coal and related beds to the Upper Triassic. Some doubt on this age is cast by the fact that the only coals on Spitzbergen are Lower Carboniferous. Ye. M. Andreyeva studied the coal's spores and found only Lower and Middle Carboniferous species. Traveling southeast of Wilczek Land in 1935, Yermolayev recovered coals he believed to be Paleozoic. Based on these finds, there is a strong likelihood of Paleozoic coals on Franz Josef Land. The Upper Triassic Vasil'yevsk Formation contains Noric to Rhaetic plants and spores. At Goristyy Cape (Champ Island) two brown coals occur; one is 1 m thick; 55 m higher is a 2-m bed coked at the top by an overlying basalt flow. The petrography of the coals is discussed. The Tegetthof Formation, based on its plant fossils, is Lower Liassic, compatible with sections on Spitzbergen. Next higher are Aalenian siltstones, Bathonian and sandy limestones with Volgian clams. Still higher are Lower Cretaceous volcanics with intercalated sandstones, shales and coals, divisible into the Tikhaya Cove Formation and Salisbury Formation. Altogether there are 13 coal beds in Franz Josef Land, ranging from Carboniferous up into the Lower Cretaceous (with 9 coal beds). Interesting petrographic details are included.—B. N. Cooper.     

Structural evolution of the Early Cretaceous depocentres,Otway Basin,Victoria

The dominant control on the (transition between) depositional settings of the Crayfish Group of the Otway Basin in Victoria, Australia has been determined. The study first involved seismic mapping of six stratigraphic units within the Early Cretaceous, continental Crayfish Group. The resulting 3D structural model was used to identify major Early Cretaceous depocentres, and to determine which Crayfish Group sediments are restricted to individual rift depocentres and which are more widespread as a result of inter-connectivity of the basin. Five structural cross-sections were then constructed across each major depocentre of the basin; these were balanced and restored, and missing section estimated, in order to test the validity of the structural interpretations. This also enabled analysis of differing extensional rates within each depocentre and the calculation of the cumulative displacement of each major bounding fault. Results show that displacement rate, growth and linkage of the faults, as well as the amount of subsidence within the depocentres, had a significant effect on the distribution and development of the major facies within the Crayfish Group. The Casterton Formation and Sawpit Shale equivalent/McEachern Sandstone were restricted to rapidly subsiding, structurally controlled depocentres in the west, while the succeeding Sawpit Sandstone equivalent was deposited within the same depocentres, across the intervening structural highs and in the eastern part of the basin where depocentres had just begun to form. The Pretty Hill Formation shows a similar distribution pattern, while the overlying fine-grained Laira Formation also drapes structural highs but is replaced in the east by coarser-grained sediments of the upper Pretty Hill Formation. Extension was locally up to 21% in the central Otway Basin but was much less in the eastern Otway Basin.     

沁水盆地石炭——二叠纪含煤岩系高分辨率层序地层及聚煤模式

晋东南沁水盆地的煤层气储层主要是石炭-二叠系煤层,其厚度变化明显受控于当时的沉积环境及层序地层格架。本文对该盆地含煤岩系的太原组和山西组进行了高分辨率层序地层分析,并探讨了主采煤层15号和3号煤层在层序地层格架下的分布模式。以区域性分布的与下切谷砂岩共生的间断面、不整合面、海侵方向转换面、下切谷砂岩底面、由深变浅-再由浅变深的沉积相转换面以及共生的古土壤层为界,将含煤岩系划分为3个三级复合层序和9个四级层序。15号厚煤层和3号厚煤层位于三级海侵(泛)面附近,前者形成于障壁——潟湖及滨外陆棚沉积环境,较低的泥岩堆积速率与较慢的可容空间增长速率相平衡;后者形成于三角洲平原分流间湾环境,较高的泥炭堆积速率与较高的可容空间的增长速率相平衡。太原组的以“根土岩——煤层——海相石灰岩”旋回为代表的四级层序中的煤层可能形成于“海相灰岩层滞后时段”,即从海平面抬升到陆棚之上到碳酸盐岩真正沉积下来之前的时段,因为缓慢的海平面抬升速率与泥炭堆积速率保持较长时间的平衡,从而聚集了厚层的泥炭/煤层。     

Geological note: Pyro‐intrusive veins in the northeastern Sydney Basin

Stratigraphic and sedimentological investigation of the interglacial succession within the Cryogenian-aged Umberatana Group of the Northern and Central Flinders Ranges reveals a complex array of sedimentary successions lying between the Sturtian and Marinoan glacial deposits. The Sturtian–Marinoan Series boundary was first defined from the Adelaide area at the uppermost contact of the Brighton Limestone. In the Northern Flinders Ranges the Sturtian–Marinoan Series boundary has been positioned at the uppermost contact of the Balcanoona Formation, which is thought to correlate with the Brighton Limestone. In the Northern Flinders Ranges a major unconformity separates the Sturtian and Marinoan-aged sedimentary successions (Nepouie–Upalinna Subgroups). In moderately deep marine depositional settings, this submarine unconformity is located at the base of the Yankaninna Formation where erosion has deeply incised (up to 300 m) into the underlying Tapley Hill Formation. In shallower marine settings the unconformity is found at the base of the Weetootla Dolomite. In very deep water depositional settings this unconformity is not recognised, and the Yankaninna Formation appears to conformably overlie the Tapley Hill Formation suggesting that this erosional feature is restricted to shallow and moderately deep depositional settings. This unconformity presents a regionally persistent chronostratigraphic marker horizon, which reliably marks the Sturtian–Marinoan Series boundary at the base of the Yankaninna Formation from shallow shelfal to deep-water basinal settings throughout the Northern Flinders Ranges. In the Central Flinders Ranges the post-Sturtian glacial stratigraphy records a very similar depositional record to that observed in the Northern Flinders Ranges. In the Central regions the Tapley Hill Formation is overlain by deep-marine carbonates and calcareous shales of the Wockerawirra Dolomite and Sunderland Formations, respectively. The base of the Wockerawirra Dolomite is found to be in erosional contact with the underlying Tapley Hill Formation. This stratigraphic relationship, together with lithological similarities, indicates the Wockerawirra Dolomite and Sunderland Formation of the Central Flinders Ranges are lateral correlatives of the Yankaninna Formation of the Northern Flinders Ranges. The regional nature of the Sturtian–Marinoan unconformity in the Adelaide Geosyncline suggest the possible existence of a glacio-eustatic event that may correlate with glacials/glaciation elsewhere on the Earth during the Cryogenian.     

Hydrocarbon genesis of Jurassic coal measures in the Turpan Basin, China

A typical case of coal-derived oils in China, i.e. the crude oils from the Middle-Lower Jurassic coal measure strata in the Turpan Basin, is presented. By means of oil-source correlation, it is confirmed that low maturity crude oil in the Shengjinkou oil field is derived from the coal-bearing Qiketai Formation of Middle Jurassic age, a brackish lacustrine sediment. Mature crude oils in the Qiketai oil field, and in well Taican 1, are sourced from the Badaowan Formation of Lower Jurassic age, which contains coal seams as thick as 100 m. Results show that commercial accumulations of liquid crude oils can be generated from coals and coal measure strata containing high volatile coal of bituminous rank. Despite unfavourable types of source material, the total hydrocarbon-generating potential can be great due to the unusual abundance of organic matter.     

Organic geochemical study of sequences overlying coal seams; example from the Mansfield Formation (Lower Pennsylvanian), Indiana

Roof successions above two coal seams from the Mansfield Formation (Lower Pennsylvanian) in the Indiana portion of the Illinois Basin have been studied with regard to sedimentary structures, organic petrology and organic geochemistry. The succession above the Blue Creek Member of the Mansfield Formation is typical of the lithologies covering low-sulphur coals (< 1%) in the area studied, whereas the succession above the unnamed Mansfield coal is typical of high-sulphur coals (>2.%). The transgressive-regressive packages above both seams reflect the periodic inundation of coastal mires by tidal flats and creeks as inferred from bioturbation and sedimentary structures such as tidal rhythmites and clay-draped ripple bedforms. Geochemistry and petrology of organic facies above the Blue Creek coal suggest that tidal flats formed inland in fresh-water environments. These overlying fresh water sediments prevented saline waters from invading the peat, contributing to low-sulphur content in the coal. Above the unnamed coal, trace fossils and geochemical and petrological characteristics of organic facies suggest more unrestricted seaward depositional environment. The absence of saline or typically marine biomarkers above this coal is interpreted as evidence of very short periods of marine transgression, as there was not enough time for establishment of the precursor organisms for marine biomarkers. However, sufficient time passed to raise SO₄²⁻ concentration in pore waters, resulting in the formation of authigenic pyrite and sulphur incorparation into organic matter.     

Developmental geology of coalbed methane from shallow to deep in Rocky Mountain basins and in Cook Inlet–Matanuska basin, Alaska, U.S.A. and Canada

The Rocky Mountain basins of western North America contain vast deposits of coal of Cretaceous through early Tertiary age. Coalbed methane is produced in Rocky Mountain basins at depths ranging from 45 m (150 ft) to 1,981 m (6,500 ft) from coal of lignite to low-volatile bituminous rank. Although some production has been established in almost all Rocky Mountain basins, commercial production occurs in only a few. Despite more than two decades of exploration for coalbed methane in the Rocky Mountain region, it is still difficult to predict production characteristics of coalbed methane wells prior to drilling. Commonly cited problems include low permeabilities, high water production, and coals that are significantly undersaturated with respect to methane. Sources of coalbed gases can be early biogenic, formed during the early stages of coalification, thermogenic, formed during the main stages of coalification, or late stage biogenic, formed as a result of the reintroduction of methane-generating bacteria by groundwater after uplift and erosion. Examples of all three types of coalbed gases, and combinations of more than one type, can be found in the Rocky Mountain region. Coals in the Rocky Mountain region achieved their present ranks largely as a result of burial beneath sediments that accumulated during the Laramide orogeny (Late Cretaceous through the end of the Eocene) or shortly after. Thermal events since the end of the orogeny have also locally elevated coal ranks. Coal beds in the upper part of high-volatile A bituminous rank or greater commonly occur within much more extensive basin-centered gas deposits which cover large areas of the deeper parts of most Rocky Mountain basins. Within these basin-centered deposits all lithologies, including coals, sandstones, and shales, are gas saturated, and very little water is produced. The interbedded coals and carbonaceous shales are probably the source of much of this gas. Basin-centered gas deposits become overpressured from hydrocarbon generation as they form, and this overpressuring is probably responsible for driving out most of the water. Sandstone permeabilities are low, in part because of diagenesis caused by highly reactive water given off during the early stages of coalification. Coals within these basin-centered deposits commonly have high gas contents and produce little water, but they generally occur at depths greater than 5,000 ft and have low permeabilities. Significant uplift and removal of overburden has occurred throughout the Rocky Mountain region since the end of the Eocene, and much of this erosion occurred after regional uplift began about 10 Ma. The removal of overburden generally causes methane saturation levels in coals to decrease, and thus a significant drop in pressure is required to initiate methane production. The most successful coalbed methane production in the Rocky Mountain region occurs in areas where gas contents were increased by post-Eocene thermal events and/or the generation of late-stage biogenic gas. Methane-generating bacteria were apparently reintroduced into the coals in some areas after uplift and erosion, and subsequent changes in pressure and temperature, allowed surface waters to rewater the coals. Groundwater may also help open up cleat systems making coals more permeable to methane. If water production is excessive, however, the economics of producing methane are impacted by the cost of water disposal.     

库车前陆盆地前渊带层序地层分析--以白垩系卡普沙良群为例

库车前陆盆地的白垩系由卡普沙良群(自下而上包括亚格列木组、舒善河组、巴西盖组)和巴什基奇克组组成.盆地北部克孜勒努尔沟的白垩系亚格列木组和巴什基奇克组底部均发育一大套泥石流沉积,表明白垩系卡普沙良群为一期构造活动幕的产物,为一个完整的二级层序,根据沉积演化特征可将其细分为7个三级层序.亚格列木组与舒善河组之间,扇三角洲平原相突变为滨浅湖相沉积,且舒善河组滨岸沙坝微相持续稳定发育,反映前陆盆地楔顶带的发育抑制了构造活动期源于造山带的粗碎屑的供给,使前渊带的沉积物供给速率趋于稳定.此外,克孜勒努尔沟卡普沙良群地层厚度远大于前缘隆起带,与上、下地层呈整合或平行不整合接触.研究表明,克孜勒努尔沟卡普沙良群为一套临近造山带的前渊带沉积.     

Architecture and depositional development of the Eocene deep‐marine Morillo and Coscojuela Formations,Aínsa Basin,Spain

The Aínsa Basin of northern Spain contains a deep‐marine succession comprising up to 24 sandstone bodies separated by thick marl‐rich units. A detailed analysis of nine outcrops (>900 m of sediment profiles) from the Morillo Formation of the San Vicente Group, from the upper part of the basin succession, has enabled a reappraisal of the unit. Within the Morillo Formation, sediment transport was to the NW, and a range of environments are recognized including channels, lobes and pelagic deposits. The overlying Coscojuela Formation, which partly cuts into the Morillo Formation, shows W‐directed palaeocurrents in its proximal reaches, with flows being deflected to the N along an adjacent slope. Destabilization of the adjacent carbonate platform resulted in a significant input of carbonate material into the flow. The final phases of sedimentation within the Aínsa Basin were more complex than previously suspected, probably as a result of a combination of factors, including tectonic activity, resulting in basin narrowing due to anticlinal growth, as well as encroachment and/or destabilization of the adjacent regional carbonate platforms. Copyright © 2013 John Wiley & Sons, Ltd.     

阳泉矿区含煤地层沉积环境及其对煤层厚度分布控制

阳泉矿区煤系地层形成于海陆交互相的过渡环境,其煤层的形成、赋存、厚度变化、分布均受沉积环境的控制和影响。根据分析成煤环境、预测煤层赋存变化情况,为煤炭资源补勘和开采生产提供指导     

新疆西部乌依塔克组的时代

通过对新发现于新疆塔里木盆地西部上白垩统乌依塔克组有孔虫化石的时代分析，认为该组的时限为晚上伦期—赛诺期，综合分析各类化石的时代特征，本区土伦阶和赛诺阶的界线应划在Ｍｉｇｒｏｓ－Ａｍｍｏｂａｃｕｌｉｔｅｓ组合和Ｐａｒａｒｏｔａｌｉａ－Ｎｏｎｉｏｎｅｌｌａ组合之间。     

青藏高原南部乌郁盆地渐新世—上新世地层沉积相分析

青藏高原南部乌郁盆地是欧亚与印度板块碰撞以来冈底斯山隆升最具代表性的盆地之一,也是青藏高原南部较大的新生代残留盆地之一。沉积盆地中保存着完整的渐新世—早更新世连续沉积记录,自下而上由古新世—始新世林子宗群（典中组、年波组和帕那组）、渐新世—中新世日贡拉组、中新世芒乡组、来庆组、上新世—早更新世乌郁群（乌郁组、达孜组）,总厚度大于4180m。林子宗群为一套中—酸性钙碱性火山岩系,夹紫红色砂岩、砾岩及粉砂岩。日贡拉组主要为紫红色砂岩、砾岩,夹少量火山熔岩及酸性火山凝灰岩,为一套山间盆地沉积。芒乡组为灰色、深灰色泥岩、砂岩,夹煤和油页岩,为湖泊相—前三角洲相—沼泽相。来庆组为一套褐色安山岩、火山碎屑岩。乌郁组是一套碎屑岩,颜色呈灰色、灰褐色,夹煤及油页岩,为山间盆地辫状河—湖泊—沼泽沉积。达孜组是一套黄褐色砾岩、砂砾岩、砂岩,夹少量泥岩,发育铁质结核,为辫状河沉积。沉积相分析表明具有明显的古新世—始新世林子宗群（典中组、年波组和帕那组）、渐新世—中新世日贡拉组—芒乡组、中新世来庆组—上新世乌郁组、上新世—早更新世达孜组四个阶段式隆升—剥蚀过程。从芒乡组的潮湿炎热的气候转变为乌郁组的干燥凉爽,显然与青藏高原隆升密切相关。乌郁盆地渐新世—早更新世沉积相分析对于研究青藏高原隆升和油气等能源均具有重要意义。      

新疆吐哈盆地中、下侏罗统含煤岩系层序地层及古地理

在吐哈盆地中、下侏罗统含煤岩系层序地层分析的基础上,对聚煤期古地理特征及其与聚煤作用的关系进行了研究。结果表明,吐哈盆地中、下侏罗统含煤岩系形成于河流-三角洲-湖泊沉积体系,其中共发育4个三级层序,分别对应于八道湾组、三工河组、西山窑组一、二段和三、四段。吐哈盆地从层序Ⅰ到层序Ⅳ,先后经历了沼泽（层序Ⅰ）-湖泊（层序Ⅱ）-沼泽（层序Ⅲ）-湖泊（层序Ⅳ）过程。在对应于最大湖泛面的湖侵体系域末期和高位体系域早期,较快的可容空间增加速率与泥炭堆积速率相平衡,从而有利于厚煤层的堆积。煤层厚度、碳质泥岩厚度与砂砾岩含量呈负相关关系,即砂砾岩含量越少,煤和碳质泥岩厚度越大;地层厚度300～500 m（层序Ⅰ）和400～550m之间（层序Ⅲ）时,煤层厚度最大,说明有利于煤和碳质泥岩聚集的环境是沉降速率中等、陆源碎屑供给相对较少的三角洲间湾、湖湾以及下三角洲平原环境,层序Ⅰ和层序Ⅲ的聚煤中心如艾维尔沟、柯尔碱、桃树园、七泉湖、柯柯亚、鄯善、艾丁湖、沙尔湖、大南湖和三道岭等均属于这类环境。     

Delineation of the distinctive nature of tertiary coal beds

Floral character in mires has changed progressively through time. In the Carboniferous, pteridophytes, sphenophytes and lycophytes were dominant but by the Permian gymnosperms were an important component of mire flora. During the early Mesozoic gymnosperms remained the characteristic mire vegetation, together with pteridophytes, and conifers became dominant during the Jurassic. Cretaceous and Paleocene vegetation are similar, with taxodiaceous flora being important in mire vegetation. From the Eocene onwards, however, angiosperms were increasingly dominant in mire communities and in the Miocene herbaceous vegetation began to play a significant role. Together with these changes in floral character at least three aspects of coal character also appear to vary sequentially with time and are distinctive in the Tertiary: (1) proportions and thickness of vitrain banding, (2) coal bed thickness and (3) proportions of carbonised material. A compilation has been made of data from the coal literature comparing older coals with those of the Tertiary, in order to give a perspective in which to examine Tertiary coals. It was found that only Tertiary coals contain significant proportions of coal devoid of vitrain bands. In addition, Tertiary coals are the thickest recorded coal beds and generally contain low percentages of carbonised material (many less than 5%) as compared to older coals. It is interesting to note that Paleocene coal beds are similar to Cretaceous coals in that they tend to be thinner and contain higher proportions of carbonised material than do younger Tertiary coals.The absence of vitrain bands in some Tertiary coal beds is thought to result from the floras dominated by angiosperms, which are relatively easily degraded as compared to gymnosperms. The thickness of Tertiary coals may be related to an increase in biomass production from the Carboniferous through to the Tertiary, as plants made less investment in producing lignin, an energy-intensive process. In addition, with less lignin in plants, easier degradation of biomass may have facilitated nutrient recycling which, in turn, led to greater biomass production. Increased biomass production may have also ‘diluted’ the carbonised material present in some Tertiary peats, leading to lower proportions in the coal. Another possible cause of decreased carbonised components in Tertiary coal is that decreasing lignin content resulted in decreased charring during fires, as lignin is particularly prone to charring. A third possibility is that the carbonised component of peat may be concentrated during coalification so that Tertiary coals, generally of lower rank than Mesozoic or Paleozoic coals, contain a smaller fraction of carbonised plant material. It is not at present clear which of these mechanisms may have affected carbonised material in peat and coal but it is clear that lignin type and content has had an important role in determining peat and coal character since the Paleozoic.     

四川资中铁佛场普查区须家河组沉积环境与聚煤作用

以大量钻孔岩心资料为基础,对资中铁佛场普查区须家河组沉积环境进行了分析,在须家河组共识别出4个三级层序,分别对应一段、二—三段、四—五段、六段,其层序特点为:低位体系域主要为河道砂岩沉积,几乎没有煤层发育;湖侵和高位体系域主要发育湖泊三角洲相,在滨岸沼泽和分流间湾环境成煤,且高位体系域煤层发育相对较厚、较多。研究认为区内主要可采煤层(高炭、下元炭煤层)形成于滨岸沼泽和受河流控制为主的湖滨三角洲环境。     

广西合山晚二叠世碳酸盐岩型煤系层序地层分析

广西合山煤田晚二叠世合山组是在浅水碳酸盐台地背景下形成的典型的碳酸盐岩型含煤岩系 ,其沉积环境有滨外陆棚、生物礁、开阔台地、潮坪和泥炭沼泽等。在包括合山组和大隆组在内的整个晚二叠世地层中 ,可以识别出5个层序界面 ,并可根据这些层序界面将区内上二叠统划分为 4个层序。层序 从合山组底面到合山组下段顶部的四 下 煤层底板硅质岩层之底面 ;层序 包括从四 下 煤底板到四 上 煤底板的一套地层 ;层序 为从四 上 煤层底板到二煤层之下铝土质泥岩底板的序列 ;层序 包括从合山组二煤层之下铝土质泥岩底板到大隆组之顶。其中层序 、层序 和层序 厚度在合山煤田范围内变化较大 ,说明受盆地基底沉降作用控制强烈 ,层序 则表现为多次的煤层-石灰岩旋回性 ,并且在合山煤田甚至桂中地区稳定分布 ,说明可能主要受全球海平面变化控制。与滨海平原靠陆一侧的冲积体系的陆源碎屑岩含煤岩系不同 ,陆表海碳酸盐岩型煤系三级层序中的最大海泛带底部以该层序中向上变薄至最薄的一层煤的底面为代表 ,如研究区三 中 煤层底面即为层序 中的最大海泛带底部 ,其下为三级层序中的海侵体系域 ,其上为高位体系域。三级层序中有包含四 上 、三 下 、三 中 、三 上 等煤层为界的 4个四级层序 ,每个四级层序中发育