Coaly Shale Research Articles

Relationships between Organic Material and Thermal Maturity Derived from Coal and C-Shale Samples

The purpose of this study is to characterize the relationship between organic material and thermal maturity during the process of evaluation of hydrocarbon potential. Samples studied include Miocene high volatile bituminous coal and coaly shale collected from outcrops and exploration wells in Hsinchu-Miaoli area, NW Taiwan, density centrifuge separated macerals, bituminous coal and anthracite from China, in addition to Woodford and Green River oil shale from the United States. Maceral composition analysis, elemental analysis, vitrinite reflectance measurement and Rock-Eval pyrolysis were performed for evaluation. The results of study show that: 1) coal samples from the Shiti Formation (middle Miocene) exhibit more vitrinite and less mineral matter contents than samples from the Nanchuang Formation (upper Miocene); H% is increased in exinite-enriched maceral mixtures with density ＜1.25 g cm^(-3), after density centrifuge separation. 2) A positive linear correlation between Tmax and Ro illustrates both Rock-Eval pyrolysis and vitrinite reflectance can be used as indicators of thermal maturity. 3) From the plot of H/C ratio vs. vitrinite reflectance, even though the depositional environments were different in Taiwan and China, their organic micelles exhibit a similar trend in the process of thermal maturation. As a whole, the curve has a turning point at Ro=0.5% and H/C=0.1 (atomic ratio 1.2) in this study. 4) Arather good correlation between S2 and TOC of samples studied indicates the contribution of S2 from TOC. 5) The highest HI occurred in certain maturities (Tmax and Ro) of samples studied, and not in the stages of less maturity or over-maturity. 6) Two different linear trends were observed in the cross plot of S1 vs. S2. Field outcropped shale or C-shale exhibits a steeper slope compared to that of coal samples which can be attributed to the compositional difference in their organic material. 7) A rather strong positive correlation for H% vs. S2 illustrates the contribution of H-containing macerals, especially exinite. As a result of this study, we expect to promote evaluation techniques for HC exploration; for instance, the development or improvement of evaluation methods for source rocks, reservoirs, structural evolution, and thermal maturity. Evaluations are expected to give more detail regarding local conditions, and be better quantified and more accurate.

Biomarker Distributions as Maturity Indicators in Coals, Coaly Shales, and Shales From Taiwan

The distribution of hopanoids and alkanes in bitumen extracts of coals, coaly shales, and shales from northwestern Taiwan has been measured to assess the maturity of potential petroleum source rocks in the studied area. The C31 homohopane isomers of the studied coals and coaly shales attain equilibrium at maturity corresponding to 0.6% Ro measured in coals or 0.65% Ro in adjacent shales. A proposed parameter using hopanoid ratios reveals a more consistent trend and approaches a steady value at maturity similar to the C31 homohopane isomer ratio. The results show that the onset of the main phase of petroleum generation in northwestern Taiwan takes place at maturity corresponding to VR of 0.6% Ro measured in coals or coaly shales and probably higher VR in shales. The distribution of pristane, phytane n-C17 and n-C18 confirms the validity of the conventional maturity indicators if the samples are from the same source, but shows depositional-or organic-source controls. The source influence on the phytane/n-C18 ratio appears to be larger than that on the pristane/n-C17 ratio. The phytane/n-C18 ratio is also less sensitive to maturity than that of the pristane/n-C17 ratio. The pristane/phytane ratios in the studied coals and coaly shales, in contrast to the pristane/n-C17 ratio, continue to decrease to maturities beyond the oil window up to 1.5% Ro and therefore may be applicable to high maturity sources.

Case Histories of Electrical Resistivity and Controlled-Source Magnetotelluric Surveys for the Site Investigation of Tunnel Construction

In tunnel construction, the information regarding rock mass quality and the distribution of weak zones is crucial for economical tunnel design and to ensure safety. Usually, the rock mass grade is estimated by observing recovered cores obtained by drilling or by physical parameters calculated in a laboratory using core samples. However, the high drilling cost limits the number of boreholes; furthermore, rough terrains can reduce the access of drilling machines to the survey sites. In such situations, surface geophysical methods such as electrical resistivity or controlled-source magnetotelluric (CSMT) can provide a rough estimate of the rock mass condition over the planned tunnel route. These methods can also map weak zones (faults, fractures, coal bearing zones, and cavities), which are characterized by a lower resistivity than the surrounding fresh rock mass. We present two successful applications of the electrical resistivity and CSMT methods to the site investigation of tunnel construction over a rough terrain. The first example demonstrates that the boundary of the bedrock and weak zones related to the distribution of coaly shale and coal seams were estimated to extend beyond a few hundred meters below the rough surface. The second example shows that the developing direction and depth of cavities, which are mainly related to the weak zones in limestone, were successfully interpreted by a three-dimensional (3-D) electrical resistivity survey with the aid of borehole test results.

Geochemistry of beryllium in Bulgarian coals

Abstract The beryllium content of about 3000 samples (coal, coaly shales, partings, coal lithotypes, and isolated coalified woods) from 16 Bulgarian coal deposits was determined by atomic emission spectrography. Mean Be concentrations in coal show great variability: from 0.9 to 35 ppm for the deposits studied. There was no clear-cut relationship between Be content and rank. The following mean and confidence interval Be values were measured: lignites, 2.6 ± 0.8 ppm; sub-bituminous coals, 8.2 ± 3.3 ppm; bituminous coals, 3.0 ± 1.2 ppm; and anthracites, 19 ± 9.0 ppm. The Be contents in coal and coaly shales for all deposits correlated positively suggesting a common source of the element. Many samples of the coal lithotypes vitrain and xylain proved to be richer in Be than the hosting whole coal samples as compared on ash basis. Up to tenfold increase in Be levels was routinely recorded in fusain. The ash of all isolated coalified woods was found to contain 1.1 to 50 times higher Be content relative to its global median value for coal inclusions. Indirect evidence shows that Be occurs in both organic and inorganic forms. Beryllium is predominantly organically bound in deposits with enhanced Be content, whereas the inorganic form prevails in deposits whose Be concentration approximates Clarke values. The enrichment in Be exceeding the coal Clarke value 2.4 to 14.5 times in some of the Bulgarian deposits is attributed to subsynchronous at the time of coal deposition hydrothermal and volcanic activity.

Modelling of the hydrocarbon generation history and volumetric considerations of the coal-sourced Lulita Field, Danish North Sea

The hydrocarbon generation history of the Middle Jurassic Lulita Field in the Søgne Basin in the northeastern part of the Danish Central Graben has been predicted by modelling the Lulita-1Xc well located on-structure and a pseudowell located in the kitchen area. The Lulita Field consists of east-dipping Middle–Upper Jurassic sediments in a structural trap. Waxy oil, sourced from Middle Jurassic coals and type III kerogen (and possibly type I kerogen) shales, occurs in Middle Jurassic sandstone reservoirs sealed by Upper Jurassic marine shales. Maturity modelling (vitrinite reflectance) was carried out by using the PresRo ® kinetic model and a heat flow history calibrated from both the tectonic-subsidence history and maturity data. An effective oil window (‘oil expulsion window’) between 0.85% and 1.8%R o for the Middle Jurassic coal and type III kerogen source rocks was applied. Timing for onset of oil generation differs between the Lulita-1Xc well and the pseudowell. The top of the source rocks becomes mature during the Late Cretaceous in the kitchen area and during the Oligocene in the Lulita-1Xc well. However, oil expulsion from the entire Middle Jurassic source rocks is modelled to have started from the Paleocene in the kitchen area and appears to have continued through to the present day. No, or little, expulsion is modelled in the Lulita-1Xc well, indicating that the Lulita Field was charged by updip migration of hydrocarbons from the Søgne Basin kitchen to the east. Hydrocarbon charging pre-dates the time of potential diagenetic modification of the reservoir, thus limiting reduction in reservoir porosity and permeability. Based on the known coal source rock volume and quality, calculated maximum generated and expelled hydrocarbons cannot account for the estimated in-place volumes of oil. The additional hydrocarbons were probably generated from coaly shales and shaly coals that form the lateral equivalent of the Middle Jurassic coals in the kitchen area, possibly with contributions from lacustrine to brackish type I kerogen shales.

Occurrence and distribution of high molecular weight hydrocarbons in selected non-marine source rocks from the Liaohe, Qaidam and Tarim Basins, China

Extracts of 18 potential source rocks from the Qaidam, Liaohe, and Tarim Basins, China have been characterized by high temperature gas chromatography (HTGC) and found to contain high molecular weight hydrocarbons (HMWHCs) above C 40. These rocks were originally formed in freshwater lacustrine, saline lacustrine, and terrigenous bog environments with mudstone, calcareous mudstone, coaly shale and coal lithologies. Their ages range from Triassic to Miocene and maturities from immature to mature covering a vitrinite reflectance range ( R o) for the Liaohe and Tarim samples of 0.54–0.84%. The combined distributions of the n-alkane and alkylcyclopentane homologues in the extracts can be used to characterize the nature of the original depositional environment. In certain samples the carbon number predominance of the n-alkanes changes from an odd/even predominance to even/odd predominance above C 40 possibly suggesting different precursors for the n-alkanes above and below C 40. Concentrations of the HMWHCs were also observed to increase with maturity of the source rocks. This is the first comprehensive report on the occurrence of HMWHCs in source rocks and their discovery introduces the possibility of using these compounds for oil/source rock correlation purposes in future studies along with the more conventional biomarkers.

Geochemistry of beryllium in the Mariza-east lignite deposit (Bulgaria)

Beryllium geochemistry in coal has been studied on the basis of its distribution in 1556 individual full channels of coal, coaly shales, partings, and lithotype samples from 11 profiles of the Mariza-east lignite deposit (Bulgaria). This is the largest lignite deposit in Bulgaria, producing coal for three Thermal Power Stations (TPS) and a briquette plant. The Be content was determined in the coal ash (500 °C) by atomic emission spectrography at a detection limit of about 1 ppm Be. The mean Be content for the different profiles ranged from 0.7 to 6.9 ppm Be, similar to that of global average for subbituminous coals. Higher concentrations of Be were found in the first seam with thickness from 1 to 4 m, whereas the second seam reached 24 m. Most of the xylain and vitrain samples showed lower Be content than the whole coal samples from which they were selected. The fusain samples were usually enriched in Be compared to the whole coal samples and the other lithotypes which is a specific feature of the deposit. Distribution of Be along vertical profiles follows that of ash. Beryllium in the lignite occurs predominantly in the inorganic matter as isomorphic admixtures and/or adsorbed on the clay minerals. A small portion is bound to the organic matter. These conclusions were based on circumstantial evidence: such as correlation with ash, aluminium, and germanium content; distribution in lithotypes; sink-float; and leaching experiments. The low Be content and its inorganic affinity are supposed to be the result of several factors: negligible influx of Be in solution in the swamp, large dimensions of the basin, great thickness of the main second seam, and long distance from the source province.

Ore-bearing Coaly Shales of the Lena Auriferous Region

Ore-bearing coaly shales of the Lena auriferous region (Patom Highland) are distinctly controlled by lithostratigraphic and structural factors. They are confined to carbonaceous and carbon-bearing (carbonate–terrigenous and terrigenous) lithologic varieties of primarily Au-rich black shales. However, the location of ore-bearing shales within these units is governed by structural factors. Gold mineralization and synore alterations are related to the tectonometasomatic reworking of substance of the geochemically favorable protoliths.

Hydrocarbon system analysis in a rift basin with mixed marine and nonmarine source rocks: The South Viking Graben, North Sea

The South Viking Graben of the North Sea is a prolific oil and gas province that has recoverable reserves of approximately 176 x 109 Sm3 (standard cubic meters) (6.2 tcf) gas, 58 x 106 t (412 million BOE) natural gas liquids, and 12.5 x 106 Sm3 (78 million bbl) of black oil contained in the main fields Sleipner Vest, Sleipner Ost, and Volve. These fields are located primarily within Block 15/9 in the Norwegian sector and extend into neighboring Blocks 15/6 and 16/7. The principal source of black, nonvolatile oil is the Late Jurassic Draupne Formation, which has a predominance of marine algal organic matter. The lower section of the Draupne Formation together with the Heather Formation are organically leaner and contain a mixture of marine algal and terrigenous organic matter, resulting in a potential to generate both oil and gas. The Middle Jurassic Hugin and Sleipner formations contain humic coals and coaly shales with potential to generate gas and some light liquids. These coals contain, on average, 80-90% vitrinitic woody material with occasional enrichment of resinite. High resinite concentrations can lead to an overprediction of oil potential, as they contribute significantly to the hydrogen index (HI) but generate primarily low molecular weight aromatic compounds. All source rock facies types have reached maturities sufficient to generate oil and gas. Basin modeling suggests that onset of oil and gas generation started during the latest Cretaceous-early Paleocene. These source rocks have continued to yield oil and gas to the present day in many parts of the catchment area for the Sleipner fields. Detailed geochemical analyses identified five main oil and condensate families. Family A comprises condensates and oil located in the northernmost part of Sleipner Vest and Dagny, generated from a marine, clastic source with a predominance of type II algal organic matter. Family B is condensates in the middle to southern part of Sleipner Vest, generated from a source, or a contribution from several source facies, with mixed terrigenous higher plant organic matter and marine algal material. Family C consists of condensates reservoired in the Jurassic of Sleipner Ost (except well 15/9-A15), generated from a mixed algal/terrigenous source but with a higher contribution of hydrocarbons from a marine algal source as compared with the Sleipner Vest family B. Family D comprises condensates in the Jurassic-Triassic of Loke and Gungne, in well 15/9-A15 from the crest of the Sleipner Ost structure, as well as condensates within the Paleocene sands of Sleipner Ost. These condensates have a mixed terrigenous higher plant and marine algal signature and are derived from pre-upper Draupne Formation sources. Family E is the black oil present in the Jurassic Volve field, derived from a marine, calcareous shale with type II to II-S organic matter. The source rock for this oil is unique in the greater Sleipner area and is likely located in the isolated subgraben between the northern parts of Sleipner Vest and Sleipner Ost. The hydrocarbon gases are broadly similar and are interpreted to have been generated from coals and coaly shales of the Sleipner and Hugin formations, as well as those parts of the pre-upper Draupne section that have a predominance of terrigenous higher plant organic matter.

Umir Formation: Organic geochemical and stratigraphic assessment as cosource for Middle Magdalena basin oil, Colombia

A detailed geochemical and stratigraphic study conducted on a sedimentary sequence of the Upper Cretaceous Umir Formation, in a section outcropping on the eastern flank of Middle Magdalena basin (MMB), Colombia, identifies this formation as a new hydrocarbon source rock, not previously considered as a source for MMB oil.The Umir Formation is composed of coal, coaly shale, claystone, siltstone, and sandstone. Based on Rock-Eval data, the coal and coaly shale show good potential for oil generation. Certain biomarkers are characteristic of the depositional environment of the Umir Formation and related oil and contrast it with the La Luna Formation and related oil. For example, biomarkers of the Umir Formation show pristane/phytane ratios greater than 1; predominance of C29 steranes; low oleanane/hopane ratios (<0.08); diasteranes/steranes ratios greater than 1; 22,29,30-(trisnor-18a-neohopane/trisnor-17a-hopane) (Ts/Tm) ratios less than 0.46; and relatively low C35/C34 hopane values (<0.94). Values of the bicadinane index of 0.15-0.25 in Umir samples sharply contrast with those of La Luna samples, which are in the range 0-0.07.Oleanane/hopane ratios do not show a good correlation with other plant indicators, for example, C29 sterane percentages and bicadinane indices. Low oleanane/hopane may reflect a predominately conifer rather than angiosperm contribution to the depositional system, which is also supported by observations of abundant resinite in thin sections. The diasteranes/steranes ratio displays an inverse correlation with total organic carbon (TOC) content and hydrogen index (HI) from Rock-Eval pyrolysis, suggesting that this parameter strongly depends on oxic depositional conditions. The biomarker results of the Umir Formation show two main sources of organic matter in competition, marine algal vs. higher plant. A detailed biomarker comparison of Santos-31 oil reservoired in the middle-upper Eocene Esmeralda and La Paz formations, sampled in a field located in the eastern area of the Middle Magdalena basin, shows it to be sourced from the Umir Formation, establishing a new Umir-Esmeralda/La Paz(!) petroleum system in the MMB. This contrasts with a good correlation of Suerte oil in the same geographic area with La Luna source rocks.

石狩～日高堆積盆における石油システム

The petroleum system of the Ishikari-Hidaka basin was investigated using the geochemical data and basin modeling of the Yufutsu oil/gas field. The Yufutsu field is located on the Tomakomai ridge, a north-south trending basement high at the center of the Ishikari-Hidaka basin. In the Yufutsu field, gas and pale yellow-orange waxy condensate oil are produced from so called &quot;Deep Reservoir&quot;, the Cretaceous granitic rocks and the conglomerate member of the Eocene Ishikari Group. In addition, bitumen is observed on cores of Deep Reservoir. Further, black oils are found in the &quot;Shallow Reservoirs&quot;, the upper Eocene coal bearing member of the Ishikari Group, the upper Oligocene Minami-naganuma Formation and the Miocene Takinoue Formation. Oils from the Shallow and Deep reservoirs are correlated to the coal bearing member of the Ishikari Group, from biomarker and carbon isotope data. However, there is subtle compositional difference between oils in the Shallow and Deep Reservoirs. From higher sterane C29-20S/(20S+20R), Ts/(Ts+Tm), Diahopane/C30-hopane, Oleanane/C30hopane ratios, oil from the Deep reservoir is highly matured. On the other hand, oils from the Shallow reservoirs are of moderate maturity. From basin modeling at the main kitchen to the east of the Yufutsu field, the time of peak oil generation was 10-15 Ma. The distribution of oils in the Shallow and Deep Reservoirs are explained as follows : 1) At earlier stage, moderately matured oil was generated in the main kitchen, and some oil migrated into the Deep Reservoir. 2) At later stage, with increasing burial, gas generation and cracking of retained bitumen began, and the gas and condensate migrated into the Deep Reservoir. As a result, de-asphaltation occurred. At the same time, coal and coaly shale around the Yufutsu field became mature, and black oil migrated into sandstone in the Ishikari Group. For oils in the Minami-naganuma and the Takinoue Formations, the timing of accumulation is not clear.

Compound-specific carbon isotope analysis of natural and artificially generated hydrocarbons in source rocks and petroleum fluids from offshore Mid-Norway

Stable carbon isotope signatures of individual hydrocarbon components provide important information on the source rock facies of oils as well as their asphaltene fractions, despite maturity variations and secondary processes such as phase fractionation and biodegradation. Our study is based upon petroleum fluids and source rock samples from offshore Mid-Norway, where the main source rock is the marine shales of the Upper Jurassic Spekk Formation. An alternative source is provided by coals and coaly shales of the Lower Jurassic Åre Formation. In terms of maturity the source rock samples are distributed throughout the main phase of oil generation. In this study compound-specific carbon isotope analysis has been performed on thermal extracts and kerogen pyrolysates of the source rocks, as well as on the oils and the pyrolysis products of their asphaltenes. We demonstrate that trends of absolute isotope data and specific isotopic fingerprints after normalizing the data are useful for petroleum-source rock correlations. The carbon isotope ratios of the n-alkanes separate the Åre from the Spekk Formation samples in both thermal extracts and kerogen pyrolysates, becoming less negative with increasing terrestrial input. The Spekk samples also tend to become isotopically heavier with increasing maturity, while the Åre samples do not show any systematic difference with increasing maturity. The carbon isotope ratios of the n-alkanes also discriminate between the oils as well as the asphaltenes from the fluids. The individual components generated by pyrolysis of kerogens are isotopically heavier than those from the thermal extracts. This is expected from models of kinetic isotope effects which predict that the isotopically lightest products are generally released at an earlier stage in the maturation process. A similar isotopic difference is also observed between the pyrolysis products of asphaltenes and the original oils derived from the same source rock type. However, in a sample where the oil and its asphaltene fraction originate from two different source rocks, the opposite relationship between the carbon isotope composition of the oil and its asphaltene fraction is observed. Bulk isotope data of kerogen concentrates, pyrolysates and the residue after pyrolysis of the source rock samples as well as bulk isotope data of whole oils are also presented. We show that besides separating Åre from Spekk, the bulk carbon isotope values of the Spekk samples are considerably heavier than the n-alkanes from the thermal extracts, whereas those of the Åre samples are almost equal.

Chemical characteristics of Upper Cretaceous (Turonian) jet of the Gosau Group of Gams/Hieflau (Styria, Austria)

Jet and coaly sediments within the Upper Cretaceous (Gosau) Schoenleiten Formation were collected from two outcrops near Gams/Hieflau (Styria, Austria). For comparison, additional jet and coal samples from different Gosau localities were included in the study. The identification of jet as bituminous driftwood (collotelinite) has been provided by microscopical examination of organic matter [Kollmann, H.A. and Sachsenhofer, R.F., Mitt. Ref. Geol. und Paläont. Landesmuseum Joanneum SH 2 (1998) 223]. Rock–Eval analyses revealed enhanced HI and lower T max values of jet compared with the coals and coaly shales. The results reflect the higher contents of bituminous organic matter compared to vitrain-rich coals of similar maturity. In comparison with the coals and coaly shales, high amounts of liberated hydrocarbons (mg HC/g C org) are in contrast to generally lower yields of soluble organic matter during extraction with dichloromethane, indicating that portions of the hydrocarbons are liberated from lipids loosely bound to kerogen during pyrolysis. Further differences in n-alkane distribution patterns, odd over even predominance, pristane/phytane, and pristane/ n-C 17 ratios exist between jet, coals and coaly shales. The microbial origin of short-chain n-alkanes presumably resulted from the degradation of the predominant odd-numbered long-chain n-alkanes within the jet. The occurrence of biological markers (sesqui and diterpenoids) within the sediments (coaly shales), coals and jet samples indicates the origin of terrestrial organic matter from conifers. Biomarker composition of jet samples indicates enhanced aromatisation of sesqui and diterpenoids. These results correspond to enhanced aromatisation of steranes, as reflected by generally higher relative contents of triaromatic steroids in the jet. Because of comparable maturation (0.5–0.6% R r) of the coals, coaly shales and the jet samples, confirmed by the isomerisation of αβ C 31-hopanes and ααα C 29-steranes, the increase in aromatisation in the jet is thought to reflect increased contribution of bacteria to organic matter degradation. The lack of enrichment of the jet samples in hopanes relative to steranes suggests that enhanced biomarker aromatisation is caused by anaerobic rather than by aerobic bacteria.

Late Lower Jurassic palynomorph assemblage in the Dubrajpur sediments, Birbhum District, West Bengal, India

This is the first palynological study of the Dubrajpur sediments exposed near the village Murgadangal within the Birbhum Coalfield of West Bengal. The grey shales and off-white sandy claystones have yielded characteristic palynomorph assemblages. At the base of the succession, which consist of coaly shales. The genus Densipollenites is prominent along with striate bisaccate pollen (Palynozone I). In the same assemblage, the first occurrence of Kremipollenites indicus, Arcuatipollenites pellucidus and Goubinispora indica, is significant. This suggests the end Permian level for the Barakar coal deposits. Subsequently, genus Callialasporites makes its first occurrence at the transition of Barakar and Dubrajpur formations and attains fair presentation in the up-section (Palynozone II) replacing Densipollenites. Definite occurrence of Callialasporites turbatus/dampieri in the presently investigated Dubrajpur strata along with Foraminisporis tribulosus, Klukisporites sp. suggest late Lower Jurassic age for Dubrajpur Formation, and the non-diversified palynomorph composition evidences shallow deposition for this outcrop section.

Brunei Darussalam: Characteristics of selected petroleums and source rocks

The development of three Tertiary deltaic complexes has resulted in the deposition of up to 10 km of sandstones and shales comprising the sources and reservoirs for crude oils that occur onshore, near-offshore and, with future exploration efforts, those likely to be encountered in deepwater reservoirs north of the Brunei coastline. We examined a series of offshore oils and onshore rock samples in Brunei Darussalam (a) to delineate oil family groups and their source rock characteristics, and (b) to assess the source potential of the sedimentary sequence with respect to lithology and depositional setting. Twelve offshore oils and 53 shales, coaly shales and coals were examined. The oils contain indicators of allochthonous (e.g. bicadinanes, oleananes) and autochthonous (e.g. cholestanes and methylcholestanes) components in the source organic matter. Predictable geographic variations of this mixed input are clearly evident in the sample set (e.g. allochthonous input appears to increase in offshore Brunei to the northeast). Although this molecular source signature is relatively clear, migration of these oils from deep (and unidentified) source rocks has resulted in extensive migration-contamination with respect to the tetracyclic and pentacyclic hydrocarbons. This contamination has resulted in strong correlations between certain molecular maturity indicators and the present-day temperature of the reservoirs. Liquid hydrocarbon source rock potential is present in the tidal and coastal embayment facies, and is greatest in the Miocene coals. Neither the shales nor coaly shales contain significant oil generative potential. The thermal immaturity of the sample set precludes valid oil–source rock correlations without conducting artificial maturation experiments on the coals.

Geological structures in the Tongri-Dogye and Sangdeog areas in the eastern part of the Samcheog Coalfield, Korea

The study area, the Tongri-Dogye and Sangdeog areas, is located in the eastern part of the Samcheog Coalfield and consists of Precambrian granitic rocks, Paleozoic sedimentary rocks, and Cretaceous sedimentary and volcanic rocks. The study area is characterized by the E−W trending folds and thrusts, and N−S trending faults. The E−W trending folds and thrusts are well developed and are cut by the N−S trending faults in the study area. The N−S trending faults records two components of fault movements; earlier stage of the west dipping normal fault and later stage of strike-slip fault. A series of these normal faults have a character of step faults and stratigraphic positions are younger toward the west across these faults. Cretaceous volcanic rocks have two phases, extrusive and intrusive phases. Extrusive volcanic rocks are affected by the southwards thrust movement, while others intruded into the thrust sheets. Age of volcanic rocks ranges from 66.9 Ma to 49.2 Ma. These lines of evidences indicate that thrust movement occurs between 66.9 Ma and 49.2 Ma. The Osipcheon Fault, one of the major N−S trending faults in the eastern part of the Samcheog Coalfield, is characterized by strike-slip with dextral movement. Along the Osipcheon fault, the horse tail structures are developed near the tip area in the western part and subparallel faults are dominant in the eastern part of the fault. The Osipcheon Fault is terminated in the Triassic Donggo Formation near the Tongri town. Thrust faults and related structures are also developed along the lateral tip line of the minor thrust such as ramp structures, crescent type anticline, and antiformal stack structures. Along the Osipcheon Fault, minor reverse faults and domino-type extensional faults are developed on the coaly shale beds during the strike-slip faulting.

Mineralogical and elemental variation of coal from Alberta, Canada: an example from the No. 2 seam, Genesee Mine

Mineralogy and elemental contents were determined on 18 samples from a vertical profile of the No. 2 seam, Genesee mine, AB. The samples analyzed consist of coal, coaly shale, shaly coal, carbonaceous shale, shale, mudstone and siltstone. Proximate analysis was determined on all samples. Elemental analyses were determined by instrumental neutron activation analysis (INAA) for all elements except As, B, Cd, Hg, Mo, Pb, Se (Atomic Absorption) and B, Ba, Be, Co, Cr, Cu, Li, Mn, Nb, Sr and V (inductively coupled plasma-emission spectroscopy, ICP-ES). Samples were low temperature ashed (LTA), X-ray diffraction (XRD) and X-ray fluorescence (XRF) were used to determine quantitative major mineralogy. Accessory mineralogy was determined with Scannining Electron microscope/energy dispersive X-ray analyzer (SEM/EDX) on four samples. In general, the coals in the Genesee mine are within the low end of the range for trace element contents given by Swaine [Swaine, D.J., 1990. Trace Elements in Coal. Butterworths, London, 278 pp.] for most coals. High contents of Cr (9–2620 ppm) and Ni (1–1440 ppm) can be related to an increased amount of a Cr–Ni–Fe oxide (chromite–magnetite?) likely derived from ultrabasic diatremes in the Golden-Columbia Icefields, BC area. The No. 2 seam of the Genesee mine can be divided into two geochemical cycles on the basis of mineralogy, trace element contents and rare earth element (REE) behavior. Cycle I consists of quartz, calcite and kaolinite, lower trace element contents, REE slightly enriched in high rare earth elements (HREE), and thick coal with few partings. Cycle II consists of quartz, calcite, kaolinite, illite, mixed layer and/or expandable lattice clays, feldspar, gypsum, calcium aluminum sulfate hydrate, clinoptilolite, calcite and diopside, higher trace element contents, REE slightly enriched in light rare earth elements (LREE) and thin coal with a greater frequency of partings. The differences between the two geochemical cycles can be accounted for by a decreasing stability of the peat-forming environment resulting from an increasing fluvial influence and volcanogenic input.

A study of the composition of light hydrocarbons (C 5–C 13) from pyrolysis of source rock samples

Pyrolysis–GC (open system) has been performed on a total of 30 source rock samples with quantification of all identified components in the C 5–C 13 range. Ten samples are from the marine shales of the Upper Jurassic Spekk Formation and 10 samples from the coals and coaly shales of the Lower Jurassic Åre Formation, from offshore Mid-Norway. This sample set was expanded with 10 samples from the Danish sector, i.e. seven samples from the marine shales of the Upper Jurassic Farsund Formation and three coal samples from the Middle Jurassic Bryne Formation. The samples were selected to cover different maturity levels and facies. The light hydrocarbon distribution generated by pyrolysis shows a clear compositional difference between the different source rock types. In general, the Åre and Bryne Formations were relatively enriched in mono-aromatics and naphthalenes, while the Spekk and Farsund Formations were richer in n-alkenes and n-alkanes. Variations in terrestrial influence of the marine shales of the Farsund and Spekk Formation samples were also observed. It is found that the abundance of m+ p xylene most effectively distinguishes between the different source rock types. This is verified by multivariate modelling. It is shown that the light hydrocarbon composition generated by pyrolysis of kerogen is more affected by source facies than maturity variations.

99/02924 Regional geology, depositional environment and maturity of organic matter of Early to Middle Jurassic coals, coaly shales, shales and clayston

99/02924 Regional geology, depositional environment and maturity of organic matter of Early to Middle Jurassic coals, coaly shales, shales and clayston

Tectonic evolution of the Tertiary basin at Batu Arang, Selangor Darul Ehsan, Peninsular Malaysia

In the Batu Arang area are found Tertiary sedimentary rocks that outcrop within an approximately elliptical basin surrounded by undulating to hilly terrain developed over Permian meta­ sedimentary rocks consisting of quartzites, schistose quartzites, phyllites, indurated shales and rare cherts. The Tertiary strata cover an area of some 15 km2 and rest unconformably over the meta­ sedimentary rocks that generally strike NNW-SSE with variable, steep to vertical dips. The Tertiary strata can be separated into two sequences: an upper one termed the Boulder Beds that consists of semi-consolidated, sandy to gravelly and bouldery sediments that unconformably overlie the lower sequence known as the Coal Measures or Batu Arang Beds comprising interbedded shales, structureless clays, fine grained to pebbly sandstones and some lignite seams. The Boulder Beds consist mainly of sub-angular to rounded, pebble to boulder sized clasts of quartzite, sandstone and vein quartz as well as minor chert, schist, phyllite and shale fragments, in a matrix of gravel, sand or clayey sand, though a few beds of inter-stratified sand and sandy clay are also seen. Differences in colour, as well as differences in composition and roundness of clasts, has allowed for differentiation of three separate sequences within the Boulder Beds. The Beds are up to 300 m thick at the centre of the basin where their bedding is horizontal, though along the basin edges, they show inward dips of 20° to 45°. A number of small, syn-depositional, normal faults, and post-depositional, wrench faults, cut these beds whose age is not know, though a late Middle Miocene to Pliocene age is proposed by correlation with regional tectonic events. The Boulder Beds are alluvial fan deposits that have developed through erosion of steep, fault induced slopes. The Coal Measures or Batu Arang Beds consist of several facies arranged in the following stratigraphical order: i) Sandstone with shale and clay intercalations, ii) Shale, iii) Coal beds, comprising two main coal seams, shale and sandstone, and iv) Sandstone with shale and clay and minor conglomerates including a basal pebbly sandstone. The strata show a synclinal structure plunging gently southeastwards, with the strata having an average dip of 14° towards the centre of the basin, though local variations are common especially towards the basin edges. The fine grained sediments range from stiff, structureless clays to well laminated and fissile shales containing abundant carbonaceous materiaL The shales are also often silty and even sandy and grade into clayey sandstone in places. The inter-bedded sandstones are mostly fine grained, though ranging up to coarse grained, and even pebbly. The coal occurs mostly as thin laminae or streaks in shales, but also builds thicker layers of more than 30 cm thick. In the eastern part of the basin, two thick coal seams are found as well as some thin beds of coal and coaly shale. The two seams are about 65 m stratigraphically apart; the Upper Seam attaining a thickness of up to 15 m, and the Lower Seam averaging 8 m in thickness. The coal appears to be intermediate between high-grade lignite and sub-bituminous coal and is a hard, black rock with a resinous lustre. Palynomorph assemblages indicate an Eocene to Oligocene age for the coals that are likely to have been peat-swamp deposits in an alluvial plain setting, whilst the inter-bedded shales were deposited in a freshwater lacustrine setting. Correlation with known stratigraphic successions in Sumatra shows that the Coal Measures are time-equivalent (Late Eocene-Early Oligocene) with, and have a somewhat similar depositional history as, the Parapat Formation of the North Sumatra Basin, the Permatang Group and Kelesa Formation of the Central Sumatra Basin, and the Lahat Formation of the South Sumatra Basin. Differences in lithology, however, occur and reflect differences in geographical locations; the sediments at Batu Arang having been deposited at a higher altitude, and in a more inland location, as compared with the Sumatran Basins that formed at lower altitudes, close to the then Sundaland coastline. Differences in geographical locations have also influenced the subsequent geological histories of the individual basins. No lithological equivalent of the Boulder Beds is found in the Tertiary strata of the Sumatran Basins, though its deposition is considered to be time-equivalent (Middle Miocene-Pliocene) with the Baong Formation of the North Sumatra Basin, the Minas Group and Binio Formation of the Central Sumatra Basin, and the Air Benakat Formation of the South Sumatra Basin. Correlation with regional tectonic events indicates that a pull-apart basin (of half-graben shape)