Analysis of wax hydrocarbons in petroleum source rocks from the Damintun depression, eastern China, using high temperature gas chromatography     

Haiping Huang  Steve R. Larter  Gordon D. Love   《Organic Geochemistry》2003,34(12):1673

A detailed organic geochemical study; utilising petrography, biomarker hydrocarbon analysis and high temperature GC analysis of extractable wax hydrocarbon constituents was performed on four marginally oil window-mature source rocks from the Shahejie Formation (Eocene), Damintun depression in eastern China. The main maceral components in the source rocks were vitrinite, liptinite and exinite, with vitrinite being more abundant (>50 vol.%) in organic-lean samples whose TOC contents were between 1 and 2 wt.%. Large differences in pristane/phytane ratios suggested that the organic-rich samples were deposited in a less oxic depositional environment than that for the organic-lean rocks. The distribution of extractable wax hydrocarbons, determined by high temperature GC, showed a marked difference between these two sample types. The organic-rich samples contained high molecular weight hydrocarbons (HMWHCs) dominated by macrocrystalline n-alkanes (n-C₂₃–n-C₃₇, typically maximising at n-C₂₉), while the organic-lean samples contained lower amounts of extractable wax hydrocarbons but were relatively rich in microcrystalline components (> n-C₃₅). In all source rocks (Es3 and Es4), a noticeable odd-over-even predominance (OEP) of n-alkane chain lengths (up to n-C₆₅) was evident, consistent with a direct biological origin for the long n-alkyl chains. They were most probably formed during diagenesis from decarboxylation of predominantly even-carbon-numbered aliphatic acids originating from higher plant or lacustrine algal sources and/or were directly biosynthesised in hydrocarbon form. At least two other homologous series of branched/cyclic HMWHCs were observed, one of which was confirmed as a series of branched alkanes (probably methyl-branched). The carbon number distribution patterns of HMWHCs may be primarily controlled by thermal maturity and biogenic source input as well as being influenced by diagenetic reactions governed by depositional environmental conditions, as shown previously [Carlson, R.M.K., Teerman, S.C., Moldowan, J.M., Jacobson, S.R., Chan, E.I., Dorrough, K.S., Seetoo, W.C., Mertani, B., 1993. High temperature gas chromatography of high wax oils. In: Indonesian Petroleum Association, 22nd Annual Convention Proceedings. Jakarta, Indonesian, pp. 483–507. Carlson, R.M.K., Jacobsen, S.R., Moldowan, J.M., Chan E.I., 1994. Potential application of high temperature gas chromatography to Middle Eastern petroleum exploration and production. In: Al-Husseini, M.I. (Ed.), Geo'94, Vol 1., Selected Middle East Papers from The Middle East Petroleum Geoscience Conference, 1994; Gulf PetroLink. Manama, Bahrain, pp. 258–267]. Our study indicates for the first time that Es3 source rocks as well as Es4 facies contain HMWHCs. The distributions of extractable wax hydrocarbons suggest that both Es4 and Es3 members may potentially serve as important parent source rocks for generating waxy petroleum in this region.  相似文献   

Stable isotope evidence for multiple fluid regimes during carbonate cementation of the Upper Tertiary Hazeva Formation, Dead Sea Graben, southern Israel     

Fred J. Longstaffe  Ran Calvo  Avner Ayalon  Steve Donaldson   《Journal of Geochemical Exploration》2003,80(2-3):151-170

Stable carbon- and oxygen-isotope compositions of calcite and dolomite cements have been used to understand porewater evolution in the Upper Tertiary Hazeva Formation within the Dead Sea Graben, southern Israel. Sandstone samples were obtained from four boreholes in three tectonic blocks of the graben over depths of 253–6448 m, a variation that largely reflects differential subsidence of individual fault-bounded blocks. Early carbonate cements dominate diagenesis. Calcite occurs at <1600 m, but was replaced by dolomite at greater depths. Dolomite at 1600–2700 m is Fe-poor (<0.8 mol% FeCO₃), and at 4700–6200 m, Fe-rich (0.5–7.2 mol% FeCO₃). Magnesite, anhydrite and halite are the final diagenetic phases. Calcite has positively correlated δ¹⁸O (+21‰ to +25‰) and δ¹³C (−6‰ to −2‰) values that generally decrease with depth. Dolomite has a wider variation in δ¹⁸O (+18‰ to +30‰) and δ¹³C (−8‰ to −1‰) values, which also generally are lower with increasing depth. However, the δ¹³C and δ¹⁸O values of dolomite from the uppermost 400 m of the Hazeva Formation in the Sedom Deep-1 borehole are anomalous in spanning the entire range of stable carbon and oxygen isotopic compositions over this relatively small interval.The decreasing dolomite δ¹³C values likely indicate an increased contribution of carbon from organic sources with increasing depth. Except for the uppermost 400 m, Hazeva Formation dolomite in the Sedom Deep-1 borehole has stable carbon-isotope compositions that imply initial dolomitization at much shallower levels, prior to the preferential subsidence of this tectonic block. The oxygen isotopic compositions of the calcite cement are best explained by equilibration at present burial temperatures (≤55 °C) with porewater of meteoric origin. Its δ¹⁸O values increased from −5‰ at the shallowest depths to 0‰ at 1600 m. The dolomite oxygen isotopic compositions also reflect equilibration at present burial temperatures with porewaters ranging from 0‰ at 1600 m to +7‰ at 3600 m (100 °C). In the deepest fault block (Sedom Deep-1 borehole), however, increasingly Fe-rich dolomite has (re)equilibrated with porewater whose δ¹⁸O values decreased from +9‰ at 4750 m (120 °C) to +1‰ to +2‰ by 6200 m (150 °C).Much of the dolomite likely formed at relatively shallow depths from saline brines derived from precursors to the Dead Sea. These infiltrated the Hazeva Formation, mixing with and largely displacing meteoric water, and dolomitizing calcite. Rock–water ratios tended to be high during these processes. However, the upper 400 m of the Hazeva Formation in the deepest fault block were likely deposited during its rapid tectonic subsidence, and largely escaped the initial style of dolomitization pervasive elsewhere in the study area. These sediments were also capped by evaporites. This relatively thin interval likely became a preferential conduit for brines that escaped underlying and overlying strata, including the Fe-rich, lower ¹⁸O fluids (evolved seawater?) present in the deepest part of the graben. These rocks present the most promising target for the passage and accumulation of hydrocarbons in the study area.  相似文献   

Morphology and surface brightness evolution of z∼1.1 radio galaxies     

Nathan Roche  Stephen Eales  & Steve Rawlings 《Monthly notices of the Royal Astronomical Society》1998,297(2):405-418

We use K '-band (2.1-μm) imaging to investigate the angular size and morphology of 10 6C radio galaxies, at redshifts 1≤ z ≤1.4. Two radio galaxies appear to be undergoing mergers, another contains, within a single envelope, two intensity peaks aligned with the radio jets, while the other seven appear consistent with being normal ellipticals in the K band.
Intrinsic half-light radii are estimated from the areas of each radio galaxy image above a series of thresholds. The 6C galaxy radii are found to be significantly smaller than those of the more radio-luminous 3CR galaxies at similar redshifts. This would indicate that the higher mean K -band luminosity of the 3CR galaxies reflects a difference in the size of the host galaxies, and not solely a difference in the power of the active nuclei.
The size–luminosity relation of the z ∼1.1 6C galaxies indicates a 1.0–1.6 mag enhancement of their rest frame R -band surface brightness relative to either local ellipticals of the same size or FRII radio galaxies at z <0.2. The 3CR galaxies at z ∼1.1 show a comparable enhancement in surface brightness. The mean radius of the 6C galaxies suggests that they evolve into ellipticals of L ∼ L * luminosity, and is consistent with their low-redshift counterparts being relatively small FRII galaxies ∼25 times lower in radio luminosity, or small FRI galaxies ∼1000 times lower in radio luminosity. Hence the 6C radio galaxies appear to undergo as much optical and radio evolution as the 3CR galaxies.  相似文献   

The radio luminosity function of radio-loud quasars from the 7C Redshift Survey     

Chris J. Willott  Steve Rawlings  Katherine M. Blundell  & Mark Lacy 《Monthly notices of the Royal Astronomical Society》1998,300(3):625-648

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Response of resource excavations in Mobile Bay, Alabama, to extreme forcing     

William W. Schroeder  Jean L. W. Cowan  Jonathan R. Pennock  Steve A. Luker  William J. Wiseman 《Estuaries and Coasts》1998,21(4):652-657

Fossil reef deposits of the American oyster,Crassostrea virginica, are a common component of the near surface sediments in the middle and upper reaches of Mobile Bay, northern Gulf of Mexico. Mining of these deposits occurred from 1946 through 1982 in open areas of undisturbed bay bottom, outside of the shipping channel corridors, in water depths of 3–5 m. The mining process resulted in the formation of pit to furrow-shaped depressions with elevated rims at some sites and troughs and ridges in other areas. Studies carried out in the early 1970s predicted normal physical processes would restore the bottom to pre-shell mining conditions within 1 yr, thus minimizing any long-term effects on the Mobile Bay estuary. However, over the period 1974–1976 unfilled excavations, some with raised rims and ridges, were observed where mining had occurred 3–5 yr earlier. In addition, the depressions tended to be sites of relatively high salinity, hypoxic to anoxic water. In 1992–1993, close grid bathymetric surveys produced no indication of either depressions or raised features at any of the old mining sites. Evidence suggests this leveling of the bay’s bathymetry was the result of two major hurricanes, Frederic in 1979 and Elena in 1985, which mobilized and redistributed significant quantities of sediments within Mobile Bay. These findings indicate currents and waves associated with Mobile Bay’s normal tidal activity and annual recurrent storms were acting very slowly to refill depressions and flatten elevated features. In contrast, the direct impact of major hurricanes appears to have served as an effetive agent to return Mobile Bay’s bathymetry to a state similar to pre-shell mining conditions.  相似文献   

A late Holocene pollen record of deforestation and environmental change from the Lake Tauanui catchment, Northland, New Zealand     

M. B. Elliot  J. R. Flenley  D. G. Sutton 《Journal of Paleolimnology》1998,19(1):23-32

Late Holocene pollen and sediment records from the Lake Tauanui catchment, northern New Zealand, indicate that the lake formed about 5500 years ago following a series of volcanic events in the Tauanui Volcanic Centre. These volcanic events initiated a volcanosere resulting in a mixed conifer-hardwood forest. Dacrydium cupressinum was the dominant tree. Agathis australis was always present. Changes similar to those registered in other Northland pollen diagrams are apparent. At ca 4000 yr B.P., when the climate became cooler and drier than before, a fire occurred in the catchment area causing erosion of the surrounding slopes and some destruction of forest. Fluctuations in abundance of many forest species, including Ascarina lucida, A. australis and D. cupressinum, from ca 3500 yr B.P. indicate repeated disturbance, increasingly so after 1600 yr B.P. Summer droughts and increased frequency of cyclonic winds are suggested as the cause. Major anthropogenic deforestation events defined by palynology occurred across many parts of the New Zealand landscape at ca 700 yr B.P. At Lake Tauanui anthropogenic forest disturbance, radiocarbon dated to ca 1000 yr B.P., is indicated by significant decline in all tree and shrub elements with concomitant increase in pteridophytes, especially Pteridium esculentum. Charcoal concentration increases steadily from the onset of disturbance, and in the final phase after the arrival of Europeans, major clearance of vegetation is indicated. Herbs increase markedly in this period, in diversity and abundance.  相似文献   

Drought Monitoring Using Data Mining Techniques: A Case Study for Nebraska, USA   总被引：4，自引：0，他引：4  

Tsegaye Tadesse  Donald A. Wilhite  Sherri K. Harms  Michael J. Hayes  Steve Goddard 《Natural Hazards》2004,33(1):137-159

Drought has an impact on many aspects of society. To help decision makers reduce the impacts of drought, it is important to improve our understanding of the characteristics and relationships of atmospheric and oceanic parameters that cause drought. In this study, the use of data mining techniques is introduced to find associations between drought and several oceanic and climatic indices that could help users in making knowledgeable decisions about drought responses before the drought actually occurs. Data mining techniques enable users to search for hidden patterns and find association rules for target data sets such as drought episodes. These techniques have been used for commercial applications, medical research, and telecommunications, but not for drought. In this study, two time-series data mining algorithms are used in Nebraska to illustrate the identification of the relationships between oceanic parameters and drought indices. The algorithms provide flexibility in time-series analyses and identify drought episodes separate from normal and wet conditions, and find relationships between drought and oceanic indices in a manner different from the traditional statistical associations. The drought episodes were determined based on the Standardized Precipitation Index (SPI) and Palmer Drought Severity Index (PDSI). Associations were observed between drought episodes and oceanic and atmospheric indices that include the Southern Oscillation Index (SOI), the Multivariate ENSO Index (MEI), the Pacific/North American (PNA) index, the North Atlantic Oscillation (NAO) Index, and the Pacific Decadal Oscillation (PDO) Index. The experimental results showed that among these indices, the SOI, MEI, and PDO have relatively stronger relationships with drought episodes over selected stations in Nebraska. Moreover, the study suggests that data mining techniques can help us to monitor drought using oceanic indices as a precursor of drought.  相似文献   

Recent protected-area designation in China: an evaluation of administrative and statutory procedures   总被引：3，自引：0，他引：3  

C. Y. Jim  Steve S. W. Xu 《The Geographical journal》2004,170(1):39-50

Past protected-area (PA) designation in China followed a centralized administrative approach with minimum participation of lower-echelon governments. A period of deregulation and decentralization in 1979–91 without the benefit of relevant legislation resulted in few designations and poor management. Responding to national and international encouragement to augment the conservation of natural resources, the central government enacted statutory procedures in 1991 to encourage and regulate PA establishments at different administrative levels of government. The study evaluates the effectiveness of the new procedures in fulfilling conservation objectives. The new legislative and administrative regime reinforces deregulation and decentralization by devolving designation power and shifting financial and management responsibilities to lower levels of government, and involving more scientists and objective site assessment in PA design and assessment. Problems have arisen in the designation process due to the omission of key biota and ecosystems, bypassing the scientific assessment stage, too much emphasis on non-conservation gains, ignoring the needs of local communities, escalating people–park conflicts, intensifying paper-park syndrome, and the conflicting role of experts. The recently designated Shimentai Provincial Rank Nature Reserve in a mountain area in south China served as a case study to illustrate the procedures and problems.  相似文献   

A climatology of leaf surface wetness     

O. Klemm  C. Milford  M. A. Sutton  G. Spindler  E. van Putten 《Theoretical and Applied Climatology》2002,71(1-2):107-117

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A numerical modelling study of coastal flooding     

Kathleen L. McInnes  Graeme D. Hubbert  Debbie J. Abbs  Steve E. Oliver 《Meteorology and Atmospheric Physics》2002,80(1-4):217-233

Summary A coastal ocean model capable of modelling tides, storm surge and the overland flow of floodwaters has been further developed to include the flux of water from tributaries and the forcing from wave breaking that leads to wave setup in the nearshore zone. The model is set up over the Gold Coast Broadwater on the east coast of Australia. This complex region features a coastal lagoon into which five tributaries flow and is subject to flooding from extreme oceanic conditions such as storm surge and wave setup as well as terrestrial runoff. Weather conditions responsible for storm surge, waves and flooding include cyclones of both tropical and mid-latitude origin. Two events are modelled. The first is an east coast low event that occurred in April 1989. This event verified well against available observations and analysis of the model simulations revealed that wave setup produced a greater contribution to the elevated water levels than the storm surge. The second case to be modelled was tropical cyclone Wanda, responsible for the 1974 floods. Modelled water levels in the Broadwater were reasonably well captured. Sensitivity experiments showed that storm surge and wave setup were only minor contributors to the elevated sea levels and their contribution was confined to the earlier stage of the event before the runoff reached its peak. The contribution due solely to runoff exhibited a tidal-like oscillation that was 180° out-of-phase with the tide and this was attributed to the greater hydraulic resistance that occurs at high tide. A simulation of this event with present day bathymetry at the Seaway produced sea levels that were 0.3–0.4 m lower than the simulation with 1974 bathymetry highlighting the effectiveness of deepened Seaway channel to reduce the impact of severe runoff events in the Broadwater. Received October 16, 2001 Revised December 28, 2001  相似文献