Journal of Earth Science

Paleofire indicated by polycyclic aromatic hydrocarbons in soil of Jinluojia archaeological site, Hubei, China

Shengli ZOU, Rencheng LI, Shucheng XIE, Junying ZHU, Xinjun WANG, Junhua HUANG

2010, 21(3): 247-256. doi: 10.1007/s12583-010-0089-x

[Abstract](915) [FullText HTML] (107) [PDF 427KB](29)

Abstract:
Combustion-derived and land-plant-derived polycyclic aromatic hydrocarbons (PAHs) have been investigated by using the GC-MS analysis in an ancient soil profile from Jinluojia (金罗家) archaeological site at Macheng (麻城), Hubei (湖北) Province, Central China. Retene, cadalene and simonellite were proposed to be derived from contemporary land plants. The pyrolytic PAHs identified include fluoranthene, pyrene, benzofluoranthenes, benzo[e]pyrene and benzo[a]pyrene. The distribution of these pyrolytic PAHs varies with depth, displaying a pattern different from the land-plant-derived compounds. On the basis of the parameter diagnostic of sources and the distribution patterns, these pyrolytic PAHs were demonstrated to be of combustion origin, rather than petrogenic origins, combustion of petroleum products and coal, or a post-depositional process such as pedogenesis or leaching. These combustion-induced PAHs were believed to result from both natural processes and anthropogenic activities. Two episodes of the elevated content of pyrolytic PAHs and charcoal fragments were identified in Ming-Qing (明清) Dynasty and late Xizhou (西周) to early Dongzhou (东周) Dynasty, inferring the occurrence of two enhanced paleofires. The two enhanced paleofire episodes were found in association with the two cold and dry paleoclimate and two episodes of enhanced abundance of charcoal fragments, inferring a dominance of the natural processes triggering the enhanced paleofire. The two periods of paleofire were also characterized by the frequent and enhanced anthropogenic activities such as war fights, likely suggesting the occurrence of anthropogenic contributions.

Detrital zircon geochronology and provenance of core sediments in Zhoulao Town, Jianghan plain, China

Jietao WANG, Chang'an LI, Yong YANG, Lei SHAO

2010, 21(3): 257-271. doi: 10.1007/s12583-010-0090-4

[Abstract](1145) [FullText HTML] (173) [PDF 1062KB](28)

Abstract:
In our study, the U-Pb age spectrum of detrital zircons from terrigenous sediments is used to determine the sources. The Middle and Upper Reaches of the Yangtze River drain the western Yangtze craton and eastern Tibetan plateau, and take lots of sediments to the Jianghan (江汉) plain. Detrital zircons collected from Zhoulao (周老) core provide an ideal sample for the provenance studies. Here we report LA-ICP-MS U-Pb ages of 125 detrital zircons from one sand sample in the core sediments, which is recovered from a depth of 86.76–88.58 m and the paleomagnetic age is about 800 kaBP, in Zhoulao Town. The 125 zircons reveal nine major age peaks of > 3.0, 2.5–2.3, 2.0–1.7 Ga, 838–723, 453–415, 257, 212, 166 and < 17 Ma. Only two zircons have ages of 14.8 and 16.5 Ma, their appearance indicates that the headwater of the Yangtze River had reached the Tibetan plateau about 800 ka ago. Our results also show that the Hanjiang (汉江) River did not influence the sediments of the Zhoulao core obviously at that time.

Effect of volcanic activities and CO₂ concentration on summer temperature in middle stratosphere, North Hemisphere

Weizheng QU, Shenggui DENG, Fei HUANG, Yingchen LIU, Ting FAN, Yan BAI

2010, 21(3): 272-283. doi: 10.1007/s12583-010-0091-3

[Abstract](598) [FullText HTML] (55) [PDF 359KB](28)

Abstract:
Successive filtration and comparison show that the stratosphere air temperature in 10 hPa-layer of the Northern Hemisphere (NH) in July continuously increases, which is associated to the increases in greenhouse gases mostly CO₂, volcanic activities, and solar activity, demonstrating the follows. (a) The increase in CO₂ concentration is largely consistent with that of the stratosphere air temperature in 10 hPa-layer of the NH in July. However, the increase in the air temperature is not in a linear pattern, during which several cooling events interrupt. The cooling events between late 1960s and late 1970s are remarkable ones and so is the one before mid 1990s. Analysis shows that these events are induced by volcanic activities and solar activity. (b) The CO₂-free variation in the stratosphere air temperature in 10 hPa-layer of the NH is consistent with that of the solar magnetic index. The wave crests and wave troughs of the two curves are consistent in phase, and the curve of solar magnetic index leads the other slightly. In other words, when the solar magnetic pole is southward, a warming in the NH stratosphere corresponds; and on the contrary, the northward solar magnetic pole corresponds to a cooling event. The variation in solar magnetic polarity strongly impacts the variation in the stratosphere temperature.

Analysis of depth-diameter relationship of craters around oceanus procellarum area

Haiyan HU, Ruiyan YANG, Dinghua HUANG, Bing YU

2010, 21(3): 284-289. doi: 10.1007/s12583-010-0092-2

[Abstract](703) [FullText HTML] (67) [PDF 296KB](24)

Abstract:
Studying the depth-diameter relationship of impact craters around the Oceanus Procellarum area together with values for simple crater, complex crater and basin confirms two inflections in the depth/diameter (d/D) curve. We classify impact craters to three types, which are simple crater, complex crater and basin. Using the most 'pristine' or deepest craters in the data, three kinds of depth-diameter relationships are determined: the linear fit for simple crater is d=0.126D+0.490 2; the best empirical power fit for complex crater is d=0.327 3D ^{0.625 2}; the best empirical power fit for basin is d=0.300 4D ^{0.463 3}, where d is the depth of the crater and D is the diameter of the crater, both in kilometers. The depth-diameter relationship for basin is characterized by a lower slope than that for complex craters, demonstrating that this morphologic transition corresponds to a further decrease in the depth of an impact structure relative to its diameter with increasing size. These relationships can then be used to estimate the theoretical depth of any impact radius, and therefore can be used to estimate the pristine shape of the crater around the Oceanus Procellarum area. The study of Oceanus Procellarum will help humankind to learn more about the origin and evolution of the moon.

Characteristics of subaerial karstification and late reconstruction in the Dengying Formation, Sichuan basin, southwestern China

Guozhi WANG, Shugen LIU, Yongsheng MA, Guosheng XU, Xunyu CAI

2010, 21(3): 290-302. doi: 10.1007/s12583-010-0093-1

[Abstract](774) [FullText HTML] (106) [PDF 809KB](26)

Abstract:
Tectonic uplift at the end of Sinian resulted in the denudation of the Dengying (灯影) Formation on a different scale and the development of a great number of secondary dissolution vugs beneath the unconformity between Sinian and Cambrian. Geological and geochemical characteristics such as the development of caves, sinkholes, karst tubes and weathering crust, abrupt depletion and negative deflection of δ¹³C and δ¹⁸O in country rock and vug filling toward unconformity surface suggest that subaerial karstification is responsible for the development of secondary karst vugs within 150 m or so beneath the unconformity surface. This kind of secondary dissolution vug was partially or completely filled by different stage dolomite, calcite, quartz and bitumen during the later deep burial and uplift. Facts such as the obvious difference in δ¹³C and δ¹⁸O of the filling in the subaerial karst vug from the country rock and the value of δ¹³C and δ¹⁸O of the filling increasing or decreasing with that of the country rocks, suggest that the hydrothermal fluid charged in vugs is allogenic fluid. Subaerial karstification vug acted as a conduit for allogenic corrosive fluid which can create new secondary vugs and enlarge previous karst vugs. The dissolution, precipitant and recrystallization produced by allogenic corrosive fluid introduction and petroleum thermal cracking, caused contraction or enlargement of the subaerial karstification vugs and the development of new secondary vugs during the deep burial and uplift. The ultimate vug of deep burial dolomitite is determined not only by fluid charge, dissolution, mineral precipitant, and petroleum thermal cracking during the deep burial and tectonic uplift, but also by the amount of initial secondary dissolution vugs created by subaerial karstification.

Organic Geochemical and Fluid Inclusion Evidence for Filling Stages of Natural Gas and Bitumen in Volcanic Reservoir of Changling Faulted Depression, Southeastern Songliao Basin

Liming Qin, Zhihuan Zhang, Yuyuan Wu, Rujin Feng, Ling Zan

2010, 21(3): 303-320. doi: 10.1007/s12583-010-0094-0

[Abstract](1003) [FullText HTML] (100) [PDF 2773KB](26)

Abstract:
Recently, volcanic gas reservoirs in Yaoyingtai (腰英台) and Daerhan (达尔罕) tectonic belts in Changling (长岭) faulted depression of southeastern Songliao (松辽) basin have been discovered. Based on the compositions and isotopic values, the natural gas is characterized by high content of methane, low content of C₂ ⁺, and C₁/C_1–5 beyond 0.95. Also, the natural gas contains nonhydrocarbons including carbon dioxide with the content from 20% to 40% and minor amount of N₂. Combined with the isotopic values, the natural gas is generated by humic kerogen and coal-derived type, but in Daerhan, the natural gas is probably mixed by oil type gas. From the measurement of lithology and fluid inclusions in volcanic rocks, the bitumen, liquid hydrocarbon, and gas hydrocarbon inclusions are present. Through the analysis of the single gas inclusion in volcanic reservoir, the content of carbon dioxide is low, so the carbon dioxide and hydrocarbon gas of the reservoirs are not accumulated at the same time. In addition, minor amount of bitumen in the reservoirs is formed by thermal evolution of the crude oils sourced from the Yingcheng (842557CE) Formation mudstones through the characterizations of the biomarkers. The distribution of homogenization temperatures presents two peaks, one with the liquid hydrocarbon filling stage, and the other with gas filling stage. However, in Daerhan tectonic belt, the second peak is gas and carbon dioxide mixed filling period probably. Combined with the homogenization temperatures of salt water inclusions, the oil and gas filling period is from Qingshankou (青山口) Formation to Nenjiang (嫩江) Formation in the research area. During the charging period, minor amount of inorganic carbon dioxide filled into the trap, but plenty of inorganic carbon dioxide from the end of Sifangtai (四方台) to Eogene periods was related with the structural movement.

Origin of Subsequent Condensate Pool in Lunnan Low Uplift, Northwest China

Nan Wu, Zhongxian Cai, Xianfeng Liu, Haijun Yang, Jianfa Han

2010, 21(3): 321-329. doi: 10.1007/s12583-010-0095-z

[Abstract](905) [FullText HTML] (87) [PDF 824KB](26)

Abstract:
Lunnan (轮南) low uplift, where developed amounts of condensate pools in both Ordovician and Carboniferous reservoirs, locates in the north uplift of Tarim basin, Northwest China. Lunnan area has experienced intensive gas invasion since the Himalayan movement, causing multiple types of accumulation coexisting in the Ordovician reservoir. Geochemical evidence shows that these condensate oils are of low maturity (vitrinite reflectance levels near 1.0%) and the dominant component of the condensate gas is dry gas (the content of CH4 over 94%), which reflects that the condensate pool in Lunnan area is not the product of thermal cracking, but the subsequent accumulation derived from the phase fractionation. Furthermore, our observations on the C₆-C₇ hydrocarbons in Lunnan area are qualitatively similar to the effect of phase fractionation with condensates having higher paraffin and lower aromaticity than residual oils. Thus, two types of the condensates are defined by their phase behavior, which are saturated condensate pool and the nonsaturated one. The saturated condensate pool with an oil ring mainly developed in Ordovician reservoir, with large difference between formation pressure (FMP) and the dew point pressure (DPP). The origin of these condensates is considered as the in-situ segregation triggered by the invasion of excessive dry gas. On the other hand, the nonsaturated condensate pool that almost existed in the Carboniferous reservoir is a hydrocarbon reservoir containing slight difference between FMP and DPP, without oil ring, and evaporative fractionation due to the fault movement controls its generation.

Experimental Field Study of Movement Charateristics of Rock Blocks Falling down a Slope

Runqiu Huang, Weihua Liu, Jiangping Zhou, Xiangjun Pei

2010, 21(3): 330-339. doi: 10.1007/s12583-010-0096-y

[Abstract](887) [FullText HTML] (93) [PDF 1612KB](25)

Abstract:
The downslope movement of detached rock blocks along steep slopes is an important process endangering the safety of infrastructure along the foot of a slope and on the valley bottom, but only limited knowledge is available on the influence of various factors on the velocity and distance of movement of such blocks. We discuss the influence of the mass and shape of the rock blocks, the steepness of the slope, and the thickness of the overburden on the slope, on the distance of movement of rock blocks which was observed in 256 field experiments with differently shaped blocks from 3 different positions on the slope with a height of 176 m. The statistical evaluation of the results of the field tests shows that the slope condition of gradient and overburden is the main factor, the form of rock masses is the second factor, and the mass is the third of the influencing factors. It is the maximum average acceleration for movement of rock masses when the mass of rock masses is 15≤m < 27 kg, the form of rock masses is flake, the condition of gradient is on average 59.6° and the overburden is basic exposed bedrock and a small quantity of gravel-soil in the experiment condition. It is the minimum average acceleration for movement of rock masses when the mass of rock masses is 9.5≤m < 15 kg, the form of rock masses is rectangular, the condition of gradient is on average 39° and the overburden is gravel-soil and cinder. Then, the foundation for impact energy is provided and the new feasible methods to prevent potential unstable rock masses are put forward.

Pretreatment of Diosgenin Wastewater Using Polyferric Sulfate and Cationic Polyacrylamide

Zhen Liang, Yanxin Wang

2010, 21(3): 340-346. doi: 10.1007/s12583-010-0097-x

[Abstract](619) [FullText HTML] (51) [PDF 411KB](28)

Abstract:
Coagulation-flocculation process was applied in the pretreatment of diosgenin wastewater. Polyferric sulfate was used as primary coagulant and a cationic polyacrylamide (CPAM) was used as coagulant aid. Using jar test procedure, the influence of the main operating parameters, such as effluent pH and coagulant dosage in the coagulation performance was investigated. The effective pH was found to be in the range of 6.5–8.0 and coagulant dosage was 100 mg/L. Under the optimal conditions, 15% chemical oxygen demand (COD) removal efficiency was achieved and the residual turbidity was less than 20 NTU. The presence of CPAM substantially promoted the reduction of residual turbidity with the appropriate CPAM dosage in the range of 2–5 mg/L.

Well Logging Responses of UHP Metamorphic Rocks from CCSD Main Hole in Sulu Terrane, Eastern Central China

Miao Luo, Heping Pan

2010, 21(3): 347-357. doi: 10.1007/s12583-010-0098-9

[Abstract](1089) [FullText HTML] (98) [PDF 946KB](26)

Abstract:
The lithologies of the Chinese Continental Scientific Drilling main hole (CCSD-MH) are mainly comprised of orthogneiss, paragneiss, eclogite, amphibolite, and ultramafic rocks. The statistical results of logs of CCSD-MH indicate that ultramafic rocks are characterized by very high CNL (neutron log) and very low GR (gamma ray log) and RD (resistivity log); eclogites are characterized by high DEN (density), V_P (P-wave velocity) and PE (photoelectric absorption capture cross section); orthogneiss and paragneiss are characterized by high GR, U (uranium content), Th (thorium content), K (potassium content) and RD, and low DEN, PE, and CNL; logging values of amphibolite are between the logging values of eclogites and paragneiss. In addition, the logs could reflect the degree of retrograde metamorphism of eclogites. The upper section (100–2 000 m) shows higher DEN, PE, V_P, and lower GR, U, Th, K, RD than the lower section (2 000–5 000 m). Most logs of the upper section are more fluctuant than those of the lower section. This indicates that the upper section has more heterogeneities than the lower section. The cross plots of logs indicate that DEN, GR, K, and CNL are more powerful in identifying ultrahigh pressure metamorphic (UHPM) rocks at the CCSD-MH. GR value of the rocks from CCSD-MH shows obviously an increasing trend from ultramafic rock (the most mafic rocks at CCSD-MH) to orthogneiss (the most acid rocks at CCSD-MH). On the contrary, DEN value decreases from the ultramafic rock to the orthogneiss. CNL log is a good indicator of the content of structure water in crystalline rocks.

Derivative-Based Techniques for Geological Contact Mapping from Gravity Data

Yuanyuan Li, Yushan Yang, Tianyou Liu

2010, 21(3): 358-364. doi: 10.1007/s12583-010-0099-8

[Abstract](581) [FullText HTML] (120) [PDF 2782KB](32)

Abstract:
Gravity anomalies illuminate subsurface lithology and geological structure in three dimensions, which is vital for studies of concealed faults, sedimentary basins, basement lithology, and other geological targets. Although not all geological contacts correspond to lithological contacts, the contact mapping provides key information on structural regimes, deformation styles and trends. Many techniques for contact mapping have been developed. Here, we evaluate five methods applied to gridded data. The first two are the horizontal gradient magnitude of the gravity field (GF_hgm), and tilt (TI_hgm). The third and fourth rely on locating maxima of the analytic signal (AS) and the 3D local wavenumber (LW). The fifth is normalized standard deviation (NSTD) method. In this article, we evaluate the use of these five methods for mapping contacts and compare the results. First, synthetic vertically-sided models are used to quantify the offsets of maxima from the true contact location due to the source effects of finite source thickness, central depth, and width. Second, the effects of contact dip are discussed. Finally, a real data set is used to evaluate the ability of each method to produce maps of coherent contact trends in the presence of noise and gridding artifacts.

2010 Vol. 21, No. 3

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