新疆塔里木盆地东北部库鲁克塔格地区寒武─奥陶纪遗迹化石

本文研究的遗迹化石采自新疆塔里木盆地东北部库鲁克塔格山上寒武统和奥陶系．经鉴定计有１６个遗迹属，２１个遗迹种，其中有４个新遗迹种．这个地区丰富的深海Ｎｅｒｅｉｔｅｓ遗迹相遗迹化石在我国首次发现，这些发现对于塔里木盆地的油气勘探，沉积环境分析具有重要的意义．

“技术进步”时代的“回望”——《西南陶纪》的艺术史意义

多年来,贡布里希先生在《艺术的故事》里的这句话——＂整个艺术史不是技术熟练的发展史,而是观念和要求的变化史。＂——一直被我理解为观看不同时代不同地域作品面貌的箴言。从图像和技术中获得观念的不同体现,主体必须放下对固有价值体系的过度依赖,贴近艺术的审美特质,

读陶纪疑

一陶渊明《始作镇军参军经曲阿》诗曰:“弱龄寄事外,委怀在琴书。”丁福保《陶渊明集笺注》:“二十曰弱。”逯钦立《陶渊明集》注:“弱龄,弱年,少年。”《有会而作》诗曰:“弱年逢家乏,老至更长饥。”唐满先《陶渊明集浅注》:“弱年,指少年。”《怨诗楚调示庞主簿邓治中》诗曰:“弱冠逢世阻,始室丧其偏。”王瑶《陶渊明集》注:“弱冠,初加冠之时,指二十岁。”杨勇《陶渊明集校笺》从之。逯钦立注:“

Hydrocarbon charging histories of the Ordovician reservoir in the Tahe oil field, Tarim Basin, China

The Ordovician reservoir of the Tahe oil field went through many tectonic reconstructions, and was characterized by multiple hydrocarbon chargings. The aim of this study was to unravel the complex charging histories. Systematic analysis of fluid inclusions was employed to complete the investigation. Fluorescence observation of oil inclusions under UV light, and microthermometry of both oil and aqueous inclusions in 105 core samples taken from the Ordovician reservoir indicated that the Ordovician reservoir underwent four oil chargings and a gas charging. The hydrocarbon chargings occurred at the late Hercynian, the Indo-Sinian and Yanshan, the early Himalaya, the middle Himalaya, and the late Himalaya,respectively. The critical hydrocarbon charging time was at the late Hercynian.

Vertical variation of trace elements and its relation to the water-bearing capacity of Ordovician strata,in Datun coal field

We tested for fourteen trace elements in samples collected from the Ordovician strata in Datun coal field. The vertical concentration variation of these trace dements is reported. The relationship of the variation to the water-bearing capacity of the Ordovician strata is discussed. The minimum concentration of eleven （of 14 total） trace elements appears in the lower Majiagou formation. The maximum concentrations mainly appear in the Badou and Jiawang formations： eight maxima are located in Badou and four more are in Jiawang. The study of karst development and the water-bearing capacity of Ordovician strata shows that karst is well developed in the Majiagou formation and there is a consequent high water-bearing capacity in this formation： Badou and Jiawang formations are contrary to this situation. The results illustrate that the minimum concentrations of most trace elements within certain Ordovician formations can be taken as strong evidence for the existence of a well developed karst and a high water-bearing capacity.

Late Ordovician and Early Devonian conodonts from Onoo Tolgoi area of Mongolia

Conodont samples were collected from three localities in the Onoo Tolgoi area, Mongolia, and many conodonts have been found. Conodonts from the Onoo Tolgoi Formation （M288-M294） lack index fossils; its age could be Late Silurian. Samples from the Hutul us hudag Formation （M295-M299） contain Ozarkodina pandora alpha Morph. （ P element）, clearly indicating that this formation is Early Devonian late Lochkovian in age. Samples collected from so-called Silurian Onoo Tolgoi Formation at other localities （M300-M303） yield many Ordovician conodonts, including Icriodella baotaensis, Icriodella cf. baotaensis, Eoplacognathus fianyeen- sis, Eoplacognathus protoramosus ; Baltoniodus alobatus ; and ？ Ambalodus triangularis ; the age is Late Ordovician, more precisely, early-middle Late Ordovician.

Carbon and strontium isotope variations and responses to sea-level fluctuations in the Ordovician of the Tarim Basin

In the Ordovician, a carbonate platform system grading from the platformal interior eastwards to basin was developed in the Tazhong area of the Tarim Basin, and the study column is located in the place where the paleoslope occurred. The isotope compositions of the carbonates there are thus considered as having reflected those of simultaneous sea waters in view of its good connection with the open seas. The carbon and strontium isotope compositions of the Ordovician carbonates in the Tazhong area are analyzed, and their relationships to the sea-level fluctuations are discussed as well. Studies have revealed that the carbon isotope composition is related positively with the sea-level fluctuations, whereas an opposing situation occurs to the strontium isotope variation. Similar responses of carbon and strontium isotope compositions to the sea-level fluctuations are reported elsewhere in the world, suggesting that the Ordovician sea-level fluctuations of the Tarim Basin were of eustatic implication.

Periodic anoxic shelf in the Early-Middle Ordovician transition:ichnosedimentologic evidence from west-central Utah,USA

Ichnosedimentologic evidence of periodic anoxic shelf in the Early-Middle Ordovician transition includes lower ichnodiversity, shallower bioturbation and burrowing depth (【4 cm), rare domichnia, tinyChondrites occupying shallower or shallowest tiering, widely distributed nodules of limonite pseudomorphs after pyrite, occurrence of trace fossils being closely associated with the storm event layers, and stratigraphic successions with orbital cyclostratigraphic architecture. It is suggested that lower atmospheric oxygen level during the Early Paleozoic, the Ordovician radiation, dramatic transgression and warmer temperatures would result in the periodic anoxia in the Early-Middle Ordovician transition. This episode began at the later Early Ordovician and lasted about 3.4 Ma on the basis of orbital cyclostratigraphy.

Detection and significance of higher thiadiamondoids and diamondoidthiols in oil from the Zhongshen 1C well of the Tarim Basin, NW China

Oil and gas breakthroughs have been achieved in the Zhongshen 1(ZS1) and 1 C(ZS1 C) wells in Cambrian pre-salt from the Tarim Basin in northwest China. However, Middle and Lower Cambrian reservoirs reveal substantial differences in the geochemistry and secondary alteration characteristics between the oils collected from the two wells. High concentrations of thiadiamondoids and diamondoidthiols, including thiatetramantanes, tetramantanethiols, thiapentamantanes, and pentamantanethiols, are detected in the organic sulfur compound fraction of concentrated oil collected from the ZS1 C well, which samples the Lower Cambrian Xiaoerbulake Formation. Higher diamondoids, such as tetramantanes, pentamantanes, hexamantanes, and cyclohexamantane, also occur in the saturate fractions of the concentrated ZS1 C oil. The presence of these compounds is verified by mass spectra analysis and comparison with previous studies. During thermochemical sulfate reduction(TSR), the cage of higher diamondoids is interpreted to open because of sulfur radicals forming open-cage higher diamondoid-like thiols, followed by cyclization that leads to the formation of high thiadiamondoids. Using D_(16)-adamantane as an internal standard, the concentrations of lower diamondoids and thiadiamondoids of non-concentrated Cambrian oil from well ZS1 C are 83874 and8578 μg/g, respectively, which are far higher than Cambrian oil from well ZS1 and most Ordovician oils in the Tarim Basin. The high concentrations of lower thiadiamondoids and occurrence of higher thiadiamondoids and diamondoidthiols support that the oil from well ZS1 C is a product of severe TSR alteration.

Discovery of late Paleozoic fossils in tectonic blocks of the Dabao Formation in the South Qinling Orogenic Belt and their significance

The Dabao Formation in the South Qinling Orogenic Belt was previously regarded as Ordovician in age and consists of clastic matrix and blocks of siltstone,limestone,chert,and volcanic rocks.However,some Middle Devonian corals,conodonts,and other fossil fragments within the limestone blocks were discovered in recent field investigations,indicating that the Dabao Formation was formed during late Paleozoic.Combined with other regional geological data,the Dabao Formation in the Southern Qinling Orogenic Belt is considered to be a late Paleozoic or early Mesozoic accretionary complex.

Conodont diversification during the Ordovician:A perspective from North China and Tarim(Northwestern China)

Review of the literature on Ordovician conodont diversification in palaeoplates of North and Western China reveals that four diversity peaks are present in North China,occurring in the middle Tremadocian,early Floian,late Floian,and late Darriwilian,with three of these peaks(excepting that in the late Floian)also being recorded in Tarim.Three diversification intervals are present in North China,during the Tremadocian,late Floian,early and middle Darriwilian;comparable intervals are observed in the early and late Tremadocian,early Floian,and the Middle Ordovician in Tarim.The main conodont diversification episode in both palaeoplates took place in the Darriwilian,at the time of the Great Ordovician Biodiversification Event.A comparison of conodont diversity patterns in different palaeoplates(North China,Tarim,and South China)demonstrates that conodont radiation events mainly occurred within the Tremadocian,Floian,and Darriwilian.Conodont diversifications in these paleoplates also display some differences.In contrasting with Tarim and South China,North China witnessed a rapid conodont diversification during late Floian time.Conodont diversity in North China and Tarim increased continually and reached a peak in the late Darriwilian,concurrent with a prominent decreasing trend in South China.Differences of conodont diversification in these three palaeoplates may be related to their palaeogeography and tectonic history.When conodont diversifications in North China and Tarim are analysed on the background of palaeoenvironments,the main episodes are seen to be partly coincident with second order sea-level changes,particularly in North China.In general,conodont radiation correlates with large scale transgressions.

Paleogeographic evolution of the Lower Yangtze region and the break of the “platform-slope-basin” pattern during the Late Ordovician

Wide distribution of the black shales and diversification of the graptolite fauna in South China during the Late Ordovician resulted from its unique paleogeographic pattern, which was significantly affected by the paleogeographic evolution of the Lower Yangtze region. In the study, 120 Upper Ordovician sections from the Lower Yangtze region were collected, and a unified biostratigraphic framework has been applied to these sections to establish a reliable stratigraphic subdivision and correlation. Under the unified time framework, we delineate the distribution area of each lithostratigraphic unit, outline the boundary between the sea and land, and reconstruct the paleogeographic pattern for each graptolite zone. The result indicates that, with the uplift and expansion of the ‘Jiangnan Oldland' in the beginning of the late Katian, the oldland extended into the Yangtze Sea gradually from south to north, which finally separate the Jiangnan Slope and the Yangtze Platform. Consequently,the longstanding paleogeographic pattern of "platform-slope-basin" in South China was broken. The paleogeographic change led to sedimentary differentiation among the two sides of the ‘Jiangnan Oldland' during the Late Ordovician. This event also led to the closure of the eastern exit of the Upper Yangtze Sea, and formed a semi-closed, limited and stagnant environment for the development of the organic-rich black shales during the Late Ordovician. The major controlling factors of these paleogeographic changes in the Lower Yangtze region were not consistent from the Katian to the Hirnantian. In the late Katian, the sedimentary differentiation between the east and west sides mostly resulted from regional tectonic movement-the Kwangsian Orogeny.However, during the Hirnantian, the whole Yangtze region became shallower, which was mostly influenced by the concentration of the Gondwana ice sheet and the consequent global sea level drop.

A deep water shelly fauna from the uppermost Ordovician in northwestern Hunan, South China and its paleoecological implications

It is the first time to document the trilobite Mucronaspis(Songxites) wuningensis and the brachiopod ParomalomenaAegiromenella Assemblage from the Xinkailing Bed(Hirnantian, uppermost Ordovician) in Taoyuan and Cili counties,northwestern Hunan Province. Synecological analysis shows that this is a deep water shelly fauna of South China during the Hirnantian. It lived on the upper Jiangnan Slope in northwestern Hunan, adjacent to the southeast margin of the Upper Yangtze Region, and belongs to the Hirnantia fauna with cool and deep water, and low diversity affinity, similar to its contemporary shelly faunas from the southern Shaanxi Slope adjacent to the north margin of the Upper Yangtze Region, the northern Chongqing depression(new name), and the Jiangxi-Anhui-Jiangsu gentle slope of the Lower Yangtze Region. Paleoecologically,it could be attributed to the BA 4–5 benthic regime(about 60–150 m deep, and deepest to 200 m), and was significantly different from the trilobite M.(S.) mucronata and the typical Hirnantia fauna while the latters may have habited in BA 2–3 benthic regimes(about 5–60 m deep). A new paleogeographic distribution pattern of the Hirnantian shallow and deep water shelly faunas of South China is herein proposed for the first time. Assuming that the depositional rate was constant in northwestern Hunan during the end Ordovician, the duration of the Xinkailing Bed might be only 12 thousand years according to the thickness of the Wufeng Formation and the absolute age values of those relevant graptolitic biozones. Such a short time interval may indicate that the global environmental change during the crisis was much shorter than previously thought, and its influence on the deep water regime was significantly shorter than that on the shallow water regime.

Temporal distribution of piperocks in Cambrian and Ordovician: A coevolutionary process with changes of paleoenvironment

Piperock, a kind of characteristic ichnofabrics in Phanerozoic, was thought to decline gradually from Cambrian to Ordovician. A new compilation on the occurrences of the Cambrian and Ordovician piperocks of China and the world shows that piperocks generally flourished in Cambrian and declined in Ordovician, but a sharp decrease occurred during Middle and Late Cambrian. The case-study on the piperocks from the Lower-Middle Ordovician Hongshiya Formation at Dabaochang of Qiaojia, northern Yunnan Province, Southwest China indicates that the forming and preservation of piperocks were controlled by the depositional environment, the intensities of predation, competition, bioturbation, and the contents of nutrition and oxygen in watermass. A careful study on the development of the Cambrian and Ordovician piperocks suggests that the decrease of nearshore siliciclastic sediments and the low contents of oxygen and nutrition in the watermass may have contributed to the decline of piperocks in Middle and Late Cambrian.

Application of Spatial Database in Quantitative Analysis of Litho-Paleogeography—A Case Study of a Middle Ordovician Sequence Interval in the Ordos Basin

Abstract In the study of sequence stratigraphy and litho-paleogeography, quantitative analysis, precise calculation and detailed comparison of tremendous geological data, such as field profiles, logging records and seismic curves from different areas, are the basic requirements. In order to obtain a more reliable and precise result, this paper presents a novel method that combines spatial database analysis with the single-factor mapping technology to establish sequence stratigraphical succession and to map the Ordovician litho-paleogeography of the Ordos Basin, one of the largest oil-gas bearing basins in North China Platform. By using this method, all of the related basic geological data can be quantitatively analyzed and effectively managed. Various attributes of the basic stratigraphic units and their characters, such as sequence thickness, penecontemporaneous dolostone content, shallow water parget content, and terrigenous material content, can be fully utilized statistically in facies analysis and in mapping. Based on this analysis, this paper has be exerted single-factor isopachous mapping quantitatively for each of the Ordovician sequences in the basin, and finally synthesized multiple factors to reconstruct the litho-paleogeography for each of the sequence intervals. The study shows that the proposed method is quite effective and has a much higher resolution in recognizing litho-paleogeographic subunits compared with traditional ways. For example, in one of the Middle Ordovician sequence intervals （SQ19 in the Lower Majiagou Formation） of the Ordos Basin, the authors have successfully developed a mathematical formula to divide the distribution of various facies units substantially, such as old lands, submarine uplifts, supratidal zones, intertidal zones and subtidal zones.