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Modern Black Sea oceanography applied to the end-Permian extinction event

Journal of Palaeogeography 2015年第1期4卷 52-62页

作者： steve kershaw Institute for the Environment Health and Societies Brunel UniversityKingston LaneUxbridge Middlesex UB8 3PH UK

The modern Black Sea has a mixed upper layer in the top 150-200 m of the water column, below which the water is anoxic, separated from the mixed layer by a redox boundary. There is limited vertical movement of water. Pyrite framboids form in the water column of the anoxic zone, then have been traditionally interpreted to sink immediately and accumulate in the sediments of the Black Sea. Thus the occurrence of framboids in sediments in the rock record is widely interpreted to indicate poorly oxygenated to anoxic conditions in ancient environments. However, in the Permian-Triassic boundary （PTB） microbialites of South China, which formed in shallow marine conditions in contact with the atmosphere, the published occurrence of framboids is inconsistent with abundant gastropod and ostracod shells in the microbialite. Furthermore, in the modern Black Sea, （a） framboids may be suspended, attached to organic matter in the water column, thus not settle to the sea floor immediately after formation; and （b） the redox zone is an unstable complex area subject to rapid vertical water movement including occasional upwelling. The model presented here supposes that upwelling through the redox zone can lead to upward transport of suspended pyrite framboids into the mixed layer. Advective circulation could then draw suspended framboids onto the shelf to be deposited in oxygenated sediments. In the Permian-Triassic transition, if framboids were upwelled from below the redox boundary and mixed with oxygenated waters, sediment deposited in these conditions could provide a mixed signal for potentially misleading interpretations of low oxygen conditions. However, stratigraphic sampling resolution of post-extinction microbialites is currently insufficient to demonstrate possible separation of framboid-bearing layers from those where framboids are absent. Profound differences between microbialite constructors and sequences between the western and eastern Tethys demonstrate barriers to migra

关键词： mass extinction Permian-Triassic boundary microbialite ostracods gastro-pods anoxia Black Sea

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Palaeozoic stromatoporoid futures:A discussion of their taxonomy,mineralogy and applications in palaeoecology and palaeoenvironmental analysis

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Journal of Palaeogeography 2013年第2期2卷 163-182页

作者： steve kershaw Institute for the Environment Halsbury BuildingBrunel UniversityUxbridgeMiddlesexUB8 3PHUK

Palaeozoic stromatoporoids are calcified sponges common between Middle Ordovician and Late Devonian times in reefs and related *** work is well known,but controversial because of conflict between classification schemes based on the calcareous skeleton versus spicules(which are almost completely lacking in Palaeozoic stromatoporoids);however,lower-level taxonomy(at genus-level) of the calcareous skeleton is considered reliable to be applied in palaeobiological *** of stromatoporoid ecology is poorly developed,such that comprehensive information is available for only a few case studies,in some Silurian and Devonian *** an overall understanding of stromatoporoid responses to environmental conditions has not yet been achieved,although stromatoporoids were likely able to deal with fine grained sediment where they mostly *** stromatoporoid genera have only certain growth forms,so future focus on the use of low-level taxonomy in ecological studies,by comprehensive sampling in high-resolution studies,may establish the relationships between stromatoporoids and their *** organisms and growth banding in stromatoporoids are aspects that have great potential in such *** of stromatoporoids remains poorly *** of their apparent state of preservation(ranging from apparently well-preserved to complete loss of calcareous skeleton features) all stromatoporoids are in fact substantially *** underwent a peculiar diagenesis,whereby the calcareous skeleton and gallery cements of all stromatoporoids are overprinted by irregular elongated calcite crystals arranged normal to the growth laminations,most clearly visible in cross-polarized *** cooccur with mollusc shells that are always either fully recrystallized or dissolved(present as internal and external moulds);this difference means that while molluscs are likely under-represented in the fossil record,stromatoproids

关键词： stromatoporoid Palaeozoic palaeoecology taxonomy biomineralogy *

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Reservoir Potential of Silurian Carbonate Mud Mounds in the Southern Sichuan Basin,Central China

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Acta Geologica Sinica(English Edition) 2006年第5期80卷 684-692页

作者： ZHAO Wenzhi YANG Xiaoping steve kershaw ZHANG Baomin Research Institute of Petroleum Exploration and Development CNPC Xueyuan Road Beijing 100083 China Department of Geography and Earth Science Brunel University Uxbridge UB8 3PH UK

Lower Silurian mud mounds of the Shinuilan Formation, located in the southern Sichuan Basin, China, have developed in open shelf settings in deeper water than shallow-water reef-bearing limestones that occur in the region. An integration of the outcrop, drill data and seismic profiles show that contemporaneous faults have controlled the boundary and distribution of the sedimentary facies of Lower Silurian rocks in the southern Sichuan Basin. Mounds appear to have developed in the topographic lows formed by synsedimentary faulting, on the sheff of the Yangtze Platform. Average mound thickness is 20 m, maximum 35 m. Mounds are composed mainly of micrite, possibly microbially bound, and are overlain by shales. Mound tops are preferentially dolomitized, with the Mg^2＋ source probably from the clay content of the mound-top carbonate. Microfacies analysis and reconstruction of the diagenetic history reveal that the mound tops have higher porosity, and are gas targets; in contrast, mound cores and limbs show pores filled by three generations of calcite cement, and therefore have a low gas potential.

关键词： sedimentary facies reservoir mud mound Early Silurian Sichuan Basin China

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陕南川北志留系特列奇阶宁强组礁相中的微生物岩和钙藻

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微体古生物学报 2002年第2期19卷 170-177页

作者：李越穆西南 kershaw steve 中国科学院南京地质古生物研究所南京210008 英国Brunel大学地理地球科学系

分布于扬子区西北缘宁强—广元地区志留系宁强组以约三千米厚的浅水相泥页岩、海相红层夹灰岩为特征 ,部分灰岩层段中发育生物礁。通过对礁灰岩的微相分析表明 ,菌藻类可通过四种方式参与造礁过程 :1)叠层石 ;2 )凝块岩 ;3)核形石 ;4 )... 详细信息

分布于扬子区西北缘宁强—广元地区志留系宁强组以约三千米厚的浅水相泥页岩、海相红层夹灰岩为特征 ,部分灰岩层段中发育生物礁。通过对礁灰岩的微相分析表明 ,菌藻类可通过四种方式参与造礁过程 :1)叠层石 ;2 )凝块岩 ;3)核形石 ;4 )钙藻碎屑堆积。其中以叠层石和凝块岩最为常见 ,它们对灰泥基质起显著的粘结作用。而核形石和钙藻相对较少。

关键词：陕南川北志留系特列奇阶宁强组礁相微生物岩钙藻生物礁

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构造及海面波动对四川盆地志留纪生物礁的控制

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石油学报 1999年第3期20卷 19-24页

作者：张廷山蓝光志 steve kershaw 南京大学地球科学系西南石油学院勘探系英国Brunel大学地科系

通过上扬子板块区各大地构造单元、四川盆地南北缘志留系锶同位素、碳氧同位素分析所显示的海平面变化及其与生物礁发育的关系分析得出：（１）志留纪时，四川盆地南北缘都分别为受上扬子板块内部稳定古隆起（古陆）控制的陆源碎屑—碳... 详细信息

通过上扬子板块区各大地构造单元、四川盆地南北缘志留系锶同位素、碳氧同位素分析所显示的海平面变化及其与生物礁发育的关系分析得出：（１）志留纪时，四川盆地南北缘都分别为受上扬子板块内部稳定古隆起（古陆）控制的陆源碎屑—碳酸盐岩缓坡环境，在靠近古陆的地区生物礁发育，而远离古陆时，由于水体逐渐加深，生物礁则不发育；（２）盆地南缘锶同位素从龙马溪组至石牛栏组呈波动式下降，反映出海平面从龙马溪组至石牛栏组总体趋势是逐渐上升，至韩家组，锶同位素值迅速上升，海平面降低；盆地南缘石牛栏组的碳同位素呈波动上升。盆地北缘王家湾组及宁强组的碳同位素也呈逐渐增加的特征。碳同位素演化显示盆地南北缘从龙马溪组至宁强组都处于海进期，而宁强组沉积时达高水位期，以后海平面迅速下降；虽然氧同位素受埋藏成岩作用影响较大，呈较大的负偏移，但其系统变化特征也可间接反映当时的海平面上升过程；生物礁在海进期及高水位期发育，且以在高水位期发育得最好。

关键词：大地构造生物礁志留纪四川盆地海面波动

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黔北凤岗硐卡拉奥陶系湄潭组中灰岩:典型的暖水相

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微体古生物学报 2010年第2期27卷 150-158页

作者：李启剑李越 steve kershaw 张园园邓小杰中国科学院南京地质古生物研究所南京210008 Institute for the Environment Brunel UniversityUxbridgeMiddlesex

黔北凤岗硐卡拉剖面下—中奥陶统湄潭组泥岩、粉砂岩中夹含一套47.5m的连续灰岩建造,是区内迄今所测得厚度最大的"中灰岩"段。中灰岩的岩石学特征显示其成分多为分异度很高的生屑、鲕粒(豆粒)和核形石等,颗粒破碎程度偏高,丰度高时可达... 详细信息

黔北凤岗硐卡拉剖面下—中奥陶统湄潭组泥岩、粉砂岩中夹含一套47.5m的连续灰岩建造,是区内迄今所测得厚度最大的"中灰岩"段。中灰岩的岩石学特征显示其成分多为分异度很高的生屑、鲕粒(豆粒)和核形石等,颗粒破碎程度偏高,丰度高时可达颗粒支撑,灰泥基质和亮晶方解石胶结均有。这些颗粒堆积形成中—高能带生屑、内碎屑浅滩,纵向上略显旋回,亦见两层较薄含瓶筐石格架的生物层。这些特征皆属浅海带暖水型沉积的标志,将该剖面的湄潭组中灰岩与之同期的大湾组和紫台组中的灰岩相比较,后者形成于偏深的相带,灰泥和泥级、粉砂级陆源碎屑含量高,也缺乏典型的暖水成因标志,故可推知扬子区陆表海的灰岩沉积相存在深度控制的海水温差分异现象。

关键词：瓶筐石生物层浅滩中灰岩湄潭组下—中奥陶统硐卡拉凤岗黔北

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四川盆地南部志留系碳酸盐泥丘储层发育特征

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地质学报 2006年第10期80卷 1615-1615页

作者：赵文智杨晓萍 steve kershaw 中国石油勘探开发研究院北京100083

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Digital neuromorphic technology: current and future prospects

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National Science Review 2024年第5期11卷 10-11页

作者： steve Furber Department of Computer Science The University of Manchester

Neuromorphic technology has diversified considerably from its origins in the seminal work by Carver Mead and his group at Caltech in the 1980s [1]. That early work focussed on the analogy between the equations describing the flow of ions in biological neurons and the equations describing the flow of carriers in field-effect transistors operating in the subthreshold region.

关键词： technology current future digital neuromorphic prospects

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Improving reflectance estimation by BRDF-consistent region clustering

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Progress in Natural Science:Materials International 2006年第3期16卷 313-320页

作者： LIN steve Beijing 100080 China Visual Computing Group Microsoft Research Asia

Previous studies in reflectance estimation generally require prior segmentation of an image into regions of uniform reflectance. Due to the measurement noise and limited sampling of the BRDF (bi-directional reflectance function) directions, such estimated results of reflectance are not accurate. In this paper, we propose a novel method for reducing uncertainty in reflectance estimates by merging image regions which have consistent reflectance observations. Each image region acts as a reflectance subspace, so merging of the image regions can result in subspace reduction. We propose a Bayesian segmentation framework to decrease the reflectance uncertainty by using novel merging criteria. Finally, a maximum likelihood reflectance estimation is made for each resulting image region. Experimental results verify the feasibility and superiority of this reflectance-oriented region merging method.

关键词： texture shading grouping and segmentation reflectance estimation BRDF uncertainty.

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Quantitative Absolute Continuity of Harmonic Measure and the Dirichlet Problem: A Survey of Recent Progress

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Acta Mathematica Sinica,English Series 2019年第6期35卷 1011-1026页

作者： steve HOFMANN Department of Mathematics University of Missouri

It is a well-known folklore result that quantitative, scale invariant absolute continuity(more precisely, the weak-A∞ property) of harmonic measure with respect to surface measure, on the boundary of an open set Ω ? R^(n+1) with Ahlfors–David regular boundary, is equivalent to the solvability of the Dirichlet problem in Ω, with data in L^p (?Ω) for some p < ∞. Drawing an analogy to the famous Wiener criterion, which characterizes the domains in which the classical Dirichlet problem, with continuous boundary data, can be solved, one may seek to characterize the open sets for which L^psolvability holds, thus allowing for singular boundary *** has been known for some time that absolute continuity of harmonic measure is closely tied to rectifiability properties of ?Ω, but also that rectifiability alone is not sufficient to guarantee absolute continuity. In this note, we survey recent progress in this area, culminating in a geometric characterization of the weak-A∞ property, and hence of solvability of the L^p Dirichlet problem for some finite p. This characterization, obtained under rather optimal background hypotheses, follows from a combination of the present author's joint work with Martell, and the work of Azzam, Mourgoglou and Tolsa.

关键词： Harmonic measure Poisson kernel uniform rectifiability weak local John condition big pieces of chord-arc domains Carleson measures

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