Modern tectonic stress field in the Chinese mainland inverted from focal mechanism solutions

IntroductionTheinversionapproachofregionalstressfielddevelopedinrecent10to20yearsprovidesausefultoolforstudyingthemeanstressinagivenregion(Angeller,1979;Ellsworth,1981,Xu,Ge,1984).Becauseitusesmultitudinousfaultsinsteadofsinglefault,itcanremovetheinhomogeneityoflocalmediumsoastorevealtheregionalstressinformation.Besides,thismethodproducesaRvalue,whichisdefinedby(O-2--q)/(q--q),andmaydescribestherelativemagnitUdeofintermediateprincipalstress,whereq,acand%arethemaximum,theintermediateandthemi…     

贻贝超氧化物歧化酶的分离纯化和部分性质

采用热变性－硫酸铵分级沉淀－Ｓｅｐｈａｄｅｘ Ｇ－１００和ＤＥ５２柱层析的方法从贻贝中分离纯化铜锌超氧化物歧化酶,并对其部分性质进行分析鉴定。结果该酶的比活力为９４５３．３Ｕ／ｍｇ（ｐｒｏｔｅｉｎ）,提纯倍数为６０９．９,对ＫＣＮ和Ｈ２Ｏ敏感,Ｔ氏液和ＳＤＳ对酶活性没影响,对热较稳定。     

Deglacial palaeoclimate at Puerto del Hambre,subantarctic Patagonia,Chile

The primary objective of this study is to further substantiate multistep climatic forcing of late‐glacial vegetation in southern South America. A secondary objective is to establish the age of deglaciation in Estrecho de Magallanes–Bahía Inútil. Pollen assemblages at 2‐cm intervals in a core of the mire at Puerto del Hambre (53°36′21″S, 70°55′53″W) provide the basis for reconstructing the vegetation and a detailed account of palaeoclimate in subantarctic Patagonia. Chronology over the 262‐cm length of core is regulated by 20 AMS radiocarbon dates between 14 455 and 10 089 ¹⁴C yr BP. Of 13 pollen assemblage zones, the earliest representing the Oldest Dryas chronozone (14 455–13 000 ¹⁴C yr BP) records impoverished steppe with decreasing frequencies and loss of southern beech (Nothofagus). Successive 100‐yr‐long episodes of grass/herbs and of heath (Empetrum/Ericaceae) before 14 000 ¹⁴C yr BP infer deglacial successional communities under a climate of increased continentality prior to the establishment of grass‐dominated steppe. The Bølling–Allerød (13 000–11 000 ¹⁴C yr BP) is characterised by mesic grassland under moderating climate that with abrupt change to heath dominance after 12 000 ¹⁴C yr BP was warmer and not as humid. At the time of the Younger Dryas (11 000–10 000 ¹⁴C yr BP), grass steppe expanded with a return of colder, more humid climate. Later, with gradual warming, communities were invaded by southern beech. The Puerto del Hambre record parallels multistep, deglacial palaeoclimatic sequences reported elsewhere in the Southern Andes and at Taylor Dome in Antarctica. Deglaciation of Estrecho de Magallanes–Bahía Inútil is dated close to 14 455 ¹⁴C yr BP, invalidating earlier dates of between 15 800 and 16 590 ¹⁴C yr BP. Copyright © 2000 John Wiley & Sons, Ltd.     

Decline of the mid‐ to late Holocene forests in China: climatic change or human impact?

Fossil pollen data from China indicate continued forest decline during the mid‐ to late Holocene in most regions north of the Yangtze River. The earliest forest decline can be detected ca. 5000 yr BP in the middle and lower Yellow River regions. North, northeast and northwest from this region, forest decline became progressively later, and almost no decline took place in the northernmost part of northeast China and in the remote areas of west China during the last 5000 yr. Climate changes could hardly account for the temporal and spatial patterns of the forest decline. Instead, anthropogenic disturbance may have been of overwhelming importance. Ancient agriculture and high‐density settlement expanded outward from the middle and lower Yellow River regions in similar patterns to those of forest change. This study also indicates that land‐use and land‐cover changes may have started in the early stage of Chinese civilization in an extensive area of the country. Copyright © 2000 John Wiley & Sons, Ltd.     

Stable isotopes of pedogenic carbonates from the Somma–Vesuvius area,southern Italy,over the past 18 kyr: palaeoclimatic implications

Stable isotopes were measured in the carbonate and organic matter of palaeosols in the Somma–Vesuvius area, southern Italy in order to test whether they are suitable proxy records for climatic and ecological changes in this area during the past 18000 yr. The ages of the soils span from ca. 18 to ca. 3 kyr BP. Surprisingly, the Last Glacial to Holocene climate transition was not accompanied by significant change in δ¹⁸O of pedogenic carbonate. This could be explained by changes in evaporation rate and in isotope fractionation between water and precipitated carbonate with temperature, which counterbalanced the expected change in isotope composition of meteoric water. Because of the rise in temperature and humidity and the progressive increase in tree cover during the Holocene, the Holocene soil carbonates closely reflect the isotopic composition of meteoric water. A cooling of about 2°C after the Avellino eruption (3.8 ka) accounts for a sudden decrease of about 1‰ in δ¹⁸O of pedogenic carbonate recorded after this eruption. The δ¹³C values of organic matter and pedogenic carbonate covary, indicating an effective isotope equilibrium between the organic matter, as the source of CO₂, and the pedogenic carbonate. Carbon isotopes suggest prevailing C₃ vegetation and negligible mixing with volcanogenic or atmospheric CO₂. Copyright © 2000 John Wiley & Sons, Ltd.     

Late quaternary palaeoclimate in the savannas of South America

The paper reviews Late Quaternary palynological evidence from eight sites in the savannas of northern South America. The sites reviewed are Lake Valencia (10°N), Carajas (6°S), Aguas Emendadas (15°S), Crominia (17°S), Salitre (19°S), Lagoa de Serra Negra (18°S), Lagoa Santa (20°S) and Lagoa dos Olhos (20°S). Four of the sites show evidence for a climate more humid than at present from ca. 36 ka BP to ca. 22–18 ka BP. Maximum dryness was reached at 14 ka to 10.5 ka BP at Lake Valencia. There was an increase in moisture from 8.8 ka BP at Lake Valencia and from 7 ka BP in Central Brazil. The presence of charcoal indicates human impact from ca. 8.6 ka BP. ©1997 John Wiley & Sons, Ltd.     

涉县地震台水管倾斜仪常见干扰分析

对于涉县地震台水管倾斜仪观测资料,根据地球物理数据跟踪分析方法,将干扰源按照自然因素、场地环境因素、观测系统、地球物理事件等类型进行分析,并给出数据处理建议。     

长江中华绒螯蟹的资源与养殖现状及其种质保护

根据中华绒螯蟹的资源及其养殖现状,分析了我国目前各水系河蟹的种质变异及其河蟹幼蟹培育和成蟹养殖中存在的问题,针对中华绒螯蟹 种质保护的要求,就防止河蟹幼蟹性早熟及和蟹养殖的遗传污染与种质混杂等问题,提出了对长江河蟹品质保持的初步设想。     

Palaeoclimate indicators (clay minerals,calcareous nannofossils,stable isotopes) compared from two successions in the late Jurassic of the Volga Basin (SE Russia)

A study of clay mineral and calcareous nannofossil abundances in late Jurassic–early Cretaceous sediments from the Volga Basin, SE Russia, is presented. From these results, we are able to compare some general patterns of mineralogical and palaeontological change for the Volga Basin to the palaeoclimate models developed for northern Europe and beyond. The two successions examined comprise calcareous mudstones with black organic‐rich shale horizons, overlain by a series of phosphatic silty sands. Clay mineralogical results show a progressive decrease in kaolinite and the concomitant increase of smectite and illite through the middle Volgian, followed by an abrupt increase in kaolinite in the late Volgian. The clay mineral evidence suggests increasing aridity at the end of the Jurassic, similar, in part, to many western European successions. Because of differential settling of clay minerals, superimposed upon this possible climatic signature is likely to be the effect of relative sea‐level change. Calcareous nannofossil analysis from a single section reveals a shift through the middle Volgian from low nutrient, warm water assemblages dominated by Watznaueria to cooler surface water and high nutrient assemblages dominated by Biscutum constans. These observations suggest that increased aridity is also associated with climatic cooling. Black shales are associated with increased productivity, higher sea levels and increases in smectite content. Hence, periods of low (chemical) hinterland weathering during semi‐arid conditions are paradoxically associated with relatively nutrient‐rich waters, and organic‐rich shales. Comparison of published carbon and oxygen stable isotope results from this and other sections to the clay mineral and nannofossil data confirms the palaeoclimatic interpretation. This study significantly improves the published biostratigraphically constrained clay mineral database for this time period, because other European and North American successions are either non‐marine (and thus poorly dated), absent (through penecontemporaneous erosion) or condensed. Copyright © 2002 John Wiley & Sons, Ltd.     

中全新世以来杭州湾古气候、环境变迁及对良渚文化的可能影响

利用在杭州湾西部良渚古城遗址附近获取的沉积物岩芯,试图通过高精度加速器质谱(AMS)测年以及多气候、环境代用指标的分析来揭示中全新世以来良渚地区的气候、环境变迁历史,进而讨论其与良渚文化消亡的可能联系.对沉积物的有孔虫分析显示:在大约7500 5200 cal a B.P.期间,研究区为富含有孔虫的潮滩相沉积环境;而约5200 cal a B.P.以来,有孔虫逐渐消失,反映了研究区逐渐脱离海水影响成陆的过程.孢粉记录显示:研究区在约5200 5000 cal a B.P.期间以常绿、落叶阔叶植被为主,伴有少量针叶植被,气候总体上相对暖湿.而在大约5000 4000 cal a B.P.期间,针叶植被的相对增加总体反映了趋于凉湿的气候.在约4000 1500 cal a B.P.期间,虽然常绿阔叶植被重新占据相对优势,但总体呈现逐渐减少的趋势,同时落叶阔叶类植被增加,表明了趋暖偏干的气候;同时,该段水生草本、蕨类植被和藻类的相对增加或许反映了研究区下垫面开始沼泽、湿地化的趋势.约1500 400 cal a B.P.期间,木本植被整体呈减少趋势,陆生草本植被则大量增加,针叶植被进一步减少,表明气候进一步趋干;同时,水生草本和藻类的急剧增加,可能反映了湿地化加剧的状况.最近约400 cal a B.P.以来,针叶植被急剧增加,常绿阔叶植被减少,可能反映了气候突然变冷的过程.岩芯下段禾本科孢粉(40μm)的出现与研究区脱海成陆的时间相吻合,这表明良渚时期(大约5000 4000 cal a B.P.)研究区水稻种植已有一定规模.但在大约4000 cal a B.P.前后的良渚文化末期,禾本科孢粉浓度一度出现降低,这可能反映了研究区人类活动强度的减弱,其与良渚文明衰落的时间基本吻合.总体上看,这一变化发生在趋干的气候背景以及沼泽化、湿地化加剧的下垫面条件下,暗示了气候、环境因素对良渚文明的衰落可能具有重要影响.