Palaeoproterozoic mid‐basin inversion in the northern Mt Isa terrane,Queensland

The Mellish Park Syncline is located in the northern part of the Mt Isa terrane. It has an axial trace that transects the remnants of the unconformity‐bounded Palaeoproterozoic Leichhardt and Isa Superbasins. The syncline is separated into a lower and upper component based upon variation in fold geometry across the basin‐bounding unconformity. The lower syncline, in the Leichhardt Superbasin, is tight and has an inclined west‐dipping axial plane. The upper syncline, in the Isa Superbasin, is open and upright. The geometry of the lower syncline is a consequence of a period of shortening and basin inversion which post‐dated the Leichhardt Rift Event (ca 1780–1740 Ma) and pre‐dated the Mt Isa Rift Event (ca 1710–1655 Ma), forming an open and upright north‐oriented syncline. Subsequent southeast tilting and half‐graben development during the Mt Isa Rift Event resulted in the lower syncline being tilted into its inclined geometry. Sequences of the Isa Superbasin were then deposited onto the eroded syncline. The geometry of the upper syncline reflects regional east‐west shortening during the Isan Orogeny (ca 1590–1500 Ma). The position of the upper syncline was largely controlled by the pre‐existing lower syncline. At this time the lower syncline was reactivated and tightened by flexural slip folding.     

Long-Term Variability of Volume and Heat Transport in the Nordic Seas: A Model Study

This article presents results from a model study of interannual and decadal variability in the Nordic Seas. Fifty years of simulations were conducted in an initial condition ensemble mode forced with the National Centers for Environmental Prediction (NCEP) reanalysis. We studied two major events in the interannual and interdecadal variability of the Nordic Seas during the past fifty years: the Great Salinity Anomaly in the 1960s and early 1970s and the warming of the Arctic and subarctic oceans in the late 1990s.

Previous studies demonstrated that the Great Salinity Anomaly observed in the subarctic ocean in 1960 was originally generated by intensified sea-ice and freshwater inflow from the Arctic Ocean. Our model results demonstrate that the increase in the transport of fresh and cold waters through Fram Strait in the 1960s was concurrent with a reduction in the meridional water exchange over the Greenland–Scotland Ridge. The resulting imbalance in salinity and heat fluxes through the strait and over the ridge also contributed to the freshening of the water masses of the Nordic Seas and intensified the Great Salinity Anomaly in the Nordic Seas.

The warming of the Atlantic Waters in the Nordic Seas and Arctic Ocean during the past two decades had an important impact on the variability of these two ocean basins. Some previous observational and model studies demonstrated that the warming of the subpolar Atlantic Ocean in the late 1990s and the meridional transport of the Atlantic Water mass (AW) into the Nordic Seas and Arctic Ocean contributed to this process. At the same time, observations show that the warming of the AW in the Nordic Seas started in the 1980s (i.e., earlier than the warming of the subpolar North Atlantic Ocean). Our model results suggest that this process was triggered by an imbalance in the lateral heat fluxes through Fram Strait and over the Greenland–Scotland Ridge. In the late 1980s the AW transport over the Greenland–Scotland Ridge was stronger than normal while the exchange through Fram Strait was close to normal. The related imbalance in the lateral heat fluxes through the strait and over the ridge warmed the Nordic Seas and caused an increase in the temperature of the AW inflow to the Arctic Ocean in the late 1980s (i.e., about a decade earlier than the warming of the source of the AW in the subpolar North Atlantic Ocean). Thus the model results suggest that the imbalance in lateral heat and salinity fluxes through the strait and over the ridge connecting the Nordic Seas to the North Atlantic and Arctic oceans could amplify the interannual variability in the subarctic ocean.

[Traduit par la rédaction] Cet article présente les résultats d'une étude par modèle de la variabilité interannuelle et décennale dans les mers nordiques. Nous avons effectué des simulations sur une période de cinquante ans en mode d'ensemble de conditions initiales forcé avec les réanalyses des NCEP (National Centers for Environmental Prediction). Nous avons étudié deux événements majeurs survenus dans la variabilité interannuelle et décennale des mers nordiques au cours des cinquante dernières années : la grande anomalie de salinité des années 1960 et du début des années 1970 et le réchauffement des océans Arctique et subarctique vers la fin des années 1990.

Des études précédentes ont démontrées que la grande anomalie de salinité observée dans l'océan subarctique en 1960 a été causée par une intensification de l'apport de glace de mer et d'eau douce depuis l'océan Arctique. Les résultats que nous avons obtenus du modèle montrent que l'accroissement du transport d'eau douce et froide à travers le détroit de Fram dans les années 1960 s'est produit en même temps qu'une réduction dans l’échange méridien d'eau au-dessus de la crête Groenland–Écosse. Le déséquilibre résultant dans les flux de salinité et de chaleur à travers le détroit et au-dessus de la crête a aussi contribué à l'adoucissement des masses d'eau des mers nordiques et a intensifié la grande anomalie de salinité dans les mers nordiques.

Le réchauffement des eaux atlantiques dans les mers nordiques et dans l'océan Arctique au cours des deux dernières décennies a eu un impact important sur la variabilité de ces deux bassins océaniques. Des études observationnelles et par modèle précédentes ont établi que le réchauffement de l'océan Atlantique subpolaire dans les années 1990 et le transport méridien de la masse d'eau atlantique dans les mers nordiques et dans l'océan Arctique ont contribué à ce processus. En même temps, les observations montrent que le réchauffement des eaux atlantiques dans les mers nordiques a commencé dans les années 1980 (c.–à–d. plus tôt que le réchauffement de l'océan Nord-Atlantique subpolaire). Les résultats du modèle suggèrent que ce processus a été déclenché par un déséquilibre dans les flux de chaleur latéraux à travers le détroit de Fram et au-dessus de la crête Groenland–Écosse. À la fin des années 1980, le transport des eaux atlantiques au-dessus de la crête Groenland–Écosse était plus fort que la normale alors que l’échange à travers le détroit de Fram était près de la normale. Le déséquilibre résultant dans les flux de chaleur latéraux à travers le détroit et au-dessus de la crête a réchauffé les mers nordiques et causé une augmentation de la température des eaux atlantiques parvenant à l'océan Arctique à la fin des années 1980 (c.-à-d. environ une décennie avant le réchauffement de la source d'eaux atlantiques dans l'océan Nord-Atlantique subpolaire). Donc, les résultats du modèle suggèrent que le déséquilibre dans les flux de chaleur et de salinité latéraux à travers le détroit et au-dessus de la crête reliant les mers nordiques à l'Atlantique Nord et à l'Arctique pourrait amplifier la variabilité interannuelle dans l'océan subarctique.     

云南新平县双沟蛇绿岩的初步研究

双沟蛇绿岩由基底岩石、辉长—辉绿岩和玄武岩三部分组成。岩相学和地球化学研究表明,双沟斜长二辉橄榄岩中存在地幔交代作用的证据,属于浸染橄榄岩(impregnated peridotite)。蛇绿岩岩石组合中缺少超镁铁质堆晶岩和席状岩墙群,而辉绿岩和玄武岩的化学成分与MORB相拟,表明双沟蛇绿岩的形成机制与大洋中脊环境类似,但岩浆房很小,扩张速度缓慢,推测相当于哀牢山古特提斯小洋盆扩张早期的裂谷阶段的产物。     

Historical changes in sediments of Pyramid Lake,Nevada, USA: consequences of changes in the water balance of a terminal desert lake

Sediment cores from the shallow and deep basins of Pyramid Lake, Nevada, revealed variations in composition with depth reflecting changes in lake level, river inflow, and lake productivity. Recent sediments from the period of historical record indicate: (1) CaCO₃ and organic content of sediment in the shallow basin decrease at lower lake level, (2) CaCO₃ content of deep basin sediments increases when lake level decreases rapidly, and (3) the inorganic P content of sediments increases with decreasing lake volume. Variations in sediment composition also indicate several periods for which productivity in Pyramid Lake may have been elevated over the past 1000 years. Our data provide strong evidence for increased productivity during the first half of the 20th Century, although the typical pattern for cultural eutrophication was not observed. The organic content of sediments also suggests periods of increased productivity in the lake prior to the discovery and development of the region by white settlers. Indeed, a broad peak in organic fractions during the 1800's originates as an increase starting around 1600. However, periods of changing organic content of sediments also correspond to periods when inflow to the lake was probably at extremes (e.g. drought or flood) indicating that fluctuations in river inflow may be an important factor affecting sediment composition in Pyramid Lake.     

Interpretation of210Pb profiles and verification of the CRS dating model in PIRLA project lake sediment cores

This paper reports results and analysis of²¹⁰Pb-activity measurements in 51 lake-sediment cores from 32 lakes in the four PIRLA (Paleoecological Investigations of Recent Lake Acidification) project regions (Adirondack Mountains [New York], Northern New England, Northern Florida, and the Northern Great Lakes States). General application of the Constant Rate of Supply (Constant Flux) model for²¹⁰Pb dating is valid for lakes in the PIRLA study, although application of the model is equivocal in a few lakes.²¹⁰Pb inventories and profiles are replicable among closely spaced cores within a lake. Specific²¹⁰Pb activity in surface sediments is negatively correlated with bulk sediment accumulation rate in seepage lakes, but not in drainage lakes. Drainage lakes with lower pH have lower unsupported²¹⁰Pb inventories in sediments, but the relationship does not occur in seepage lakes.²¹⁰Pb profiles in only seven of the cores, all from either the Adirondacks or the northern Great Lakes states, exhibit exponential decay curves. Deviations from an exponential profile include a flattening of the profile in the top few cm or excursions of one or a few measurements away from an exponential curve.²¹⁰Pb dates typically agree with other chronostratigraphic markers, most of which are subject to greater uncertainty. Several hypotheses, including sediment mixing, hydrologic regime, sediment focusing, and acidification, are proposed to explain variation of²¹⁰Pb distribution among lakes and regions. Hydrologic factors exert control on unsupported²¹⁰Pb inventories in PIRLA lakes, and there is a strong focusing effect in drainage lakes but a weak focusing effect in seepage lakes.This is the third of a series of papers to be published by this journal following the 20^th anniversary of the first application of²¹⁰Pb dating of lake sediments. Dr P. G. Appleby is guest editing this series.     

8680 X荧光光谱仪与长城0520-CH计算机的数据通信

8680X荧光光谱仪采用RSX-11M多用户操作系统。本文将0520计算机作为RSX-11M主机的一个从属终端,设计了相应软件与8680联机。无需修改任何硬件,在0520上可以执行RSX-11M的全部操作指令,并且只要8680主机不关闭,0520计算机即可随时从8680的磁盘上读取数据而不需事先与8680的操作者约定,传送数据快速、准确。     

Multispectral remote sensing of biomass burning in West Africa

Remote sensing measurements provide a vauable means of determining the extent of burning areas and of estimating the overall distribution of pollutant sources (identified from experimental studies) in time and space. This distribution has to be taken into account in the boundary conditions of chemistry atmospheric models.Recent methods developed for the remote sensing of active fires in tropical or temperated forest zones, have been found to be completely inadequate for fire detection on West African savannas. In order to accurately estimate the active fire distribution in the function of different sorts of West African savannas (Sahelian, Sudanian and Guinean) and forests, a multispectral methodology has been developed based on NOAA/11-AVHRR satellite data, with the purpose of eliminating as much as possible the problems related to large surface heterogeneity, confusion and bias, produced by clouds, smoke, haze, background emissivities, etc.Unlike other methods, the results show that the multispectral method, in spite of its selectivity, provides realistic results, and does not under- or over-estimate the number of fires that can be sensed by the satellite. Consequently, this methodology is more appropriate than the simplest ones for a systematic sensing of this phenomenon.     

哀牢山—金沙江富碱侵入岩及其与裂谷构造关系初步研究

沿哀牢山—金沙江分布的富碱侵入岩,年龄为50-30Ma,化学成分是高钾(K_2O=5.07-8.30％)富碱(K_2O+Na_2O=8.17-10.08％),LREE富集(∑Ce/∑Y=7.5-9.4),铕一般无异常(δEu=0.98-1.06),δS~(34)值小(1.11-3.27)和锶初始比低(i=0.706)等,以及成因演化受第三纪裂谷控制。