Long-term evolution of the global carbon cycle: historic minimum of global surface temperature at present     

SIEGFRIED FRANCK  KONRAD J. KOSSACKI  WERNER VON BLOH  CHRISTINE BOUNAMA 《Tellus. Series B, Chemical and physical meteorology》2002,54(4):325-343

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Dust mobilization and transport in the northern Sahara during SAMUM 2006 – a meteorological overview     

By PETER KNIPPERTZ  ALBERT ANSMANN  DIETRICH ALTHAUSEN  DETLEF MÜLLER  MATTHIAS TESCHE  EIKE BIERWIRTH  TILMAN DINTER  THOMAS MÜLLER  WOLFGANG VON HOYNINGEN-HUENE  KERSTIN SCHEPANSKI  MANFRED WENDISCH  BERND HEINOLD  KONRAD KANDLER  REAS PETZOLD  LOTHAR SCHÜTZ  INA TEGEN 《Tellus. Series B, Chemical and physical meteorology》2009,61(1):12-31

The SAMUM field campaign in southern Morocco in May/June 2006 provides valuable data to study the emission, and the horizontal and vertical transports of mineral dust in the Northern Sahara. Radiosonde and lidar observations show differential advection of air masses with different characteristics during stable nighttime conditions and up to 5-km deep vertical mixing in the strongly convective boundary layer during the day. Lagrangian and synoptic analyses of selected dust periods point to a topographic channel from western Tunisia to central Algeria as a dust source region. Significant emission events are related to cold surges from the Mediterranean in association with eastward passing upper-level waves and lee cyclogeneses south of the Atlas Mountains. Other relevant events are local emissions under a distinct cut-off low over northwestern Africa and gust fronts associated with dry thunderstorms over the Malian and Algerian Sahara. The latter are badly represented in analyses from the European Centre for Medium–Range Weather Forecasts and in a regional dust model, most likely due to problems with moist convective dynamics and a lack of observations in this region. This aspect needs further study. The meteorological source identification is consistent with estimates of optical and mineralogical properties of dust samples.  相似文献   

Three-dimensional architecture and development of Danian bryozoan mounds at Limhamn, south-west Sweden, using ground-penetrating radar     

LARS NIELSEN  ADAM SCHACK VON BROCKDORFF  MORTEN BJERAGER  FINN SURLYK 《Sedimentology》2009,56(3):695-708

Bryozoan mounds from the middle Danian (Lower Palaeocene) of the Danish Basin represent a possibly new class of non‐cemented skeletal mounds. The sedimentology and palaeoecology of the mounds have recently been studied in detail. Three‐dimensional images of middle Danian bryozoan mound structures in the Limhamn limestone quarry, south‐west Sweden, obtained from combined reflected ground‐penetrating radar signals and outcrop analysis provide new information about the architecture and growth development of such mounds. The mounds are composed of bryozoan limestone and dark‐grey to black flint bands which outline mound geometries. Ground‐penetrating radar data sections are collected over a 120 m by 60 m grid of data lines with trace spacing of 0·25 m, providing a depth penetration of 7 to 12 m and a vertical resolution of ca 0·30 m. The ground‐penetrating radar images outline the geometry of the internal layering of the mounds which, typically, have widths and lengths of 30 to 60 m and heights of 5 to 10 m. Mound architecture and growth show great variability in the ground‐penetrating radar images. Small‐scale mound structures with a palaeorelief of only a few metres may constitute the basis for growth of larger mounds. The outermost beds of the individual mounds are commonly characterized by sub‐parallel to parallel reflections which have a circular to slightly oval appearance in map view. The mounds are mainly aggrading and do not show clear signs of pronounced lateral migration during growth, although some mound structures indicate a preferential growth direction towards the south. Growth patterns interpreted from the ground‐penetrating radar images suggest that the palaeocurrents in the study area may have shown great variability, even on a small scale. This observation is in contrast to results from studies of extensive, slightly older early Danian mound complexes exposed in coastal cliffs at Stevns Klint and Karlby Klint located 50 and 200 km away from the study area, respectively. At these locations the mounds show a remarkably uniform development and typically are asymmetrical, clearly showing migration directions towards the south. These differences in mound geometry may be the result of differences in the current systems and water depths that existed during formation of the early and middle Danian mounds, respectively. The mounds at Limhamn were located closer to the basin margin in shallower water than those at Stevns Klint and Karlby Klint. In addition, the difference in mound architecture may be due to the occurrence of non‐layered, irregular coral mounds intercalated with the bryozoan mounds at Limhamn.  相似文献   

Interdecadal variability in a global coupled model     

JIN-SONG VON STORCH 《地球，A辑:动力气象学与海洋学》1994,46(4):419-432

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Petrological and Chemical Evolution of the Northeastern Troodos Extrusive Series, Cyprus     

BEDNARZ  ULRICH; SCHMINCKE  HANS-ULRICH 《Journal of Petrology》1994,35(2):489-523

Four magma series are distinguished in the northeastern TroodosExtrusive Series: (A) a Lower Low-Ti Series (Lo-LTS) of basalticandesites, (B) a High-Ti Series (HTS) of basaltic andesitesto rhyodacites, (C) a Low-Ti Series(DLTS), the last two beingof basaltic andesite. Trace-element characteristics vary systematicallyfrom Series A to D and are interpreted in terms of a variablecontribution of three major source components (SCs). LILE-enrichedwater-rich fluids (SCI) derived from dehydration of a subductedlithosphere slab were continuously added to the overlying mantlewedge. Increasing LILE/HFSE and LILE/REE ratios and decreasingabsolute HFSE and REE concentrations from Series A to Dindicateprogressive depletion of the actual mantle source (SCII). Anegative Ta anomaly in the lavas decreases from Series A toD and is interpreted to have resulted from partial melting ofthe lower crust (SCII) where Ta-Nb-Ti may be fractionated byTi-rich accessory phases. The contribution of SCIII decreaseswhen the eruptive sites successively move away from the centralaxial zone and the temperature of the lower crust decreases,preventing partial melting of the lower crust. Chemical compositionsof fresh glass separates and phenocrysts indicate a change ofmajor petrogenetic processes from series A to D. Lo-LTS andIITS lavas are intrepreted to be directly related by open-systemfractional crystallization in crustal magma chambers. Removalof observed phenocryst phases clinopyroxene, orthopyroxene,plagioclase, and magnetite, and repeated subsequent mixing ofdacitc to rhyodacitic magmas with batches of replenshing basalticandesites are the major processes, possibly induced by vesicleformation in the mafic layer after a period of some crystallization.LTS and DLTS magmas were directly fed to the surface withoutstagnating at crustal levels, with feeder dykes positioned marginalto the central rift zone and thus by-passing the central magmachambers. These magmas apparently experienced only limited fractionalcrystallization of 10–15 wt.% olivine+clinopyroxene+chromite,probably at the mantle-crust boundary.  相似文献   

INTEGRATED EXPLORATION FOR LOW-TEMPERATURE GEOTHERMAL RESOURCES IN THE HONEY LAKE BASIN,CALIFORNIA1     

ULRICH SCHIMSCHAL 《Geophysical Prospecting》1991,39(2):279-291

An integrated exploration study is presented to locate low-temperature geothermal reservoirs in the Honey Lake area of northern California. Regional studies to locate the geothermal resources included gravity, infra-red, water-temperature, and water-quality analyses. Five anomalies were mapped from resistivity surveys. Additional study of three anomalies by temperature-gradient and seismic methods was undertaken to define structure and potential of the geothermal resource. The gravity data show a graben structure in the area. Seismic reflection data indicate faults associated with surface-resistivity and temperature-gradient data. The data support the interpretation that the shallow reservoirs are replenished along the fault zones by deeply circulating heated meteoric waters.  相似文献   

Modern carbonate and terrigenous clastic sediments on a cool water, high energy, mid-latitude shelf: Lacepede, southern Australia   总被引：1，自引：0，他引：1  

NOEL P. JAMES  YVONNE BONE†  CHRISTOPHER C. VON DER  BORCH‡ VICTOR A. GOSTIN† 《Sedimentology》1992,39(5):877-903

The wide Lacepede Shelf and narrow Bonney Shelf are contiguous parts of the south-eastern passive continental margin of Australia. The shelves are open, generally deeper than 40 m, covered by waters cooler than 18°C and swept by oceanic swells that move sediments to depths of 140 m. The Lacepede Shelf is proximal to the ‘delta’of the River Murray and the Coorong Lagoon. Shelf and upper slope sediments are a variable mixture of Holocene and late Pleistocene quartzose terrigenous clastic and bryozoa-dominated carbonate particles. Bryozoa grow in abundance to depths of 250 m and are conspicuous to depths of 350 m. They can be grouped into four depth-related assemblages. Coralline algae, the only calcareous phototrophs, are important sediment producers to depths of 70 m. Active benthic carbonate sediment production occurs to depths of 350 m, but carbonate sediment accumulation is reduced on the open shelf by continuous high energy conditions. The shelf is separated into five zones. The strandline is typified by accretionary sequences of steep shoreface, beach and dune carbonate/siliciclastic sediments. Similar shoreline facies of relict bivalve/limestone cobble ridges are stranded on the open shelf. The shallow shelf, c.40–70 m deep, is a wide, extremely flat plain with only subtle local relief. It is a mosaic of grainy, quartzose, palimpsest facies which reflect the complex interaction of modern bioclastic sediment production (dominated by bryozoa and molluscs), numerous highstands of sea level over the last 80 000 years, modern mixing of sediments from relatively recent highstands and local introduction of quartz-rich sediments during lowstands. The middle shelf, c.70–140 m deep, is a gentle incline with subtle relief where Holocene carbonates veneer seaward-dipping bedrock clinoforms and local lowstand beach complexes. Carbonates are mostly modern, uniform, clean, coarse grained sands dominated by a diverse suite of robust to delicate bryozoa particles produced primarily in situ but swept into subaqueous dunes. The deep shelf edge, c. 140–250 m deep, is a site of diverse and active bryozoa growth. Resulting accumulations are characteristically muddy and distinguished by large numbers of delicate, branching bryozoa. The upper slope, between 250 and 350 m depth, contains the deepest platform-related sediments, which are very muddy and contain a low diversity suite of delicate, branching cyclostome bryozoa. This study provides fundamental environmental information critical for the interpretation of Cenozoic cool water carbonates and the region is a good model for older mixed carbonate-terrigenous clastic successions which were deposited on unrimmed shelves.  相似文献   

Environmental setting and microstructure of subfossil lithified stromatolites associated with evaporites, Marion Lake, South Australia   总被引：2，自引：0，他引：2  

C. C. VON DER  BORCH  B. BOLTON  J. K. WARREN 《Sedimentology》1977,24(5):693-708

A variety of finely laminated, subfossil, aragonitic stromatolites and oncolites occur on a regressive marginal flat surrounding Marion Lake, South Australia. These algal forms overlie a substrate of coarse, highly porous, moldic aragonitic limestone which passes progressively towards the take centre through a zone of interstatified aragonite and gypsum and ultimately to pure crystalline gypsum. All of these facies overlie Holocene marine carbonate bank sediments which unconformably overlie at least one upper Pleistocene marine unit. Detailed petrographic and stratigraphic studies, combined with comparative studies of related nearby lakes containing a variety of living aragonitic cryptalgalaminates, provide a model for development of the Holocene sedimentary sequence. Marion Lake last became inundated by the sea around 6500 years ago during the Holocene transgression, when a protected marine environment was initiated. Lateral sediment accretion sealed marine passes into the resulting lagoon system soon after sealvel stabilized, and a variety of gypsum and gypsum-carbonate-algal facies evolved. Pure gypsum was deposited in waters 2–3 m deep in the central basin area concurrently with formation of seasonally alternating gypsum and aragonite layers towards basin margins. Blue-green filamentous algae thrived in the shallower marginal areas and at least partly controlled carbonate deposition, which must have occurred during seasonal outflow of carbonate-rich ground water from the calcareous dune aquifer over denser gypsum-saturated waters. These systems eventually migrated towards the centre of the lake to produce the relationships preserved today. The fresher waters also leached the gypsum from the marginal gypsum-carbonate facies. Collapse due to gypsum dissolution, along with aragonite crystallization, combined to form a lake-marginal mega-polygonal facies. Teepee structures formed around polygon margins, with optimum conditions for stromatolite development occurring on the teepee crests. The actual stromatolites which occur around Marion Lake are strongly indurated and involve a variety of morphologies, the most common of which are laterally linked hemispheroids. Stacked hemispheroids and oncolites are also relatively common, along with irregular forms, many of which encrust a variety of substrate irregularities. Vertical relief of the stromatolites varies from centimetres to tens of centimetres and all forms are characterized by extremely fine internal interlaminations of alternate light and dark grey laminae which typically occur several per millimetre. The microstructure comprises micritic aragonite crystals with fibrous habit associated with organic matter, and occasional zones of abundant algal filament molds which are generally oriented normal to the laminae.  相似文献   

DIE STRATIGRAPHISCHE UND PALAEONTOLOGISCHE BEDEUTUNG DER FOSSILEN NAGETIERE CHINAS     

VON C.C.YOUNG 《地质学报》1931,(1)

Ⅰ. VORBEMERKUNG. Die Ordnung Nagetiere umfasst sehr viele Arten und ist die verbreitetste Tiergruppe innerhalb der Saeugetiere. Sie macht mit ihren etwa 2800 Species mehr als ein Drittel der heutigen Landsaeugetiere aus. Die Nagetiere sind auf der ganzen Welt bis zu den Polen und dem vereisten Hochgebirge an-  相似文献   

Statistical downscaling of monthly mean North Atlantic air-pressure to sea level anomalies in the Baltic Sea   总被引：1，自引：0，他引：1  

HAUKE HEYEN  EDUARDO ZORITA  HANS VON STORCH 《地球，A辑:动力气象学与海洋学》1996,48(2):312-323

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