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30 September 1994, Volume 6 Issue 3 Previous Issue    Next Issue
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GEOCHEMICAL CHARACTERISTICS AND MEDIUM PRESSURE GRANULITE FACIES METAMOPHISM OF MAFIC GRANULITE ROCKS FROM THE LARSEMANN HILLS,EAST ANTARCTICA 1994, 6 (3):  4-14.  Abstract ( 1406 )   PDF (547KB) ( 1161 )   Oriented distributed mafic granulite lenses,pods and boudins occur in metapelitic and leucogneiss in the Larsemann Hills,Prydz Bay,East Antarctica. The geochemical characteristic of the rocks imply that they are chemically similar to mafic cumulate.They probably represent remnants of mafic dykes. In the Mirror peninsula orthopyroxene plagioclase symplectites aroud garnet in mafic granulite is discovered ,orthopyroxene and plagioclase form by the reaction garnet+quartz→plagioclase+orthopyroxene Average pressure calculation on the assemblage indicates the prevailing conditions were 6.3±0.5kbar at 747±48°C.It is the first pressure estimate in the light of the equilibrium assemblage garnet orthopyroxene plagioclase quartz.An earlier medium pressure granulite facies event in the Larsemann Hills is confirmed. Related Articles | Metrics

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CRUST MANTLE STRUCTURE UNDER SOUTH POLE AND ROSS SEA BEACH IN ANTARCTICA 1994, 6 (3):  15-22.  Abstract ( 1200 )   PDF (454KB) ( 1231 )   In this paper, based on waveform comparision of theoretical seismgrams with four teleseismograms recorded by SBA(New Zealand) and SPA(U.S.A) of WWSSN.It shows that the crustal thickness beneath South Pole is about 45km, double layered structure.That crustal thickness below Ross Sea Beach is single structure, about 24km.At the depth of 350-450km it presents low velocity layer. The above results indicated different tectonic characteristics in both sides of Antarctic Transantarctic Mountain. Related Articles | Metrics

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CRYSTAL FABRICS OF FIRN/ICE CORES FROM SHALLOW BOREHOLES ON NELSON ICE CAP,ANTARCTICA 1994, 6 (3):  23-27.  Abstract ( 1262 )   PDF (153KB) ( 898 )   The crystal fabric measurement of three shallow firn/ice cores from Nelson Ice Cap shows that c axes orientation is preferred at the surface.Within 20m depth,the double fan pattern fabric is dominant.Between 20 and 30m depth,the fabric pattern has a tendency to change to the single maximum pattern.These are very different from that reported from mountain temperate glaciers in the lower latitudes.The intense meltwater percolation and refreezing may have an important effect,but the mechanism needs to be studied further in detail. Related Articles | Metrics

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A PRELIMINARY AGE DETERMINATION WITH NUMERICAL MODELLING FOR AN ICE CORE EXTRACTED FROM LOW DOME OF COLLINS ICE CAP,KING GEORGE ISLAND,ANTARCTICA 1994, 6 (3):  28-35.  Abstract ( 1332 )   PDF (224KB) ( 1133 )   After coring,ice sampling strategies and preliminary interpretations require a preliminary understanding of age depth profiles of the core,which means the well established time scales are necessariated. According to ice flow state,temperature distribution,mass balance and dynamic characteristics of Low Dome on Collins Ice Cap,revealed by observational data collected in situ for more than one year,Dansgaard Johnsen model and isothermal ice flow models for n=3 are adopted respectively to calculate the time scales of a 80. 2m ice core.Our calculation show a very approximate time scale of the core,at depth of 10m above the bedrock,ice dating of 1879 a and 1854 a B.P.are obtained by these two models respectively.The maximum error between two model calculation is no more than 2% at each depth of the ice cap.Comparisons with the chronical records of the volcanic ash layers contained in the middle upper part of the core suggest an age error less than 3%. Related Articles | Metrics

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ANALYSIS OF THE IONOSPHERIC ANOMALY OVER GREAT WALL STATION,ANTARCTICA 1994, 6 (3):  36-40.  Abstract ( 1250 )   PDF (254KB) ( 1118 )   In this paper,we use an empirical method to derive the height of maximum electron concentration of the F 2 region and neutral meridional winds over Great Wall Station,Antarctic.Using the HWM 90 Model,the predictions of the meridional winds over Great Wall Station are also calculated. The results can explain two anomaly features of ionosonde data of GreatWall Station. In summer,peak values of f 0F 2 appear during night time. In winter,especially during June and July,f 0F 2 decrease dramatically compare to summer's data.Summer anomaly can be explained by combining effects of two competing cause,thermospheric winds and solar effects on ionosphere. The location of high geographic latitude and middle geomagnetic latitude of Great Wall Station is an important factor in this study. Related Articles | Metrics

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STUDY ON THE OSCILLATION RELATIONSHIP BETWEEN SEA ICE OF THE ARCTIC AND ANTARCTIC 1994, 6 (3):  41-55.  Abstract ( 1237 )   PDF (672KB) ( 1291 )   In this paper,the Antarctic sea ice is divided into four regions:SPI1,the eastern Antarctic region;SPI2,centered at the Ross Sea;SPI3,centered at the Weddell Sea;SPI4,the whole Antarctic sea region.The Arctic Sea ice is divided into three regions:NPI1 on the Pacific-side;NPI2 on the Atlantic-side;NPI3,the whole Arctic sea region.In this paper,by the mathematical statistical methods,the SIGRID polar sea ice data provided by WDC-A are used to analyze the interrelations between sea ice among the Arctic and Antarctic regions. It is found that ,very complicated interactions exist between sea ice of the Arctic and Antarctic Regions with the most outstanding characteristics as follows: The vibration source of the interactions between two Poles' sea ice is NPI2.SPI3 is the positive feedback center affecting the Antarctic sea ice.SPI2 is the negative feedback center affecting on two Poles' sea ice. The strongest interactions among NPI2,SPI3 and SPI2 make a quasi-periodic intensity variation between sea ice of the Antarctic and Arctic with their cycle period of 5￣6 years. This cycle period is just coincident with the principal period of NPI2 and SPI3 variations themselves. An oscillation relationship forms among NPI2,SPI3 and SPI2. The oscillation between SPI3 and SPI2 is of zonal nature while the oscillation between NPI2 and SPI3 or SPI2 is of meridional nature. This kind of oscillation is not at the same time but with a longer lag time difference.NPI2 is about 0.5￣1 year lag to SPI2;SPI3 is 2￣12 months and 24￣48 months lag to SPI2;and SPI3 is 0.5￣2 years lag to NPI2. Related Articles | Metrics

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DESCRIPTION OF THREE ENDOCOMMENSAL CILIATES FROM SEA URCHINS IN THE WEDDELL SEA,ANTARCTICA (PROTOZOA,CILIOPHORA) 1994, 6 (3):  56-64.  Abstract ( 1264 )   PDF (546KB) ( 1442 )   Morphology and infraciliature of 3 endocommensal ciliates,Strombidium echini Song et al.,in press,Parauronemoides echini Song et al.,in press,Paracryptochilidium antarcticum Song et al.,in press,from the digestion tract of sea urchins in Antarctica (Weddell Sea) had been investigated during April,1992 and morphologically studied. The Parauronemoides echini is characterized by the bilateral flattened body shape,absence of the naked apical plate,shortened somatic kineties direct to the ventral surface and the twisted narrow buccal field.Paracryptochilidium antarcticum would be distinguished with the D formed bodyshape,buccal apparatus which is located to the posterior 1/4 of cell length ,the pedal like "branched " macronucleus and the absence of the caudal projection.Different from many other congeners,the dorso ventrally flattened Strombidium echini is of,very particularly ,one girdle and two postequatorial kineties. Related Articles | Metrics

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OBSERVATIONS ON ECOLOGICAL ENVIRONMENTAL CONDITION OF THE GREAT WALL BAY,KING GEORGE ISLAND, ANTARCTICA,FROM NOVEMBER 1988 TO MARCH 1989 1994, 6 (3):  65-76.  Abstract ( 1327 )   PDF (317KB) ( 1259 )   Physical and chemical factors, chlorophyll a in water column were measured in the Great Wall Bay, King George Island,Antarctica during austral summer in 1988-1989.Routine samples of water were taken at five sites with water depth ranges from 14 to over 100m. Water temperature and pH ranged from -1.6 to 2.2°C and from 8.0 to 9.1 respectively. Transparency of sea water ranged from 4m to 13m. Concentrations of phosphate, nitrate and nitrite ranged from 0.738 to 4.873μg P/L,6.181 to 25.945μg N/L and 0.017 to 0.273 μg N/L respectively. Chlorophyll a concentration in water column ranged from 0.21 to 2.67 mg/m 3.The maximum of chlorophyll a(2.67 mg/m 3) was observed at surface water on 26 November 1988 at site 5. In comparison with the water, chlorophyll-a concentration in the fast ice was higher,which ranged from 2.55 to 56.84 mg/m 3 and most of them were concentrated in the interior layer of sea ice rather than in the bottom layer which often observed in other sea ice such as Davis, Syowa, Casey and McMurdo Sound etc. Related Articles | Metrics