observations on the role of the bernice coal field sullivan county pennsylvania anthracites in the development of coalification theories in the appalachians abstract the bernice coal field sullivan county pennsylvania contains anthracite rank coal in relatively unfolded strata that setting along with a misinterpretation of the significance of apparent rank anomalies led to examples from the bernice coal field being used in the development of coalification theories in the late 1800 s and early 1900 s the evidence available was used to justify both theories of thrust pressure coalification and rank variation due to original differences in the peat or peat accumulation processes as opposed to thermal metamorphism

on the antarctic peninsula batholith the plutonic rocks of the antarctic peninsula magmatic arc form one of the major batholiths of the circum pacific rim the antarctic peninsula batholith is a 1350 km long by 210 km wide structure which was emplaced over the period 240 to 10 ma with a cretaceous peak of activity that started at 142 ma and waned during the late cretaceous early jurassic and late jurassic early cretaceous gaps in intrusive activity probably correspond to episodes of arc compression in a northern zone of the antarctic peninsula the batholith intrudes palaeozoic mesozoic low grade meta sedimentary rocks and in a central zone it intrudes schists and ortho and paragneisses which have late proterozoic nd model ages and were deformed during triassic to early jurassic compression in a southern zone the oldest exposed rocks are permian sedimentary rocks and deformed jurassic volcanic and sedimentary rocks all these pre batholith rocks formed a belt of relatively immature crust along the gondwana margin with few exceptions jurassic plutons crop out only within the central zone many are peraluminous having s like mineralogies and relatively high 87sr 86sri they are considered to consist largely of partial melts of upper crust schists and gneisses and components of mafic magmas that caused the partial fusion by contrast early cretaceous plutons crop out along the length of the batholith few magma compositions appear to have been affected by upper crust the bulk being compositionally independent of the type of country rock they intrude they are dominated by metaluminous calcic si oversaturated 1 type granitoid rocks with relatively low 87sr 86sri intermediate silicic compositions 5 mgo we interpret these to represent partial melts of basic to intermediate igneous locally garnet bearing lower crust contemporaneous mafic magmas e g syn plutonic dykes form a more alkaline si saturated series having higher 143nd 144nd at the same87sr 86sr than the intermediate silicic series to which they are not petrogenetically related the change from limited partial fusion of upper crust in jurassic times to widespread partial fusion of lower crust in early cretaceous times is considered to be a result of an increasing volume of basaltic intrusion into the crust with time

biaxial vitrinite reflectance in coals of the elk valley coalfield southeastern british columbia canada ninety nine grab coal samples collected from ten different diamond drill cores from the jurassic cretaceous mist mountain formation in the elk valley coalfield in southeastern british columbia were analyzed petrographically for mean maximum vitrinite reflectance rmax mean random vitrinite reflectance rm and the lengths of the maximum intermediate and minimum axes of the reflectance indicating surface or ris of vitrinite rmaxrint andrmin coal rank in the coalfield ranges from high volatile a to low volatile bituminous values of rmax in the core samples range from 0 95 to 1 50 rmax rm rmax rint and rmin are all strongly intercorrelated r 0 89 in all combinations the vitrinite in all samples is biaxial in most cases biaxial negative as a consequence rmax is always less than rmax the relationship being rmax 1 044 rmax there is no relationship between degree of vitrinite reflectance anisotropy as represented by the ris shape and rank the results indicate that a secondary stress field not perpendicular to bedding existed during coalification

multiscale organisation of organic matter associated with gold and uranium minerals in the witwatersrand basin south africa abstract organic matter from the northern part of the early proterozoic witwatersrand basin carbon leader reef was investigated using optical om and transmission electron tem microscopes completed by xrd analysis the multiscale organization texture microtexture structure of the organic matter was observed in order to gain information about the processes which affected organic material after its deposition in sediments in the micrometre scale optical microscope the shape and size of the reflectance indicating surface ris of the organic matter were determined the organic matter reveals a prevailing biaxial symmetry the size of ris is generally dependent on uranium and increases with increasing uranium concentration furthermore it appears that more than one ris is present within the scale of a single sample each with a different symmetry and size the presence of domains differing in organisation of the aromatic framework was confirmed by tem observation in the df mode the aromatic skeleton of organic matter is composed of short often crumpled mostly isolated non stacked polyaromatic layers whose fringe length corresponds to 3 16 aromatic rings the data indicate reorganization of the polyaromatic organic matter structure under stress in high pressure and relatively low temperature conditions the organic matter was in a solid state within the rocks before the pressure event

textural transformation of thermally treated anthracites abstract the organic matter of anthracites consists of turbostratic two dimensional crystalline order stacks of three to five aromatic layers called the basic structural units bsu the arrangement of bsu forms the texture of anthracites which corresponds to their chemical and physical properties including optical properties reflectance values thermal treatment leads to the changes in the arrangement of bsu the character of structural and textural transformation of anthracites during heating can be determined based on the changes of reflectance values of anthracites several anthracites of various ranks were thermally treated over the temperature range of 400 673 k 1000 c 1273 k in an inert atmosphere n2 at atmospheric pressure the reflectance indicating surfaces ris were reconstructed and reflectance indicatrix parameters were calculated according to the kilby method specially modified for the study of anthracites it was found that the relative increase of reflectance values rmax rmin was greater for the lower metamorphosed samples than for the higher ones however the higher rank of initial samples the greater their final reflectance values and the anisotropy of the texture attained at 1000 c it indicates that the texture of the higher metamorphosed anthracites meta anthracites is more flexible for rearrangement during heating than the texture of the lower metamorphosed anthracites moreover the difference in the changes of reflectance values versus temperature for the higher and for the lower rank anthracites suggests that meta anthracites have undergone stronger natural metamorphism equivalent to about 200 c in comparison with the other anthracites it could be said that the character of textural transformations of individual anthracites results from the degree of their metamorphism and in a consequence from the texture of parent sediments

problems and possible solutions concerning radiocarbon dating of surface marine sediments ross sea antarctica abstract radiocarbon accelerator mass spectrometric ams dates on the acid insoluble fraction from 38 core tops from the western ross sea antarctica are used to address these questions 1 what are the apparent ages of sediments at or close to the present sediment water interface 2 is there a statistically significant pattern to the spatial distribution of core top ages and 3 is there a correction factor that can be applied to these age determinations to obtain the best possible holocene downcore chronologies ages of core top sediments range from 2000 to 21 000 14c yr b p some old core top dates are from piston cores and probably represent the loss of sediment during the coring process but some core top samples 6000 14c yr b p may represent little or no holocene deposition four possible sources of variability in dates 6000 14c yr b p n 28 are associated with 1 different sample preparation methods 2 different sediment recovery systems 3 different geographic regions and 4 within sample lateral age variability statistical analysis on an a posteriori design indicates that geographic area is the major cause of variability there is a difference in mean surface sediment age of nearly 2000 yr between sites in the western ross sea and sites east of ross bank in south central ross sea the systematic variability in surface age between areas may be attributed to a variable sediment accumulation rates sar surface age is inversely related to sar b differences in the percentage of reworked dead carbon between each area and or c differences in the co2 exchange between the ocean and the atmosphere

correlation between optical chemical and micro structural parameters of high rank coals and graphite abstract in order to identify the parameters that best characterize the chemical and structural evolution of organic matter during coalification the relationships between optical chemical and micro structural parameters in high rank coals and natural graphite were studied the samples include anthracites from penarroya belmez espiel basin spain douro basin portugal and alto chicama basin peru and natural graphite from canada mozambique and austria correlations between the following optical parameters were assessed vitrinite random reflectance rr reflectance indicating surfaces ris axis rmax rint and rmin and ris parameters ram rev and rst as well as bw and ai anisotropy parameters furthermore the chemical parameters used were chosen according to their significant variation in coals namely volatile matter carbon and hydrogen contents calculated in dry ash free basis vmdaf cdaf hdaf as well as the h c atomic ratio structural organization was characterized by micro raman spectroscopy and xrd raman parameters used were the full width at half maximum fwhm and position of g and d1 bands on the first order raman spectrum and the id1 ig intensity area ratio the selected xrd parameters were interlayer spacing d002 and crystallite sizes la and lc results show that i rmax ris axis seems to correlate best with chemical and micro structural parameters ii for the majority of studied samples hdaf and h c atomic ratio are the only chemical parameters with significant correlations with rmax iii the fwhm of the g band of raman spectrum shows good linear correlation with the xrd parameter d002 and iv structural organization of carbon materials as measured by trends in their optical and crystalline parameters is influenced by their hydrogen content daf basis and therefore by the h c atomic ratio

application of tandem accelerator mass spectrometer dating to late pleistocene holocene sediments of the east antarctic continental shelf abstract glacial recession from the antarctic continental shelf is recorded by glacial marine diamictons sands and overlying siliceous oozes in order to clarify the chronology for this sequence use was made of the university of arizona tandem accelerator mass spectrometer tams for 14 c dating small samples of benthic and planktonic foraminifera were selectively removed from diamictons graded sands and surface sediments which were recovered from the wilkes land continental shelf and slope east antarctica organic carbon was also utilized as a source for tams dating of the siliceous oozes and muds uncorrected ages varied from 14 260 140 to 3230 200 yr b p carbon fixed by phytoplankton and foraminifera is strongly influenced by old glacial derived co 2 thus reservoir corrections of up to 5500 yr are needed for the 14 c dates iceberg turbation reworks foraminifera so that dates from resulting deposits diamictons are interpreted as maximum ages the consistency of corrected ages from the shelf along with the sedimentologic interpretation suggests a rather recent recession perhaps mid holocene for this portion of the east antarctic ice sheet further application of the tams method should help clarify other problems concerning the late quaternary glacial history of antarctica

holocene glacier fluctuations a global overview of glacier advances and retreats grouped by regions and by millennia for the holocene is compiled from previous studies the reconstructions of glacier fluctuations are based on 1 mapping and dating moraines defined by 14 c tcn osl lichenometry and tree rings discontinuous records time series and 2 sediments from proglacial lakes and speleothems continuous records time series using 189 continuous and discontinuous time series the long term trends and centennial fluctuations of glaciers were compared to trends in the recession of northern and mountain tree lines and with orbital solar and volcanic studies to examine the likely forcing factors that drove the changes recorded a general trend of increasing glacier size from the earlyemid holocene to the late holocene in the extra tropical areas of the northern hemisphere nh is related to overall summer temperature forced by orbitally controlled insolation the glaciers in new zealand and in the tropical andes also appear to follow the orbital trend i e they were decreasing from the early holocene to the present in contrast glacier fluctuations in some monsoonal areas of asia and southern south america generally did not follow the orbital trends but fluctuated at a higher frequency possibly triggered by distinct teleconnections patterns during the neoglacial advances clustered at 4 4e4 2 ka 3 8e3 4 ka 3 3e2 8 ka 2 6 ka 2 3e2 1 ka 1 5e1 4 ka 1 2e1 0 ka 0 7e0 5 ka corresponding to general cooling periods in the north atlantic some of these episodes coincide with multidecadal periods of low solar activity but it is unclear what mechanism might link small changes in irradiance to widespread glacier fluctuations explosive volcanism may have played a role in some periods of glacier advances such as around 1 7e1 6 ka coinciding with the taupo volcanic eruption at 232 5 ce but the record of explosive volcanism is poorly known through the holocene the compilation of ages suggests that there is no single mechanism driving glacier fluctuations on a global scale multidecadal variations of solar and volcanic activity supported by positive feedbacks in the climate system may have played a critical role in holocene glaciation but further research on such linkages is needed the rate and the global character of glacier retreat in the 20th through early 21st centuries appears unusual in the context of holocene glaciation though the retreating glaciers in most parts of the northern hemisphere are still larger today than they were in the early and or mid holocene the current retreat

the occurrence of anthracites in an area characterized by lower rank coals in the upper silesian coal basin of poland abstract the results of petrographical geological and chemical examinations on anthracites semianthracites and medium low volatile bituminous coals from jastrzebie in the upper silesian coal basin of poland are presented the coking coals mined in this region exhibit volatile matter v daf 18 26 free swelling index fsi 3 8 and reflectance r m 1 10 1 35 and are inertiniterich coals i 25 63 coal seam 504 of the anticlinal beds namurian b has been affected by thermal metamorphism and contains both coking coals and coals of higher rank according to the criterion of polish standards this coal seam varies from anthracite v daf daf 10 14 in rank the carbon content is slightly lower and the hydrogen content a little higher than those of typical anthracites and semianthracites the reflectance values r m 1 56 2 62 are generally lower than the r m values proposed by the international committee for coal petrology as boundary values for anthracites and bituminous coal the magnitude of anisotropy and microhardness were also examined examinations of optical properties prove that the metamorphism exhibited by the coals is the result of elevated temperature and variable pressure the analyses of the maceral composition indicate that there is a decrease in the inertinite content in anthracites vitrinite exhibits the features of thermally altered coal the micrinite content shows a little variation in coking coals a strongly fluorescing bituminous substance with the optical features of exsudatinite was found the constructed geological section of coal seam 504 shows distinct regular changes in chemical and physical properties as well as the petrographic composition which may be caused by the heat flux of a magma intrusion not localized so far

raman spectra of carbonaceous material in metasediments a new geothermometer metasedimentary rocks generally contain carbonaceous material cm deriving from the evolution of organic matter originally present in the host sedimentary rock during metamorphic processes this organic matter is progressively transformed into graphite s s and the degree of organisation of cm is known as a reliable indicator of metamorphic grade in this study the degree of organisation of cm was systematically characterised by raman microspectroscopy across several mesozoic and cenozoic reference metamorphic belts this degree of organisation including within sample heterogeneity was quantified by the relative area of the defect band r2 ratio the results from the schistes lustres western alps and sanbagawa japan cross sections show that 1 even through simple visual inspection changes in the cm raman spectrum appear sensitive to variations of metamorphic grade 2 there is an excellent agreement between the r2 values calculated for the two sections when considering samples with an equivalent metamorphic grade and 3 the evolution of the r2 ratio with metamorphic grade is controlled by temperature t along the tinos cross section greece which is characterised by a strong gradient of greenschist facies overprint on eclogite facies rocks the r2 ratio is nearly constant consequently the degree of organisation of cm is not affected by the retrogression and records peak metamorphic conditions more generally analysis of 54 samples representative of high temperature low pressure to high pressure low temperature metamorphic gradients shows that there is a linear correlation between the r2 ratio and the peak temperature t c 445 r2 641 whatever the metamorphic gradient and probably the organic precursor the raman spectrum of cm can therefore be used as a geothermometer of the maximum temperature conditions reached during regional metamorphism temperature can be estimated to 50 c in the range 330 650 c a few technical indications are given for optimal application

ice stream retreat and ice shelf history in marguerite trough antarctic peninsula sedimentological and foraminiferal signatures the timing nature and causes of grounded ice sheet retreat following the last glacial maximum lgm in marguerite trough west antarctic peninsula and subsequent early holocene ice shelf decay are presented in this paper we use sedimentological foraminiferal geotechnical and accelerator mass spectrometer ams radiocarbon data from marine cores from the mid continental shelf together with previously published ams dates to establish a sedimentological and chronological model initial ice sheet retreat through the outer and mid shelf sectors of marguerite trough was under way by ca 14 ka b p was rapid and coincided with the sea level rise of meltwater pulse 1a an ice shelf formed during this retreat and fine grained laminated muds reflecting meltwater derived suspension settling and or tidal pumping were deposited during this time the ice sheet remained grounded on the inner shelf ice shelf breakup and retreat of the calving front from ca 13 2 to 12 5 ka b p was slow 100 m a 1 across the outer and mid shelf with calving bay conditions remaining for at least 3 5 ka we interpret this ice shelf decay to have been driven by an incursion of weddell sea transitional water onto the shelf in contrast grounding line and ice shelf retreat in the inner bay occurred from ca 9 3 ka b p and was driven by circumpolar warm deep water encroaching onto the continental shelf at this time the mid shelf was an open marine environment characterized by hemipelagic deposition these findings highlight the importance of oceanographic controls in the breakup of antarctic peninsula ice shelves during the holocene

first geomorphological record and glacial history of an inter ice stream ridge on the west antarctic continental shelf inter ice stream areas cover significant portions of antarctica s formerly glaciated shelves but have been largely neglected in past geological studies because of overprinting by iceberg scours here we present results of the first detailed survey of an inter ice stream ridge from the west antarctic continental shelf well preserved sub and proglacial bedforms on the seafloor of the ridge in the eastern amundsen sea embayment ase provide new insights into the flow dynamics of this sector of the west antarctic ice sheet wais during the last glacial cycle multibeam swath bathymetry and parasound acoustic sub bottom profiler data acquired across a mid shelf bank between the troughs of the pine island thwaites pitpis and cosgrove palaeo ice streams copis reveal large scale ribbed moraines hill hole pairs terminal moraines and crevasse squeeze ridges together these features form an assemblage of landforms that is entirely different from that in the adjacent ice stream troughs and appears to be unique in the context of previous studies of antarctic seafloor geomorphology from this assemblage the history of ice flow and retreat from the inter ice stream ridge is reconstructed the bedforms indicate that ice flow was significantly slower on the inter ice stream ridge than in the neighbouring troughs while terminal moraines record at least two re advances or stillstands of the ice sheet during deglaciation an extensive field of crevasse squeeze ridges indicates ice stagnation subsequent to re advancing ice which deposited the field of terminal moraines in the ne the presented data suggest that the ice flow behaviour on the inter ice stream ridge was substantially different from that in the adjacent troughs however newly obtained radiocarbon ages on two sediment cores recovered from the inter ice stream ridge suggest a similar timing in the deglaciation of both areas this information closes an important gap in the understanding of past wais behaviour in the eastern ase our newly documented bedforms will also serve as an important diagnostic tool in future studies for interpreting ice sheet histories in similar inter ice stream areas

vitrinite reflectance anisotropy as a tectonic fabric element the anisotropy of the coal maceral vitrinite was analyzed in relation to the tectonic setting of a coal from the southern anthracite field in pennsylvania for the coal studied the maximum intermediate reflectance plane essentially paralleled the axial plane of the synclinorium n66 e strike 64 se dip

lithological dependency and anisotropy of vitrinite reflectance in high rank sedimentary rocks of the ibbenburen area nw germany implications for the tectonic and thermal evolution of the lower saxony basin abstract covering a depth interval of 1200 m thirty one rock samples were collected from a well drilled in the beust field of the ibbenburen anthracite mine lower saxony basin nw germany these rock samples consist of high rank coals anthracites claystones siltstones and sandstones of pennsylvanian age analytical methods include the measurement of random vitrinite reflectance vr r rotational reflectance vr rot as well as maximum and minimum reflectances vr max and vr min enabling the evaluation of the lithological influence on vitrinite reflectance as well as the indication of tectonic stresses in the lower saxony basin by applying the ris reflectance indicating surface analysis method this study shows that not only due to the high rank of the studied samples and associated anisotropic character but also due to lithological dependency a partially significant scatter of measured vr r can be observed the scatter in coals is significantly less than in other sedimentary rocks e g standard deviation in coals can be up to 7 less than in siltstones the expected increase of standard deviation with increasing rank and accordant anisotropy was not observed for vr r but rather for vr max with the exception of coals displaying a relatively constant and low deviation throughout the depth maturity interval mean vr r values of coals differ from those of other sedimentary rocks at equal depths vr r measured in claystones is consistently higher compared to associated coal seams and can be elevated by up to 10 silt and sandstones always display lower vr r with differences of up to 16 at very high levels of thermal maturity vitrinite reflectance depends not only on maximum paleotemperature but also on lithology leading to differences in pressure propagation and thus deformation additionally radioactive trace elements in coals and organic matter rich claystones provide a local secondary heat source 40 k and 232 th are preferentially bound to clay particles which are enriched in the studied claystones and depleted in the silt and sandstones possibly leading to higher vitrinite reflectance observed in the claystones ris analysis shows a predominantly negative biaxial distribution indicating the absence of thermal overprinting by a possible intrusion bramsche massif during the late cretaceous which would have induced a uniaxial distribution instead this implies in addition to vertical stresses due to depositional loading the presence of a secondary stress field not perpendicular to bedding which is related to the inversion of the lower saxony basin this information presents in combination with previous basin modeling results additional evidence for deep subsidence with subsequent uplift being the cause for the present day maturity patterns observed in the lower saxony basin

climatically induced retreat and collapse of northern larsen ice shelf antarctic peninsula the areal changes of the northern larsen ite shelf lis antarctic peninsula between march 1986 and march 1997 have been analyzed based on synthetic aperture radar images of the european remote sensing satellites ers 1 and ers 2 and on landsat images this analysis is complemented by data on ice motion and surface mass balance which have been obtained during several field campaigns since the early 1980s after a period of retreat coinciding with atmospheric warming and with decreasing net accumulation at the surface due to melt losses the two northernmost sections of lis disintegrated almost completely within a few days in january 1995 recent observations of the ice shelf section north of jason peninsula which is presently the northernmost section of lis show increased summer melt and intensification of the rifting processes probably causing accelerated retreat of this section in the near future the retreat and the disintegration event of lis indicate high sensitivity of ice shelves to prolonged perturbations of the mass balance

late quaternary glacial history of george vi sound area west antarctica during the last glacial maximum in west antarctica separate ice caps developed on alexander island and on palmer land became confluent in george vi sound and discharged northward from latitude 72 s radiocarbon 32 000 yr and amino acid approximately 120 000 yr age determinations on shell fragments hiatella solida found in basal till suggest a wisconsin age for the glaciation that incorporated them the pattern of ice flow differed from that deduced for this area in the climap reconstruction following the maximum stage there was a stadial event when outlet valley glaciers flowed from smaller ice caps into george vi sound more widespread recession permitted the george vi ice shelf to deposit palmer land erratics on eastern alexander island before isostatic recovery raised them to final elevations of about 82 m the ice shelf may have been absent at about 6500 yr b p when large barnacles bathylasma corolliforme were living in the sound small glaciers readvanced to form at least two terminal moraines before the ice shelf re formed and incorporated the barnacle shells into its moraine on alexander island the shells gave a 14c age corrected for antarctic conditions of about 6500 yr b p and an amino acid ratio consistent with a holocene age valley glaciers readvanced over the ice shelf moraine before oscillations of both valley glaciers and the ice shelf led to the formation of the present sequence of contiguous ice cored moraines probably during the little ice age such oscillations may represent a climatic control not yet observed in the dry valleys of victoria land the only other part of antarctica studied in detail for glacier fluctuations

processes controlling the formation of the mertz drift george vth continental shelf east antarctica evidence from 3 5 khz sub bottom profiling and sediment cores recently discovered sediment drift deposits on the antarctic continental shelf provide access to information on the holocene palaeoceanography of the bottomcurrent regime within deep shelf basins that were previously inaccessible the george vth basin on the east antarctic margin has been identified by oceanographers as an important source of antarctic bottomwater hence the holocene history of bottomcurrent activity here may be relevant to variations in bottom water export the analysis of seismic and sediment core data indicates that the holocene history of sedimentation on the mertz drift occurred in response to a progressively changing bottom current regime the stratigraphic horizons that mark the onset of different phases of deposition are diachronous within the mertz drift rapidly accumulating laminated siliceous mud and diatom ooze smo that comprises the bulk was deposited first on the eastern side of the drift 5000 3500 years bp and later on the lobate southwestern side 3000 and 2000 years bp this spatial variation in timing of rapid smo deposition is attributed to a gradual increase in bottom current speed over the mid to late holocene the deposition of true drift style sedimentary features is restricted to a small area in the southwestern corner of the mertz drift with the remaining parts characterised by drape and fill deposits an estimation of the mass flux of sediment reaching the drift suggests that the modern stronger bottom currents need carry only a very low suspended sediment concentration to explain the measured 10 fold reduction in sediment accumulation rates after 3000 years bp cores fromthe mertz drift and froma perched basin located 60 kmto the east contain the same lithologic units and have the same approximate age thus the palaeoenvironmental interpretations based on the mertz drift can be extrapolated over the entire george vth basin region

the sedimentary legacy of a palaeo ice stream on the shelf of the southern bellingshausen sea clues to west antarctic glacial history during the late quaternary a major trough belgica trough eroded by a palaeo ice stream crosses the continental shelf of the southern bellingshausen sea west antarctica and is associated with a trough mouth fan belgica tmf on the adjacent continental slope previous marine geophysical and geological studies investigated the bathymetry and geomorphology of belgica trough and belgica tmf erosional and depositional processes associated with bedform formation and the temporal and spatial changes in clay mineral provenance of subglacial and glaciomarine sediments here we present multi proxy data from sediment cores recovered from the shelf and uppermost slope in the southern bellingshausen sea and reconstruct the ice sheet history since the last glacial maximum lgm in this poorly studied area of west antarctica we combined new data physical properties sedimentary structures geochemical and grain size data with published data shear strength clay mineral assemblages to refine a previous facies classification for the sediments the multi proxy approach allowed us to distinguish four main facies types and to assign them to the following depositional settings 1 subglacial 2 proximal grounding line 3 distal sub ice shelf sub sea ice and 4 seasonal open marine in the seasonal open marine fades we found evidence for episodic current induced winnowing of near seabed sediments on the middle to outer shelf and at the uppermost slope during the late holocene in addition we obtained data on excess pb 210 activity at three core sites and 44 ams c 14 dates from the acid insoluble fraction of organic matter aio and calcareous micro fossils respectively at 12 sites these chronological data enabled us to reconstruct for the first time the timing of the last advance and retreat of the west antarctic ice sheet wais and the antarctic peninsula ice sheet apis in the southern bellingshausen sea we used the down core variability in sediment provenance inferred from clay mineral changes to identify the most reliable aio c 14 ages for ice sheet retreat the palaeo ice stream advanced through belgica trough after similar to 36 0 corrected c 14 ka before present b p it retreated from the outer shelf at similar to 25 5 ka b p the middle shelf at similar to 19 8 ka b p the inner shelf in eltanin bay at similar to 12 3 ka b p and the inner shelf in ronne entrance at similar to 6 3 ka b p the retreat of the wais and apis occurred slowly and stepwise and may still be in progress this dynamical ice sheet behaviour has to be taken into account for the interpretation of recent and the prediction of future mass balance changes in the study area the glacial history of the southern bellingshausen sea is unique when compared to other regions in west antarctica but some open questions regarding its chronology need to be addressed by future work c 2010 elsevier ltd all rights reserved

reflectance anisotropy of upper carboniferous coals in the appalachian foreland basin pennsylvania u s a abstract patterns of vitrinite reflectance anisotropy in coal are represented by a three dimensional graphical form resembling an ellipsoid termed the vitrinite reflectance indicating surface vri naturally occurring vris from the northern appalachian basin pennsylvania range in shape from biaxial negative to biaxial positive depending on their coalification history and tectonic setting vri shapes are measured by estimating the magnitudes of the three principal reflectances rmax rint and rmin either on oriented blocks or non oriented grain mounts spatial orientations of the principal axes are determined by reflectance measurements on oriented polished cores the various vri shapes are portrayed on axial ratio diagrams i e plots of r max r int on the vertical axis and r int r min on the horizontal axis axial ratio diagrams are also used to depict the progressive change in vri shape with coalification standard deviations of the principal reflectance axes as measured on oriented cores average around 0 09 in magnitude and 5 in orientation measurements are highly reproducible between pairs of oriented cores estimates of the principal reflectance magnitudes as measured on oriented vs non oriented samples agree on average to within 0 04 for rmax 0 08 for rint and 0 20 for rint coal bearing strata in the north central coal fields medium volatile bituminous coal to semianthracite in northern pennsylvania were diagenetically altered in a predominantly burial strain environment and exhibit structural evidence of only mild tectonic deformation vris from this suite of coals are biaxial negative with rmin axes roughly perpendicular to bedding with increasing rank toward the southeast these vris plot along a straight line pathway on the axial ratio diagram emanating from near the origin and extending through the biaxial negative deformation field vris of coals from the western middle anthracite field exhibit a wide range of shapes and orientations which is indicative of a more complex tectonic history in their present day orientation rmin axes are scattered about a great circle distribution the pole to which is precisely coincident with regional fold axes when beds are unfolded to a flat lying orientation they become significantly less scattered indicating that most coalification here preceded the final phase of alleghanian folding rmax axes of sporinite grains are alwayas aligned parallel to bedding which suggests that the strata were still flat lying and not subject to tectonic forces when the coals passed through the 1st and 2nd coalification jumps

late holocene glacial advance and ice shelf growth in barilari bay graham land west antarctic peninsula three marine sediment cores were collected along the length of the fjord axis of barilari bay graham land west antarctic peninsula 65 55 s 64 43 w multi proxy analytical results constrained by high resolution geochronological methods 210 pb radiocarbon 137 cs in concert with historical observations capture a record of holocene paleoenvironmental variability our results suggest early and middle holocene 7022 2815 cal calibrated yr b p retreated glacial positions and seasonally open marine conditions with increased primary productivity climatic cooling increased sea ice coverage and decreased primary productivity during the neoglacial 2815 to cal 730 cal yr b p this climatic cooling culminated with glacial advance to maximum holocene positions and expansion of a fjord wide ice shelf during the little ice age lia ca 730 82 cal yr b p seasonally open marine conditions were achieved and remnant ice shelves decayed within the context of recent rapid regional warming 82 cal yr b p to present our findings agree with previously observed late holocene cooling and glacial advance across the antarctic peninsula suggesting that the lia was a regionally significant event with few disparities in timing and magnitude comparison of the lia antarctic peninsula record to the rest of the southern hemisphere demonstrates close synchronicity in the southeast pacific and southern most atlantic region but less coherence for the southwest pacific and indian oceans comparisons with the northern hemisphere demonstrate that the lia antarctic peninsula record was contemporaneous with pre lia cooling and sea ice expansion in the north atlantic arctic suggesting a global reach for these events

graphitization of organic matter and fluid deposited graphite in palaeoproterozoic birimian black shales of the kaya goren greenstone belt burkina faso west africa palaeoproterozoic black shales form an essential part of the birimian volcanosedimentary belt in burkina faso west africa the mean rmax values and the atomic h c values of the bulk carbonaceous matter bcm together with rock structures and mineral assemblages indicate that these carbon rich rocks were metamorphosed to sub greenschist and low grade greenschist facies x ray diffraction reveals that the 002 graphite peak width in half maximum fwhm ranges from 0 43 to 0 71 2 in sub greenschist facies and from 0 27 to 0 41 2 in greenschist facies rocks but the d 002 values in both groups of rocks are approximately the same 3 35 a the bcm of individual samples is composed of particles with very variable shape reflectance and raman spectra type i particles that predominate in sub greenschist facies are fine grained irregular or elongate bodies 1 to 3 m in size their maximum reflectance rmax ranges between 2 5 and 8 2 and raman parameters r1 and r2 range from 0 5 to 1 4 and 0 5 to 0 8 respectively type ii particles are lath shaped up to 40 m large bodies commonly arranged parallel to white mica flakes the number of these particles increases from sub greenschist to greenschist facies maximum reflectance varies between 6 and 11 2 and r1 and r2 raman parameters range from 0 05 to 0 7 and from 0 1 to 0 5 respectively type iii particles occur in hydrothermally altered and sheared rocks these are nodular aggregates composed of grains up to 10 m in size this type of particles has very high reflectance rmax 11 15 and its raman spectra indicate a very high degree of structural ordering corresponding to well ordered graphite type i particles represent original organic matter in the metasediments type ii particles are believed to have been formed either in situ by solid state transformation of type i particles or by crystallization from metamorphic fluids gradual graphitization of the type i organic particles and the growth of lath shaped type ii particles from a fluid phase is assumed to have taken place under the peak metamorphic conditions associated with the burial of birimian sediments during thrust tectonism progressive tectonic accretion and crustal thickening during the d1 event of the eburnean orogeny the growth of equant high reflectance postkinematic nodular aggregates of type iii particles is ascribed to the reduction of co2 rich fluids during a hydrothermal event associated with late eburnean d2 exhumation and strike slip movements type i carbonaceous particles were only slightly affected by high temperature low pressure contact metamorphism during intrusion of late eburnean magmatic bodies whereas formation of type ii or iii particles was not recorded in contact metamorphosed rocks at all

evaluation of the structure of bituminous coal from sośnica mine in the upper silesian coal basin poland using reflectance indicating surface ris parameters abstract the effect of a magmatic intrusion on the optical properties reflectance anisotropy and optical character of vitrinite in low rank bituminous coals was examined the study focused on coal samples collected at different distances from an intrusion emplaced into seam no 416 in so nica mine near gliwice in the upper silesian coal basin poland in the immediate contact zone coal transformed into natural coke may be seen for comparison laboratory carbonization of coals weakly changed or apparently unchanged by the intrusion was carried out the results obtained confirmed that during carbonization of the low rank coal heating alone with no external pressure makes possible the reorganization of carbon planes that is responsible for the increase of vitrinite reflectance the heating leads to the destruction of coal structure cross linkages aliphatic groups or heteroatoms and various further transformations of the structural net in addition to the removal of volatile carbonization products external pressures affect the transformation process especially by promoting the rearrangement of small structural units to form further elements of anisotropic structure thus in the case of coal from the immediate contact of the intrusion pressures resulted in values of anisotropy parameters higher than those characterizing coal heated in the laboratory up to 1200 c but in the absence of stress the source of pressure that strongly affected the coal in the mine was probably intrusion related weak tectonism in the region of the so nica mine could explain the fine biaxial optical character of the low rank parent coals more generally pressures associated with thermally evolving gasses conceivably led to the growth of structural anisotropy in the walls of degassing pores finally some structural changes seen in coal adjacent to the intrusion may reflect hydrothermal activity

late holocene palaeoclimatic records from lake sediments on james ross island antarctica sediment profiles from several lakes ponds in the northern ice free area of james ross island antarctica were the subject of a multi disciplinary palaeoenvironmental investigation the results obtained from lithological geomagnetic geochemical and diatom analyses and the frequency of branchinecta eggs were evaluated with multivariate statistics and provide a fairly detailed picture of climate change during the last 5000 years new radiocarbon dates are combined with previously published 14c dates so as to date the palaeoenvironmental and palaeohydrological changes identified by the stratigraphic studies in combination with the findings of glacial geological studies our data suggest that the brandy bay glacier began to recede rapidly just before 5000 yr b p due to calving and moisture starvation caused by cold and arid conditions in one of the ponds studied gypsum began to precipitate as a consequence of these conditions when the influence of glacial meltwater ceased this hypothesis was tested by hydrochemical modeling at approximately 4200 yr b p the climate became more humid and warmer and the pond supported a fairly diverse biota which included a variety of diatom species and for example branchinecta gaini a crustacean that feeds on benthic cyanobacterial mats the brandy bay glacier probably advanced during this humid period but the advance was interrupted by subsequent arid conditions which started at 3000 yr b p during this arid phase glaciers became completely absent from the study area as a result formerly large lakes fed by glacial meltwater transformed into small enclosed brackish water bodies that contained b gaini the arid and fairly cold conditions lasted for 1500 2000 years until approximately 1200 yr b p when the aquatic systems expanded and their salinity was lowered as a result of increased snow accumulation and glacial expansion the increased deposition of minerogenic matter caused by glacial erosion and meltwater inflow probably caused the disappearance of branchinecta on james ross island we regard this most recent phase as a period of increased humidity and warmth compared to the previous period although the conditions appear to be less warm and humid than those which prevailed during the climatic optimum between 4200 and 3000 yr b p in spite of certain correlation problems we tentatively correlate our results to other studies of holocene environments in antarctica and from that it can be suggested that the climatic optimum was of circumpolar significance therefore the climatic oscillations recorded in sediments on james ross island may reflect oscillations in the anticyclonic stormtracks and the strength of the high pressure cell over the inland ice sheet

climate since ad 1510 on dyer plateau antarctic peninsula evidence for recent climate change a 480 year record of the oxygen isotope ratios dust content chemical species and net accumulation from ice cores drilled in 1989 90 on dyer plateau in the antarctic peninsula is presented the continuous analyses of small sub annual samples reveal well preserved annual variations in both sulfate content and 18o thus allowing an excellent time scale to be established this history reveals a recent pronounced warming in which the last two decades have been among the warmest in the last five centuries furthermore unlike in east antarctica on dyer plateau conditions appear to have been fairly normal from ad 1500 to 1850 with cooler conditions from 1850 to 1930 and a warming trend dominating since 1930 reconstructed annual layer thicknesses suggest an increase in net accumulation beginning early in the 19th century and continuing to the present this intuitive conflict between increasing net accumulation and depleted 18o cooler climate in the 19th century appears widespread in the peninsula region and challenges our understanding of the physical relationships among moisture sources air temperatures and snow accumulation the complex meteorological regime in the antarctic peninsula region complicates meaningful interpretation of proxy indicators and results in a strong imprint of local high frequency processes upon the larger scale climate picture

review and update of the applications of organic petrology part 1 geological applications abstract organic petrology developed as coal petrology at the beginning of the 20th century dedicated mainly to the study of coals because of their utilization in industry coal petrology was then considered a branch of coal science later with the development of specialized nomenclature classification of coal components and the standardization and improvement of analytical microscopical methods this discipline expanded in interests and name becoming organic petrology organic petrology carries a broader context being as well a tool applied in the study of dispersed organic matter in sedimentary rocks due to its importance in exploration for fossil fuel resources at present organic petrology is a discipline widely recognized for its role in fundamental and applied research with respect to both coal utilization and in geosciences throughout the 20th century several important monographs have been published on the discipline of organic petrology including stach s textbook of coal petrology 1st edition 1935 2nd 1975 3rd 1982 updated as the more general organic petrology by taylor et al 1998 more recently the text applied coal petrology the role of petrology in coal utilization was published by suarez ruiz and crelling 2008 this review is the first in a two part review series that describes and updates the role of organic petrology in geosciences a second part complementing this one and focused on the applications of organic petrology to other scientific fields will follow

genesis and rank distribution of upper carboniferous coal basins in the cantabrian mountains northern spain abstract the cantabrian mountains located in the nw of the iberian peninsula constitute the most important coal mining district of spain anthracitic and bituminous coals high and medium rank coals have been mined in the area since the end of the nineteenth century and they currently account for about 70 of the total coal resources of the country the region forms part of the cantabrian and west asturian leonese zones of the iberian variscan fold belt and is strongly deformed by a set of imbricate thrusts coeval folds and high angle faults coal bearing successions are westphalian and stephanian pennsylvanian in age and are exposed in numerous coalfields of variable size arranged roughly parallel to the tectonic structures coal rank varies from medium rank bituminous d coals rr 0 5 to high rank anthracites a coals rr

continental rift to back arc basin jurassic cretaceous stratigraphical and structural evolution of the larsen basin antarctic peninsula the larsen basin developed in jurassic times as a result of continental rifting during the early stages of gondwana break up lower upper jurassic non marine sedimentary and volcanic rocks constitute a syn rift megasequence recording initial largely amagmatic extension and subsequent widespread extension related silicic volcanism a succeeding kimmeridgian early berriasian transgressive megasequence consisting largely of anoxic dysoxic hemipelagic mudstones is thought to have been deposited during a thermal subsidence phase when relative magmatic quiescence and peak jurassic eustatic sea levels served to maximize sediment starvation the fragmentary record for late berriasian barremian times suggests that a regressive megasequence may have developed in the earlier part of this period recording increased sediment yield to the larsen basin from the increasingly emergent antarctic peninsula arc subsequently strata in the southern but not the northern part of the basin underwent relatively intense eastward verging deformation possibly during the formation of a retro arc fold thrust belt where exposed the lower part of the succeeding aptian eocene megasequence consists of a deep marine clastic wedge deposited along the fault bounded western basin margin during a phase of arc uplift and related differential subsidence following partial basin inversion in late cretaceous times regression took place as reduced basinal subsidence rates allowed shallow marine facies to prograde basinward

flow dynamics and till genesis associated with a marine based antarctic palaeo ice stream geophysical and geological data indicate that during the last glacial cycle a palaeo ice stream drained the antarctic peninsula ice sheet apis through marguerite bay to the edge of the continental shelf via a bathymetric trough marguerite trough mega scale glacial lineations msgl in outer marguerite trough are formed in an acoustically transparent sediment unit consisting of a soft deformation till the association of msgl with deformation till indicates that bed deformation occurred beneath the ice stream and the thickness of the subglacial deforming layer was on the order of several metres msgl within outer marguerite trough are related to a pre existing thick sequence of soft sediments on the outer shelf and are inferred to have formed by a combination of subglacial sediment deformation by attenuation from a point source and groove ploughing morphologically the msgl differ in several respects from those documented elsewhere and this variation suggests a polygenetic origin for this subglacial landform an initial advance of the apis across the marguerite bay continental shelf at the lgm deposited a stiff subglacial till following this advance the ice margin within marguerite trough retreated 70 100 km before stabilising and depositing a grounding zone wedge an ice stream then developed in the trough and extended to the shelf edge forming a soft deformation till development of the ice stream may have been a glacio dynamic response to regional deglaciation subsequent retreat of the marguerite trough ice stream was underway by 13 490 uncorrected 14c years before present based on the geophysical and core data ice stream retreat appears to have been rapid and it contrasts with reconstructions of palaeo ice streams from other locations in antarctica this implies marked regional variations in antarctic ice stream dynamics during late quaternary deglaciation

trends and connections across the antarctic cryosphere satellite observations have transformed our understanding of the antarctic cryosphere the continent holds the vast majority of earth s fresh water and blankets swathes of the southern hemisphere in ice reductions in the thickness and extent of floating ice shelves have disturbed inland ice triggering retreat acceleration and drawdown of marine terminating glaciers the waxing and waning of antarctic sea ice is one of earth s greatest seasonal habitat changes and although the maximum extent of the sea ice has increased modestly since the 1970s inter annual variability is high and there is evidence of longer term decline in its extent this paper discusses how antarctic ice has changed over recent decades and how these changes have been recorded in satellite observations

recognition of vitrinite with non uniaxial negative reflectance characteristics non uniaxial negative reflectance characteristics are being reported for coals from around the world with increasing frequency these data have traditionally been collected from oriented sections cut from a block of coal to determine the magnitudes of the principal reflectance axes to make data collection less time consuming a method of determining the principal reflectance axes from a standard crushed coal sample has been developed the method requires measurement of the maximum and minimum apparent reflectances from a series of randomly oriented vitrinite particles the reflectance crossplot displays these two reflectance values against their difference or bireflectance the paper describes the method of interpreting the resultant pattern to determine the values of the three principal reflectance axes analysis of coals from the british columbia rocky mountains and foothills revealed biaxial and uniaxial positive as well as uniaxial negative reflectance characteristics a new measure of maturation rev is proposed which is based purely on the lengths of the three principal reflectance axes rm approximates this value but is influence by any eccentricity of the reflectance indicating surface ris vitrinite with a non uniaxial reflectance characteristics cannot be adequately described by a single measure such as rmaxorrm but requires reference to both the size and shape of the ris a reflectance determination such as rev or rm provides rank astm information whereas the new measures rst and ram describe a reflectance indicating surface shape which is the result of maturation and tectonic histories vitrinites with non uniaxial negative reflectance characteristics are abundant in the coalfields of the rocky mountains and foothills of british columbia rmax does not fully describe the reflectance character of these coals and does not describe the potentially useful ris shape

rapid collapse of northern larsen ice shelf antarctica in january 1995 4200 square kilometers of the northern larsen ice shelf antarctic peninsula broke away radar images from the ers 1 satellite complemented by field observations showed that the two northernmost sections of the ice shelf fractured and disintegrated almost completely within a few days this breakup followed a period of steady retreat that coincided with a regional trend of atmospheric warming the observations imply that after an ice shelf retreats beyond a critical limit it may collapse rapidly as a result of perturbated mass balance

marine record of holocene climate ocean and cryosphere interactions herbert sound james ross island antarctica abstract the sediment record offshore james ross island northeast antarctic peninsula presents an unparalleled opportunity to directly compare marine and terrestrial climate records spanning the holocene in maritime antarctica an 11 m drill core was collected between herbert sound and croft bay as part of the shaldril nbp 0502 initiative and produced the southernmost sediment record from the eastern side of the ap thirty eight radiocarbon ages are used to construct an age model of centennial scale resolution multi proxy records including magnetic susceptibility pebble content particle size total organic carbon and diatom assemblages were interrogated in the context of nearby holocene age ice core lake and drift records from james ross island differences in the timing and expression of holocene events reflect marine controls on tidewater glaciers such as water mass configurations and sea ice glacial behavior mimics ice core paleotemperatures during the holocene with the exception of distinct ocean warming events herbert sound was fully occupied by grounded ice during the last glacial maximum and experienced rapid lift off followed by a floating ice phase the canopy of floating ice receded by 10 2 4 cal kyr bp presumably in response to early holocene warming herbert sound and croft bay fully deglaciated by 7 2 cal kyr bp when the mid holocene hypsithermal commenced and the sound became open and productive an extreme peak in productivity 6 1 cal kyr bp indicates an oceanic warming event that is not reflected in atmospheric temperature or lacustrine sediment records increase in sea ice cover and ice rafting mark the onset of the neoglacial 2 5 cal kyr bp when pronounced atmospheric cooling is documented in the james ross island ice core our comparison facilitates more holistic understanding of atmosphere ocean cryosphere interactions that may aid predictions of glacial response to future warming and sea level scenarios

antarctic palaeo ice streams we review the geomorphological sedimentological and chronological evidence for palaeo ice streams on the continental shelf of antarctica and use this information to investigate basal conditions and processes and to identify factors controlling grounding line retreat a comprehensive circum antarctic inventory of known palaeo ice streams their basal characteristics and minimum ages for their retreat following the last glacial maximum lgm is also provided antarctic palaeo ice streams are identified by a set of diagnostic landforms that nonetheless display considerable spatial variability due to the influence of substrate flow velocity and subglacial processes during the lgm palaeo ice streams extended via bathymetric troughs to the shelf edge of the antarctic peninsula and west antarctica and typically to the mid outer shelf of east antarctica the retreat history of the antarctic ice sheet since the lgm is characterised by considerable asynchroneity with individual ice streams exhibiting different retreat histories this variability allows antarctic palaeo ice streams to be classified into discrete retreat styles and the controls on grounding line retreat to be investigated such analysis highlights the important impact of internal factors on ice stream dynamics such as bed characteristics and slope and drainage basin size whilst grounding line retreat may be triggered and to some extent paced by external atmospheric and oceanic forcing the individual characteristics of each ice stream will modulate the precise timing and rate of retreat through time

palaeolimnological evidence for marked holocene environmental changes on signy island antarctica lake sediment cores from heywood and sombre lakes on signy island south orkney islands antarctica have yielded a conformable radiocarbon chronology for the holocene and a high resolution record of environmental change the lakes share a common climate and geology but have distinct catchments this provides an opportunity for using lake sediments to differentiate between local within lake catchment events and those at a regional scale analyses of various biological and physical remains from the lakes suggest that both catchments have undergone considerable changes during the last 5700 years macrofossils moss and crustacean remains are more abundant in the late holocene being associated with a period of high sediment accumulation which is related to diatom evidence for more nutrient rich conditions at the sites this is inter preted as a response to a holocene climate optimum at c 3800 1300 14 c yr bp the record is consistent with other lake ice and ocean core studies although the climate optimum appears to have persisted for a longer period at signy island

vitrinite anisotropy resulting from simple shear experiments at high temperature and high confining pressure abstract orientations of r 0 max and r 0 min of vitrinite have been determined in coal samples that have been deformed in simple shear experiments at t 650 900 c confining pressures of 0 8 and 1 0 gpa and constant displacement rates of 10 5 10 6 s 1 samples chosen are a high volatile bituminous coal and two anthracites shear strains up to 3 0 were attained in experiments that lasted up to 100 h high temperature and large strains have facilitated an increase in r 0 max an increase in anisotropy bireflectance and reorientation of r 0 max and r 0 min results of these experiments indicate that tectonic strain at and above semi anthracite rank enhances the degree of molecular ordering leading to preferential growth of graphite and that vitrinite anisotropy may track with tectonic strain

precursor and metamorphic condition effects on raman spectra of poorly ordered carbonaceous matter in chondrites and coals abstract geothermometers based on raman spectrometry of carbonaceous matter and covering a wide range of temperatures 100 650 c have been developed over recent years while raman data have been largely interpreted in terms of temperature they are also the fingerprint of certain metamorphic conditions especially in the low temperature range relevant to poorly ordered carbonaceous matter this study investigates the raman spectra of two series of chondritic carbonaceous matter and coal samples formed from different precursors and under different metamorphic conditions the raman spectra of polyaromatic carbonaceous matter pcm from 42 chondrites and 27 coal samples measured with visible 514 nm and ultra violet 244 nm excitation wavelengths are analyzed the raman spectra of low rank coals and chondrites of petrologic types 1 and 2 which contain the more disordered pcm reflect the distinct carbon structures of their precursors the 514 nm raman spectra of high rank coals and chondrites of petrologic type 3 exhibit continuous and systematic spectral differences reflecting different carbon structures present during the metamorphism event they result from differences in the chemical structures of the precursors concerning for instance the reticulation of polyaromatic units or an abundance of ether functional groups or possibly from a lack of carbonization processes to efficiently expel oxygen heteroatoms due to weak lithostatic pressure and confinement these results suggest that the use of low temperature carbon thermometers should be restricted to a given geological context at the same time the sensitivity of raman spectra to precursors and certain metamorphic conditions could be used to obtain information other than temperature the analysis also provides evidence of the accretion of relatively homogeneous pcm precursors among ordinary co and cv carbonaceous chondrite parent bodies given that the 514 nm raman spectra of pcm efficiently trace the metamorphism grades looking closer however the 514 nm raman data are more scattered in chondrites than in coals and the maturity tracers are less sensitive and miscorrelate with the atomic h c ratio suggesting slight compositional and structural differences among the pcm precursors accreted

first synchronous retreat of ice shelves marks a new phase of polar deglaciation it is now 10 y since field observations and radarsat imagery witnessed the breakup of the ward hunt ice shelf on ellesmere island canada this was the largest remaining ice shelf in the arctic and one of the last fragments of the 8 900 km2 ellesmere ice shelf charted by the aldrich 1875 1876 and peary 1906 expeditions 1 its breakup has been linked to the polar amplification of climate change being witnessed in the wider arctic region 2 including the ongoing reduction in the extent and duration of sea ice 3 similar ice shelf retreats have been reported from the antarctic peninsula region 4 the key question is the following have the polar ice shelves broken up before under natural conditions or are these unique events triggered by anthropogenic climate forcing in pnas antoniades et al 5 report a marine geological reconstruction of the holocene history of the ward hunt ice shelf they found that the northern coast of ellesmere island has been free of a bounding ice shelf through most of the past ca 11 500 y the holocene epoch and that ice shelves have only been present there between 4 000 and 1 400 calibrated radiocarbon years before present cal y b p and from 800 cal y b p until the recent break up event this has built on previous work on radiocarbon dated ancient driftwood deposited along the northern coast of ellesmere island that could have arrived there either during periods of ice shelf absence or as a result of changes in the configuration of ocean currents and sea ice 6

oxidatively and thermally altered high volatile bituminous coals in high temperature coal fire zone no 8 of the wuda coalfield north china abstract coal fires have received increasing attention due to their environmental economic and social impacts their significant influence on coal properties is widely documented by geophysical and geochemical methods the present paper demonstrates by means of coal petrological methods significant changes of microstructure optical appearance and optical properties of medium rank bituminous coals affected by an underground coal fire the studied changes are suggested to result from distinct oxidative and thermal alterations induced by a high temperature regime temperatures over 800 c encountered in the coal fire zone no 8 wuda coalfield the investigated coal seam no 9 represents a high volatile a bituminous coal and is dominated by vitrinite followed by inertinite with minor amounts of liptinite the microstructure of the coal fire affected coals facilitate a broad spectrum of characteristic features the microscopic analyses revealed development of 1 non tectonic fissures and non tectonic fractures 2 distinct micropores 3 dark oxidations rims and 4 bright spots interpreted as incipient mesophases optical properties were characterised for megasporinite and vitrinite in the examined megasporinite a noticeable anisotropy and distinct granular appearance was observed in the investigated coals both a dominant increase as well as a minor decrease in both random and maximum vitrinite reflectances were documented for 1 coal grains and 2 dark rimmed vitrinite at non tectonic fissures and non tectonic fractures in addition also a characteristic bimodal vitrinite population was measured the increase in bireflectance was clearly documented for two sub zones within the coal fire zone no 8 the applied kilby s cross plots suggested a large overlapping of the data sets of r max and r min indicating marked changes in vitrinite structure the applied coal petrological approach revealed distinct changes to the coal s microstructure appearance as well as to optical properties induced by the underground coal fire the presented coal petrographic approach may help determine the extent of coal fires in coal mines and the direction of propagation of coal fire front

deep water sedimentary environments of the northwestern weddell sea and south sandwich islands antarctica abstract two transects have been sampled using short cores multi and box seabed photography video sequences and sediment profile images across the northwestern weddell sea and south sandwich forearc antarctica a total of 12 core stations were examined for sediment structure texture and composition to determine their depositional history four of the core stations from the weddell continental slope abyssal plain and south sandwich forearc and trench were further examined for trace metal analysis ba u mn and pb for sediment source and palaeoproductivity and 210pb for age profiles and depth of mixing by bioturbation the 3055 m station at the base of the weddell continental slope recovered laminated muddy silty contourites with a surface layer of hemipelagites with abundant ice rafted debris possibly originating from the 1995 larsen a and 2002 larsen b ice shelf disintegration this is interpreted as a moderate energy depositional environment influenced by weddell sea bottom water along slope current reworking sediment sediment sources to this station include the direct input of clastic material from ice with variation in sediment sources from in situ current winnowing and along slope transport reflected in the mn li and ba li ratios the 4760 m station on the weddell abyssal plain recovered hemipelagites interpreted as a low energy depositional environment with sediment supplied both from direct ice rafting and pelagic settling during productive seasonally ice free periods the 210pb profiles indicate a sedimentation rate of 0 024 cm year 1 with the 206 207pb isotope ratios suggesting a principle sediment source from ice rafting the 2292 and 6326 m stations from the slope and floor of the south sandwich forearc recovered pelagic and turbiditic sediments this is interpreted as a high energy down slope depositional environment with high surface biogenic productivity and sediment supply leading to localised down slope mass movements on the slope and floor high levels of mn li and elevated u li ratios demonstrate a strong concentration of mn in organic poor sediment the mn redoxcline is present at 10 cm depth the high ba li 500 ppm in the forearc floor core reflects some limited enhanced productivity source sediment for the forearc may in part be derived from the northwest weddell abyssal plain based on the 206 207pb isotope ratios reflecting transport by weddell sea bottom water

conversion of carbonaceous material to graphite within the greywacke zone of the eastern alps morphology and reflectance of carbonaceous material cm in late carboniferous metasediments of the eastern greywacke zone eastern alps indicate a mixture of vitrinite grainy textured and lamellar shaped particles as imaged by high resolution atomic force microscopy vitrinite and the grainy textured particles show mesophase structures which can be described as facetted nanocrystals within the carbon matrix high resolution transmission electron microscopy has revealed two types of microtextures representing different degrees of graphitization the first type is characterized by elongated ring shaped microtextures whereas the second type is characterized by graphite lamellae and polygonal flakes with long range ordered aromatic layers in spite of the heterogeneity of the cms the geographical distribution of quantitative metamorphic parameter raman spectra parameter x ray diffraction pattern microscopic reflectance suggests a graphitization process which is promoted by advective heat transport during post collisional processes in a tentative pressure time path late cretaceous thrusting results in a turbostratic ordering of the aromatic layer ordering to long range ordered aromatic layers was achieved during the late cretaceous paleogene exhumation of mid crustal rocks beneath the eastern greywacke zone

reflectance anisotropy and syn deformational coalification of the jewel seam in the cadomin area alberta canada abstract the jewel seam of the cadomin area is complexly folded and cut by several thrust faults vitrinite reflectance anisotropy was determined from twenty oriented coal blocks collected from various structural positions five of the blocks have uniaxial anisotropies five have biaxial positive anisotropies the remaining ten are biaxial negative the biaxial coals display maximum reflectance axes parallel to nearby fold axes which suggests a relationship between vitrinite anisotropy and deformation the biaxial vitrinite reflectance ellipsoids result from superposition of tectonic strains on a primary sedimentary burial related uniaxial anisotropy a tectonic stress field was probably present during the later stages of sedimentary burial and subsequent deformation coalification resulted largely from pre deformational sedimentary burial but the final coalification stage was syn deformational as illustrated by the intersection of isorank surfaces and the jewel seam and the biaxial vitrinite reflectance anisotropy

on the optically biaxial character and heterogeneity of anthracites abstract the results of the study of optical properties of 13 anthracites from different parts of the world are presented in this paper measurements of reflectance values were made on non oriented vitrinite grains for a minimum of 300 points per sample the reconstruction of reflectance indicating surfaces ris were made by kilby s method kilby w e 1988 recognition of vitrinite with non uniaxial negative reflectance characteristics int j coal geol 9 267 285 kilby w e 1991 vitrinite reflectance measurement some technique enhancements and relationships int j coal geol 19 201 218 it was found that the use of kilby s method for strongly anisotropic materials like anthracites did not give unambiguous results some improvement in kilby s method consisting of the division of the cumulative cross plot into several elemental components is suggested each elemental cross plot corresponds to a textural class of anthracite which is characterized by the values of ris main axes rmax k rint k and rmin k k 1 2 n n number of classes the global texture of anthracite is characterized as a ris with main axes calculated as the weighted means of r max r int and r min for each class of this anthracite the division of cumulative kilby s cross plot on elemental components makes possible the calculation of new coefficients ht and h10 characterizing the heterogeneity of the structure and texture of anthracites the results of our study show that all anthracites have biaxial negative textures but their heterogeneity varies in a wide range of ht and h10 coefficients depending upon the individual coal basin

facies and depositional processes in an upper jurassic to lower cretaceous pelagic sedimentary sequence antarctica the nordenskjold formation oxfordian berriasian age is exposed on the east coast of the antarctic peninsula where it consists of interbedded ash layers and biosiliceous mudstones which accumulated under anaerobic to dysaerobic bottom waters the mudstones were deposited by pelagic settling and the ash layers by pelagic settling from suspension or as fallout from subaerial eruption columns the lower part of the succession accumulated in a basinal setting under anaerobic bottom waters and is characterized by parallel bedding mudstones deposited in this setting preserve abundant zooplankton faecel pellets compaction of these pellets has given rise to a bedding parallel fissility the upper part of the succession accumulated under dysaerobic bottom waters in a slope setting the sequence is wavy bedded and contains abundant evidence of post depositional sediment instability and resedimentation much of which was caused by tectonic activity discrete slide masses are absent from the slope sequence and it appears that slope processes were dominated by creep examination of the mudstones shows that as levels of dissolved oxygen in bottom waters increase pelleted mudstones give way to structureless mudstones before visible bioturbation is noted

recent atmospheric warming and retreat of ice shelves on the antarctic peninsula in 1978 mercer1 discussed the probable effects of climate warming on the antarctic ice sheet predicting that one sign of a warming trend in this region would be the retreat of ice shelves on the antarctic peninsula analyses of 50 year meteorological records have since revealed atmospheric warming on the antarctic peninsula2 3 and a number of ice shelves have retreated4 8 here we present time series of observations of the areal extent of nine ice shelves on the antarctic peninsula showing that five northerly ones have retreated dramatically in the past fifty years while those further south show no clear trend comparison with airtemperature data shows that the pattern and magnitude of ice shelf retreat is consistent with the existence of an abrupt thermal limit on iceshelf viability the isotherm associated with this limit having been driven south by the atmospheric warming ice shelves therefore appear to be sensitive indicators of climate change

relationship between structure morphology and carbon isotopic composition of graphite in marbles implications for calcite graphite carbon isotope thermometry carbon isotope exchange between calcite and graphite is a useful and reliable geothermometer for medium to high grade marbles however in rare instances such as at naxos greece apparent disequilibrium carbon isotope fractionation between calcite and graphite has been previously reported in this study new results are presented on the morphological features x ray diffraction studies raman spectroscopic studies and carbon isotope studies of graphite three morphologically distinct graphite types are identified the first type is fine grained with distinct polygonal crystal aggregates having smooth pinacoid faces the second type consists of large botryoidal aggregates with typical crystal overgrowth features and the third type is normal large platy crystals associated with phlogopite graphite morphological features using an fe sem suggests that the botryoidal aggregates are composed of complexly intergrown and stacked graphite layers comprised of cone helix structures different types of graphite display distinct lc 002 and dg values as well as a sharp first order raman peak at 1580 cm 1 with disordered bands the presence of raman disordered bands in fine grained well crystallized graphite is attributed to edge effects carbon isotope analysis of graphite reveals that marble with fine grained well crystallized graphite show a consistent isotope fractionation with the calcite which perfectly match temperature estimates based on the mineral isograds in contrast coarse botryoidal graphite gives heterogeneous carbon isotope values about a few per mill and show anomalous carbon isotope fractionation between the calcite and graphite the graphite associated with phlogopite also shows variations in the carbon isotope values combining morphologic crystallographic and carbon isotopic data we conclude that the variations in carbon isotopic composition were caused by the overgrowth of graphite on the preexisting grain and that morphological observations and structural characterizations of graphite crystals is a key for predicting isotopic equilibration during metamorphism

raman spectroscopy of selected carbonaceous samples abstract this paper presents the results of raman spectra measured on carbonaceous materials ranging from greenschist facies to granulite facies graphite anchimetamorphism and epimetamorphism zones raman spectroscopy has come to be regarded as a more appropriate tool than x ray diffraction for study of highly ordered carbon materials including chondritic matter soot polycyclic aromatic hydrocarbons and evolved coal samples this work demonstrates the usefulness of the raman spectroscopy analysis in determining internal crystallographic structure disordered lattice heterogeneity moreover this methodology permits the detection of differences within the meta anthracite rank semi graphite and graphite stages for the samples included in this study in the first order raman spectra the bands located near to c a 1350 cm 1 defects and disorder mode a 1g and 1580 cm 1 in plane e 2g zone centre mode contribute to the characterization and determination of the degree of structural evolution and graphitization of the carbonaceous samples the data from raman spectroscopy were compared with parameters obtained by means of structural chemical and optical microscopic analysis carried out on the same carbonaceous samples the results revealed some positive and significant relationships although the use of reflectance as a parameter for following the increase in structural order in natural graphitized samples was subject to limitations

mechanisms of holocene palaeoenvironmental change in the antarctic peninsula region the antarctic peninsula is one of the three fastest warming regions on earth here we review holocene proxy records of marine and terrestrial palaeoclimate in the region and discuss possible forcing mechanisms underlying past change with a specific focus on past warm periods our aim is to critically evaluate the mechanisms by which palaeoclimate changes might have occurred in order to provide a longer term context for assessing the drivers of recent warming two warm events are well recorded in the holocene palaeoclimate record namely the early holocene warm period and the mid holocene hypsithermal mhh whereas there are fewer proxy data for the mediaeval warm period mwp and the recent rapid regional rrr warming we show that the early holocene warm period and mhh might be explained by relatively abrupt shifts in position of the southern westerlies superimposed on slower solar insolation changes a key finding of our synthesis is that the marine and terrestrial records in the ap appear to show markedly different behaviour during the mhh this might be partly explained by contrasts in the seasonal insolation forcing between these records circumpolar deep water cdw has been implicated in several of the prominent changes through the holocene but there are still differences in interpretation of the proxy record that make its influence difficult to assess further work is required to investigate contrasts between marine and terrestrial proxy records east west contrasts in palaeoclimate the history of cdw to retrieve a long onshore high resolution record of the holocene and determine the role of sea ice in driving or modulating palaeoclimate change along with further efforts to study the proxy record of the rrr and the mwp

first survey of antarctic sub ice shelf sediments reveals mid holocene ice shelf retreat the retreat of five small antarctic peninsula ice shelves in the late 20th century has been related to regional possibly anthropogenic climate warming we use the record of ice rafted debris ird in cores to show that the prince gustav channel ice shelf also retreated in mid holocene time early and late holocene age sediments contain ird derived entirely from local ice drainage basins which fed the section of ice shelf covering each site core top and mid holocene 5 2 ka sediments include a wider variety of rock types recording the drift of far traveled icebergs which implies seasonally open water at the sites the period when the prince gustav ice shelf was absent corresponds to regional climate warming deduced from other paleoenvironmental records we infer that the recent decay cannot be viewed as an unequivocal indicator of anthropogenic climate perturbation

living stained and dead foraminifera from the newly ice free larsen ice shelf weddell sea antarctica ecology and taphonomy within the past 7 years the northern larsen ice shelf has broken up so it is now possible to sample the sea floor that formerly lay beneath it box cores have yielded surface sediment samples 0 1 cm that give information on living and dead foraminiferal assemblages the living assemblages are of moderate diversity and four have 50 calcareous tests while five have 50 agglutinated tests this is an area of high primary production and the standing crops of the benthic foraminiferal assemblages are high all the dead assemblages are much enriched in agglutinated tests often 90 they give a time averaged record of the past 7 ice free years and several decades of ice cover the loss of permanent ice cover there is still seasonal ice cover may have caused some response from the fauna but it is likely that it was mainly changes in relative absolute abundance of the existing fauna the differences between the live and dead assemblages in the surface 1 cm are attributed mainly to taphonomic effects dissolution of calcareous tests and loss of fragile agglutinated tests subsurface samples down to 5 cm show that dissolution of calcareous tests is widespread and there may be some loss of fragile agglutinated forms such as reophax subdentaliniformis for these reasons in this area it may be best to make palaeoecological interpretations on the agglutinated component of the fossil assemblages

fault induced perturbed stress fields and associated tensile and compressive deformation at fault tips in the ice shell of europa implications for fault mechanics secondary fractures at the tips of strike slip faults are common in the ice shell of europa large magnitude perturbed stress fields must therefore be considered to be a viable driving mechanism for the development of part of the fracture sequence fault motions produce extensional and compressional quadrants around the fault tips theoretically these quadrants can be associated with tensile and compressive deformational features i e cracks and anti cracks respectively accordingly we describe examples of both types of deformation at fault tips on europa in the form of extensional tailcracks and compressional anti cracks the characteristics of these features with respect to the plane of the fault create a fingerprint for the mechanics of fault slip accumulation when compared with linear elastic fracture mechanics lefm models of perturbed stress fields around fault tips tailcrack kink angles and curving geometry can be used to determine whether opening accompanies sliding motion kink angles in the 50e70 range are common along strike slip faults that resemble ridges and indicate that little to no opening accompanied sliding in contrast tailcrack kink angles are closer to 30 for strike slip faults that resemble bands with tailcrack curvatures opposite to ridge like fault examples indicating that these faults undergo significant dilation and infill during fault slip episodes anti cracks which may result from compression and volume reduction of porous near surface ice have geometries that further constrain fault motion history corroborating the results of tailcrack analysis the angular separation between anti cracks and tailcracks are similar to lefm predictions indicating the absence of cohesive end zones near the tips of europan faults hence suggesting homogeneous frictional properties along the fault length tailcrack analysis can be applied to the interpretation of cycloidal ridges chains of arcuate cracks on europa that are separated by sharp kinks called cusps cusp angles are reminiscent of tailcrack kink angles along ridge like strike slip faults cycloid growth in a temporally variable tidal stress field ultimately resolves shear stresses onto the near tip region of a growing cycloid segment thus resultant slip and associated tailcrack development may be the driving force behind the initiation of the succeeding arcuate segment hence facilitating the ongoing propagation of the cycloid chain 2005 elsevier ltd all rights reserved