wind effects on estimates of sea level rise 1 variability in sea level at the longest periods observable in modern records has recently been found to be well correlated with local atmospheric pressure at shorter periods however longshore winds are known to be one of the primary mechanisms for forcing sea level variability on the eastern margins of the ocean there is a remarkable 80 mm drop in mean sea level on both the eastern north pacific and north atlantic coasts between the late 1800s and early 1900s it is found here to be in agreement with longshore wind forcing from the equator up to the latitude of the observed tide stations better resolved data beginning in 1960 show that the delay near the annual period between wind forcing and sea level is approximately 1 month the relative high in sea level in the late 1800s on the west coast of europe appears to have propagated westward across the atlantic as a long rossby wave and then to have been seen on the east coast of the united states because many features in long term sea level variability are correlated with wind forcing on time scales from annual to decades it will be prudent to base conclusions about long term sea level rise on the longest records available the results here are based on forcing by longshore winds the related issue of the extent to which open ocean wind curl may also be responsible is not addressed here nor the extent to which coastal sea level observations are representative of the open ocean

low frequency variability in coastal sea level from tide gauges and altimetry 1 long sea level observations are fundamental for studies of the low frequency changes in ocean circulation and climate tide gauges provide records several decades long but their locations are geographically sparse and confined to the coastline to assess the extent to which tide gauge point measurements represent broader scale conditions in the adjacent ocean we compare tide gauge records to altimeter data in their vicinity for the period 1993 2008 the analysis is based on detrended annual mean series and focuses on interannual variability the best agreement between tide gauge and altimeter series is found for mid ocean islands in the tropical pacific and indian oceans and along the coast of western australia elsewhere along most continental coasts root mean square differences between the two sea level estimates can be substantial when compared to the observed variability or the expected measurement noise with the worst correspondence found in western south america japan and eastern australia differences in magnitude as well as poor correlations between the tide gauge and altimeter estimates are involved although land motions and measurement errors can be a factor results point to the presence of considerable short spatial structure in coastal sea level at interannual time scales which can be related to the low frequency dynamics of coastally trapped circulations western boundary currents and associated eddy regimes or response to river runoff knowing whether coastal sea level variability becomes more spatially homogeneous at longer time scales must await longer sea level records

geochemistry and origin of archaean quartz cordierite gneisses from the godthabsfjord region west greenland we report new data on the major minor and trace element compositions of metasedimentary quartzcordierite gneisses qcg an important member of the archaean malene supracrustal suite found throughout the godthabsfjord region of west greenland the analyzed qcg contain assemblages of quartz cordierite biotite garnet anthophyllite gedrite staurolite sillimanite plagioclase with abundant accessory zircon and minor rutile monazite and allanite and broadly resemble cordierite orthoamphibole rocks found in a great number of other metamorphic terrains chemically the qcg are characterized by 1 high but variable sio2 59 87 wt relative enrichments in mgo feo and al2o3 mg 0 35 0 85 and depletions in na2o k2o and especially cao 2 low concentrations of sc cr co ni and sr 3 high concentrations of y nb zr hf ta th u and ree rare earth elements with prominent negative eu anomalies in each case 5 high concentrations of ga 18 55 ppm with variable ga al ratios that are significantly higher than average crustal material low cr and ni together with enriched and fractionated ree displaying negative eu anomalies distinguish the malene qcg from published accounts of most other archaean sedimentary rocks furthermore all of the above mentioned trace element characteristics distinguish the qcg from ordinary malene clastic metasediments quartzites psammites and pelites suggesting a separate origin for the qcg these data point towards chemically evolved felsic igneous rocks being the source of the qcg consequently we propose that the malene qcg represent metamorphosed felsic volcaniclastic sediments that underwent hydrothermal alteration by heated seawater prior to metamorphism which resulted in gain of mg and fe loss of alkalis and lime and possibly eu and sr the overall trace element characteristics of the qcg elevated ga zr nb ree etc are features shared by a type granites and their volcanic equivalents such igneous rocks may represent the ultimate source material for the qcg protolith

pyrite formation in an anoxic estuarine basin in a shallow fjord like estuary the upper and lower basins of the pettaquamscutt river rhode island each contain water columns stratified into oxic and anoxic plus sulfidic layers both water columns contain iron monosulfides and pyrite from just below the oxic anoxic interface down to the sediment water interface concentrations of iron monosulfides increase with increasing depth in the water columns but concentrations of pyrite are relatively constant with depth suspended pyrite is present only as framboids whereas the underlying sediments contain dominantly framboids but also euhedral grains and infilled framboids based on pyrite textures s isotopic compositions of water column and sediment sulfides and settling rate calculations about 70 of the pyrite burial flux to the pettaquamscutt sediments is accounted for by framboids forming at the oxic anoxic interface and settling to the sediment water interface the remaining pyrite burial flux is secondary pyrite nucleation and growth within the sediments represented by euhedral grains and infilled framboids the s isotopic composition of pyrite in the pettaquamscutt sediments and presumably of pyrite in the sediments of other modern anoxic basins and analogous ancient sediments therefore contains a component originating near the oxic anoxic interface and a component added below the sediment water interface pyrite framboids form in the water column where there is high supersaturation with respect to pyrite and slight undersaturation with respect to the iron monosulfides we propose that framboid nucleation and growth occurs in the water column adjacent to and below the oxic anoxic interface where supplies of ferrous species sulfide species and suitable electron acceptors are available infilled and overgrown framboids from in the sediments as a result of surface nucleation and continued pyrite growth on framboids that originate above the sediment water interface

grace measurements of mass variability in the earth system monthly gravity field estimates made by the twin gravity recovery and climate experiment grace satellites have a geoid height accuracy of 2 to 3 millimeters at a spatial resolution as small as 400 kilometers the annual cycle in the geoid variations up to 10 millimeters in some regions peaked predominantly in the spring and fall seasons geoid variations observed over south america that can be largely attributed to surface water and groundwater changes show a clear separation between the large amazon watershed and the smaller watersheds to the north such observations will help hydrologists to connect processes at traditional length scales tens of kilometers or less to those at regional and global scales

global and regional sea level change during the 20th century sea level variations prior to the launch of satellite altimeters are estimated by analyzing historic tide gauge records recently a number of groups have reconstructed sea level by applying eof techniques to fill missing observations we complement this study with alternative methods in a first step gaps in 178 records of sea level change are filled using the pattern recognition capabilities of artificial neural networks afterward satellite altimetry is used to extrapolate local sea level change to global fields patterns of sea level change are compared to prior studies global mean sea level change since 1900 is found to be 1 77 0 38 mm yr 1 on average local trends are essentially positive with the highest values found in the western tropical pacific and in the indian ocean east of madagascar where it reaches about 6 mm yr 1 regions with negative trends are spotty with a minimum value of about 2 mm yr 1 south of the aleutian islands although the acceleration found for the global mean 0 0042 0 0092 mm yr 2 is not significant local values range from 0 1 mm yr 2 in the central indian ocean to 0 1 mm yr 2 in the western tropical pacific and east of japan these extrema are associated with patterns of sea level change that differ significantly from the first half of the analyzed period i e 1900 1950 to the second half 1950 2000 we take this as an indication of long period oceanic processes that are superimposed to the general sea level rise

precambrian paleosols in canada although at least 38 precambrian paleosols have been reported in canada few have received the attention afforded most other geological phenomena the most intensively studied of these are widely distributed early proterozoic paleosols associated with the sub huronian and matonabbee new name unconformities criteria that have been most useful in identifying precambrian paleosols in canada include macrostructures ascending protolith disruption saprolith and corestones micromorphology sepic texture and peds mineralogical changes dissolution transformation geochemical signatures ascending depletion of some elements characteristic weathering indices and distinctive colour contrast diagenetic mechanical and geochemical overprinting of the paleosols evident in many canadian examples includes paleosol compaction veins cutting pedogenic features and widespread alkali and alkaline earth element metasomatism metamorphism and deformation also tend to mask pedogenic features as attested by th

geochemistry of archean shales from the pilbara supergroup western australia archean clastic sedimentary rocks are well exposed in the pilbara block of western australia shales from turbidites in the gorge creek group ca 3 4 ae and shales from the whim creek group ca 2 7 ae have been examined the gorge creek group samples characterized by muscovite quartzchlorite mineralogy are enriched in incompatible elements k th u lree by factors of about two when compared to younger archean shales from the yilgarn block alkali and alkaline earth elements are depleted in a systematic fashion according to size when compared with an estimate of archean upper crust abundances this depletion is less notable in the whim creek group such a pattern indicates the source of these rocks underwent a rather severe episode of weathering the gorge creek group also has fairly high b content 85 29 ppm which may indicate normal marine conditions during deposition rare earth element ree patterns for the pilbara samples are characterized by light ree enrichment lanybn 7 5 and no or very slight eu depletion eueu 0 82 0 99 a source comprised of about 80 felsic igneous rocks without large negative eu anomalies felsic volcanics tonalites trondhjemites and 20 mafic ultramafic volcanics is indicated by the trace element data very high abundances of cr and ni cannot be explained by any reasonable provenance model and a secondary enrichment process is called for

improving sea level reconstructions using non sea level measurements 1 we present a new method for reconstructing sea level involving cyclostationary empirical orthogonal functions cseofs while we show results from a cseof reconstruction using basis functions computed from satellite altimetry and subsequently fit to tide gauge data our focus is on how other ocean observations such as sea surface temperature can be leveraged to create an improved reconstructed sea level data set spanning the time period from 1900 to present basis functions are computed using satellite measurements of sea surface temperature and using a simple regression technique these basis functions are transformed to represent a similar temporal evolution to corresponding satellite altimeter derived sea level basis functions the resulting sea level and sea surface temperature basis functions are fit to tide gauge data and historical sea surface temperature data respectively to produce a reconstructed sea level data set spanning the period from 1900 to present we demonstrate the use of this reconstructed data set for climate monitoring focusing primarily on climate signals in the pacific ocean the cseof reconstruction technique can be used to create indices computed solely from sea level measurements for monitoring signals such as the eastern pacific ep el nino southern oscillation enso central pacific cp enso and pacific decadal oscillation pdo the ep enso cp enso and pdo signals are all well represented in the cseof reconstruction relying solely on sea level measurements from 1950 to present however significant improvement can be made in reconstructing these signals during the first half of the twentieth century by including sea surface temperature measurements in the sea level reconstruction procedure

geochemistry of banded iron formation of orissa india major and trace element analyses of representative samples of various types of banded iron formation and its various minerals associated sediments iron ores and volcanic tuff from different localities of orissa india are presented in this paper the orissa banded iron formation is classified as precambrian banded iron formation and is similar to the oxide facies iron formation of lake superior type the orissa iron formation consists only of iron oxide and silica with total absence of iron silicate sulfide and carbonate minerals and is devoid of terrigenous material the trace element content suggests the source of the underlying quartzite to be a continental igneous rock mass while the interbedded tuff are of undoubted volcanic origin the overlying iron formation were chemically precipitated as oxidate sediments in which the principal iron mineral magnetite was formed at low temperature in a shallow marine environment from the overwhelming similarity of major and trace element contents of all the samples from the different localities it is postulated that these detached outcrops originated in the same continous basin

alumina rich rocks from the early precambrian of the kaapvaal craton as indicators of paleosols and as products of other decompositional reactions within early archaean to early proterozoic pelites and volcanics of the kaapvaal craton rocks with above 20 al2o3 are widely distributed the alumina rich nature of these rocks is ascribed to decompositional reactions during which up to about 60 of the original material was leached out of the source rock and removed in solution many of these rocks also show diagenetic enrichment in k2o of up to 10 the decomposition reactions in many cases affected the source rocks without disturbing fine structures such as perlitic devitrification cracks in volcanic glass granules the origin of the majority of these rocks can be ascribed to decomposition during subaerial weathering they represent paleosols for other occurrences the stratigraphic context rules out an explanation as paleosols the origin of this type is ascribed to subaqueous decomposition of lavas or tuffs assisted by hydrothermal exhalations it is shown that alumina rich rocks in greenschist belts almost exclusively formed subaqueously whereas the younger occurrences mostly are of weathering origin geotectonic differences are invoked to explain this contrast rocks of similar chemical composition are described from the canadian shield zimbabwe western australia india and the baltic shield they illustrate that the preservation potential of these rocks is high only the study of the stratigraphic context will allow a conclusion on whether a particular occurrence is the product of weathering or subaqueous decomposition

a note on the representation of steric sea level in models that conserve volume rather than mass this note discusses the representation of steric sea level in ocean circulation models changes in steric sea level are caused when changes in the density of the water column imply an expansion or contraction of the column models usually make the boussinesq approximation and conserve volume rather than mass and so do not properly represent expansion or contraction this means that although expansion contraction is included in the equation of state it is not accounted for by the model dynamics in this note we examine the equation governing the time evolution of the sea level displacement it is shown that requiring conservation of mass rather than volume introduces a new term to this equation a simple example is used to show the relationship of the new term to the surface buoyancy flux the equilibrium response to the new term has two parts one part consists of the goldsbrough and stommel gyres for which in the ocean interior vortex stretching due to the local expansion contraction of the water column is balanced by changes in planetary vorticity the other part corresponds to the inverse barometer the effect is to adjust sea level by a globally uniform but timevarying factor determined by the net expansion contraction of the global ocean since this correction is globally uniform it has no dynamical significance both the goldsbrough stommel gyres and the inverse barometer solution are missing from models as currently formulated this does not represent a serious error however if comparison is made with observations of sea level model calculated sea level should be adjusted by a globally uniform time varying factor determined by the net expansion contraction of the global ocean this would be important for assessing the likely rise in sea level in response to global warming

dynamical suppression of sea level rise along the pacific coast of north america indications for imminent acceleration 1 long term changes in global mean sea level msl rise have important practical implications for shoreline and beach erosion coastal wetlands inundation storm surge flooding and coastal development altimetry since 1993 indicates that global msl rise has increased about 50 above the 20th century rise rate from 2 to 3 mm yr 1 at the same time both tide gauge measurements and altimetry indicate virtually no increase along the pacific coast of north america during the satellite epoch here we show that the dynamical steric response of north pacific eastern boundary ocean circulation to a dramatic change in wind stress curl xy which occurred after the mid 1970s regime shift can account for the suppression of regional sea level rise along this coast since 1980 alarmingly mean xy over the north pacific recently reached levels not observed since before the mid 1970s regime shift this change in wind stress patterns may be foreshadowing a pacific decadal oscillation regime shift causing an associated persistent change in basin scale xy that may result in a concomitant resumption of sea level rise along the u s west coast to global or even higher rates

ocean beach tasmania a swell dominated shoreline reaches climate induced recessional tipping point global sea level rise since the nineteenth century is expected to eventually cause recession of many shores however most swell exposed sandy beaches have not yet shown such response this study analysed a 70 year air photo and beach profile record for swell dominated ocean beach western tasmania to show an abrupt change of long term shoreline position variability circa 1980 from episodic erosion and accretion since at least 1947 to persistent recession with no recovery up to the present dating of back dune peats exposed in the dune scarp showed that recent shoreline recession exceeds any in the last 1800 years investigation of potential causes identified recent onset sea level rise slr on a tectonically stable coast and increasing winds driving increased wave setup as drivers with sufficient explanatory power to account for the observed changes although data limitations and residual uncertainties mean additional contributing factors such as interdecadal wave direction changes cannot be ruled out we hypothesise that ocean beach has experienced earlier recession in response to slr and other climate change effects than many other beaches owing to exposure to a very high energy stormdominated wave climate littoral drift efficiently delivering eroded sand to a large capacity active sand sink and low variability in swell wave directions and inter annual sea levels we hypothesise that sea level rise with higher onshore wind speeds generating increased wave setup at ocean beach since before the 1980s has increased upper beach erosion event frequency until the formerly stable or gaining sand budget reversed to deficit a major storm or storm cluster abruptly tipped the beach into its current recessional mode when its sand budget was close to deficit factors causing an early shoreline response to sea level rise at this site are applicable more widely as potential indicators of beaches likely to respond earlier than others to climate induced changes including not only slr but also wind climate changes

late caradoc graptolitic faunal gradients across the iapetus ocean late caradoc graptolite assemblages across the iapetus ocean in wales and scotland became progressively more disparate despite the narrowing of the ocean we compare faunal distributions in continuous sections from opposite sides of iapetus at whitland in south wales and hartfell score in the southern uplands of scotland a comprehensive graptolite range chart is given for each the graptolite assemblages from the clingani biozone are subdivided into a lower ensigraptus caudatus subzone and upper dicellograptus morrisi subzone at both localities though the faunas differ in detail higher in the sequence the distinctive scottish linearis biozone fauna is not recognizable at whitland its presumed equivalent being a fauna dominated by variable morphotypes of the genus normalograptus this suggests that environmental gradients depth and or temperature were changing more rapidly than the geography significantly the subsequent inception of limestone deposition at whitland was approximately contemporaneous with widespread replacement of black mudstones by oxic bioturbated sediments elsewhere in the welsh basin and in scotland this was possibly a response to an early phase of cooling prior to the end ordovician glaciation in wales the claimed hiatus at the caradoc ashgill boundary may rather reflect biofacies variation

experiments in reconstructing twentieth century sea levels abstract one approach to reconstructing historical sea level from the relatively sparse tide gauge network is to employ empirical orthogonal functions eofs as interpolatory spatial basis functions the eofs are determined from independent global data generally sea surface heights from either satellite altimetry or a numerical ocean model the problem is revisited here for sea level since 1900 a new approach to handling the tide gauge datum problem by direct solution offers possible advantages over the method of integrating sea level differences with the potential of eventually adjusting datums into the global terrestrial reference frame the resulting time series of global mean sea levels appears fairly insensitive to the adopted set of eofs in contrast charts of regional sea level anomalies and trends are very sensitive to the adopted set of eofs especially for the sparser network of gauges in the early 20th century the reconstructions appear especially suspect before 1950 in the tropical pacific while this limits some applications of the sea level reconstructions the sensitivity does appear adequately captured by formal uncertainties all our solutions show regional trends over the past five decades to be fairly uniform throughout the global ocean in contrast to trends observed over the shorter altimeter era consistent with several previous estimates the global sea level rise since 1900 is 1 70 0 26 mm yr 1 the global trend since 1995 exceeds 3 mm yr 1 which is consistent with altimeter measurements but this large trend was possibly also reached between 1935 and 1950

regional sea level variability and trends 1960 2007 a comparison of sea level reconstructions and ocean syntheses several existing statistical and dynamical reconstructions of past regional sea level variability and trends are compared with each other and with tide gauges over the 48 yr period 1960 2007 partially pre dating the satellite altimetry era evaluated statistical reconstructions were built from tide gauge data tgr and dynamical reconstructions from ocean data assimilation oda approaches although most of the tgrs yield global mean time series of sea level with trends deviating within only 0 1 mm yr 1 the spatial anomalies of the trends deviate substantially between the reconstructions over the period predating altimetry in contrast tgrs match observed regional trend patterns fairly well during the satellite altimetry era tgrs match tide gauge data better than oda results however they exhibit less variability in the open ocean compared to altimetric data over the pre altimetry period all reconstructed regional sea level trend patterns deviate substantially from each other in terms of detrended correlations in this earlier period the reconstructions match tide gauges and each other much better in the pacific than in the atlantic an ensemble of all tgr and oda estimates provides some improvements in correlations and trends to both tide gauges and altimetry nevertheless a lack of independent open ocean sea surface height data predating altimetry makes impossible the validation of the ensemble for pre altimetry open ocean sea level trends and variability estimating regional sea level changes prior to altimetry therefore remains an unsolved challenge

geochemical evolution of archean shales from south africa i the swaziland and pongola supergroups abstract the fig tree group and moodies group part of the swaziland supergroup are exposed in the barberton mountain land and are 3 3 3 5 ga old shales from the fig tree group are characterized by variable rare earth element ree patterns with lan ybn 5 5 1 8 95 confidence and eu eu 0 97 0 18 shales from the moodies group have more fractionated ree patterns lan ybn 8 7 2 0 and less variable eu anomalies eu eu 0 92 0 02 both groups are characterized by very high abundances of cr and ni modelling of those trace elements which are relatively unfractionated during sedimentary processes ree th sc is consistent with the derivation of these sedimentary rocks from a mixture of the archean bimodal igneous suite mafic volcanics tonalites trondhjemites felsic volcanics with the moodies group requiring a larger percentage of the felsic end member the data for shales from the swaziland supergroup support models suggesting that the archean exposed crust was of more mafic composition than the post archean upper crust and that intracrustal melting was relatively unimportant in differentiating the archean crust the pongola supergroup is younger than the swaziland supergroup but older than 2 9 ga shales and mudstones from the nsuze and mozaan groups show ree characteristics intermediate between the older shales of the swaziland supergroup and typical post archean shales one quartzite sample from the witwatersrand supergroup ca 2 6 ga has a ree pattern virtually parallel to average post archean shales but with much lower abundances the change from typical archean to post archean sedimentary trace element patterns has been documented in early proterozoic successions from canada and australia this change has been related to a short interval of intense growth and chemical differentiation of the continental crust during the late archean 2 7 2 5 ga in southern africa this change appears to have taken place much earlier 3 2 2 9 ga but can be related to similar processes thus the period of crustal evolution related to the archean proterozoic boundary while virtually episodic regionally occurred over a protracted period world wide during the period ca 3 2 2 5 ga

early archean silicate spherules of probable impact origin south africa and western australia layers of sand sized silicate spherules in 3 2 to 3 5 ga archean greenstone belts in south africa and western australia formed by the accumulation of quenched liquid silicate droplets having primary compositions resembling those of immediately underlying rock sequences the layers and particles appear to be unrelated to volcanic activity and we suggest that both occurrences may represent melt droplets formed during meteorite or comet impacts if so these spherules are the oldest known terrestrial impact products if these objects are representative of a larger population of early archean impact features it may be possible to directly estimate the meteorite flux on the early archean earth

reappraisal of a 2200 ma old paleosol near waterval onder south africa abstract a fossil soil paleosol about 2200 ma old in a deep roadcut between the towns of waterval boven and waterval onder transvaal here called the waterval onder clay paleosol was formerly reported to have formed on the hekpoort basalt it is here thought to have developed on a thick formerly at least 5 5 m upward fining and thinning sequence of sandstone siltstone and shale derived from pre existing soils on hekpoort basalt within the basal portion of the fluvial dwaal heuvel formation in contrast to paleosols developed on hekpoort basalt the waterval onder clay paleosol is little deformed lacks corestones and shows compositional variation and berthierine rich laminae interpreted as relict bedding the paleosol has a ridge and swale topography linear or wavy gilgai and a subsurface structure mukkara typical of modern vertisols since there is considerable relict bedding it probably formed over a short period of time less than 7000 years and was not self plowing to the extent seen in modern vertisols clastic dikes filled with sandstone from the overlying rocks are evidence that the profile was periodically dry to depths of at least 2 m more drab colored rocks below that may represent the level of permanent water table iron and manganese stain of layers and claystone granules within the surface horizon of the profile have some characteristics of modern rock varnish and could be taken as evidence for life in the soil the high ratio of ferric to ferrous iron near the surface of the paleosol together with evidence from clastic dikes that this horizon was not waterlogged is an indication of an oxidizing atmosphere although probably one in which oxygen was much less abundant than it is today the very low amounts of acid titratable bases in the shaly parent material of this paleosol and surficial loss of these bases within the paleosol appear to have been produced by decarbonation reactions comparable to those found today in soils of vascular land plants a likely source of weathering acid during the precambrian is an elevated abundance of atmospheric carbon dioxide considering these likely atmospheric differences together with the distribution of comparable modern vertisols and other geological evidence the climate under which this soil formed was probably semiarid to subhumid seasonally dry and temperate

a reassessment of facies and faunas in the type llandeilo ordovician wales abstract detailed analysis of the lithological and faunal successions of the type llandeilo forms the basis of an evaluation of the sequence of depositional environments and a quantitative description of the entombed faunas comprising mainly brachiopods trilobites and ostracods recorded distribution patterns confirm the validity of the existing trilobite trinucleid biostratigraphic zones but emphasize the importance of benthic bivalved taxa which are particularly abundant in the lower llandeilo groups of assemblages comprising localized faunules or associations despite exhibiting evidence of transportation are readily identified as representative of more widespread contemporary palaeocommunities recently described from wales and the welsh borderland the relationship between these palaeocommunities and the transgressive llandeilo sequence indicates a shoreface to open shelf zonation of ecosystems controlled primarily by substrate conditions rather than depth

a palaeomagnetic study of the builth wells llandrindod wells ordovician inlier wales palaeogeographic and structural implications summary discrepancies exist in the southern british ordovician palaeomagnetic data set with individual studies indicating either high southerly or temperate southerly palaeolatitudes although previous palaeomagnetic investigations from the builth inlier have delineated a three component remanence structure doubts have been raised concerning i the magnetization age of the supposed primary component p ii the structural setting of the sampling area llanelwedd quarry within a zone of strike slip deformation and iii whether detailed step wise demagnetization has fully separated the various magnetization components in addressing these problems we present new palaeomagnetic results as follows i a positive palaeomagnetic conglomerate test establishing a pre late llanvirn age for component p ii an enlarged geographic sampling embracing several tectonic domains indicating that relative rotations linked to strike slip tectonism are minor within the builth sampling area and iii evidence that component p is uncontaminated by overprints at some sites suggesting the resulting palaeolatitude of 35 s to be representative for the builth inlier we also present evidence for local syn volcanic deformation within llanvirn volcanics and for intrusion related deformation of llanvirn shales when the revised llanvirn pole from the inlier 3 s 4 e is combined with other data from southern britain in a statistical spline analysis a mean palaeolatitude of 44 5 s is calculated for builth in llanvirn times a palaeoreconstruction for 468 474 ma c mid llanvirn is presented utilizing this analysis

metamorphic alteration of a precambrian 2 2 ga paleosol from south africa revealed by backscattered electron imaging abstract like many precambrian paleosols the 2200 ma old waterval onder clay has been metamorphosed to the greenschist facies of regional metamorphism the extent of metamorphic alteration of the fine grained uppermost horizons of the paleosol is assessed here using optical and backscattered electron microscopy in hand specimens and under low power optical examination the paleosol shows surficial lamination cumulic horizon of soil terminology rounded clasts coated with opaque sesquioxides manganoferriargillans cracks defining a fitted breccia of blocks that were evidently soft in places blocky angular peds cracks filled with multiple generations of material from above illuviation argillans and zones of unusually highly birefringent clay climobimasepic plasmic fabric with backscattered electron microscopy however at a resolution of less than about 10 m the fine structure of originally colloidal parts of the paleosol mangans argillans matrix and plasma separations is shown to be extensively recrystallized to illite and berthierine original soil structure has been obscured at this resolution by crystal growth at random across original microscopic discontinuities preferred orientation of metamorphic crystals can still be seen along what are presumed to be highly birefringent zones of oriented clay similar to those in modern soils but the matrix itself shows random clusters of crystals suggestive of an advanced stage of illitization by ostwald ripening the style of recrystallization of laminae in the surface horizon is similar to that seen lower in the profile where recrystallized beds are thicker and coarser grained thus the paleosol probably formed on an upward thinning and fining sequence of sandstone and shale rather than on basalt on this assumption the profile has gained iron compared with its shaly parent material rather than lost iron compared with basalt this may be an indication of greater oxygenation of the atmosphere than previously thought possible microbial traces can be seen in thin section but because of pervasive recrystallization these remain dubiofossils

annual sea level changes on the north american northeast coast influence of local winds and barotropic motions abstractunderstanding the relationship between coastal sea level and the variable ocean circulation is crucial for interpreting tide gauge records and projecting sea level rise in this study annual sea level records adjusted for the inverted barometer effect from tide gauges along the north american northeast coast over 1980 2010 are compared to a set of data assimilating ocean reanalysis products as well as a global barotropic model solution forced with wind stress and barometric pressure correspondence between models and data depends strongly on model and location at sites north of cape hatteras the barotropic model shows as much if not more skill than ocean reanalyses explaining about 50 of the variance in the adjusted annual tide gauge sea level records additional numerical experiments show that annual sea level changes along this coast from the barotropic model are driven by local wind stress over the continental shelf and slope this result is interpreted in the light of a simple dynamic

premetamorphic lateritisation in proterozoic metabasites of rogaland sw norway heterogeneous layers of granulite facies metamorphic basites of the proterozoic supracrustal faurefjell formation in rogaland s w norway display an extreme chemical variation within a single layer the bulk chemical composition gradually changes from approximately basaltic in basic granulites to alumina iron rich in granofelses component ratios and composition volume relations indicate open system chemical reactions mainly involving the extraction of silica apparent enrichment in fe ti p al zr ni co zn y nb hf and ree and variations in resulting metamorphic mineral assemblages are related to premetamorphic progressive lateritisation of a basaltic protolith the weathering generated a continuous chemical suite from sio2 48 wt fe2o3 10 wt and al2o3 19 wt in the basic granulites to 14 wt 40 wt and 25 wt in the fe al granofelses metasomatism during diagenesis and during very high grade metamorphism 1200 900 ma further perturbed the concentrations of relatively mobile elements ca mg k rb sr ba na and li in the laterites without affecting the transition metal ratios in particular the ree did not fractionate differentially during the supracrustal and metasomatic alteration

high resolution correlation of anglo welsh middle to upper ordovician sequences and its relevance to international chronostratigraphy abstract continuously fossiliferous sections in south wales and shropshire spanning the base of the upper ordovician permit precise correlation of the nemagraptus gracilis biozone a horizon currently under scrutiny for the selection of a global stratotype section and point gssp using graphic correlation we have compiled a new composite global standard for the middle upper ordovician which shows that the first occurrence of the key graptolite n gracilis is not everywhere of the same age appearing earlier in north american successions than it does in britain species of dicellograptus by contrast appear to be almost synchronous in their first appearance the status and correlation of standard british biozones through the llandeilian caradoc interval based on graptolites and trilobites are revised suitable sections for the definition of bases of biozones are proposed if the base of the n gracilis biozone is accepted internationally as the base of the upper ordovician this biozone being coincident with the base of the caradoc series there are sections suitable for its precise definition in the british succession

a vertic paleosol at the archean proterozoic contact from the singhbhum orissa craton eastern india abstract we report on an inferred paleoproterozoic soil horizon from the singhbhum orissa craton near keonjhargarh orissa eastern india which preserves vertic vertisol like features the 2 10 m thick white shale consists of quartz muscovite pyrophyllite interpreted as a paleosol overlies 3 32 ga granite and is covered by pre 2 0 ga sandstones kolhan group deposited in marginal marine environments the paleosol passes downwards through a partly altered granite saprolith zone to fresh granite abundant pedogenic slickensides ped structures gilgai topography reddish stain on ped surfaces and sepic plasmic microfabric in the paleosol were probably related to shrink and swell processes driven by marked seasonal precipitation in a well drained landscape an observed decrease of alkali elements and an increase of silica alumina and cia values from granite to paleosol together with relatively constant ti al ratios suggest in situ weathering of granite protolith however a paleo vertisol necessitates a mafic parent rock either directly igneous or reworked through alluvium the c 2 25 ga malangtoli jagannathpur basaltic rocks are relatively widespread and close to the inferred paleosol occurrences and provide a logical solution geochemistry of the highly depleted paleosol in contrast particularly when applying the isochon method strongly supports a granitic parent the apparent conundrum can possibly be solved through repeated alluvial reworking of both granitic and mafic detritus and accumulation of weathered material with varying proportions of these two components yet enough smectitic clays 30 to form a paleo vertisol this pre 2 0 ga weathering event in the singhbhum craton is consistent with a global scenario of paleoproterozoic weathering which followed an extended global glaciation and thus has the potential to contribute to understanding of pre 2 0 ga amalgamation of regional and global cratonic blocks

deep ocean warming assessed from altimeters gravity recovery and climate experiment in situ measurements and a non boussinesq ocean general circulation model 1 observational surveys have shown significant oceanic bottom water warming but they are too spatially and temporally sporadic to quantify the deep ocean contribution to the present day sea level rise slr in this study altimetry sea surface height ssh gravity recovery and climate experiment grace ocean mass and in situ upper ocean 0 700 m steric height have been assessed for their seasonal variability and trend maps it is shown that neither the global mean nor the regional trends of altimetry slr can be explained by the upper ocean steric height plus the grace ocean mass a non boussinesq ocean general circulation model ogcm allowing the sea level to rise as a direct response to the heat added into the ocean is then used to diagnose the deep ocean steric height constrained by sea surface temperature data and the top of atmosphere toa radiation measurements the model reproduces the observed upper ocean heat content well combining the modeled deep ocean steric height with observational upper ocean data gives the full depth steric height adding a grace estimated mass trend the data model combination explains not only the altimetry global mean slr but also its regional trends fairly well the deep ocean warming is mostly prevalent in the atlantic and indian oceans and along the antarctic circumpolar current suggesting a strong relation to the oceanic circulation and dynamics its comparison with available bottom water measurements shows reasonably good agreement indicating that deep ocean warming below 700 m might have contributed 1 1 mm yr to the global mean slr or one third of the altimeter observed rate of 3 11 0 6 mm yr over 1993 2008

reconstructing sea level using cyclostationary empirical orthogonal functions 1 cyclostationary empirical orthogonal functions derived from satellite altimetry are combined with historical sea level measurements from tide gauges to reconstruct sea level fields from 1950 through 2009 previous sea level reconstructions have utilized empirical orthogonal functions as basis functions but by using cyclostationary empirical orthogonal functions and by addressing other aspects of the reconstruction procedure an alternative sea level reconstruction can be computed the procedure introduced here is capable of capturing the annual cycle and el nino southern oscillation enso signals back to 1950 with correlations between the reconstructed enso signal and common enso indices found to be over 0 9 the regional trends computed from the new reconstruction show good agreement with the trends obtained from the satellite altimetry but some discrepancies are seen when comparing with previous sea level reconstructions over longer time periods the computed rate of global mean sea level rise from the reconstructed time series is 1 97 mm yr from 1950 to 2009 and 3 22 mm yr from 1993 to 2009

description and ecology of a new middle ordovician llanvirn odontopleurid trilobite from the builth inlier of mid wales with a review of the genus meadowtownella a new odontopleurid trilobite meadowtownella serrata is described from a new llanvirnian darriwilian didymograptus murchisoni biozone locality in the builth inlier mid wales this unusually spinose species displays a remarkable array of pygidial spines and extends the stratigraphic range of the genus back into the abereiddian benthic faunas are rare in the predominantly anoxic d murchisoni biozone of the welsh basin and these beds are an unusual habitat for odontopleurids environmental analyses framboidal pyrite and associated total organic carbon in this study together with the distribution of benthic faunas described and figured in the section indicate a likely oxic water column and episodically oxic bottom waters a new diagnosis for meadowtownella is presented with a review of the genus as a clarification of previous work the greater spinosity of earlier members of the lineage may reflect either changing environmental preferences or the derivation of meadowtownella from an original more spinose lineage

a paleoproterozoic paleosol horizon in the lesser himalaya and its regional implications abstract a paleoproterozoic paleosol horizon in the himachal himalaya along a basement cover contact is identified on the basis of an integrated field petrographic geochemical studies the paleosol horizon is exposed in a road section along the sutlej river near karcham it is represented by a 2 5 m thick sericite schist unit along the contact of the 1866 10 ma jeori wangtu bandal gneissic complex jwbgc and the overlying sericite quartzite of the manikaran formation rampur group which is interstratified with 1800 13 ma tholeiitic flows in its basal part the geochemical studies reveal a sharp drop in the concentration of sio2 fe2o3 mgo cao na2o and a rise in concentration of al2o3 tio2 k2o and p2o5 at the contact of granite gneiss and sericite schist ree plots of granite gneiss sericite schist and quartzite samples of the manikaran formation display similarity of pattern fractionation between the lree and hree and comparable negative eu anomaly the total ree of the sericite schist and sericitic quartzite is lower than those of the granite gneiss based on these studies the sericite schist is inferred to be a metamorphosed alumina rich soil which appears to have formed in a warm and humid climate in a waterlogged terrain of gentle relief and is post 1866 ma and pre 1800 ma in age apparent gradation from the strongly deformed amphibolite facies jwbc to the sericite schist with diffused contact indicates that the jwbgc was already metamorphosed and deformed prior to the development of the paleosol thereafter both together with the overlying manikaran formation were subjected to low grade metamorphism during the himalayan orogeny the jwbc is involved in the crystalline thrust sheet and is present throughout the length of the himalaya thus it is inferred that the paleoproterozoic metamorphism was a regional event in the himalaya at a time when the indian plate was part of the nuna supercontinent

the proterozoic thelon paleosol northwest territories canada abstract beneath the 1 72 ga thelon formation in the northwestern part of the canadian shield an unmetamorphosed and undeformed paleosol is preserved on a variety of paleoproterozoic and archean protoliths this paper documents the paleosol referred to as the thelon paleosol in four localities where it developed on leucocratic schist gneiss and granite the thelon paleosol is characterized by these ascending changes from fresh protolith through paleosol to the unconformity a saprolitic disruption of the protolith resulting in ped and ferran formation b reddening of the paleosol as a consequence of hematitization c increase in dissolution of feldspar plagioclase alkali feldspar increase in the degree of iron oxidation in biotite chlorite and garnet and an increase in the abundance of neoform kaolinite illite and hematite cement d a loss of tio2 fe2o3 total feo mno mgo cao na2o k2o p2o5 u zr rb sr ba e a gain of fe2o3 and f an increase in cia values the fabric of the parent material appears to be the only soil forming factor that locally influenced paleosol development in comparison to thin profiles developed on massive relatively impervious protoliths thick profiles have developed on metamorphic protoliths in which the fabric has allowed deeper penetration of paleoweathering fluids the behaviour of iron in the profiles particularly profile 2 with a granite protolith and an increase in hematite towards the top of the profiles suggests that the thelon paleosol formed under an oxidizing atmosphere subsequent deposition of quartzose conglomerate and sandstone of the thelon formation has caused compaction of the thelon paleosol and this compaction probably was responsible for the formation of stylocumulates in the paleosol during diagenesis of the thelon formation the influx of diagenetic fluids into the paleosol produced veinlets of quartz and hematite a newly recognized microcrystalline hydrated alumino phosphate sulphate mineral and widespread pseudomorphs of illite after pedogenic vermiform kaolinite

archean chemical weathering at three localities on the canadian shield abstract sapropelite developed on a granodiorite basement below the archean steeprock group in the western superior structural province of canada weathered materials from a 3 15 ga granitic basement to the archean yellowknife supergroup in the slave structural province and weathered detritus from contemporaneous komatiites and gneissic basement of the archean prince albert group in northern churchill structural province have been analysed the deviation of the weakly metamorphosed weathered material from the chemical composition of their precursors is comparable to that seen in more recent weathered profiles from similar source materials this includes the enhancement of ferric to ferrous iron ratios and potash to soda lime and magnesia ratios there is also an increase in lighter ree and a depletion of heavier ree quartz rich sediments immediately above the unconformity derived from the basement granitoids may be enriched in aluminum and iron and yield chloritoid under proper metamorphic conditions sediments formed from mixed sources such as weathered gneissic basement and contemporaneous komatiitic volcanics yield anomalous resistate sedimentary mixtures such as chromiferous quartzites based on the data given here there is no need to postulate that different weathering and or ground water systems were operative during the archean compared to more recent times on the other hand the complicated weathering and diagenetic history that altered material undergoes below a subsiding unconformity relies as much or more on the buffering capacity of the enclosed rock mass as on the atmospheric conditions prevalent at the time of weathering hence weathering profiles old and new are more a response to local environmental conditions within the rock than the composition of the atmosphere

regional biases in absolute sea level estimates from tide gauge data due to residual unmodeled vertical land movement the only vertical land movement signal routinely corrected for when estimating absolute sea level change from tide gauge data is that due to glacial isostatic adjustment gia we compare modeled gia uplift ice 5g vm2 with vertical land movement at 300 gps stations located near to a global set of tide gauges and find regionally coherent differences of commonly 0 5 2 mm yr reference frame differences and signal due to present day mass trends cannot reconcile these differences we examine sensitivity to the gia earth model by fitting to a subset of the gps velocities and find substantial regional sensitivity but no single earth model is able to reduce the disagreement in all regions we suggest errors in ice history and neglected lateral earth structure dominate model data differences and urge caution in the use of modeled gia uplift alone when interpreting regional and global scale absolute geocentric sea level from tide gauge data

sea level on the u s east coast decadal variability caused by open ocean wind curl forcing one of the puzzling features of sea level on the east coast of the united states is the decedal scale variability the fluctuations are 10 15 cm peak to peak at periods longer than a few years the authors find that this variability in the frequency band treated with the model is largely caused by a deep sea signal generated by the wind stress curl over the north atlantic a simple forced long rossby wave model of the response of the thermocline to wind forcing is used computing long wave speeds from observed hydrographic data the authors model the response of the ocean at periods longer than 3 years for the full width of the atlantic and for the north south extent of the main anticyclonic gyre 188 388n the model output in deep water shows remarkably good agreement with tide gauges both at bermuda 328n and puerto rico 188n as well as with dynamic height fluctuations of 20 cm peak to peak once these fluctuations reach the western side of the ocean the authors estimate coastal sea level by constructing a complementary coastal model the coastal model is geostrophic and conserves mass within a nearshore region that encompasses the gulf stream by extending this nearshore region as far south as 148 188n and using only the oceanic fluctuations to force the variability in the stream between 80 and 90 of the variance of sea level at coastal tide gauges can be explained sea level along the coast is used to test the model assumptions the basic results however seem important because they are constrained only by open ocean wind forcing and not by input boundary conditions

estimates of the regional distribution of sea level rise over the 1950 2000 period abstract topex poseidon satellite altimeter data are used to estimate global empirical orthogonal functions that are then combined with historical tide gauge data to estimate monthly distributions of large scale sea level variability and change over the period 1950 2000 the reconstruction is an attempt to narrow the current broad range of sea level rise estimates to identify any pattern of regional sea level rise and to determine any variation in the rate of sea level rise over the 51 yr period the computed rate of global averaged sea level rise from the reconstructed monthly time series is 1 8 0 3 mm yr 1 with the decadal variability in the computed global mean sea level it is not possible to detect a significant increase in the rate of sea level rise over the period 1950 2000 a regional pattern of sea level rise is identified the maximum sea level rise is in the eastern off equatorial pacific and there is a minimum along the equator in the western pacific and in the eastern indian ocean a g

a polygenetic palaeosol from the silurian wenlock of southwest ireland a problematic palaeosol unit caps a thick basalt at the top of the clogher head formation dunquin group late wenlock silurian in the dingle peninsula southwest ireland the main part of the unit consists of an altered calc alkaline basalt with a fine clay assemblage of chlorite corrensite and smectite probably resulting from weathering during wenlock times the uppermost part of the unit consists of detrital silicates which were admixed by bioturbation and well defined burrow fills are present the underlying weathered basalt was possibly truncated before the detrital horizon was deposited and finally the whole unit underwent a phase of surface water gleying a catenary relationship existed locally with the pseudo gley developed lower in the landscape while contemporaneous basalts in topographically higher better drained areas largely escaped the effects of gleying these now exhibit reddened tops the complex history and the possiblity of the incompleteness of the profile makes accurate assessment of the soil climate function difficult however the occurrence of calcrete bearing palaeosols in the overlying mill cove formation supports the view that the basalt was weathered under a sub humid or semi arid climate considering the alteration of the dunquin group to actinolite prehnite grade the preservation of the smectite is highly unusual there is no evidence for its origin due to more recent weathering or interstratal neoformation it is thus interpreted as a relict product of the original weathering phase

geology of precambrian paleosols at the base of the huronian supergroup elliot lake ontario canada abstract detailed examination of two new profiles through the denison series paleosol and one new profile through a pronto series paleosol in the elliot lake area lend fresh insight into atmospheric and hydrogeologic environmental conditions of precambrian earth these are reassessed with reference to the results of previous studies as true indigenous paleosols of polygenetic character virtually all of the criteria grandstaff et al 1986 for identification of paleosols are met the paleosols bear strong mineralogical and chemical similarities despite derivation from different parent materials and sampling at locations distant from each other there has evidently been a common reaction to weathering processes peculiar to the early proterozoic diagenetic and metamorphic events mask to a considerable extent the role played by environmental and hydrologic conditions in the development of the paleosols in the denison greenstone derived paleosol clay formed from amphibole feldspar and chlorite is altered to sericite increased quartz content is due to residual concentration and to secondary development in granodiorite derived paleosol quartz and sericite are generally more abundant quartz is relatively concentrated toward the top of the profile the paleosols are thus primarily sericite quartz and chlorite assemblages rutile and leucoxene are accessory minerals profiles of elemental chemistry show the most drastic changes in concentration at the base in transition to bedrock magnesia and lime are leached from all profiles as in modern soils although in common with most precambrian paleosols potash accumulated total fe is strongly depleted from the profiles except just above the bedrock contact with granodiorite a condition attributed to mobilization of fe from the paleosol to a position directly over relatively impermeable parent rock use of holland s method of establishing oxygenation from paleosols indicates that in terms of fe content parent material of granodiorite derived paleosol should produce a reduced fe paleosol the oxygen demand of this rock was greater than granite owing to an abundant ferromagnesian content two fossil eluvial horizons marked by high chlorite and a dramatic decrease in sericite content are recognized in the denison paleosol their existence shows that although initial stages of weathering may have occurred under water saturated conditions conditions were probably more arid than supposed by previous workers particularly during the later stages of development of the paleosol although fe enriched the eluvial horizons are drastically depleted in potash al and th removal of al 2 o 3 negates normalization of chemical analyses of paleosols to al 2 o 3 for purposes of constant volume calculations th associated with sericite in the profiles increases at the contact with the overlying matinenda formation in association with rutile and leucoxene owing to interaction with diagenetic u bearing fluids from overlying sediments rutile and leucoxene originate from parent rocks and are a late stage form of mineralization these titaniferous phases indirectly contributed to the local dominance of brannerite type orc through diagenetic processes of mineralization involving the pronto reaction paleotopographic greenstone highs are related to local anomalously high concentrations of heavy minerals in the brannerite rich orc this involves hydraulic deposition of heavy minerals in the lee of crescent shaped greenstone highs with subsequent diagenetic upgrading granodiorite derived paleosol contains 5 10 times more au than the denison paleosol and is modestly enriched above background a slight decrease in au content upward evident in all profiles is an artefact of erosion of the top of the paleosols

global glacial isostasy and the surface of the ice age earth the ice 5g vm2 model and grace abstract the 100 kyr quasiperiodic variation of continental ice cover which has been a persistent feature of climate system evolution throughout the most recent 900 kyr of earth history has occurred as a consequence of changes in the seasonal insolation regime forced by the influence of gravitational n body effects in the solar system on the geometry of earth s orbit around the sun the impacts of the changing surface ice load upon both earth s shape and gravitational field as well as upon sea level history have come to be measurable using a variety of geological and geophysical techniques these observations are invertible to obtain useful information on both the internal viscoelastic structure of the solid earth and on the detailed spatiotemporal characteristics of glaciation history this review focuses upon the most recent advances that have been achieved in each of these areas advances that have proven to be central to the construction of the refined model of the global process of glacial isos

an evaluation of subsidence rates and sea level variability in the northern gulf of mexico 1 while subsidence is widely recognized as a driver of geomorphic change in the northern gulf of mexico gom there is considerable disagreement over the rates of subsidence and the interpreted variability in these rates which leads to controversies over the impacts of subsidence on surface land area change here we present a new method to calculate subsidence rates from the tide gauge record that is based on an understanding of the meteorological drivers of inter annual sea level change in grand isle la and galveston tx we explicitly show that temporal patterns of subsidence are closely linked to subsurface fluid withdrawal and coastal land loss and suggest changes in withdrawal rates can both increase and decrease rates of subsidence and wetland loss our results also imply that the volume of sediment needed to rebuild gom wetlands may currently fall within the low end of some restoration scenarios

reconstruction of regional mean sea level anomalies from tide gauges using neural networks 1 the 20th century regional and global sea level variations are estimated based on long term tide gauge records for this the neural network technique is utilized that connects the coastal sea level with the regional and global mean via a nonlinear empirical relationship two major difficulties are overcome this way the vertical movement of tide gauges over time and the problem of what weighting function to choose for each individual tide gauge record neural networks are also used to fill data gaps in the tide gauge records which is a prerequisite for our analysis technique a suite of different gap filling strategies is tested which provides information about stability and variance of the results the global mean sea level for the period january 1900 to december 2006 is estimated to rise at a rate of 1 56 0 25 mm yr which is reasonably consistent with earlier estimates but we do not find significant acceleration the regional mean sea level of the single ocean basins show mixed long term behavior while most of the basins show a sea level rise of varying strength there is an indication for a mean sea level fall in the southern indian ocean also for the the tropical indian and the south atlantic no significant trend can be detected nevertheless the south atlantic as well as the tropical atlantic are the only basins that show significant acceleration on shorter timescales but longer than the annual cycle the basins sea level are dominated by oscillations with periods of about 50 75 years and of about 25 years consequently we find high lagged correlations between the single basins

pseudo oolites in rocks of the ulundi formation lower part of the archaean fig tree group south africa abstract the ulundi formation of the lowermost fig tree group in the type area in the barberton mountain land consists of a sequence of quartz sericite schists banded cherts and tuffaceous rocks up to 40 m thick it overlies talc carbonate schists assigned to the upper part of the onverwacht group in the cherts which in parts represent the sulfide facies of a banded iron formation silicified spheroids have been observed which appear to be diagenetically altered locally zeolitized accretionary lapilli portions of the cherts formed through silicification of fine grained felsic tuffs and contain abundant stylolite seams along which 4 of the rock thickness has been removed by intrastratal solution during deformation a supposedly organogenic spheroidal structure ramsaysphera has been previously described from the upper part of the ulundi formation the spheroids with diameters of up to 8 mm occur in a distinct bed of up to at least 1 6 m thickness and can be traced in outcrop over an area which originally covered 17 30 km the bed was deposited in fairly still water of several 100 m depth the spheroids accumulated with only little finer grained detrital material the interstices between them being filled by cherty silica and minor amounts of dolomite up to 65 of the spheroids consist of tectonically elongated originally round fragments of a micro felsitic groundmass with remnants of phenocrysts the majority of the remaining spheroids consists of concentrically banded bodies of siliceous material with minor amounts of chlorite and sericite as well as small dolomite crystals these spheroids represent highly altered granules of volcanic glass deposited from volcanic ash clouds through a body of water the prototype of ramsay sphera also belongs to this group of spheroids and there is little microscopic or macroscopic evidence for its explanation as an organic structure

evidence of tidal processes from the lower part of the witwatersrand supergroup south africa abstract a 1600 m succession of quartz arenites and associated shaley deposits comprising the hospital hill subgroup at the base of the witwatersrand supergroup is considered to have been deposited largely under the influence of tidal processes facies analysis indicates that deposition occurred in the following environments 1 marine shalf 2 shallow subtidal to intertidal 3 intertidal flat and 4 tidal inlet the presence of strong tidal currents implies that the witwatersrand basin was open to an ocean basin at least during the early stages of its evolution palaeocurrent trends and isopach data suggest that this probably lay to the southwest an area now occupied by the high grade natal namaqua metamorphic belt the contrast between the supermature quartz arenites of the hospital hill subgroup and the overlying gold bearing immature subgreywackes feldspathic quartzites and conglomerates of fluvial origin is believed to be a function of tidal reworking of sediments