magnetic fabrics of the miocene ignimbrites from west cameroon implications for pyroclastic flow source and sedimentation abstract the miocene ignimbrites of mounts bambouto and bamenda located in the central part of cameroon volcanic line are generally made of welded and non welded massive lapilli tuff and lithic breccias these discontinuous deposits cover a total area of 180 km 2 with thickness ranging from 25 to 200 m the different facies contain several lithic fragments of mainly trachytic nature the devitrified matrix of the welded ignimbrites is constituted by sanidine anorthoclase quartz plagioclase clinopyroxene biotite fe ti oxides and devitrified fiammes anisotropy of magnetic susceptibility ams is used to characterize magnetic fabrics and to provide an estimate of flow direction of each ignimbrite sheet magnetic mineralogy results from different flow units show that titanomagnetite titanohematite maghemite and goethite with grain size ranging from coarse md to very fine sp are the main magnetic carriers of these ignimbrites inferred transport directions based on the ams data and field indicators show that bambouto caldera is the source of main pyroclastic deposits of mount bambouto in southwestern mount bamenda santa mbu caldera or bambouto caldera constituted the probable emission center of mbengwi bamenda and mbu ignimbrite sheets whereas magnetic fabrics of bambili sabga and big babanki ignimbrites demonstrate that these deposits were emitted from a northeastern source namely oku vent in mount oku a small number of subvertical ams fabrics correspond to rocks possibly modified by an elutriation process

evaluation of paleomagnetism as a correlation criterion for mogollon datil ignimbrites southwestern new mexico paleomagnetic and rock magnetic data show that 36 24 ma ignimbrite outflow sheets in the mogollon datil volcanic field carry thermoremanent magnetizations trms that provide useful reliable correlation criteria over 90 of 404 ignimbrite sites exhibit well grouped 95 500 m intracaldera ignimbrite sequences agree in polarity with associated outflow sheets but show less consistent trm directions probably reflecting syncooling secular variation and discrepancies between eutaxitic foliations and the syncooling paleohorizontal mean virtual geomagnetic pole positions vgps of normal and reverse polarity ignimbrites are nearly antipodal 175 6 apart showing no evidence of long term differences in the zonal harmonics of the normal and reverse polarity states less antipodal mean vgps 161 2 apart from normal and reverse polarity lavas are interpreted as defects in the data set probably including incompletely removed normal polarity viscous overprints the mean paleomagnetic pole position for mogollon datil ignimbrites n 68 independent unit mean vgps is located at 78 8 n 166 6 e k 19 8 a95 4 0 18 2

quaternary history of the antarctic circumpolar current evidence from the scotia sea within the scotia sea the axis of the antarctic circumpolar current acc is geographically confined and sediments therefore contain a record of palaeo flow speed uncomplicated by acc axis migration we outline holocene and last glacial maximum lgm current controlled sedimentation using data from 3 5 khz profiles cores and current meter moorings geophysical surveys show areas of erosion and deposition controlled by neogene basement topography deposition occurs in mounded sediment drifts or flatter areas where 500 1000 m of sediment overlies acoustic basement 3 5 khz profiles show parallel continuous sub bottom reflectors with highest sedimentation rates in the centre of the drifts and reflectors converging towards marginal zones of non deposition locally on the flanks of continental blocks e g south georgia downslope processes are dominant the absence of mudwaves on the sediment drifts may result from the unsteadiness of acc flow a core transect from the acc axis south to the boundary with the weddell gyre shows a southward decrease in biogenic content controlled by the polar front and the spring sea ice edge both these features lay farther north at lgm the cores have been dated by relative abundance of the radiolarian cycladophora davisiana and by changes in the biogenic ba content a palaeoproductivity indicator sedimentation rates range from 3 to 17 cm ka the grain size of holocene sediments shows a coarsening trend from south to north consistent with strongest bottom current flow near the acc axis though interpretation is complicated by the presence of biogenic grains year long current meter records indicate mean speeds from 7 cm s in the south to 12 cm s in the north with benthic storm frequency increasing northwards lgm sediments are predominantly terrigenous and show a clearer northward coarsening trend with well sorted silts in the northern scotia sea assuming a constant terrigenous source this implies stronger acc flow at the lgm contrasting with weaker weddell gyre flow deduced from earlier work

paleomagnetism from deception island south shetlands archipelago antarctica new insights into the interpretation of the volcanic evolution using a geomagnetic model deception island shows the most recent exposed active volcanism in the northern boundary of the bransfield trough the succession of the volcanic sequence in the island is broadly divided into pre and post caldera collapse units although a well constrained chronological identification of the well defined successive volcanic episodes is still needed a new paleomagnetic investigation was carried out on 157 samples grouped in 20 sites from the volcanic deposits of deception island south shetlands archipelago antarctic peninsula region distributed in 1 volcanic breccia 3 sites and lavas 2 sites prior to the caldera collapse 2 lavas emplaced after the caldera collapse 10 sites and 3 dikes cutting pre and the lowermost post caldera collapse units 5 sites the information revealed by paleomagnetism provides new data about the evolution of the multi episodic volcanic edifice of this quaternary volcano suggesting that the present day position of the volcanic materials is close to their original emplacement position the new data have been combined with previous paleomagnetic results in order to tentatively propose an age when comparing the paleomagnetic data with a global geomagnetic model despite the uncertainties in the use of averaged paleomagnetic data per volcanic units the new data in combination with tephra occurrences noted elsewhere in the region suggest that the pre caldera units f1 and f2 erupted before 12 000 year bc the caldera collapse took place at about 8300 year bc and post caldera units s1 and s2 are younger than 2000 year bc

rapid high temperature formation of large scale rheomorphic structures in the 2 06 ma huckleberry ridge tuff idaho usa in the teton river canyon eastern idaho the ca 2 06 ma 130 m thick huckleberry ridge tuff exhibits large scale rheomorphic fold geometries defined by eutaxitic fabrics parallel to both the primary internal zonation and the basal contact with older strata paleomagnetic data from a large amplitude 150 m northwest trending overturned fold near the failed teton dam indicate folding above maximum magnetization unblocking temperatures 580 c the in situ characteristic remanent magnetization chrm direction is indistinguishable from previous studies of undeformed huckleberry ridge tuff and a fold test is negative k minimized at 100 unfolding anisotropy of magnetic susceptibility data reveal magnetic foliation planes that dip northeast roughly parallel to the axial surface of the fold because deformed and undeformed huckleberry ridge tuff exposures preserve the same anomalous chrm direction large scale rheomorphic structures in the tuff must have formed rapidly at high temperatures shortly after development of compaction fabrics post welding high temperature deformation is consistent with field evidence indicating rapid plastic secondary deformation of much of the tuff prior to devitrification

palaeoclimatological and chronological implications of the vostok core dust record the2 083 m vostok ice core recovered by the soviet antarctic expeditions has provided much information of climatic and environmental interest for a period covering a full glacial inter glacial cycle1 6 here we present and discuss the dust record obtained down to 2 202 m the final depth to which this core was extended in 1986 first we document the fact that major changes in aeolian deposits as recorded in the vostok core appear to be of global significance and confirm the existence of a link between high latitude aeolian deposits and the earth s orbital parameters7 8 second we propose atmospheric dust as a strati graphic marker to compare timing with other records of palaeocli mate and use the magnetic susceptibility profile measured along the rc11 120 indian ocean core9 for this purpose assuming that major dust events correspond to common aeolian inputs this approach indicates that the vostok and marine records were roughly in phase at the previous glacial interglacial transition

provenance and transport of terrigenous sediment in the south atlantic ocean and their relations to glacial and interglacial cycles nd and sr isotopic evidence sr and nd isotopic compositions of late quaternary surface sediment and sediment cores from the south atlantic and southeast pacific sectors of the southern ocean are used to constrain the provenance and transport mechanisms of their terrigenous component we report isotopic and mineralogical data for core samples from three localities the mid atlantic ridge at 41 s and the northern and southern scotia sea in addition data for surface sediment samples from the south atlantic and southeast pacific sectors of the southern ocean are presented the variations of sr and nd isotopic compositions of the bulk sediment samples in all cores were correlated with the magnetic susceptibility of the sediment and with the inferred glacial interglacial stages the isotopic data indicate that during glacial periods sediment was delivered from continental crust with a shorter residence time than that supplying material during interglacial periods at the core site near the mid atlantic ridge nd isotopic combined with mineralogical evidence indicates interglacial period deposition of a relatively high amount of kaolinite and silt with low nd values 4 5 probably derived from southern south america was indicated the glacial interglacial shift in sources may be due to either a decreasing influence of north atlantic deep water during glacial times or by a larger contribution of glaciogenic detritus from southern south america at the core site in the northern scotia sea sediment of interglacial periods is dominated by smectite with nd 4 we suggest that smectite was derived from the falkland shelf and silt was derived from the argentinian shelf during glacial periods the argentinian shelf was an important source for silt and chlorite with nd 4 the contribution from the falkland shelf seems to have remained similar during glacial and interglacial periods hydrographic transport by bottom currents and turbidites could account for the high glacial detrital flux an evaluation of the significance of an aeolian contribution to deep sea sediment suggests that it plays only a minor role in the southern scotia sea the antarctic peninsula is considered an important source for young material with nd 4 in particular during glacial periods during interglacial periods sediment supply from the antarctic peninsula was lower than during glacial times resulting in a relatively high contribution of old material nd 8 from east antarctica deep water currents and icebergs could account for the transport of the old component to the southern scotia sea the accumulation rates of material from the various source regions for glacial times are in agreement with an increase in the strength of the antarctic circumpolar current the production rate and the circulation pattern of bottom water in the weddell sea appear to have remained similar over most of the last 150 kyr

the holocene secche di lazzaro phreatomagmatic succession stromboli italy evidence of pyroclastic density current origin deduced by facies analysis and ams flow directions the edifice of stromboli volcano gravitationally collapsed several times during its volcanic history 100 ka present the largest holocene event occurred during the final stage of the neostromboli activity 13 5 ka and was accompanied by the emplacement of phreatomagmatic and lahar deposits known as the secche di lazzaro succession a stratigraphic and paleomagnetic study of the secche di lazzaro deposits allows the interpretation of the emplacement and the eruptive processes we identify three main units within the succession that correspond to changing eruption conditions the lower unit ua consists of accretionary lapilli rich thinly bedded parallel to cross stratified ash deposits interpreted to indicate the early stages of the eruption and emplacement of dilute pyroclastic density currents upward the second unit ub of the deposit is more massive and the beds thicker indicating an increase in the sedimentation rate from pyroclastic density currents the upper unit uc caps the succession with thick immediately post eruptive lahars which reworked ash deposited on the volcano s slope flow directions obtained by anisotropy of magnetic susceptibility ams analysis of the basal bed of ua at the type locality suggest a provenance of pyroclastic currents from the sea this is interpreted to be related to the initial base surges associated with water magma interaction that occurred immediately after the lateral collapse which wrapped around the shoulder of the sector collapse scar upward in the stratigraphy upper beds of ua and ub paleoflow directions change and show a provenance from the summit vent probably related to the multiple collapses of a vertical pulsatory eruptive column

onset of cenozoic antarctic glaciation abstract this paper considers the wide range of evidence both direct and indirect for the onset of cenozoic antarctic glaciation it distinguishes two useful phases of antarctic glacial onset an initial phase of mountain glaciation from which ice streams occasionally and in isolated locations reached sea level and a subsequent phase of full glaciation with an ice sheet as large as today s extending everywhere to sea level according to direct evidence generally proximal from the continent itself or surrounding southern ocean the first of these occurred probably during the late eocene while the second developed at the eocene oligocene boundary indirect evidence mainly involving proxy measurements from dsdp and odp sites remote from the southern ocean suggests that middle and late eocene glaciations may have been full also ice sheets possibly even larger than today s but short lived and that the e o boundary onset differed from these mainly in producing a stable ice sheet in pursuing the notion of glacial onset we examined the direct record separately for east antarctica west antarctica and the antarctic peninsula the different sub ice topography and geographic positions of which suggest that their glacial histories could have been different the direct record for an initial middle or late eocene phase is very sparse only the rare occurrence of ird at southern ocean dsdp and odp sites suggests the possibility of early ice and all three regions include mountains that could have hosted such ice although the indirect record and climate modelling in combination suggest that full glaciation of each region was probably synchronous we find differences in the available direct evidence there is abundant evidence that east antarctica became fully glaciated in the earliest oligocene but certain evidence of glaciation of a similar age extending to sea level is sparse for the antarctic peninsula and is not found until the late oligocene for west antarctica high resolution direct evidence is required to resolve uncertainties in glacial history

the shaw method of palaeointensity determinations and its application to recent volcanic rocks summary our new version together with previous versions of the shaw method has been compared by applying them to recent volcanic samples for which we have well determined palaeointensity values although the earlier modifications to the shaw method give a linear portion to the nrm trm diagram of all the specimens about half of the calculated palaeointensities deviate by more than 20 per cent from the expected values this may be caused by alteration of the magnetic minerals during the laboratory heating or by chemical alteration prior to the laboratory experiments the new modification uses a double heating of samples above the curie temperature in the laboratory after heating the specimen twice in the same field the measured intensity from the second heating is compared with the laboratory field intensity if the difference is larger than the experimental error then we assume that the anhysteretic remanent magnetization arm correction is not applicable and the sample is therefore rejected this technique provides a powerful criterion with which to select samples using this selection technique palaeointensities are generally within 10 per cent difference of the expected values with a success rate of about 40 per cent

scaling of columnar joints in basalt 1 we describe field work analysis and modeling of columnar joints from the columbia river basalt group this work is focused on the regions around the grand coulee snake river and columbia gorge which form parts of this unusually homogeneous and very large sample of columnar basalt we examine in detail the scaling relationship between the column width and the size of the striae and relate these quantitatively to thermal and fracture models we found that the column radius and stria size are proportional to each other and inversely proportional to the cooling rate of the lava near a flow margin our results put observational constraints on diffusive thermal models of joint formation deeper than a few meters into a colonnade our measurements are consistent with a simple advection diffusion model of two phase convective cooling within the joints regardless of the direction of cooling this model allows an accurate comparison of igneous columnar jointing and joints due to desiccation in laboratory analog systems we also identify a new length scale in which wavy columns can appear in some colonnades the mechanisms leading to the wavy columns are likely related to those underlying similar wavy cracks in 2 d analog systems

sedimentary patterns in the late quaternary southern ocean the spatial and temporal distribution of biogenic and lithogenic sediments in the late quaternary southern ocean reflects the zonal character of the antarctic circumpolar current and is basically controlled by glacial dynamics in antarctica sea ice distribution temperature gradients wind patterns and thermohaline ocean circulation carbonate patterns in most places reveal a decline in biogenic carbonate preservation during glacial periods mainly attributed to a reduced influx of north atlantic deep water and increased ocean stratification which modified deep water chemistry towards more corrosivity an important lithological feature of the southern ocean is the circumpolar opal belt which today is situated between the polar front and the seasonal sea ice limit to the south during the glacial periods the opal belt shifted to the north in response to a wider sea ice extension that reduced light availability and diatom productivity to the south biosiliceous productivity to the north likely was fueled by detrital iron supplied by aeolian dust input and or hemipelagic processes lithogenic fluxes generally increased during the glacial periods provenance studies on the origin and dispersal of detrital materials suggest combined effects of low sea level stands increased glaciogenic input and enhanced current transport to have caused elevated detrital fluxes the relative and absolute contribution of aeolian dust is difficult to decipher and awaits further clarification by integrated provenance studies of both marine sediments and more reference materials from the potential terrestrial source areas ice rafted debris ird represents a minor fraction of lithogenic sediments but can be used to infer both antarctic ice sheet dynamics and the fate of both sea ice and iceberg survival in the distal southern ocean future work should be concentrated on a better identification of ird origin in terms of volcaniclastic influences the distinction of east and west antarctic sediment sources and sea ice versus iceberg transportation

late brunhes polarity excursions mono lake laschamp iceland basin and pringle falls recorded at odp site 919 irminger basin abstract component natural remanent magnetizations derived from u channel and 1 cm3 discrete samples from odp site 919 irminger basin indicate the existence of four intervals of negative inclinations in the upper brunhes chronozone according to the age model based on planktic oxygen isotope data these excursional intervals occur in sediments deposited during the following time intervals 32 34 ka 39 41 ka 180 188 ka and 205 225 ka these time intervals correspond to polarity excursions detected elsewhere known as mono lake laschamp iceland basin and pringle falls the isotope based age model is supported by the normalized remanence paleointensity record that can be correlated to other calibrated paleointensity records for the 0 500 ka interval such as that from odp site 983 for the intervals associated with the mono lake and laschamp excursions virtual geomagnetic poles vgps reach equatorial latitudes and mid southerly latitudes respectively for intervals associated with the iceland basin and pringle falls excursions repeated excursions of vgps to high southerly latitudes indicate rapid directional swings rather than a single short lived polarity reversal the directional instability associated with polarity excursions is not often recorded probably due to smoothing of the sedimentary record by the process of detrital remanence drm acquisition

characterization of the magnetic fabric of rocks abstract an inextensive system of magnetic susceptibility anisotropy factors is suggested which is sufficient in the majority of practical applications for characterizing the magnetic fabric of rocks the system involves three newly devised factors the corrected anisotropy degree the shape factor and the difference shape factor the first of these characterizes the quantity of anisotropy somewhat better than the commonly used anisotropy degree the shape factor characterizes the quality of anisotropy i e the shape of the susceptibility ellipsoid in a convenient way its definition is based on a certain analogy between the anisotropy ellipsoid and the strain ellipsoid the difference shape factor can replace the shape factor when only the differences between the principal susceptibilities are given while the mean susceptibility is unknown

emplacement dynamics of phonolite magma into maar diatreme structures correlation of field thermal modeling and ams analogue modeling data abstract emplacement mode and original shape and dimensions of a well exposed phonolite body in the ceske st edoho i mountains czech republic were reconstructed using combined techniques of structural analysis of magmatic fabrics and columnar jointing together with analogue and thermal mathematical modeling of cooling for different shapes of experimental bodies phreatomagmatic rocks in the vicinity of some phonolite stocks in the area of interest suggest that the phonolite bodies were likely emplaced into maar diatremes our modeling revealed that intrusion of magma into phreatomagmatic maar diatreme craters can result in cryptodomes extrusive domes lava lakes or branched intrusions the fabric and columnar jointing pattern of the selected phonolite body reveals best fit with an asymmetric extrusive dome emplaced into the maar crater the scaling analysis and thermal modeling also suggest that the phonolite extrusion could have formed within 6 66 days and cooled to the background temperature after 10 000 years combined analogue and thermal modeling also revealed that the phonolite extrusions into maar diatreme craters are marked by upper tier collonade of vertical columns and lower tier of curved and outward flaring columns both tiers in the phonolite extrusions are divided by a subhorizontal suture

gld100 the near global lunar 100 m raster dtm from lroc wac stereo image data 1 we derived near global lunar topography from stereo image data acquired by the wide angle camera wac of the lunar reconnaissance orbiter camera lroc system from polar orbit tracks the lroc wac provides image data with a mean ground resolution at nadir of 75 m pixel with substantial cross track stereo overlap wac stereo images from the one year nominal mission and the first months of the science mission phase are combined to produce a near global digital terrain model dtm with a pixel spacing of 100 m the global lunar dtm 100 m or gld100 it covers 79 s to 79 n latitudes 98 2 of the entire lunar surface we compare the gld100 with results from previous stereo and altimetry based products particularly with the lunar orbiter laser altimeter lola altimetry which is the current topographic reference for the moon we describe typical characteristics of the gld100 and based upon the comparison to the lola data set assess its vertical and lateral resolution and accuracy we conclude that the introduced first version of the stereo based gld100 is a valuable topographic representation of the lunar surface complementary to the lola altimetry data set further improvements can be expected from continuative investigations

reappraisal of sea ice distribution in atlantic and pacific sectors of the southern ocean at 18 000 yr bp the question of the distribution of winter and summer sea ice cover during the last glacial maximum 18 000 yr bp is important in climatic modelling of the glacial world we have now compared satellite derived 5 yr monthly averages of per cent summer sea ice cover in the atlantic and pacific sectors of the southern ocean with the distribution of reported sedimentological indicators of sea ice cover at the sediment water interface these data strongly suggest that sediment type cannot be used to identify summer sea ice limits neither in recent sediments nor in sediments of the last glacial maximum rather the data seem to indicate that sediment type can be used to identify spring sea ice limits for these two time intervals

iron and other transition metals in patagonian riverborne and windborne materials geochemical control and transport to the southern south atlantic ocean abstract the bulk of particulate transition metals transported by patagonian rivers shows an upper crustal composition riverine particulate 0 5 n hcl leachable trace metal concentrations are mainly controlled by fe oxides complexation of fe by dissolved organic carbon doc appears to be an important determinant of the phases transporting trace metals in patagonian rivers in contrast aeolian trace elements have a combined crustal and anthropogenic origin aeolian materials have fe mn and al contents similar to that found in regional topsoils however seasonal concentrations of some metals e g co pb cu and zn are much higher than expected from normal crustal weathering and are likely pollutant derived we estimate that patagonian sediments are supplied to the south atlantic shelf in approximately equivalent amounts from the atmosphere 30 10 6 t yr 1 and coastal erosion 40 10 6 t yr 1 with much less coming from the rivers 2 0 10 6 t yr 1 low trace metal riverine fluxes are linked to the low suspended particulate load of patagonian rivers inasmuch most of it is retained in pro glacial lakes as well as in downstream reservoirs based on our estimation of aeolian dust fluxes at the patagonian coastline the high nutrient low chlorophyll sub antarctic south atlantic could receive 1 0 to 4 0 mg m 2 yr 1 of leachable 0 5 n hcl fe past and present volcanic activity in the southern andes through the ejection of tephra must be highlighted as another important source of fe to the south atlantic ocean based on the 1991 hudson volcano eruption it appears that volcanic events can contribute several thousand fold the mass of leachable fe to the ocean as is introduced by annual patagonian dust fallout

opal sedimentation shifts in the world ocean over the last 15 myr biogenic silica opal accumulation records were used to trace mechanisms consequence and geographic pattern of shifts in the main locus of opal deposition of the world ocean over the last 15 myr over this time interval the main opal sink seems to have moved from the north atlantic to the pacific equatorial pacific eastern equatorial pacific eastern boundary current upwelling systems california namibia peru and finally to the southern ocean the interplay between opal deposition and a series of climatic tectonic oceanographic and biologic events has been analyzed and discussed these events include the cenozoic global cooling trend intensified glaciation in antarctica late miocene early pliocene biogenic bloom development of northern hemisphere glaciation nhg closing of the panama seaway transition of the climate system from a monopolarto a bipolar glaciated world mid pleistocene revolution mpr nutrient availability evolution of diatoms and c4 plants and changes in continental weathering rates while the observed shifts are mostly traceable to oceanic reorganizations and global climatic evolution conditions favorable to opal deposition involve the above mentioned complex mix of processes for this reason the interpretation of opal deposition records might not always be straightforward we however believe that it can still provide clear indications of large scale oceanographic reorganizations in the geological past d 2004 elsevier b v all rights reserved

230th normalization an essential tool for interpreting sedimentary fluxes during the late quaternary there is increasing evidence indicating that syndepositional redistribution of sediment on the seafloor by bottom currents is common and can significantly affect sediment mass accumulation rates notwithstanding its common incidence this process generally referred to as sediment focusing is often difficult to recognize if redistribution is near synchronous to deposition the stratigraphy of the sediment is not disturbed and sediment focusing can easily be overlooked ignoring it however can lead to serious misinterpretations of sedimentary fluxes particularly when past changes in export flux from the overlying water are inferred in many instances this problem can be resolved at least for sediments deposited during the late quaternary by normalizing to the flux of 230th scavenged from seawater which is nearly constant and equivalent to the known rate of production of 230th from the decay of dissolved 234u we review the principle advantages and limitations of this method notwithstanding its limitations it is clear that 230th normalization does provide a means of achieving more accurate interpretations of sedimentary fluxes and eliminates the risk of serious misinterpretations of sediment mass accumulation rates

pleistocene collapse of the west antarctic ice sheet some glacial sediment samples recovered from beneath the west antarctic ice sheet at ice stream b contain quaternary diatoms and up to 108 atoms of beryllium 10 per gram other samples contain no quaternary diatoms and only background levels of beryllium 10 less than 10 6 atoms per gram the occurrence of young diatoms and high concentrations of beryllium 10 beneath grounded ice indicates that the ross embayment was an open marine environment after a late pleistocene collapse of the marine ice sheet

rock magnetic properties of trm carrying baked and molten rocks straddling burnt coal seams the subsurface spontaneous combustion of coal seams in xinjiang nw china during pleistocene to recent times produced large areas of thermally altered sedimentary rocks with large magnetic moments the natural remanent magnetization nrm and thermoremanent magnetization trm intensities and low field susceptibilities of such combustion metamorphic rocks range from 0 1 to 10 a m and 100 10 4 to 1000 10 4 si respectively which is two to three orders of magnitude higher than values typical of their sedimentary protoliths the dominant magnetic carriers in the burnt rocks appear to include relatively pure forms of magnetite maghemite and hematite as well as more complex spinel phases these magnetic phases mainly occur as fine pseudo single domain psd particles conspicuous is the presence of pure metallic iron fe in some samples this highly magnetic phase is inferred to appear as more or less elongated super paramagnetic and single domain sd inclusions in host silicate phases which prevent them from oxidizing the sd fe particles can carry a highly stable remanence having remanent coercivities ranging 70 140 mt the arm and irm stability of all burnt rock samples to alternating fields is shown to be relatively high median destructive fields b 1 2 a and b 1 2 i respectively range of 25 46 and 20 30 mt for dominant spinel bearing samples 34 36 and 47 53 mt for maghemite hematite bearing samples and 48 89 and 64 84 mt for metallic iron bearing samples consequently burnt rocks are high quality geomagnetic field recorders their very nature makes them useful for paleointensity determinations although age determination is a limiting factor furthermore remanence intensities and susceptibilities of these magnetically enhanced rocks are sufficient to produce observable magnetic anomalies this property illustrates the potential to delineate the areal extent and depth of extinct coal fires with magnetic exploration such information is necessary to refine estimates of hazardous co 2 emission and furthers our understanding of natural coal fires 2001 elsevier science b v all rights reserved

geomagnetic paleointensity deduced for the last 300 kyr from unzen volcano japan and the dipolar nature of the iceland basin excursion abstract we have conducted paleointensity measurements of lavas and pyroclastic flows from unzen volcano japan they have been shown in a previous study to contain a record of brunhes chron secular variation with one flow recording a transitional direction senbongi geomagnetic excursion 191 17 ka various rock magnetic analyses indicate that the main magnetic carriers of samples are ti poor titanomagnetites which have mixtures of single domain sd and or pseudo sd and multi domain grain sizes the low temperature demagnetization ltd double heating test dht shaw method yielded 209 successful results from 56 sites giving 27 acceptable site mean paleointensities for the past 5 300 kyr when excluding the senbongi excursion data and two other data points the data give an average virtual dipole moment vdm of 7 69 10 22 a m 2 with a standard deviation of 2 51 10 22 a m 2 n 24 this is consistent with the selected 80 site mean thellier paleointensity data from the latest paleointensity database with an average vdm of 7 64 10 22 a m 2 and a standard deviation of 2 56 10 22 a m 2 paleointensity measurements on samples that record the senbongi excursion which is claimed to correlate with the iceland basin excursion provide a value of 7 74 9 37 t using the ltd dht shaw method this corresponds to an average standard deviation vdm of 2 19 10 22 a m 2 0 21 10 22 a m 2 when calibrating sedimentary records that capture the iceland basin excursion by averaging the ltd dht shaw vdms obtained from the pre and post excursional period the records give consistent vdm values with the volcanic senbongi record during the excursion this indicates that variation of the geomagnetic field direction and intensity during the iceland basin excursion can be well represented by a simple dipolar variation

a holocene paleosecular variation record from 14c dated volcanic rocks in western north america 1 a paleosecular variation psv curve for western north america is presented on the basis of 94 virtual geomagnetic poles vgps from dated volcanic rocks sampled at 446 sites approximately 60 of the paleomagnetic database has been previously published a curve defined by spherical smoothed splines is fitted to the vgps ranked by the quality of the age determinations where the data density is highest between 3690 and 30 years before present b p a d 1950 between 7800 and 7050 years b p and between 14 060 and 12 700 years b p the younger segments of the curve derived from volcanic rocks are similar but less complex than other high resolution psv curves derived from lacustrine sediments particularly the record at fish lake oregon the psv record from lava flows psvl however is perhaps more reliable in its general shape and chronology because of the higher fidelity of volcanic rocks as magnetic field recorders and because of the greater density of 14c dates the new psvl record provides a partial holocene master curve for western north america and will be of particular value in dating geological and archeological materials using paleomagnetic directions

insights into deposition and deformation of intra caldera ignimbrites central nevada abstract magnetic studies together with structural and 40 ar 39 ar age analyses were used to investigate the development and deformation of ignimbrites of the caetano tuff formation in central north nevada magnetic susceptibility susceptibility anisotropy ams and magnetic remanence approaches were used to decipher events accompanying emplacement and subsequent deformation of that tuff for both intracaldera tuffs and outflow deposits 40 ar 39 ar ages both those presented here and previously published ages indicate about 33 8 ma for the age of caetano ignimbrites approximately at the eocene oligocene boundary although extensive faulting associated with regional extension of the great basin region has dissected these deposits the thickness of the intra caldera ignimbrites has been estimated at 3 5 km or more thermal modeling for cooling of a caldera filling of 3 5 km thickness indicates acquisition of remanent magnetization can persist up to 25 ka sufficient to average secular variation this contrasts with rapid cooling and remanence acquisition in outflow ignimbrites typically only tens of meters thick a 750 m thick reference section was selected for more detailed study about 10 km to the west of the type area this reference section fault bounded at both base and top represents the upper part of the formation its lower member includes the uppermost 250 m of the lower massive resistant unit of ignimbrites a middle member of 375 m of well stratified pyroclastic deposits vitrophyres and sediments and an upper member of about 125 m of recessive ignimbrite and thin bedded clastic and pyroclastic deposits structural and magnetic remanence measurements suggest 13 eastward tilting of the caldera floor occurred early during deposition of the middle member flow directions inferred from ams k max axes in the middle member diverge about 45 relative to those in the underlying member and suggest a change in vent source accompanying the deposition of the middle member correcting for e w extension the outflow ignimbrites reached approximately 20 km to the west and south of the caldera north of the caldera ignimbrites formerly assigned to the caetano tuff but now assigned to the tuff of cove mine exhibit variable flow directions from an indeterminate source significantly however the intracaldera ams magnetic lineations conventionally used as proxies for flow lines trend mainly wnw parallel to a proposed major paleodrainage which stretches from the southern cortez range through 40 km to the tobin range caetano tuff magnetic remanence is entirely reversed and corresponds to magnetization acquired in the younger part of magnetochron 13r the magnetic remanence directions of both the intra caldera and outflow ignimbrites are similar d 151 i 60 significantly different from those predicted by a coeval reference pole for north america raising the possibility of a regional counterclockwise rotation of the sampling area of 15 6 presumably this began during faulting and major regional extension about 16 ma ago during the middle miocene and possibly continued later

late quaternary variability of ocean circulation in the southeastern south atlantic inferred from the terrigenous sediment record of a drift deposit in the southern cape basin odp site 1089 during leg 177 of the ocean drilling program an expanded sequence of pliocene to holocene calcareous muds was recovered at site 1089 on a drift deposit in the southern cape basin se south atlantic the reconstruction of detrital sources and modes of sediment transport gives insight into the operational modes of regional current systems in response to climate variability over the last 590 kyr as inferred from sedimentological and mineralogical parameters of the terrigenous sediment fraction terrigenous sediments mainly originate from african sources with minor contributions from distant southern sources south america and antarctica and are supplied by circumpolar water masses north atlantic deep water nadw and surface currents of the agulhas current changes in clay mineralogy as tracers of deep and shallow ocean circulation best displayed by variations in quartz feldspar ratios and kaolinite chlorite ratios of clay reflect both the northward displacement of nadw injection into the antarctic circumpolar current and a weakening of agulhas current leakage from the indian ocean around south africa to the south atlantic during glacial stages sub stages and stadials modifications of these regional current patterns are consistent with perturbations in global conveyor circulation and climate variability on milankovitch and sub milankovitch time scales elevated mass accumulation rates of terrigenous matter generally document high particle fluxes and focusing effects by bottom current action throughout the late quaternary current sorting and coarsening of terrigenous mud independently of its source signals prevails during interglacial periods and is linked to a stronger flow of antarctic bottom water and the invigoration of deep contour currents in response to long term changes 100 kyr cyclicity in antarctic ice sheet dynamics high amplitude fluctuations in global sea level and increased bottom water formation

stratigraphy paleomagnetism and magnetic fabric of the toba tuffs constraints on the sources and eruptive styles the toba depression in north central sumatra is a complex of several overlapping calderas resulting from three major ignimbrite forming eruptions within the depression the upland masses of samosir and northern uluan consist of welded ignimbrite capped by coarse breccia and lacustrine sediment hitherto interpreted to be two parts of a single resurgent dome this study has demonstrated that the welded tuffs of samosir and uluan have different magnetic polarities and therefore at least two different ignimbrites are present the samosir uluan massif may consist of parts of two resurgent domes the first ignimbrite eruption occurred at 0 84 ma and produced a very thick 400 m densely welded unit having a reversed polarity anisotropy of magnetic susceptibility ams flow direction and lithic size data indicate that the source lies in the southern part of the toba depression and the thick deposit of uluan is thought to have ponded in a 40 km wide caldera the second ignimbrite is normally magnetized ams flow direction data indicate two separate source vents one to the north in the haranggaol caldera and another to the south the thick deposit at samosir is thought to have ponded in the southern caldera coarse sediments then accumulated over samosir and northern uluan and were capped by lacustrine deposits a renewed episode of resurgence then uplifted samosir island and possibly the northern part of uluan at approximately 0 075 ma the last and apparently largest ignimbrite eruption occurred from calderas in the north and south parts of the toba depression this ignimbrite is mostly nonwelded and normally magnetized part of the uluan dome was destroyed by collapse of the sibandung caldera and latung graben and concomitant with renewed subsidence of the haranggaol and porsea calderas

integration of chang e 1 imagery and laser altimeter data for precision lunar topographic modeling lunar orbital imagery and laser altimeter data are two major data sources for lunar topographic modeling most of the previous work has processed imagery and laser altimeter data separately usually though there are inconsistencies between the topographic models derived from them this paper presents an endeavor to integrate the chang e 1 imagery and laser altimeter data for consistent and precision lunar topographic modeling a combined adjustment model for the chang e 1 imagery and laser altimeter data is developed in which the participants are the laser altimeter points image exterior orientation eo parameters and tie points collected from the stereo images a weighting scheme is designed for the participants in the adjustment and a local surface constraint is imposed to improve the adjustment performance the output of the combined adjustment is the refined image eo parameters and laser ground points experimental results using the chang e 1 data in the apollo 15 and 16 landing site areas show that the proposed combined adjustment approach can reduce the misregistrations between the imagery and the laser altimeter data by a maximum of 1 18 pixels in image space the japanese selenological and engineering explorer selene laser altimeter data at the apollo 15 and 16 landing site areas are employed for comparison analysis small shifts between the selene and chang e 1 laser altimeter data were found the topography derived from chang e 1 data after the combined adjustment shows a relatively consistent trend with the topography determined by the selene laser altimeter data

palaeointensities of the auckland geomagnetic excursions by the ltd dht shaw method we report new palaeointensity results concerning the auckland geomagnetic excursions using the double heating technique of the shaw method with low temperature demagnetisation ltd dht shaw method the excursional palaeodirections recorded in six volcanoes of the auckland volcanic field new zealand have been classified into three groups north down nd west up wu and south up su directions in the present study five to six consistent palaeointensities have been obtained from each of five volcanoes recording the auckland geomagnetic excursions the wiri 27 ka crater hill and puketutu volcanoes nd group yielded mean palaeointensities of 10 6 1 2 1 11 8 2 8 and 11 1 0 4t respectively the hampton park volcano 55 ka wu group gave 9 5 1 2t while the mclennan hills volcano su group gave 2 5 0 5t it is notable that consistent palaeointensities have been obtained from the three different volcanoes which have almost the same palaeodirections nd group possibly supporting the reliability of the palaeointensity data these five palaeointensities for the auckland geomagnetic excursions correspond to virtual dipole moments vdms of 0 6 2 1 10 22 am 2 whereas three mean palaeointensities obtained from the auckland volcanoes having non excursional palaeodirections are 13 1 40 0 t giving stronger vdms of 2 1 6 9 10 22 am 2 these results suggest that the dipole component of the geomagnetic field reduced to about 2 10 22 am 2 or less during the auckland geomagnetic excursions

terrigenous input and paleoproductivity in the southern ocean the geochemistry of several sites along the polar front zone of the southern ocean revealed significant changes in terrigenous input and productivity on glacial timescales our records indicate concentrations and fluxes of terrigenous elements i e fe al and ti are low during interglacials and increase tenfold to twentyfold during glacials phosphorus accumulation reactive p concentrations and p ti ratios exhibit similar trends as the terrigenous components suggesting increased export production during glacials in all cores elemental ratios remain relatively constant indicating terrigenous sources at each site have not likely varied over the past 250 kyr iron accumulation rates for these sites are 10 times higher during glacials than interglacials and exceed the estimated regional eolian fluxes by 50 times the source of this terrigenous material is thus likely to be hemipelagic rather than direct eolian input or ice rafting and we speculate fe upwelled from this source may have stimulated glacial productivity in the southern ocean

a sediment record of cyclic bottom current variability from the northwest weddell sea cores and 3 5 khz sub bottom profiles collected from the continental slope and rise near 64 s 52 w off the tip of the antarctic peninsula reveal transport and depositional processes in a high energy environment a large channel runs downslope from the shelf break the remaining slope area is smooth and shows no acoustic penetration except locally in the lee of topography sediments on the slope and rise were mainly deposited by suspension from a 150 to 300 m thick nepheloid layer periodic resuspension and winnowing by bottom currents has produced coarse lags of ice rafted debris throughout these deposits and has also produced an elongated field of mudwaves running parallel to the base of the slope these low amplitude asymmetric features were formed by currents flowing from west to east parallel to the local slope short gravity cores show a compositional and textural cyclicity developed between two distinct lithologies intervals of poorly sorted sediment barren of fauna and with mud dominated size distributions are interpreted to result from a cold climate and low bottom current strength production of weddell sea bottom water probably lessened during these times and there was a greater duration of sea ice cover these sediments are interbedded with winnowed and better sorted deposits comprising fine sands and silts that contain abundant planktonic foraminifera interpreted as implying warmer climatic conditions and stronger current activity a varied calcareous benthic foraminiferal assemblage also indicates that these intervals lay above the ccd during deposition renewed and invigorated production of bottom water is implied contemporaneous with a shorter duration of sea ice cover petrographic evidence indicates an antarctic peninsula source throughout the cycles are considered to be the result of climatic fluctuations occurring over the timespan of glacial interstadials although confirmation of this timescale awaits acquisition of an absolute chronology

the blake geomagnetic excursion recorded in a radiometrically dated speleothem one of the most important developments in geomagnetism has been the recognition of polarity excursions of the earth s magnetic field accurate timing of the excursions is a key point for under standing the geodynamo process and for magnetostratigraphic correlation one of the best known excursions is the blake geomagnetic episode which occurred during marine isotope stage mis 5 but its morphology and age remain controversial here wes how for the first time the blake excursion recorded in a stalagmite which was dated using the uranium series dis equilibrium techniques the characteristic remanent magnetisation is carried by fine grained magnetite the eventis documented by two reversed intervals b1 and b2 the age of the eventis estimated to be between 116 5 0 7 kyr bp and 112 0 1 9 kyr bp slightly younger 3 4 kyr than recent estimations from sedimentary records dated by astronomical tuning low values of relative palaeointensity during the blake episode are estimated but a relative maximum in the palaeofield in tensity coeval with the complete reversal during the b2 interval was observed duration of the blake geomagnetic excursion is 4 5 kyr two times lower than single excursions and slightly higher than the estimated diffusion time for the inner core 3 kyr

magnetic fabric flow directions and source area of the lower miocene peach springs tuff in arizona california and nevada we have used anisotropy of magnetic susceptibility ams to define the flow fabric and possible source area of the peach springs tuff a widespread rhyolitic ash flow tuff in the mojave desert and great basin of california arizona and nevada the tuff is an important stratigraphic marker from the colorado plateau to barstow california a distance of 350 km however the location of its source caldera is unknown dated at 18 5 ma by 40ar 39 ar the tuff erupted during the early stages of miocene extension along the lower colorado river the thicker accumulations 100 m occur at kingman arizona and in the piute mountains california on opposite sides of the colorado river extensional corridor our ams studies produced well defined magnetic lineations in 30 of 42 sites distributed throughout the tuff typical ratios of the principal ams axes are 1 01 for the magnetic lineation kmax kint and 1 02 for the foliation kint kmin the bulk magnetic susceptibility of the peach springs tuff averages 2 0 10 3 in the si unit system the subhorizontal lineations which presumably parallel the flow directions form a pattern radiating outward from the approximate center of the outcrop area magnetic foliations define an imbrication that generally dips away from the distal margins and toward the center of the outcrop of the tuff the lineation and imbrication indicate a source region near the southern tip of nevada defining the best intersection of the ams lineations required restoration of major extension strike slip faulting and associated tectonic rotation in the disrupted tuff the optimum intersection of magnetic lineations lies in the southern black mountains of arizona on the eastern side of the colorado river extensional corridor no caldera structures are known from that area but the area contains thick sections of the peach springs tuff above a silicic volcanic center the caldera may be buried under younger deposits in the mohave valley of arizona tertiary granite in the newberry mountains may represent a deeper level of the peach springs tuff vent that has been exhumed by detachment faulting

flow directions in ash flow tuffs a comparison of geological and magnetic susceptibility measurements tshirege member upper bandelier tuff valles caldera new mexico usa this study concludes that the elongation axis k 1 of the ellipsoid of anisotropic magnetic susceptibility ams is a suitable proxy for flow axis in ashflow tuffs 153 oriented samples 176 specimens were studied from 18 sites in the 1 1 ma tshirege member of the bandelier tuff these sites are distributed around the valles caldera at distances of 5 25 km outside of the rim k 1 axes correlate well with postulated radial flow axes at 13 sites k 1 also agrees with measured geological flow indicators mainly imbricated larger clasts at 7 sites at 2 of the 5 sites where significant disagreement is seen between theoretical radial flow directions and measuredk 1 axes thek 1 axes correspond well with geological flow indicators indicating that the divergence of flow from the predicted radial flow pattern is real two major topographic buttresses are suggested as the cause of flow divergence for the tshirege ash flows the san pedro buttress northwest of the caldera and the san miguel buttress in the southeast in situk 1 axes plunge about 7 toward the source at two thirds of the sites therefore the plunge ofk 1 is a plausible in situ indicator for thedirection of flow multiple flow zones in sections of several meters thickness indicate changes of flow direction that are both rapid and large during ash flow emplacement these observations raisre the question of how best to represent mean flow directions in ash flow sheets by eigenvector methods by vector sum methods or by modes a method for measuring imbrication of larger clasts using apparent dips in vertical joints is outlined imbrication determined in this way at one third of the sites dips toward the source i e up flow the minimum k 3 axis of the ams ellipsoid correlates with the flow foliation rather than with the larger clast imbrication the flow axes of ash flows correspond with thek 1 axes not with the declination ofk 3 axes as suggested by some authors initial dip of the sampled ash flows is not large and does not affect the paleomagnetic remanence direction which is reversed with a mean ofd 173 5 i 38 4 95 3 4 n 18 this mean is not different at the 95 confidence level from that of earlier workers the mean pole at 098 0 e 74 8 n a 95 3 3 n 18 is about 15 far sided relative to the expected time averaged geomagnetic pole suggesting a history of emplacement too short to adequately average secular variation

instantaneous record of the geomagnetic field direction of various facies from pyroclastic flow deposits tests for consistency in paleomagnetic directions abstract a comparative study of the paleomagnetism of various lithofacies of pyroclastic flow deposits has been undertaken to examine the accuracy of their remanent magnetization direction at the time of deposition the aso 2 pyroclastic flow deposit which erupted at 141 ka from aso caldera japan was chosen as the site of our investigation because the deposit formed over a short time period and the paleomagnetic directions of the deposit are expected to record substantial contemporaneous volcanism paleomagnetic samples of densely welded lava like rheomorphic and non welded pyroclastic deposits were collected at nine sites from the aso 2 pyroclastic flow deposit remanence directions from densely welded pyroclastic deposits display good within and between site consistency and are considered to accurately record the ambient geomagnetic field direction at the time of emplacement rheomorphic pyroclastic deposits had directions that show good within site consistency and it is considered that this material obtains its remanence direction parallel to the ambient field corresponding to the time of its emplacement remanence directions from non welded pyroclastic deposits show large confidence limits or deviations from their expected directions such deposits would likely be prone to modification of remanence direction introduced from random rotations of remanence carrying material during syn or post depositional stages in conclusion we suggest that among various lithofacies of pyroclastic flow deposits remanence directions observed from non welded pyroclastic deposits may need to be interpreted cautiously

ages of mare basalts on the lunar nearside the chronology of lunar volcanism is based on radiometric ages determined from apollo and luna landing site samples regional stratigraphic relationships and crater degradation and size frequency distribution data for units largely defined prior to the end of the apollo program here we report on new crater size frequency distribution data for 139 spectrally and morphologically defined basalt units which are exposed in six nearside impact basins australe tranquillitatis humboldtianum humorum serenitatis and imbrium crater size frequency distribution measurements are a statistically robust and accurate method to derive absolute model ages of unsampled regions of the moon compared to crater degradation ages crater size frequency ages performed on spectrally defined units offer significant improvements in accuracy our investigation showed that 1 in the investigated basins lunar volcanism was active for at least 1 5 2 0 b y starting at about 3 9 4 0 b y and ceasing at 2 0 b y 2 most basalts erupted during the late imbrian period at about 3 6 3 8 b y 3 significantly fewer basalts were emplaced during the eratosthenian period 4 basalts of copernican age were not found in any of the investigated basins 5 lunar basin filling volcanism probably started within 100 m y after the formation of the individual basins we also assessed the relationship between impact basin age and the history of mare basalt emplacement in these basins we found that 1 in all pre nectarian basins australe and tranquillitatis as well as in the humboldtianum basin which is of nectarian age the distribution of surface ages is clearly dominated by only a single peak in the number of erupted units at 3 6 3 8 b y 2 in the younger basins humorum serenitatis and imbrium a second peak at 3 3 3 5 b y is observed 3 basalt eruptions younger than 2 6 b y occur only intermittently and 4 in the youngest basins serenitatis and imbrium we see an extended period of active basin filling volcanism 1 5 1 6 b y which is 500 m y longer than in the australe and humorum and even 1 0 b y longer than in tranquillitatis and humboldtianum

paleointensity measurements of pyroclastic flow deposits co born with widespread tephras in kyushu island japan we report the results of paleointensity determination with welded pyroclastic flow deposits co born with widespread tephras derived from kikai k ah 7 3 ka aira at 28 ka and aso aso 1 270 ka aso 2 140 ka aso 3 120 ka aso 4 90 ka calderas in kyushu island japan since the widespread tephras are commonly used as good key layers their ages and oxygen isotope stages have been well established thermal demagnetization and several rock magnetic experiments showed that the pyroclastic flow samples had stable remanent magnetizations and are suitable for paleointensity measurements using thelliers method we obtained reliable paleointensities from six eruptive units and calculated corresponding virtual dipole moment vdm values ranging from 2 7 to 9 7 10 22 am 2 vdms for the youngest units k ah and at are consistent with the global trend of increasing dipole moment for the past 40 kyr aso 4 3 and 1 yield moderate vdms similar to the mean paleointensity for the past 1 myr and especially the results from aso 4 and 3 show good agreement with the vdm variation between 70 and 130 ka obtained from la reunion island j geophys res 96 1991 1981 earth planet sci lett 140 1996 173 a low vdm value and an abnormal vgp position obtained from aso 2 suggest a possibility that aso 2 records an excursion like event occurred around 140 ka between blake and jamaica events 2002 elsevier science b v all rights reserved

the formation of columnar joints produced by cooling in basalt at staffa scotland columnar jointing in basaltic lava flows on the island of staffa nw scotland was studied using a combination of field mapping and measurement of column dimensions sample petrology and measurements of plagioclase crystal size distributions csds interpreted using theoretical models of cooling four different lava flow units were measured and column ordering was assessed using the hexagonality index and relative standard deviations of column side length top area and internal angle upper and lower colonnades consist of dominantly 5 6 and 7 sided columns with a hexagonality index value very similar to that of giant s causeway and other basaltic columnar jointed localities csds from samples at different heights within one colonnade were used to infer the propagation of the solidus isotherm which was consistent with a convective cooling mechanism within the colonnade interior sample petrology and csd measurements suggest that entablature can form both by the interaction of propagating joint sets and flooding of the flow surface by water and the most widely exposed unit on staffa shows evidence of both mechanisms operating on the same flow crystal size distribution measurements can provide a useful tool for field interpretation of lava flow cooling mechanisms

magnetic anisotropy in rhyolitic ignimbrite snake river plain implications for using remanent magnetism of volcanic rocks for correlation paleomagnetic studies and geological reconstructions some of the field and laboratory expenses for this work were covered by the natural environment research council nerc grant ne g005372 1 the salary and school fees for the first author were covered in part by a national science foundation nsf grant ear 443549 81179 awarded to x zhao

impact cratering in and around the orientale basin results from recent high resolution remote sensing datasets abstract impact craters are the predominant geological features on the lunar surface data about the craters are crucial for inferring information about surface age the generation processes of the geological units and the sequences of geological events the higher resolution remote sensing datasets collected by recent lunar missions enable the investigation of impact craters of smaller size and provide more accurate information this paper presents an investigation of the distribution and population characteristics of impact craters in and around the orientale basin based on high resolution datasets first an update to the crater catalogue for the orientale basin and its surrounding area is provided including craters as small as 1 km in diameter based on the updated crater catalogue the crater densities and depth to diameter ratios in and around the orientale basin are investigated the inclusion of small craters enables a crater density map with higher resolution revealing a significantly higher crater density of the study area also the surface age of orientale basin is estimated from the size frequency distribution sfd using the new crater catalogue showing an age of 3 75 ga using the production function of neukum et al 2001 which is in good agreement with previous studies finally distribution patterns of secondary craters around the orientale basin are investigated indicating the orientale basin may be caused by an oblique impact with a downrange direction of about 235 260 and an offset strength towards the direction of about 305 350

evidence against dust mediated control of glacial interglacial changes in atmospheric co2 the low concentration of atmospheric co2 inferred to have been present during glacial periods is thought to have been partly caused by an increased supply of iron bearing dust to the ocean surface1 this is supported by a recent model2 that attributes half of the co2 reduction during past glacial stages to iron stimulated uptake of co2 by phytoplankton in the southern ocean but atmospheric dust fluxes to the southern ocean even in glacial periods are thought to be relatively low and therefore it has been proposed that southern ocean productivity might be influenced by iron deposited elsewhere for example in the northern hemisphere3 4 which is then transported south via ocean circulation similar to the distal supply of iron to the equatorial pacific ocean5 6 7 here we examine the timing of dust fluxes to the north atlantic ocean in relation to climate records from the vostok ice core in antarctica around the time of the penultimate deglaciation about 130 kyr ago two main dust peaks occurred 155 kyr and 130 kyr ago but neither was associated with the co2 rise recorded in the vostok ice core this mismatch together with the low dust flux supplied to the southern ocean suggests that dust mediated iron fertilization of the southern ocean did not significantly influence atmospheric co2 at the termination of the penultimate glaciation

meandering flow of a pyroclastic density current documented by the anisotropy of magnetic susceptibility ams in the quartz latite ignimbrite of the pleistocene monte cimino volcanic centre central italy abstract a pattern of shifting current direction is revealed by the anisotropy of magnetic susceptibility ams in the quartz latite ignimbrite associated with the pleistocene cimini dome complex in central italy high field ams documents that both paramagnetic and ferrimagnetic minerals contribute to the magnetic fabric of the ignimbrite the results of low field ams studies suggest that the pyroclastic density current changed both direction and character during deposition of each flow unit that makes up the ignimbrite the meandering behaviour of the currents can be observed on the scale of 15 cm increments in the fine grained basal layer 2a of one flow unit in an area lacking significant palaeotopography ams data from 1 2 and 4 metre increments through the flow units also show complex changes in flow direction throughout the deposition of each unit studied the most closely aligned ams fabrics occur near the bases of flow units and dispersion increases upward this trend may represent decreased shear between the flow and the substrate or increased turbulence in the upper depositional zone of the pyroclastic density current or both suggesting a progressively waning current in terms of capacity or particle concentration the phenomena observed in this study have broad implications for the general methodology of ams studies detailed vertical profiles made up of several individual sample sites within 1 metre thickness intervals can reveal small scale current flow variations that may not be evident if sampling is done more sparsely

clay mineral distribution in surface sediments of the south atlantic sources transport and relation to oceanography abstract surface samples mostly from abyssal sediments of the south atlantic from parts of the equatorial atlantic and of the antarctic ocean were investigated for clay content and clay mineral composition maps of relative clay mineral content were compiled which improve previous maps by showing more details especially at high latitudes large scale relations regarding the origin and transport paths of detrital clay are revealed high smectite concentrations are observed in abyssal regions primarily derived from southernmost south america and from minor sources in southwest africa near submarine volcanoes of the antarctic ocean south sandwich bouvet island smectite contents exhibit distinct maxima which is ascribed to the weathering of altered basalts and volcanic glasses the illite distribution can be subdivided into five major zones including two maxima revealing both south african and antarctic sources a particularly high amount of mg and fe rich illites are observed close to east antarctica they are derived from biotite bearing crystalline rocks and transported to the west by the east antarctic coastal current chiorite and well crystallized dioctaedral illite are typical minerals enriched within the subantarctic and polarfrontal zone but of minor importance off east antarctica kaolinite dominates the clay mineral assemblage at low latitudes where the continental source rocks west africa brazil are mainly affected by intensive chemical weathering surprisingly a slight increase of kaolinite is observed in the enderby basin and near the filchner ronne ice shelf the investigated area can be subdivided into ten large scale clay facies zones with characteristic possible source regions and transport paths clay mineral assemblages of the largest part of the south atlantic especially of the western basins are dominated by chlorite and illite derived from the antarctic peninsula and southernmost south america and supported by advection within the circumantarctic deep water flow in contrast the east antarctic provinces are relatively small assemblages of the eastern basins north of 30 s are strongly influenced by african sources controlled by weathering regimes on land and by a complex interaction of wind river and deep ocean transport the strong gradient in clay mineral composition at the brazilian slope indicate a relatively low contribution of tropically derived assemblages to the western basins

integration of chang e 2 imagery and lro laser altimeter data with a combined block adjustment for precision lunar topographic modeling abstract lunar topographic information is essential for lunar scientific investigations and exploration missions lunar orbiter imagery and laser altimeter data are two major data sources for lunar topographic modeling most previous studies have processed the imagery and laser altimeter data separately for lunar topographic modeling and there are usually inconsistencies between the derived lunar topographic models this paper presents a novel combined block adjustment approach to integrate multiple strips of the chinese chang e 2 imagery and nasa s lunar reconnaissance orbiter lro laser altimeter lola data for precision lunar topographic modeling the participants of the combined block adjustment include the orientation parameters of the chang e 2 images the intra strip tie points derived from the chang e 2 stereo images of the same orbit the inter strip tie points derived from the overlapping area of two neighbor chang e 2 image strips and the lola points two constraints are incorporated into the combined block adjustment including a local surface constraint and an orbit height constraint which are specifically designed to remedy the large inconsistencies between the chang e 2 and lola data sets the output of the combined block adjustment is the improved orientation parameters of the chang e 2 images and ground coordinates of the lola points from which precision lunar topographic models can be generated the performance of the developed approach was evaluated using the chang e 2 imagery and lola data in the sinus iridum area and the apollo 15 landing area the experimental results revealed that the mean absolute image residuals between the chang e 2 image strips were drastically reduced from tens of pixels before the adjustment to sub pixel level after adjustment digital elevation models dems with 20 m resolution were generated using the chang e 2 imagery after the combined block adjustment comparison of the chang e 2 dem with the lola dem showed a good level of consistency the developed combined block adjustment approach is of significance for the full comparative and synergistic use of lunar topographic data sets from different sensors and different missions

patagonian origin of glacial dust deposited in east antarctica vostok and dome c during glacial stages 2 4 and 6 abstract the source area of continental dust deposited at both vostok and dome c sites east antarctica during the glacial stages stage 2 18 ka last glacial maximum stage 4 60 ka and stage 6 160 ka of the last two climatic cycles has remained constant the isotopic composition 87 sr 86 sr and 143 nd 144 nd of the ice core dust has been compared with the isotopic composition of the potential source areas antarctica new zealand southern africa australia and south america this comparison reveals the southern south american provenance of the dust for all three glacial periods as has already been shown for the lgm 1 we show that the patagonian loess and the marine shelf sediments from the argentine continental shelf which was variably emerged during glacial periods display different isotopic compositions and that the composition of the patagonian loess best matches the signature of the ice core dust the identification of the patagonian region as the source of the windblown dust deposited over east antarctica during all the latest glacial periods permits a better understanding of paleo atmospheric circulations of the last climatic cycles and a better constraint on the parametrization of dust sources for paleoatmospheric general circulation models

provenance and dispersal of glacial marine surface sediments in the weddell sea and adjoining areas antarctica ice rafting versus current transport abstract mineralogical and granulometric properties of glacial marine surface sediments of the weddell sea and adjoining areas were studied in order to decipher spatial variations of provenance and transport paths of terrigenous detritus from antarctic sources the silt fraction shows marked spatial differences in quartz contents in the sand fractions heavy mineral assemblages display low mineralogical maturity and are dominated by garnet green hornblende and various types of clinopyroxene cluster analysis yields distinct heavy mineral assemblages which can be attributed to specific source rocks of the antarctic hinterland the configuration of modern mineralogical provinces in the near shore regions reflects the geological variety of the adjacent hinterland in the distal parts of the study area sand sized heavy minerals are good tracers of ice rafting granulometric characteristics and the distribution of heavy mineral provinces reflect maxima of relative and absolute accumulation of ice rafted detritus in accordance with major iceberg drift tracks in the course of the weddell gyre fine grained and coarse grained sediment fractions may have different origins in the central weddell sea coarse ice rafted detritus basically derives from east antarctic sources while the fine fraction is discharged from weak permanent bottom currents and or episodic turbidity currents and shows affinities to southern weddell sea sources winnowing of quartz rich sediments through intense bottom water formation in the southern weddell sea provides muddy suspensions enriched in quartz the influence of quartz rich suspensions moving within the weddell gyre contour current can be traced as far as the continental slope in the northwestern weddell sea in general the focusing of mud by currents significantly exceeds the relative and absolute contribution of ice rafted detritus beyond the shelves of the study area

paleomagnetic directional dispersion produced by plastic deformation in a thick miocene welded tuff southern nevada implications for welding temperatures two voluminous rhyolitic to quartz latitic ash flow sheets the tiva canyon and topopah spring members of the paintbrush tuff were erupted from the miocene claim canyon cauldron in southern nevada although lithologically similar these units differ greatly in their recording of the ancient geomagnetic field the reversely magnetized tiva canyon member yields remanent directions that are well grouped both within and between sites the normally magnetized topopah spring member however yields remanent directions that vary both laterally and vertically remanent directions from a 100 m thick section of nonwelded to partially welded topopah spring are well grouped precision parameter k 200 and give a mean direction d 293 i 69 that is probably a good approximation of the geomagnetic field at the time of emplacement and cooling in three 300 m thick sections of more densely welded tuff inclinations from the upper parts of the topopah spring are steep 70 but flatten with depth to about 20 and then steepen abruptly near the base of the unit in general the directional dispersion increases with the thickness of the section k 30 for sections that are about 300 m thick much of the directional variation in the topopah spring can be attributed to an inclination error produced by subblocking temperature rotation of the magnetic carriers during welding the possibility of subblocking temperature deformation in an ash flow sheet is enhanced by 1 high blocking temperature spectra of the primary magnetic phases 2 relatively low emplacement temperatures and 3 great stratigraphic thickness thermal demagnetization results from the topopah spring member indicate that welding may have continued to temperatures as low as 475 c in the basal vitrophyre of the ash flow sheet remanent directions from the tiva canyon member were unaffected by the welding process because this unit possesses significantly lower blocking temperatures and does not attain the great thicknesses of the topopah spring

co registration of lunar topographic models derived from chang e 1 selene and lro laser altimeter data based on a novel surface matchingmethod abstract various lunar digital topographic models dtms have been generated from the data collected from earlier and recent lunar missions there are usually inconsistencies among them due to differences in sensor configurations data acquisition periods and production techniques to obtain maximum value for science and exploration the multi source lunar topographic datasets must be co registered in a common reference frame only such an effort will ensure the proper calibration registration and analysis of the datasets which in turn will permit the full comparative and synergistic use of them this study presents a multi feature based surface matching method for the co registration of multiple lunar dtms that incorporates feature points lines and surface patches in surface matching to guarantee robust surface correspondence a combined adjustment model is developed for the determination of seven transformation parameters one scale factor three rotations and three translations from which the multiple dtms could be co registered the lunar dtms derived from the chang e 1 selene and lro laser altimeter data in the apollo 15 landing area and the sinus iridum area are examined in this study small offsets were found among the chang e 1 selene and lro dtms through experimental analysis the developed multi feature based method was proven able to effectively co register multiple lunar dtms the performances of the multi feature based surface matching method were compared with the point based method and the former was proven to be superior to the latter

past hydrographic and climatic changes in the subantarctic zone of the south atlantic the pleistocene record from odp site 1090 abstract pleistocene summer sea surface temperatures ssst have been reconstructed on a composite core section recovered in the subantarctic zone of the southern ocean from planktonic foraminifers applying the modern analog technique the composite consists of core ps2489 2 and the sections recovered at odp site 1090 and documents the last 1 83 ma three distinct climatic periods can be identified that mirror the pleistocene development of the southern ocean hydrography cold climatic conditions prevailed at 43 s during glacial as well as during interglacial periods during the early pleistocene 1 83 0 87 ma indicating a northward shift of isotherms that characterize the present day polar front zone by about 7 of latitude evidence shows a strong linkage between southern ocean and low latitude climate during that interval time between the mid pleistocene revolution ca 0 9 ma and the mid brunhes event ca 0 4 ma we observe higher amplitude fluctuations in the ssst between glacial and interglacial periods corresponding to the temperature range between the present polar front and subantarctic front these climatic variations have been related to changes in the northern hemisphere ice sheets the past 0 4 ma are characterized by strong ssst variations of up to 8 c between glacials and interglacials only during the climatic optima stages 11 3 9 3 7 5 7 1 5 5 and the early holocene ssst exceeded present ssst at the core locality 10 2 c although the carbonate dissolution record exhibits high variability during the pleistocene it can be shown that ssst estimates were not significantly biased the mid brunhes dissolution cycle as well as the mid pleistocene enhanced carbonate preservation appear to belong to a global long term variability in carbonate preservation

future of the west antarctic ice sheet a collapse of the antarctic ice sheets would raise the sea level by 5 meters and depending on how quickly it occurred would pose an enormous threat to global economy and ecology how stable are these volumes of ice in his perspective bindschadler discusses recent efforts to model the behavior of the west antarctic ice sheet on the basis of data on past ice sheet movement including results reported in the same issue by wingham et al consideration of these past data suggests that the ice sheets will remain stable for the next 4000 to 7000 years but an accurate assessment awaits more data on ice sheet history and better understanding of ice sheet dynamics

estimates of flow direction for calc alkaline welded tuffs and paleomagnetic data reliability from anisotropy of magnetic susceptibility measurements central san juan mountains southwest colorado abstract flow directions are estimated from the measurement of the magnetic fabric of 106 samples collected at 18 sites in four welded tuff units in the central san juan mountains of southern colorado the estimates assume that the tuffs generally flowed directly away from the extrusive vents and that the lineations of magnetic grains within the tuffs represent the flow direction at individual sites errors in the estimation may arise from topographic variation rheomorphism post emplacement mass flow within the tuff and other factors magnetic lineation is defined as the site mean anisotropy of magnetic susceptibility maximum azimuth a test on the flow directions for individual units is based on the projection of lineation azimuths and their intersection within or near the known source caldera for the tuff this test is positive for the four units examined paleomagnetic results for these tuffs are probably reliable indicators of the geomagnetic field direction in southwest colorado during the time 28 2 26 5 ma of emplacement

quantifying the opal belt in the atlantic and southeast pacific sector of the southern ocean by means of 230th normalization 1 a set of 114 samples from the sediment surface of the atlantic eastern pacific and western indian sectors of the southern ocean has been analyzed for 230th and biogenic silica maps of opal content th normalized mass flux and th normalized biogenic opal flux into the sediment have been derived significant differences in sedimentation patterns between the regions can be detected the mean bulk vertical fluxes integrated into the sediment in the open southern ocean are found in a narrow range from 2 9 g m 2 yr 1 eastern weddell gyre to 15 8 g m 2 yr 1 indian sector setting upper and lower limits to the vertically received fraction of open ocean sediments the silica flux to sediments of the atlantic sector of the southern ocean is found to be 4 2 1 4 1011 mol yr 1 just one half of the last estimate this adjustment represents 6 of the output term in the global marine silica budget

paleomagnetic and magnetic fabric studies of the san gaspar ignimbrite western mexico constraints on emplacement mode and source vents abstract paleomagnetic and magnetic fabric data for the 4 8 ma san gaspar ignimbrite one of the largest in western mexico are used to investigate the source vents emplacement mechanism and tectonics rock magnetic properties from distant parts of the ignimbrite are similar suggesting relatively homogeneous mineralogy of the unit isothermal remanence and continuous susceptibility temperature experiments point to low to medium ti titanomagnetites as the main magnetic carriers hysteresis ratio parameters of most samples fall in the pseudo single domain grain size region wasp waisted hysteresis loops were identified corresponding to high hcr hc values stepwise thermal and alternating field demagnetization shows that secondary components are completely removed below 20 mt or 400 c thereafter the characteristic component is isolated with small within site dispersion of mean direction 95

palaeomagnetism of welded pyroclastic fall scoriae at vulcano aeolian archipelago abstract this paper deals with the magnetic fabric and remanent magnetization of welded scoriae fall deposits four scoriae blankets were emplaced on vulcano aeolian islands from about 50 to 8 ka their detailed chronostratigraphic position has been debated in the literature and they have therefore been given a different interpretation in the reconstruction of the vulcano s eruptive history the aims of the study were a better understanding of the magnetic features of the scoriae fall deposits which have so far been given little attention and to set the chronostratigraphic relationships of the sampled deposits on the ground of their palaeomagnetic directions overall the magnetic properties of the four deposits are alike investigation of isothermal remanence and susceptibility versus temperature measurements point to low ti titanomagnetite as the main ferromagnetic mineral magnetic foliation is well developed moderately dispersed and in most cases close to horizontal lineation is either clustered or dispersed within the foliation plane stepwise thermal and alternating field demagnetization shows that secondary components are negligible in two units in the other two they are always completely removed in the first steps below 20 mt or 400 c thereafter the characteristic component chrm is clearly isolated and the within site dispersion of its direction is small 95 95 the palaeomagnetic results corroborate the hypothesis that the investigated scoriae deposits correspond to different volcanic phases related to recurrent arrival of mafic magma and show that those of spiaggia lunga and quadrara were produced during two distinct periods of volcanic activity with little time separation between them

topographic modeling and analysis of the landing site of chang e 3 on the moon abstract the chinese lunar probe chang e 3 carrying the jade rabbit lunar rover successfully landed in the sinus iridum area on the moon on december 14 2013 this paper presents the characterization activities that were done for the selection of the landing area including topographic modeling and analysis based on multisource lunar remote sensing data seven meter resolution chang e 2 imagery and lunar orbiter laser altimeter data were integrated to generate a digital elevation model dem with a resolution of 20 m for the entire sinus iridum landing area long baseline slopes were assessed according to this dem for all of this area lunar reconnaissance orbiter narrow angle camera images and 1 5 m resolution chang e 2 imagery were used to derive dems with higher resolution 4 m at several local regions within the sinus iridum landing area slope analyses at lander footprint scale 8 m were performed in these local regions craters were detected from the dems and the derived orthophotos and size frequency distributions were generated crater morphological statistics including the depth diameter ratios rim height diameter ratios and wall slopes were analyzed the results showed that the sinus iridum landing area is relatively flat most of the area has slopes of less than 15 the steeper slopes are mainly alongside craters and ridges the crater size frequency distribution is close to the equilibrium distribution the crater ages as indicated by their morphological statistics vary from mature to relatively fresh in different regions these topographic modeling and analysis results were used for strategic planning to identify the landing site for the chang e 3 and made a useful contribution to the success of the chang e 3 mission

multi level consistency tests in paleointensity determinations from the welded tuffs of the aso pyroclastic flow deposits abstract we have performed multi level consistency tests in an ltd dht shaw paleointensity study on the welded tuffs of the aso pyroclastic flow deposits aso 1 aso 2 aso 3 and aso 4 in order to obtain reliable mean paleointensities from each unit for a unit level consistency test we collected samples at three or more sites in each unit to enhance a site level consistency test we conducted paleointensity experiments on both whole rock and glass samples from the same sites thermal demagnetization curves of the samples indicate that the main magnetic carrier is titanium poor titanomagnetite to pure magnetite hysteresis parameters are different among the sites of the same units also differences in unblocking spectra and hysteresis parameters are recognized between the whole rock and glass samples from the same sites therefore these samples of various properties are expected to work effectively for multi level consistency test twenty nine out of 65 whole rock samples and 10 out of 31 glass samples gave accepted paleointensity results at the site level consistency of paleointensity estimates is observed with the exception of one site two paleointensity estimates from glass samples of a site of aso 4 are inconsistent and are excluded from further analysis at the unit level consistency or inconsistency among the sites is observed for individual units for aso 1 inconsistency in paleointensity estimates among the sites is observed and we can recognize more reliable results from two sites for aso 2 consistency in paleointensity estimates from glass and whole rock samples supports the acceptance of a site for aso 3 all paleointensity estimates from two sites are thought to be reliable because consistency between the site means of the two sites as well as site level consistency between the glass and whole rock samples for each site is recognized for aso 4 some difference among the sites is observed but there is no obvious reason to exclude the results of particular sites overall both the site level and unit level consistency checks work effectively in these samples which confirm the reliability of the paleointensity estimates or highlights the erroneous ones on the basis of the reliable paleointensity estimates unit mean values are obtained as 24 9 2 2 1 t n 9 for aso 1 22 9 1 6 t n 5 for aso 2 28 3 3 4 t n 10 for aso 3 and 40 1 6 2 t n 7 for aso 4

palaeointensity study of the hawaiian 1960 lava implications for possible causes of erroneously high intensities summary it is known that the hawaiian 1960 lava sometimes yields higher palaeointensities than the igrf 36 2 t in order to clarify the causes we have performed a comprehensive investigation of palaeointensity measurements on 19 cores from the lava according to various rock magnetic analyses they are classified into three groups with degrees of the deuteric oxidation in coe s version of the thellier method a significantly larger mean palaeointensity of 49 0 9 6 t n 17 was observed similar to previous studies these palaeointensities showed a dependence on the oxidation indices which can be explained by thermochemical remanent magnetization tcrm acquisition during the natural cooling stage of the lava although it is generally difficult to distinguish the tcrm from thermoremanent magnetization trm a lowtemperature demagnetization ltd treatment on nrm and trm in the thellier experiment seems to allow us to detect the influence of the tcrm on nrm another possible tool for tcrm detection is the double heating technique dht of the shaw method combined with ltd ltd dht shaw method it gave a better average of 39 4 7 9 t n 9 though the success rate was much lower most of the inappropriate results were screened by a combination of the double heating test the arm correction and the ltd treatment if two outliers are further excluded the average is improved to be 35 7 3 3 t n 7 which agrees well with the expected intensity the results of both methods emphasize the importance of taking and measuring samples from the parts of various oxidation degrees in a lava flow

similar glacial and interglacial export bioproductivity in the atlantic sector of the southern ocean multiproxy evidence and implications for glacial atmospheric co2 we present time series of export productivity proxy data including 230thex normalized deposition rates rain rates of 10be dissolution corrected biogenic ba and biogenic opal as well as authigenic u concentrations which are complemented by rain rates of total detrital fe and sea ice indicating diatom abundances from five sediment cores across the atlantic sector of the southern ocean covering the past 150 000 years the results suggest that 10be rain rates and authigenic u concentration cannot serve as quantitative paleoproductivity proxies because they have also been influenced by detrital particle fluxes in the case of 10be and bulk sedimentation rates sediment focussing and deep water oxygenation in the case of u the combined results of the remaining productivity proxies of this study rain rates of biogenic opal and biogenic ba in those sections without authigenic u and other previously published proxy data from the southern ocean 231pa 230th and nitrogen isotopes suggest that a combination of sea ice cover shallow remineralization depth and stratification of the glacial water column south of the present position of the antarctic polar front and possibly fe fertilization north of it have been the main controlling factors of export paleoproductivity in the southern ocean over the last 150 000 years an overall glacial increase of export paleoproductivity is not supported by the data implying that bioproductivity variations in the southern ocean are unlikely to have contributed to the major glacial atmospheric co2 drawdown observed in ice cores

international geomagnetic reference field the eleventh generation the eleventh generation of the international geomagnetic reference field igrf was adopted in december 2009 by the international association of geomagnetism and aeronomy working group v mod it updates the previous igrf generation with a definitive main field model for epoch 2005 0 a main field model for epoch 2010 0 and a linear predictive secular variation model for 2010 0 2015 0 in this note the equations defining the igrf model are provided along with the spherical harmonic coefficients for the eleventh generation maps of the magnetic declination inclination and total intensity for epoch 2010 0 and their predicted rates of change for 2010 0 2015 0 are presented the recent evolution of the south atlantic anomaly and magnetic pole positions are also examined