seeking phyllosilicates in thermal infrared data a laboratory and martian data case study 1 previous analyses of thermal emission spectrometer tes data produce results that could suggest a widespread distribution of phyllosilicate minerals over the surface of mars whereas studies of visible to near infrared vnir data indicate a more limited distribution we use vnir detections of phyllosilicates in the vicinity of the nili fossae to determine the spectral characteristics of phyllosilicate bearing material in the thermal infrared tir by investigating areas of vnir phyllosilicate detection in more detail we find that the phyllosilicate bearing material corresponds to spectral variation in thermal emission imaging system decorrelation stretched tir images and differences in infrared spectral shape that are consistent with but not uniquely attributable to mixtures of phyllosilicates and basalt phyllosilicate phases are modeled from tes data at abundances that average 5 over the region and at abundances near the 10 15 detection limit in our specific regions of interest deconvolution of numerical mixtures of phyllosilicate and basalt spectra indicates that these low abundances of phyllosilicates likely are not influenced by uncertainties greater than the 10 15 uncertainty of the method tes spectra and modeled abundances vary between the phyllosilicate bearing material and the surrounding region but this difference in composition cannot be attributed solely to the presence of phyllosilicates we believe the inconsistencies in phyllosilicate occurrence between tes and vnir analyses may be explained by the inclusion of phyllosilicates in the models of tes data as substitutes for poorly crystalline phases e g allophane not currently available in public infrared spectral libraries

a new contribution to the late quaternary tephrostratigraphy of the mediterranean aegean sea core lc21 tephra layers preserved in marine sediments can contribute to the reconstruction of volcanic histories and potentially act as stratigraphic isochrons to link together environmental records recent de velopments in the detection of volcanic ash tephra at levels where none is macroscopically visible so called crypto tephra have greatly enhanced the potential of tephrostratigraphy for synchronising environmental and archaeological records by expanding the areas over which tephras are found in this paper crypto tephra extraction techniques allow the recovery of 8 non visible tephra layers to add to the 9 visible layers in a marine sediment core lc21 from the se aegean sea to form the longest single core record of volcanic activity in the aegean sea using a novel shard specific methodology sources of the tephra shards are identified on the basis of their major and trace element single shard geochemistry by comparison with geochemical data from proximal mediterranean volcanic stratigraphies the results indicate that the tephra layers are derived from 14 or 15 separate eruptions in the last ca 161 ka bp 9 from santorini 2 or 3 from kos yali or nisyros 2 from the campanian province and one from pan telleria the attributions of these tephra layers indicate that 1 inter plinian eruptions from santorini may have produced regionally significant tephra deposits 2 marine tephrostratigraphies can provide unique and invaluable data to eruptive histories for island volcanoes and 3 tephra from both pantelleria and campania may be used to correlate marine records from the aegean sea to those from the tyrrhenian adriatic and ionian seas

a search for basaltic to intermediate glasses on mars assessing martian crustal mineralogy multiple datasets have demonstrated that the crust of mars is fundamentally basaltic however spectral libraries used to interrogate thermal infrared spectra of martian dark regions through spectral deconvolution have heretofore lacked mafic glasses despite the importance of amorphous phases or phases with amorphous like spectral signatures in martian mineralogy to establish the presence and importance of basaltic to intermediate glasses in martian lithologies we created five such glasses obtained their thermal infrared spectra and included the spectra in a library used to deconvolve nine regional thermal emission spectrometer spectra from mars we employed the nonnegative least squares nnls deconvolution method which yields deconvolved phase abundances and the uncertainties associated with those abundances the basaltic to intermediate glasses do not appear in the deconvolution solutions indicating they are not globally or regionally important phases because martian igneous or impact processes are capable of basaltic to intermediate glass formation the lack of such glasses in the deconvolved mineralogies suggests either the glasses did not form in detectable quantities or they or their signatures have been removed the masking or replacement of basaltic to intermediate glasses through alteration is supported by the appearance in the deconvolution solutions of amorphous phases e g silica rich glasses opal or phases with amorphous like spectral signatures e g clays zeolites that commonly form through aqueous alteration of mafic glasses the glasses may still be important to local scale thermal infrared studies given the basaltic nature of mars and the variety of local scale lithologies detected by various missions the regional mineralogies derived from the nnls deconvolution analysis divide into five statistically separable groups which provide insight into regional trends in mineralogy

metamorphism in the martian crust compositions of basaltic and ultramafic rocks analyzed by mars rovers and occurring as martian meteorites allow predictions of metamorphic mineral assemblages that would form under various thermophysical conditions key minerals identified by remote sensing roughly constrain temperatures and pressures in the martian crust we use a traditional metamorphic approach phase diagrams to assess low grade hydrothermal equilibrium assemblages basaltic rocks should produce chlorite actinolite albite silica accompanied by laumontite pumpellyite prehnite or serpentine talc only prehnite bearing assemblages have been spectrally identified on mars although laumontite and pumpellyite have spectra similar to other uncharacterized zeolites and phyllosilicates ultramafic rocks are predicted to produce serpentine talc and magnesite all of which have been detected spectrally on mars mineral assemblages in both basaltic and ultramafic rocks constrain fluid compositions to be h2o rich and co2 poor we confirm the hypothesis that low grade hydrothermal metamorphism affected the noachian crust on mars which has been excavated in large craters we estimate the geothermal gradient 20 c km 1 required to produce the observed assemblages this gradient is higher than that estimated from radiogenic heat producing elements in the crust suggesting extra heating by regional hydrothermal activity

the application of icp ms methods to tephrochronological problems pearce nicholas westgate j a perkins w t preece s j 2004 the application of icp ms methods to tephrochronological problems applied gechemistry 19 3 pp 289 322 rae2008

hydrated silicate minerals on mars observed by the mars reconnaissance orbiter crism instrument phyllosilicates a class of hydrous mineral first definitively identified on mars by the omega observatoire pour la mineralogie l eau les glaces et l activitie instrument preserve a record of the interaction of water with rocks on mars global mapping showed that phyllosilicates are widespread but are apparently restricted to ancient terrains and a relatively narrow range of mineralogy fe mg and al smectite clays this was interpreted to indicate that phyllosilicate formation occurred during the noachian the earliest geological era of mars and that the conditions necessary for phyllosilicate formation moderate to high ph and high water activity were specific to surface environments during the earliest era of mars s history here we report results from the compact reconnaissance imaging spectrometer for mars crism of phyllosilicate rich regions we expand the diversity of phyllosilicate mineralogy with the identification of kaolinite chlorite and illite or muscovite and a new class of hydrated silicate hydrated silica we observe diverse fe mg oh phyllosilicates and find that smectites such as nontronite and saponite are the most common but chlorites are also present in some locations stratigraphic relationships in the nili fossae region show olivine rich materials overlying phyllosilicate bearing units indicating the cessation of aqueous alteration before emplacement of the olivine bearing unit hundreds of detections of fe mg phyllosilicate in rims ejecta and central peaks of craters in the southern highland noachian cratered terrain indicate excavation of altered crust from depth we also find phyllosilicate in sedimentary deposits clearly laid by water these results point to a rich diversity of noachian environments conducive to habitability

a global view of martian surface compositions from mgs tes thermal emission spectrometer tes data from the mars global surveyor mgs are used to determine compositions and distributions of martian low albedo regions two surface spectral signatures are identified from low albedo regions comparisons with spectra of terrestrial rock samples and deconvolution results indicate that the two compositions are a basaltic composition dominated by plagioclase feldspar and clinopyroxene and an andesitic composition dominated by plagioclase feldspar and volcanic glass the distribution of the two compositions is split roughly along the planetary dichotomy the basaltic composition is confined to older surfaces and the more silicic composition is concentrated in the younger northern plains

revisiting the y 3 tephrostratigraphic marker a new diagnostic glass geochemistry age estimate and details on its climatostratigraphical context the y 3 tephra is a crucial stratigraphic marker within the central mediterranean region that falls close to the marine isotope stage 3 2 transition and a cooling event proposed as a correlative of the north atlantic heinrich stadial 3 hs3 consequently this tephra offers great potential to assess any leads and lags in environmental responses to this abrupt climatic transition new grain specific glass analysis empa and la icp ms of the type locality y 3 tephra recorded in the ionian sea confirms its origin from campi flegrei cf but reveals that it is compositionally different from the previously suggested proximal equivalent the vra eruptive unit verdolino valley cf consequently the 40ar 39ar age of the vra should not be exported distally to the y 3 tephra instead we propose a new robust age for the y 3 tephra following its identification in the tenaghi philippon sedimentary record ne greece a bayesian based 14c age model from tenaghi philippon provides a distal age of 28 680 29 420 cal yrs bp for the y 3 tephra the identification of this tephra in ne greece markedly extends its known eastern dispersal whilst its stratigraphic position falls within the latter part of a period of low tree pollen percentages related to dry stadial conditions this new age and environmental context suggest that this marker postdates the onset of hs3 in the eastern mediterranean region by 2300 years

basaltic andesite altered basalt and a tes based search for smectite clay minerals on mars 1 the global scale surface type 2 unit first identified with the mars global surveyor thermal emission spectrometer tes remains enigmatic competing hypotheses suggest that it represents either basaltic andesite or some form of altered basalt rich in dioctahedral smectite clay minerals and or spectrally similar amorphous silica phases common dioctahedral smectites contain a diagnostic feature in a portion of tes spectra that has been excluded in previous studies because of atmospheric co2 absorption we exploit the relative transparency of this spectral region to develop two indices that in tandem distinguish between certain smectites and amorphous phases smectites are not detected in northern lowlands type 2 settings consistent with other datasets but the case for primary or secondary amorphous silica phases is strengthened separately one index reveals an abundance of isolated type 2 occurrences in the southern high latitudes 50 associated with dunes the other shows olivine concentrations between 40 and 30

identification of quartzofeldspathic materials on mars 1 a unique spectral component has been identified near and on the central peaks of two 30 km diameter craters in northern syrtis major these exposures are clearly visible in thermal emission imaging system themis color radiance images as well as themis and thermal emission spectrometer tes surface emissivity data both tes and themis data indicate the presence of increased 1050 1250 cm 1 8 9 5 m absorption compared to the surrounding basaltic plains and tes data also display other absorptions at 400 470 and 800 cm 1 25 20 and 12 m consistent with the presence of quartz ratio and isolated central peak spectral unit spectra match laboratory emissivity spectra of granitoid rocks composed primarily of quartz and plagioclase feldspar deconvolution results also indicate that the surface contains quartz and feldspar in addition to a high si glass and or sheet silicate component because central peak materials are brought up from depth during the cratering event the association of the quartzofeldspathic mineralogy with the central peaks of the craters indicates that the quartz bearing material was excavated from depth the occurrence in the two adjacent craters may imply a granitoid pluton of considerable extent a plausible formation mechanism for this relatively silicic material may be similar to that of terrestrial trondhjemites which do not require plate tectonics the rarity of the exposures implies that the process that formed the granitoid composition was probably not widespread the presence of quartz bearing material on mars indicates that mechanisms that produce highly differentiated magmas have been present and extends the diversity of surface compositions identified

refining the late quaternary tephrochronology for southern south america using the laguna potrok aike sedimentary record abstract this paper presents a detailed record of volcanism extending back to 80 kyr bp for southern south america using the sediments of laguna potrok aike icdp expedition 5022 potrok aike maar lake sediment archive drilling project pasado our analysis of tephra includes the morphology of glass the mineral componentry the abundance of glass shards lithics and minerals and the composition of glass shards in relation to the stratigraphy firstly a reference database of glass compositions of known eruptions in the region was created to enable robust tephra correlations this includes data published elsewhere in addition to new glass shard analyses of proximal tephra deposits from hudson eruption units h 1 and h 2 aguilera a 1 reclus r 1 r 2 3 mt burney mb 1 mb 2 mb x mb 1910 and historical lautaro viedma deposits the analysis of the ninety four tephra layers observed in the laguna potrok aike sedimentary sequence reveals that twenty five tephra deposits in the record are the result of primary fallout and are sourced from at least three different volcanoes in the austral andean volcanic zone mt burney reclus lautaro viedma and one in the southernmost southern volcanic zone hudson one new correlation to the widespread h 1 eruption from hudson volcano at 8 7 8 6 9 0 cal ka bp during the quaternary is identified the identification of sixty five discrete deposits that were predominantly volcanic ashes glass and minerals with subtle characteristics of reworking in addition to three likely reworked tephra and one unknown layer indicates that care must be taken in the analysis of both visible and invisible tephra layers to decipher their emplacement mechanisms

stress and pore pressure changes due to sand compaction pile installation in soft clay this paper presents centrifuge model data and describes a semi empirical approach to predict short term total radial stress and pore pressure changes around sand compaction piles installed in soft marine clays comparison of the measured changes in radial stress and pore pressure with plane strain cavity expansion theory shows that the latter gives a reasonably good estimate at large depth for the entire installation process and for the peak stress measured during casing jack in but not for the residual stress after casing jack in however deviation from plane strain cavity expansion theory was noted at shallow depths to account for the effect of the ground surface a plane stress cavity expansion theory was proposed for the shallow zones which assumes constant vertical overburden stress the establishment of the two limits formed by the plane strain and plane stress theories allows semi empirical relations to be established by fitting to the data these semi empirical relations allow the post install

tephrochronology of core prad 1 2 from the adriatic sea insights into italian explosive volcanism for the period 200 80 ka core prad 1 2 located on the western flank of the mid adriatic deep was investigated for tephra content within the part of the sequence assigned on biostratigraphic and sapropel layer stratigraphy to mis 5 and 6 ca 80 200 ka bp a total of 11 discrete tephra layers are identified 8 visible and 3 cryptotephra layers 235 geochemical measurements obtained from individual glass shards using wds epma enabled 8 of the 11 tephras to be correlated to known eruption events 5 of which are represented in the lago grande di monticchio lgdm regional tephra archive sequence three of these layers are recognised ultra distally for the first time extending their known distributions approximately 210 km further north the results provide an independent basis for establishing an age depth profile for the mis 5 6 interval in the prad 1 2 marine record this approach allowed age estimates to be interpolated for the tephra layers that could not be correlated to known events it also provides an independent test of and support for the broad synchroneity of sapropel equivalent s e events in the adriatic sea with the better developed sapropel layers of the eastern mediterranean proposed by piva et al 2008a

mid pleistocene silicic tephra beds in the auckland region new zealand their correlation and origins based on the trace element analyses of single glass shards abstract the trace element composition of individual glass shards from twelve distinct mid pleistocene silicic tephra beds from the auckland region new zealand has been determined by laser ablation la icp ms analysis this is the first application of such data to tephra correlation studies in new zealand these analyses support earlier major element based correlations between three surface sections oruarangi and okariha at port waikato and st kentigern s at east auckland and a long core patiki road west auckland the correlations provide a higher resolution record of taupo volcanic zone tvz activity than is preserved in more proximal deposits where burial and erosion obscure much of the volcanic record a combination of major and trace element analysis enables the correlation of three units exposed in the auckland region with their proximal equivalents ignimbrites from the tvz namely deposits associated with 1 the ongatiti ignimbrite 1 21 0 04 ma 2 an un named post ahuroa pre unit e ignimbrite sample ut1274 from the rocky hill section king country and 3 the unit e ignimbrite 1 ma combined major and trace element data show a marked evolution in magma chemistry with the large ongatiti and unit e ignimbrite eruptions occurring after a change in composition caused by replenishment reactivation of the magma chamber changes in magma chemistry between these deposits resulted from a combination of assimilation of metasedimentary country rocks and periods of fractional crystallisation of a plagioclase dominated assemblage trace element data and the wider dispersal of the silicic tephras in the auckland region suggests that they are all sourced from the mangakino volcanic centre mvc in the tvz this study illustrates for the first time in a new zealand context the potential for correlating tephra deposits using single glass shard trace element chemistry

toward a comprehensive upper quaternary tephra and ignimbrite stratigraphy in new zealand using electron microprobe analysis of glass shards abstract new zealand quaternary marine and terrestrial sequences contain numerous tephras or volcanic ash horizons that are the distal correlatives of voluminous welded ignimbrite sheets erupted from central north island electron microprobe analyses of glass shards from the distal tephras demonstrate their homogeneity and are shown to identify each tephra examined by matching tephras from stratigraphically controlled sequences the first comprehensive tephra stratigraphy spanning from 50 000 to 700 000 yr ago and covering the new zealand region is advanced analyses on glass shards from the unwelded base of ignimbrite sheets are comparable to the distal tephra analyses and allow correlation between ignimbrites and to the distal tephras the better exposed tephra record constrains the number of separate eruptive events and the stratigraphy of the ignimbrites both of which were previously confused by lack of outcrop samples from pumiceous marine sediments were found to contain two or more chemically distinct populations of glass the pumice is in cross bedded sands or sand lenses within conglomerate attesting to a shallow high energy environment where reworking could occur however each glass population could be matched to older known tephras

spectral evidence for weathered basalt as an alternative to andesite in the northern lowlands of mars mineral abundances derived from the analysis of remotely sensed thermal emission data from mars have been interpreted to indicate that the surface is composed of basalt surface type 1 and andesite surface type 2 1 the global distribution of these rock types is divided roughly along the planetary dichotomy which separates ancient heavily cratered crust in the southern hemisphere basalt from younger lowland plains in the north andesite 1 but the existence of such a large volume of andesite is difficult to reconcile with our present understanding of the geological evolution of mars here we reinterpret martian surface rock lithologies using mineral abundances from previous work1 and new mineralogies derived from a spectral end member set representing minerals common in unaltered and low temperature aqueously altered basalts our results continue to indicate the dominance of unaltered basalt in the southern highlands but reveal that the northern lowlands can be interpreted as weathered basalt as an alternative to andesite the coincidence between locations of such altered basalt and a suggested northern ocean basin implies that lowland plains material may be composed of basalts weathered under submarine conditions or weathered basaltic sediments transported into this depocentre

trace element composition of single glass shards in distal minoan tephra from sw turkey volcanic glass from the seventeenth century bc c 3600 bp minoan eruption of santorini thera has been recovered from a 4 cm thick tephra deposit at golhisar golu a small lake in sw turkey analysis of single grains of this glass by laser ablation inductively coupled plasma mass spectrometry la icp ms provides for the first time an accurate determination of the trace element composition of the juvenile glass component of this eruption free from contaminants such as phenocrysts or detrital material individual glass shards 150 m show a large degree of variation in their trace element composition indicative of substantial small scale compositional heterogeneity in the magma this is a result of the proximity of crystallizing phases and provides insights into the chemical evolution of the minoan magma the range of elemental compositions displayed by individual glass shards combined with the consistency of many trace element ratios are characteristics of the minoan glass these features provide a trace element signature for the minoan tephra which will be of value in stratigraphic correlation across the eastern mediterranean

thermal emission spectroscopy of the silica polymorphs and considerations for remote sensing of mars 1 the possible existence of silica rich rocks on mars requires consideration of all of the candidate forms of silica that might exist there we synthesized coesite and cristobalite and obtained natural samples of tridymite opal a and opal ct the thermal emission spectra of these silica phases were analyzed and related to their crystal structure and crystallinity structural differences between the polymorphs result in unique spectral character and the degree and type of crystal ordering in opal ct results in cristobalite or tridymite like spectral features these spectra will be useful for analysis of thermal emission spectrometer tes data from mars while silica polymorphs are not modeled in deconvolution of the two main tes surface type spectra this does not preclude the possible detection of local abundances of these minerals on mars spectral detection of silica phases on mars would have implications for the volcanic and alteration history of the planet

mineralogy and stratigraphy of phyllosilicate bearing and dark mantling units in the greater mawrth vallis west arabia terra area constraints on geological origin 1 analyses of mro crism images of the greater mawrth vallis region of mars affirm the presence of two primary phyllosilicate assemblages throughout a region 1000 1000 km these two units consist of an fe mg phyllosilicate assemblage overlain by an al phyllosilicate and hydrated silica assemblage the lower unit contains fe mg smectites sometimes combined with one or more of these other fe mg phyllosilicates serpentine chlorite biotite and or vermiculite it is more than 100 m thick and finely layered at meter scales the upper unit includes al smectite kaolin group minerals and hydrated silica it is tens of meters thick and finely layered as well a common phyllosilicate stratigraphy and morphology is observed throughout the greater region wherever erosional windows are present this suggests that the geologic processes forming these units must have occurred on at least a regional scale sinuous ridges interpreted to be inverted channels and narrow channels cut into the upper clay bearing unit suggesting that aqueous processes were prevalent after and possibly during the deposition of the layered units we propose that layered units may have been deposited at mawrth vallis and then subsequently altered to form the hydrated units the fe mg phyllosilicate assemblage is consistent with hydrothermal alteration or pedogenesis of mafic to ultramafic rocks the al phyllosilicate hydrated silica unit may have formed through alteration of felsic material or via leaching of basaltic material through pedogenic alteration or a mildly acidic environment these phyllosilicate bearing units are overlain by a darker relatively unaltered and indurated material that has probably experienced a complex geological history

40ar 39ar dating of the thorsmork ignimbrite and icelandic sub glacial rhyolites abstract robust correlation of paleoclimatic archives e g marine sediments ice speleothems necessitates an increase of the number of independent and accurately dated stratigraphic markers using numerical methods icelandic rhyolitic volcanism has a strong chronological interest because these products are found as tephra in the north atlantic marine archives as well as in greenland ice cores in this study we have dated using the 40ar 39ar method subglacial rhyolites of the tindfjallajokull kerlingarfjoll and torfajokull volcanoes which are the main sources of rhyolitic tephra identified in marine and glaciological records the thorsmork ignimbrite tindfjallajokull which correlates with the rhyolitic component ii rhy 1 of the north atlantic ash zone ii naaz ii layer is dated at 55 6 2 4 ka an age that agrees with the ones given by the ice core chronologies gicc05 55 4 1 2 ka the eruptions of rau fossafjoll and fannborg are respectively dated at 77 0 3 0 ka and 149 3 3 4 ka these new ages along with the published ones confirm as already concluded by flude et al 2010 that there is no clear evidence at least at the latitude of iceland that climate warming is the main mechanism that triggered rhyolitic eruptions combining major and trace element compositions with our new age determinations it appears that the rau fossafjoll and the snaefell rhyolitic eruptions have not yet been discovered in marine sediment cores nevertheless given the accuracy and precision of our dating these rhyolitic eruptions have the potential to become chronostratigraphic markers once tephra shards corresponding to these eruptions are discovered in ice and or marine sediment records the fannborg eruption might be recorded in the marine core link 16 during mis 6 prior to the transition to mis5e

effects of pure silica coatings on thermal emission spectra of basaltic rocks considerations for martian surface mineralogy 1 on mars silica derived from chemical weathering could precipitate to coat rocks and particles we suggest that rock coatings of secondary amorphous silica may account for a widespread martian surface spectral unit previously modeled as andesite or weathered basalt in a laboratory study we investigated the effects of synthetic silica coatings on thermal infrared tir spectroscopic measurements secondary amorphous silica is spectrally similar to silicate glass and clay spectra used in previous spectroscopic models silica coating and substrate spectra combine nonlinearly to produce a composite spectrum of a coated rock silica coatings 10 m thick effectively mask the spectral contribution of a silicate substrate therefore the capability of volumetrically small amounts of silica present as thin coatings on rocks should be considered when seeking explanations for spectral variability of martian surface materials

icelandic volcanic ash from the late glacial open air archaeological site of ahrenshoft la 58 d north germany abstract cryptotephra of icelandic origin from the open air archaeological site of ahrenshoft la 58 d kr nordfriesland schleswig holstein northern germany overlies a late glacial havelte lithic assemblage hitherto dated by 14 c and biostratigraphy to the earliest part of the late glacial interstadial gi 1e to gi 1c 3 peaks in ash shards are observed in two profiles major and minor element geochemistry indicates volcanic ash originating in the katla system precise correlation to previously described tephra is uncertain due to overlapping chemical characteristics the ahrenshoft 14 c determinations litho and bio stratigraphy encompass a broad age span for the cryptotephra bearing sediments from the end of the allerod to the preboreal the most plausible volcanic eruption correlates are the vedde ash younger dryas already known from the european mainland tephra af555 late younger dryas and the suduroy tephra preboreal boreal hitherto recorded only in the north atlantic region these three ash horizons have been dated to respectively 12 171 57 yr b2k in the ngrip ice core c 11 500 cal bp in scotland and c 8000 cal bp by radiocarbon from the faroe isles ongoing research on deposits from the type sites for the tephra layers may in the future differentiate these markers leading to better discrimination of the chemistries and a resolution of this question

occurrences of possible hydrated sulfates in the southern high latitudes of mars abstract hydrated sulfate minerals record the history of water and habitable environments on mars yet prior studies of them have neglected a vast region surrounding the planet s south pole some of the few sulfates reported there are localized to putative ancient volcanoes that may have erupted under an ice sheet possibly forming sulfates via hydrothermal alteration alternatively sulfates may have formed more recently from sunlight causing minor melting of polar ices and the weathering of embedded dust particles a process thought to explain the sulfates found near mars north pole to test these hypotheses we searched for southern high latitude sulfates using the compact reconnaissance imaging spectrometer for mars crism on the mars reconnaissance orbiter mro focusing on regions that include putative volcanoes or geologically similar landforms in 217 targeted images we used spectral parameters to identify regions of interest from which we extracted spectra the spectra were then visually compared to laboratory spectra to identify possible hydrated mineral constituents in this paper we present spectra from 16 of the images and statistics derived from the full set of 217 along with spectra from one mapping tile we find that hydrated sulfates are found throughout the southern high latitudes suggesting a ubiquitous process for hydrated mineral formation and or the relocation of hydrated minerals due to a long history of impacts aeolian transport weathering and periglacial processes

mineralogy of the nili fossae region with omega mars express data 2 aqueous alteration of the crust 1 nili fossae is a region with fresh exposures of old material omega spectral data have revealed a strong diversity of minerals in the nili fossae region including mafic minerals and phyllosilicates phyllosilicates are found to be primarily fe rich smectites a type of clay minerals these phyllosilicates are observed only on the noachian crust in four types of locations three are without any signatures other than phyllosilicates on 1 smooth layered deposits 2 massive exhumed material and 3 crater ejecta and one type of location is associated with olivine 4 over an altered mafic unit this diversity suggests a widespread liquid water activity and a variety of alteration processes the formation of phyllosilicates underwent considerable reduction if not cessation by the time of formation of syrtis major lava flows in the hesperian period phyllosilicates are spatially and chronologically disconnected from the fluvial and depositional landforms observed in the nili fossae region observations suggest that these landforms formed after the extensive formation of phyllosilicates during short periods of time and or temperatures close to freezing

high level triggers for explosive mafic volcanism albano maar italy abstract colli albani is a quiescent caldera complex located within the roman magmatic province rmp italy the recent via dei laghi phreatomagmatic eruptions led to the formation of nested maars albano maar is the largest and has erupted seven times between ca 69 33 ka the highly explosive nature of the albano maar eruptions is at odds with the predominant relatively mafic sio 2 48 52 wt foiditic k 2 o 9 wt composition of the magma the deposits have been previously interpreted as phreatomagmatic however they contain large amounts up to 30 vol of deep seated xenoliths skarns and all pre volcanic subsurface units all of the xenoliths have been excavated from depths of up to 6 km rather than being limited to the depth at which magma and water interaction is likely to have occurred suggesting an alternative trigger for eruption high precision geochemical glass and mineral data of fresh juvenile magmatic clasts from the small volume explosive deposits indicate that the magmas have evolved along one of two evolutionary paths towards foidite or phonolite the foiditic melts record ca 50 mixing between the most primitive magma and ca rich melt late stage prior to eruption a major result of our study is finding that the generation of ca rich melts via assimilation of limestone may provide storage for significant amounts of co 2 that can be released during a mixing event with silicate magma differences in melt evolution are inferred as having been controlled by variations in storage conditions residence time and magma volume

laser ablation inductively coupled plasma mass spectrometry and tephras a new approach to understanding arc magma genesis the development of laser ablation inductively coupled plasma mass spectrometry has revolutionized the analysis of tephras by providing 1 an efficient and precise method for determining abundances of a wide variety of trace elements at low concentrations in individual glass shards and 2 assessment of geochemical heterogeneities within individual ash horizons this development is important for petrogenetic studies of intraoceanic arc systems where tephras provide the most complete temporal record of magmatism results from the izu bonin and mariana arc systems indicate that despite close geographical proximity and similar tectonic evolution they contrast strongly in terms of geochemical evolution since 35 ma whereas the mariana tephras have exceptional compositional diversity ranging from low k oligocene to high k miocene and subsequently medium k compositions pliocene quaternary the izu bonin arc has been dominated by low k compositions throughout the mariana increases in k are paralleled by increases in abundances of incompatible trace elements and by increased values of diagnostic ratios e g nb yb and th yb regarded as monitors of potential mantle source fertility the relative uniformity of nb yb and nb zr ratios in izu bonin tephras indicates that cyclic processes of backarc basin development and mantle depletion do not necessarily induce large scale temporal geochemical variations in the associated arc temporal variability within the mariana arc and its divergence from the izu bonin arc ca 13 ma can be traced to a major injection of subducted sediment in the mariana system at this time

an approach to evaluation of field cptu dissipation data in overconsolidated fine grained soils dissipation of excess pore pressures during piezocone testing in firm to stiff overconsolidated fine grained soils provides data curves that cannot be interpreted using published theoretical soluti

the importance of independent chronology in integrating records of past climate change for the 60 8 ka intimate time interval this paper provides a brief overview of the most common dating techniques applied in palaeoclimate and palaeoenvironmental studies including four radiometric and isotopic dating methods radiocarbon 230th disequilibrium luminescence cosmogenic nuclides and two incremental methods based on layer counting ice layer varves for each method concise background information about the fundamental principles and methodological approaches is provided we concentrate on the time interval of focus for the intimate integrating ice core marine and terrestrial records community 60 8 ka this dating guide addresses palaeoclimatologists who aim at interpretation of their often regional and local proxy time series in a wider spatial context and therefore have to rely on correlation with proxy records obtained from different archives from various regions for this reason we especially emphasise scientific approaches for harmonising chronologies for sophisticated and robust proxy data integration in this respect up to date age modelling techniques are presented as well as tools for linking records by age equivalence including tephrochronology cosmogenic 10be and palaeomagnetic variations finally to avoid inadequate documentation of chronologies and assure reliable correlation of proxy time series this paper provides recommendations for minimum standards of uncertainty and age datum reporting

early last interglacial ocean warming drove substantial ice mass loss from antarctica the future response of the antarctic ice sheet to rising temperatures remains highly uncertain a useful period for assessing the sensitivity of antarctica to warming is the last interglacial lig 129 to 116 ky which experienced warmer polar temperatures and higher global mean sea level gmsl 6 to 9 m relative to present day lig sea level cannot be fully explained by greenland ice sheet melt 2 m ocean thermal expansion and melting mountain glaciers 1 m suggesting substantial antarctic mass loss was initiated by warming of southern ocean waters resulting from a weakening atlantic meridional overturning circulation in response to north atlantic surface freshening here we report a blue ice record of ice sheet and environmental change from the weddell sea embayment at the periphery of the marine based west antarctic ice sheet wais which is underlain by major methane hydrate reserves constrained by a widespread volcanic horizon and supported by ancient microbial dna analyses we provide evidence for substantial mass loss across the weddell sea embayment during the lig most likely driven by ocean warming and associated with destabilization of subglacial hydrates ice sheet modeling supports this interpretation and suggests that millennial scale warming of the southern ocean could have triggered a multimeter rise in global sea levels our data indicate that antarctica is highly vulnerable to projected increases in ocean temperatures and may drive ice climate feedbacks that further amplify warming

using themis data to resolve the discrepancy between crism omega and tes modeled phyllosilicate abundance in mawrth vallis abstract we explore the effects of spatial resolution on the detectability of phyllosilicates in the thermal infrared dataset from the mars global surveyor thermal emission spectrometer tes data from the mars odyssey thermal emission imaging system themis instrument is used to resolve spatial resolution driven discrepancies between detection of phyllosilicates in the infrared and visible near infrared wavelength range the 100 m pixel spatial resolution offered by themis even with its limited spectral resolution significantly improves the likelihood of phyllosilicate detection furthermore spectral unit mapping techniques provide the first phyllosilicate abundance maps of the mawrth vallis phyllosilicate bearing units which indicate phyllosilicate abundances of 50 with heterogeneous spatial distributions derived abundances are used to evaluate the proposed formation mechanisms for phyllosilicates in this region and are found to be consistent with intermediate weathering of mafic primary material

mineralogical characterization of mars science laboratory candidate landing sites from themis and tes data abstract data from the mars global surveyor thermal emission spectrometer tes and the mars odyssey thermal emission imaging system themis instruments are used to assess the mineralogic and dust cover characteristics of landing regions proposed for the mars science laboratory msl mission candidate regions examined in this study are eberswalde crater gale crater holden crater mawrth vallis miyamoto crater nili fossae trough and south meridiani planum compositional units identified in each region from tes and themis data are distinguished by variations in hematite olivine pyroxene and high silica phase abundance whereas no units are distinguished by elevated phyllosilicate or sulfate abundance though phyllosilicate minerals have been identified in all sites using near infrared observations these minerals are not unambiguously detected using either tes spectral index or deconvolution analysis methods for some of the sites small phyllosilicate outcrop sizes relative to the tes field of view likely hinder phyllosilicate mineral detection porous texture and or small particle size 15 possibly up to 40 of a high silica phase such as amorphous silica or zeolite high silica phase abundance over phyllosilicate bearing surfaces in mawrth vallis is higher than that of surrounding surfaces by 10 15 with the exception of these high silica surfaces in mawrth vallis regions examined in this study exhibit similar bulk mineralogical compositions to that of most low albedo regions on mars the msl scientific payload will thus be able to provide important information on surface materials typical of low albedo regions in addition to investigating the origin of phyllosilicate and or sulfate deposits with the exception of gale crater all of the landing sites have relatively low dust cover compared to classic high albedo regions tharsis arabia and elysium and to previous landing sites in gusev crater utopia planitia and chryse planitia

the role of cryptotephra in refining the chronology of late pleistocene human evolution and cultural change in north africa abstract sites in north africa hold key information for dating the presence of homo sapiens and the distribution of middle stone age msa middle palaeolithic mp and later stone age lsa cultural activity in the late pleistocene here we present new and review recently published tephrochronological evidence for five cave sites in north africa with long msa mp and lsa cultural sequences four tephra horizons have been identified at the haua fteah cyrenaica libya they include cryptotephra evidence for the campanian ignimbrite ci eruption dating to 39 ka that allows correlation with other palaeolithic sequences in the eastern mediterranean and as far north as russia cryptotephra have also been recorded from the moroccan sites of taforalt rhafas and dar es soltane 1 at taforalt the geochemical composition suggests a provenance in the azores while examples from sodmein egypt appear to derive from central anatolia and another unknown source in these latter examples chemical compositional data from relevant proximal volcanic centres is currently lacking so the identification of tephra in layers of known age and cultural association provides the first reliable age determinations for distal volcanic events and their geographical extent the future potential for tephrochronological research in north africa is also discussed

volcanism and the greenland ice cores the tephra record abstract in recent years increased awareness of the considerable potential offered by tephrochronology in palaeoclimatic studies has fuelled a renewed interest in the tephra record preserved within the greenland ice cores this renewal has occurred in tandem with the development of continuous flow analysis techniques which provide high resolution volcanic aerosol records these chemical records are of considerable value for identifying tephra horizons composed of glass shards and also provide the basis for a new high precision ice core timescale thus allowing ages to be assigned to volcanic events tephra horizons of glass shards in the ice cores play a critical role for 1 testing and building chronological frameworks for the ice cores and other sequences 2 synchronising disparate palaeoclimatic sequences and testing phase relationships 3 atmospheric pathway reconstruction and 4 verifying the source of volcanic aerosol peaks here we review the results of over 25 years of research into tephra horizons in the grip gisp2 and ngrip cores we provide high precision ages for horizons based on recently developed timescales and draw together geochemical characterisations of the products of 45 volcanic events deposited on the greenland ice sheet and identified in the cores there is a clear disparity between the number of volcanic aerosol peaks and the number of tephra horizons of glass shards identified thus far however this synthesis highlights the critical role of the greenland ice cores firstly in the reconstruction of the history of icelandic volcanic eruptions and secondly the considerable value of some tephra horizons in facilitating the correlation of these key climatic archives to north atlantic marine sequences other noteworthy issues include the potential of these cores to preserve tephra horizons from more distal volcanic sources such as north america to resolve the debate surrounding the thera eruption and the observation that some tephra horizons are preserved within the ice without coeval volcanic aerosol signals

age and geochemistry of tephra layers from ischia italy constraints from proximal distal correlations with lago grande di monticchio unraveling the eruptive history of the island of ischia southern italy is problematic due to its burial caldera collapse resurgent uplift and erosion here we present new major and trace element glass data for 39 75 ka proximal tephra deposits including those of the caldera forming monte epomeo green tuff megt eruption correlations with the distal tephra archive preserved at lago grande di monticchio lgdm are used to constrain the timing of as yet undated eruptive events out of 13 lgdm tephras analysed from the 39 104 ka time window glass geochemical data show that all are compositionally consistent with the explosive volcanic eruptions of ischia whilst 5 of them can be correlated with specific proximal deposits pre megt pyroclastic sequences comprise three compositional groups these groups occur repeatedly in sucessive eruptions proximal distal correlations indicate that the porticello eruption occurred at 59 2 ka and the tisichiello eruption probably occurred at 76 3 ka the megt eruption is correlated with lgdm tm 19 which has been directly dated at 55 2 ka post megt tephras form compositional groups that overlap with the pre megt but are displaced to lower feo and tio2 and lower incompatible element contents proximal distal correlations indicate that the schiappone and pietre rosse eruptions occurred at 50 6 2 0 ka and 45 6 ka respectively tephra from the megt eruption span a wide compositional range broadly overlapping the three pre megt compositional groups but are displaced to higher nd and y and contain an additional less evolved glass population glass geochemistry is used to recognise and confirm distal equivalents of the megt at lgdm tm 19 and in the ionian y 7 adriatic prad 1870 and tyrrhenian c 18 md 28 seas distal occurences of megt tephra define a dispersal axis to the south southeast and are found as far as 540 km from ischia making the megt one of the most widely dispersed late quaternary pyroclastic deposit erupted in the campanian region we estimate a volume of approximately 40 km3 for the fallout portion of the megt pyroclastic sequence on the basis of proximal and distal deposit thicknesses

structural and spectroscopic changes to natural nontronite induced by experimental impacts between 10 and 40 gpa many phyllosilicate deposits remotely detected on mars occur within bombarded terrains shock metamorphism from meteor impacts alters mineral structures producing changed mineral spectra thus impacts have likely affected the spectra of remotely sensed martian phyllosilicates we present spectral analysis results for a natural nontronite sample before and after laboratory generated impacts over five peak pressures between 10 and 40 gpa we conducted a suite of spectroscopic analyses to characterize the sample s impact induced structural and spectral changes nontronite becomes increasingly disordered with increasing peak impact pressure every infrared spectroscopic technique used showed evidence of structural changes at shock pressures above 25 gpa reflectance spectroscopy in the visible near infrared region is primarily sensitive to the vibrations of metal oh and interlayer h2o groups in the nontronite octahedral sheet midinfrared mir spectroscopic techniques are sensitive to the vibrations of silicon and oxygen in the nontronite tetrahedral sheet because the tetrahedral and octahedral sheets of nontronite deform differently impact driven structural deformation may contribute to differences in phyllosilicate detection between remote sensing techniques sensitive to different parts of the nontronite structure observed spectroscopic changes also indicated that the sample s octahedral and tetrahedral sheets were structurally deformed but not completely dehydroxylated this finding is an important distinction from previous studies of thermally altered phyllosilicates in which dehydroxylation follows dehydration in a stepwise progression preceding structural deformation impact alteration may thus complicate mineral specific identifications based on the location of oh group bands in remotely detected spectra this is a key implication for martian remote sensing arising from our results

in situ lateral stress coefficient k0 from shear wave velocity measurements in soils abstractthe at rest lateral stress coefficient k0 is an important soil parameter in geotechnical design problems and yet it is quite elusive in our ability to assess its value either by laboratory or in situ tests in this study an innovative geophysics approach toward the evaluation of the in situ k0 profile with depth is obtained by using small strain stiffness anisotropy ratio g0 hh g0 vh in soils the newly proposed k0 equation is derived from a database compiled from 12 test sites which have direct k0 measurements as procured from field tests either self boring pressuremeters sbp or total stress cells tsc and or laboratory triaxial tests instrumented consolidometers and or suction measurements the data show a strong relationship between the overconsolidation difference ocd p vo and stiffness anisotropy ratio thus enabling a k0 assessment in clays silts and sands

marine continental tephra correlations volcanic glass geochemistry from the marsili basin and the aeolian islands southern tyrrhenian sea italy abstract major minor and trace element analysis of volcanic glass in proximal and distal it is evident that correlation of proximal continental and distal marine tephras at a high level of confidence requires a full complement of major minor and trace element data in conjunction with considerations of the mineralogy and morphology of juvenile deposits these data help define petrological lineages such that precise provenance can be established whilst a precise proximal distal match must be based on identical major minor and trace element concentrations it is clear that resurgent activity from a single volcano can produce magmas with identical compositions in such cases stratigraphic relationships must complement any geochemical study occasionally proximal stratigraphies may be unrepresentative of the complete eruptive history because of a lack of exposure due to burial by more recent effusive and explosive activity or sector collapse which can remove vital stratigraphy particularly on volcanic islands

a systematic mapping procedure based on the modified gaussian model to characterize magmatic units from olivine pyroxenes mixtures application to the syrtis major volcanic shield on mars clenet et al 2011 have developed an adapted version of the modified gaussian model mgm the improvements allow the characterization of spectra of olivine pyroxene s mixtures addressing both modal composition and individual minerals chemical composition this version of mgm is fully automated and operational with large amounts of hyperspectral imaging data two natural cases are considered the first one is the sumail massif in the oman ophiolite earth based on our approach applied to hymap data two contrasted lithologic units are mapped the mantle which is harzburgite dominated and the crust made of gabbros and clinopyroxene rich cumulates with spectral variations interpreted in terms of pyroxenes chemical compositions once this new mgm mapping approach has been validated on a controlled natural situation we map the distribution of mafic assemblages across the syrtis major volcano on mars using a visible and near infrared vnir short wave infrared swir observatoire pour la mineralogie l eau les glaces et l activite omega mars express mex mosaic our results are in agreement with previous work but olivine appears to be more abundant than previously estimated in the central part of the volcanic edifice especially in ternary mafic assemblages augite olivine enstatite based on these results we propose a possible scenario for the igneous and thus thermal evolution of the syrtis major region surrounding terrains have formed first and local heterogeneity can be observed between northern and southern areas of the noachian crust we also observe variations in the mineral assemblages within syrtis major lavas which can be interpreted in terms of differentiation from a common parent melt and or of a progressive evolution of the mantle source composition and temperature key points mgm systematic mapping on syrtis major to characterize mafic minerals mixtures olivine and pyroxenes mixture is detected in the central lavas of the volcano pyroxenes have chemical compositions spanning the enstatite augite range

tephra geochemistry a discussion of some persistent analytical problems distal tephrochronological studies are reliant upon precise and accurate geochemical quantitation this quantitation can involve difficulties not often encountered in more conventional petrology solving these problems is of particular importance in the holocene and late quaternary of northwest europe where numerous tephra layers of icelandic origin have been detected in peat bogs and lake and marine sediments electron probe microanalysis epma has proved the most applicable analytical technique when insufficient quantities of tephra are available for bulk analysis standard epma techniques require fine tuning to the tephra problem as the geochemical instability of glass is a common feature in many previous studies geochemical data of avoidably low quality have been produced and little attention appears to have been directed to modification of epma methods it is suggested that the black box approach to geochemical analysis should be avoided by the consideration of several factors these include

clay minerals in delta deposits and organic preservation potential on mars clay rich sedimentary deposits are often sites of organic matter preservation and have therefore been sought in mars exploration however regional deposits of hydrous minerals including phyllosilicates and sulphates are not typically associated with valley networks and layered sediments that provide geomorphic evidence of surface water transport on early mars the compact reconnaissance imaging spectrometer for mars crism has recently identified phyllosilicates within three lake basins with fans or deltas that indicate sustained sediment deposition eberswalde crater holden crater and jezero crater here we use high resolution data from the mars reconnaissance orbiter mro to identify clay rich fluvial lacustrine sediments within jezero crater which has a diameter of 45 km the crater is an open lake basin on mars with sedimentary deposits of hydrous minerals sourced from a smectite rich catchment in the nili fossae region we find that the two deltas and the lowest observed stratigraphic layer within the crater host iron magnesium smectite clay jezero crater holds sediments that record multiple episodes of aqueous activity on early mars we suggest that this depositional setting and the smectite mineralogy make these deltaic deposits well suited for the sequestration and preservation of organic material

occurrence of an unknown atlantic eruption in the chaine des puys volcanic field massif central france a volcanic ash layer called mf1 was recently identified in holocene sediments from the gourgon and molhiac peat bogs monts du forez french massif central this ash layer consists of colorless shards with a heterogeneous trachytic to rhyolitic composition the trace elements analyzed by laser ablation inductively coupled plasma mass spectrometry la icp ms attest to a local origin radiocarbon dating of peat samples taken within and below the ash layer indicates the best age at 6339 61 cal yr bp i e an age contemporaneous with the volcanic activity of montchal montcineyre and pavin volcanoes from the chaine des puys volcanic field these volcanoes are characterized by basaltic and trachytic products thus the rhyolitic composition of mf1 tephra suggests that it is likely originated from an unknown eruption these results again confirm the interest of studying the distal volcanic ash fallouts in order to establish or specify records of past eruptions of volcanic fields identification of this new tephra layer also provides an additional tephrochronological marker for eastern french massif central

late glacial explosive activity on mount etna implications for proximal distal tephra correlations and the synchronisation of mediterranean archives abstract plinian and ignimbrite deposits represent explosive activity ca 17 19 cal ka within the predominantly effusive and mildly explosive strombolian volcanic history of mount etna italy proximal glasses from the biancavilla ignimbrites and unit d plinian fall deposits are characterised fall deposits recorded at acireale d1b and d2b and giarre d1a and d2a are geochemically distinct confirming they relate to different eruptions the acireale plinian fall d1b and d2b deposits compositionally overlap with the biancavilla ignimbrite deposits these explosive eruptions from etna are considered responsible for widespread ash dispersals throughout the central mediterranean region producing the marker tephra layers y 1 et 1 recorded in marine and lacustrine sedimentary archives stratigraphically these distal tephras occur at or close to the onset of the last deglaciation termination 1 within their respective palaeoenvironmental records therefore making them potentially crucial tephrostratigraphic markers this study investigates distal tephra deposits thought to be from etna recorded in the ionian sea y 1 lago grande di monticchio lgdm italy tephras tm 11 and tm 12 1 lago di mezzano italy and the haua fteah cave libya the glass chemistry of y 1 tephras recorded in the ionian sea and at haua fteah is consistent with the biancavilla ignimbrites 16 965 17 670 cal yrs bp and the upper acireale plinian fall d2b the lgdm record indicates that explosive activity on etna associated with unit d spans a minimum of 1540 80 varve years tm 12 1 19 200 19 804 cal yrs bp in lgdm appears to represent the oldest distal counterpart of etna unit d explosive activity and is associated with the lower acireale d1b plinian eruption the proximally undefined tm 11 17 640 18 324 cal yrs bp and distal correlatives are geochemically distinct from the ionian sea y 1 tephra such significant compositional differences seen between distal tephra layers are not observed within individual proximal units and are likely to indicate that the distal tephras relate to separate eruptive phases until proximal relationships can be established the tm 11 type y 1 equivalents should be termed tm 11 great care should be exercised when using these distal ash layers to synchronise sedimentary records during a crucial period of environmental change

no signature of clear co2 ice from the cryptic regions in mars south seasonal polar cap the seasonal polar ice caps of mars are composed mainly of co2 ice a region of low 30 albedo has been observed within the south seasonal cap during early to mid spring the low temperature of this cryptic region has been attributed to a clear slab of nearly pure co2 ice with the low albedo resulting from absorption by the underlying surface here we report near infrared imaging spectroscopy of the south seasonal cap the deep and broad co2 absorption bands that are expected in the near infrared with a thick transparent slab of co2 ice are not observed models of the observed spectra indicate that the low albedo results from extensive dust contamination close to the surface of a co2 ice layer which could be linked to atmospheric circulation patterns the strength of the co2 absorption increases after mid spring so part of the dust is either carried away or buried more deeply in the ice layer during the co2 ice sublimation process

volcanic ash from icelandic 57 300 yr bp eruption found in gisp2 greenland ice core we have found volcanic ash in wisconsinan ice from the gisp2 ice core retrieved from the summit location in central greenland the ash consists predominantly of large rhyolitic glass shards similar to the ones found in wisconsinan dye 3 ice from southern greenland we give the results of our analysis of the ash and present evidence that correlates this ash with the z2 ash layer found in atlantic sediment cores with the dye 3 ash with ash recently found in the grip ice core from central greenland and with ash associated with the icelandic thorsmork ignimbrite the mineralogy of the ash is very similar to that of ash from the icelandic tindfjallajokull volcano that is also present in the thorsmork ignimbrite and we suggest that this is the source volcano tindfjallajokull has also been suggested as the source of the z2 ash based on the excellent dating of the gisp2 ice core we determined that the eruptions that produced the gisp2 ash occured 57 300 1 700 yr bp which agrees extremely well with the most recent dating of 57 500 1 300 yr bp of the z2 ash based on the specmap chronology this provides us with a reliable revision of the dye 3 ice core dating at a depth of 1950 m this ice was originally dated at 70 000 yr bp

explosive silicic volcanism in iceland and the jan mayen area during the last 6 ma sources and timing of major eruptions abstract fifty three major explosive eruptions on iceland and jan mayen island were identified in 0 6 ma old sediments of the north atlantic and arctic oceans by the age and the chemical composition of silicic tephra the depositional age of the tephra was estimated using the continuous record in sediment of paleomagnetic reversals for the last 6 ma and paleoclimatic proxies 18 o ice rafted debris for the last 1 ma major element and normative compositions of glasses were used to assign the sources of the tephra to the rift and off rift volcanic zones in iceland and to the jan mayen volcanic system the tholeiitic central volcanoes along the iceland rift zones were steadily active with the longest interruption in activity recorded between 4 and 4 9 ma they were the source of at least 26 eruptions of dominant rhyolitic magma composition including the late pleistocene explosive eruption of krafla volcano of the eastern rift zone at about 201 ka the central volcanoes along the off rift volcanic zones in iceland were the source of at least 19 eruptions of dominant alkali rhyolitic composition with three distinct episodes recorded at 4 6 5 3 3 5 3 6 and 0 1 8 ma the longest and last episode recorded 11 pleistocene major events including the two explosive eruptions of tindfjallajokull volcano thorsmork ca 54 5 ka and katla volcano solheimar ca 11 9 ka of the southeastern transgressive zone eight major explosive eruptions from the jan mayen volcanic system are recorded in terms of the distinctive grain size mineralogy and chemistry of the tephra the tephra contain k rich glasses k 2 o sio 2 0 06 ranging from trachytic to alkali rhyolitic composition their normative trends ab q or and their depleted concentrations of ba eu and heavy ree reflect fractional crystallisation of k feldspar biotite and hornblende in contrast their enrichment in highly incompatible and water mobile trace elements such as rb th nb and ta most likely reflect crustal contamination one late pleistocene tephra from jan mayen was recorded in the marine sequence its age estimated between 617 and 620 ka and its composition support a common source with the borga pumice formation at sor jan in the south of the island

tephrostratigraphy of a lateglacial lake sediment sequence at wegliny southwest poland abstract this paper presents the first late quaternary locality in the present day territories of poland where multiple cryptotephra layers have been identified located near wegliny in southwest poland study of the lateglacial gyttja deposits reveals the presence of at least four non visible tephra horizons electron microprobe and laser ablation icpms analysis of glass shards suggests products from at least two icelandic volcanic centres katla and snaesfellsness of particular importance is the discovery of two eruptions believed to originate from the east eifel volcanic field within the allerod chronozone one correlates with the well documented laacher see tephra lst but the second horizon herein designated t642 t655 would appear to represent an earlier precursor eruption the chemical composition of the lst and the precursor tephra both appear to match to the upper laacher see tephra ulst phase which previously was thought to have dispersed not to the northeast but in a southerly direction towards the alpine foreland this indicates the eruption dynamics of the laacher see are more complex than hitherto recognised

characterization of phyllosilicates observed in the central mawrth vallis region mars their potential formational processes and implications for past climate mawrth vallis contains one of the largest exposures of phyllosilicates on mars nontronite montmorillonite kaolinite and hydrated silica have been identified throughout the region using data from the compact reconnaissance imaging spectrometer for mars crism in addition saponite has been identified in one observation within a crater these individual minerals are identified and distinguished by features at 1 38 1 42 1 91 and 2 17 2 41 m there are two main phyllosilicate units in the mawrth vallis region the lowermost unit is nontronite bearing unconformably overlain by an al phyllosilicate unit containing montmorillonite plus hydrated silica with a thin layer of kaolinite plus hydrated silica at the top of the unit these two units are draped by a spectrally unremarkable capping unit smectites generally form in neutral to alkaline environments while kaolinite and hydrated silica typically form in slightly acidic conditions thus the observed phyllosilicates may reflect a change in aqueous chemistry spectra retrieved near the boundary between the nontronite and al phyllosilicate units exhibit a strong positive slope from 1 to 2 m likely from a ferrous component within the rock this ferrous component indicates either rapid deposition in an oxidizing environment or reducing conditions formation of each of the phyllosilicate minerals identified requires liquid water thus indicating a regional wet period in the noachian when these units formed the two main phyllosilicate units may be extensive layers of altered volcanic ash other potential formational processes include sediment deposition into a marine or lacustrine basin or pedogenesis

correlation and characterisation of individual glass shards from tephra deposits using trace element laser ablation icp ms analyses current status and future potential pearce nicholas denton j s perkins w t westgate j a 2007 correlation and characterisation of individual glass shards from tephra deposits using trace element laser ablation icp ms analyses current status and future potential journal of quaternary science 22 7 pp 721 736 rae2008

analysis of terrestrial and martian volcanic compositions using thermal emission spectroscopy 2 application to martian surface spectra from the mars global surveyor thermal emission spectrometer atmospherically corrected thermal infrared spectra of large regions of the martian surface from the mars global surveyor thermal emission spectrometer mgs tes previously have been interpreted to represent two general spectral classes one class represents a basalt to basaltic andesite composition and the other class represents a basaltic andesite to andesite composition we have performed new linear deconvolutions of the two martian surface type spectra with an end member set tailored to represent volcanic rock types our preparatory study of laboratory spectra of terrestrial volcanic rocks acquired at 2 cm 21 sampling convolved to tes spectral sampling 10 cm 21 shows little degradation in deconvolution results when compared to results acquired using the higher spectral resolution data indicating that the deconvolution technique is valid for analyzing data at tes resolution our spectral fits to the martian data agree well with previous models and do not exhibit any notable deviations from the martian spectra that would indicate the absence of any significant end members in our model modal mineralogies obtained with these new spectral fits also compare favorably within the previously stated uncertainties to prior results the newly derived modal mineralogies are used with new and traditional classification schemes for volcanic igneous rocks introduced in a companion paper wyatt et al this issue to classify the martian compositions our results substantiate the previously proposed hypothesis that these two spectral classes on the martian surface represent volcanic compositions with distinguishable differences in silica content ranging from basalt to andesite

field studies of an instrumented model pile in clay an instrumented model pile was used to investigate the fundamental behaviour of driven cylindrical steel piles in clay soils data are described from two test bed sites one with heavily over consolidated clay and one with normally consoli dated clay these confirm that a residual shear surface is formed adjacent to the pile shaft during installation comparisons with other site investigation data and cavity expansion theoretical predic tions suggest that stress relief immediately behind the pile tip during installation gives rise to total radial stress and pore pressure measurements on the shaft which are lower than the simple cavity expansion model predicts however the data did indicate that the radial effective stress might be successfully predicted during reconsolidation the radial effective stress drops initially followed by a slow recovery which was insufticient in the two clays investigated for the final value to reach that during installation on undrained loading the clay adjacent to th

emission spectroscopy of clay minerals and evidence for poorly crystalline aluminosilicates on mars from thermal emission spectrometer data 1 to understand the aqueous history of mars it is critical to constrain the alteration mineralogy of the martian surface previously published analyses of thermal infrared 6 25 m remote sensing data of mars suggest that dark regions have 15 20 clay minerals however near infrared 1 3 m spectral results generally do not identify widespread clay minerals thermal infrared detections of clays on mars are difficult to interpret owing in part to the relative paucity of published spectral analyses of clay minerals and clay bearing materials using similar spectra thermal infrared emission spectra in this study we present an analysis of the thermal emission spectral features 6 25 m or 400 1650 cm 1 of a suite of clay mineral reference materials and clay bearing rocks linking their spectral features to the crystal chemical properties of the clays on the basis of this context provided by the emission spectral analysis of clay minerals and clay bearing rocks we reconsider the evidence for clay minerals on mars from thermal emission spectrometer tes results we propose that global scale clay abundances determined from tes probably represent a geologically significant surface component though they may actually correspond to poorly crystalline aluminosilicates with similar si o ratios to clay minerals 0 3 0 4 rather than well crystalline clays if clay minerals or clay like materials on mars are poorly crystalline and or dessicated they may be detectable in the thermal infrared but not easily detected with near infrared data sets

microanalysis of tephra by la icp ms strategies advantages and limitations assessed using the thorsmork ignimbrite southern iceland abstract micron scale analysis of vesicular volcanic glass can be problematic because thin vesicle walls and junctions limit the area available for analysis subsurface vesicles limit the vertical thickness available microcrysts at or below the surface may contaminate glass analyses and some glasses show compositional banding in addition distal tephra are very small 10 100 m and material may be sparse we have analysed the mpi ding reference glasses and natural tephra samples pumice scoria and fiamme from the thorsmork ignimbrite southern iceland using laser ablation inductively coupled plasma mass spectrometry la icp ms three different reduction strategies are used averaging uncertainty weighting and log linear regression we then assess the data quality achieved using the various strategies using our technique we show that the main limiting factor on data quality is precision particularly for natural tephra analyses at 20 000 cps relative standard deviations rsds in the thorsmork tephra are 5 10 approximately twice those achieved in the mpi ding glasses 3 5 at the same conditions rhyolitic pumice and fiamme from the thorsmork ignimbrite are compositionally homogenous the proximal deposit also contains subordinate basalt scoria therefore the deposit is bimodal the thorsmork rhyolite correlates with the north atlantic ash zone 2 naaz2 tephra described in a marine sediment core lacasse and garbe schonberg 2001 jvgr 170 113 147

towards a protocol for the trace element analysis of glass from rhyolitic shards in tephra deposits by laser ablation icp ms laser ablation inductively coupled plasma mass spectrometry la icp ms is used widely to analyse single volcanic glass shards from quaternary tephra deposits for stratigraphic correlation as yet no generally accepted protocol for these analyses exists and published methods report significant differences in crater size and calibration strategies using ca as the internal standard cai s and not sii s for the analysis of rhyolitic glass can cause significant problems because of ablation of i ca rich phenocrysts notably ubiquitous plagioclase but also calcic amphibole apatite and allanite or ii mounting epoxy resin which can contribute to the ca internal standard signal using cai s can cause underreporting of many elements which concentrate in ca rich phenocrysts making their ablation difficult to recognize but when using sii s no such underreporting occurs additionally larger ablation craters 50 m diameter potentially incorporate even small volumes of phenocryst material whereas smaller craters 20 m diameter more frequently miss phenocrysts thus for the la icp ms analysis of rhyolitic glass shards smaller ablation craters should be employed and calibrated using sii s allowing recognition and removal of analyses incorporating ca rich phenocrysts and avoiding issues related to the ablation of the mounting resin

petrogenesis of the solheimar ignimbrite katla iceland implications for tephrostratigraphy the solheimar ignimbrite was one of the largest eruptions from the katla caldera iceland and is important for tephra studies in the north atlantic because of its possible linkage with the vedde ash a compositionally bimodal tephra layer used for correlation of sedimentary records in the north atlantic and northern europe the composition of the solheimar ignimbrite extends from rhyolite to basaltic icelandite a trend that defines a coherent magma mixing line mixing is evident both in mingled textures seen in hand specimens and thin sections and as binary mixing trends in major and trace element and 87sr 86sr isotopes of the volcanic glasses the solheimar rhyolite is slightly more radiogenic than the basaltic icelandite in terms of sr isotopes which is inconsistent with generation of the rhyolite by fractionation of the basaltic icelandite alternatively the solheimar rhyolite may have been produced by partial melting of icelandic crust major and trace element modelling indicates that partial melting of icelandic tholeiite does not replicate the observed rhyolite composition in particular k2o is significantly lower in the modelled melt however partial melting of katla alkali basalt does produce a comparable melt we suggest a two stage model in which 30 40 melting of basalt generated a dacitic magma which underwent subsequent 30 fractionation of the observed phenocryst phases feldspar clinopyroxene spinel and feti oxide form rhyolite the eruption of the solheimar ignimbrite was triggered by the intrusion of basaltic icelandite magma which mixed with resident rhyolite magma during eruption the solheimar ignimbrite has been linked to the vedde ash lacasse et al 1995 a compositionally bimodal tephra layer used to link sedimentary records in the north atlantic and northern europe despite the importance of the vedde ash in late quaternary studies its provenance remains equivocal we demonstrate that vedde rhyolite glasses share the same major and trace element chemistry as the solheimar rhyolite carrying the implication that these deposits may be produced by the same eruption however the solheimar ignimbrite lacks the basaltic component that is sometimes associated with rhyolitic shards of the vedde ash at far distal locations therefore this correlation cannot be confirmed

reconstructing the quaternary evolution of the world s most active silicic volcanic system insights from an 1 65 ma deep ocean tephra record sourced from taupo volcanic zone new zealand abstract the taupo volcanic zone tvz central north island new zealand is the most frequently active quaternary rhyolitic system in the world silicic tephras recovered from ocean drilling programme site 1123 41 47 16 s 171 29 94 w 3290 m water depth in the southwest pacific ocean provide a well dated record of explosive tvz volcanism since 1 65 ma we present major minor and trace element data for 70 quaternary tephra layers from site 1123 determined by electron probe microanalysis 1314 analyses and laser ablation inductively coupled plasma mass spectrometry 654 analyses trace element data allow for the discrimination of different tephras with similar major element chemistries and the establishment of isochronous tie lines between three sediment cores 1123a 1123b and 1123c recovered from site 1123 these tephra tie lines are used to evaluate the stratigraphy and orbitally tuned stable isotope age model of the site 1123 composite record trace element fingerprinting of tephras identifies 4 5 m and 7 9 m thick sections of repeated sediments in 1123a 49 0 53 5 mbsf metres below seafloor and 1123c 48 1 56 0 mbsf respectively these previously unrecognised repeated sections have resulted in significant errors in the site 1123 composite stratigraphy and age model for the interval 1 15 1 38 ma and can explain the poor correspondence between 18o profiles for site 1123 and site 849 equatorial pacific during this interval the revised composite stratigraphy for site 1123 shows that the 70 tephra layers when correlated between cores correspond to 37 38 individual eruptive events tephras 7 of which can be correlated to onshore tvz deposits the frequency of large volume tvz derived silicic eruptions as recorded by the deposition of tephras at site 1123 has not been uniform through time rather it has been typified by short periods 25 50 ka of intense activity bracketed by longer periods 100 130 ka of quiescence the most active period at least 1 event per 7 ka occurred between 1 53 and 1 66 ma corresponding to the first 130 ka of tvz rhyolitic magmatism since 1 2 ma 80 of tephras preserved at site 1123 and the more proximal site 1124 were erupted and deposited during glacial periods this feature may reflect either enhanced atmospheric transport of volcanic ash to these sites up to 1000 km from source during glacial conditions or more speculatively that these events are triggered by changes in crustal stress accumulation associated with large amplitude sea level changes only 8 of the 37 38 site 1123 tephra units 20 can be found in all three cores and 22 tephra units 60 are only present in one of the three cores whether a tephra is preserved in all three cores does not have any direct relationship to eruptive volume instead it is postulated that tephra preservation at site 1123 is patchy and influenced by the vigorous nature of their deposition to the deep ocean floor as vertical density currents at this site at least 5 cores would need to have been drilled within a proximity of 10 s to 100 s of metres of each other to yield a 99 chance of recovering all the silicic tephras deposited on the ocean surface above it in the past 1 65 ma

central mediterranean explosive volcanism and tephrochronology during the last 630 ka based on the sediment record from lake ohrid abstract lake ohrid located in the central mediterranean region downwind of the italian volcanoes has great potential for developing a detailed record of the explosive activity of these volcanoes electron microprobe and laser ablation inductively coupled plasma mass spectrometry geochemical analyses of juvenile glass fragments of previously not analysed tephra layers of the deep site sediment record of lake ohrid expand the existing tephrostratigraphy for the interval marine isotope stages 1 16 the geochemical signatures of all tephra layers suggest an origin exclusively from the italian volcanism eight of these tephra layers have potential equivalents in marine and terrestrial archives of the central mediterranean region oh dp 1966 sc5 a7 oh dp 1955 ces1 a2 oh dp 1055 s1 oh dp 1006 s2 oh dp 0997 s3 oh dp 0710 s8 c 51 oh dp 0766 odp5 p 13 oh dp 0505 odp4 nine tephra layers which have not been described so far help to reconstruct the late volcanic activity of mount vulture oh dp 2439 and the paleovulsini oh dp 1998 the pre and post rio rava activity of the roccamonfina volcano oh dp 1911 1812 1733 1640 1527 the early activity of the aeolian arc oh dp 1513 1520 and the bracciano activity of the monti sabatini volcanic district oh dp 1175 the multi proxy dataset and chronology of the deep site sediments allowed definition of the climatostratigraphic position for all tephra layers and constrain the ages of so far unknown and or undated tephra layers the presented data provide a crucial increase of knowledge of the middle pleistocene tephrostratigraphy in the central mediterranean back to 630 ka and allows new insights of the volcanic activity of roccamonfina the roman province the campanian volcanic zone cvz the aeolian arc pantelleria and mount vulture

composition and thermal inertia of the mawrth vallis region of mars from tes and themis data abstract clay mineral bearing deposits previously discovered on mars with near infrared 0 3 5 m remote sensing data are of major significance for understanding the aqueous history geological evolution and past habitability of mars in this study we analyzed the thermal infrared 6 35 m surface properties of the most extensive phyllosilicate deposit on mars the mawrth vallis area clay mineral bearing units which in visible images appear to be relatively light toned layered bedrock have thermal inertia values ranging from 150 to 460 j m 2 k 1 s 1 2 this suggests the deposits are composed of a mixture of rock with sand and dust at 100 meter scales dark toned materials that mantle the clay bearing surfaces have thermal inertia values ranging from 150 to 800 indicating variable degrees of rockiness or induration of this younger sedimentary or pyroclastic unit thermal emission spectrometer tes spectra of the light toned rocks were analyzed with a number of techniques but none of the results shows a large phyllosilicate component as has been detected in the same surfaces with near infrared data instead tes spectra of light toned surfaces are best modeled by a combination of plagioclase feldspar high silica materials similar to impure opaline silica or felsic glass and zeolites we propose three hypotheses for why the clay minerals are not apparent in thermal infrared data including effects due to surface roughness sub pixel mixing of multiple surface temperatures and low absolute mineral abundances combined with differences in spatial sampling between instruments zeolites modeled in tes spectra could be a previously unrecognized component of the alteration assemblage in the phyllosilicate bearing rocks of the mawrth vallis area tes spectral index mapping suggests that fe mg clays detected with near infrared data correspond to trioctahedral fe2 clay minerals rather than nontronite like clays the average mineralogy and geologic context of these complex interbedded deposits suggests they are either aqueous sedimentary rocks altered pyroclastic deposits or a combination of both

phyllosilicates in the mawrth vallis region of mars 1 omega mars express has discovered large outcrops rich in phyllosilicates in the region of mawrth vallis mars around 20 w 25 n the region is located in noachian highly cratered terrains close to the limit of the martian dichotomy where the outflow channel mawrth vallis cuts the highlands we have examined this region using omega spectra of the surface from 0 9 m to 2 6 m with spatial sampling from 500 m to 3 km offering a full coverage of the region omega spectra show two broad bands centered at 1 m and 2 2 m revealing the presence of clinopyroxene on dark surfaces phyllosilicates have been identified by absorption bands at 1 4 m 1 9 m and 2 2 or 2 3 m comparison with laboratory spectra reveals similarities with al oh smectites such as montmorillonites or fe or mg oh smectites such as nontronite a precise location of the phyllosilicate rich areas on visible hrsc images indicates that they are placed exclusively on bright outcrops mostly on the plateaus dated to the noachian period on hrsc and moc images the phyllosilicate rich outcrops reveal strong erosional features such as numerous residual buttes composed of layers a few meters thick the phyllosilicate rich unit corresponds to a geological unit more than 100 m thick over a horizontal extension approximately of 300 km 400 km this unit implies a large volume of altered rocks either in situ or after transport and deposition in noachian terrains revealing a different climatic and geologic environment from the present one

analysis of terrestrial and martian volcanic compositions using thermal emission spectroscopy 1 determination of mineralogy chemistry and classification strategies we have examined and applied existing classification schemes for volcanic rocks and developed new schemes using thermal emission spectra of terrestrial volcanic rocks laboratory thermal infrared spectra 5 25 m at 2 cm 1 spectral sampling deconvolved modal mineralogies and derived mineral and bulk rock chemistries were used to distinguish basalt basaltic andesite andesite and dacite modal mineralogies derived from linear deconvolution of terrestrial volcanic rocks were compared to modes measured by an electron microprobe phase mapping technique to determine the accuracy of linear deconvolution in modeling specific mineral abundances one standard deviations of the absolute differences between modeled and measured mineral abundances range from 2 4 to 12 2 vol with an average standard deviation of 4 8 vol being in agreement with average uncertainties calculated in previous studies weighted average compositions of feldspars in the deconvolution generally overlap the measured ranges of plagioclase compositions and the presence of low calcium and high calcium pyroxenes was correctly identified bulk chemistries of volcanic rocks were derived with a relatively high degree of accuracy 1 standard deviations ranging from 0 4 to 2 6 vol by combining the compositions of spectrally modeled phases in proportion to their relative abundances in a particular sample these data were collectively used to examine existing and develop new volcanic rock classification schemes however no single classification scheme was effective in accurately classifying all samples multiple steps of classification were required to distinguish volcanic rocks reflecting the mineralogic diversity and continuum of compositions that exists in volcanic rock types in a companion paper hamilton et al this issue these schemes are applied to the classification of martian surface compositions

correlating tephras and cryptotephras using glass compositional analyses and numerical and statistical methods review and evaluation abstract we define tephras and cryptotephras and their components mainly ash sized particles of glass crystals in distal deposits and summarize the basis of tephrochronology as a chronostratigraphic correlational and dating tool for palaeoenvironmental geological and archaeological research we then document and appraise recent advances in analytical methods used to determine the major minor and trace elements of individual glass shards from tephra or cryptotephra deposits to aid their correlation and application protocols developed recently for the electron probe microanalysis of major elements in individual glass shards help to improve data quality and standardize reporting procedures a narrow electron beam diameter 3 5 m can now be used to analyze smaller glass shards than previously attainable reliable analyses of microshards defined here as glass shards in part 2 of the review we describe critically assess and recommend ways in which tephras or cryptotephras can be correlated in conjunction with other information using numerical or statistical analyses of compositional data statistical methods provide a less subjective means of dealing with analytical data pertaining to tephra components usually glass or crystals phenocrysts than heuristic alternatives they enable a better understanding of relationships among the data from multiple viewpoints to be developed and help quantify the degree of uncertainty in establishing correlations in common with other scientific hypothesis testing it is easier to infer using such analysis that two or more tephras are different rather than the same adding stratigraphic chronological spatial or palaeoenvironmental data i e multiple criteria is usually necessary and allows for more robust correlations to be made a two stage approach is useful the first focussed on differences in the mean composition of samples or their range which can be visualised graphically via scatterplot matrices or bivariate plots coupled with the use of statistical tools such as distance measures similarity coefficients hierarchical cluster analysis informed by distance measures or similarity or cophenetic coefficients and principal components analysis pca some statistical methods cluster analysis discriminant analysis are referred to as machine learning in the computing literature the second stage examines sample variance and the degree of compositional similarity so that sample equivalence or otherwise can be established on a statistical basis this stage may involve discriminant function analysis dfa support vector machines svms canonical variates analysis cva and anova or manova or its two sample special case the hotelling two sample t2 test randomization tests can be used where distributional assumptions such as multivariate normality underlying parametric tests are doubtful compositional data may be transformed and scaled before being subjected to multivariate statistical procedures including calculation of distance matrices hierarchical cluster analysis and pca such transformations may make the assumption of multivariate normality more appropriate a sequential procedure using mahalanobis distance and the hotelling two sample t2 test is illustrated using glass major element data from trachytic to phonolitic kenyan tephras all these methods require a broad range of high quality compositional data which can be used to compare unknowns with reference training sets that are sufficiently complete to account for all possible correlatives including tephras with heterogeneous glasses that contain multiple compositional groups currently incomplete databases are tending to limit correlation efficacy the development of an open online global database to facilitate progress towards integrated high quality tephrostratigraphic frameworks for different regions is encouraged

a technique for mapping fe mg rich phyllosilicates on mars using themis multispectral thermal infrared images 1 we present a method for mapping exposures of fe mg rich phyllosilicates on the martian surface using themis daytime multispectral thermal infrared images the primary utility of this technique comes from the fact that themis coverage is near global at 100 m pixel so it offers the opportunity to extend and improve upon phyllosilicate maps created using crism and or omega near infrared data alone the spectral index formulation used for this mapping consists of a sum of spectral band ratios weighted in different proportions an initial formulation of the index was determined using a suite of synthetic spectra containing varying proportions of a martian basalt spectrum and a laboratory phyllosilicate spectrum a scene specific formulation was then optimized by exploiting the correlation between pixels the initial formulation flags in each themis scene as containing phyllosilicates and those identified in overlapping crism data once the optimal formulation of the index is determined it is applied to the entire themis scene extending the map of phyllosilicates beyond the area of overlapping crism coverage the method is illustrated using 12 themis scenes from the mawrth vallis and nili fossae regions the new themis derived maps of fe mg rich phyllosilicates in these two regions have approximately double the coverage provided by crism data the cross wavelength and cross instrument approach we use to derive phyllosilicate indices for themis data could potentially be used to define spectral indices for mapping other compositions of interest on mars that possess spectral features in more than one spectral region

closure to piezocone penetration testing in atlantic piedmont residuum by kimberly a finke paul w mayne and rick a klopp

tephrochronology of last termination sequences in europe a protocol for improved analytical precision and robust correlation procedures a joint scotav intimate proposal the precise sequence of events during the last termination 18 000 9000 ka 14 cy r bp and the extent to which major environmental changes were synchronous are difficult to estab lish using the radiocarbon method alone because of serious distortions of the radiocarbon time scale as well as the influences of site specific errors that can affect the materials dated attention has there fore turned to other methods that can provide independent tests of the chronology and correlation of events during the last termination with emphasis on european sequences we summarise here the potential of tephrostratigraphy and tephrochronology to fulfil this role recent advances in the detection and analysis of hidden tephra layers cryptotephra indicate that some tephras of last termination age are much more widespread in europe than appreciated hitherto and a number of new tephra deposits have also been identified there is much potential for developing an integrated tephrochronological framework for europe which can help to underpin the overall chronology of events during the last termination for that potential to be realised however there needs to be a more systematic and robust analysis of tephra layers than has been the practice in the past we pro pose a protocol for improving analytical and reporting procedures as well as the establishment of a centralised data base of the results which will provide an important geochronological tool to support a diverse range of stratigraphical studies including opportunities to reassess volcanic hazards although aimed primarily at europe the protocol proposed here is of equal relevance to other regions and periods of interest copyright 2004 john wiley sons ltd

science and empiricism in pile foundation design scientific approaches to pile design have advanced enormously in recent decades and yet still the most fundamental aspect of pile design that of estimating the axial capacity relies heavily upon empirical correlations improvements have been made in identifying the processes that occur within the critical zone of soil immediately surrounding the pile but quantification of the changes in stress and fabric is not straightforward this paper addresses the degree of confidence we can now place a on the conceptual and analytical frameworks for estimating pile capacity and b on the quantitative parameters required to achieve a design the discussion is restricted to driven piles in clays and siliceous sands with particular attention given to extrapolating from design approaches derived for closed ended piles of relatively small diameter to the large diameter open ended piles that are used routinely in the offshore industry from a practical viewpoint we need design approaches that minimise sensitivity

the detailed tephrostratigraphy of a core from the south east black sea spanning the last 60 ka one visible volcanic ash layer and 21 non visible cryptotephra horizons have been identified in the m72 5 25 gc1 core from the south east black sea that spans the last 60 ka glass chemistry suggests that the tephras derive from italian hellenic and turkish sources the visible tephra layer is trachytic in composition and has been correlated to the 39 ka campanian ignimbrite super eruption from campi flegrei caldera italy two cryptotephra layers are associated with eruptions from acigol volcano turkey around the last glacial maximum another is linked to activity at erciyes dagi in the early holocene perikartini or karagullu and a cryptotephra layer near the top of the core correlates to the 3 6k cal a bp minoan marine z2 tephra from santorini thera greece this extends the known dispersal area for all these volcanic ash units many other calc alkaline rhyolite layers preserved in the core are likely to be from central anatolian sources but the lack of detailed proximal data for many of the volcanoes in the region prohibits further correlations the tephrostratigraphy and glass compositional data presented here allow the tephra layers to be used to correlate sedimentary archives across the region and help to extend the mediterranean tephrochronology framework towards the east

evaluating the in situ lateral stress coefficient k0 of soils via paired shear wave velocity modes abstractthe utilization of shear wave velocities toward the evaluation of the in situ geostatic horizontal stress state in soils is validated specifically the lateral stress coefficient k0 field shear wave velocities from paired sets of different directional and polarization modes are compiled from 16 well documented test sites involving a variety of geomaterials focus is particularly placed on shear wave velocities measured by downhole tests vsvh crosshole tests vshv and special rotary type crosshole tests vshh at these sites field k0 stress states have been quantified using one or more direct assessment techniques including self boring pressuremeter total stress cells and hydrofracture in field testing as well as suction measurements special consolidometers and or triaxial arrangements on undisturbed samples in the laboratory although the specific delineation of stress induced versus inherent or fabric anisotropy may be difficult it is shown that the ratio of horizontally polarized