integrated provenance and detrital thermochronology studies on the andrill and 2a drill core late oligocene early miocene exhumation of the transantarctic mountains southern victoria land antarctica terra nova 22 361 368 2010 abstract detrital apatite fission track data combined with provenance analysis of gravel fraction detritus are used in this study to investigate the neogene exhumation of the west antarctic rift system samples have been collected from the upper 1000 m of the andrill and 2a drill core which documents the miocene history of the victoria land basin most samples have apatites with fission track ages between 23 and 36 ma and gravel clasts derived from the erebus volcanic province and the transantarctic mountains exposed along the southern victoria land coast these results indicate the existence of a so far undetected oligocene early miocene exhumation phase in the region between the blue koettlitz and skelton mulock glaciers suggesting the importance of fluctuation of local glaciers in the royal society range and or expansions into the mcmurdo sound of an ice sheet mainly sourced by larger outlet glaciers located further south

a detrital apatite fission track study of the ciros 2 sedimentary record tracing ice pathways in the ross sea area over the last 5 ma

crustal structure at the blake spur fracture zone from expanding spread profiles we present results from wkbj and reflectivity synthetic seismogram modeling of 10 reversed expanding spread profiles esps along flow lines parallel to the blake spur fracture zone across 140 ma atlantic crust these profiles provide detailed constraints on variations in crustal structure at the fracture zone seven profiles on either side of the fracture zone show a normal structure for old oceanic crust a 2 3 km thick upper layer with a steep velocity gradient is underlain by 4 5 km of crust with velocities of 6 5 7 2 km s and low gradient and a sharp transition to upper mantle velocities of 8 km s several velocity discontinuities were detected within the upper 2 3 km but these do not generally coincide with intracrustal reflectors detected by simultaneous normal incidence reflection profiles this structure shows little regional variation toward the fracture zone despite the small magnetic anomaly offset 12 km and the indistinct topographic signature of the fracture zone three esps within a 10 20 km wide ribbon centered on the fracture zone trough show clearly anomalous crustal structure relative to normal oceanic crust a 2 4 km thick high gradient upper layer is underlain by a thick prism of material with a velocity of 7 2 7 6 km s and high poisson s ratio probably at least 0 29 which is consistent with 15 30 serpentinization of upper mantle peridotites this interpretation requires the action of off axis hydrothermal circulation penetrating the cracked and relatively permeable fracture zone lithosphere to a depth of at least 7 km the original igneous crust in a narrow region close to the fracture zone is thus inferred to have been much thinner than adjacent normal crust which may imply a sharp reduction in the magma budget at the ends of the adjacent spreading segments

tectonic and climatic signals from apatite detrital fission track analysis of the cape roberts project core records south victoria land antarctica abstract the cenozoic tectonic reorganization of the west antarctic rift system in the ross sea region occurred concurrently with a major change in the global climate system and a global reorganization of plate motions this region thus provides the opportunity to study in detail a range of geological issues dealing with tectonic and climate feedbacks during the late eocene early oligocene greenhouse icehouse transition at high latitudes with the aim to decipher tectonic vs climatic forcing in the ice sheet drainage evolution a detrital apatite fission track study was carried out throughout the cenozoic drill cored stratigraphic succession of the cape roberts project mcmurdo sound victoria land basin apatite fission track ages of detrital samples with depositional ages between 34 ma and 17 ma were decomposed into statistically significant age populations three age peaks were detected reflecting different bedrock provenance areas i a young peak p1 between 34 ma and 26 ma recording the signal of a source area exhumed with a constant denudation rate but absent in the proximal continental area and ii two peaks older than 40 ma that are instead compatible with thermochronological data available from the onshore bedrock p1 peak testifies a late oligocene early miocene denudation event and traces a southern provenance of a fraction of the sediments filling the cape roberts basin we propose that this denudation event might have been triggered by renewed n s transtensional shearing along the western shoulder of victoria land basin controlling glacial flow pattern and the associated sediment transport

the evolution of the subglacial landscape of antarctica the aim is to investigate the evolution of the subglacial landscape of antarctica using an ice sheet and erosion model we identify different stages of continental glaciation and model the erosion processes associated with each stage the model links erosion to the basal thermal regime and indicates that much of the antarctic interior may have been subject to less than 200 m of erosion the depth of erosion reflects the presence or absence of warm based ice and the consistency of ice flow direction this information linked with knowledge about landscapes of glaciation in the northern hemisphere and some simple but robust assumptions about initial topography is used to generate a map of the subglacial antarctic landscape in which much of the lowland interior resembles the landscapes of areal scouring typical of the laurentian and scandinavian shields near the continental margins selective linear erosion has overdeepened pre existing river valleys by as much as 2 8 km high elevation plateaus adjacent to such drainage systems have survived largely unmodified under cold based ice high erosion rates result from steep thermal gradients in basal ice mountain regions such as the gamburtsev mountains uplands in dronning maud land and massifs in west antarctica are likely to bear features of local alpine glaciation such landscapes may have been protected under cold based ice for the last 34 myrs or possibly longer

development and inversion of the mesozoic victoria basin in the terra nova bay transantarctic mountains derived from thermochronological data abstract the terra nova bay region of the transantarctic mountains hosts three n s to nnw sse extending mountain ranges deep freeze range eisenhower range and northern prince albert mountains all ranges consist of basement rocks locally overlain by permo triassic sediments and jurassic volcanic rocks recent thermochronological studies recognized that the eisenhower range was originally covered by a kilometre thick jurassic eocene sedimentary sequence here we present a comprehensive apatite fission track aft and u th sm he ahe data set of vertical sample profiles from the terra nova bay to reconstruct architecture extension and geometry of this depocentre and place its evolution in the context of supraregional geodynamic processes the study comprises new data and thermal history models from the deep freeze range and new thermal history models of published data from the northern prince albert mountains new aft and ahe ages of 25 275 ma from the deep freeze range correlate tightly with sample elevations thermal history modelling of these data and complementary proxies detects common heating of the jurassic surface and rapid late eocene cooling regression of vertical paleotemperature profiles reveals an increased jurassic and a moderate cretaceous eocene geothermal gradient of 45 and 25 c km respectively paleotemperatures and gradients used in tandem infer basement burial increasing from 2 km in deep freeze and eisenhower ranges to 3 4 km in the prince albert mountains such a varying overburden probably reflects regional differences in the jurassic basement topography subsequently sediment thickness uniformly increased in the order of 1 km until late eocene mid jurassic basin initiation and subsequent sediment accumulation is explained by extension of a mesozoic victoria basin during gondwana breakup between antarctica and australia late eocene early oligocene basin inversion is associated with the formation of the west antarctic rift system while differential final exhumation represents the change from downwearing to backstepping incision

thermochronologic evidence for orogen parallel variability in wedge kinematics during extending convergent orogenesis of the northern apennines italy analysis of 146 new apatite u th he ages six new apatite fi ssion track ages and 165 previously published apatite fi ssiontrack aft ages from the northern apennine extending convergent orogen reveals a signifi cant along strike change in post late miocene wedge kinematics and exhumation history east of 11 30 e age patterns and age elevation relationships are diagnostic of ongoing frontal accretion and slab retreat consistent with a northeastward migrating orogenic wave enhanced erosion rates of 1 mm yr over a period of 3 5 ma are recorded on the contractional pro side of the orogen and 0 3 mm yr on the extending retro side west of 11 30 e ongoing exhumation has been restricted to the range core since at least ca 8 ma at rates of 0 4 mm yr increasing to 1 mm yr in the pliocene ca 3 ma accompanied by post pliocene tilting and associated faulting this pattern can be attributed to either continued convergence but a switch in the transfer of material into the wedge to a regime dominated by underplating or out of sequence shortening or a slowdown or cessation of frontal accretion and slab retreat with enhanced pliocene uplift and erosion triggered by a deeper seated process such as lithospheric delamination complete slab detachment or slab tear these fi ndings emphasize that no single model of wedge kinematics is likely appropriate to explain long term northern apennine orogenesis and synconvergent extension but rather that different lithospheric geodynamic processes have acted at different times in different lateral segments of the orogen

hydraulic conductivity of geosynthetic clay liners exhumed from landfill final covers samples of geosynthetic clay liners gcls from four landfill covers were tested for water content swell index hydraulic conductivity and exchangeable cations exchange of ca and mg for na occurred in all of the exhumed gcls and the bentonite had a swell index similar to that for ca or mg bentonite hydraulic conductivities of the gcls varied over 5 orders of magnitude regardless of cover soil thickness or presence of a geomembrane hydraulic conductivity was strongly related to the water content at the time of sampling controlled desiccation and rehydration of exhumed gcls that had low hydraulic conductivity 10 9 to 10 7 cm s resulted in increases in hydraulic conductivity of 1 5 4 orders of magnitude even with overburden pressure simulating a 1 m thick cover comparison of these data with other data from the united states and europe indicates that exchange of ca and or mg for na is likely to occur in the field unless the overlying cover soil is sodic sodium rich the comparison also shows th

cretaceous oblique extensional deformation and magma accumulation in the fosdick mountains migmatite cored gneiss dome west antarctica 1 the fosdick mountains west antarctica expose a 15 x 80 km migmatite cored gneiss dome consisting of migmatitic gneisses diatexite migmatite and subhorizontal leucogranite sheets the fosdick dome was emplaced and exhumed in the mid cretaceous due to oblique extension associated with the west antarctic rift system along the west antarctic new zealand segment of east gondwana the dome is bounded to the south by a dextral oblique detachment structure and to the north by an inferred dextral strike slip fault within the fosdick dome and in the detachment zone granite occupies leucosomes dikes sills and dilatant and shear structures the pattern of kilometer scale domains of migmatite and granite suggest that lithologic variations and heterogeneous deformation boudinage resulted in pressure gradients that enhanced melt flow and magma accumulation in the fosdick dome steep foliations are overprinted folded and transposed by subhorizontal fabrics the crosscutting relationship is interpreted as a transition from wrench deformation to oblique divergence steep structures in the dome host concordant subvertical leucosome and granite sheets yielding shrimp u pb zircon ages between ca 117 and 114 ma prevalent subhorizontal domains host large volumes of subhorizontal diatexite migmatite and granite sheets that yield u pb zircon ages between ca 109 and 102 ma these ages indicate a timescale for melt influx of approximately 15 ma and that the transition from wrench to oblique divergence may have occurred in as little as 5 ma granites with crystallization ages between ca 109 and 102 ma were also emplaced in the south fosdick detachment zone indicating that the detachment was active during oblique divergence shrimp u pb titanite ages between ca 102 and 97 ma for late to post tectonic diorite dikes are interpreted as emplacement ages and give a minimum age for gneissic foliation development during detachment faulting the fosdick mountains preserve a record of the middle to lower crustal response to a transition from wrench to oblique extensional deformation overprinting structural relationships show that a change in the angle of oblique extension can induce accumulation of subhorizontal magma sheets and lead to initiation of a detachment zone

post orogenic evolution of the dabie shan eastern china from u th he and fission track thermochronology the dabie shan of eastern china is a 200 kilometers wide mountain range with nearly 2 kilometers of relief and is an archetype of deep ultrahigh pressure metamorphic rock exhumation despite its regional and petrologic importance little is known about the low temperature and post orogenic evolution of the dabie shan here we present apatite and zircon u th he ahe and zhe respectively and apatite fission track aft cooling ages from the dabie shan that constrain the patterns and history of exhumation over the last 115 myr on the scale of the whole orogen zhe and ahe ages are inversely correlated with mean elevation and are systematically younger in the core of the range these cooling ages were converted to exhumation rates assuming steady state erosion and accounting for topographic effects these results indicate that since the eocene flanks of the range have eroded at rates as low as 0 02 km myr while the range core has eroded at about 0 06 km myr even in the core of the range these recent exhumation rates are at least 10 to 20 times slower than those estimated for the initial stages of exhumation in the triassic jurassic in a 1 4 kilometer vertical transect in the core of the range all ages are positively correlated with elevation with zhe ages increasing from 76 to 112 ma aft from 44 to 70 ma and ahe from 24 to 43 ma we present a simple model for topographic correction of thermochronometric ages in vertical transects using the admittance ratio ratio of isotherm relief to topographic relief applied to the ahe age elevation relationship this yields tertiary exhumation rates of 0 05 to 0 07 km myr in the core of the dabie shan in good agreement with regional exhumation rate patterns finally age elevation relationships for all three chronometers in the vertical transect are consistent with a constant exhumation rate of 0 06 0 01 km myr since the creta ceous with a possible modest increase in exhumation rates as high as 0 2 km myr between 80 to 40 ma these data show no evidence for significant variations in exhumation rates over the last 115 myr as might be expected for decay of old topography or tectonic reactivation of old structures

the eisenhower range transantarctic mountains evaluation of qualitative interpretation concepts of thermochronological data abstract the transantarctic mountains tam were one of the first regions where apatite fission track aft thermochronology was applied routinely to study exhumation processes and long term landscape evolution pioneering publications from the region introduced or refined interpretation concepts of thermochronological data such as the break in slope in vertical age profiles as qualitative marker for the onset of accelerated rock cooling new aft data were compiled from vertical profiles in the eisenhower range northern tam and compared with published data samples originally examined by the population technique were re analyzed via the external detector technique aft ages increase from 32 2 ma at an elevation of 220 m to 175 14 ma at 2380 m geological evidence and thermal history modeling of the aft data require jurassic to late eocene reheating of the samples and an onset of cooling at 35 30 ma this requires the deposition of an 3 to 3 5 km thick sedimentary sequence on the granitic basement subsequent to jurassic ferrar magmatism at 180 ma the regression of paleotemperatures against sample altitudes infers a high jurassic geothermal gradient of 60 c km related to rifting processes and ferrar magmatism and a moderate cretaceous eocene geothermal gradient of 30 c km comparison of ages generated with population and external detector technique shows the importance of determining single grain ages for each sample even from granitic rocks of the same intrusion and thus strongly supports previous cases made for the determination of annealing kinetics and grain age evaluation age comparison additionally illustrates that samples above a break in slope record larger deviations between population and external detector ages than samples below a break in slope we demonstrate that the position and shape of a break in slope result from various factors such as the thermal history prior to final cooling maximum paleotemperatures cooling rate and geothermal gradient a break in slope does not straightly date the onset of final cooling and cannot substitute thermal history modeling therefore earlier studies from the tam and similar settings elsewhere need to be validated by combining thermal history modeling of thermochronological data and supplementary geological information

properties of barrier components in a composite cover after 14 years of service and differential settlement abstracta case study is presented describing the effects of age 14 years and differential settlement 0 3 m vertical over 0 4 m horizontal along a horizontal distance of 10 m on the engineeri

poisson s ratio of a seaward dipping reflector series hatton bank summary seismic reflection profiles across the hatton bank continental margin in the eastern north atlantic have imaged thick sequences of seaward dipping reflectors converted shear waves propagating through one of these sequences were recorded on a two ship expanding spread profile just landward of the ocean continent transition synthetic seismogram modelling of these shear waves indicates that poisson s ratio in the sequence is 0 27 0 01 similar to that of normal oceanic layer 2

tectonic and denudational history of the rennick graben north victoria land implications for the evolution of rifting between east and west antarctica 1 the tectonic depression of the rennick graben northern victoria land antarctica is a key element for deciphering the cenozoic separation history between east and west antarctica and evolution of the west antarctic rift system the geometry kinematics and timing of the boundary faults of the rennick graben are presented on the basis of a detailed structural study of the major fault segments combined with apatite fission track data the structural architecture of the rennick graben is controlled by distributed and partitioned right lateral strike slip faulting fission track data indicate that the last significant denudation stage of the rennick graben shoulders started from eocene times with increasing cooling and denudation since 40 50 ma a direct structural connection is then established between cenozoic denudation and the activation of the dextral strike slip regime in north victoria land during the cenozoic in this framework the rennick graben is interpreted as a localized tectonic depression generated as a displacement accommodation area of the regionally sized dextral strike slip shearing the results of this study 1 invalidate the commonly assumed link between mesozoic ross sea rifting and opening of the rennick graben 2 argue against orthogonal rifting models for the cenozoic evolution of the ross sea region and 3 provide constraints to the modalities and timing of the separation between the east antarctic craton and the west antarctica extensional province

cenozoic range front faulting and development of the transantarctic mountains near cape surprise antarctica thermochronologic and geomorphologic constraints 1 the transantarctic mountains tam define the western flank of the west antarctic rift system cape surprise near the shackleton glacier in the central tam is the only location along the range s 3500 km length where upper paleozoic beacon supergroup strata are down faulted to near sea level previous studies have inferred a range front master normal fault accommodates extension and rock uplift across the tam front in this region the history of rock uplift is debated suggested as early as mesozoic typically cenozoic or even pliocene or younger structural observations apatite fission track aft thermochronology and geomorphologic mapping undertaken within the tam front east of the shackleton glacier indicate extension faulting and denudation was mostly late eocene late oligocene and likely into the early miocene an exhumed aft partial annealing zone is found at the coast and traced 50 km inland the base of that exhumed partial annealing zone indicates denudation accelerated at 40 ma near the coast and at 30 35 ma on the inland side of the tam front vertically offset aft isochrones across the tam front reveal a step faulted architecture rather than a single master fault the cumulative vertical offset of the 55 ma isochrone is 2 3 2 7 km compared to 2 4 2 6 km offset of beacon strata indicating that all significant normal faulting is cenozoic and not related to mesozoic extension within the west antarctic rift system denudation from 26 ma to 14 ma produced a locally preserved erosion surface within the tam front erosion surface remnants indicate the tam front has undergone minimal internal deformation and only 290 790 m of surface uplift along offshore faults since the middle miocene

exhumation and performance of an antarctic composite barrier system after 4 years exposure an antarctic biopile using a composite liner high density polyethylene geomembrane gmb over a geosynthetic clay liner gcl was constructed on a coarse granular subgrade to contain hydrocarbon

hydraulic conductivity of bentonite slurry mixed sands the hydraulic conductivity k of specimens from columns containing initially dry sands mixed with bentonite slurries was measured the mixed specimens represented a range in void ratios 0 672 e 3 94 and bentonite contents 0 61 bc 7 65 by dry weight the measured k values which ranged from 2 4 10 7 cm s to 6 8 10 4 cm s correlated poorly with the total void ratio e of the specimens due to the complicating effect of the bentonite in the sand bentonite slurry mixtures however the measured k values correlated better with the void ratio of the bentonite eb which is consistent with the results of previous studies involving permeation of compacted bentonite and sand bentonite specimens even though the range in values of eb in this study 42 5 eb 127 was much higher than that previously reported the relatively large range in eb values for the sand bentonite slurry mixtures was also consistent with the relatively large range in measured k values which are about one to seven or

changes in geosynthetic clay liner gcl properties after 2 years in a cover over arsenic rich tailings a test cover comprised of three different needle punched geosynthetic clay liner gcl products and covered with up to 1 m of cover soil gravelly sand was built over arsenic rich tailings at a former gold mine in nova scotia canada to evaluate the performance of the gcls under local climatic conditions of the gcls examined one had untreated and two had polymer enhanced natural sodium bentonite the three gcls each had different carriers one with a woven geotextile one with a scrim reinforced nonwoven geotextile and one with a woven geotextile laminated with a polypropylene film at some locations each type of gcl was placed in direct contact with the tailings at other locations each gcl was separated from the tailings by 0 15 m of cover soil samples of each gcl tailings and cover soil were recovered 1 and 2 years after construction tests show that the gcl with untreated bentonite maintained a low hydraulic conductivity 5 10 11 m s at locations where there was 0 7 m of cover soil abov

preferential flow in geosynthetic clay liners exhumed from final covers with composite barriers geosynthetic clay liners gcls were exhumed from final covers with composite barriers geomembrane over gcl at two municipal solid waste landfills in the usa preferential flow and high hydraulic conductivity 2 10 9 m s was observed in eight of the 18 gcl samples collected from both sites at one site manganese oxide precipitate was concomitant with bundles of needle punched fibers that conducted preferential flow nearly complete replacement of na by ca on the bentonite surface occurred in all gcl samples gcls with and without preferential flow could not be differentiated by physical and chemical properties commonly used to differentiate gcls with high and low hydraulic conductivities exhumed water content swell index mole fraction monovalent cations soluble cation concentrations the relative abundance of soluble cations in the pore water of gcls exhibiting preferential flow was comparable to the relative abundance in the subgrade pore water whereas the pore water in gcls with distributed

the mesozoic victoria basin vanished link between antarctica and australia the transantarctic mountains tam are the largest non compressional mountain belt in the world their origin is traditionally related to crustal thickening during the jurassic ferrar magmatic event that was followed by episodic uplift in the early and late cretaceous and since the paleocene this concept of a long lived morphological high constitutes a base of virtually all gondwana reconstructions and global climate models here we demonstrate that crossover age relationships between thermochronological apatite fission track data and stratigraphic information contradict this established interpretation instead these data together with a wealth of independent thermal indicators and geological evidence require the existence of a vast intra gondwana basin between at least late triassic and late cretaceous times including during the ferrar magmatic event referred to here as the mesozoic victoria basin mvb this basin formed during crustal extension across the paleo pacific margin of antarctica and australia uplift of the tam with associated basin inversion commenced only with the development of the west antarctic rift system in paleogene times the recognition of the long lived mvb has primary consequences for the general understanding of the landscape of gondwana and the breakup between antarctica and australia west antarctic rifting and uplift of the tam and global long term climate evolution and faunal radiation

intraplate shortening in the central indian ocean determined from a 2100 km long north south deep seismic reflection profile although intraplate deformation is commonly observed on the continents there are only a few places in the oceans where deformation is distributed over a broad area rather than being localized at a single plate boundary the central indian ocean has long been recognized as a site of active widespread compressive deformation of the oceanic lithosphere reflecting an exceptionally high stress level however the strain pattern derived from indirect and incomplete observations remains poorly known a more complete data set was obtained during the phedre cruise 1991 by means of deep seismic reflection profiling one 2100 km long profile runs along the 81 e meridian from lat 14 s to the coast of sri lanka and provides us with the first long cross section through the region of observed crustal level faults fault analysis offers new estimates of the amount of shortening which was obtained across individual faults by measuring the maximum vertical uplift of sedimentary reflectors at the base of the sedimentary cover and converting it to horizontal throw under various assumptions of the fault geometry the contribution of the seismically resolvable faults amounts to 22 37 km of shortening or 2 5 4 3 this is two to three times greater than previous estimates extrapolated from local measurements on shorter seismic reflection profiles

analysis of antarctic glacigenic sediment provenance through geochemical and petrologic applications abstract the number of provenance studies of glacigenic sediments in antarctica has increased dramatically over the past decade providing an enhanced understanding of ice sheet history and dynamics along with the broader geologic history such data have been used to assess glacial erosion patterns at the catchment scale flow path reconstructions over a wide range of scales and ice sheet fluctuations indicated by iceberg rafted debris in circumantarctic glacial marine sediments it is notable that even though most of the bedrock of the continent is ice covered and inaccessible provenance data can provide such valuable information about antarctic ice and can even be used to infer buried rock types along with their geo and thermochronologic history glacigenic sediments provide a broader array of provenance analysis opportunities than any other sediment type because of their wide range of grain sizes and in this paper we review methods and examples from all size fractions that have been applied to the antarctic glacigenic sedimentary record interpretations of these records must take careful consideration of the choice of analytical methods uneven patterns of erosion and spatial variability in sediment transport and rock types which all may lead to a preferential identification of different elements of sources in the provenance analyses because of this we advocate a multi proxy approach and highlight studies that demonstrate the value of selecting complementary provenance methods

performance of polymer enhanced bentonite sand mixture for covering arsenic rich gold mine tailings for up to four years experiments conducted over a 4 year period on a polymer enhanced bentonite sand mixture pebsm used as cover for gold mine tailings are reported the effect on pebsm hydraulic conductivity k of subgrade porewater chemistry subgrade water content and confining stress are investigated results show that the reduction in the mole fraction of bound na esp and corresponding increase in k of pebsm with time was highly dependent on the ionic strength of the subgrade porewater when the pebsm was in direct contact with gold mine tailings with porewater having an ionic strength of 145 mmol l esp decreased from 59 to 2 and k increased from 4 10 11 to 6 9 10 9 m s the esp and k values of pebsm over tailings with 11 mmol l porewater were 21 and 6 9 10 11 m s respectively a 0 15 m thick foundation layer between tailings and pebsm layer significantly lowered the reduction in esp and increase in k with time as did a reduction in the subgrade water content there was no effect of changing confining

effect of a calcium rich soil on the performance of an overlying gcl abstractchanges in geosynthetic clay liner gcl properties over time are examined for the case in which the gcl 1 rests directly on a ca rich soil 1 700 1 800 mg l ca and 2 a 30 cm foundation soil 200 300 mg l ca overlying the ca rich soil results for a control case in which the gcl rested only on the foundation soil are also reported the moisture content increased to 108 and then remained constant in the control case the moisture and calcium uptake from the underlying soil caused the moisture content of gcl to increase to 96 and 86 in the first 279 days of the experiment for the cases with and without foundation soil respectively the moisture content then decreased to 80 and 67 after 1 100 days under isothermal condition with and without the foundation layer respectively after 1 100 days three years the hydraulic conductivity of the gcl increased attributable to cation exchange from approximately 3 10 11 m s initially to approximately 7 10 11 and 2 10 10 m s with and

cenozoic erosion of the transantarctic mountains a source to sink thermochronological study abstract the formation of the transantarctic mountains tam is strictly related to the evolution of the west antarctic rift system but the timing of their exhumation is still not fully assessed in this work we provide new apatite fission track data collected on the region between the royal society range and the britannia range cooling ages are late eocene oligocene in the center of the region but they get older both northwards and southwards we infer that exhumation was strictly controlled by tam parallel fault strands that were active after the oligocene the royal society range and the britannia range represent transition zones corresponding to transverse structures probably inherited from early basement crustal discontinuities and reactivated as transfer regions during rift propagation the exhumation of the investigated region has been then modeled and predicted thermochronological ages have been compared with detrital data from the miocene sedimentary succession drilled in the victoria land basin results indicate that this sector of the tam is the most probable candidate for the source of sediments and that during the neogene 3 km but up to 5 km of rocks was exhumed

mineralogical and geochemical characterization of the old tailings dam australia evaluating the effectiveness of a water cover for long term amd control abstract establishing a shallow water cover over tailings deposited in a designated storage facility is one option to limit oxygen diffusion and retard oxidation of sulfides which have the potential to form acid mine drainage amd the old tailings dam otd located at the savage river mine western tasmania contains 38 million tonnes of pyritic tailings deposited from 1967 to 1982 and is actively generating amd the otd was constructed on a natural gradient resulting in sub aerial exposure of the southern area with the northern area under a natural water cover this physical contrast allowed for the examination of tailings mineralogy and geochemistry as a function of water cover depth across the otd tailings samples n 144 depth 1 5 m were collected and subjected to a range of geochemical and mineralogical evaluations tailings from the southern and northern extents of the otd showed similar amd potential based on geochemical nag ph range 2 1 to 4 2 and bulk mineralogical parameters particularly at depth however sulfide alteration index sai assessments highlighted the microscale contrast in oxidation in the sub aerial zone pyrite grains are moderately oxidized to a depth of 0 3 m maximum sai of 6 10 under both gravel fill and oxidized covers with secondary minerals e g ferrihydrite and goethite developed along rims and fractures beneath this mildly oxidized pyrite is seen in fresh tailings sai 2 9 10 to 5 8 10 in the sub aqueous zone the degree of pyrite oxidation demonstrates a direct relationship with cover depth with unoxidized potentially reactive tailings identified from 2 5 m directly beneath an organic rich sediment layer sai 0 to 1 10 these findings are broadly similar to other tailings storage facilities e g fox lake sherritt gordon zn cu mine canada and stekenjokk mine sweden where water covers up to 2 m have successfully reduced amd whilst geotechnical properties of the otd restrict the extension of the water cover pyrite is enriched in cobalt up to 2 6 wt indicating reprocessing of tailings as an alternative management option through adoption of an integrated mineralogical and geochemical characterization approach for tailings assessment robust management strategies after mine closure can be developed

antarctic topography at the eocene oligocene boundary we present a reconstruction of the antarctic topography at the eocene oligocene ca 34 ma climate transition this provides a realistic key boundary condition for modeling the first big antarctic ice sheets at this time instead of using the present day bedrock topography which has changed significantly from millions of years of tectonism and erosion we reconstruct topography using a set of tools including ice sheet erosion models models of thermal subsidence and plate movement erosion estimates are constrained with offshore sediment volumes estimated from seismic stratigraphy maximum and minimum topographic reconstructions are presented as indicators of the range of uncertainty our results point to a significant upland area in the ross sea marie byrd land and weddell sea sectors in addition east antarctic coastal troughs are much shallower than today due to the restoration of material that has been selectively eroded by the evolving ice sheets parts of east antarctica have not changed since the e o boundary because they were protected under non erosive cold based ice the reconstructions provide a better defined boundary condition for modeling that seeks to understand interaction between the antarctic ice sheet and climate along with more robust estimates of past ice volumes under a range of orbital settings and greenhouse gas concentrations

evidence of a full west antarctic ice sheet back to the early oligocene insight from double dating of detrital apatites in ross sea sediments the west antarctic ice sheet is the most unstable component of the antarctic cryosphere its fluctuations are well documented since the pliocene but its behaviour over the last 35 ma is more controversial particularly during periods of past high global pco2 values similar to those predicted in future global climate scenarios here we present new u pb dating of detrital apatite grains previously dated by the fission track method from cape roberts project oligocene to pliocene marine sediments in the ross sea two past ice flow patterns were identified one formed by outlet glaciers sourcing short travelled apatites and one northerly directed bringing far travelled apatite grains the latter provides the first robust physical evidence for the presence and repeated expansion of an oligocene west antarctic ice sheet

field performance of gcl under ion exchange conditions five victorian reservoirs of brick pillar and arch construction were renovated using geosynthetic clay liners also called bentonite geosynthetic composites gcl as roof sealing materials the gcl was predominantly sodium bentonite and contained some 2 of calcite gcls were laid on leveled original puddled clay packed between and above the brick arches there was an overlying gravel layer connected to a drainage system that in turn was covered with soil and seeded with grass leaks through roofs into stored potable water were discovered excavation and exposure of the gcl showed that they were finely cracked in many places samples of the gcl bentonite from several locations at each of five sites had a high moisture content also the gcl had a much reduced exchangeable sodium and increased exchangeable calcium content when compared to the dry unused gcl laboratory experiments lasting for a limited period were carried out to simulate operating conditions of the gcl whereby water falling on the ground and reaching the gcl flowed across the gcl in the overlying gravel layer to collector drains similar but less extensive ion exchange calcium for sodium was found here also the evidence demonstrates that calcium from calcite contained in the gcl bentonite exchanged with sodium and in so doing contributed to shrinkage and cracking supplementary sources of calcium for ion exchange probably came from overlying calcareous soil and water from firehoses used to field test the integrity of the gcl

interpretation of u th he single grain ages from slowly cooled crustal terranes a case study from the transantarctic mountains of southern victoria land low temperature thermochronologic techniques e g apatite fission track aft thermochronology and u th he dating constrain near surface t t paths and are often applied to uplift denudation and landscape evolution studies samples collected in vertical profiles from granitic walls on either side of the ferrar glacier southern victoria land antarctica were analyzed using aft thermochronology and apatite u th he dating to further constrain the lowest temperature thermal history of this portion of the transantarctic mountains aft central ages vary systematically with elevation and together with track length information define a multi stage cooling denudation history in the cretaceous and early tertiary apatite u th he single grain age variation with elevation is not as systematic with considerable intra sample age variation although many complicating factors e g u and th rich micro inclusions fluid inclusions variation in crystal size particle ejection correction zonation and particle ejection correction implantation of he into a crystal or impediment of he diffusion out of a crystal and 147sm derived particles may contribute to age dispersion we found that variation in single grain ages correlated with cooling rate samples that cooled relatively quickly have less variation in single grain ages whereas samples that cooled relatively slowly 3 c m y or resided within an u th he partial retention zone heprz prior to more rapid cooling have a comparatively greater variation in ages decay of u and th via particle emission creates a 4he concentration profile dependent upon the initial parent u th within a crystal variation of single grain ages for samples with non homogeneous u th distributions will be enhanced with long residence time in the partial retention zone i e slow cooling because of the relative importance of loss via volume diffusion and loss via particle ejection with respect to the u th zonation and the grain boundary correction of ages for particle ejection ft correction factor typically assumes uniform u and th distribution within the crystal and when applied to a population of crystals with different u and th distributions will enhance the variation in ages most complicating factors listed above for apatite u th he ages result in ages that are too old we propose that if considerable variation in u th he single grain ages exists that a weighted mean age is determined once outlier single crystal ages are excluded using the criterion of chauvenet or a similar approach we suggest that the true age or most representative age for that age population lies between the minimum u th he age and the weighted mean age we apply this approach coupled with composite age profiles to better constrain the t t history of the profiles along the ferrar glacier significant intra sample variation in single crystal apatite u th he ages and other minerals dated by the u th he method should be expected especially when the cooling rate is slow the variation of u th he single crystal ages is therefore another parameter that can be used to constrain low temperature thermal histories

potential for desiccation of geosynthetic clay liners used in barrier systems abstractthe potential for the desiccation of a geosynthetic clay liner gcl forming part of a single composite landfill liner is evaluated a thermohydromechanical model is used to identify conditions likely to cause desiccation simulations for typical landfill conditions show that the potential risk of desiccation exists even at relatively low temperatures i e 35 c it is found that the water content of the gcl prior to waste placement the liner temperature the overburden stress the grain size and water content of the subsoil and the depth to aquifer all affect the potential for desiccation the results suggest that the placement of gcls directly over coarse grained soils or drainage layers should be evaluated carefully this study highlights the need for more research into the potential for gcl desiccation and in particular the need to establish water retention curves for different gcls over a range of stresses and degrees of hydration before heating so that the effect of stress and hystere