late pliocene and quaternary glaciations of new zealand abstract evidence of late pliocene glaciations is fragmentary the ross glaciation in northwest south island is correlated with the first marine faunal evidence of marked cooling in the wanganui basin in southern north island it is inferred to be in the 2 6 2 4 ma age range the porika glaciation in a separate area of northwest south island is younger judged by palynology and is correlated with a cooling 2 2 2 1 ma bp inferred from stratigraphic evidence of lowered sea level in the wanganui basin a gap of 1 5 ma in the record of glaciations is largely filled by wanganui basin marine sediments although an unconformity cuts out the record between ca 1 45 and 1 0 ma bp since then the many sedimentary cycles caused by sea level changes are presumed to be glacio eustatic in origin uplifted interglacial marine terraces back to marine oxygen isotope stage 17 and river terraces formed by cold climate aggradation are linked into the cyclic sequence through loess and tephra in their cover beds east of the south island cores from the dsdp site 594 in the southwest pacific record the earliest glaciation and higher in the core nine periods of south island glaciation in the last 0 7 ma onshore because of uplift and erosion only the last four glaciations assigned to oxygen isotope stages 10 8 6 and 4 2 are identified being named nemona waimaunga waimea and otira glaciations they are best known in north westland northwest south island where the relations of glacial outwash and interglacial shoreline deposits are displayed the late otira glaciation stage 2 is radiocarbon dated as beginning somewhat before 22 3 ka bp culminating ca 18 ka bp and ending at ca 14 ka bp when rapid deglaciation began a relatively small advance at ca 12 ka bp may have been followed by little change until after 8 6 ka bp recession was then followed by a period of advance from ca 5 ka bp until recent centuries and a subsequent recession that still continues

glaciations of the west coast range tasmania geomorphic stratigraphic palynologic and 14c evidence indicates that the west coast range tasmania was glaciated at least three times during the late cenozoic the last or margaret glaciation commenced after 30 000 yr b p culminated about 19 000 yr b p and ended by 10 000 yr b p during this period a small ice cap ca 250 m thick and cirque and valley glaciers covered 108 km2 the glacial deposits show little chemical weathering or erosional dissection the snow line ranged from 690 to 1000 m with an average of 830 m for the ice cap mean temperature was 6 5 c below the present temperature during the preceding henty glaciation a 300 to 400 m thick ice cap and outlet glaciers exceeded 1000 km2 the glacial deposits are beyond 14c assay they are more weathered chemically and more dissected than margaret age deposits and the degree suggests a pre last interglaciation age 130 000 yr b p the snow line of the ice cap lay at 740 m and annual temperature was reduced by 7 c ice of the earliest linda glaciation slightly exceeded that of the henty glaciation but had a similar distribution the glacial deposits are intensely weathered have reversed magnetization and overlie a paleosol containing pollen of tertiary type an early pleistocene or tertiary age is indicated

late pleistocene glaciation of the kosciuszko massif snowy mountains australia abstract late pleistocene glaciation of the australian mainland was restricted to a small area of the southeastern highlands geomorphic mapping of the area and exposure dating using the in situ produced cosmogenic isotope 10be provides evidence for at least two distinct glaciations the early kosciuszko glaciation consisted of a single glacier advance before 59 300 5400 years ago snowy river advance the late kosciuszko glaciation comprised three glacier advances 32 000 2500 headley tarn advance 19 100 1600 blue lake advance and 16 800 1400 years ago mt twynam advance the early kosciuszko glaciation was the most extensive and the late kosciuszko advances were progressively less extensive these periods of glaciation in the highlands correspond to episodes of periglacial activity and peaks in lake levels and river discharge at lower elevations in southeastern australia glacier advances on the kosciuszko massif correlate with advances in tasmania south america and new zealand and are broadly representative of hemispheric climate changes during the last glacial cycle

extensive mountain glaciation in central patagonia during marine isotope stage 5 abstract the timing and magnitude of glacial advances throughout a glacial cycle can give insight on the underlying drivers of climate change our knowledge of glacial activity early in a glacial cycle however is limited by incomplete preservation of the geomorphological record here we present a b 10 e dated glacial chronology from early in the last glacial cycle from the belgrano valley east of monte san lorenzo in central patagonia our chronology reveals the most extensive glacial advance of the last glacial cycle occurred at 75 ka at the end of marine isotope stage 5 a second less extensive advance occurred at 25 ka during the global last glacial maximum the topographic setting is such that ice growth would have initiated on and around the san lorenzo massif at the start of the glacial cycle we suggest reduced southern hemisphere summer insolation at the time played a significant role in driving this early advance the comparatively smaller glacier extent during the global last glacial maximum is likely a consequence of the build up of the full patagonian ice sheet which would have caused ice divide migration ice flow re routing and increased aridity on its lee side

organomineralization in mesoproterozoic giant ooids abstract ooids are common carbonate particles that are traditionally considered as abiogenically formed by physical and chemical processes in highly agitated environments recent studies point to the importance of microbial activities in ooid formation but more case studies are required to confirm and clarify the roles of microbes and their organomineralization processes here we report an integrated petrographic element geochemical and isotopic study of mesoproterozoic giant ooids from the wumishan formation ca 1 50 1 45 ga of north china the wumishan giant ooids 2 0 14 4 mm are composed of small micritic nuclei and thick radial fibrous cortices abundant organic relics including putative bacterial filaments and mucus like extracellular polymeric substances eps are present in ooid cortices organominerals e g nanoparticles and polyhedrons are concentrated and lined with the axes of radial fibers suggesting in situ mineralization of bacterial filaments the abundance of organic relics and fiber aligned organominerals confirms the constructive roles of microbes in the formation of the wumishan giant ooids the preservation of bacterial filaments filament bundles in their growth orientation requires fast mineralization in caco 3 supersaturated environments which may have been controlled by the shallow chemocline in redox stratified mesoproterozoic basins

australasian evidence for mid holocene climate change implies precessional control of walker circulation in the pacific abstract at its simplest the pacific cell of the walker circulation may be regarded as a thermal circulation driven by the temperature contrast between the west and east pacific evidence from australasia is summarized indicating that this circulation was greatly weakened in the early holocene but was enhanced at about 5000 bp the initial effect of this enhancement was the intensification of the northern australian monsoon within the australian tropics but this was reversed abruptly after 3700 bp the enhancement is attributed to an increased polar equator pressure gradient after 5000 bp with consequent intensification of the overall circulation pattern in the southern hemisphere including the mid latitude westerlies and the trade winds this in turn appears to be a result of increased southern hemisphere seasonality driven by the precessional cycle it is proposed that increased wind speeds off south america after 5000 bp in both mid and low latitudes enhanced upwelling and reduced sea surface temperatures ssts this created a greater east west surface temperature contrast across the pacific compounding a pre existing trend towards enhanced circulation and flipping climates in the southern hemisphere pacific basin from an early holocene mode to a late holocene mode under reduced circulation conditions early holocene climates at low latitudes in the southern hemisphere may have been dominated by monsoonal heat transfers

timing of late quaternary glaciations in the himalayas of northern pakistan optically stimulated luminescence dating of late quaternary glaciogenic sediments was undertaken in critical areas of the himalayas of northern pakistan in order to examine the timing of glaciation the dates demonstrate that several glaciations occurred during the last glacial cycle in swat the grabral 2 stade and the kalam i stade were dated at ca 77 ka and ca 38 ka respectively the error on the former date is large and it is conceivable that the moraines may have formed during the early part of oxygen isotope stage 3 rather than during oxygen isotope stage 4 the kalam i stade however clearly represents a glaciation during oxygen isotope stage 3 the oldest moraines and those at the lowest altitude in the indus valley at shatial have an age of ca 60 ka these also relate to a major glacial advance during oxygen isotope stage 3 a younger series of moraines the jalipur tillite and glaciofluvial sands at liachar in the indus valley and moraines at rampur tarshing have ages of ca 27 ka ca 21 23 ka and ca 15 ka respectively these dates show that glaciers also occupied parts of the indus valley during oxygen isotope stage 2 these dates and the morphostratigraphy show that glaciation in the pakistani himalaya was more extensive during the early part of the last glacial cycle and that the local last glacial maximum in pakistan was asynchronous with the maximum extent of northern hemisphere ice sheets copyright 2000 john wiley sons ltd

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

comment on barrell et al reconciling the onset of deglaciation in the upper rangitata valley southern alps new zealand quaternary science reviews 203 2019 141 150

optical dating using infrared diodes young samples abstract ages are reported for unburnt sediment samples from 9 archaeological sites in england spanning 1000 5000 years samples from two modern contexts have also been measured

millennial scale variability in south east australian hydroclimate between 30 000 and 10 000 years ago abstract global climate variability during the late quaternary is commonly investigated within the framework of the bipolar seesaw pattern of asynchronous temperature variations in the northern and southern polar latitudes the terrestrial hydrological response to this pattern in south eastern australia is not fully understood as continuous high resolution well dated proxy records for the hydrological cycle in the region are sparse here we present a well dated highly resolved record of moisture balance spanning 30000 10000 calendar years before present 30 10 ka bp based on x ray fluorescence and organic carbon isotope 13com measurements of a sedimentary sequence from lake surprise in south eastern australia the data provide a locally coherent record of the hydrological cycle elevated si reflecting windblown quartz and clays and relatively high 13com indicate an extended period of relative aridity between 28 and 18 5 ka bp interrupted by millennial scale episodes of decreased si and 13com suggesting increased moisture balance this was followed by a rapid deglacial shift to low si and 13com at 18 5 ka bp indicative of wetter conditions we find that these changes are coeval with other records from south eastern australia and new zealand and use a monte carlo empirical orthogonal function approach to extract a common trend from three high resolution records our analyses suggest that drivers of the regional hydrological cycle have varied on multi millennial time scales in response to major shifts in global atmosphere ocean dynamics during the last glacial interglacial transition southern ocean processes were the dominant control on hydroclimate during glacial times via a strong influence of cold sea surface temperatures on moisture uptake and delivery onshore following the last deglaciation around 18 ka bp the southward migration of cold southern ocean fronts likely resulted in the establishment of conditions more like those of the present day millennial scale variability in records from the region is dominated by a persistent ca 2300 year periodicity consistent with other records across the southern hemisphere mid latitudes however this pervasive periodicity is not obviously linked to the bipolar seesaw and the mechanism remains equivocal

glacial interglacial ocean climate variability from planktonic foraminifera during the mid pleistocene transition in the temperate southwest pacific odp site 1123 abstract planktonic foraminiferal assemblages and artificial neural network estimates of sea surface temperature sst at odp site 1123 41 47 2 s 171 29 9 w 3290 m deep east of new zealand reveal a high resolution history of glacial interglacial g i variability at the subtropical front stf for the last 1 2 million years including the mid pleistocene climate transition mpt most g i cycles of 100 kyr duration have short periods of cold glacial and warm deglacial climate centred on glacial terminations followed by long temperate interglacial periods during glacial deglacial transitions maximum abundances of subantarctic and subtropical taxa coincide with sst minima and maxima and lead ice volume by up to 8 kyrs such relationships reflect the competing influence of subantarctic and subtropical surface inflows during glacial and deglacial periods respectively suggesting alternate polar and tropical forcing of southern mid latitude ocean climate the lead of ssts and subtropical inflow over ice volume points to tropical forcing of southern mid latitude ocean climate during deglacial warming this contrasts with the established hypothesis that southern hemisphere ocean climate is driven by the influence of continental glaciations based on wholesale changes in subantarctic and subtropical faunas the last 1 2 million years are subdivided into 4 distinct periods of ocean climate 1 the pre mpt 1185 870 ka has high amplitude 41 kyr fluctuations in sst superimposed on a general cooling trend and heightened productivity reflecting long term strengthening of subantarctic inflow under an invigorated antarctic circumpolar current 2 the early mpt 870 620 ka is marked by abrupt warming during mis 21 followed by a period of unstable periodicities within the 40 100 kyr orbital bands decreasing sst amplitudes and long intervals of temperate interglacial climate punctuated by short glacial and deglacial phases reflecting lower meridional temperature gradients 3 the late mpt 620 435 ka encompasses an abrupt decrease in the subantarctic inflow during mis 15 followed by a period of warm equable climate poorly defined low amplitude g i variations in ssts during this interval are consistent with a relatively stable stf and evenly balanced subantarctic and subtropical inflows possibly in response to smaller less dynamic polar icesheets 4 the post mpt 435 0 ka is marked by a major climatic deterioration during mis 12 and a return to higher amplitude 100 kyr frequency sst variations superimposed on a long term trend towards cooler ssts and increased mixed layer productivity as the subantarctic inflow strengthened and polar icesheets expanded

microbial carbonates the geological record of the calcified bacterial algal mats and biofilms summary deposits produced by microbial growth and metabolism have been important components of carbonate sediments since the archaean geologically best known in seas and lakes microbial carbonates are also important at the present day in fluviatile spring cave and soil environments the principal organisms involved are bacteria particularly cyanobacteria small algae and fungi that participate in the growth of microbial biofilms and mats grain trapping is locally important but the key process is precipitation producing reefal accumulations of calcified microbes and enhancing mat accretion and preservation various metabolic processes such as photosynthetic uptake of co2 and or hco3 by cyanobacteria and ammonification denitrification and sulphate reduction by other bacteria can increase alkalinity and stimulate carbonate precipitation extracellular polymeric substances widely produced by microbes for attachment and protection are important in providing nucleation sites and facilitating sediment trapping microbial carbonate microfabrics are heterogeneous they commonly incorporate trapped particles and in situ algae and invertebrates and crystals form around bacterial cells but the main component is dense clotted or peloidal micrite resulting from calcification of bacterial cells sheaths and biofilm and from phytoplankton stimulated whiting nucleation interpretation of these texturally convergent and often inscrutable fabrics is a challenge conspicuous accumulations are large domes and columns with laminated stromatolite clotted thrombolite and other macrofabrics which may be either agglutinated or mainly composed of calcified or spar encrusted microbes stromatolite lamination appears to be primary but clotted thrombolite fabrics can be primary or secondary microbial precipitation also contributes to hot spring travertine cold spring mound calcrete cave crust and coated grain deposits as well as influencing carbonate cementation recrystallization and replacement microbial carbonate is biologically stimulated but also requires favourable saturation state in ambient water and thus relies uniquely on a combination of biotic and abiotic factors this overriding environmental control is seen at the present day by the localization of microbial carbonates in calcareous streams and springs and in shallow tropical seas and in the past by temporal variation in abundance of marine microbial carbonates patterns of cyanobacterial calcification and microbial dome formation through time appear to reflect fluctuations in seawater chemistry stromatolites appeared at 3450 ma and were generally diverse and abundant from 2800 to 1000 ma inception of a proterozoic decline variously identified at 2000 1000 and 675 ma has been attributed to eukaryote competition and or reduced lithification thrombolites and dendrolites mainly formed by calcified cyanobacteria became important early in the palaeozoic and reappeared in the late devonian microbial carbonates retained importance through much of the mesozoic became scarcer in marine environments in the cenozoic but locally re emerged as large agglutinated domes possibly reflecting increased algal involvement and thick micritic reef crusts in the late neogene famous modern examples at shark bay and lee stocking island are composite coarse agglutinated domes and columns with complex bacterial algal mats occurring in environments that are both stressed and current swept products of mat evolution ecological refugia sites of enhanced early lithification or all three

towards a climate event stratigraphy for new zealand over the past 30 000 years nz intimate project it is widely recognised that the acquisition of high resolution palaeoclimate records from southern mid latitude sites is essential for establishing a coherent picture of inter hemispheric climate change and for better understanding of the role of antarctic climate dynamics in the global climate system new zealand is considered to be a sensitive monitor of climate change because it is one of a few sizeable landmasses in the southern hemisphere westerly circulation zone a critical transition zone between subtropical and antarctic influences new zealand has mountainous axial ranges that amplify the climate signals and consequently the environmental gradients are highly sensitive to subtle changes in atmospheric and oceanic conditions since 1995 intimate has through a series of international workshops sought ways to improve procedures for establishing the precise ages of climate events and to correlate them with high precision for the last 30 000 calendar years the nz intimate project commenced in late 2003 and has involved virtually the entire new zealand palaeoclimate community its aim is to develop an event stratigraphy for the new zealand region over the past 30 000 years and to reconcile these events against the established climatostratigraphy of the last glacial cycle which has largely been developed from northern hemisphere records e g last glacial maximum lgm termination i younger dryas an initial outcome of nz intimate has been the identification of a series of well dated high resolution onshore and offshore proxy records from a variety of latitudes and elevations on a common calendar timescale from 30 000 cal yr bp to the present day high resolution records for the last glacial coldest period lgcp including the lgm sensu stricto and last glacial interglacial transition lgit from auckland maars kaipo and otamangakau wetlands on eastern and central north island marine core md97 2121 east of southern north island speleothems on northwest south island okarito wetland on southwestern south island are presented discontinuous fragmentary records comprising compilations of glacial sequences fluvial sequences loess accumulation and aeolian quartz accumulation in an andesitic terrain are described comparisons with ice core records from antarctica epica dome c and greenland gisp2 are discussed a major advantage immediately evident from these records apart from the speleothem record is that they are linked precisely by one or more tephra layers based on these new zealand terrestrial and marine records a reasonably coherent regionally applicable sequence of climatically linked stratigraphic events over the past 30 000 cal yr is emerging three major climate events are recognised 1 lgcp beginning at ca 28 000 cal yr bp ending at termination i ca 18 000 cal yr bp and including a warmer and more variable phase between ca 27 000 and 21 000 cal yr bp 2 lgit between ca 18 000 and 11 600 cal yr bp including a lateglacial warm period from ca 14 800 to 13 500 cal yr bp and a lateglacial climate reversal between ca 13 500 and 11 600 cal yr bp and 3 holocene interglacial conditions with two phases of greatest warmth between ca 11 600 and 10 800 cal yr bp and from ca 6 800 to 6 500 cal yr bp some key boundaries coincide with volcanic tephras copyright 2007 john wiley sons ltd

quantifying the effects of vein mineralogy thickness and orientation on the strength of intact veined rock abstract the presence of veins in the rock matrix influences the behaviour of a rock this results in a behaviour that is distinct from intact rock without any veins and structure and from jointed rock in this context intact veined rock is a rock containing mineral veins and no joints this paper investigates the influence of vein mineralogy thickness and orientation on the strength of intact veined andesite from the el teniente mine this investigation has focused on a comprehensive vein characterization and analyses of the results of triaxial compression experiments in a comprehensive laboratory investigation it was demonstrated that the peak strength of intact veined rock specimens was strongly influenced by the orientations of individual veins whereby vein mineralogy and thickness had a lesser role a further analysis of the mineral composition of the intact veined rock specimens following a series of triaxial tests revealed a more dominant influence of the mineral composition of the veins it was shown that rock specimens dominated by veins containing 4 attained significantly lower peak strengths than specimens where the average content of hard minerals exceeded 60 of the vein infill analyses of the mobilised shear strength of individual veins demonstrated a strong correlation between the presence of hard minerals and the strength of individual veins in the rock specimens this relationship was stronger when the vein volumetric content of hard minerals was

the stratigraphy timing and climatic implications of glaciolacustrine deposits in the middle rakaia valley south island new zealand abstract stratigraphic interpretations and infrared stimulated luminescence irsl ages document the glacial history of the middle rakaia gorge section of the rakaia valley canterbury new zealand during the last two glacial cycles sheets of glaciolacustrine sediments several tens of metres in thickness can be traced at least 10 km upstream of the rakaia gorge the stratigraphic package is capped by outwash gravels associated with the last glacial maximum lgm advances the dominant inferred sedimentary environments in the sequence are 1 pro glacial and paraglacial lake beds 2 sub aqueous ice contact fans 3 sub aqueous mass flow deposits 4 supraglacial dump material and 5 outwash gravels syndepositional deformation associated with glacitectonic deformation is common the stratigraphy records glacier margin oscillations including six significant advances these occurred in early mis 6 mid mis 6 mis 5b c100 90 ka mis 5a 4 c 80 ka mid mis 3 c 48 ka and late mis 3 c 40ka all the post mis 6 advances can be corroborated from other sites in new zealand and the timings appear to coincide with both southern hemisphere insolation minima and maxima suggesting variable combinations of climatic forcing in new zealand glaciation

timing of glaciation during the last glacial cycle evaluating the concept of a global last glacial maximum lgm abstract it has long been known that mountain glaciers and continental ice sheets around the globe reached their respective maximum extent at different times during the last glacial cycle often well before the global last glacial maximum lgm c 23 19 ka which is formally defined by peaks in global sea level and marine oxygen isotope records however there is increasing evidence from around the world that it was not only mountain glaciers which were asynchronous with the global lgm but also some regions of the large continental glaciers the barents kara ice sheet in northern eurasia together with a majority of ice masses throughout asia and australasia reached their maximum early in the last glacial cycle a few thousand years before the global lgm period the east antarctic ice sheet also reached its maximum extent several millennia before the global lgm in numerous mountainous regions at high mid and low latitudes across the world glaciers reached their maximum extent before marine isotope stage mis 2 in mis 5 4 and 3 this is in contrast to most sectors of the laurentide ice sheet the cordilleran ice sheet the se sector of the fennoscandinavian ice sheet and the alpine ice sheet in central europe which appear to have reached their maximum close to the global lgm in mis 2 the diachronous maximum extents of both mountain glaciers and continental ice sheets during the last glacial cycle means that the term and acronym last glacial maximum lgm has limited chronostratigraphical meaning when correlating glacial deposits and landforms

the timing of the last glacial maximum in australia abstract late pleistocene glaciation of australia was restricted to the snowy mountains and the tasmanian highlands glaciers were most extensive in tasmania where ice caps formed on the central plateau and west coast ranges and systems of valley and cirque glaciers formed on surrounding mountains to investigate the timing of maximum glacier advance during the last glacial maximum lgm we dated boulders on 18 moraines in 8 glaciated areas using cosmogenic 36cl and 10be we sampled moraines deposited by cirque and valley glaciers in a range of climate types and lithologies over a 7 latitudinal and a 1430 m altitudinal transect exposure ages for lgm moraine boulders group tightly in the range 17 20 ka boulders from the hamilton moraine often treated as the lgm type moraine range in age from 190 350 ka indicating that it was deposited well before the last glaciation collectively the exposure ages show that southeastern australia was glaciated briefly during and after the lgm and deglaciated well before the holocene ice retreated from the terminal moraines after the period of coldest sea surface temperatures in the southwest pacific ocean no evidence was found for readvance of glaciers during the antarctic cold reversal or the younger dryas period

luminescence chronology of late pleistocene glacial deposits in north westland new zealand abstract the chronology of the late pleistocene glacial history of north westland south island of new zealand is refined by luminescence dating of sediments it is demonstrated by two case studies that ages determined by different luminescence techniques agree well with the results of radiocarbon dating luminescence ages determined for sediments from two key sites of the loopline formation confirm the previous correlation of this unit with marine isotope stage mis 4 this indicates that late pleistocene glaciers reached their last maximum extent in north westland during the early part of the otira last glaciation furthermore initial dating evidence on coarse alluvial deposits in the lowlands indicates their formation during mis 5b and mis 5d it is probable that these coarse gravel deposits are outwash related to glacial advances if so both advances were probably much less extensive than the glaciations during mis 4 and mis 2

rupture of veined granite in polyaxial compression insights from three dimensional discrete element method modeling granite formations have been frequently involved in subsurface energy related activities such as radioactive waste disposal oil and gas storage this is principally because of their mechanical stability low permeability and high corrosion resistance these favorable properties however can be compromised by the addition of mineral veins which tend to occur ubiquitously in upper crustal rock formations evaluation of the impact of veins on the integrity and rupture characteristics of granite especially under true triaxial stresses is therefore important yet currently underemphasized this study examines the rupture of veined granite in polyaxial compression via a discrete element method model in the model with soft veins the rupture is localized along the fabricated inclined veins 45 relative to the horizontal with strike running in the 2 direction under low confining stresses 2 67 mpa in contrast a combined rupture of veins and granite matrix is observed when 2 is increased to 141 6 mpa shear sliding along the inclined veins is revealed by examining the displacement field shear induced volumetric dilation is suspected in the soft veined models in relatively low confining stresses 2 67 mpa with sliding and dilation behavior apparently suppressed at 2 141 6 mpa hard veins impede local rupture resulting in conjugate shear bands the well recognized 2 effect is observed for the hard veined models while no pronounced 2 effect is noticed for the soft veined models this study also reveals that vein thickness has a negligible impact on rupture characteristics which is however profoundly affected by vein orientation

facies architecture within a regional glaciolacustrine basin copper river alaska abstract this paper defines the principal architectural elements present within the pleistocene glaciolacustrine basin fill of the copper river basin in alaska the copper river drains an intermontane basin via a single deeply incised trench through the chugach mountains to the gulf of alaska this trench was blocked by ice during the last glacial cycle and a large ice dammed lake referred to as lake atna filled much of the copper basin facies analysis within the basin floor allows a series of associations to be defined consistent with the basinward transport of sediment deposited along calving ice margins and at the basin edge basinward transport involves a continuum of gravity driven processes including slumping cohesive debris flow hyperconcentrated concentrated density flows and turbidity currents this basinward transport results in the deposition of a series of subaqueous fans of which two main types are recognised 1 large stratified basin floor fans which extend over at least 5 km and are exposed in the basin centre these fans are composed of multiple lobes incised by large mega channels giving fan architectures that are dominated by horizontal strata and large cross cutting channel fills individual lobes and channel fills consist of combinations of diamict derived from iceberg rainout and the ice marginal release of subglacial sediment multiple units of fining upward gravels which grade vertically into parallel laminated and rippled fine sands and silts deposited by a range of density flows and currents derived from the subaqueous discharge of meltwater and rhythmites grading vertically into diamicts deposited from a range of sediment density flows re mobilising sediment deposited by either iceberg rainout or the ice marginal release of sediment 2 small complex proximal fans which extend over less than 2 km and are exposed in the southern part of the basin these fans are composed of coalescing and prograding lobes of diamict and gravel deposited both directly by subaqueous meltwater and from sediment density flows these lobes are cross cut by a range of sand and gravel filled troughs and channels cut by subaqueous outwash and either overlie or are overlain by horizontal sheets of gravel and diamict deposited from a range of sediment density flows the fans are therefore characterised by a complex and laterally variable facies architecture water depth proglacial topography stability of meltwater portals and sediment supply may all be important in determining the type of subaqueous fan present at any one location we suggest that the copper river basin fill is dominated by packages of sediment containing multiple subaqueous fans with individual fans separated by units of diamict each sediment package is in turn separated from the next by a palaeo landsurface shaped by interstadial interglacial fluvial processes and by volcanic debris flows

sedimentology and architecture of de geer moraines in the western scottish highlands and implications for grounding line glacier dynamics sedimentary exposures in moraines in a scottish highland valley glen chaorach reveal stacked sequences of bedded and laminated silt sand and gravel interspersed or capped with diamicton units in four examples faults and folds indicate deformation by glaciotectonism and syndepositional loading we propose that these sediments were laid down in an ice dammed lake close to the last ice margin to occupy this glen individual units within cross valley de geer moraine ridges are interpreted by comparison with examples from similar environments elsewhere stratified diamictons containing laminated or bedded lenses are interpreted as subaqueous ice marginal debris flow deposits massive fine grained deposits as hyperconcentrated flow deposits and massive gravel units as high density debris flow deposits using an allostratigraphic approach we argue that glaciotectonically deformed coarsening upward sand and gravel sequences that culminate in deposition of subglacial diamicton represent glacier advances into the ice marginal lake whereas undisturbed cross bedded sand and gravel reflects channel or fan deposits laid down during glacier retreat a flat terrace of bedded sand and gravel at the northern end of glen chaorach is interpreted as subaerial glaciofluvial outwash on the basis of these inferences we propose the following three stage deglacial event chronology for glen chaorach during glacier recession ice separation and intra lobe ponding first led to subaquaeous deposition of sorted and unsorted facies subsequent glacier stabilisation and ice marginal oscillation produced glaciotectonic structures in the ice marginal sediment pile and formed de geer moraines finally drainage of the ice dammed lake allowed a subaerial ice marginal drainage system to become established throughout deglaciation deposition within the lake was characterized by abrupt changes in grain size and in the architecture of individual sediment bodies reflecting changing delivery paths and sediment supply and by dynamic margin oscillations typical of water terminating glaciers

reply to comment received from j shulmeister et al regarding reconciling the onset of deglaciation in the upper rangitata valley southern alps new zealand quaternary science reviews 203 2019 141 150

origin of the ediacaran weng an and kaiyang phosphorite deposits in the nanhua basin sw china abstract the weng an and kaiyang phosphorite deposits are located in central guizhou southwestern china and formed within the sinian ediacaran doushantuo formation a systematic investigation of the geology mineralogy and geochemistry of these phosphorites was conducted to constrain the redox environment origin and genetic mechanisms of ediacaran phosphorite in the lower ore layer layer a the phosphate minerals are mainly globular phosphate intraclasts which are characterized by special sedimentary and reworking textures including microgranular sedimentary isopachous cement shrinkage crack and spongy texture the phosphate minerals from the upper layer layer b have microbial phosphate components namely embryo and algae like microfossils these phosphatic microfossils have biological structures and both consist of interior structure and isopachous wall the p2o5 concentration of phosphorites in layer a reach 32 31 somewhat higher than that in layer b 28 7 whereas the p content in globular phosphate intraclasts 40 05 resemble that of the microbial phosphate component 41 19 rocks from layer a have left inclining post archean australian shale paas normalized rare earth element ree distributions with higher ce anomalies ceanom ranging from 0 12 to 0 01 average 0 07 in contrast rocks from layer b have hat shaped paas normalized ree distributions with lower ceanom ranging from 0 32 to 0 23 average 0 28 these geochemical characteristics suggest that hydrothermal fluids mixed with normal seawater might have contributed to metallogenesis and the redox environment transitioned from anoxic to oxic from layer a to b we conclude that the lower doushantuo globular intraclasts formed by the mechanical reworking of previous phosphatic sediments which were dominated by the strong mechanical power of seawater the upper doushantuo microbial phosphorite on the other hand formed by microbially mediated accretionary growth

the timing and nature of the last glacial cycle in new zealand abstract this paper constitutes a review of the last otiran glaciation in new zealand spanning marine isotope stages mis 4 2 we highlight the nature of glaciation which is characterised by exceptional sedimentation relatively mild maritime climatic conditions and the widespread presence of water associated with proglacial settings these conditions produce glacial systems characterised by extensive outwash fans and relatively small terminal moraines extensive recent geochronological work allows us to recognise at least eight glacial advances during the otiran these occurred at 65 3 25ka 47 5 3 ka 38 5 2 ka 31 5 3 ka 26 5 2 ka 20 5 2 ka 17 2 ka and 13 1 ka which we term the otira 1 to 8 advances respectively though the analytical uncertainty ranges for some of these advances overlap all are independently distinguished through moraine morphologic relationships and or stratigraphic relationships in outcrop major advances appear to be associated with climate influences such as periods of southern hemisphere insolation minima 65ka and 31 5 ka advances the last glacial maximum cooling lgm 20 5 ka and periods of antarctic cooling 13ka the timing of greatest glacial extent in the last glacial cycle is not simultaneous across new zealand the mis 4 advance was the greatest in the southern south island while the mis 3 2 advances 26 5 ka were greatest in the central south island in the northern south island and the north island mis 4 mis 3 2 and the last glacial maximum appear to be equivalent in extent we attribute these spatio temporal variations in the timing of maximum glaciation to precipitation changes related to a northward shift in the track of the westerlies

orbital forcing of mid latitude southern hemisphere glaciation since 100 ka inferred from cosmogenic nuclide ages of moraine boulders from the cascade plateau southwest new zealand cosmogenic nuclide be 10 exposure dating of moraine boulders in the cascade valley southwest new zealand reveals three phases of glaciation with similar maximum magnitude since 100 ka in this area 8 10 lateral moraines were deposited during the last glacial maximum lgm at 22 19 ka and 15 lateral moraines and three end moraines were deposited during recession after the lgm also three exposure ages of 29 33 ka from pre lgm deposits may indicate increased weathering and erosion at the onset of the lgm in new zealand as has been suggested by other studies an exposure age of 57 8 2 7 ka from one of the highest moraines combined with previous studies of cave speleothems glacial features offset by the alpine fault the vostok dust record and sediment cores supports the inference that a significant glacial phase culminated at 66 58 ka a cluster of five exposure ages from older moraines reveals a glacial phase with at least three advance retreat cycles at 79 0 3 9 ka correlation between the ages of glacial periods and the timing of southern hemisphere summer insolation minima suggests that orbital forcing has played a first order role in regulating glacial extent in new zealand

surface exposure chronology of the waimakariri glacial sequence in the southern alps of new zealand implications for mis 2 ice extent and lgm glacial mass balance during the late quaternary the southern alps of new zealand experienced multiple episodes of glaciation with large piedmont glaciers reaching the coastal plains in the west and expanding into the eastern alpine forelands here we present a new 10be exposure age chronology for a moraine sequence in the waimakariri valley n canterbury which has long been used as a reference record for correlating glacial events across new zealand and the wider southern hemisphere our data indicate that the waimakariri glacier reached its maximum last glaciation extent prior to 26 ka well before the global last glaciation maximum lgm this was followed by a gradual reduction in ice volume and the abandonment of the innermost lgm moraines at about 17 5 ka significantly we find that during its maximum extent the waimakariri glacier overflowed the avoca plateau previously believed to represent a mid pleistocene glacial surface i e mis 8 at the same time the glacier extended to a position downstream of the waimakariri gorge some 15 km beyond the previously mapped lgm ice limit we use a simple steady state mass balance model to test the sensitivity of past glacial accumulation to various climatic parameters and to evaluate possible climate scenarios capable of generating the ice volume required to reach the full local lgm extent model outcomes indicate that under new zealand s oceanic setting a cooling of 5 c assuming modern precipitation levels or a cooling of 6 5 c assuming a one third reduction in precipitation would suffice to drive the waimakariri glacier to the eastern alpine forelands canterbury plains our findings demonstrate that the scale of lgm glaciation in the waimakariri valley and adjacent major catchments both in terms of ice volume and downvalley ice extent has been significantly underestimated our observation that high lying glacial surfaces so far believed to represent much older glacial episodes were glaciated during the lgm challenges the conventional geomorphic model of glaciation in new zealand where the vertical arrangement of glacial landform associations is used to assign successively older glaciation ages

accuracy of cosmogenic ages for moraines analyses of all published cosmogenic exposure ages for moraine boulders show an average age range of 38 between the oldest and youngest boulders from each moraine this range conflicts with the common assumption that ages of surface boulders are the same as the age of the landform the wide spread in boulder ages is caused by erosion of the moraine surface and consequent exhumation of fresh boulders a diffusion model of surface degradation explains the age range and shows that a randomly sampled small set of boulders n 3 7 will always yield a lower age limit for the moraine the model indicates that for identical dating accuracy six to seven boulders are needed from old and tall moraines 40 000 100 000 yr 50 100 m initial height but only one to four boulders from small moraines 20 000 100 000 yr 10 20 m by following these guidelines the oldest obtained boulder age will be 90 of the moraine age 95 probability this result is only weakly sensitive to a broad range of soil erosion rates our analysis of published boulder ages indicates that 3 of all moraine boulders have prior exposure and 85 of these boulders predate the dated moraine

pebble fabric in an ice rafted diamicton pebble fabric studies on ice rafted diamictons have been limited to general observations with authors noting preferences toward vertical random or horizontal orientations to clarify such observations pebble fabric data were collected from a fossiliferous diamicton of late pleistocene age located on whidbey island washington the ice rafted origin of this unit is supported by several independent characteristics including in situ macrofauna and microfauna conformity with subaqueous lithofacies containing dropstones lower bulk densities and higher void ratios than associated tills soft sediment deformation structures suggestive of iceberg dumping textural gradations and facies relationships analysis using the eigenvalue method indicates that ice rafted fabrics are nearly random with little consistency of vector orientations between sites and without any relationship to the probable direction of glacial flow the weak fabric is mainly the product of settling through the water column and impact wit

the obliquely convergent plate boundary in the south island of new zealand implications for ancient collision zones abstract the alpine fault of new zealand forms the western boundary of a zone of distributed deformation formed by the oblique convergence of continental crust belonging to the pacific and australian plates structural and geodetic data from the alpine fault show that a large proportion of the total plate displacement is accommodated by rapid oblique slip on the fault the remaining displacement is distributed over a 200 km wide zone to the east the collision may be modelled as a two sided deforming orogen with the partitioning of deformation being controlled by erosional differences between the narrow high strain inboard and broad low strain outboard sides in ancient collision zones little evidence may remain of the nature and amount of displacement on the inboard side partitioning of deformation among pre existing structures complicates interpretation of the outboard zone radiometric ages may post date collision by several tens of millions of years and indicate slow isostatic uplift and unroofing collision ages if preserved may be recognized by high uplift rates calculated from muscovite biotite pairs

pegmatite dyke emplacement and the state of stress during cratonization an example from the dharwar craton south india abstract in this study we measured orientations of 797 pegmatite dykes intruding the 2 5 ga koppal pluton dharwar craton south india and use the data to evaluate the state of stress prevalent during dyke emplacement we infer that the dykes were emplaced synchronously with late d3 regional deformation that was controlled by nw se directed shortening dykes within the koppal pluton kp have a restricted range of orientations which is indicative of fluid pressure pf

cosmogenic nuclide chronology of pre last glacial maximum moraines at lago buenos aires 46 s argentina at lago buenos aires argentina 10 be 26 al and 40 ar 39 ar ages range from 190 000 to 109 000 yr for two moraines deposited prior to the last glaciation 23 000 16 000 yr ago two approaches maximum boulder ages assuming no erosion and the average age of all boulders and an erosion rate of 1 4 mm 10 3 yr both yield a common estimate age of 150 000 140 000 yr for the two moraines the erosion rate estimate derives from 10 be and 26 al concentrations in old erratics deposited on moraines that are n760 000 yr old on the basis of interbedded 40 ar 39 ar dated lavas the new cosmogenic ages indicate that a major glaciation during marine oxygen isotope stage 6 occurred in the mid latitude andes the next five youngest moraines correspond to stage 2 there is no preserved record of a glacial advance during stage 4 the distribution of dated boulders and their ages suggest that at least one major glaciation occurred between 760 000 and n200 000 yr ago the mid latitude patagonian glacial record which is well preserved because of low erosion rates indicates that during the last two glacial cycles major glaciations in the southern andes have been in phase with growth and decay of northern hemisphere ice sheets especially at the 100 000 yr periodicity thus glacial maxima are global in nature and are ultimately paced by small changes in northern hemisphere insolation d 2005 university of washington all rights reserved

asynchronous climate change between new zealand and the north atlantic during the last deglaciation climatic fluctuations recorded in antarctica and greenland during the last deglaciation 18 10 ka differ markedly in their timing it remains controversial whether local climate fluctuations recorded in southern mid latitudes relate primarily to northern or southern polar records we present multiproxy results from new zealand that show strong evidence for a minor cooling or slowdown in the rate of warming at the time of the north atlantic late glacial interstadial the younger dryas chronozone in new zealand was a period of resumed warming and increased westerly airflow differences between the hemispheres at this time were probably due to a reorganization of the thermohaline circulation system and associated changes in the meridional temperature gradient

the mis 3 maximum of the torres del paine and ultima esperanza ice lobes in patagonia and the pacing of southern mountain glaciation abstract the timing structure and termination of the last southern mountain glaciation and its forcing remains unclear most studies have focused on the global last glacial maximum lgm 26 5 19 ka time period which is just part of the extensive time frame within the last glacial period including marine isotope stages 3 and 4 understanding the glacial fluctuations throughout the glacial period is a prerequisite for uncovering the cause and climate mechanism driving southern glaciation and the interhemispheric linkages of climate change here we present an extensive n 65 cosmogenic 10be glacier chronology derived from moraine belts marking the pre global lgm extent of the former patagonian ice sheet in southernmost south america our results show the mountain ice sheet reached its maximum extent at 48 0 1 8 ka during the local lgm but attained just half this extent at 21 5 1 8 ka during the global lgm this finding supported by nearby glacier chronologies indicates that at orbital time scales the southern mid latitude glaciers fluctuated out of phase with northern hemisphere ice sheets at millennial time scales our data suggest that patagonian and new zealand glaciers advanced in unison with cold antarctic stadials and reductions in southern ocean sea surface temperatures this implies a southern middle latitudes wide millennial rhythm of climate change throughout the last glacial period linked to the north atlantic by the bipolar seesaw we suggest that winter insolation acting alongside other drivers such as the strength and or position of the southern westerlies controlled the extents of major southern mountain glaciers such as those in southernmost south america

a last interglacial pollen temperature reconstruction central north island new zealand abstract we present new pollen temperature reconstructions for the last interglacial from central north island new zealand using partial least squares regression pls and modern analogue technique applied with the new zealand pre deforestation calibration pollen dataset the pollen bearing organic sequence includes numerous millimetre to decimetre thick tephra mostly from the adjacent tongariro volcanic centre and is overlain by tephric cover beds including the c 25 4 ka cal bp kawakawa oruanui tephra fine resolution pollen and preliminary diatom analyses above and below prominent tephra layers showed that significant vegetation impact followed only the thickest ashfall event 22 cm thickness with vegetation recovery taking several hundred years apart from this changes in the longer term pollen record are likely to be related to climate oscillations that resemble the classic five fold subdivision of mis 5 the warmest interval ascribed to mis 5e was characterised by tall temperate rainforest and occurs at the base of the sequence with mean annual temperatures reaching around 1 1 c higher than present mean annual temperatures declined to 4 c below present during mis 5d and mis 5b and were within 1 2 c of present during mis 5c the pls temperature reconstructions are corroborated by estimates derived independently from elevational changes to vegetation communities corresponding to modern temperature controls inferred from the karioi pollen spectra temperatures reconstructed quantitatively by the modern analogue technique were up to 1 3 c higher for mis 5e mis 5d and mis 5b possibly reflecting weaker modern vegetation analogues for these intervals

the interpretation and classification of subglacially deformed materials abstract a general classification of subglacially deformed materials is proposed based on sediment properties and their relationship to styles of subglacial strain deformation till is defined as homogenized usually diamictic material formed by glacially induced shear of subsole materials three types are recognized type a formed by pervasive ductile deformation type b formed by brittle shear and comminution till produced by the reduction of void space by in situ crushing and abrasion the term glacitectonite is adopted for materials that have undergone subglacial shear but retain some of the structural characteristics of the parent material original structures may be truncated by glacitectonic fabric elements type a or distorted but not truncated type b the principles of strain and material response particle orientation mechanisms fabric development and drainage conditions are reviewed examples of deformation tills and glacitectonites from breidamerkurjokull iceland slettmarkbreen norway loch lomond scotland and east yorkshire england are used to illustrate the nature of subglacially deformed materials and their relationship to former subglacial strain and drainage conditions the geologic evidence suggests a continuum of bed strengths can be recognized in deforming substrata ranging from high strength low strain type b deformation till and comminution till to low strength high strain type a deformation till

near synchronous interhemispheric termination of the last glacial maximum in mid latitudes isotopic records from polar ice cores imply globally asynchronous warming at the end of the last glaciation however 10be exposure dates show that large scale retreat of mid latitude last glacial maximum glaciers commenced at about the same time in both hemispheres the timing of retreat is consistent with the onset of temperature and atmospheric co2 increases in antarctic ice cores we suggest that a global trend of rising summer temperatures at the end of the last glacial maximum was obscured in north atlantic regions by hypercold winters associated with unusually extensive winter sea ice

stratigraphy optical dating chronology irsl and depositional model of pre lgm glacial deposits in the hope valley new zealand abstract a 110 m thick succession of glacial valley fill is described from poplars gully central south island new zealand the section consists of eight lithofacies assemblages that represent different stages of ice occupation in the valley basal sediments record an ice retreat phase followed by a glacial re advance which deposited mass flow diamictons and till a subsequent ice retreat from the site is indicated by the stratigraphic transition from till to thick glacio fluvial gravels this is followed by a probably short lived glacier re advance that caused folding and thrusting of proglacial sediments final glacial retreat from the valley led to the formation of a large proglacial lake in total poplars gully holds evidence for two major ice advances separated by a glacial retreat that resulted in complete ice evacuation from the lower hope valley infrared stimulated luminescence irsl dating on ice proximal sediments from poplars gully yielded six ages between 181 and 115 ka bp our stratigraphic logging and dating results show that the fill sequence was not as previously thought deposited in association with ice advances during the last glacial maximum lgm nor indeed during the last glacial cycle lgm glaciers later overran the fill but we find that the older glacial sequences are considerably more voluminous than those deposited during the last glacial cycle we also show that the mid pleistocene glaciers carved a much deeper valley trough than did glaciers during the lgm taken together these features are likely to reflect a significant difference in the magnitude of successive pleistocene glaciations in the valley with the mid pleistocene ice advances having been considerably larger than those of the last glacial cycle the recognition of the in situ survival of extensive pre mis 5 marine isotope stage deposits in valley troughs that were later occupied by lgm glaciers represents a new feature in the quaternary stratigraphy of the southern alps the results demonstrate that new zealand s commonly very large soft sedimentary valley fills provide a valuable yet largely unexploited terrestrial sedimentary archive of successive glaciations in the region

microbial mineralization of botryoidal laminations in the upper ediacaran dolostones western yangtze platform sw china abstract botryoidal dolostones are abundant in the second member of the upper ediacaran dengying formation in the western yangtze platform although they have been extensively discussed as important host rocks for giant gas reservoirs there is no consensus on the microbial impact on mineralization processes in the botryoidal laminations typical botryoidal laminations were studied under optical microscopes and scanning electron microscopes sems to investigate their origin there are three macroscopic morphological types of botryoidal lamination stromatoid lamination cavity lining lamination and spherical encrusting lamination these three types of lamination are composed of fibrous and bladed crystals growing perpendicular to the botryoidal laminae which have hitherto been implicitly considered to be from abiogenic chemical precipitation there are many lines of new evidence that demonstrate microbial activities in the interbedded dark and bright laminae constituting the laminations in the dark laminae euhedral dolomite rhombs are observed sticking to linear and tubular filaments or wrapped in sheets of extracellular polymeric substances eps with dolomite crystal sizes of generally

exposure dating and glacial reconstruction at mt field tasmania australia identifies mis 3 and mis 2 glacial advances and climatic variability tasmania is important for understanding quaternary climatic change because it is one of only three areas that experienced extensive mid latitude southern hemisphere glaciation and it lies in a dominantly oceanic environment at a great distance from northern hemisphere ice sheet feedbacks we applied exposure dating using 36cl to an extensive sequence of moraines from the last glacial at mt field tasmania glaciers advanced at 41 44 ka during marine oxygen isotope stage mis 3 and at 18 ka during mis 2 both advances occurred in response to an ela lowering greater than 1100 m below the present day mean summer freezing level and a possible temperature reduction of 7 8 c deglaciation was rapid and complete by ca 16 ka the overall story emerging from studies of former tasmanian glaciers is that the mis 2 glaciation was of limited extent and that some glaciers were more extensive during earlier parts of the last glacial cycle copyright 2006 john wiley sons ltd

deformation phenomena in jointed rock the role of rock joints in rock mass deformation phenomena is described individually joints display concave shaped stress closure curves under normal loading and convex shaped stress displacement curves under shear usually accompanied by dilation the deformation behaviour of rock masses depends on the relative magnitudes of these components of closure shear and dilation the deformation of a rock mass may result in dramatic changes in the joint apertures and conductivities conversely changes in joint water pressure cause changes in joint aperture which affect the overall deformation of the rock mass examples of compaction in jointed reservoirs and leakage phenomena in pressure tunnels are cited each of which may be caused by changes in effective stress the presence of rock joints is seen to affect stress slabbing phenomena in tunnels and is the suspected cause of depth dependent contrasts of stress in sedimentary rocks the phenomenon of hydraulic shearing of joints is discussed with particular

quaternary marine terrace chronology north canterbury new zealand using amino acid racemization and infrared stimulated luminescence extensive marine terraces along the north canterbury coast of the south island of new zealand record uplift in this tectonically active area although the terraces have been studied previously applications of quaternary geochronological techniques to the region have been limited we use infrared stimulated luminescence irsl amino acid racemization aar and radiocarbon to determine ages of terraces at three locations glenafric motunau beach and haumuri bluff we develop an aar calibration curve for the mollusk species tawera spissa from sites of known age including the sedimentary sequence of the whanganui basin bayesian model averaging of the results is used to estimate ages of marine shells from the north canterbury terraces by using both irsl and aar we are able to confirm ages using two independent dating methods and to identify one irsl result that is likely in error we develop new age estimates for the marine terraces of north canterbury and propose correlations between sites this terrace chronology differs significantly from most previous studies highlighting the importance of numerical dating the most extensive terraces are from marine isotope stages miss 5a and 5c with partial reoccupation of one terrace during mis 3 whereas mis 5e terraces are notably lacking among those dated

the longmenshan tectonic complex and adjacent tectonic units in the eastern margin of the tibetan plateau a review abstract the longmenshan tectonic complex lstc along the eastern margin of the tibetan plateau the site of devastating earthquakes such as the magnitude 8 0 wenchuan earthquake on 12 may 2008 preserves an exceptionally complete history of the tectonic evolution of the yangtze block and its relations to adjacent tectonic units due to sequential tectonic superposition and tectonic reactivation the tectonic nature of the lstc and in particularly the older history has been profoundly debated and many different tectonic models have been proposed herein we summarize the current understandings of the major tectonic events that have shaped this important tectonic complex highlighting problems left to be solved by future work including 1 the nature and constraints for at least 6 regional tectonic events i e building of the metamorphic basement art the columbia nuna supercontinent pt1t the rodinia supercontinent pt3t the paleozoic passive continental margin pzt the paleotethys orogeny mzt and the neotethys orogeny kzt 2 metamorphic basement exposures and their tectonic implications including rock types and geochronological constraints for the archean paleoproterozoic and neoproterozoic basements 3 nature of the present lstc and its affinity with adjacent tectonic units 4 consideration of the ne striking longmenshan thrust belt and arcuate shape yanyuan muli thrust belt as parts of a single tectonic feature 5 mountain basin coupled systems recording past tectonic eposides we draw the following conclusions and tectonic models based on published research combined with our own recent studies 1 the well preserved archean yudongzi gneiss group in the lstc has a genetic affinity with the kongling group and thus belongs to the yangtze block 2 the paleoproterozoic hejiayan group juxtaposed adjacent to the archean yudongzi group may represent a 2000 1800 ma orogenic belt which corresponds to the supercontinent nuna columbia amalgamation event 3 a neoproterozoic trench arc basin system which is reconstructed based on identification of a neoproterozoic ophiolite complex arc type magmatic rock assemblages and volcaniclastic basinal deposits along the western margin of the yangtze block and the lstc may represent the record of eastward subduction of the neoproterozoic mozambique oceanic lithosphere beneath the yangtze block during the assembly of the rodinia supercontinent 4 a complete bidirectional wilson cycle was reconstructed by the formation of the late permian to the middle late triassic back arc ganze litang rift and ocean following the early paleozoic mianlue continental rift and ocean and subsequent closure of the ocean basin by simultaneous bidirectional northward and southwestward subduction and later collision this relatively uncommon bidirectional wilson cycle might be attributed to the formation of the three armed rift system in the eastern paleotethys associated with the late permian eemeishan large igneous province in the lstc 5 a three stage tectonic sequence of in sequence imbricate thrust in the lstc during india eurasian collisional orogeny at 55 15 ma extrusion from 15 to 5 ma and the plateau uplift since 5 ma resulting from lower crustal channel flow is proposed for the formation of the present lstc

a review of new zealand palaeoclimate from the last interglacial to the global last glacial maximum abstract results from terrestrial and marine palaeoclimate proxies are integrated to reconstruct palaeoclimate variations in new zealand from the last interglacial to the global last glacial maximum glgm by combining data from 21 speleothems we have constructed composite o c stable isotope sequences from 0 to 88 5 ka bp and from 107 8 to 128 2 ka bp the gaps in the sequence a 19 3 ka break in coverage in mis 5b c and a 2 97 ka gap in mis 5a preclude the construct of a continuous record so data were referenced to a common scale by normalising individual records subtracting means and dividing by standard deviation overlapping records were then merged chronologically these records were compared to integrated summer insolation for 45 s and to terrestrial and marine environmental proxies available for the new zealand region the mis 5e thermal maximum in new zealand was around 128 122 kiloyears bp ka bp and therefore similar in timing to the last interglacial in australia southern europe and greenland temperatures in parts of the north island may have been 2 3 c warmer than present and the sea rose 3 6 m above modern level in mis 5d and 5b cool conditions with glacial advances occurred in the south island but from about 87 to 73 ka in mis 5a warmth within 2 c of present characterised most of the interstadial locally termed the otamangakau interstadial conditions then cooled rapidly and culminated in a mis 4 glacial advance that was the greatest of the new zealand last glacial cycle nzlgm the climate was cool to cold and while wet in westerly windward locations may have been dry in the east combined australian and new zealand evidence suggests glacial culmination around 67 62 ka this regional lgm coincided with severe cooling in europe during mis 3 conditions were very variable the climate in eastern north island hawke bay and the bay of plenty at the start of mis 3 was similar to the holocene and the period 61 43 ka was relatively mild overall and is termed the aurora interstadial although it contained a short interval of mountain glacier expansion around 49 47 ka after 43 ka conditions cooled again with a glacial advance from 42 to 38 ka before a return to milder but still cool conditions during the moerangi interstadial from 37 to 31 ka after this conditions deteriorated at the lead in to the glgm the maximum glacial advance occurred in late mis 3 between 31 and 29 ka the glacial onset was abrupt with te anau glacier in fiordland one of the largest in the southern alps taking only about 2000 years to achieve its maximum glgm depth probably because conditions were wet as well as cold but stable isotope data suggest that the climate then became drier while remaining cold and the glacier progressively ablated such that its surface had lowered 390 m by the start of mis 2 and by 600 m by ca 18 ka the glgm maximum in new zealand may have led the terrestrial ice sheet lgm in the northern hemisphere by a few thousand years possibly because alpine glaciers respond more rapidly to climate change than continental ice sheets the culmination of the glgm in nz occurred in mis 3 about 12 000 years before global ice volume reached its peak as determined by the marine stable isotope record the marine glgm by the time global ice volume was at a maximum 19 ka glaciers had almost disappeared from major fiordland valleys in new zealand whereas polar ice sheet records have revealed a bi polar see saw this is not so evident in the mid latitudes because some temperate zone inter hemispheric climate events coincide closely in time perhaps the see saw effect diminishes with distance from the poles

origin of mafic intrusions in the micangshan massif central china implications for the neoproterozoic tectonic evolution of the northwestern yangtze block abstract the mafic intrusions exposed in the micangshan massif preserve important information pertaining to the neoproterozoic tectonic evolution along the northwestern margin of the yangtze block in this paper we report new la icp ms zircon u pb ages lu hf isotopes and whole rock compositions for mafic sills in the micangshan massif to understand their petrogenesis and supplement the regional tectonic evolution xenocrystic zircon grains from two mafic sill samples yield weighted mean ages of 860 4 ma and 858 5 ma respectively suggesting the maximum emplaced age of the mafic sills was at ca 860 ma a granitic dyke sample which intruded into the mafic sills yields a crystallization age of 799 4 ma implying the minimum emplacement of the mafic sills was at ca 800 ma these results indicate that the mafic sills were formed within the span of ca 860 800 ma geochemical results show that most of these mafic sills are tholeiitic in composition and are characterized by low to moderate feototal and tio2 contents as well as moderate to high mgo contents and mg values they display distinct enriched light rare earth element lree patterns variable remarkable enrichment in large ion lithophile elements liles e g cs and ba and evident depletion of high field strength elements hfses e g nb ta and p resembling signatures of typical subduction related basaltic rocks in addition these sills exhibit comparatively high nb ta moderate nb yb as well as low nb la th yb and nb y ratios indicating that they probably originated from partial melting of a previously metasomatized mantle wedge source these observations together with regional tectonics suggest that these mafic sills in the micangshan massif might be formed in a subduction related continental arc setting therefore combining our new data with available results from previous studies in the adjacent regions our study supports the dominant subduction related tectonics along the northwestern margin of the yangtze block during the early neoproterozoic time

cosmogenic 10be and 26al exposure ages of moraines in the rakaia valley new zealand and the nature of the last termination in new zealand glacial systems new zealand glaciers reached their last glacial maximum position at or before 25 ka and as early as 23 ka commenced a slow and continual retreat new cosmogenic exposure ages and field mapping from the rakaia valley in the south island suggest that extensive ice survived well into the latter half of the last glacial interglacial transition 18 11 ka with the post 15 ka period inferred to have near holocene climate conditions based on ecological proxy data by as late as 15 5 ka glacier termini had retreated as little as 5 10 km from glacial maximum positions numerous minor ice still stand positions and oscillations are recognized but the record specifically excludes evidence for either a major climatic amelioration at 15 16 ka or a significant glacial re advance during the antarctic cold reversal acr or the younger dryas yd we conclude that the currently widespread interpretation of an episodic new zealand glacial record since the lgm is an artifact of valley dependent retreat processes pro glacial lake formation and local site conditions combined to give an apparent but misleading picture of glacial retreat punctuated by major climatically driven re advances copyright 2010 elsevier b v all rights reserved

cavity filling dolomite speleothems and submarine cements in the ediacaran dengying microbialites south china responses to high frequency sea level fluctuations in an aragonite dolomite sea speleothems mostly composed of calcium carbonate are widely present in modern karst originated caves but have rarely been reported in palaeokarst systems this study presents a novel type of dolomite speleothem and subsequent submarine dolomite cement which are widely present in the upper ediacaran dengying formation in the upper yangtze area these precipitated materials occur in the cavity system that cuts across several peritidal cycles the interconnected cavity networks with irregular shapes embayed walls internal breccias on cavity floor and their preferential development in the shallower cycle tops for example tepee deformed beds suggest that they were initially generated by subaerial dissolution as the earliest infills the hemispherical protrusions icicle like pendants and ground up columns show similar morphological features and occurrence patterns to the cave popcorn stalactites and stalagmites respectively thus these earliest infills are speleothems resulting from associated meteoric precipitation during subaerial exposure the isopachous growth pattern of subsequent more extensive fibrous dolomite cements points to a submarine diagenetic environment in which they were precipitated microscopically the micritic to micro crystalline dolomite acicular dolomite in speleothems and the subsequent fibrous dolomite share similar crystal fabrics to metastable precursors for example mg calcite meanwhile the carbon oxygen isotope compositions of the speleothem and fibrous dolomite although partly altered by burial diagenesis share a large overlap with host rock and coeval marine carbonates all over the yangtze platform for these reasons these speleothems and fibrous cements are considered to have been initially precipitated as metastable carbonate precursors in meteoric and submarine environments respectively and stabilized during submarine mimetic dolomitization the cyclic occurrence of cavity systems filled with speleothems and submarine cements reflects periodic subaerial exposure and marine flooding of broad tidal flat in the upper yangtze area driven by high frequency sea level fluctuations furthermore the neoproterozoic seawater chemistry that favoured early dolomitization of carbonate precursor mineralogies was an advantage for the preservation of fabrics from metastable precursor minerals

paleoclimate climate change across the hemispheres climate records from greenland ice cores have shown that climate has changed rapidly and drastically throughout the last glacial period on a millennial time scale in his perspective shackleton highlights the report by blunier and brook who have correlated the greenland records with an antarctic record there is a systematic difference in the character and timing of temperature changes in the two hemispheres although the mechanism linking the hemispheres remains uncertain absolute dating is essential

lithofacies types and vertical profile models an alternative approach to the description and environmental interpretation of glacial diamict and diamictite sequences abstract increased knowledge of modern glacial depositional environments has resulted in rapidly evolving classifications of glacial tills these are based to a large degree on theoretical considerations of likely depositional processes the classifications are sophisticated and more advanced than the establishment of simple field criteria whereby individual till facies can be identified in quaternary and pre quaternary successions this situation is compounded in many quaternary terrains by the continued description of tills in terms of laboratory derived analytical data only reflecting a traditional interest in stratigraphic correlation rather than reconstruction of depositional environment detailed sedimentological logging of lithofacies is rarely undertaken there is thus considerable confusion as to what is being described or sampled when analytical data are presented for many pleistocene tills the same remarks apply to pre pleistocene tillites a lithofacies code is presented here for the rapid description and visual appraisal of field sequences or drill cores containing unconsolidated diamicts or lithified diamictites the term till is not used as it has a strict genetic definition referring to direct aggregation and deposition by glacier ice use of a four part code in conjunction with codes already published for fluvial sediments allows fundamental field properties to be depicted independent of genetic terminology and provides a firm basis for subsequent environmental interpretation and analytical work the value of this approach is illustrated by comparing a representative suite of vertical profiles of diamict assemblages deposited by modern grounded glaciers with a classic late pleistocene glacigenic sequence at scarborough bluffs ontario

the last glacial maximum lgm in western south island new zealand implications for the global lgm and mis 2 abstract the morainic and outwash deposits of the larrikins la and moana mn formations in north westland are correlated with the m5 t5 and m6 t6 deposits in south westland the la m5 deposits resulted from two separate otira glaciation glacial advances la 1 m5 1 la 2 m5 2 of essentially similar extents pollen sequences in peats and coverbeds extending from before to after the kawakawa tephra 26 500 cal yr bp indicate an extensive period of cold with a slight amelioration beginning shortly before tephra deposition this amelioration which is supported by interpretation of coverbed sequences in south westland separates the la 1 m5 1 and la 2 m5 2 advances the three westland glacial advances la 1 m5 1 la 2 m5 2 and mn m6 culminated at ca 28 000 21 500 and 19 000 cal yr bp the last being followed by major rapid glacier retreat pollen and caco 3 records from dsdp 594 east of the south island reflect contemporary glacier fluctuations on the east side of the southern alps they show the last major cold period as lasting from ca 34 000 to ca 16 000 years ago a period starting before the culmination of the la 1 m5 1 advance and ending later than the beginning of glacier retreat from the mn m6 advance the period from the la 1 m5 1 culmination to the mn m6 culmination represents the lgm in new zealand a slightly longer lgm is recorded in chile and a long lgm may also be indicated in australia a long lgm in the southern hemisphere is supported by the global sea level curve and by the regional antarctic temperature criteria of the vostok ice core these different records indicate a southern hemisphere lgm beginning at least as early as 27 000 years ago much earlier than the ocean last isotope maximum lim from 21 500 to 18 000 years ago the beginning of mis 2 defined primarily from deep sea benthic 18 o at 24 000 years is well after the beginning of ice advances leading to the southern hemisphere lgm a review of global land and ocean correlations is desirable

triaxial compression experiments on intact veined andesite abstract a comprehensive experimental program was instigated to test intact veined andesite from the el teniente mine chile under triaxial compression with confining pressure ranging from 2 to 60 mpa the experimental program established that the veins acted as weak mechanical components in the specimens promoting rock fracture under stress the experimental results indicated that the stress thresholds identifying the onset of dilatancy and the transition from the stable to unstable fracturing were higher in intact veined rock than in intact rock the observed behaviour illustrated a significant departure from intact rock where the onset of acoustic emissions ae correlates with the onset of specimen dilatancy the experimental results from intact veined rock indicated that the onset of ae correlated with the crack damage stress the departure from the behaviour of intact rock is attributed to the presence of veins

mineralogy and geochemistry of surface sediments from the bengal fan indian ocean abstract the mineralogy and composition of 75 sediment samples from the bengal fan andaman sea and the eastern flanks of the upper nicobar fan have been determined sediments from the upper and middle bengal fan are mainly terrigenous and derived from the ganges brahmaputra river system whereas sediments from the andaman sea and the eastern flank of the upper nicobar fan vary from terrigenous to largely biogenic for the terrigenous sediments the continental influence is illustrated by the distribution of the major elements excluding ca which decrease away from the source the ti al and fe al ratios of the sediments are higher in samples from the cast coast of india than from the fans indicating the influence of material from the deccan basalts as well as from mafic rocks of the indian peninsula in the clay mineral fraction of upper bengal fan sediments illite and chlorite are the dominant constituents with minor amounts of smectite and traces of kaolinite illite is mainly a weathering product of lithic material from the himalaya and is transported by the ganges brahmaputra river system smectite is the dominant constituent of the sediments adjacent to the indian peninsula

dating the late cenozoic glacial sequence pieman river basin western tasmania australia abstract the pieman river basin western tasmania displays one of the most complete middle to early pleistocene glacial sequences from a southern hemisphere mid latitude site most of the glacial deposits exceed the 14 c limit although mapping of the depositional units using morphostratigraphic post depositional weathering criteria and magnetostratigraphy shows that the sediments of the boco and bobadil glaciation were deposited during the brunhes normal chron 275 kyr late last margaret glaciation advances in the pieman basin are much more restricted in extent and display evidence for multiple stillstand readvance phases during the decay of the system with most of the ice having disappeared by 14 kyr bp

rock mass characterization and assessment of block forming geological discontinuities during caving of primary copper ore at the el teniente mine chile abstract the primary copper ore at the el teniente mine is very competent and massive it is a rock with almost no open discontinuities nevertheless there is a high frequency network of small scale veins coupled with widely spaced faults a research investigation was implemented to determine what discontinuities are the most relevant in the rock mass disassembly process during cave mining rock mass characterization was undertaken at four different scales within the rock mass in particular the block forming discontinuities were characterized by studying a significant number of blocks at the caving draw points two relevant discontinuity characteristics have been found the data suggest that discontinuities having approximately less than 1 3 of hard minerals as infill and thicknesses greater than or equal to 2 mm are weaker and more likely to define blocks during caving and the subsequent comminution process the infill characteristics have been used to characterize rock mass quality in different sectors and the results are in accordance with actual observations at the mine site

botryoidal aragonite and its diagenesis botryoidal aragonite is a spectacular growth form occurring as mamelons up to 100 mm in diameter three examples of this particular carbonate cement have been discovered in two distinct areas in new caledonia small scale mamelons have been recognized within pleistocene reefal terraces at ouvea an island of the loyalty archipelago and in the red sea large scale mamelons of botryoidal aragonite exist within pleistocene reefal terraces along the um gheig region of the egyptian coast in addition a similar botryoidal cement partly dolomitized but exhibiting aragonite relics occurs within a miocene reef in the same region mamelons of botryoidal aragonite are isolated and or coalescent but grow only on fixed substrates they occur within cavities of varied origin their fabrics are characterized by fans of elongate euhedral crystals of aragonite fibres botryoidal aragonite can be preceded or followed by other types of cements or internal sediment despite similar mineralogy petrography and ultrastructure there are differences between the fabrics of the pleistocene botryoids from the red sea and ouvea and the miocene botryoids from the red sea the former are of submarine origin as confirmed by the strontium content 8500 10 500 ppm and isotopic composition 18o between 0 10 and 0 19 pdb the latter related to a miocene karst are rich in strontium average 13 600 ppm and have an isotopic composition average 18o 10 50 pdb indicative of non marine precipitation diagenesis of these botryoidal aragonites consists of slight dissolution for pleistocene botryoids and mineralogical transformation for the miocene botryoids the latter exhibit the diagenetic sequence aragonite calcite dolomite the aragonite to calcite transformation is a dissolution reprecipitation process the void distribution and size influencing the distribution and the size of the replacement calcite crystals

geochronological constraints on stratigraphic correlation and oceanic oxygenation in ediacaran cambrian transition in south china the continuous late ediacaran early cambrian deep water successions of south china archive the complete evolution of seawater chemical conditions in the deep ocean during this critical time interval however the geochemical data from these poorly fossiliferous and condensed successions lack high resolution stratigraphic constraints hampering their interpretation for the spatio temporal evolution of the sweater chemistry in this time interval in this study we report a new sims and ca id tims zircon u pb age 545 76 0 66 ma total uncertainty for an ash bed at the lower liuchapo formation in the deep water longbizui section in western hunan province the new age suggests that the lower and the middle upper parts of the liuchapo formation in the deep water facies can be correlated with the lower dengying formation and the upper dengying lower zhujiaqing formations in the shallow water facies respectively this correlation implies that the correlative horizon of the ediacaran cambrian boundary in the deep water facies in south china is likely located near the base of a widespread negative 13corg excursion at the upper liuchapo formation based on our new geochronological framework the compilations of fe speciation mo and u data indicate that the deep ocean was characterized by widespread anoxic ferruginous water with intermittent euxinic water impinged on the middle lower slope in ediacaran cambrian transition and significant oxygenation events occurred in 533 520 ma the compilations do not support any significant oceanic oxygenation events in 551 535 ma

dynamics of pacific plate crust in the south island new zealand zone of oblique continent continent convergence here we analyze topographic and fission track data to quantify the response of the surface of the pacific plate in south island new zealand to late cenozoic oblique continental convergence across the alpine fault over the central 350 km length of the southern alps mountain chain we derive and map the rates of mean surface uplift the rates of working associated with mean surface uplift during the late cenozoic mountain building the amounts and rates of denudation and consequent isostatic rebound and the tectonic component of rock uplift the rate of mean surface uplift ranges from 0 3 mm yr over most of the area east of the main divide the highest rates of mean surface uplift occur to the southeast of the regions of highest mean elevation and relief the rate of working against gravity during uplift of the mean surface ranges from 2 5 mw m 2 in the southwest to 10 mw m 2in the central eastern parts of the alps areas of lower mean elevation uplifted most recently have received rates of energy input similar to that of areas of higher mean elevation where uplift started earlier the amount of denudation is large compared with the mean surface uplift and ranges from 18 km adjacent to the alpine fault to 2 km along the southeast margin of the southern alps the rate of denudation ranges from 2 5 to 0 5 mm yr with increasing distance from the alpine fault across the alps to the southeast the amount of isostatic uplift ranges from a maximum of 14 km adjacent to the alpine fault to 2 km along the southeast margin of the alps the tectonic component of uplift varies from 4 km along the alpine fault to 1 km along the eastern margin of the alps

stratigraphic and geomorphologic evidence of three mis 2 glacial advances in the south fork hoh river valley olympic mountains washington usa the geomorphology and stratigraphy of the south fork hoh river sf hoh olympic mountains washington allow for greater understanding of marine oxygen isotope stage 2 mis 2 ice fluctuations glacial dynamics and sedimentation age control from optically stimulated luminescence and radiocarbon dating constrains deposited sediments associated with four late pleistocene ice marginal positions that formed under reduced ice volume conditions compared with mis 3 5 glaciers in the same drainage the earliest mis 2 ice margin extended into the main hoh river valley pre sf 1 28 ka to 23 0 ka after retreat the ice occupied three closely spaced ice marginal positions sf 1 3 that range in age from 22 0 ka to shortly after 18 7 ka while the sf 1 and sf 3 positions were previously identified as the twin creeks i and ii positions the intermediate sf 2 position had not been recognized moraines are composed of poorly sorted but stratified sediment and few tills diamicton units show evidence of water reworking this research documents a detailed record of mis 2 glaciation in a maritime setting in western north america and provides evidence of rapid mis 2 ice marginal fluctuations that likely reflect responses to millennial scale climatic fluctuations and may be relevant to understanding other complex mis 2 moraine sequences

a cosmogenic nuclide chronology of the last glacial transition in north west nelson new zealand new insights in southern hemisphere climate forcing during the last deglaciation we present a new glacial chronology for the last glacial interglacial transition c 20 to 10 ka from the cobb valley nw nelson new zealand based on a suite of 10be and 26al cosmogenic exposure ages this chronology describes one of the most comprehensive deglaciation sequences from a late quaternary valley system in the southern hemisphere we chronicle the decay from the last local glacial maximum as follows onset of the last deglaciation that commenced no earlier than 18 19 ka followed by numerous short term still stands and or minor re advances over the ensuing 3 4 kyr and complete evacuation of ice by 14 ka we find no evidence to indicate a late glacial re advance commensurate with the northern hemisphere younger dryas chronozone the absence of a major glacial re advance in this valley during the latter stages of the last glacial interglacial transition lgit precludes a thermal decline in excess of about 3 c and suggests no decline the absence of late lgit re advances in the mountains of north west nelson while deglacial readvances occurred in the main ranges of the southern alps can be best explained if westerly wind forcing rather than large scale thermal decline is the primary control on glacier fluctuations at least during the deglaciation these findings challenge models of global climate change predicated on synchrony of millennial scale glacial transitions due to thermal changes between northern and southern hemispheres

regional insolation forcing of late quaternary climate change in the southern hemisphere southern new zealand positioned within the important southwesterly wind system is a prime site for examining interhemispheric linkages in climate change a series of cores drilled in the okarito pakihi peat bog now provides a continuous record of vegetation and climate change that may become a benchmark for the region the data include clear evidence for modification of the global climate change signal in the southern hemisphere by local variation in the intensity of solar radiation in agreement with the milankovitch orbital forcing hypothesis1 it is often assumed that glacial interglacial climate transitions occurred synchronously in the northern and southern hemispheres of the earth it is difficult to test this assumption because of the paucity of long continuous climate records from the southern hemisphere that have not been dated by tuning them to the presumed northern hemisphere signals2 here we present an independently dated terrestrial pollen record from a peat bog on south island new zealand to investigate global and local factors in southern hemisphere climate changes during the last two glacial interglacial cycles our record largely corroborates the milankovitch model of orbital forcing but also exhibits some differences in particular an earlier onset and longer duration of the last glacial maximum our results suggest that southern hemisphere insolation may have been responsible for these differences in timing our findings question the validity of applying orbital tuning to southern hemisphere records and suggest an alternative mechanism to the bipolar seesaw for generating interhemispheric asynchrony in climate change

cosmogenic nuclide ages for last glacial maximum moraine at schnells ridge southwest tasmania abstract moraines on schnells ridge southwest tasmania have been dated using in situ 10be an age of 19 400 600 yr is indicated for the well preserved innermost moraine from consistent measurements on four large quartzite boulders this corresponds closely with exposure ages reported by t t barrows et al 2002 quaternary science reviews 21 159 173 for last glacial maximum glacial features farther north in tasmania and southeast australia in contrast ages between 39 000 and 141 000 yr were obtained from a series of boulders on a more extensive outer moraine indicating that this has had a more complex history

high precision 10be chronology of moraines in the southern alps indicates synchronous cooling in antarctica and new zealand 42 000 years ago millennial scale temperature variations in antarctica during the period 80 000 to 18 000 years ago are known to anti correlate broadly with winter centric cold warm episodes revealed in greenland ice cores however the extent to which climate fluctuations in the southern hemisphere beat in time with antarctica rather than with the northern hemisphere has proved a controversial question in this study we determine the ages of a prominent sequence of glacial moraines in new zealand and use the results to assess the phasing of millennial climate change forty four 10be cosmogenic surface exposure ages of boulders deposited by the pukaki glacier in the southern alps document four moraine building events from marine isotope stage 3 mis 3 through to the end of the last glacial maximum 18 000 years ago lgm the earliest moraine building event is defined by the ages of nine boulders on a belt of moraine that documents the culmination of a glacier advance 42 000 years ago at the pukaki locality this advance was of comparable scale to subsequent advances that from the remaining exposure ages occurred between 28 000 and 25 000 at 21 000 and at 18 000 years ago collectively all four moraine building events represent the lgm the glacier advance 42 000 years ago in the southern alps coincides in antarctica with a cold episode shown by the isotopic record from the epica dome c ice core between the prominent a1 and a2 warming events therefore the implication of the pukaki glacier record is that as early as 42 000 years ago an episode of glacial cold similar to that of the lgm extended in the atmosphere from high on the east antarctic plateau to at least as far north as the southern alps 44 s such a cold episode is thought to reflect the translation through the atmosphere and or the ocean of the anti phased effects of northern hemisphere interstadial conditions to the southern half of the southern hemisphere regardless of the mechanism any explanation for the cold episode at 42 000 years ago must account for its widespread atmospheric footprint not only in antarctica but also within the westerly wind belt in southern mid latitudes

formation of the waiho loop terminal moraine new zealand we present an analysis of the formation and evolution of the waiho loop terminal moraine recent work has shown that the loop comprises mainly rock avalanche material and suggested its formation was associated with a rock avalanche driven glacier advance new evidence from shallow seismic studies between the range front and the loop suggests i that the presence of a basal trough critically influences glacier behaviour and moraine formation and ii that the volume of the waiho loop is significantly greater than previously thought a one dimensional dynamic ice flow model is used to test two rock avalanche based scenarios for the formation of the loop first that a rock avalanche caused a significant advance of the glacier terminus from a location within the confined mountain valley to the loop and second that the rock avalanche occurred while the glacier was retreating with its terminus close to the position of the loop it is shown that this terminal moraine was not the result of a glacier advance

glaciolacustrine deposits formed in an ice dammed tributary valley in the south central pyrenees new evidence for late pleistocene climate abstract combined geomorphic features stratigraphic characteristics and sedimentologic interpretation coupled with optically stimulated luminescence osl dates of a glacio fluvio lacustrine sequence linas de broto northern spain provide new information to understand the palaeoenvironmental significance of dynamics of glacier systems in the south central pyrenees during the last glacial cycle 130 ka to 14 ka the linas de broto depositional system consisted of a proglacial lake fed primarily by meltwater streams emanating from the small sorrosal glacier and dammed by a lateral moraine of the ara trunk glacier the resulting glacio fluvio lacustrine sequence around 55 m thick is divided into five lithological units consisting of braided fluvial gravel deposits lake margin gravel and sand deltaic deposits and distal lake silt and clay laminites facies associations evolution of the depositional environment reflects three phases of progradation of a high energy braided fluvial system separated by two phases of rapid expansion of the lake fluvial progradation occurred during short periods of ice melting lake expansion concurred with ice dam growth of the trunk glacier the first lake expansion occurred over a time range between 55 9 ka and 49 11 ka and is consistent with the age of the viu lateral moraine 49 8 ka which marks the maximum areal extent of the ara glacier during the last glacial cycle these dates confirm that the maximum areal extent of the glacier occurred during marine isotope stages 4 and 3 in the south central pyrenees thus before the last glacial maximum the evolution of the linas de broto depositional system during this maximum glacier extent was modulated by climate oscillations in the northern iberian peninsula probably related to latitudinal shifts of the atmospheric circulation in the southern north atlantic ocean and variations in summer insolation intensity

new chronological constraints for cryogenian to cambrian rocks in the three gorges weng an and chengjiang areas south china abstract the neoproterozoic and cambrian were two of the most dramatic periods in the history of the earth because large multi cellular animals first appeared then in the so called cambrian explosion to better understand this event many paleontological and geochemical studies now focus on rocks in south china because of the fossiliferous succession and good exposure since the recognition of the yangtze gorges and chengjiang area as type localities of the sinian ediacaran and meishucunian early cambrian systems both sections have been intensively investigated in order to decipher the relationships between the evolution of life and surface environmental changes it is necessary to understand their paleontological geochemical and geo chronological constraints this study presents new chronological constraints for the cryogenian to cambrian rocks in the three gorges weng an and chengjiang areas south china we discovered two tuff layers one at the base of the shuijingtuo fm at three gorges and the other at the bottom of the dahai member in chengjiang in addition we collected sandstones from neoproterozoic strata in the three gorges chengjiang and weng an areas for provenance analysis zircons separated from the tuff layers provide new nano sims u pb ages of 526 4 5 4 ma at the base of the shuijingtuo fm and 523 9 6 7 ma at the bottom of the dahai member the tuffaceous beds occur at an unconformity and nodules are common in the three gorges meishucun and taoying sections indicating that major and relatively wide scale volcanic and sedimentological events occurred at ca 525 ma moreover carbonate carbon isotope chemostratigraphies at morocco siberia three gorges and meishucun display different characteristics during the tommotian one possibility is that the south china ocean was separated from an outer ocean at that time detrital zircons in sandstones have age populations at ca 2 7 1 8 1 6 1 0 and from 0 9 to 0 75 ga indicating that the paleo hinterland of the nanhua and kangdian rift basins was geologically complex despite the lack of ca 1 6 ga rocks in the yangtze and cathaysia blocks these data are nevertheless interpreted to indicate derivation of the zircons from basement rocks in the yangtze craton

polyphase deformation at an oscillating ice margin following the loch lomond readvance central scotland uk the sequence of glacitectonic disturbance of an ice contact delta during the initial stages of deglaciation following the loch lomond readvance is examined an ice marginal gilbert type deltaic sequence exposed in drumbeg quarry drymen scotland displays a polyphase deformation history that is punctuated by periods of erosion and deposition progradation of the delta into ice dammed lake blane led to a temporary stabilisation of the loch lomond glacier during recession from its loch lomond readvance maximum position this was followed by a ne directed readvance into the ice contact slope of the delta resulting in proglacial deformation d1 and the formation of a thrust block ridge in the middle to outer parts of the delta complex sedimentation continued uninterrupted subsequent retreat of the ice was accompanied by erosion and deposition as the ice contact slope was re established a second phase of readvance resulted in subglacial ductile shearing d2 and deposition of a diamicton during ne directed over riding of the delta sediments by the ice the direction of ice flow subsequently changed towards the se this was followed by a further retreat of the ice and re establishment of the fan delta complex the complexity of the glacitectonic sequence at drumbeg records the impact of an oscillating ice margin responding to either relative deepening of the lake waters in contact with the receding snout or climatic controls it provides further evidence that many of the scottish highland glaciers were subject to active recession rather than stagnation at the end of the loch lomond readvance

thickness and spatial distribution of veins in a porphyry copper deposit rosia poieni romania abstract a statistical analysis of the vein thickness distributions of veins in the rosia poieni porphyry copper deposit romania indicates that vein thickness data conform to a power law distribution whereas the spatial distribution of veins follows a negative exponential law a high clustering of the veins is indicated by both the spacing distribution and the cv values the similar vein densities observed at the open pit scale are representative of a saturation level of vein nucleation differences in the spacing distribution and in the mean vein thickness are explained by different initial nucleation rates in the deepest and the lowest parts of the porphyry copper the highly clustered organization of the system is explained by vein linkage processes during their growth and modification of the fluid pressure and local stress during the hydrofracturing

dolomite formation within microbial mats in the coastal sabkha of abu dhabi united arab emirates microbial mediation is the only demonstrated mechanism to precipitate dolomite under earth surface conditions a link between microbial activity and dolomite formation in the sabkha of abu dhabi has until now not been evaluated even though this environment is cited frequently as the type analogue for many ancient evaporitic sequences such an evaluation is the purpose of this study which is based on a geochemical and petrographic investigation of three sites located on the coastal sabkha of abu dhabi along a transect from the intertidal to the supratidal zone this investigation revealed a close association between microbial mats and dolomite suggesting that microbes are involved in the mineralization process observations using scanning electron microscopy equipped with a cryotransfer system indicate that authigenic dolomite precipitates within the exopolymeric substances constituting the microbial mats in current models microbial dolomite precipitation is linked to an active microbial activity that sustains high ph and alkalinity and decreased sulphate concentrations in pore waters such models can be applied to the sabkha environment to explain dolomite formation within microbial mats present at the surface of the intertidal zone by contrast these models cannot be applied to the supratidal zone where abundant dolomite is present within buried mats that no longer show signs of intensive microbial activity as no abiotic mechanism is known to form dolomite at earth surface conditions two different hypotheses can reconcile this result in a first scenario all of the dolomite present in the supratidal zone formed in the past when the mats were active at the surface in a second scenario dolomite formation continues within the buried and inactive mats in order to explain dolomite formation in the absence of active microbial metabolisms a revised microbial model is proposed in which the mineral template properties of exopolymeric substances play a crucial role

near synchroneity of new zealand alpine glaciations and northern hemisphere continental glaciations during the past 750 kyr the brunhes magnetochron 0 730 kyr at deep sea drilling project site 594 off eastern south island new zealand comprises up to 100 m of alternating units of pelagic and hemipelagic ooze formed during interglacial and glacial periods respectively the youngest hemipelagic interval corresponds to glacial isotope stage 2 and can be correlated with extensive glacial and glacio fluvial deposits of the late last glaciation 27 13 kyr bp on south island inferring the same genetic link for the other hemipelagic sediment units down core we show here that as many as 12 major episodes of expanded alpine glaciation have occurred on south island in the past 730 kyr each of these glacial episodes coincided with a period of significant 18o enrichment 2 in the core resulting from changes in ocean isotope composition associated with major growth phases of the northern hemisphere ice sheets the inferred history of alpine glaciations on this remote south pacific island appears to be closely phase locked 3 kyr to world wide climate changes

subglacial till formation sedimentary characteristics and classification we review the major subglacial till forming processes as presently understood by glacial researchers and define the parameters within which tills are produced and reconcile them with sedimentary end members processes of deformation flow sliding lodgement and ploughing coexist at the base of temperate glacier ice and act to mobilize and transport sediment and deposit it as various end members ranging from glacitectonically folded and faulted stratified material to texturally homogeneous diamicton the dominance of any one subglacial process varies both spatially and temporally giving rise to the possibility that a till or complex till sequence contains a superimposed signature of former transportation deposition at the ice bed interface we recommend that while glacial geologists and geomorphologists should be able to recognize the sedimentary imprints of various subglacial processes genetic fingerprinting of subglacial tills should be less process specific and till classification must reflect the range of products encompassed by the subglacial till production continuum glacial geologists can presently unequivocally identify a glacitectonite rock or sediment that has been deformed by subglacial shearing deformation but retains some of the structural characteristics of the parent material b subglacial traction till sediment deposited by a glacier sole either sliding over and or deforming its bed the sediment having been released directly from the ice by pressure melting and or liberated from the substrate and then disaggregated and completely or largely homogenised by shearing and support the theoretical case for c melt out till sediment released by the melting of stagnant or slowly moving debris rich glacier ice and directly deposited without subsequent transport or deformation because observations on contemporary glaciers reveal that their beds are most likely to be mosaics of deformation and sliding and warm based and cold based conditions the patterns of which change temporally and spatially it is extremely unlikely that subglacial till end members in the geological record will be anything but hybrids produced by the range of processes operative in the subglacial traction zone

rates of deformation uplift and landscape development associated with active folding in the waipara area of north canterbury new zealand analysis of the geometry and ages of faulted and tilted late quaternary fluvial terraces and their associated cover beds provide evidence of active folding at three locali ties in the waipara area of north canterbury new zealand terrace survey data the occurrence of the approximately 22 6 kyr old aokautere ash and examination of soil profiles indi cate that folding has continued into the late holocene but that the amounts and rates of deformation are locally variable rates of uplift in the waipara area are compared with those de rived from marine terraces preserved at the pacific coast east of the study area results indicate that rates of measurable de formation reach a maximum along the waipara range front where bedrock deformation is most intense and shortening rates of up to 5 57 0 69 100 kyr occur across the coastal ranges the average rate of shortening is 0 8 0 4 100 kyr which corresponds with an absolute shortening rate of 1 4 0 6 m kyr and represents only a small proportion of the pre dicted plate motion vector in this region uplift rates range from 0 1 83 m kyr for a late last glacial fluvial terrace and from 1 36 2 16 m kyr for three marine terraces fluvial and marine terrace uplift rates vary in accord with the geometries of the folds in bedrock and the spatial pattern of uplift di rectly reflects fold growth the structure contour pattern of folded surfaces provides a first approximation to the spatial pattern of uplift differential uplift due to folding accounts for up to approximately 55 75 of the total uplift and has produced folds with structural relief of about 1300 m i e amplitudes of 600 700 m these folds have formed over the

the tekapo glacier new zealand during the last glacial maximum an active temperate glacier influenced by intermittent surge activity abstract quaternary glaciations have created impressive landform assemblages that can be used to understand palaeo glacier extent character and behaviour and hence past global and local glacier forcings however in the southern hemisphere and especially in new zealand the quaternary glacial landform record is relatively poorly investigated with regard to glaciological properties in this study a 1 m digital elevation model dem was generated from airborne lidar data and supplemented with aerial imagery and field observations to analyse the exceptionally well preserved glacial geomorphology surrounding lake tekapo new zealand we describe a rich suite of last glacial maximum lgm and recessional ice marginal subglacial supraglacial glaciofluvial and glaciolacustrine landform assemblages these represent two landsystems comprising i fluted till surfaces with low relief push moraine ridges and ii crevasse squeeze ridges zig zag eskers and attenuated lineations the former landsystem records the behaviour of an active temperate glacier and the latter landsystem which is superimposed upon and inset within the former strongly suggests intermittent surge phases the two landsystem signatures indicate a sequential change in ice marginal dynamics during recession that was likely to have been partially non climatically driven overall we present the first evidence of surge type glacier behaviour in new zealand

multiple glacial advances in the rangitata valley south island new zealand imply roles for southern hemisphere westerlies and summer insolation in mis 3 glacial advances stratigraphic evidence and extensive optically stimulated luminescence osl geochronology from an 18 km long reach of the middle rangitata valley south island new zealand provide evidence for at least six distinct glacial advances during the last glacial cycle these include four well constrained marine oxygen isotope stage mis 3 and 2 advances at ca 38 ka ca 27 ka ca 21 ka and at 18 ka as well as less well constrained advances in mis 4 and or early mis 3 ice occupied a farther downvalley reach of the rangitata from 38 ka to after 18 ka indicating that near full glacial conditions persisted for most of the last 20 ka of the last glaciation though the glacier still fluctuated significantly as reflected by the numerous distinguishable advances global or regional cooling alone cannot explain the persistence of near maximum glacial conditions for this extended period nor can it explain the occurrence of the largest advances ca 32 ka instead we invoke the northward expansion of the westerlies during mis 3 as the cause for the early widespread glaciation wherein enhanced westerly flow under moderate cooling maximised glacial extents local insolation favoured extended mis 3 glaciation until ca 32 ka increasing summer insolation gradually reduced glacial extents after ca 28 ka

evidence for slow late glacial ice retreat in the upper rangitata valley south island new zealand abstract a suite of cosmogenic radionuclide ages taken from boulders on lateral and latero terminal moraines in the rangitata valley eastern south island new zealand demonstrates that relatively thick ice occupied valley reaches inland of the rangitata gorge until c 21 ka thereafter ice began to thin and by c 17 ka it had retreated 33 km up valley of the rangitata gorge to the butler brabazon downs a structurally created basin in the upper rangitata valley despite its magnitude this retreat represents a minor ice volume reduction from 21 ka to 17 ka and numerous lateral moraines preserved suggest a relatively gradual retreat over that 4 ka period in contrast to records from adjacent valleys there is no evidence for an ice collapse at c 18 ka we argue that the rangitata record constitutes a more direct record of glacial response to deglacial climate than other records where glacial dynamics were influenced by proglacial lake development such as the rakaia valley to the north and the major valleys in the mackenzie basin to the south west our data supports the concept of a gradual warming during the early deglaciation in the south island new zealand