tectonically induced diversion of the indus river west of the salt range pakistan abstract neogene and quaternary molasse deposition at the west end of the salt range in the foreland fold thrust belt of northern pakistan produced an unusually thick upper siwalik section near the indus river here siwalik sedimentary rocks coarsen upsection to 1500 m thick stacked channel conglomerate deposits with a distant provenance similar to deposits forming the bed load of the modern indus river the chisal algad an underfit stream separated from the indus river by a tectonically induced drainage divide contains a bed load clast assemblage resembling that of the indus river the indus channel migrated eastward abandoning the chisal algad and leaving high terrace deposits of indus gravels unconformably overlying tilted siwalik sedimentary rocks north of shakardarra uplift accompanying thrust faulting and transpression in the right slip kalabagh fault zone tilted a block measuring 15 km east west by 30 km north south the block has been incised by juvenile consequent drainage toward the indus river the indus river was diverted eastward in the last 0 5 ma and now occupies the lower part of the soan river system

mid holocene drylands a multi model analysis using paleoclimate modelling intercomparison project phase iii pmip3 simulations this study examines changes in aridity levels during the mid holocene approximately 6000 cal yr ago using multi model simulations from the paleoclimate modelling intercomparison project phase ii

a late pleistocene vegetation history from the australian semi arid zone abstract cuddie springs is an ephemeral lake in central northern new south wales australia the upper 3 m of sediment consist of lacustrine clays containing a late pleistocene sequence of extinct and extant fauna and in the upper 1 7 m an associated archaeological record changes observed in the pollen sequence include i a peak in charcoal values corresponding to a dramatic decline in casuarina woodland to chenopod shrubland at 2 5 m respresenting a climatic shift to more arid conditions ii chenopod shrubland moved into decline with the spread of grasslands around 1 7 m and the amelioration in climatic conditions persisted until approximately 28 000 bp a regime emerged which resulted in extended lake dry periods and peak aridity by approximately 19 000 bp and iii at 1 m depth around 19 000 bp a shift to peak arid conditions is observed with a return of chenopodiaceae and a decline in grasses the lake entered an ephemeral phase that has persisted until the present day the broad palaeoenvironmental framework of lake history climate and vegetation change spans the archaeological and faunal records from cuddie springs the direct association enables a closer examination of causation in faunal extinctions and human subsistence activities in the australian arid zone

variability of el nino southern oscillation activity at millennial timescales during the holocene epoch the variability of el nino southern oscillation enso during the holocene epoch in particular on millennial timescales is poorly understood palaeoclimate studies have documented enso variability for selected intervals in the holocene but most records are either too short or insufficiently resolved to investigate variability on millennial scales1 2 3 here we present a record of sedimentation in laguna pallcacocha southern ecuador which is strongly influenced by enso variability and covers the past 12 000 years continuously we find that changes on a timescale of 2 8 years which we attribute to warm enso events become more frequent over the holocene until about 1 200 years ago and then decline towards the present periods of relatively high and low enso activity alternating at a timescale of about 2 000 years are superimposed on this long term trend we attribute the long term trend to orbitally induced changes in insolation and suggest internal enso dynamics as a possible cause of the millennial variability however the millennial oscillation will need to be confirmed in other enso proxy records

a noachian source region for the black beauty meteorite and a source lithology for mars surface hydrated dust the martian surface is covered by a fine layer of oxidized dust responsible for its red color in the visible spectral range bibring et al 2006 morris et al 2006 in the near infrared the strongest spectral feature is located between 2 6 and 3 6 m and is ubiquitously observed on the planet jouglet et al 2007 milliken et al 2007 although this absorption has been studied for many decades its exact attribution and its geological and climatic implications remain debated we present new lines of evidence from laboratory experiments orbital and landed missions data and characterization of the unique martian meteorite nwa 7533 all converging toward the prominent role of hydroxylated ferric minerals martian breccias so called black beauty meteorite nwa7034 and its paired stones nwa7533 and nwa 7455 are unique pieces of the martian surface that display abundant evidence of aqueous alteration that occurred on their parent planet agee et al 2013 these dark stones are also unique in the fact that they arose from a near surface level in the noachian southern hemisphere humayun et al 2013 we used ir spectroscopy fe xanes and petrography to identify the mineral hosts of hydrogen in nwa 7533 and compare them with observations of the martian surface and results of laboratory experiments the spectrum of nwa 7533 does not show mafic mineral absorptions making its definite identification difficult through nir remote sensing mapping however its spectra are virtually consistent with a large fraction of the martian highlands abundant nwa 7034 7533 and paired samples lithologies might abound on mars and might play a role in the dust production mechanism

milankovitch forcing of fluctuations in the level of tropical lakes from 18 to 0 kyr bp an atmospheric general circulation model has been used to simulate the climates of january and july at 3 000 yr intervals from 15 kyr bp onwards the model simulates a strengthened monsoon circulation and increased precipitation in the northern hemisphere tropics culminating at 9 6 kyr bp the computed hydrological budgets were used to estimate the area of closed lakes between 8 9 and 26 6 n giving with minor exceptions results in good agreement with geological evidence

late miocene pleistocene evolution of india eurasia convergence partitioning between the bhutan himalaya and the shillong plateau new evidences from foreland basin deposits along the dungsam chu section eastern bhutan the shillong plateau is a unique basement cored uplift in the foreland of the eastern himalaya that accommodates part of the india eurasia convergence since the late miocene it was uplifted in the late pliocene to 1600 m potentially inducing regional climatic perturbations by orographically condensing part of the indian summer monsoon ism precipitations along its southern flank as such the eastern himalaya shillong plateau ism is suited to investigate effects of tectonics climate and erosion in a mountain range broken foreland system this study focuses on a 2200 m thick sedimentary section of the siwalik group strategically located in the lee of the shillong plateau along the dungsam chu at the front of the eastern bhutan himalaya we have performed magnetostratigraphy constrained by vitrinite reflectance and detrital apatite fission track dating combined with sedimentological and palynological analyses we show that 1 the section was deposited between 7 and 1 ma in a marginal marine deltaic transitioning into continental environment after 5 ma 2 depositional environments and paleoclimate were humid with no major change during the depositional period indicating that the orographic effect of the shillong plateau had an unexpected limited impact on the paleoclimate of the bhutanese foothills and 3 the diminution of the flexural subsidence in the basin and or of the detrital input from the range is attributable to a slowdown of the displacement rates along the main boundary thrust in eastern bhutan during the latest miocene pleistocene in response to increasing partitioning of the india eurasia convergence into the active faults bounding the shillong plateau

the influence of changing orbital parameters and surface boundary conditions on climate simulations for the past 18 000 years abstract general circulation model experiments at 3000 year intervals for the past 18 000 years were made to estimate the magnitude timing and pattern of the climatic response to prescribed changes of orbital parameters date of perihelion axial tilt eccentricity and glacial age lower boundary conditions ice sheets land albedo sea ice and sea surface temperature the experiments used the community climate model ccm of the national center for atmospheric research ncar the response of monsoon circulations and tropical precipitation to the orbitally produced solar radiation changes was much larger than the response to changes of glacial age boundary conditions the continental interior of eurasia was 2 4 k warmer in summer and summer monsoon precipitation of north africa south asia was increased by 10 20 between 12 000 and 6000 yr bp before present when perihelion occurred during northern summer rather than in winter as now and the earth s axial tilt was larger than now southern hemisphe

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

middle late miocene 10 ma formation of the main boundary thrust in the western himalaya three independent data sets from northwestern india and pakistan suggest initial displacement along 1000 km of the main boundary thrust prior to 10 ma at least 5 m y earlier than previously reported regionally extensive changes in the depositional characteristics and rates of the foreland basinfill between 11 and 9 5 ma are interpreted to reflect new hinterland loading due to the formation of the main boundary thrust sediment accumulation rates sandstone siltstone ratios and thickness and amalgamation of individual sandstone bodies all substantially increase after 11 ma in well dated stratigraphic sections from pakistan to nepal across the indo gangetic foreland basin in the himachal pradesh reentrant of northwestern india a newly discovered 8 7 ma conglomerate derived from the hanging wall of the main boundary thrust indicates that source area uplift and denudation must have occurred prior to 9 ma and probably prior to 10 ma assuming a gravelprogradationrateof3cm yr threeapatitefission trackages fromstructuresattheleadingedgeofthemainboundarythrustin the kohat region of northwest pakistan indicate that rapid cooling below 105 c1 2 m y earlier these data indicate that the main boundary thrust in the western himalaya formed synchronously along strike in the middle late miocene has a displacement rate of 10 mm yr and has a displacement history that is coeval with late displacement on the main central thrust

using anticyclonicity to determine the position of the southern hemisphere westerlies implications for the lgm 1 the possible meridional displacement of southern hemisphere westerlies under a different climate regime is examined by studying the characteristics of surface anticyclones an atmospheric general circulation model is used to simulate the climates of the present day and the last glacial maximum a vortex tracking scheme applied to the model data determines the characteristics of southern hemisphere anticyclones the statistics of anticyclone system density and system strength suggest the glacial epoch had surface westerlies that were displaced poleward over much of the hemisphere during both the summer and winter seasons the largest displacement occurred in the australian region during austral winter the anticyclones also reflect different atmospheric circulations in the past winter climate these are a weaker tropical circulation and more intense mid latitude eddy activity the simulation results are compared to paleo reconstructions and the consequences of potentially important ocean forcing are highlighted

strontium isotope variations in single ostracod valves from the gulf of carpentaria australia a palaeoenvironmental indicator the gulf of carpentaria is a shallow 70 m epicontinental sea which was partially and at times fully isolated from the ocean due to changing sea levels in the late quaternary in an attempt to elucidate the palaeoenvironment of this marine lacustrine system and hence constrain the rates of sea level changes high precision measurements 0 0036 of 87sr86sr ratios are reported for individual fossil ostracod valves these valves were extracted from two piston cores taken from the deepest part of the gulf of carpentaria single valves weighing 20 g 40 g and containing a total of 10 8 g to 2 10 8 g of sr have been analysed at the bottom of the main core in a depth interval equivalent to an age of 36 000 to 40 000 years valves from the ostracod species cyprideis have 87sr86sr ratios of from 0 70955 2 to 0 70967 2 sr 6 1 to 7 9 from 26 000 years to 22 000 years slightly higher but relatively constant 87sr86sr ratios of from 0 70998 2 to 0 71016 2 sr 12 2 to 14 9 are present the highest sr ratios are found in ostracod valves of 13 000 years age which have values from 0 71034 2 to 0 71039 2 sr 17 2 to 18 0 all these values are significantly greater than that of contemporary seawater and are indicative of continental sources with high 87sr86sr ratios significantly lower 87sr86sr ratios of from 0 70918 2 to 0 70961 2 sr from 0 8 to 7 0 are found in ostracods younger than 12 000 years and ratios identical to modern seawater 87sr86sr 0 70912 2 sr 0 0 are present in the upper 2 cm of core which is 5 000 years in age the variations in 87sr86sr ratios in ostracod valves from the carpentaria basin are consistent with a lacustrine environment from 36 000 years to 12 000 years followed by a transgressive marine sequence which commenced in the gulf of carpentaria 12 000 years ago this marine transgression was a result of sea level rising above the 53 m relative to present day sea level arafura sill sr isotope ratios identical to that of modern seawater were however only obtained when the 12 m torres strait sill was opened to the coral sea which occurred 8 000 to 7 000 years ago the marked decrease in sr isotopic ratios at the bottom of the core may be due to flow of the fly river from new guinea prior to its diversion into the coral sea or more probably a transitory input of marine water into the carpentaria basin during a relatively high sea level 40 000 years ago it is suggested that the highest asr values present 13 000 years ago reflect increased rainfall in the gulf area of northern australia which is attributed to a southwards migration of the monsoonal rainfall pattern at that time in contrast to some other chemical indicators of palaeoenvironments the asr results of this study provide definitive and unambiguous resolution of marine versus non marine environments and can thus be used to resolve with great accuracy transgressive regressive sequences

initiation of the australian summer monsoon 14 000 years ago abstract definitive evidence for the onset of monsoon moisture in northern australia following the arid phase of the last glacial maximum has been elusive in large part due to the lack of long continuous sediment records here we report new evidence from two separate drainage basins in the kimberley region of monsoonal northwestern australia at both sites radiocarbon ages on basal biogenic materials in flood deposits indicate stream flow as high or higher than maximum historic levels began about 14 cal ka bp these results suggest that the australian summer monsoon was fully active several millennia earlier than previously expected the early onset of the monsoon and the widespread evidence for diminished monsoon activity in the late holocene cannot be reconciled with primary forcing of the australian monsoon by changes in low latitude summer insolation over australia

ice age terrestrial carbon changes revisited n shackleton 1977 first proposed that changes in the marine 13 c record 13 c could be used to infer ice age changes in carbon storage on land the previously published best estimate from the marine record is equivalent to about 490 gt 0 32 13 c however adams et al 1990 utilized a pollen database to estimate a 1350 gt change in carbon storage which would cause a 13 c of about 0 90 the nearly trillion ton difference in estimates amounts to almost half of the total carbon stored on land to address the nature of this discrepancy i have reexamined the terrestrial carbon record based on a new pollen database compiled by r webb and the cooperative holocene mapping project cohmap group i estimate about 750 1050 gt glacial interglacial change in terrestrial carbon storage with the range reflecting uncertainties in carbon storage values for different biomes additional uncertainties apply to rainforest and wetland extent and presence of c4 plants which have a significantly different isotopic signature than c3 plants although some scenarios overlap a new estimate of carbon storage based on the oceanic 13 c record revised to 0 40 and 610 gt most estimates seem to fall outside the envelope of uncertainty in the marine record several possible explanations for this gap involve 1 a missing sink may be involved in land sea carbon exchange e g continental slopes 2 the geochemistry of the exchange process is not understood 3 carbon storage by biome may have changed under ice age boundary conditions or 4 the standard interpretation of whole ocean changes in the marine 13 c record requires reevaluation this latter conclusion receives some support from comparison of the 13 c records for 18 o stages 2 and 6 for the stage 6 glacial the 13 c changes are 50 60 larger than for the stage 2 glacial yet implications of increased aridity are not supported by longterm trends in atmospheric dust loading to summarize the above analysis implies that despite the uncertainties remaining in estimates of terrestrial carbon storage changes a case can be made that our understanding of the transfer process is incomplete and that the eventual explanation may require clarification of factors affecting the marine 13 c record

sorted clastic stripes lobes and associated gullies in high latitude craters on mars landforms indicative of very recent polycyclic ground ice thaw and liquid flows self organised patterns of stone stripes polygons circles and clastic solifluction lobes form by the sorting of clasts from fine grained sediments in freeze thaw cycles we present new high resolution imaging science experiment hirise images of mars which demonstrate that the slopes of high latitude craters including heimdal crater just 25 km east of the phoenix landing site are patterned by all of these landforms the order of magnitude improvement in imaging data resolution afforded by hirise over previous datasets allows not only the reliable identification of these periglacial landforms but also shows that high latitude fluviatile gullies both pre and post date periglacial patterned ground in several high latitude settings on mars because thaw is inherent to the sorting processes that create these periglacial landforms and from the association of this landform assemblage with fluviatile gullies we infer the action of liquid water in a fluvio periglacial context we conclude that these observations are evidence of the protracted widespread action of thaw liquids on and within the martian regolith moreover the size frequency statistics of superposed impact craters demonstrate that this freeze thaw environment is at least in heimdal crater less than a few million years old although the current martian climate does not favour prolonged thaw of water ice observations of possible liquid droplets on the strut of the phoenix lander may imply significant freezing point depression of liquids sourced in the regolith probably driven by the presence of perchlorates in the soil because perchlorates have eutectic temperatures below 240 k and can remain liquid at temperatures far below the freezing point of water we speculate that freeze thaw involving perchlorate brines provides an alternative low temperature hypothesis to the freeze thaw of more pure water ice and might drive significant geomorphological work in some areas of mars considering the proximity of heimdal crater to the phoenix landing site the presence of such hydrated minerals might therefore explain the landforms described here if this is the case then the geographical distribution of martian freeze thaw landforms might reflect relatively high temperatures but still below 273 k and the locally elevated concentration of salts in the regolith c 2010 elsevier inc all rights reserved

abrupt post glacial climate events in west asia and north africa monsoon domains regions beyond the present or past penetration of the indian and african monsoons have experienced several large and abrupt climatic fluctuations over the past 13 14c kyr pollen and lake records from west asia western tibet and rajasthan east africa ethiopia and west africa western sahara sahel and subequatorial africa were selected on the basis of chronological control sensitivity of both site and environmental indicators to climate change the continuity of the record and interdisciplinary control of the palaeoclimatic interpretation conditions wetter than those of today prevailed during the early mid holocene period but major dry spells are recorded at all sites during the intervals 11 0 9 5 kyr bp 8 7 kyr bp and 3 4 kyr bp several records also suggest dry events of minor amplitude around 6 kyr bp potential boundary forcings of insolation and sea surface and tropical land surface conditions are discussed the solar radiation accounts for the general envelop of the post glacial monsoon fluctuations but explains neither the timing nor the amplitude of the short term changes in spite of apparent covariation between fluctuations in sea surface conditions in the north atlantic and the monsoon record no direct mechanism could be found relating the intensity of the oceanic thermohaline conveyor belt to the monsoon strength changes in tropical land surface conditions soil moisture negative feedback and changes in ch4 production from wetlands provide a more satisfactory hypothesis for explaining abrupt reversal events

mars exploration program 2007 phoenix landing site selection and characteristics 1 to ensure a successful touchdown and subsequent surface operations the mars exploration program 2007 phoenix lander must land within 65 to 72 north latitude at an elevation less than 3 5 km the landing site must have relatively low wind velocities and rock and slope distributions similar to or more benign than those found at the viking lander 2 site also the site must have a soil cover of at least several centimeters over ice or icy soil to meet science objectives of evaluating the environmental and habitability implications of past and current near polar environments the most challenging aspects of site selection were the extensive rock fields associated with crater rims and ejecta deposits and the centers of polygons associated with patterned ground an extensive acquisition campaign of odyssey thermal emission imaging spectrometer predawn thermal ir images together with 0 31 m pixel mars reconnaissance orbiter high resolution imaging science experiment images was implemented to find regions with acceptable rock populations and to support monte carlo landing simulations the chosen site is located at 68 16 north latitude 233 35 east longitude areocentric within a 50 km wide n s by 300 km long e w valley of relatively rock free plains surfaces within the eastern portion of the valley are differentially eroded ejecta deposits from the relatively recent 10 km wide heimdall crater and have fewer rocks than plains on the western portion of the valley all surfaces exhibit polygonal ground which is associated with fracture of icy soils and are predicted to have only several centimeters of poorly sorted basaltic sand and dust over icy soil deposits

insolation forcing of the australian monsoon as controls of pleistocene mega lake events 1 during the last c 300 000 years mega lakes with areas an order of magnitude greater than those of today occurred in the monsoon region of northern australia the results of an atmosphere global circulation model agcm sensitivity experiment show that the repeated occurrence of mega lake phases during the pleistocene and the strong monsoon flow that this implies can be related to milankovitch insolation forcing the agcm experiment is centred on the southern hemisphere low latitude summer insolation high of 115 000 years ago the details of the results indicate a strong response of the australian monsoon to the higher insolation at that time with a longer monsoon season increased precipitation and higher resultant runoff than at present

geological evidence against large scale pre holocene offsets along the karakoram fault implications for the limited extrusion of the tibetan plateau two end member models proposed to accommodate the convergence between india and asia north of the himalaya are 1 homogeneous crustal thickening of the tibetan plateau and 2 continental escape or extrusion of tibet and southeast asia away from the indenting indian plate foremost among the arguments supporting the latter would be large scale 1000 km offsets and high present day slip rates along the major strike slip faults bounding the postulated extruding crust notably the altyn tagh fault along the northern margin of tibet and the karakoram fault along the sw margin satellite photographic interpretation and field mapping in the karakoram mountains in pakistan the nubra siachen area of north ladakh and the pamirs in xinjiang show that although the karakoram fault is extremely active today geological offsets along the right lateral fault are probably less than 120 km the 21 0 5 ma baltoro monzogranite leucogranite batholith has been rotated clockwise about a vertical axis 35 40 into nw se alignment parallel with the karakoram fault east of the siachen glacier with a maximum offset of 90 km across the fault the bangong shyok suture zone similarly has a dextral offset of 85 km the course of the indus river which was antecedent to the rise of the ladakh karakoram and himalayan ranges has been offset dextrally by 120 km south of pangong lake if present day slip rates approximately 32 mm yr avouac and tapponnier 1993 are correct only 4 ma are required to obtain a 120 km offset there is no geological evidence for any larger scale pre holocene offsets and it is suggested that the karakoram fault cannot have accommodated major eastward lateral motion of tibetan crust the fault has also exerted little or no influence on surface topographic uplift cutting obliquely across the highest peaks of the karakoram dextral motion along the central part of the karakoram fault has been transferred in the north to the rangkul murghab and karasu transpressional faults in the central pamir north of tashkurgan the karakoram fault shows mainly normal motion around the kongur and mustagh ata gneiss domes metamorphic core complexes and the extensional muji graben minor dextral displacement has occurred along the shiquanhe fault but this motion cannot be linked to the jiale fault of east tibet the southern end of the karakoram fault merges with the indus yarlung suture zone near mount kailas and does not cut across the himalaya the lack of large scale geological offsets along the karakoram fault together with its very recent initiation 5 or 4 ma suggests that it is related to the pliocene quaternary northward indentation of the pamir and not to any long term extrusion of tibetan crust following the indian collision

ensemble simulations of asian australian monsoon variability by 11 agcms ensemble simulations of asian australian monsoon a am anomalies were evaluated in 11 atmospheric general circulation models for the unprecedented el nino period of september 1996 august 1998 the models simulations of anomalous asian summer rainfall patterns in the a am region 308s 308n 408 1608e are considerably poorer than in the el nino region this is mainly due to a lack of skill over southeast asia and the western north pacific 58 308n 808 1508e which is a striking characteristic of all the models the models deficiencies result from failing to simulate correctly the relationship between the local summer rainfall and the sst anomalies over the philippine sea the south china sea and the bay of bengal the observed rainfall anomalies are negatively correlated with sst anomalies whereas in nearly all models the rainfall anomalies are positively correlated with sst anomalies while the models physical parameterizations have large uncer tainties this problem is primarily attributed to the experimental design in which the atmosphere is forced to respond passively to the specified ssts while in nature the ssts result in part from the atmospheric forcing regional monsoon dynamic indices are calculated for the indian the western north pacific and the australian monsoons respectively most models can realistically reproduce the western north pacific and australian mon soon yet fail with the indian monsoon to see whether this is generally the case a suite of five seoul national university model runs with the same observed lower boundary forcing and differing only in their initial conditions was examined for the period 1950 98 the skill in the 49 yr ensemble simulations of the indian monsoon is significantly higher than the skill for the period 1996 98 in other words for the unprecedented 1997 98 el nino period the models under study experience unusual difficulties in simulating the indian monsoon circulation anomalies moreover the observed webster yang index shows a decreasing trend over the last 50 yr a trend missed by the models ensemble simulations

coordinated analyses of orbital and spirit rover data to characterize surface materials on the cratered plains of gusev crater mars 1 comparison of the mars exploration rover spirit s pancam 0 4 to 1 0 m and mars express observatoire pour la mineralogie l eau les glaces et l activite omega 0 4 to 2 5 m spectral reflectance data over spirit s traverses shows that gusev cratered plains are dominated by nanophase ferric oxide rich dust covering weakly altered basaltic sands this interpretation is also consistent with both observations from omega data covering plains beyond the traverse region and interpretations of data from the other payload instruments on the spirit rover omega observations of relatively low albedo regions where dust has presumably been stripped by dust devils show negative spectral reflectance slopes from 1 5 to 2 5 m and moderately masked spectral features which are indicative of olivine or pyroxene high albedo regions north and south of the spirit landing site have flat spectral reflectance slopes and few spectral features although all spectra have a nanophase ferric oxide absorption edge between 0 4 and 0 75 m comparison of themis derived thermal inertia values with omega derived spectral parameters shows that although the dust cover can be optically thick 0 4 to 2 5 m wavelength region in some areas it is not thick enough 1 cm to mask the thermal inertia of the underlying substrate for areas included in this study

thrusting and gravel progradation in foreland basins a test of post thrusting gravel dispersal the use of gravels as syntectonic indicators of thrusting has recently been questioned by foreland basin models that assign gravels to a post thrusting interval of progradation except in very proximal areas on the basis of precise temporal control provided by magnetostratigraphically dated sections the history of gravel progradation after a major thrusting and uplift event in the northwestern himalaya is shown to be a virtually syntectonic phenomenon despite considerable crustal subsidence driven by a thick skinned thrust gravels prograded approximately 70 km during a 1 5 m y long thrusting event by 3 m y after the start of thrusting gravels extended more than 110 km into the basin although delayed gravel progradation appears appropriate for many rocky mountain foreland basins it is clearly not valid for the himalaya the authors attribute the difference in depositional response between these basins to difference in the quantity of sediment supplied to them sediment starved vs overfilled the availability of resistates in the source area and the size of the antecedent drainage

changes in the atmospheric ch4 gradient between greenland and antarctica during the last glacial and the transition to the holocene significant variations in the interpolar difference of atmospheric ch4 concentration over the holocene period were observed by chappellaz et al 1997 here we extend this study to the last glacial and the transition to the holocene we observe a gradient of 3 4 parts per billion by volume ppbv during the last glacial maximum it increases to 26 10 ppbv during the bolling allerod and remains at 26 9 ppbv during the younger dryas cold period on average we find an interpolar difference of 14 4 ppbv during the cold phases and of 37 10 ppbv during the warm periods of the last glacial with a three box model we derive from the measured gradients the contributions of methane from the tropics and the mid to high latitudes of the northern hemisphere the tropics have been the largest source in all glacial epochs the contribution by the northern latitudes have been very small during the last glacial maximum but surprisingly large during the earlier part of the glacial epoch the model result suggests completely unexpected that the higher atmospheric ch4 concentration during the warm dansgaard oeschger events are caused by a higher source strength of the northern latitudes and not of the tropics

palynology of eastern indonesian marine piston cores a late quaternary vegetational and climatic record for australasia abstract pollen analyses of late quaternary sediments from nine marine piston cores reveal a continuous vegetation and environmental record for eastern indonesia and northern australia on the island of halmahera a montane oak forest largely replaced the tropical lowland vegetation during the last glacial period while fern cover was strongly reduced during its maximum 18 000 yr b p climate was cooler and slightly drier than today around 10 000 yr b p mangrove vegetation expanded following the rising sea level in our western new guinea record at 14 000 yr b p climate grew warmer and slightly wetter until it stabilised around 10 000 yr b p at that time the mid to upper montane forests expanded to their full altitudinal range and fern cover increased while montane oak forest grassland and woodland areas had contracted in our marine pollen records during the last glacial the climate of northern australia was distinctly drier than today grassland vegetation with sedges increased considerably at 38 000 and 24 000 yr b p replacing eucalypt forest and culminating in a maximum grassland cover at the height of the last glaciation 18 000 yr b p the rapid sea level rise allowed the expansion of mangrove forests and salt bush marshes which had become established on the large tidal flats of the drowning sahul shelf around 12 000 yr b p one piston core g6 4 extends to 300 000 yr b p and shows that glacial periods are characterized by high pollen concentrations in marine sediments recording expanding grassland vegetation during interglacial woodland and fern cover increased while pollen concentrations in the sediments were low after 190 000 yr b p a more open vegetation suggests that conditions were in general much more arid than before repeated mangrove vegetation expansions suggest major rises in sea level at around 244 000 220 000 and 130 000 yr b p

late quaternary landscapes in central australia sedimentary history and palaeoecology of puritjarra rock shelter puritjarra rock shelter provides a long record of late quaternary vegetation in the australian arid zone analysis of the sedimentary history of this rock shelter is combined with reanalysis of charcoal and phytolith records to provide a first order picture of changing landscapes in western central australia these show a landscape responding to increasing aridity from 45 ka with deflation of clay rich red palaeosols 45 ka and sharp declines in grassland and other vegetation at 40 36 ka and at the beginning of the last glacial maximum lgm 24 ka vegetation in the catchment of the rock shelter recovered after 15 ka with expansion of both acacia woodland and spinifex grasslands registering stronger summer rainfall in the interior of the continent by 8 3 ka re vegetation of local palaeosols and dunes had choked off sediment supply to the rock shelter and the character of the sediments changed abruptly poaceae values peaked at 5 8 ka suggesting the early mid holocene climatic optimum in central australia is bracketed between 8 3 and 5 8 ka local vegetation was disrupted in the late holocene with a sharp decline in poaceae at 3 8 ka coinciding with an abrupt intensification of enso local grasslands recovered over the next two millennia and by 1 5 ka the modern vegetation appears to have become established copyright 2009 john wiley sons ltd

opaline silica in young deposits on mars high spatial and spectral resolution reflectance data acquired by the mars reconnaissance orbiter compact reconnaissance imaging spectrometer for mars crism instrument reveal the presence of h 2o and sioh bearing phases on the martian surface the spectra are most consistent with opaline silica and glass altered to various degrees confirming predictions based on geochernicall experiments and models that amorphous silica should be a common weathering product of the basaltic martian crust these materials are associated with hydrated fe sulfates including h 3o bearing jarosite and are found in finely stratified deposits exposed on the floor of and on the plains surrounding the valles marineris canyon system stratigraphic relationships place the formation age of these deposits in the late hesperian or possibly the amazonian implying that aqueous alteration continued to be an important and regionally extensive process on mars during that time

global monsoons in the mid holocene and oceanic feedback the response of the six major summer monsoon systems the north american monsoon the northern africa monsoon the asia monsoon the northern australasian monsoon the south america monsoon and the southern africa monsoon to mid holocene orbital forcing has been investigated using a coupled ocean atmosphere general circulation model foam with the focus on the distinct roles of the direct insolation forcing and oceanic feedback the simulation result is also found to compare well with the ncar csm the direct effects of the change in insolation produce an enhancement of the northern hemisphere monsoons and a reduction of the southern hemisphere monsoons ocean feedbacks produce a further enhancement of the northern africa monsoon and the north american monsoon however ocean feedbacks appear to weaken the asia monsoon although the overall effect direct insolation forcing plus ocean feedback remains a strengthened monsoon the impact of ocean feedbacks on the south american and southern african monsoons is relatively small and therefore these regions especially the south america experienced a reduced monsoon regime compared to present however there is a strong ocean feedback on the northern australian monsoon that negates the direct effects of orbital changes and results in a strengthening of austral summer monsoon precipitation in this region a new synthesis is made for mid holocene paleoenvironmental records and is compared with the model simulations overall model simulations produce changes in regional climates that are generally consistent with paleoenvironmental observations

early onset and tropical forcing of 100 000 year pleistocene glacial cycles between 1 5 and 0 6 myr ago the period of the earth s glacial cycles changed from 41 kyr the period of the earth s obliquity cycles to 100 kyr the period of the earth s orbital eccentricity1 2 which has a much smaller effect on global insolation the timing of this transition and its causes pose one of the most perplexing problems in palaeoclimate research3 here we use complex demodulation to examine the phase evolution of precession and semiprecession cycles the latter of which are phase coupled to both precession and eccentricity in the tropical and extra tropical atlantic ocean we find that about 1 5 myr ago tropical semiprecession cycles with periods of about 11 5 kyr started to propagate to higher latitudes coincident with a growing amplitude envelope of the 100 kyr cycles evidence from numerical models suggests that cycles of about 10 kyr in length may be required to explain the high amplitude of the 100 kyr cycles4 combining our results with consideration of a modern analogue we conclude that increased heat flow across the equator or from the tropics to higher latitudes around 1 5 myr ago strengthened the semiprecession cycle in the northern hemisphere and triggered the transition to sustained 100 kyr glacial cycles

sensitivity of the australian summer monsoon to tilt and precession forcing abstract the response of the australian summer monsoon to orbital forcing is studied using a coupled general circulation model gcm with the focus on the relative roles of tilt and precession on the forcing of the northern australian summer monsoon it was found that unlike the northern hemisphere monsoons which are dominated by precession forcing the australian monsoon can be enhanced significantly not only by precession forcing but also by tilt forcing coupled to oceanic feedback the new insights obtained from a series of experiments with differing tilt precession configurations allow an interpretation of the australian late quaternary monsoon record in which insolation forcing plays a significant role

orbital controls on the el nino southern oscillation and the tropical climate the global synchroneity of glacial interglacial events is one of the major problems in understanding the link between milankovitch forcing and the climate of the late quaternary in this study we isolate a part of the climate system the tropical pacific and test its sensitivity to changes in solar forcing associated with changes in the earth s orbital parameters we use a simplified coupled ocean atmosphere model that is run for the past 150 000 years and forced with milankovitch changes in the solar insolation this system responds primarily to the precessional cycle in solar forcing and is capable of generating a mean response to the changes in the seasonal distribution of solar radiation even while the annual mean insolation is roughly constant the mean response to the precessional forcing is due to an interaction between an altered seasonal cycle and the el nifio southern oscillation enso changes in the enso behavior result in a mean tropical climate change the hypothesis is advanced that such a change in the tropical climate can generate a globally synchronous climate response to milankovitch forcing

geomorphologic and mineralogic characterization of the northern plains of mars at the phoenix mission candidate landing sites 1 a suite of remote sensing data is used to evaluate both geomorphology and mineralogy of the candidate landing sites for the 2007 phoenix mission three candidate landing site boxes are situated in the northern plains of mars on the distal flank of alba patera in the region from 67 n to 72 n and from 230 e to 260 e geomorphology is mapped at subkilometer spatial scales using thermal emission imaging system themis visible and mars orbiter laser altimeter mola topographic data supplemented by images from the high resolution imaging science experiment hirise and context imager ctx mineralogy and spectral properties are examined using compact reconnaissance imaging spectrometer for mars crism visible and near infrared multispectral mapping and targeted hyperspectral data at 200 and 20 m pixel respectively geomorphic mapping supports the idea that terrains along the boundary between the amazonian scandia region and vastitas borealis marginal geologic units have undergone extensive modification intercrater plains are disrupted to form mesas and interlocking blocks while irregular depressions and knobby terrain are consistent with erosion subsidence and local deposition despite the varied morphology the present day surface is nearly homogeneous with spectral signatures dominated by nanophase iron oxides and basaltic sand and rocks similar to that of the gusev crater plains at the mars exploration rover mer landing site the compilation of geomorphic and spectral information for the candidate phoenix landing sites provides a framework for the mission s in situ observations to be extrapolated to the northern plains as a whole

river systems and their sediment flux indo gangetic plains northern bihar india river systems of part of the himalayan foreland northern bihar plains india are described in terms of their channel morphology hydrology and suspended sediment characteristics a simple classification of the river systems based mainly on the source area characteristics is proposed i mountain fed ii foothills fed iii plains fed and iv mixed fed rivers distinct differences are noted between these classes of river systems most rivers show evidence of channel movement mainly by avulsion but cut offs also occur locally the mountain fed rivers are characterized by very high discharge and low suspended sediment concentration and the plains fed rivers have relatively low discharge and high suspended sediment concentration the foothill fed rivers have moderate values of discharge and suspended sediment concentration the mountain fed rivers have built megafans of large extent whereas the foothills fed and plains fed rivers have formed muddy interfan areas semi quantitative estimates of water and sediment flux suggest that about 99 9 of the mass transfer into the plains is water with the remaining 0 1 being sediment and that 10 s of the latter 0 01 of the total is retained in the basin the remainder being transferred to the bengal fan

exotic conglomerates of the neogene siwalik succession and their implications for the tectonic and topographic evolution of the western himalaya

organic petrology of subbituminous carbonaceous shale samples from chalāw kabul province afghanistan considerations for paleoenvironment and energy resource potential abstract neogene subbituminous carbonaceous shale deposits from chal w afghanistan were investigated through organic petrology techniques and standard coal analyses to determine paleoenvironment and potential for resource utilization the chal w deposit approximately 30 km southeast of kabul currently is exploited for brick making and domestic heating and cooking three multiple bench channel samples of the mined bed at chal w were collected and evaluated the presence of significant huminite ranging from 0 2 to 59 0 vol mineral inclusive basis is suggestive of a terrestrial lignin rich precursor plant material measured reflectance values of 0 38 0 55 indicate subbituminous rank this rank suggests burial depths of approximately 1500 m and maximum temperatures of approximately 50 c structured liptinite macerals generally are absent except for some fluorescing morphologies interpreted to be poorly preserved root cork suberinite sponge spicule bioliths including gemmoscleres and megascleres are common these petrographic observations in addition to high mineral matter content 33 to 95 vol medium to high sulfur content 2 1 11 5 wt dry basis db and the presence of common gastropod shell fragments and an aragonite needle chalk bed are consistent with but not directly indicative of a marginal marine or estuarine mangrove depositional environment however additional data are necessary to confirm this hypothesis and deposition in a freshwater environment cannot be ruled out at this time commercial scale development and utilization of the chal w deposit as a thermal fuel resource may be possible using a fluidized bed combustion system which could accept the low quality mine product currently produced samples examined herein contain high ash yield 45 90 wt db high total moisture content 17 39 wt low calorific value 980 6860 btu lb m mmf and have poor agglomerating properties fsi 0 consistent with fuels utilized in fluidized bed combustors however delineation of the extent of the deposit through field investigation will be necessary to make a quantified resource estimate for mine planning

time slice analysis of the australian summer monsoon during the late quaternary using the fast ocean atmosphere model we use the fast ocean atmosphere model foam to investigate the variation in the australian summer monsoon over the last 55 000 years a synthesis of palaeoenvironmental observations is used to constrain the model for six time slices 55 35 21 11 6 and 0 ka both inter hemispheric forcing and the seasonal timing of local insolation changes play key and interacting roles on the evolution and intensity of the monsoon during the onset to the monsoon a heat low develops to the west of australia over the indian ocean in all time slices but with varying strengths divergent outflow from asia converges with the cyclonic flow to bring increased rainfall to northern australia and the maritime continent the relative importance of a low pressure pull and the high pressure push varies according to the strength of the pressure anomalies only in the middle holocene is the low pressure pull the dominant forcing mechanism at 21 ka the climate shift to colder mean temperatures determines the large scale dynamics of the monsoon the general picture that emerges from these results is consistent with available palaeodata but highlights the importance of a broad regional perspective to ascribe the driving mechanisms at different times copyright 2006 john wiley sons ltd

spectral variability of the martian high latitude surfaces 1 we report the surface distributions of some minerals in the high latitude 50 regions of mars using the omega mex observations in the near infrared wavelength domains 1 2 5 m mafic minerals pyroxene and olivine are observed in the low albedo terrains the identification of these minerals is consistent with the presence of volcanic features identified by geologic mappings water bearing minerals identified on the basis of the 1 9 m band cover the surfaces of latitudes larger than 60 the presence of this hydration is likely the result of diffusive exchange of water between the sub surface ice the pore space of the regolith and the atmosphere rather than chemically bound water resulting from hydrous alteration during the formation of the minerals these observations will allow for comprehensive coordinated analyses of data from the orbital and phoenix platforms

human environment interactions in australian drylands exploratory time series analysis of archaeological records exploratory time series analysis of radiocarbon data from archaeological contexts is used to reconstruct the population history of arid australia allowing this to be read in concert with records of climatic variability over the last 20 000 years probability distribution plots of 971 radiocarbon ages from 286 sites in five dryland regions the arid west coast pilbara and murchison nullarbor arid interior and the southeastern arid zone provide a proxy record of prehistoric population fluctuations in these areas there is regional variation but the radiocarbon density plots suggest a step wise pattern of population growth and expansion with significant thresholds at 19 8 and 1 5 cal kyr bp within this the plots suggest a saw tooth pattern of rapid population growth and decline on a 1 3 kyr frequency with a marked collapse of dryland hunter gatherer populations around 3 2 5 cal kyr bp affecting most regions comparison with climate data shows broad correlations with past temperature and rainfall

chemical weathering and diagenesis of a cold desert soil from wright valley antarctica an analog of martian weathering processes weathering diagenesis and chemical alteration of a soil profile from the dry valleys of antarctica have been studied as an analog to soil development within the martian regolith soil samples from a one meter deep soil pit on prospect mesa wright valley have been examined for their major element concentrations water soluble cations and anions carbon sulfur and water concentrations and related petrographic characteristics of weathering in a cold dry environment petrographic study of the soil samples indicates that most silicate mineral and lithic fragments exhibit some degree of alteration chemical alteration occurs in samples both from above and from within the permanently frozen zone concentrations of water soluble cations na k ca2 and anions cl so42 no3 decrease significantly from the surface to the permanently frozen zone suggesting major movement of water soluble species enrichments in secondary mineral abundances correlate with the water soluble ion concentrations formation of zeolites is observed throughout the soil column and may be potential reservoirs for volatile storage within the regolith from the detailed study of the dry valley soils an idealized soil profile for the regolith has been developed and is suggested as applicable to other planetary surfaces especially the martian nearsurface environment the soil profile consists of four zones aeolian salt active and permanently frozen

biomass burning and oceanic primary production estimates in the sulu sea area over the last 380 kyr and the east asian monsoon dynamics abstract coccolithophorid assemblages and micro charcoal content were analysed in giant piston core md97 2141 recovered in the sulu sea philippines these proxies help to reconstruct respectively the dynamics of the oceanic primary production pp and biomass burning in that area pp in the sulu sea intensifies during the east asian winter monsoon eawm and therefore pp constitutes a proxy for eawm dynamics most of the precipitation in the sulu sea region occurs during the east asian summer monsoon easm because the intensity of biomass burning is related to dryness of the surrounding area the sedimentary micro charcoal content can be used as an inverse proxy for easm intensity our results show that the eawm intensifies during glacial times in agreement with previous studies precessional forcing appears to act directly on eawn because of the early response of pp in that frequency band the micro charcoal record exhibits complex dynamics which we attribute to the competing influence of the long term el nino southern oscillation enso like forcing and the glacial interglacial cycle on easm these influences create an unusual frequency spectrum with power around 30 kyr and 19 kyr attributed to the non linear response to the 100 kyr cycle glacial and the 23 kyr enso cycle a factor of two increase in the amplitude of the micro charcoal variability between 51 and 10 ka bp could correspond to homo sapiens biomass burning in the style of the fire stick farming of the australian aborigines we also find on precession cycles an opposite phase between easm and eawm records and an advance of 18 o and 18 o respectively by 2000 yr

mineralogy of the phoenix landing site from omega observations and how that relates to in situ phoenix measurements abstract we present an analysis comparing observations acquired by the mars express observatoire pour la mineralogie l eau les glaces et l activite omega and phoenix lander measurements analysis of omega data provides evidence for hydrous and ferric phases at the phoenix landing site and the surrounding regions the 3 m hydration band deepens with increasing latitude along with the appearance and deepening of a 1 9 m h2o band as latitude increases 60 polewards a water content of 10 11 is derived from the omega data for the optical surface at the phoenix landing site compared to 1 2 derived for subsurface soil by phoenix lander measurements the hydration of these regions is best explained by surface adsorbed water onto soil grains no evidence for carbonate or perchlorate bearing phases is evident from omega data consistent with the relatively small abundances of these phases detected by phoenix the identification of spectral features consistent with hydrated phases possibly zeolites from omega data covering regions outside the landing site and the ubiquitous ferric absorption edge suggest that chemical weathering may play a role in the arctic soils

the history and variability of the east asian paleomonsoon climate abstract changes in the east asian paleomonsoon reflect interactions between the global atmosphere ocean land and ice systems and are also an expression of their combined effect within the boundary conditions imposed by the east asian continent and solar radiation the history of the east asian monsoon is an alternation between dominance by the dry cold winter and warm humid summer monsoons high resolution eolian sequences preserved in the chinese loess plateau reveal that the east asian monsoon may have commenced at least 7 2 ma ago they also provide evidence indicating that the pulsed uplift of the tibetan plateau at about 3 4 and 7 2 ma may have played an important role in inducing climate change the palaeoclimatic records of the last glacial cycle show high frequency variability on time scales of 1000 year or even shorter and instability of the east asian paleomonsoon system the high frequency variability could be due to a non linear response to orbital forcing or a result of the coupling processes between different components of the global system cold air activity in northern high latitudes the trans equatorial air streams from the southern hemisphere and possibly enso may have played an important role in east asian monsoon variability the synchroneity of all the palaeoclimatic events along the polar equator polar pep transect is still an open question correlation of limited palaeoclimatic records for the last 30 kyr obtained from east asia and australia suggests that the trans equatorial air streams driven by the monsoon and trade winds may have had an influence on opposite hemispheres

late quaternary milankovitch scale climatic change and variability and its impact on monsoonal australasia four pollen and charcoal records derived from marine cores around the northern perimeter of australia are examined to provide a regional picture of patterns causes and impacts of climate change over the last 100 300 ka the availability of radiocarbon dates and oxygen isotope records for the cores provides primary chronological control spectral analysis of components of these records demonstrates an overall importance of milankovitch frequencies with clear glacial interglacial cyclicity dominated by variation in precipitation in addition a number of pollen taxa as well as charcoal particles exhibit a 30 ka frequency that is considered from its relationship with biomass burning and with results of past modelling to reflect changes in the intensity of el nino southern oscillation enso variability pollen components of all records show a decline frequently stepwise in more fire sensitive vegetation and its replacement with more fire tolerant vegetation there is some evidence that this trend is linked to an onset or general increase in enso activity and perhaps also to variation in monsoon activity dating from about 300 ka bp that was caused by changes to oceanic circulation within the indonesian region the trend may have accelerated within the last 45 ka due to burning by indigenous people c 2003 elsevier b v all rights reserved

how well can we simulate past climates evaluating the models using global palaeoenvironmental datasets abstract global syntheses of palaeoenvironmental data are required to test climate models under conditions different from the present data sets for this purpose contain data from spatially extensive networks of sites the data are either directly comparable to model output or readily interpretable in terms of modelled climate variables data sets must contain sufficient documentation to distinguish between raw primary and interpreted secondary tertiary data to evaluate the assumptions involved in interpretation of the data to exercise quality control and to select data appropriate for specific goals four data bases for the late quaternary documenting changes in lake levels since 30 14 c kyr bp the global lake status data base vegetation distribution at 18 14 c kyr and 6 14 c kyr bp biome 6000 aeolian accumulation rates during the last glacial interglacial cycle dirtmap and tropical terrestrial climates at the last glacial maximum the lgm tropical terrestrial data synthesis are summarised each has been used to evaluate simulations of last glacial maximum lgm 21 calendar kyr bp and or mid holocene 6 cal kyr bp environments comparisons have demonstrated that changes in radiative forcing and orography due to orbital and ice sheet variations explain the first order broad scale in space and time features of global climate change since the lgm however atmospheric models forced by 6 cal kyr bp orbital changes with unchanged surface conditions fail to capture quantitative aspects of the observed climate including the greatly increased magnitude and northward shift of the african monsoon during the early to mid holocene similarly comparisons with palaeoenvironmental datasets show that atmospheric models have underestimated the magnitude of cooling and drying of much of the land surface at the lgm the inclusion of feedbacks due to changes in ocean and land surface conditions at both times and atmospheric dust loading at the lgm appears to be required in order to produce a better simulation of these past climates the development of earth system models incorporating the dynamic interactions among ocean atmosphere and vegetation is therefore mandated by quaternary science results as well as climatological principles for greatest scientific benefit this development must be paralleled by continued advances in palaeodata analysis and synthesis which in turn will help to define questions that call for new focused data collection efforts

north atlantic forcing of millennial scale indo australian monsoon dynamics during the last glacial period recent studies of the last glacial period indo australian summer monsoon iasm have revealed links to both northern and southern hemisphere high latitude climate as well as to regional ocean conditions particular interest has been paid to the monsoon response to heinrich events with variability explained by meridional shifts in positioning of the intertropical convergence zone itcz but this model has not been adequately tested in addition the shorter lived dansgaard oeschger d o events have not been detected beyond d o 1 the bolling allerod in land based records from the indo pacific despite their prominent expression in stalagmites from southern asia raising questions about the sensitivity of the iasm to these events here we present a southern hemisphere stalagmite oxygen isotopic time series from ball gown cave bgc tropical northern australia located on the margins of the modern austral summer itcz that spans 40e31 and 27e8 ka elevated iasm rainfall coincides with heinrich stadials and the younger dryas while decreased rainfall characterizes d o interstadials a response that is antiphased with sites spanning the indo pacific warm pool and with chinese records of the east asian summer monsoon the bgc time series thus reveals a precipitation dipole consistent with a southward northward migration of the itcz during periods of high northern latitude cooling warming as the primary driver of millennial scale iasm variability during the last glacial period our record indicates a strengthening of the iasm after the younger dryas period likely as a result of rising sea level and sea surface temperatures breaking the link with the high latitudes

elemental delta c 13 at allen s cave nullarbor plain australia assessing post depositional disturbance and reconstructing past environments the degree to which post depositional disturbance can be assessed in archaeological sequences is critical for the development of robust chronologies for such deposits a common approach is the identification of conjoined artefacts distributed through the sequence as a measure of disturbance following deposition although this method is relatively labour intensive and does not provide a continuous record of disturbance through the entire sequence here we present 13c values for different size fractions 125 m of chemically resistant charcoal distributed through a sedimentary profile at allen s cave south australia the curves generated from both size fractions parallel one another indicating minimal disturbance through the entire profile and providing greater confidence in the luminescence and radiocarbon chronologies reported previously for the site in addition the elemental 13c values provide an indication of greater aridity compared with present persisting in this area from ca 45 to 12 ka consistent with other proxy records the onset of the holocene is marked by a shift to wetter conditions probably as a result of post glacial marine transgression and closer proximity to the coastline copyright 2001 john wiley sons ltd

sequential late cenozoic structural disruption of the northern himalayan foredeep chronologies for the siwalik molasse and intermontane basins along the southern margin of the himalaya and hindu kush ranges constrain the timing and pattern of facies migration and structural disruption of the indo gangetic foredeep this synthesis indicates that quiescent intervals are punctuated by pulses of rapid deformation as thrusting migrates in a stepwise fashion across the foredeep

martian surface mineralogy from observatoire pour la mineralogie l eau les glaces et l activite on board the mars express spacecraft omega mex global mineral maps 1 after 2 years of operation the observatoire pour la mineralogie l eau les glaces et l activite omega imaging spectrometer on board mars express has acquired data coverage of the martian surface with spatial resolution varying between 300 m and 4 8 km depending on the pericenter altitude of the spacecraft s elliptical orbit we report the global surface distributions of some minerals using the omega observations in the visible and near infrared vnir wavelength domains 0 35 2 5 m global maps of ferric phases mafic minerals pyroxenes and olivines and hydrated minerals have been derived from spectral parameters the limits of detection in terms of abundance for some minerals of different grain size distributions are given the distribution of pyroxenes is in general agreement with the mineral maps of previous telescopic and space observations the fe3 absorption feature in the visible wavelength region is present everywhere on the surface the spectra of the bright regions compare with anhydrous nanophase ferric oxides terrains with water bearing minerals cover a very small fraction of the martian surface olivine mg rich compositions is detected in more extensive regions of the pyroxene rich zones than previously reported olivine with higher iron content and or larger grain size 100 m is only detected in isolated areas the mineralogy of the northern low albedo regions is discussed in the light of these mineral maps chemical alteration or oxidation during extrusion producing a coating or varnish of anhydrous ferric phases over a dark basaltic surface best accounts for the vnir spectral properties of these regions although a glassy composition resulting from impact is also considered

water in the martian regolith from omega mars express here we discuss one of the current reservoirs of water on mars the regolith and rocks exposed at the surface this reservoir is characterized by the presence of h2o and oh bearing phases that produce a broad absorption at a wavelength of 3 m in near infrared nir reflectance spectra this absorption is present in every ice free spectrum of the martian surface obtained thus far by orbital nir spectrometers we present a quantitative analysis of the global distribution of the 3 m absorption using the observatoire pour la mineralogie l eau les glaces et l activite omega imaging spectrometer that has been mapping the surface of mars at kilometer scale for more than 10 years based on laboratory reflectance spectra of a wide range of hydrous minerals and phases we estimate a model dependent water content of 4 1 wt in the equatorial and midlatitudes surface hydration increases with latitude with an asymmetry in water content between the northern and southern hemispheres the surface hydration is compared to various parameters albedo dust geological units time relative humidity atmospheric water pressure and in situ measurements performed by phoenix and curiosity to constrain the nature of the reservoir we conclude that the nature of the surface hydration of the martian low latitudes is not adsorbed water but rather more tightly bound water molecules and hydroxyl groups in the structure of the materials of the near top surface a frost related process best explains the implementation of water into and onto the first microns of the high latitude martian regolith

palaeoenvironmental change in tropical australasia over the last 30 000 years a synthesis by the oz intimate group the tropics are the major source of heat and moisture for the australasian region determining the tropics response over time to changes in climate forcing mechanisms such as summer insolation and the effects of relative sea level on exposed continental shelves during the last glacial period is an ongoing process of re evaluation we present a synthesis of climate proxy data from tropical australasia spanning the last 30 000 years that incorporates deep sea core coral speleothem pollen charcoal and terrestrial sedimentary records today seasonal variability is governed largely by the annual migration of the inter tropical convergence zone itcz influencing this region most strongly during the austral summer however the position of the itcz has varied through time towards the end of marine isotope stage mis 3 conditions were far wetter throughout the region becoming drier first in the south universally cooler land and sea surface temperature sst were characteristic of the last glacial maximum with drier conditions than previously although episodic wet periods are noted in the fluvial records of northern australia the deglacial period saw warming first in the coral sea and then the indonesian seas with a pause in this trend around the time of the antarctic cold reversal c 14 5 ka coincident with the flooding of the sunda shelf wetter conditions occurred first in indonesia around 17 ka and northern australia after 14 ka the early holocene saw a peak in marine sst to the northwest and northeast of australia modern vegetation was first established on indonesia then progressively south and eastward to ne australia flores and the atherton tablelands show a dry period around 11 6 ka steadily becoming wetter through the early holocene the mid late holocene was punctuated by millennial scale variability associated with the el nino southern oscillation this is evident in the marine coral speleothem and pollen records of the region

tropical pacific climate at the mid holocene and the last glacial maximum simulated by a coupled ocean atmosphere general circulation model 1 simulations for the mid holocene 6000 years before present 6 ka and the last glacial maximum lgm 21 ka have been performed by a global ocean atmosphere coupled general circulation model gcm after the initial spin up periods both runs were integrated for about 200 years for 6 ka the model shows an enhanced seasonal variation in surface temperature and a northward shift of the african and the indian summer monsoon rain area overall circulation features in the tropics correspond to a strong walker circulation state with negative sea surface temperature sst and precipitation anomalies in the central pacific and positive precipitation anomalies over the indian and australian monsoon regions it is noted that there is about a 0 35 c cooling of the global mean sst in contrast to the 6 ka result the simulated tropical climate anomaly at 21 ka corresponds to a weak walker circulation state the simulated lgm sst decrease is about 2 c over the tropical western pacific it is larger about 5 c over the caribbean sea this sst anomaly is in broad agreement with the observed proxy data interestingly the model simulates a warmer than present sst over the subtropical pacific this may be related to a weaker subtropical anticyclone due to weakened monsoon circulation at the lgm

restoration and evolution of the intermontane indus molasse basin ladakh himalaya india abstract collision of the indian plate with the karakorum plate lhasa block during the eocene ca 55 50 ma created predominantly a s or sw verging thrust culmination across the himalaya during the late tertiary two molasse basins existed the siwalik bain formed in the late miocene to present on the indian foreland south of the himalaya and the mid eocene to late miocene indus basin along the indus suture zone north of the high himalaya the indus basin is approximately 2000 km long extending eastwards from ladakh across south tibet a balanced cross section along the zanskar river shows a minimum 36 km shortening in the eocene late miocene molasse and suggests that the minimum basin width was approximately 60 km in ladakh more than 2000 m of post eocene alluvial fan fluvial and fluvio lacustrine sediments accumulated in the ladakh sector with petrographies suggesting derivation mainly from the deeply dissected and uplifted northern granodioritic ladakh batholith aptian eocene with only minor amounts of debris derived from the deformed southern tethyan passive margin palaeocurrents show predominant e w axis parallel sediment transport with subordinate lateral input paths being preserved the indus molasse basin is deformed by numerous post eocene n directed backthrusts many of which cut the entire stratigraphy and therefore were active at least into late tertiary times

continental scale river flow in climate models abstract the hydrologic cycle is a major part of the global climate system there is an atmospheric flux of water from the ocean surface to the continents the cycle is closed by return flow in rivers in this paper a river routing model is developed to use with grid box climate models for the whole earth the routing model needs an algorithm for the river mass flow and a river direction file which has been compiled for 4 5 and 20 2 5 resolutions river basins are defined by the direction files the river flow leaving each grid box depends on river and lake mass downstream distance and an effective flow speed that depends on topography as input the routing model uses monthly land source runoff from a 5 yr simulation of the nasa giss atmospheric climate model hansen et al the land source runoff from the 4 5 resolution model is quartered onto a 2 2 5 grid and the effect of grid resolution is examined monthly flow at the mouth of the world s major rivers is compared with observations and a

comparative uranium thorium and thermoluminescence dating of weathered quaternary alluvium in the tropics of northern australia abstract thermoluminescence tl age determinations of alluvial sediments in the tropics are evaluated by comparison with u th age determinations of pedogenic accumulations in the alluvium of the lower gilbert river a large fan delta in the wet dry tropics of northern queensland australia this study extends u th dating by applying it not only to calcretes but also to fe mn oxyhydroxide oxide accumulations while a direct correlation cannot be made between u th dates from secondary minerals and tl dates from the host sediments both sets of data show broad consistency in addition to providing a minima for acceptable tl ages u th dates are useful for determining the chronology of pedogenesis diagenesis they show that calcretes and ferricretes have formed under similar climatic conditions in the wet dry tropics of northern australia during the late pleistocene beneath about 5 12 m the gilbert fan delta consists of an extensive sand body older than 85 000 yr and probably about 120 000 yr in age representative of a period of major fluvial activity not repeated since this time above are muds and fine sandy muds that extend uninterrupted to the present surface except in the downstream fan where they are bisected by a thin unit of medium sand that tl dates at 40 000 50 000 yr b p a system of sandy distributary channels over the fan surface represents an early holocene fluvial phase probably more active than at present

proximal braidplain deposits in the middle devonian malbaie formation of eastern gaspe quebec canada the middle devonian malbaie formation of eastern gaspe canada comprises sharply alternating conglomerate and sandstone units their petrography suggests derivation from the same source but palaeocurrents indicate different dispersal systems for the sand and gravel the principal conglomerate facies is horizontally stratified with well developed imbrication characteristic of deposition on a high energy proximal braidplain minor cross stratified conglomerate shows well defined size sorting attributed to avalanching down foresets and sorting within minor bedforms on bar tops the sandstone units mainly comprise erosion surfaces overlain by mudstone intraclasts alternating with lineated low angle to horizontally stratified sandstone or trough cross stratified sandstone the sandstone units were deposited on a proximal braidplain with highly variable discharge but the absence of calcrete indicates that dry periods were not prolonged the malbaie is the coarsest uppermost formation of a devonian clastic wedge formed during the acadian orogeny the uniformity of facies association and palaeocurrents particularly in conglomerate units indicates derivation from a broad upwarp to the south this implies that the acadian uplands resulted from straight compression in contrast to the localized uplifts formed by strike slip faulting during the carboniferous

mechanisms of mid holocene precipitation change in the south pacific convergence zone abstractthe variability of the south pacific convergence zone spcz during the mid holocene is investigated using models archived in the paleoclimate modelling intercomparison project phase ii pmip2 database relative to preindustrial conditions mid holocene top of atmosphere insolation was relatively lower during austral summer december february djf which is the season when the spcz is at its peak intensity in response to this perturbation the pmip2 models simulate a displacement of the spcz to the southwest this spcz shift is associated with a sea surface temperature sst dipole with increased rainfall collocated with warm sst anomalies decomposing the djf precipitation changes in terms of a diagnostic moisture budget indicates that the spcz shift is balanced to leading order by a change in the mean moisture convergence changes to the broad area of upper level negative zonal stretching deformation where transient eddies can become trapped and subsequently generate deep convection suppo

paleomagnetic chronology fluvial processes and tectonic implications of the siwalik deposits near chinji village pakistan a 2800 m section of siwalik strata containing the stratotypes for both the chinji and nagri formations has been dated by magnetic polarity stratigraphy and the observed polarity zonation has securely been correlated with the chron 17 7 segment of the time scale the base of the section is the base of the kamlial formation which occurs near the top of chron 17 18 3 m y the kamlial chinji formation boundary occurs in the middle of chron 15 14 3 m y the chinji nagri boundary near the bottom of chron 10 10 8 m y and the nagri dhok pathan boundary at the chron 8 9 boundary 8 5 m y the siwalik deposits near chinji village consist of four distinct classes of fluvial cycles each with a characteristic periodicity a first order of 10 7 years a second order of 10 6 years a third order of 10 4 10 5 years and a fourth order of 10 0 10 4 years the river system responsible for siwalik sedimentation flowed from west to east and had properties much like the modern ganges river syste

transition from foreland to piggyback basin deposition plio pleistocene upper siwalik group shinghar range nw pakistan plio pleistocene synorogenic deposits of the upper siwalik group in the shinghar range trans indus salt ranges of north western pakistan record the transition from foreland basin to piggyback basin deposition on the hangingwall of the salt range thrust the siwalik and upper siwalik groups are over 4 km thick in the shinghar range the lower 3 km consists of the miocene siwalik group which was deposited by a south flowing foreland trunk stream the palaeo indus river the upper 1 5 km consists of the upper siwalik group which is herein divided into three members the lowest member includes deposits of the south flowing palaeo indus river and is distinguished from the underlying siwalik group by the first appearance of conglomerate the transition from the lower member to the middle member is interpreted as recording uplift on the salt range thrust as the salt range thrust was active the palaeo indus river was bifurcated to the east and west around the embryonic shinghar range and overbank and lacustrine deposition occurred represented by the middle member when the shinghar range achieved significant topography the upper member was deposited by streams transporting gravel and sand that flowed north and west out of the range and into a piggyback basin that formed on the hangingwall of the salt range thrust new and previously published palaeomagnetic stratigraphy and fission track ages from volcaniclastic deposits within the upper siwalik group provide tight constraints on the chronology of sedimentary facies transitions and timing of uplift of the shinghar range the integration of sedimentological and geochronological data indicates that motion on the salt range thrust and repositioning of the indus river began at 1 0 ma

variability of the indian ocean dipole in coupled model paleoclimate simulations 1 the indian ocean dipole iod mode of variability has been observed to influence atmospheric circulation and precipitation over the indian ocean basin and surrounding continental areas interacting with the asian monsoon and el nino southern oscillation enso paleo iod reconstructions from fossil corals from the eastern tropical indian ocean suggest that iod events may have varied in strength and timing under past climate conditions the variability of the iod and interactions with the asian monsoon and enso are investigated here using a series of coupled model simulations of time slices during the last 55 000 years the fast ocean atmosphere model foam is used to simulate pre industrial climate and paleoclimate time slices at 6 000 11 000 21 000 35 000 and 55 000 years before present the strength and timing of iod events in the foam simulations is found to vary with larger amplitude iod variability being associated with a weaker asian summer monsoon and stronger enso variability foam simulates a reduced strength iod in the mid holocene and stronger iod variability in the last glacial maximum time slice there is some evidence that the timing of iod events varies in response to changes in insolation seasonality over the tropical indian ocean and resulting changes in the timing and amplitude of the asian summer monsoon and enso

sensitivity of the australian monsoon to insolation and vegetation implications for human impact on continental moisture balance general circulation model experiments test the geologically based correlation of high monsoon rainfall over interior australia with northern hemisphere insolation and evaluate the sensitivity of the australian monsoon to ecosystem change our results suggest that northern hemisphere insolation control on the intensity of the siberian high rather than summer insolation over the australian continent determines the strength of the australian monsoon on millennial time scales unlike a classic monsoon regime additional simulations show that the penetration of monsoon moisture into the interior is sensitive to biosphere atmosphere feedbacks linked to vegetation type and soil properties this sensitivity offers a resolution to the observed failure of the australian monsoon to penetrate the interior in the holocene postulated regular burning practiced by early humans may have converted a tree shrub grassland mosaic across the semiarid zone to the modern desert scrub thereby weakening biospheric feedbacks and resulting in long term desertification of the continent

mineralogy composition and alteration of mars pathfinder rocks and soils evidence from multispectral elemental and magnetic data on terrestrial analogue snc meteorite and pathfinder samples major element multispectral and magnetic properties data were obtained at ares vallis during the mars pathfinder mission to understand the compositional mineralogical and process implications of these data we obtained major element mineralogical and magnetic data for well crystalline and nanophase ferric minerals terrestrial analogue samples with known geologic context and snc meteorites analogue samples include unaltered palagonitic and sulfatetic tephra from mauna kea volcano hydrolytic and acid sulfate alteration steam vent material from kilauea volcano hydrolytic alteration and impactites from meteor crater relithification salient results for mars pathfinder include 1 band depths bd530b and bd600 and the reflectivity ratio r800 r750 are consistent with the dominant ferric mineral being nanophase ferric oxide associated with an unknown amount of h2o and occurring in composite particles along with subordinate amounts of other ferric minerals hematite and hematite plus nanophase goethite are most consistent with the data but maghemite akaganeite schwertmannite and nanophase lepidocrocite are also possible interpretations ferric oxides that are consistently not favored by the data as sole alteration products are jarosites and well crystalline goethite and lepidocrocite 2 the strength of the ferric adsorption edge r750 r445 implies the fe3 fe2 values for pathfinder rock and soil are within the ranges 0 7 3 and 3 20 respectively 3 ferrous silicates are indicated for subsets of pathfinder rocks and soils one subset has a band minimum near 930 nm that can attributed to low ca pyroxene alternatively the band could be a second manifestation of certain ferric oxides including nanophase goethite maghemite akaganeite and schwertmannite another subset has a negative spectral slope from 800 to 1005 nm which could result from the high energy wing of a high ca pyroxene and or olivine band a mixture of bright and dark materials and for rocks thin coatings of bright dust on dark rocks 4 chemical data on pathfinder rocks and soils are consistent with two component mixtures between an andesitic rock with low mgo and so3 concentrations soil free rock and a global basaltic soil with high mgo and so3 concentrations rock free soil pathfinder rock free soil can be modeled as a chemical mixture of snc meteorites and the pathfinder soil free rock 5 pathfinder soil cannot be obtained by chemical alteration of pathfinder rocks by any of the hydrolytic and acid sulfate alteration processes we studied presumably global mixing has obscured and possibly erased the elemental signatures of chemical alteration 6 the strongly magnetic phase in palagonitic and sulfatetic tephra is titanomagnetite and possibly its oxidation product titanomaghemite fe ti spinels the saturation magnetization of the tephra samples 0 5 2 0 am2 kg is at or below the low end of the range inferred for martian dust 4 2 am2 kg implying that lithogenic fe ti spinels are a possible candidate for the martian strongly magnetic phase 7 the predominantly palagonitic spectral signature and magnetic nature of martian soil and dust are consistent with glassy precursors with imbedded fe ti spinel particles comparison with lunar glass production rates suggests that production of sufficient quantities of glassy materials on mars by volcanic and impact processes is sufficient to account for these observations

the human colonisation of australia optical dates of 53 000 and 60 000 years bracket human arrival at deaf adder gorge northern territory the date at which people entered australia has important implications for the debate on modern human origins thermoluminescence dates of 50 60 ka reported for initial occupation of the malakunanja ii site in northern australia have been used as a means of calibrating the rate of mitochondrial and nuclear dna evolution in modern humans optical dating of unburnt quartzose sediments from a rock shelter site nauwalabila i lindner site in deaf adder gorge 70 km south of malakunanja ii provides new evidence for the timing of the colonisation of the continent optical dates were determined for several stratigraphic levels within a 3 m deep excavation in which flaked stone artefacts and ground pigments were found in primary depositional setting the lowest human occupation levels are bracketed by dates of 53 4 5 4 ka and 60 3 6 7 ka while the upper levels show good agreement between optical and calibrated 14c age estimates high quality haematite with ground facets and striations is associated directly with the 53 ka level and indicates the use of pigments by these early australians the optical dates independently confirm evidence for the colonisation of northern australia shortly after 60 ka and should be seen in the context of this region as having been a likely entry route for the first human movements into sahul

morphology sedimentology and palaeohydraulic significance of large gravel dunes altai mountains siberia coarse gravel bedforms which resulted from pleistocene glacial outburst floods are identified as subaqueous dunes comparison of the morphology of these fossil structures with modern dunes shows that the form of two dimensional 2 d transverse dunes and 3 d cuspate and lunate dunes developed in coarse gravels is comparable with sand dune morphology within lesser scale geophysical flows the similarity of the steepest gravel dunes with equilibrium dunes in sand indicates that grain size is not a major factor in constraining primary duneform internal structure indicates that flow over 2 d dunes was relatively uniform but over 3 d bedforms flow was locally variable flow separation and complex streaming of flow occurred over the steepest 3 d dunes cross beds are thin and few approach the angle of repose consequently most dunes did not migrate primarily by avalanching but by stoss entrained gravel transported over the crests rolling down and depositing on the lee slopes the lee formed when flood power was waning some dunes were siightly planed down during falling stage because lee side cross beds tend to be steeper than the angle of the preserved lee slope however silt rich caps indicate that any height reduction was contemporary with the final deposition of foresets post flood modification has been negligible although the modern topography is subdued by loess deposits within the dune troughs lee side sediments are often finer than the stoss slope sediments which indicates

mineralogic and compositional properties of martian soil and dust results from mars pathfinder mars pathfinder obtained multispectral elemental magnetic and physical measurements of soil and dust at the sagan memorial station during the course of its 83 sol mission we describe initial results from these measurements concentrating on multispectral and elemental data and use these data along with previous viking snc meteorite and telescopic results to help constrain the origin and evolution of martian soil and dust we find that soils and dust can be divided into at least eight distinct spectral units based on parameterization of imager for mars pathfinder imp 400 to 1000 nm multispectral images the most distinctive spectral parameters for soils and dust are the reflectivity in the red the red blue reflectivity ratio the near ir spectral slope and the strength of the 800 to 1000 nm absorption feature most of the pathfinder spectra are consistent with the presence of poorly crystalline or nanophase ferric oxide s sometimes mixed with small but varying degrees of well crystalline ferric and ferrous phases darker soil units appear to be coarser grained compacted and or mixed with a larger amount of dark ferrous materials relative to bright soils nanophase goethite akaganeite schwertmannite and maghemite are leading candidates for the origin of the absorption centered near 900 nm in imp spectra the ferrous component in the soil cannot be well constrained based on imp data alpha proton x ray spectrometer apxs measurements of six soil units show little variability within the landing site and show remarkable overall similarity to the average viking derived soil elemental composition differences exist between viking and pathfinder soils however including significantly higher s and cl abundances and lower si abundances in viking soils and the lack of a correlation between ti and fe in pathfinder soils no significant linear correlations were observed between imp spectral properties and apxs elemental chemistry attempts at constraining the mineralogy of soils and dust using normative calculations involving mixtures of smectites and silicate and oxide minerals did not yield physically acceptable solutions we attempted to use the pathfinder results to constrain a number of putative soil and dust formation scenarios including palagonitization and acid fog weathering while the pathfinder soils cannot be chemically linked to the pathfinder rocks by palagonitization this study and mcsween et al 1999 suggest that palagonitic alteration of a martian basaltic rock plus mixture with a minor component of locally derived andesitic rock fragments could be consistent with the observed soil apxs and imp properties

sedimentology of the indus group ladakh northern india implications for the timing of initiation of the palaeo indus river the upper reaches of the indus river form a longitudinal network that drains a large portion of the western himalaya it plays an important role as a sediment routing system feeding the indus delta and submarine fan and has played a controlling role in the denudational history of the western himalaya given the rivers long term significance its timing of initiation remains poorly constrained the facies palaeocurrents and provenance of the post early eocene indus group preserved along the upper reaches of the modern indus reveal a history of fluvial deltaic and deep water sedimentation in an intermontane basin dominated by internal drainage hence the indus group is not considered to represent the deposits of a palaeo indus river as previously thought illite crystallinity values and apatite fission track dating of the indus group suggest that the succession was buried to temperatures of 155 280 c and that unroofing started in early miocene times and proceeded at 0 1 0 4 mm a 1 to the present the youngest sedimentary rocks preserved along the indus basin are early miocene in age from the tectonostratigraphically equivalent deposits around kargil to the west of the study area the transition from sediment accumulation to erosional unroofing in early miocene times coincides with accelerated regional unroofing of the high himalayas to the south and the initiation of the indus delta submarine fan to the west differential uplift between the northward thrusting of the zanskar and indus sedimentary succession against the undeformed ladakh batholith provides a mechanism for post early miocene initiation of a major longitudinal river hence early miocene times is believed to represent the earliest possible age of initiation of the palaeo indus river following this course

ams radiocarbon dating in the study of arid environments examples from lake eyre south australia abstract sediments containing small amounts of carbon are difficult to date using traditional radiocarbon techniques this has resulted in less than satisfactory attempts to establish reliable chronologies for sedimentation and environmental change in the australian arid zone we describe here the first application of the ams technique to the radiocarbon dating of salt lake core samples using a chemical pretreatment methodology based on pollen extraction techniques these results indicate that fine grained charcoal and pollen have a similar source and depositional mechanism the data from lake eyre imply a last glacial maximum deposition for the major buried halite layer an early holocene return to lacustrine conditions with a late holocene reduction of net sediment inout to madigan gulf as the present playa conditions were established

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

sedimentology of plio pleistocene late orogenic deposits associated with intraplate subduction the upper siwalik subgroup of a part of panjab sub himalaya india abstract this study provides a detailed sedimentologic documentation of the lithofacies cyclicity sandbody geometry palaeoflow variability and depositional models of the youngest late orogenic deposits of the siwalik molasse these deposits represent one of the important examples of sedimentation in the zone of intraplate subduction of the himalayan collision belt lithofacies analysis has resulted in the recognition of four conglomerate facies massive matrix supported conglomerate crudely stratified conglomerate trough cross stratified conglomerate planar cross stratified conglomerate five sandstone facies erosional scour and fill pebbly sandstone medium to coarse grained sandstone fine to medium grained ripple drift laminated sandstone bioturbated calcareous fine grained sandstone and six mudstone facies parallel laminated bioturbated mudstone reddish brown massive mudstone variegated mudstone bluish grey to violet mudstone buff coloured mudstone pebbly mudstone in addition hard calcareous layers have been recognised as a separate facies state the deduced cyclic sequences of the tatrot and pinjor formations of the upper siwalik subgroup show fining upward characters from cs coarse sandstone to ms mudstone through fs fine sandstone and ss alternations of sandstone and siltstone the sandbodies of the tatrot and pinjor formations reveal a sheet like geometry and an internal dominance of inter storey scour surfaces the presence of intraformational debris mud drapes reactivation surfaces and a general fining upward of grain size indicates fluctuating hydrodynamic conditions with frequent channel abandonment and re occupation resulting in net vertical aggradation the dominant style of sedimentation both in the channel and overbank facies is through vertical aggradation data on the palaeoflow variability indicates that the upper siwalik subgroup can be subdivided into four and three sediment vector sequences in the khetpurali and ghaggar sections respectively the palaeodrainage pattern in the khetpurali section reveals a major influence of northerly drainage twice in the stratigraphic column the high percentage of overbank deposits in individual cycles the lack of vegetal debris organic poor palaeosol units and abundant syngenetic caco 3 activity warrant comparison with the modern anastomosed deposits described from arid central australia some intervals of the sequences are comparable to the sublinear subparallel drainages with local anastomosis of the modern piedmont zone of the himalaya the higher parts of the stratigraphic column indicate proximal braided stream deposits and finally proximal alluvial fan deposits syntectonic activity has controlled the deposition of the megasequences which are a response to episodicity in the activity of basin margin basin margin or basin margin intrabasin structures the vertical stacking of the siwalik megasequences appears to be episodic in character

antarctic permafrost an analogue for water and diagenetic minerals on mars at high altitudes 1000 m throughout the dry valleys antarctica liquid water is rare yet ground ice which may be millions of years old is pervasive in glacial sediments and bedrock the origin of this ice is different from its arctic and alpine counterparts and may be similar to water on mars we present chemical and isotopic analyses of antarctic ground ice from cores of sirius group sediments at table mountain in the dry valleys these data together with the presence of diagenetic calcite and chabazite in the frozen sediments indicate that the ice and minerals accumulated over long periods of time from atmospheric water vapor and brine films formed on the surface of the ground this analogy indicates that ferric bearing minerals could precipitate under present conditions in the martian soil

reconciliation of late quaternary sea levels derived from coral terraces at huon peninsula with deep sea oxygen isotope records a major discrepancy between the late quaternary sea level changes derived from raised coral reef terraces at the huon peninsula in papua new guinea and from oxygen isotopes in deep sea cores is resolved the two methods agree closely from 120 ka to 80 ka and from 20 ka to 0 ka ka 1000 yr before present but between 70 and 30 ka the isotopic sea levels are 20 40 m lower than the huon peninsula sea levels derived in earlier studies new high precision u series age measurements and revised stratigraphic data for huon peninsula terraces aged between 30 and 70 ka now give similar sea levels to those based on deep sea oxygen isotope data planktonic and benthic 18o data using the sea level and deep sea isotopic data oxygen isotope ratios are calculated for the northern continental ice sheets through the last glacial cycle and are consistent with results from greenland ice cores the record of ice volume changes through the last glacial cycle now appears to be reasonably complete