elemental compositions and monazite age patterns of core sediments in the changjiang delta implications for sediment provenance and development history of the changjiang river core from a continuous borehole in the changjiang delta to a depth of 318 7 m dated back to the pliocene 3 58 ma and was selected for geochemical measurements and determinations of th u pb ages of monazite in order to investigate the changing sediment provenance and development history of the changjiang river geochemical proxies including fractionation parameters of rare earth elements cerium and europium anomalies and elemental ratios cr th nb co and th co suggest that the pliocene and quaternary sediments have remarkably different provenances six peak ages of monazite grains dated at 25 50 200 200 400 400 550 800 1000 and 1800 2000 ma are consistent with the main tectonic and magmatic events in the yangtze craton the data imply that the pliocene sediments were mostly derived from proximal and more silicic sources whereas the quaternary sediments were sourced from distal and more basic provenances including the emeishan basalt province in the upper changjiang valley we propose that during the pliocene the paleo changjiang or its eastern equivalent was a locally small river draining today s lower changjiang valley whereas during the early pleistocene not later than 1 18 ma it changed its drainage pattern and developed into a large river that originated from the eastern tibetan plateau this time matches well with many previous studies based upon geomorphologic geographic and tectonic observations in the jinshajiang valley and the three gorges

planetary surface dating from crater size frequency distribution measurements partial resurfacing events and statistical age uncertainty abstract we describe the procedure to fit a cumulative production function polynomial to a partial crater size frequency distribution the technique is of particular use in deriving ages for surfaces which have undergone partial resurfacing events namely erosional or depositional events which have affected a limited diameter range of the crater population we demonstrate its use in obtaining times for both the surface formation and the resurfacing event we give a practical outline of the method for making age measurements from crater counts and how to identify resurfacing effects in the results we discuss the conversion of production function polynomials between common presentations and the statistical uncertainty of the determined ages with respect to the non linear chronology function and a minor refinement of data binning

provenance and weathering control on river bed sediments of the eastern tibetan plateau and the russian far east abstract we investigated the petrography and major trace and rare earth element compositions of the bed sediments from the large rivers draining the eastern tibetan plateau etp the huang he yellow chang jiang yangtze hong he red mekong and salween the combined drainage spans tropical temperate and arid climate zones in addition samples from the lena river draining the verkhoyansk and sette daban ranges in an arctic to sub arctic climate zone in siberia were also studied for their major and trace element composition the sub angular texture the quartz feldspar rock fragment classification in the lithic arenite field and the relatively low chemical index of alteration cia 42 79 indicate that these sediments are texturally petrographically and chemically immature and immobile trace elements can be used to obtain some information about the lithologic provenance the etp river sediments are felsic and similar to the upper continental crust with the salween most felsic and the lena most mafic the sediments show a gradation in maturity that is not clearly related to present climatic or physiographic regime this suggests that maturity itself is a relict feature inherited from previous sedimentary cycles the high physical erosion in such high energy and relief systems seems to inhibit intense weathering and manifests a provenance control from local rocks on the sediment compositions

erosional history of the eastern tibetan plateau since 190 kyr ago clay mineralogical and geochemical investigations from the southwestern south china sea a high resolution study of clay mineralogy and major element geochemistry has been conducted on high sedimentation rate cores md01 2393 and md97 2150 collected off the mekong river mouth in the southwestern south china sea in order to reconstruct the erosional and weathering history of the mekong basin the chronology is based upon planktonic foraminiferal oxygen isotope records combined with carbonate stratigraphy clay minerals and major element results suggest that the mekong river is the major sedimentary source over the past 190 kyr for both cores illite and chlorite were derived mainly from the eastern tibetan plateau kaolinite was derived mainly from active erosion of inherited clays from reworked sediments in the middle part of the mekong basin smectites originated mainly through chemical weathering of parent aluminosilicate and ferromagnesian silicate under warm and humid conditions in the middle to lower parts of the mekong basin smectites illite chlorite and smectites kaolinite ratios coupled to k2o sio2 and al2o3 sio2 ratios allow us to reconstruct a history of chemical weathering versus physical erosion good correlations between those ratios suggest monsoon controlled weathering and erosion over the eastern tibetan plateau and the mekong basin variations with time scales of 0 3 0 6 kyr for the last 70 kyr and 1 2 kyr for 70 190 kyr ago in the chemical weathering erosional history are strongly related to the east asian monsoon evolution which is itself related to the summer solar radiation calculated for the northern hemisphere d 2004 elsevier b v all rights reserved

late quaternary variability of precipitation in southern california and climatic implications clay mineral evidence from the santa barbara basin odp site 893 abstract clay mineral assemblages have been investigated in a sequence of late quaternary age sediments 160 ka from the santa barbara basin off california these predominantly terrigenous sediments contain an assemblage of clay minerals dominated by smectite mostly derived from discharges of the santa clara river together with illite and kaolinite from adjacent relief besides its characteristic clay mineral signature the santa clara river has the largest drainage basin in this region and contributes most of the terrigenous load to the santa barbara basin smectite contents of the sediments in the basin may therefore be used as a proxy for precipitation and run off distinct changes in the relative abundance of smectite allow reconstruction of the pattern of precipitation and its relations with regional environments and global climate this showed that major intervals of precipitation coincide with local development of pine during glacials and oak during terminations and interglacials some expansion of mountain glaciers in the sierra nevada especially when they occur during local minima of insolation and lacustrine developments in the now arid continental interior of california major precipitation intervals started during glacials and persisted during terminations and early interglacials associated with a weak california current and subsequent expansion of warm pacific surface waters in detail major precipitation intervals consist of alternating episodes of higher and lower rainfall modulated by orbital precession with a significant correlation between episodes of high rainfall and minima in precession which were times of increased meridional gradients enhanced poleward heat transfer and northward expansion of tropical waters

paleoenvironmental and archaeological investigations at qinghai lake western china geomorphic and chronometric evidence of lake level history abstract qinghai lake located on the northeastern qinghai tibet plateau qing zang gaoyuan is china s largest extant closed basin lake its position relative to major asian climate systems makes it sensitive to global climate change the lake has been the subject of numerous paleoenvironmental investigations including dating of shoreline features around the lake basin here we report new age estimates of shoreline features geomorphic exposures and archaeological sites that contribute to the development of a lake level history for qinghai lake and a landscape model of the qinghai lake basin lake highstands above 3230 m 36 m above the modern lake level appear to date to late mis 5 70 110 ka the lake has had much more modest highstands since then no evidence of mis 3 lake stands higher than modern were found and early holocene highstands are no more than 12 m above modern if the age of highstands greater than 3230 m is confirmed through future work then the qinghai lake basin hydrologic balance prior to 70 ka was dramatically different than after that time including during the holocene a simple hydrologic balance model provides insights into the combination of precipitation evaporation and runoff generation needed to sustain the lake at 3260 m the highest shoreline observed a range of factors may explain the difference primarily the relative strength of the east asian monsoon the basin was apparently subject to extensive alluviation during mis 3 interrupted by widespread erosion and development of cryogenic features before and during the last glacial maximum lgm loess that presently drapes much of the lower basin landscape began to be deposited after the lgm 16 18 ka the landscape model outlined here has implications for archaeological visibility of early human occupation of the qinghai tibet plateau

clay mineral record in lake baikal sediments the holocene and late glacial transition abstract we analyse the clay mineralogical composition of two 1 m long cores from elevated plateaus in the southern and northern basins of lake baikal our aim is to test the limits of classically used clay proxies for climate reconstructions mineralogical signature is determined by x ray diffraction on oriented aggregates from holocene and late glacial sediments mineralogical results are presented on a palaeomagnetic derived time scale sampling at a centimeter resolution allows for a sub millenial order reconstruction the evolution of clay derived climate proxies smectite illite peak intensity ratio s i is compared between the two locations with respect to other climate reconstructions for the lake baikal area and siberia during the late glacial punctual increases of s i are related to changes of particle source rather than any climate change at both sites the most intense chemical weathering conditions occured during the subboreal lagging the eurasian middle atlantic climate optimum s i follows a gradual but irregular increase through the holocene probably related to slow warming favourable to the development of the siberian soils the different sensitivity to hydrolysing conditions in northern and southern sites can be explained by a combination of local lithological and topographical parameters

stable isotopes of lake and fluid inclusion brines dabusun lake qaidam basin western china hydrology and paleoclimatology in arid environments the qaidam basin underlain by salt is the largest 120 000 km2 on the qinghai tibet plateau western china numerous shallow to ephemeral saline lakes and dry saline pans are present on the qarhan salt plain dabusun lake the largest about 200 km2 contains high salinity na mg cl brines whereas it precipitates halite it is fringed by a potash salt flat the dominant inflow to dabusun lake the golmud river contains dilute na hco 3 rich meteoric waters dabusun lake brines fall on an evaporation trend given by d 3 3 18o 43 both d and 18o values increase with salinity which in turn varies considerably with flooding and evaporation the isotope compositions of the fluid inclusion brines from modern halite formed along the lake s edge are intermediate to those of dabusun lake brines and those from the salt flat shallow sediments beneath qarhan consist of interbedded salts and mud a short core section 1 3 1 7 m depth from the northern edge of dabusun lake was found to contain three dissolution surfaces and three mud partings the 18o values for fluid inclusions in 22 primary halite samples from this section show a record of episodic flooding lower 18o values followed by evaporation gradual increase in 18o values primary fluid inclusions in halite crystallized initially at the surface provide a geochemical record of surface brines their major element compositions varied through time more concentrated fluids indicate more arid conditions in the basin whereas wetter conditions prevailed during intervals of non salt deposition when laminated muds accumulated the isotope compositions together with the activity of h2o of fluid inclusions in primary halite were used to determine isotope variations in regional precipitation and hence paleoclimatic changes on the qinghai tibet plateau during the past 50 000 years

sample preparation effects on illite crystallinity measurement grain size gradation and particle orientation abstract specimen thickness is the main experimental factor controlling the results of illite crystallinity ic or crystallite size measurements on sedimentation slides different values obtained from thick and thin preparations are due to grain size gradation effects which may exclude larger and higher ordered grains from contributing to the diffraction orientation effects control the measured peak intensity the change from poor particle orientation in thick slides to high orientation in very thin slides is marked by an increase in specimen density diminishing non basal reflections and by a strong increase in peak intensity a plateau with constant peak breadths is observed if thin slides of well ordered platy illites are used a similar plateau can be recognized for thick preparations of specimens from less ordered materials but not from well ordered ones therefore it is suggested that ic is determined on very thin sedimentation slides with a thickness of 0 25 mg cm2 or less ultrasonic and h2o2 treatments enhance the degree of particle orientation by destruction of grain aggregates and organic compounds leading to smaller peak breadths and higher intensities

lunar central peak mineralogy and iron content using the kaguya multiband imager reassessment of the compositional structure of the lunar crust ryder and wood 1977 suggested that the lunar crust becomes more mafic with depth because the impact melts associated with the large imbrium and serenitatis basins are more mafic than the surface composition of the moon in this study we reexamine the hypothesis that the crust becomes more mafic with depth we analyze the composition of crater central peaks by using recent remote sensing data and combining the best practices of previous studies we compute the mineralogy for 34 central peaks using 1 nine band visible and near infrared data from the kaguya multiband imager 2 an improved version of hapke s radiative transfer model validated with spectra of lunar soils with well known modal mineralogy and 3 new crustal thickness models from the gravity recovery and interior laboratory data to examine the variation in composition with depth we find that there is no increase in mafic mineral abundances with proximity to the crust mantle boundary or with depth from the current lunar surface and therefore that the crust does not become more mafic with depth we find that anorthosite with very low mafic abundance purest anorthosite or pan is a minority constituent in these peaks and there is no clear evidence of a distinct pan rich layer in the middle crust as previously proposed the composition of most of the central peaks we analyze is more mafic than classically defined anorthosites with an average noritic anorthosite composition similar to that of the lunar surface

evidence for basaltic volcanism on the moon within the past 100 million years the majority of basaltic volcanism on the moon occurred more than 3 billion years ago small mounded formations on the lunar nearside may be products of basaltic eruptions less than 100 million years ago suggesting a long decline of magmatic activity

influence of late cenozoic mountain building on ocean geochemical cycles in a steady state ocean input fluxes of dissolved salts to the sea must be balanced in mass and isotopic value by output fluxes for the elements strontium calcium and carbon rivers provide the primary input whereas marine biogenic sedimentation dominates removal dissolved fluxes in rivers are related to rates of continental weathering which in turn are strongly dependent on rates of uplift the largest dissolved fluxes today arise in the himalayan and andean mountain ranges and the tibetan plateau during the past 5 m y uplift rates in these areas have increased significantly this suggests that weathering rates and river fluxes may have increased also the oceanic records of carbonate sedimentation level of the calcite compensation depth and delta sup 13 c and delta sup 87 sr in biogenic sediments are consistent with a global increase in river fluxes since the late miocene the cooling of global climate over the past few million years may be linked to a decrease in atmospheric co sub 2 driven by enhanced continental weathering in these tectonically active regions

evolution of chaka salt lake in nw china in response to climatic change during the latest pleistocene holocene abstract the late pleistocene and holocene hydrologic balance of chaka salt lake in the eastern qaidam basin of nw china was studied based on the analysis of lithostratigraphy mineralogy total organic carbon and total nitrogen from a 9 0 m long sediment core an age depth model for the lake sediments is based on eight accelerator mass spectrometry ams 14 c measurements of organic matter and a 1700 year radiocarbon reservoir correction the pitzer model was used to calculate the sequence of minerals precipitated as a function of salinity assuming that the initial lake water was recharged from adjacent rivers and springs lake salinity values were derived from a good match between the calculated and observed mineral sequences our multi proxy based hydrologic reconstruction of chaka lake indicates that it was a clastic dominated freshwater lake between 17 2 and 11 4 cal ka bp which may have resulted from the input of glacial water into the lake at that time during the lateglacial and holocene a warm climatic regime predominated between 13 9 and 12 7 cal ka bp and then a cold climatic regime prevailed between 12 7 and 11 4 cal ka bp these warm and cold periods correlate with the bolling allerod and younger dryas events in the region beginning at 11 4 cal ka bp a saline or hypersaline lake developed which may have resulted from increased summer insolation and temperatures these conditions persisted throughout the holocene modeling indicates that lake salinity fluctuated between 66 and 223 ppt from 11 4 to 7 2 cal ka bp and then increased to 223 322 ppt between 7 2 and 6 0 cal ka bp when most regions of china recorded high moisture availability i e the so called mid holocene climatic optimum lake salinity decreased to 66 223 ppt during a short time period between 6 0 and 5 3 cal ka bp possibly caused by reduced evaporation subsequently salinity values rapidly increased to 223 322 ppt between 5 3 and 5 2 cal ka bp and a hypersaline lake with a salinity higher than 324 ppt similar to modern chaka salt lake became established around 5 2 cal ka bp this establishment may have been related to the weakening of asian monsoon regional comparisons of paleoclimatic records indicate that large temporal and spatial variations exist in the occurrence and intensity of drought over western china since the lateglacial

a combined spectrophotometric and morphometric study of the lunar mare dome fields near cauchy arago hortensius and milichius in this study we examine the spectral and morphometric properties of the four important lunar mare dome fields near cauchy arago hortensius and milichius we utilize clementine uv vis mulfispectral data to examine the soil composition of the mare domes while employing telescopic ccd imagery to compute digital elevation maps in order to determine their morphometric properties especially flank slope height and edifice volume after reviewing previous attempts to determine topographic data for lunar domes we propose an image based 3d reconstruction approach which is based on a combination of photoclinometry and shape from shading accordingly we devise a classification scheme for lunar marc domes which is based on a principal component analysis of the determined spectral and morphometric features for the effusive mare domes of the examined fields we establish four classes two of which are further divided into two subclasses respectively where each class represents distinct combinations of spectral and morphometric dome properties as a general trend shallow and steep domes formed out of low tio2 basalts are observed in the hortensius and milichius dome fields while the domes near cauchy and arago that consist of high tio2 basalts are all very shallow the intrusive domes of our data set cover a wide continuous range of spectral and morphometric quantities generally characterized by larger diameters and shallower flank slopes than effusive domes a comparison to effusive and intrusive mare domes in other lunar regions highland domes and lunar cones has shown that the examined four mare dome fields display such a richness in spectral properties and 3d dome shape that the established representation remains valid in a more global context furthermore we estimate the physical parameters of dome formation for the examined domes based on a rheologic model each class of effusive domes defined in terms of spectral and morphometric properties is characterized by its specific range of values for lava viscosity effusion rate and duration of the effusion process for our data set we report lava viscosities between about 10 2 and 10 8 pas effusion rates between 25 and 600 m 3 s 1 and durations of the effusion process between three weeks and 18 years lava viscosity decreases with increasing r 415 r 750 spectral ratio and thus tio2 content however the correlation is not strong implying an important influence of further parameters like effusion temperature on lava viscosity

understanding the lunar surface and space moon interactions the surface of the moon is a critical boundary that shapes our understanding of the moon as a whole all geologic mapping and remote sensing techniques utilize only the outermost portion of the moon before leaving the moon for study in our laboratories all lunar samples that have been studied existed at or very near the surface with the exception of the deeply probing geophysical techniques our understanding of the interior of the moon is derived from surficial but not superficial information coupled with boundary of the lunar crust it is the lower boundary layer of the tenuous lunar atmosphere and constitutes both a source and a sink for atmospheric gases the surface is also where the moon interacts with the space environment causing changes in the physical nature of lunar materials and provides a laboratory for the study of processes that occur on all airless bodies the data obtained remotely by the galileo clementine and lunar prospector missions as well as data derived from lunar meteorites have resulted in major changes to our understanding of global distributions of chemistry and rocks this chapter summarizes the current understanding of this critical interface the surface of the moon in its role as the lower boundary of the lunar atmosphere the upper boundary of the crust and the window through which we view through remote sensing the composition of the crust and the history of the moon in this post lunar prospector time the view of the moon has changed lending new perspectives to lunar samples and lunar processes but the new view will likely remain in flux as we continue to digest the results from these recent space missions and move forward to a new era of lunar exploration despite the freshness of our perspective this is an important moment to capture

weathering in the lake baikal watershed during the kazantsevo eemian interglacial evidence from the lacustrine clay record the clay mineralogical record of a piston core recovered on an elevated plateau in the northern basin of lake baikal has been investigated for the kazantsevo interglacial period i e eemian s s equivalent in northern europe the age model as inferred from palaeomagnetic intensity suggests that this stage spans ca 128 to 117 kyr bp relative clay mineral abundances and clay mineral ratios are used to reconstruct the weathering conditions within the baikal watershed at a sub millennial resolution and suggest that the clay record is highly variable a bimodal clay data distribution is in agreement with different clay sources and or formation between the studied glacial and interglacial periods high amounts of smectites in the taz glacial samples 128 7 136 4 kyr bp may be explained by an additional source of neoformed smectites during the glacial stage in addition to the classically used smectite illite ratio the mineralogical results are integrated by the calculation of a hydrolysis index that takes into account the abundance of all clay species and their sensitivity to chemical weathering a principal components analysis pca of the baikal clay minerals allows the comparison of the clay parameters with regard to weathering conditions clay data are further compared i with diatom and pollen profiles ii with pollen based quantitative reconstructions for the same core material and iii with other climate reconstructions for the lake baikal region and siberia several features of our record are highlighted here during the early period of the kazantsevo interglacial 128 4 125 2 kyr bp weathering processes remain controlled by physical reworking for more than 2 kyr after the initial transition from cold to warm conditions inception of chemical weathering starts only after ca 125 kyr bp a period coincident with the warmest conditions according to both the pollen record and by the strongest chernozem development in siberian soils within the interglacial interval the hydrolysis index displays a two step increase punctuated by a minimum value ca 122 kyr bp the increasing but irregular trend persists after the transition from the kazantsevo interglacial to the zyryanka glacial similar to 117 kyr bp peak chemical weathering as inferred by clay changes lags the interglacial glacial transition by at least 2 kyr this suggests that pedogenesis remains active after the interval of surface stabilization lake baikal clay minerals trace the nature of the main weathering conditions within the watershed we note any increase in physical weathering is rapidly recorded in sedimentary clay assemblages but the mineral imprint to chemical weathering changes is more gradual lagging reconstructed climate conditions over the lake by ca 2 kyr 0 2007 elsevier b v all rights reserved

climate changes in the qaidam basin in nw china over the past 40 kyr abstract little is known about the climate and environmental changes that have occurred in the extremely arid regions of china since mis marine isotope stage 3 59 29 cal kyr bp when most regions in northwestern china and the tibetan plateau featured warm and humid conditions in this paper we present a record of the climate changes in the qaidam basin in arid northwestern china over the past 40 kyr based on the mineralogy of a 35 m long sediment core recovered from qarhan salt lake our results show that the lake was a saline or hyper saline lake saturated with respect to gypsum between 40 and 33 cal kyr bp beginning at 33 cal kyr bp evaporite formation was dominated by halite precipitation indicating that the lake salinity had increased extensively and that the climate became drier during 33 24 5 cal kyr bp the lake salinity then increased continuously resulting in the appearance of bischofite between 24 5 and 14 6 cal kyr bp the disappearance of bischofite and the increase in gypsum indicate that the salinity of the water decreased slightly between 14 6 and 8 3cal kyr bp however during the last 8300 years the lake has dried up and is now a playa generally the climate was wet in late mis 3 arid in mis 2 29 11 7 cal kyr bp and hyperarid in the holocene the relatively humid conditions may have resulted from weak evaporation caused by the relatively low insolation and intense ice albedo feedback in late mis 3 the decreased insolation and dramatically increased eurasian ice volume in mis 2 may have led to limited precipitation which resulted in persistent dry climate conditions in the qaidam basin in the holocene the reduction in ice volume reduced the albedo and this change in conjunction with increased insolation may have led to evaporation exceeding local precipitation resulting in hyperarid climate conditions in the qaidam basin

astronomical forcing of the east asian monsoon mirrored by the composition of pliocene south china sea sediments abstract high precision major and minor element records of pliocene core intervals from ocean drilling program odp site 1145 located in the northern part of the south china sea were generated at a 5 cm approximately 2 kyr resolution from the geochemical data distinct proxies those indicating changes in detrital matter provenance as well as those indicating productivity variations could be derived both the terrigenous input to the northern south china sea k si and variations in productivity ba al show a response to insolation forced monsoon variability while the fluvial input k si responds to changes in the summer monsoon productivity increases as documented by ba enrichments seem to reflect variations in winter monsoon intensity a stronger winter monsoon may have increased nutrient availability via dust input and or upwelling phenomena according to our geochemical proxy records summer and winter monsoons are approximately 180 out of phase this may imply forcing of the winter monsoon through southern hemisphere summer insolation maxima the k si ratio shows a linear correlation with the la90 1 0 5 northern hemisphere summer insolation record and has therefore been used to create an astronomical timescale for the investigated sediments of odp site 1145 carbonate contents and corresponding color reflectances display 41 and 100 kyr cycles we propose that these do not reflect glacial cycles but are rather the result of an interference signal of dilution by fluvial and eolian terrigenous material and carbonate production burial flux a sudden onset of gradual changes in sediment composition occurs after 3 0 ma this is also documented by an increase in sedimentation rates and may be caused by enhanced fluvial input from the pearl river due to intensified weathering rates on the asian continent this may be linked to tectonic processes around the himalayan tibetan complex and its consequences regarding land sea heating and atmospheric circulation

impacts into porous asteroids abstract many small bodies in the solar system have bulk density well below the solid density of the constituent mineral grains in their meteorite counterparts those low density bodies undoubtedly have significant porosity which is a key factor that affects the formation of impact craters this paper summarizes the results of lab experiments in which materials with porosity ranging from 43 to 96 were impacted at 1800 m s the experiments were performed on a geotechnical centrifuge in order to reproduce the lithostatic overburden stress and ejecta ballistics that occur in large scale cratering events on asteroids or planetary satellites experiments performed at various accelerations up to 514g simulate the outcomes of impacts at size scales up to several tens of km in diameter our experiments show that an impact into a highly porous cohesionless material generates a large ovoid shaped cavity due to crushing by the outgoing shock the cavity opens up to form a transient crater that grows until the material flow is arrested by gravity the cavity then collapses to form the final crater during collapse finely crushed material that lines the cavity wall is carried down and collected in a localized region below the final crater floor at large simulated sizes high accelerations most of the crater volume is formed by compaction because growth of the transient crater is quickly arrested nearly all ejected material falls back into the crater leaving the crater without an ejecta blanket we find that such compaction cratering and suppression of the ejecta blankets occur for large craters on porous bodies when the ratio of the lithostatic stress at one crater depth to the crush strength of the target exceeds 0 005 the results are used to identify small solar system bodies on which compaction cratering likely occurs a model is developed that gives the crater size and ejecta mass that would result for a specified impact into a porous object

explosive volcanic eruptions ix the transition between hawaiian style lava fountaining and strombolian explosive activity the commonest eruption styles of basaltic volcanoes involve hawaiian lava fountaining or intermittent strombolian explosions we investigate the ways in which magma rise speed at depth magma volatile content and magma viscosity control which of these eruption styles takes place we develop a model of the degree of coalescence between gas bubbles in the magma which allows us to simulate the transition between the two extreme styles of activity we find that magma rise speed is the most important factor causing the transition with gas content and viscosity also influencing the rise speed at which the transition occurs counter to intuitive expectations a decrease in gas content does not cause a transition from hawaiian to strombolian activity but instead causes a transition to passive effusion of vesicular lava rather a change from hawaiian to strombolian style requires a significant reduction in magma rise speed

age constraints on the late quaternary evolution of qinghai lake tibetan plateau dating and geomorphology of shoreline features in the qinghai lake basin of northwestern china suggest that contrary to previous interpretations the lake likely did not reach levels 66 140 m above modern within the past 90 000 yr maximum highstands of 20 66 m above modern probably date to marine isotope stage mis 5 mis 3 highstands are undated and uncertain but may have been at or below post glacial highs the lake probably reached 3202 3206 m 8 12 m during the early holocene but stayed below 3202 m after 8 4 ka this shoreline history implies significantly different hydrologic balances in the qinghai lake basin before 90 ka and after 45 ka possibly the result of a more expansive asian monsoon in mis 5

the constitution and structure of the lunar interior the current state of understanding of the lunar interior is the sum of nearly four decades of work and a range of exploration programs spanning that same time period missions of the 1960s including the rangers surveyors and lunar orbiters as well as earth based telescopic studies laid the groundwork for the apollo program and provided a basic understanding of the surface its stratigraphy and chronology through a combination of remote sensing surface exploration and sample return the apollo missions provided a general picture of the lunar interior and spawned the concept of the lunar magma ocean in particular the discovery of anorthite clasts in the returned samples led to the view that a large portion of the moon was initially molten and that crystallization of this magma ocean gave rise to mafic cumulates that make up the mantle and plagioclase flotation cumulates that make up the crust smith et al 1970 wood et al 1970 this model is now generally accepted and is the framework that unifies our knowledge of the structure and composition of the moon the intention of this chapter is to review the major advances that have been made over the past decade regarding the constitution of the moon s interior much of this new knowledge is a direct result of data acquired from the successful clementine and lunar prospector missions as well as the analysis of new lunar meteorites as will be seen results from these studies have led to many fundamental amendments to the magma ocean model much of what we know from sample analyses has been previously summarized elsewhere and only their most important aspects will be discussed in this chapter the reader is referred to the relevant chapters in the books basaltic volcanism on the terrestrial planets basaltic volcanism study project 1981 the

young lunar volcanic features thermophysical properties and formation abstract irregular mare patches imps are small volcanic features on the lunar nearside with young model ages several formation mechanisms have been proposed including caldera collapse explosive outgassing lava flow inflation pyroclastic eruption and regolith drainage we present new observations of the four largest imps sosigenes ina cauchy 5 and maskelyne using the lunar reconnaissance orbiter lro diviner lunar radiometer diviner and evaluate the formation hypotheses in the context of both previous results and the results presented here we find that the imps have a rock abundance slightly higher than their surrounding terrain comparison of the diviner data with thermal models excludes the possibility of extensive competent rocks within 15 cm of the surface at the imps we also derive the thermal inertia at the four largest imps three appear to have thermal inertias slightly higher than typical regolith due to alteration by nearby craters or mass wasting from surrounding steep slopes but ina has a thermal inertia lower than the surrounding terrain in particular the largest smooth mound in ina is the area with the lowest thermal inertia suggesting that the material on the mound is less consolidated than typical regolith and or contains fewer small rocks

last deglacial and holocene lake level variations of qinghai lake north eastern qinghai tibetan plateau qinghai lake is of significance for paleoclimate research because it lies in a pivotal region that is influenced by both the mid latitude westerlies and the low latitude asian summer monsoon asm most published lake level histories of qinghai lake are interpreted from drill core proxies here we combine geomorphic shoreline investigations with optically stimulated luminescence dating to constrain lake level variations since the last deglacial the results indicate that two periods of highstands occurred during the last deglacial approximate to 16 14 9 and approximate to 12 6 12 2 ka and that lake levels were 6 7 4m higher than at present lake levels dropped abruptly during the younger dryas and were generally low with frequent fluctuations during the early holocene qinghai lake reached its highest holocene level 9 1m higher than modern at approximate to 5 ka and has regressed during the past 2 ka we propose that high lake levels during the last deglacial were due mainly to melting glacial and permafrost waters supplemented by enhanced westerlies precipitation and decreased evaporation during heinrich event 1 approximate to 16 14 9 ka and increased asm rainfall during the bolling allerod warm period approximate to 14 12 ka lake level fluctuations during the holocene were generally in accordance with moisture variations in the marginal monsoon zones of inland china

formation of lunar mare domes along crustal fractures rheologic conditions dimensions of feeder dikes and the role of magma evolution abstract in this study we examine a set of lunar mare domes located in the hortensius milichius t mayer region and in northern mare tranquillitatis with respect to their formation along crustal fractures their rheologic properties the dimensions of their feeder dikes and the importance of magma evolution processes during dome formation many of these domes display elongated summit vents oriented radially with respect to major impact basins and several dome locations are also aligned in these preferential directions analysis of clementine uv vis and lunar prospector gamma ray spectrometer data reveals that the examined mare domes formed from low si basaltic lavas of high feo and low to moderate tio2 content based on their morphometric properties diameter height volume obtained by photoclinometric and shape from shading analysis of telescopic ccd images we derive rheologic quantities lava viscosity during eruption effusion rate duration of the effusion process magma rise speed and the dimensions of the feeder dikes we establish three rheologic groups characterised by specific combinations of rheologic properties and dike dimensions where the most relevant discriminative parameter is the lava viscosity the first group is characterised by 10 4 pa s 10 6 pa s and contains the domes with elongated vents in the milichius t mayer region and two similar domes in northern mare tranquillitatis the second group with 10 2 pa s 10 4 pa s comprises the very low aligned domes in northern mare tranquillitatis and the third group with 10 6 pa s 10 8 pa s the relatively steep domes near hortensius and in the t mayer region the inferred dike dimensions in comparison to lunar crustal thickness data indicate that the source regions of the feeder dikes are situated within the upper crust for six of the domes in northern mare tranquillitatis while they are likely to be located in the lower crust and in the upper mantle for the other examined domes by comparing the time scale of magma ascent with the time scale on which heat is conducted from the magma into the host rock we find evidence that the importance of magma evolution processes during ascent such as cooling and crystallisation increases with lava viscosity we conclude that different degrees of evolution of initially fluid basaltic magma are able to explain the broad range of lava viscosities inferred for the examined mare domes the spectral data reveal that differences in tio2 content may additionally account for the systematic difference in lava viscosity between the two examined lunar regions we show that the described mechanisms are likely to be valid also for other lunar mare domes situated near cauchy and arago regarded for comparison on the other hand we find for the gruithuisen and mairan highland domes that despite their inferred high lava viscosities of 10 8 10 9 pa s no significant magma cooling in the dike occurred during ascent supporting previous findings that the highland domes were formed during a specific phase of non mare volcanism by highly silicic viscous lavas

ebsd microfabric study of pre cambrian deformations recorded in quartz pebbles from the sierra de la demanda n spain abstract we describe a new method for the reorientation of lattice preferred orientation data in the absence of a pre constrained kinematic reference frame the method enables us to present conventional quartz fabric diagrams after measurements taken from rock sections with a general orientation with respect to foliation and lineation a microstructural and electron back scattered diffraction ebsd study of quartz pebbles in early cambrian conglomerates following this method permit us to recognize a variety of fabrics that resulted from syn metamorphic ductile deformation under variable temperatures up to 650 c the likely source area of the conglomerates was a proterozoic basement candidates for source rock correlations include neoproterozoic units similar to those outcropping in the northern iberian massif neoproterozoic medium to high grade metamorphic rocks as those outcropping in sw iberia or a neoarchean to mesoproterozoic concealed basement

weathering and global denudation a negative correlation between sediment yield and weathering history as measured by the chemical alteration cia of the suspended sediment is observed for many of the world s major rivers and other regions of denudation the weathering history is a first order control on the sediment yield of such areas termed equilibrium denudation regions for other areas data scatter with either apparent increases or decreases of sediment yield for given cia values these areas are termed nonequilibrium denudation regions low sediment yields can be attributed to moderated erosion either natural or human induced and or the incorporation of unweathered glacial debris accelerated erosion resulting in high sediment yield is primarily human induced and results from cultivation and other land use each of these effects has a profound influence on global sediment discharge from the continents pre human suspended sediment discharge from the continents is estimated to be 12 6 times 10 15 g yr or about 0 6 the

earth based 12 6 cm wavelength radar mapping of the moon new views of impact melt distribution and mare physical properties abstract we present results of a campaign to map much of the moon s near side using the 12 6 cm radar transmitter at arecibo observatory and receivers at the green bank telescope these data have a single look spatial resolution of about 40 m with final maps averaged to an 80 m four look product to reduce image speckle focused processing is used to obtain this high spatial resolution over the entire region illuminated by the arecibo beam the transmitted signal is circularly polarized and we receive reflections in both senses of circular polarization measurements of receiver thermal noise during periods with no lunar echoes allow well calibrated estimates of the circular polarization ratio cpr and the four element stokes vector radiometric calibration to values of the backscatter coefficient is ongoing radar backscatter data for the moon provide information on regolith dielectric and physical properties with particular sensitivity to ilmenite content and surface or buried rocks with diameter of about one tenth the radar wavelength and larger average 12 6 cm circular polarization ratio cpr values for low to moderate tio 2 mare basalt deposits are similar to those of rough terrestrial lava flows we attribute these high values to abundant few centimeter diameter rocks from small impacts and a significant component of subsurface volume scattering an outflow deposit inferred to be impact melt from glushko crater has cpr values near unity at 12 6 cm and 70 cm wavelengths and thus a very rugged near surface structure at the decimeter to meter scale this deposit does not show radar brightness variations consistent with levees or channels and appears to nearly overtop a massif suggesting very rapid emplacement deposits of similar morphology and or radar brightness are noted for craters such as pythagoras rutherfurd theophilus and aristillus images of the north pole show that despite recording the deposition of orientale material byrd and peary craters do not have dense patterns of radar bright ejecta from small craters on their floors such patterns in amundsen crater near the south pole were interpreted as diagnostic of abundant impact melt so the fraction of orientale derived melt in the north polar smooth plains 1000 km farther from the basin center is inferred to be much lower

magnetostratigraphy and sedimentologically derived geochronology of the quaternary lacustrine deposits of a 3000 m thick sequence in the central qaidam basin western china the qaidam basin is a large basin in western china where the thickness of quaternary deposits has a range of 2000 3000 m at its subsiding depocentre this study investigated the chronology of the quaternary deposits including palaeomagnetics biostratigraphic correlation rates of sediment accumulation seismic reflection surveys and electrical property correlations the results give a full interpretation of ages for the sequence from bottom to top the oldest sequence age was defined by the first appearance of microlimnocythere sinensis huang and was placed in the gauss epoch estimated at approximately 3 ma by extrapolation of accumulation rates the m g boundary occurs at the base of the third fossil zone of ostracoda the first appearance of qinghaicypris crassa huang or at the marker layer k 10 of the electrical log in the sebei anticline area considered here to be 2 48 ma the olduvai event in the fifth fossil zone spanning electrical layers k 4 and k 3 in the sebei area occurs at reflection layer t 0 1 of seismic stratigraphy which could be stratigraphically correlated in the whole basin the boundary of early middle pleistocene such as the brunhes and matsuyama b m boundary falls within the eighth fossil zone and coincides with electrical marker k 0 1 two boundaries corresponding to middle late pleistocene and pleistocene holocene occur at the bases of the 11th and 12th biozones respectively neither of which can be correlated with seismic stratigraphy and electrical logs in the basin due to the lack of widely distributed lacustrine deposits since the middle pleistocene the ages of the boundaries can be tested by deposition rates of different facies derived from the varves and synchronous deposits as a result geochronological sequences of subsurface stratigraphy could be established within a basin wide area on the synchronology of seismic reflectors and correlations of electrical logs as well as biozones c 1998 elsevier science b v all rights reserved

eruption of magmatic foams on the moon formation in the waning stages of dike emplacement events as an explanation of irregular mare patches abstract volcanic eruptions on the moon take place in conditions of low gravity and negligible atmospheric pressure very different from those on earth these differences lead to characteristic lunar versions of hawaiian and strombolian explosive activity and to the production of unusual eruption products neither predicted nor observed on earth in the terminal stages of eruptions these include the unusual mounds and rough hummocky blocky floors of some small shield summit pit crater floors elongate depressions and mare flows similar to those named irregular mare patches imps by braden et al 2014 we examine the ascent and eruption of magma in the waning stages of the eruptive process in small shield summit pit crater floors and show that many imp characteristics can be plausibly explained by basaltic magma behavior as the rise rate of the ascending magma slows to zero volatiles exsolve in the dike and lava lake to form a very vesicular foam and the dike begins to close stresses in the very vesicular and porous lava lake crust produce fractures through which the foam extrudes at a rate determined by its non newtonian rheology waning stage extrusion of viscous magmatic foams to the surface produces convex mounds whose physical properties inhibit typical impact crater formation and regolith development creating an artificially young crater retention age this mechanism for the production and extrusion of very vesicular magmatic foams is also applicable to waning stage dike closure associated with pit craters atop dikes and fissure eruptions in the lunar maria providing an explanation for many irregular mare patches this mechanism implies that imps and associated mare structures small shields pit craters and fissure flows formed synchronously billions of years ago in contrast to very young ages less than 100 million years proposed for imps by some workers

late pleistocene paleoclimatic history documented by an oxygen isotope record from carbonate sediments in qarhan salt lake ne qinghai tibetan plateau late pleistocene paleoclimatic variability on the northeastern qinghai tibetan plateau ne qtp was reconstructed using a chronology based on ams 14 c and 230 th dating results and a stable oxygen isotopic record these are derived from lake carbonates in a 102 m long qarhan sediment core isl1a collected from the eastern qaidam basin previous research indicates that the d 18 o values of lacustrine carbonates are mainly controlled by the isotopic composition of lake water which in turn is a function of regional p e balance and the proportion of precipitation that is monsoon derived on the ne qtp modern isotopic observations indicate that the d 18 o values of lake carbonates in hyper arid qaidam basin are more positive during the warm and wet period due to strong evaporation and continental effect in this basin the positive d 18 o values in the arid region indicate drier climatic conditions based on this interpretation and

scavenged excess aluminum and its relationship to bulk titanium in biogenic sediment from the central equatorial pacific ocean we present results from chemical analyses of al and ti in surface sediment sampled along two cross equator latitudinal transects at 135w and 140w in the central equatorial pacific ocean although traditionally both al and ti are considered to reside exclusively within terrigenous phases in marine sediment these sediments present extremely high al ti ratios that are several times that of average shale and other potential crustal sources a sharp maximum in al ti is observed slightly south of the equator where sedimentary bulk accumulation rate bar is also highest reflecting elevated productivity in the overlying water caused by surface water divergence bulk al ti decreases sharply away 2 latitude to near crustal values at 4 north and south the latitudinal profiles of al ti are entirely unrelated to the concentration of the biogenic components as well as to the absolute accumulation of al and ti these results indicate the presence of a significant scavenged component of al sourced directly from seawater during particle settling the data from the two transects analytically and oceanographically confirms our earlier work that was based on the single 135w transect calculations of alexcess indicate that the highest al ti ratios correspond to 50 of the total al being unsupported by the small amount of terrigenous phases present these results are consistent with previous and ongoing studies of biogenic sediment suspended particulate matter and sediment trap material quantitative use of al as an index of terrigenous material may therefore lead to an overestimation by a factor of two of the true terrigenous load in marine sediment sedimentary rock and settling particles because bulk al ti appears to respond to sedimentary bar which in biogenic regimes is linked to surface water productivity downcore records of al ti in biogenic sediment may track productivity changes through time such al ti proxy records may be applicable in sediment of all ages unlike radionuclide tracers which are limited by radioactive decay to use over the past hundreds of kyr

geological characterization of the ina shield volcano summit pit crater on the moon evidence for extrusion of waning stage lava lake magmatic foams and anomalously young crater retention ages ina a distinctive 2 3 km d shaped depression is composed of unusual bulbous shaped mounds surrounded by optically immature hummocky blocky floor units the crisp appearance optical immaturity and low number of superposed impact craters combine to strongly suggest a geologically recent formation for ina but the specific formation mechanism remains controversial we reconfirm that ina is a summit pit crater vent on a small shield volcano 3 5 billion years old following detailed characterization we interpret the range of ina characteristics to be consistent with a two component model of origin during the waning stages of summit pit eruption activities the ina pit crater floor is interpreted to be dominated by the products of late stage low rise rate magmatic dike emplacement magma in the dike underwent significant shallow degassing and vesicle formation followed by continued degassing below the solidified and highly microvesicular and macrovesicular lava lake crust resulting in cracking of the crust and extrusion of gas rich magmatic foams onto the lava lake crust to form the mounds these unique substrate characteristics highly porous aerogel like foam mounds and floor terrains with large vesicles and void space exert important effects on subsequent impact crater characteristics and populations influencing 1 optical maturation processes 2 regolith development and 3 landscape evolution by modifying the nature and evolution of superposed impact craters and thus producing anomalously young crater retention ages accounting for these effects results in a shift of crater size frequency distribution model ages from

sr isotope and major ion compositional evidence for formation of qarhan salt lake western china abstract qarhan salt lake qsl is the largest potash brine deposit in the continental qaidam basin qb of western china the origins of the qarhan brines whether from migration of qaidam mega paleolakes paleoriver capture or mixing of modern river water and ca cl spring water are controversial details about the origin hydrothermal diagenetic or both of the ca cl inflow waters entering qsl in the qb are unclear here we show from the strontium sr isotope ratios of river waters intercrystalline brines spring waters halite gypsum and corbicula shells from qarhan playa that 87 sr 86 sr increases from bieletan western qsl to huobuxun eastern qsl this trend verifies that river water spring water mixing has been operating at qsl for the past 50 000 years contributions of ca cl inflow waters to the qb have profoundly influenced the brine evolution and mineralogy of salt deposits mixing between low sr 2 concentration low 87 sr 86 sr value of river waters and high sr 2 concentration high 87 sr 86 sr value of ca cl spring inflow waters has produced various intercrystalline brines and salt deposits at qsl ca cl inflow waters and brines are enriched in sr 2 and ca 2 and depleted in mg 2 and so 4 2 these characteristics suggest brine sedimentary rock silicate interactions at burial diagenetic or hydrothermal conditions ca cl inflow waters and brines have a similar sr isotopic range as oilfield brines and celestite deposits in the qb which also suggests a diagenetic hydrothermal origin ca cl brines discharge as springs or seeps along fault zones in the qb they are interpreted to reach the surface of the northern margin of qarhan playa by topographically driven circulation

geochemical factors controlling accumulation of major and trace elements in greenland coastal and fjord sediments the major al ti ca mg fe mn si and trace element cd cr cu hg li ni pb v zn concentrations in surficial 63 m and 63 m and have accumulated at the same rate as other detrital clastic material provenance and glaciomarine deposition are the main factors controlling the abundance and distribution of the major and trace elements the chemical composition reflects the mineralogical differences in the provenance of glacial marine material deposited by water and ice adjacent to greenland the main source of the sediments enriched in ti fe mg cr cu ni and v appears to be material derived from the volcanic rocks of the mesozoic tertiary provinces of greenland by glacial erosion

crater degradation on the lunar maria topographic diffusion and the rate of erosion on the moon landscape evolution on the moon is dominated by impact cratering in the post maria period in this study we mapped 800 m to 5 km diameter craters on 30 of the lunar maria and extracted their topographic profiles from digital terrain models created using the kaguya terrain camera we then characterized the degradation of these craters using a topographic diffusion model because craters have a well understood initial morphometry these data provide insight into erosion on the moon and the topographic diffusivity of the lunar surface as a function of time the average diffusivity we calculate over the past 3 ga is 5 5 m2 myr with this diffusivity after 3 ga a 1 km diameter crater is reduced to approximately 52 of its initial depth and a 300 m diameter crater is reduced to only 7 of its initial depth and craters smaller than 200 300 m are degraded beyond recognition our results also allow estimation of the age of individual craters on the basis of their degradation state provide a constraint on the age of mare units and enable modeling of how lunar terrain evolves as a function of its topography

moderate chemical weathering of subtropical taiwan constraints from solid phase geochemistry of sediments and sedimentary rocks abstract the well known earthquake and storm triggered extremely high physical weathering rate in taiwan is consistent with present geochemical studies of sediments from different subenvironments offshore coastal river and lake and sedimentary rocks of different geological ages indicating a moderate chemical weathering condition major and trace element concentrations normalized to the average upper crust of yangtze craton show that the sediments and the average composition of sedimentary rocks of taiwan are depleted in ca mg na and sr enriched in rb and zr and unchanged with respect to k indicating their moderately altered nature the mean chemical index of alteration cia 71 75 and plagioclase index of alteration pia 81 86 values of coastal and offshore sediments reveal the sediments derivation from sedimentary rocks by moderate silicate chemical weathering processes the mean cia value 62 of sedimentary rocks of taiwan is similar to that for chinese sediment 61 further confirming

a 94 10 ka pollen record of vegetation change in qaidam basin northeastern tibetan plateau drill core isl1a was obtained from the qarhan salt lake in central eastern qaidam basin northeastern tibetan plateau ne tp fossil pollen and the lithology of the core sediment were analyzed in conjunction with ams c 14 and th 230 dating the results indicated that artemisia and chenopodiaceae dominated the steppe desert steppe vegetation developed around the lake between 94 and 51 2 ka corresponding with the organic rich silty clay deposited in the core sediments pediastrum continuously appeared in the core sediments between 94 and 51 2 ka indicating freshwater to oligohaline conditions of the paleo qarhan lake during the late marine isotope stage mis 5 mis 4 and early mis 3 during the 51 2 to 32 5 ka period ephedra dominated shrub desert vegetation expanded in the basin while pediastrum disappeared in the core sediments the core sediments consisted of interbedded layers of halite silt and clay rich halite between 51 2 and 32 5 ka signifying a shift toward drier hydrologic conditions thus the paleo qarhan lake experienced periods of desiccation and shallow water levels artemisia and chenopodiaceae dominated steppe desert steppe vegetation appeared again from 32 5 to 253 ka with clay rich sediments in the core thereby suggesting an increase of runoff from the lake under relatively wetter climatic conditions since 253 ka however pollen concentrations declined corresponding with the amount of halite deposited in the core sediment and suggesting a cold dry climatic condition during mis2 our findings have important implications for understanding complex regional vegetation and climatic responses to large scale forcings in the qaidam basin c 2015 elsevier b v all rights reserved

controls on lunar basaltic volcanic eruption structure and morphology gas release patterns in sequential eruption phases assessment of mare basalt gas release patterns during individual eruptions provides the basis for predicting the effect of vesiculation processes on the structure and morphology of associated features we subdivide typical lunar eruptions into four phases phase 1 dike penetrates to the surface transient gas release phase phase 2 dike base still rising high flux hawaiian eruptive phase phase 3 dike equilibration lower flux hawaiian to strombolian transition phase phase 4 dike closing strombolian vesicular flow phase we show how these four phases of mare basalt volatile release together with total dike volumes initial magma volatile content vent configuration and magma discharge rate can help relate the wide range of apparently disparate lunar volcanic features pyroclastic mantles small shield volcanoes compound flow fields sinuous rilles long lava flows pyroclastic cones summit pit craters irregular mare patches imps and ring moat dome structures rmdss to a common set of eruption processes

ina pit crater on the moon extrusion of waning stage lava lake magmatic foam results in extremely young crater retention ages the enigmatic ina feature on the moon was recently interpreted to represent extrusive basaltic volcanic activity within the past 100 m y of lunar history an extremely young age for volcanism on the moon ina is a 2 3 km d shaped depression that consists of a host of unusual bleb like mounds surrounded by a relatively optically fresh hummocky and blocky floor documentation of magmatic volcanic processes from shield volcano summit pit craters in hawai i and new insights into shield building and dike evolution processes on the moon provide important perspectives on the origin of ina we show that the size location morphology topography and optical maturity of ina are consistent with an origin as a subsided summit pit crater lava lake on top of a broad 22 km diameter 3 5 b y old shield volcano new theoretical treatments of lunar shield building magmatic dike events predict that waning stage summit activity was characterized by the production of magmatic foam in the dike and lake the final stages of dike stress relaxation and closure cause the magmatic foam to extrude to the surface through cracks in the lava lake crust to produce the mounds the high porosity of the extruded foams 75 altered the nature of subsequent impact craters the aerogel effect causing them to be significantly smaller in diameter which could bias the crater derived model ages accounting for this effect allows for significantly older model ages to 3 5 b y contemporaneous with the underlying shield volcano thus extremely young volcanic eruptions are not required to explain the unusual nature of ina

deep generation of magmatic gas on the moon and implications for pyroclastic eruptions 1 lunar pyroclastic beads are interpreted to represent primitive magmas derived from great depths and rapidly erupted to the surface in explosive events however a detailed mechanism for gas generation at great depth and rapid magma transport to the surface has not yet been described furthermore the pyroclastic beads are not petrogenetically related to basalts erupted near the sampling sites we propose a model in which these conundrums are resolved through gas build up in a low pressure micro environment near the tip of a magma filled crack dike propagating rapidly from the magma source depth to the surface the gas rich region consists of a free gas cavity overlying a foam extending vertically for 20 km eruption of the foam results in the widespread emplacement of unfractionated pyroclastic beads subsequent ascent of the underlying gas free picritic magma is unlikely to occur perhaps accounting for the lack of sampled eruptive equivalents

an assessment and comparison of 230th and ams 14c ages for lacustrine sediments from qarhan salt lake area in arid western china the age framework of qarhan salt lake in arid western china is still controversial due in part to 1 age discrepancy between conventional 14c and 230th dating results and 2 no ams 14c ages of organic carbon from drilling cores in qarhan salt lake were reported until now in order to discuss these chronological problems upper 54 50 m lacustrine sediments from a drilling core isl1a recovered from qarhan salt lake were dated based on 230th and ams 14c dating techniques results show that 1 ams 14c ages of total organic carbon toc from 4 65 to 30 29 m are almost in stratigraphic order and consistent with 230th ages of halite in the corresponding layers 2 ams 14c ages of toc from 30 29 to 54 50 m are younger with increasing depth this phenomenon was also found in shell bar in the study area suggesting that ams 14c ages from upper 30 29 m are more reliable while those from lower 24 21 m in isl1a may be underestimated 3 230th ages of halite from lower 24 m lacustrine sediments are obviously older than ams 14c ages of toc in the corresponding layers which results into different age framework of salt lake sediments in qarhan salt lake 4 if extrapolating these reliable ams 14c ages in isl1a similar age framework with 230th ages in this core confirms that 230th ages are much close to the true ages of these sediments which suggests that the forming timing of the bottom salt layer is 50 ka

two unique weathering regimes in the changjiang and huanghe drainage basins geochemical evidence from river sediments the present research reconstructs the histories of chemical weathering in the drainage basins of the changjiang and huanghe based on the chemical compositions of the river sediments the silicate weathering of the changjiang basin is strong and naand ca silicate minerals are considerably dissolved while other silicate minerals are less attacked in comparison the huanghe basin is characterized by very weak silicate weathering and the weathering degree corresponds well with that of the loess which is the predominant source of the huanghe sediment overall the changjiang and huanghe basins constitute a consistent weathering spectrum from the early to intermediate stage the similarity of chemical compositions between upper continental crust and the huanghe sediments as well as the low degree of chemical weathering in the huanghe basin imply that the river sediments can be considered to be the representative of ucc and are suitable for studying the evolution of continental crust our observations indicate that climate is the predominant factor controlling silicate weathering in both river basins while controls by source rocks and relief are subordinate highly erosive river basins such as the huanghe produce poorly weathered materials which casts doubt on the idea that strong physical weathering naturally contributes much to chemical weathering differences in silicate weathering processes between the changjiang and huanghe basins may provide more constraints in estimating atmospheric co2 budget in china d 2003 elsevier b v all rights reserved

a new lunar digital elevation model from the lunar orbiter laser altimeter and selene terrain camera abstract we present an improved lunar digital elevation model dem covering latitudes within 60 at a horizontal resolution of 512 pixels per degree 60 m at the equator and a typical vertical accuracy 3 to 4 m this dem is constructed from 4 5 10 9 geodetically accurate topographic heights from the lunar orbiter laser altimeter lola onboard the lunar reconnaissance orbiter to which we co registered 43 200 stereo derived dems each 1 1 from the selene terrain camera tc 1010 pixels total after co registration approximately 90 of the tc dems show root mean square vertical residuals with the lola data of

lunar mare volcanism stratigraphy eruption conditions and the evolution of secondary crusts abstract lunar mare basalt deposits cover 17 of the lunar surface occur preferentially in topographic lows on the nearside and have a total volume estimated at 1 107 km3 analysis of returned samples and photogeologic and remote sensing studies shows that mare volcanism began prior to the end of heavy bombardment the period of cryptomare formation in pre nectarian times and continued until the copernican period a total duration approaching 3 5 4 ga stratigraphic analyses show that the flux was not constant but peaked in early lunar history during the imbrian period which spans the period 3 85 3 2 ga average volcanic output rate during this peak period was about 10 2 km 3 a very low relative to the present global terrestrial volcanic output rate and comparable to the present local output rates for individual volcanoes such as vesuvius and kilauea hawaii volcanic landforms indicate that many eruptions were of high volume and long duration some eruptions associated with sinuous rules may have lasted of the order of a year and emplaced 103 km3 of lava representing the equivalent in one year of about 70 000 years at the average flux shallow magma chambers were uncommon the nearsidefarside mare deposit asymmetry can be readily explained by differences in crustal thickness magma ascending from the mantle or from a buoyancy trap at the base of the crust should preferentially extrude to the surface on the nearside but should generally stall and cool in dikes in the farside crust extruding only in the deepest basins the occurrence of farside maria within craters whose diameter is generally near to or less than the thickness of the crust may be accounted for by the difference between local and regional compensation dikes that establish pathways to the surface on the nearside should have very high volumes comparable to the volumes associated with many observed flows and sinuous rilles an abundance of dikes should exist in the lower crust of the moon many more than those feeding surface eruptions the upper limit is 37 50 of the crust by volume the presence and abundance of such dike swarms have important implications for the interpretation of the average composition of the lunar crust and the composition of basin and crater ejecta the interplay between thermal contraction and differentiation leads to net cooling and ultimate contraction of the outer portions of the moon resulting in a regional horizontal compressive stress acting on the lunar crust in addition overall cooling and deepening of sources require the production of ever larger volumes of magma in order to reach the surface with time stresses became high enough so that few dikes could open to the surface causing eruptive activity to be severely diminished in the eratosthenian and perhaps to cease in the copernican period lower stress levels are required to terminate eruptive activity on the lunar farside consistent with the imbrian age of the farside maria and the nearside location of the youngest maria lunar mare deposits provide an example of the transition from primary crusts to secondary crusts and illustrate the significance of several factors in the evolution of secondary crusts such as crustal density variations in crustal thickness presence of impact basins state and magnitude of stress in the lithosphere and general thermal evolution these factors are also responsible for the extremely low volcanic flux even during periods of peak extrusion

late pleistocene evolution of salt lakes in the qaidam basin qinghai province china abstract the qaidam basin is a tectonically controlled depression at 2700 m altitude on the northern margin of the qinghai xizang tibet plateau rimmed by the high aljun qilian ranges to the north and kunlun peaks to the south rising above 5000 m the basin floor experiences hyper arid conditions with evaporation precipitation ratios exceeding 100 1 periglacial and glacial conditions prevail on montane peaks with permafrost above 3800 m on the basin floor small waterbodies lie on extensive halite salt flats on the largest the qarhan salt flat 5800 km2 in extent the small lakes dabuxun and taijinier represent contracted remnants of a once expansive water body throughout neogene time a succession of clastic sediments indicates lake depo centre migration from nw to se towards late pliocene evaporitic conditions developed with formation of gypsum halite celestite mirabilite and bloedite continued deformation through pleistocene time has developed a series of nw se trending domes and troughs this setting has continued to exert a controlling influence on basin and brine evolution with progressive development through sulfate to chloride brines as dry conditions intensified in late pleistocene expanded lake conditions qarhan mega lake corresponding to near the 2800 m contour indicate the existence of past climates much more humid than those of today a drilling program has defined the lateral and vertical extent of evaporitic halite deposits freshwater clastics and shell deposits which predate the halite phase indicate humid lacustral conditions until after 40 000 30 000 yr b p desiccation from about 25 000 yr until about 9000 yr b p resulted in deposition of halite to 60 m thick with thin parting muds representing brief returns to more humid environments high lake shorelines with aragonitic ooids surrounding the dry playa kunteyi and high level ostracod rich beach and near shore deposits on xiao qaidam attest to the presence of expanded late pleistocene lacustral conditions on lakes other than qarhan preceding the final evaporite stage clastic sediments associated with the halite are dominated by loessial silts equivalent to the late pleistocene malan deposits of central china simultaneous halite and loess deposition reflect the dry conditions that developed in the qaidam basin during the latter part of the last glaciation and which have persisted ever since the final evolution of brines has resulted in development of extensive potassium rich brines and salts with the mineral carnallite providing the basis for a large potash extraction industry near golmud the hydrologic history documented by the analyses of lake sediments reflects the interaction of tectonic deformation and climatic change in the development of brines to the potash stage

fluctuations in surface height of active lava lakes during 1972 1974 mauna ulu eruption kilauea volcano hawaii an active lava lake is one that forms directly on top of a magma column as opposed to an inactive one formed by passive ponding of lava within a preexisting crater two active lava lakes operating within summit craters of newly constructed volcanic shields at mauna ulu and alae were the longest lived of any observed in a hawaiian rift zone to date small scale fluctuations a few to 20 m in the height of lake surfaces are typically associated with degassing gas piston activity larger fluctuations as great as 200 m reflect major changes in eruptive activity measurements of surface height fluctuations of mauna ulu lake show gross positive correlation with variation in summit tilt which in turn reflects the inflation deflation state of kilauea s summit magma reservoir a more tenuous conclusion is that a sympathetic variation possibly exists between surface heights of the mauna ulu and alae lakes collectively these observations 1 require the existence of a fully engorged connected open and hydraulically efficient magma conduit system linking the summit reservoir with the lava lakes 2 provide additional evidence for the postulated regime of quasi steady state magma transfer that characterized much of the eruption 3 imply that fluctuations in lake surface reflect variation in magma supply rate to the reservoir and or outflow rate from the mauna ulu alae vents and 4 suggest undetected episodes of magma intrusion or storage in kilauea s east rift zone during 1973

diversity of basaltic lunar volcanism associated with buried impact structures implications for intrusive and extrusive events abstract relatively denser basalt infilling and the upward displacement of the crust mantle interface are thought to be contributing factors for the quasi circular mass anomalies for buried impact craters in the lunar maria imagery and gravity observations from the lunar reconnaissance orbiter lro and dual gravity recovery and interior laboratory grail missions have identified 10 partially or fully buried impact structures where diversity of observable basaltic mare volcanism exists with a detailed investigation of the characteristics of associated volcanic landforms we describe their spatial distribution relationship with respect to the subsurface tectonic structure of complex impact craters and propose possible models for the igneous processes which may take advantage of crater related zones of weakness and enable magmas to reach the surface we conclude that the lunar crust having been fractured and reworked extensively by cratering facilitates substance and energy exchange between different lunar systems an effect modulated by tectonic activities both at global and regional scales in addition we propose that the intrusion caused contribution to gravity anomalies should be considered in future studies although this is commonly obscured by other physical factors such as mantle uplift and basalt load

constraints on the depth and variability of the lunar regolith knowledge of regolith depth structure is important for a variety of studies of the moon and other bodies such as mercury and asteroids lunar regolith depths have been estimated using morphological techniques i e quaide and oberbeck 1968 shoemaker and morris 1969 crater counting techniques shoemaker et al 1969 and seismic studies i e watkins and kovach 1973 cooper et al 1974 these diverse methods provide good first order estimates of regolith depths across large distances tens to hundreds of kilometers but may not clearly elucidate the variability of regolith depth locally 100 m to km scale in order to better constrain the regional average depth and local variability of the regolith we investigate several techniques first we find that the apparent equilibrium diameter of a crater population increases with an increasing solar incidence angle and this affects the inferred regolith depth by increasing the range of predicted depths from 7 15 m depth at 100 m equilibrium diameter to 8 40 m at 300 m equilibrium diameter second we examine the frequency and distribution of blocky craters in selected lunar mare areas and find a range of regolith depths 8 31 m that compares favorably with results from the equilibrium diameter method 8 33 m for areas of similar age 2 5 billion years finally we examine the utility of using clementine optical maturity parameter images lucey et al 2000 to determine regolith depth the resolution of clementine images 100 m pixel prohibits determination of absolute depths but this method has the potential to give relative depths and if higher resolution spectral data were available could yield absolute depths

clay mineralogical and geochemical constraints on late pleistocene weathering processes of the qaidam basin northern tibetan plateau abstract at the qarhan salt lake qsl on the central eastern qaidam basin northern tibetan plateau quaternary lacustrine sediments have a thickness of over 3000 m and mainly composed of organic rich clay and silty clay with some silt halite and halite in this study a 102 m long sediment core isl1a was obtained from the qsl combining with ams 14c and 230th dating clay minerals and major element concentrations of isl1a were used to reconstruct the weathering process and trend of the qsl since late pleistocene the results reveal that the clay mineral from

lunar regolith thickness determination from 3d morphology of small fresh craters abstract the lunar regolith can provide critical information about the moon and the space environment in the study of lunar regolith thickness is one of its most important parameters because of the significance in estimating the relative geologic age and the quantities of solar wind implanted volatiles in this research an improved morphological method for determining the lunar regolith thickness is proposed by directly measuring the distance from the lunar ground surface to the floor flat bottomed and central mound craters or bench concentric craters of indicative small fresh craters the pre impact ground surface is first modeled with crater edge points through plane fitting avoiding crater ejecta then the lunar regolith thickness is calculated as the distance between the modeled ground surface and the crater floor or bench the method has been verified at the landing sites of chang e 3 rover with high resolution stereo images from chang e 2 orbiter and the landing sites of apollo 11 12 14 15 16 and 17 missions with high resolution lunar reconnaissance orbiter dem data all the results are in good agreement with results from in situ measurements demonstrating the reliability of the proposed method this method can be applied to estimate lunar regolith thickness where high precision topographic data is available

analysis of impact crater populations and the geochronology of planetary surfaces in the inner solar system analyzing the density of impact craters on planetary surfaces is the only known technique for learning their ages remotely as a result crater statistics have been widely analyzed on the terrestrial planets since the timing and rates of activity are critical to understanding geologic process and history on the moon the samples obtained by the apollo and luna missions provide critical calibration points for cratering chronology on mercury venus and mars there are no similarly firm anchors for cratering rates but chronology models have been established by extrapolating from the lunar record or by estimating their impactor fluxes in other ways this review provides a current perspective on crater population measurements and their chronological interpretation emphasis is placed on how ages derived from crater statistics may be contingent on assumptions that need to be considered critically in addition ages estimated from crater populations are somewhat different than ages from more familiar geochronology tools e g radiometric dating resurfacing processes that remove craters from the observed population are particularly challenging to account for since they can introduce geologic uncertainty into results or destroy information about the formation age of a surface regardless of these challenges crater statistics measurements have resulted in successful predictions later verified by other techniques including the age of the lunar maria the existence of a period of heavy bombardment in the moon s first billion years and young volcanism on mars

distribution and fractionation of heavy metals in the surface sediments of the ganges brahmaputra meghna river system in the bengal basin the lower ganges brahmaputra meghna g b m drainage basin occupies the total bengal basin which is one of the unique basins of the world because of its location and size density of population and catastrophic deposition of sediments the increased heavy metal concentration in the 63 m fraction of surface sediments shows similarity among major segments of the g b m system in the basin which reflects the homogenization of lithologic and chemical diversity of the greater denudation regime by the river processes the differences in heavy metal concentation in the lower g b m system with that of its upper and middle counterpart is mainly related to the contrast between himalayan rivers and the other major south asian rivers and may be due to the geological differences of their denudation regime heavy metals in the lower g b m system have an affinity towards the clay fraction of the sediments the correlation matix of heavy metals in the lower brahmaputra and meghna suggests the importance of fe mn oxyhydroxides in their accumulations iron ti and mn are higher in the meghna main channel zn is higher in the meghna tributaries and cr is higher in both the brahmaputra and meghna compared to the value for standard shale the enrichment factor is 1 for most of the metals except mn which is relatively higher in the meghna and lower ganges main channels the geoaccumulation index igeo for most of the heavy metals lies below grade zero suggesting unpolluted sediment quality the lower ganges system shows relatively higher concentration in the nondetrital fraction of heavy metals probably due to the presence of petroleum refinery industrial and mining effluents and agricultural runoff in the drainage basin the relative uniformity in concentration of heavy metals in vertical profiles may be due to the uniformity in sediment grain size and catastrophic deposition of sediments where the time period represented by the vertical sediment column is not enough to reflect the cultural accumulation of heavy metals the bengal basin thus represents a relatively unperturbed alluvial basin with regards to heavy metal pollution

climatic and tectonic controls on chemical weathering in tropical southeast asia malay peninsula borneo and sumatra abstract clay mineralogy and major element geochemistry were investigated on 58 surface sediment samples collected in 27 rivers draining malay peninsula borneo and sumatra to assess the chemical weathering process and its controlling factors in tropical southeast asia the clay mineral assemblages show high kaolinite contents in malay peninsula average 80 sumatra 58 78 and south borneo 41 55 high illite contents in north borneo 47 77 and moderate smectite contents in sumatra 6 29 intensive chemical weathering is identified in all three investigated regions from both clay mineralogical and geochemical bulk and clay fraction results regardless of their various lithological and tectonic settings relatively the chemical weathering intensity increases gradually from north borneo to south borneo and further to malay peninsula and sumatra our results suggest that the east asian australian monsoon climatic condition with constant warm temperature and abundant precipitation throughout the year is the principal forcing factor on the chemical weathering and the tectonic activity including mountain uplift earthquakes and volcanic eruptions and their specific lithological characters is only a subordinate factor on the intensity of chemical weathering in tropical southeast asia

extraction of lunar domes from chang e 2 data with new method abstract lunar domes which are distributed mainly in the lunar mare were generated by lunar volcanism several billion years ago in this context identifying lunar mare domes and studying their morphological properties enhances the study of lunar volcanism traditionally most lunar domes have been identified by manually analyzing images or topographic maps of the lunar surface this approach has identified several lunar domes in specific local areas to learn more about global lunar domes it is necessary to identify them from the global lunar mare in this paper we present a method of identifying lunar domes using chang e 2 data we demonstrate the identification of domes and analyze their morphological and geological properties

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

a theoretical model for the formation of ring moat dome structures products of second boiling in lunar basaltic lava flows abstract newly documented ring moat dome structures rmdss low mounds typically several hundred meters across with a median height of 3 5 m and surrounded by moats occur in the lunar maria they appear to have formed synchronously with the surrounding mare basalt deposits it has been hypothesized that they formed on the surfaces of lava flows by the extrusion of magmatic foams generated in the flow interiors as the last stage of the eruption and flow emplacement process we develop a theoretical model for the emplacement and cooling of mare basalts in which the molten cores of cooling flows are inflated during the late stages of eruptions by injection of additional hot lava containing dissolved volatiles crystallization of this lava causes second boiling an increase in vapor pressure to the point of supersaturation due to crystallization of the melt generating copious quantities of vesicles magmatic foam layers at the top and bottom of the central core of the flow flow inflation of many meters is predicted to accompany the formation of the foam layers flexing the cooled upper crustal layer and forming fractures that permit extrusions of the magmatic foams onto the surface to form domes with subsidence of the subjacent and surrounding surface forming the moats by modeling the evolution of the internal flow structure we predict the properties of rmdss and the conditions in which they are most likely to form we outline several tests of this hypothesis

geomorphic and chronometric evidence for high lake level history in gahai lake and toson lake of north eastern qaidam basin north eastern qinghai tibetan plateau palaeoshorelines highstand lacustrine sediments and lakeshore terraces are preserved around saline lakes in the arid qaidam basin previous research indicates that the chronology of a mega paleolake in the qaidam basin during the late pleisotocene is controversial here we report quartz optically stimulated luminescence osl age estimates of highstand lacustrine sediments shoreline features and geomorphic exposures that contribute to a revision of the lake level history of gahai and toson lakes in the north eastern qaidam basin on the northeastern qinghai tibetan plateau qtp margin the results imply that i high lake levels at gahai and toson lakes based on quartz osl dating occurred at 85 72 63 55 31 5 4 and 0 9 0 7 ka probably corresponding to periods of warm and wet climate ii periods of high lake levels are almost synchronous with other lakes on the qtp e g qinghai and namco lakes with the highest late pleistocene levels occurring during marine oxygen isotope stage 5 and iii highstand phases on the qtp are out of phase with those of low latitude lakes in the southern hemisphere possibly driven by solar insolation variability in the low latitude region copyright 2011 john wiley sons ltd

tectonic uplift influenced monsoonal changes promoted hominin occupation of the luonan basin insights from a loess paleosol sequence eastern qinling mountains central china abstract quaternary soil deposits from northern and southern china are distinctly different reflecting variability of the east asian monsoon north and south of the qinling mountains coeval sediments from the transitional climatic zone of central china which are little studied to date have the potential to improve our understanding of quaternary monsoon changes and associated influences on hominin occupation of this region here we investigate in detail a well preserved and continuous quaternary loess paleosol sequence shangbaichuan from the luonan basin using a variety of weathering indices including major and trace element ratios clay mineralogy and fe oxide mineralogy the whole rock samples display similar rare earth element patterns characterized by upper continental crustal ratios la yb n 9 5 and eu eu 0 65 elemental data such as la yb n la th and eu eu ratios show a high degree of homogeneity suggesting that dust in the source region may have been thoroughly mixed and recycled resulting in all samples having a uniform initial composition indices for pedogenic weathering such as na k ba sr rb sr cia ciw cpa pia kaolinite illite kaolinite smectite illite and hematite hematite goethite exhibit similar secular trends and reveal a four stage accumulation history the indices also indicate that the climate was warmer and wetter during the most recent interglacial stage compared with coeval environments of the chinese loess plateau secular changes in weathering intensity can be related to stepwise uplift of the qinling mountains and variation in east asian monsoon intensity both of which played significant roles in controlling climate evolution in the luonan basin furthermore intensified aridity and winter monsoon strength in dust source areas as evidenced by mineralogic and geochemical changes may have been due to the mid pleistocene climate transition based on temporal correlation of warmer and wetter climatic conditions with more frequent hominin occupation we infer that the paleoclimate in the eastern qinling mountains remained mild and favorable during glacial stages of the late quaternary thus promoting early human settlement

model for the origin ascent and eruption of lunar picritic magmas a model for the origin ascent and eruption of the lunar a17 orange glass magma has been constructed using petrological constraints from gas solubility experiments and from analyses of the lunar sample 74220 to better determine the nature and origin of this unique explosive eruption three stages of the eruption have been identified stage 1 of the eruption model extends from 550 km the a17 orange glass magma source region based on phase equilibria studies to 50 km depth in the moon stage 2 extends from 50 km to 500 m where a c o h s gas phase formed and grew in volume based on melt inclusion analyses and measurements the volume of the gas phase at 500 m depth below the surface is calculated to be 7 to 15 vol of the magma closed system using the minimum and maximum estimates of co h2o and s loss from the melt in stage 3 depths shallower than 450 m the rising magma exsolved an additional 800 900 ppm h2o and 300 ppm s increasing the moles in the gas by a factor of 3 to 4 the closed system gas phase is calculated to reach 70 vol at 130 m depth enough to fragment the magma and form pyroclastic beads however fragmentation bead formation is interpreted to have occurred at depths ranging from 600 to 300 m below the lunar surface based on the pressure necessary to explain the c content of the orange glass beads the gas volume 70 required to fragment the ascending magma at this depth is a factor of 5 greater than the volume determined for closed system degassing of an orange glass magma at 500 m strongly implying that the gas was produced by open system degassing as the magma ascended from greater depths formation of the dike carrying the magma up from the 550 km deep source is considered to occur by a crack propagation mechanism wilson and head 2003 2017 the rapid dike propagation process facilitates gas collection by open system degassing in the upper part of the dike this is necessary to achieve the gas volumes required for magma fragmentation at 600 m depths and the magma ascent velocities to explain the wide areal distribution of the bead deposit the explosive nature of the picritic orange glass eruption and the homogeneity of the bead compositions are consistent with this gas assisted eruption scenario as is the evidence of a fe metal forming reduction event during stage 2 followed by a stage 3 oxidation event in the ascending magma

extracting accurate and precise topography from lroc narrow angle camera stereo observations abstract the lunar reconnaissance orbiter camera lroc includes two identical narrow angle cameras nac that each provide 0 5 to 2 0 m scale images of the lunar surface although not designed as a stereo system lroc can acquire nac stereo observations over two or more orbits using at least one off nadir slew digital terrain models dtms are generated from sets of stereo images and registered to profiles from the lunar orbiter laser altimeter lola to improve absolute accuracy with current processing methods dtms have absolute accuracies better than the uncertainties of the lola profiles and relative vertical and horizontal precisions less than the pixel scale of the dtms 2 5 m we computed slope statistics from 81 highland and 31 mare dtms across a range of baselines for a baseline of 15 m the highland mean slope parameters are median 9 1 mean 11 0 standard deviation 7 0 for the mare the mean slope parameters are median 3 5 mean 4 9 standard deviation 4 5 the slope values for the highland terrain are steeper than previously reported likely due to a bias in targeting of the nac dtms toward higher relief features in the highland terrain overlapping dtms of single stereo sets were also combined to form larger area dtm mosaics that enable detailed characterization of large geomorphic features from one dtm mosaic we mapped a large viscous flow related to the orientale basin ejecta and estimated its thickness and volume to exceed 300 m and 500 km 3 respectively despite its 3 8 billion year age the flow still exhibits unconfined margin slopes above 30 in some cases exceeding the angle of repose consistent with deposition of material rich in impact melt we show that the nac stereo pairs and derived dtms represent an invaluable tool for science and exploration purposes at this date about 2 of the lunar surface is imaged in high resolution stereo and continued acquisition of stereo observations will serve to strengthen our knowledge of the moon and geologic processes that occur across all of the terrestrial planets

u series chronology of sediments associated with late quaternary fluctuations balikun lake northwestern china abstract the u series dating method was used to date the sediment core b194 from balikun lake xinjiang northwestern china the samples were extracted with acids of different concentrations and 230th 232th and 234u 232th ratios of each sample were measured contamination with non radiogenic 230th can be overcome in most instances using an isochron correction scheme for a sequential acid leach procedure the method can provide the most reliable dates from samples in lake of the arid semiarid regions where carbonate is assumed close to uranium and thorium after deposition where three known ages of palaeomagnetic reversals have already been obtained in the same core the u series ages appear to compare reasonably well with palaeomagnetic event ages based on the u series chronology and stable isotope records lake level history was reconstructed which suggests that balikun has been a shallow saline lake since 150 ka bp and its level frequently changed in response to climate changes arid climates occurred between 129 71 ka bp and at 62 25 ka bp corresponding to marine oxygen isotopic stages ois 5 and 3 during which times balikun lake approached playa conditions after 13 ka bp the lake shrank and became a saline field and mudflat with a water table at or below the lake bed three major high lake stands were identified at about ca 138 132 69 65 and 25 18 ka bp and the three high stand periods correspond to ois 6 4 and 2 rising lake levels during the penultimate glaciation and both stades of the last glaciation might have resulted from the location of the lake in an arid region where the climate was controlled mainly by the westerly winds

experimental study on impact induced seismic wave propagation through granular materials abstract impact induced seismic waves are supposed to cause movements of regolith particles resulting in modifications of asteroidal surfaces the imparted seismic energy is thus a key parameter to determining the scale and magnitude of this seismic shaking process it is important to study the propagation velocity attenuation rate and vibration period of the impact induced seismic wave to estimate the seismic energy hence we conducted impact cratering experiments at kobe university using a 200 m glass beads target to simulate a regolith layer and measured the impact induced seismic wave using three accelerometers set on the target surface at differences ranging from 3 2 to 12 7 cm the target was impacted with three kinds of projectiles at 100 m s 1 using a one stage gas gun the propagation velocity of the seismic wave in the beads target was 108 9 m s 1 and the maximum acceleration gmax in the unit of m s 2 measured by each accelerometer showed good correlation with the distance from the impact point normalized by the crater radius x r irrespective of projectile type they also were fitted by one power law equation gmax 102 19 x r 2 21 the half period of the first peak of the measured seismic waves was 0 72 ms and this duration was almost consistent with the penetration time of each projectile into the target according to these measurements we estimated the impact seismic efficiency factor that is the ratio of seismic energy to kinetic energy of the projectile to be almost constant 5 7 10 4 inside the crater rim while it exponentially decreased with distance from the impact point outside the crater rim at a distance quadruple of the crater radius the efficiency factors were 4 4 10 5 for polycarbonate projectile and 9 5 10 5 for alumina and stainless steel projectiles

chemical weathering in the three rivers region of eastern tibet abstract three large rivers the chang jiang yangtze mekong lancang jiang and salween nu jiang originate in eastern tibet and run in close parallel over 300 km near the eastern himalayan syntaxis seventy four river water samples were collected mostly during the summer season from 1999 to 2004 their major element compositions vary widely with total dissolved solids tds ranging from 31 to 3037 mg l reflecting the complex geologic makeup of the vast drainage basins the major ion distribution of the main channel samples primarily reflects the weathering of carbonates evaporite dissolution prevails in the headwater samples of the chang jiang in the tibetan plateau interior as evidenced by the high tds 928 and 3037 mg l and the na cl dominant major element composition local tributary samples of the mekong and salween draining the lincang batholith and the tengchong volcano show distinctive silicate weathering signatures we used five reservoirs rain halite sulfate carbonate and silicate in a forward model to calculate the contribution from silicate weathering to the total dissolved load and to estimate the consumption rate of atmospheric co 2 by silicate weathering carbonate weathering accounts for about 50 of the total cationic charge tz in the samples of the mekong and the salween exiting the tibetan plateau in the exit sample of the chang jiang 45 of tz is from halite dissolution inherited from the extreme headwater tributaries in the interior of the plateau and carbonates contribute only 26 to the tz the net rate of co 2 consumption by silicate weathering is 103 121 10 3 mol km 2 year 1 lower than the rivers draining the himalayan front gis based analyses indicate that runoff and relief can explain 52 of the spread in the rate of atmospheric co 2 drawdown by silicate weathering but other climatic temperature precipitation potential evapotranspiration and geomorphic elevation slope factors also show collinearity only qualitative conclusions can be drawn for the significance of lithology due to lack of digitized lithologic information the effect of the peculiar drainage pattern due to tectonic forcing is not readily apparent in the major element composition or in increased chemical weathering rates the 87 sr 86 sr ratios and the silicate weathering rates are in general lower in the three rivers than in the rivers draining the himalayan front

chemical weathering in luzon philippines from clay mineralogy and major element geochemistry of river sediments clay mineralogy and major element geochemistry of 35 surface sediment samples collected in 21 major to moderate rivers of luzon philippines are used to evaluate the present chemical weathering process the clay mineral assemblage consists mainly of smectite average 86 with minor kaolinite 9 and chlorite 5 and very scarce illite 1 and does not show strong island wide differences the major element results of both bulk and clay fraction sediments indicate that the formation of clay minerals is accompanied by leaching of ca and na first and of fe and mn thereafter during the chemical weathering process a low moderate chemical weathering degree of bulk sediments and a moderate intensive degree of clay fraction sediments are obtained in luzon rivers based on proxies of chemical index of alteration cia and smectite crystallinity it is suggested that the majority of andesitic basaltic volcanic and sedimentary rocks along with the tectonically active geological setting and sub tropical east asian monsoon climate are responsible for the predominance of smectite in the clay mineral assemblage

the cauchy 5 small low volume lunar shield volcano evidence for volatile exsolution eruption patterns and type 1 type 2 hybrid irregular mare patch formation the lunar shield volcano cauchy 5 sitting at the low diameter height volume end of the population is the only known example containing two different types of irregular mare patches imps in very close association 1 the pit crater interior type 1 imp composed of bleb like mounds surrounded by a hummocky and blocky floor unit and 2 type 2 imps small often optically immature pits less than 5 m deep located on the generally block deficient shield flanks a four phase lunar magma ascent eruption model predicts that during a relatively brief eruption low magma rise rates maximize volatile exsolution in lava filling the pit crater bubble rich magmas overtop the pit crater and form extremely vesicular flows on the shield flanks exposure of the flanking flows to vacuum produces a fragmental layer of exploded glassy bubble walls subsequent second boiling upon cooling of the flanking flow interiors releases additional volatiles which migrate and collect forming magmatic foams and gas pockets as magma rise rates slow trapped gas and magmatic foam build up below the cooling pit crater floor magmatic foams are extruded to form type 1 imp deposits type 2 imps on the flanks are interpreted to be due primarily to subsequent impacts causing collapse of the flow surface layer into the extremely vesicle and void rich flow interior anomalously young pit crater floor shield flank crater retention ages compared with surrounding maria ages may be due to effects of cauchy 5 substrate characteristics extreme micro and macroporosity foamy nature and glassy auto regolith on superposed crater formation and retention

integrated spectral analysis of mare soils and craters applications to eastern nearside basalts abstract high spatial resolution clementine images are examined to measure the reflectance properties of small and optically immature mare craters that have sampled discrete compositional units the spectral properties of these relatively crystalline mare materials are compared to associated mature soils to determine the effects of space weathering on specific basalt types space weathering is observed to alter the optical properties of distinct lunar basalt units in a systematic manner allowing compositional distinctions to be recognized across maturity states ultraviolet visible reflectance properties of mare basalts are sensitive to titanium content but are relatively independent of maturity state and demonstrate only a slight reddening as regoliths mature to soils other compositional distinctions between basalt types are identified by differences in albedo and band strength of ferrous minerals that are maintained over a full range of maturity states immature deposits within large craters are compared to the spectral properties of well defined mare units to examine the composition of buried materials when craters excavate through the mare highland contamination is readily identified as a mixing relation between mafic and feldspathic lithologies the approach presented here provides new information on the composition and stratigraphy of several nearside mare deposits including the identification of thin low iron and very low titanium basalts in lacus somniorum and more iron rich low titanium basalts in eastern mare frigoris

drainage geomorphic evolution in response to paleoclimatic changes since 12 8 ka in the eastern kunlun mountains ne qinghai tibetan plateau abstract investigation of the geomorphologic evolution of drainage basins can provide insight into the response of mountain basin systems to paleoclimate fluctuations this study investigates the evolution of geomorphic units and their connectivity from upstream piedmont to downstream salt lake since the late quaternary in the golmud river catchment of the eastern kunlun mountains klm the study aims to elucidate the debate over linkages between 1 landform evolution and paleoclimatic change and 2 dynamic geomorphic processes and lake evolution in the lower basin based on geomorphic and sedimentological observations and an optically stimulated luminescence osl chronology we show three main phases of geomorphic processes 1 upstream piedmont alluvial fans and an alluvial delta fan at the salt lake margin have surface sediment osl ages of 12 8 11 4 ka suggesting a valley aggradation stage in which mass periglacial detritus were eroded and redeposited in the drainage basin 2 incision terraces in alluvial valley fills provide ages between 11 4 and 8 8 8 1 6 2 and 4 9 3 9 ka incision is ascribed to the reduction in supply of detritus owing to glacial recession and enhanced precipitation in the early to middle holocene and 3 widely distributed swamp sediments in the distal delta fan date to 3 2 1 8 ka suggesting a wetter stage within the late holocene climatic deterioration loess indicative of aridity was deposited intermittently during the middle to late holocene we reconstructed a wetness index based on wetness scores of drainage geomorphic units which is consistent with published moisture proxies this association implies that 1 landform processes in klm responded well to precipitation fluctuations in indian summer monsoon ism dominant regions indicating their climatic forcing and 2 precipitation variations in the eastern klm have been mainly controlled by ism intensity since 12 8 ka linking the geomorphologic evolution of mountain basin systems to downstream arid basin evolution shows that the periods of fluvial terrace incision early to middle holocene were probably important sources of lake salt mineral enrichment the landscape evolution patterns of mountain basin systems in the eastern klm offer a model for assessing the linkages between geomorphic processes paleoclimatic changes and lake evolution in other arid regions

growth of planetary crusts the planets and satellites of the solar system show much diversity but most have formed crusts which differ substantially from their bulk compositions three principal types of crust may be broadly distinguished primary formed after accretional heating e g lunar highlands secondary formed following partial melting in planetary mantles e g lunar maria terrestrial oceanic crust and tertiary formed by processing of secondary crusts of which the continental crust of the earth is the only identifiable example crustal growth before 3800 m y was complicated by the heavy planetesimal bombardment active erosion on the earth is likely to have destroyed the brecciated rubble resulting from over 200 mare orientale scale events in this period the mercurian crust is probably primary perhaps analogous to the lunar highlands in contrast the observable martian and venusian crusts are secondary dominated by basaltic volcanism the icy crusts of the satellites of the outer planets are mixtures of both primary and secondary crusts with complex histories ganymede is of special interest in displaying a secondary grooved terrain water ice crust which has split an older more heavily cratered possibly primary crust slight expansion has resulted probably from polymorphic transitions from high density ice viii to low density ice i the primary lunar crust 12 of lunar volume grew in 108 years secondary crusts derived by partial melting of mantles grow at a much slower rate total production of terrestrial oceanic crust over 4000 m y is only 2 of planetary volume whereas terrestrial continental crustal growth is even slower producing over the same period a volume only about 0 33 that of the earth crustal growth on the other planets appears to be an irreversible process without evidence of recycling no evidence for massive planetary expansion as required by expanding earth hypotheses is apparent on the other planets or satellites of the solar system

weathering of the ganga alluvial plain northern india implications from fluvial geochemistry of the gomati river abstract in the northern part of the indian sub continent the ganga alluvial plain gap feeds its weathering products to the ganga brahmaputra river system one of the world s largest fluvial systems the authors present a geochemical study of the gap weathering products transported by the gomati river the ganga river tributary to understand weathering processes of an alluvial plain in a humid sub tropical climate a total of 28 sediment samples were collected during the monsoon season and were analysed by x ray fluorescence spectrometry for 25 major and trace elements bulk chemistry of the channel flood and suspended sediments mostly consists 90 80 and 75 respectively of three elements al si and fe major element concentrations normalised with respect to upper continental crust ucc show strong depletion of highly mobile elements na ca and enrichment of immobile elements ti si silica enrichment in the sand fraction is probably caused by chemical weathering of feldspar mineral sorting during fluvial transportation acts as the single important factor that controls the geochemistry of these weathering products and also strongly influences major and trace element distribution in the individual sediment samples trace element ba cr cu nb ni pb v and zn concentrations were strongly correlated with major element si al fe mn and k concentrations indicating that the abundance of trace elements is controlled by the same processes that control the major element distribution in these sediments the gap weathering products were geochemically distinguished as arkose to litharenite in rock classification chemical mobility normalised with respect to tio 2 in ucc indicates that si na zr ba and sr mainly derived from feldspar muscovite and biotite are lost during weathering iron and zn remained immobile during weathering and were strongly adsorbed by phyllosilicates and concentrated in fine grained sediment fractions the chemical index of alteration indicates that the gap has experienced chemical weathering of incipient to moderate intensity the gap weathering products also demonstrated a progressive incomplete alteration in the alluvial sequence made up of the himalayan derived sediments a model has been proposed to better understand weathering processes and products of the gap in temporary storage of 50 ka in a humid sub tropical climate

the role of substrate characteristics in producing anomalously young crater retention ages in volcanic deposits on the moon morphology topography subresolution roughness and mode of emplacement of the sosigenes lunar irregular mare patch lunar irregular mare patches imps comprise dozens of small distinctive and enigmatic lunar mare features characterized by their irregular shapes well preserved state of relief apparent optical immaturity and few superposed impact craters imps are interpreted to have been formed or modified geologically very recently 100 ma braden et al 2014 however their apparent relatively recent formation modification dates and emplacement mechanisms are debated we focus in detail on one of the major imps sosigenes located in western mare tranquillitatis and dated by braden et al 2014 at 18 ma the sosigenes imp occurs on the floor of an elongate pit crater interpreted to represent the surface manifestation of magmatic dike propagation from the lunar mantle during the mare basalt emplacement era billions of years ago the floor of the pit crater is characterized by three morphologic units typical of several other imps i e 1 bulbous mounds 5 10 m higher than the adjacent floor units with unusually young crater retention ages meters thick regolith and slightly smaller subresolution roughness than typical mature lunar regolith 2 a lower hummocky unit mantled by a very thin regolith and significantly smaller subresolution roughness and 3 a lower blocky unit composed of fresh boulder fields with individual meter scale boulders and rough subresolution surface texture using new volcanological interpretations for the ascent and eruption of magma in dikes and dike degassing and extrusion behavior in the final stages of dike closure we interpret the three units to be related to the late stage behavior of an ancient dike emplacement event following the initial dike emplacement and collapse of the pit crater the floor of the pit crater was flooded by the latest stage magma the low rise rate of the magma in the terminal stages of the dike emplacement event favored flooding of the pit crater floor to form a lava lake and co gas bubble coalescence initiated a strombolian phase disrupting the cooling lava lake surface this phase produced a very rough and highly porous with both vesicularity and macroporosity lava lake surface as the lake surface cooled in the terminal stage of the eruption dike closure with no addition of magma from depth caused the last magma reaching shallow levels to produce viscous magmatic foam due to h2 o gas exsolution this magmatic foam was extruded through cracks in the lava lake crust to produce the bulbous mounds we interpret all of these activities to have taken place in the terminal stages of the dike emplacement event billions of years ago we attribute the unusual physical properties of the mounds and floor units anomalously young ages unusual morphology relative immaturity and blockiness to be due to the unusual physical properties of the substrate produced during the waning stages of a dike emplacement event in a pit crater the unique physical properties of the mounds magmatic foams and hummocky units small vesicles and large void space altered the nature of subsequent impact cratering regolith development and landscape evolution inhibiting the typical formation and evolution of superposed impact craters and maintaining the morphologic crispness and optical immaturity accounting for the effects of the reduced diameter of craters formed in magmatic foams results in a shift of the crater size frequency distribution age from 100 myr to billions of years contemporaneous with the surrounding ancient mare basalts we conclude that extremely young mare basalt eruptions and resulting modification of lunar thermal evolution models to account for the apparent young ages of the imps are not required we suggest that other imp occurrences both those associated with pit craters atop dikes and those linked to fissure eruptions in the lunar maria may have had similar ancient origins

terrestrial analogues for lunar impact melt flows abstract lunar impact melt deposits have unique physical properties they have among the highest observed radar returns at s band 12 6 cm wavelength implying that they are rough at the decimeter scale however they are also observed in high resolution optical imagery to be quite smooth at the meter scale these characteristics distinguish them from well studied terrestrial analogues such as hawaiian p hoehoe and a lava flows the morphology of impact melt deposits can be related to their emplacement conditions so understanding the origin of these unique surface properties will help to inform us as to the circumstances under which they were formed in this work we seek to find a terrestrial analogue for well preserved lunar impact melt flows by examining fresh lava flows on earth we compare the radar return and high resolution topographic variations of impact melt flows to terrestrial lava flows with a range of surface textures the lava flows examined in this work range from smooth hawaiian p hoehoe to transitional basaltic flows at craters of the moon cotm national monument and preserve in idaho to rubbly and spiny p hoehoe like flows at the recent eruption at holuhraun in iceland the physical properties of lunar impact melt flows appear to differ from those of all the terrestrial lava flows studied in this work this may be due to a differences in post emplacement modification processes or b fundamental differences in the surface texture of the melt flows due to the melts unique emplacement and or cooling environment information about the surface properties of lunar impact melt deposits will be critical for future landed missions that wish to sample these materials