early mis 3 occupation of mochena borago rockshelter southwest ethiopian highlands implications for late pleistocene archaeology paleoenvironments and modern human dispersals abstract between 70 and 50 ka bp anatomically modern humans dispersed across and out of africa to eventually populate all inhabitable continents knowledge of paleoenvironments and human behavioral patterns in africa prior to and during these dispersals is crucial for understanding how and why hunter gatherers were able to adapt rapidly to the new environments they encountered however few well dated sites from this time period are known from the horn of africa one of the purported staging areas for population movements into southern arabia and asia excavations at mochena borago rockshelter situated on the western slopes of a dormant volcano where the sw ethiopian highlands meet the ethiopian rift have yielded the first securely dated archaeological sequence for later periods of the dispersal three major lithostratigraphic groups incorporating occupational episodes have yielded charcoal radiocarbon ages 53 38 ka calbp deeper deposits have been tested but remain undated archaeological assemblages consist mainly of obsidian flaked stone artifacts manufactured from small minimally prepared single to multi platform flake cores radially prepared cores are rare and blade cores are absent small unifacial to bifacial points from non radial cores dominate the earliest shaped tool assemblages and backed pieces first appear by 45 ka calbp by 43 ka calbp scrapers and backed pieces are predominant rather than points however there is little evidence for technological change other than the appearance of bipolar technology mochena borago s archaeological sequence thus cannot be neatly classified as middle stone age later stone age or transitional and calls into question some of the principles by which archaeologists have attempted to classify african toolmaking traditions

late holocene terrestrial glacial history of miki and i c jacobsen fjords east greenland we present a late holocene glacial and environmental history of three valleys within miki and i c jacobsen fjords east greenland 68 n the fjords have no direct connection with the main ice sheet and are presently glacierized by a series of local ice caps and glaciers little sediment has been deposited within the study area but bedrock is distinctly glacially striated which suggests that extensive valley glaciers reached the present coastline in the past moraines are the prominent morphological features including distinct end and lateral moraines most of the moraines are related to the existing glaciers in the area apparent moraines extend as far as 2 to 2 5 km in front of present day glaciers based on morphological and stratigraphical studies of the sediments in these valleys five glacier advances during the late holocene are implied stabilization of the oldest moraines is lichenometrically dated to c 1450 to 1650 years ago younger moraines in both miki and i c jacobsen fjords are lichenometrically dated to c 1050 1100 years ago c 750 950 years ago and c 600 700 years ago the youngest moraines containing measurable lichens stabilized c 300 400 years ago the timing of this moraine formation correlates to marine records from previous research on the inner part of miki fjord where apparent intensification in sediment stratification is related to a glacier advance into the fjord c 290 years ago this glacial advance may correlate to the little ice age cooling observed in many records from the north atlantic region our glacial record from miki and i c jacobsen fjords also shows good correlation with temperature proxies within the grip ice core in greenland and foraminifera records from nansen fjord east greenland less pronounced correlation is observed with the icelandic sea ice index and records of glacier fluctuation in iceland during the last 1000 years these results suggest that widespread climatic cooling was the direct cause of many of the late holocene glacier variations documented in this study although the glacial advance at c 1050 1100 years ago coincides with the so called medieval warm period and could reflect the response of glaciers to increased precipitation within the area

quartz grains reveal sedimentary palaeoenvironment and past storm events a case study from eastern baltic abstract sediment record collected from the coastal lake serves as a powerful tool for reconstructing changes in palaeoenvironment and understanding the potential signals of past storminess in this study we use several proxies from sediment of the holocene thermal maximum at coastal lake lilaste latvia we focus on surface texture of quartz grains from the mineral inorganic fraction as indicators of depositional environments we then use this as a proxy for potential storm transport and combine with information on granulometry diatom stratigraphy and chronology to answer the question whether flux of quartz grains in the lake originated from the sea or from the land analyses in a binocular and scanning electron microscope reveal that most of the investigated quartz grains originate from dwelling in the seawater and wave action in the nearshore zone grains representing very energetic subaqueous environment similar to storm events are also present terrestrial record is of minor significance and visible through occurrence of aeolian quartz grains during drier and colder conditions an influx of sand with aeolian imprint was delivered to the lake between 8500 and 7800 cal yr bp marine and terrestrial conditions alternated between 7800 and 6000 cal yr bp storm induced grains were likely deposited three times at 7300 cal yr bp 6600 6400 cal yr bp and 6200 6000 cal yr bp overall stable marine environmental conditions prevailed between 6000 and 4000 cal yr bp except of the last portion of terrestrial induced sediment at 4100 cal yr bp

lichenometric dating using rhizocarpon subgenus rhizocarpon in the patagonian andes argentina abstract this study represents the first attempt to develop and apply lichenometric dating curves of rhizocarpon subgenus rhizocarpon for dating glacier fluctuations in the patagonian andes six glaciers were studied along the patagonian andes surfaces of known ages historical evidences and tree ring analyses were used as control sites to develop indirect lichenometric dating curves dating curves developed for the studied glaciers show the same general logarithmic form indicating that growth rate of subgenus rhizocarpon decreases over time the strong west east precipitation gradient across the andean cordillera introduces statistically significant differences in the growth curves with faster growth rates in the moist west sites than the drier eastern sites latitudinal difference among the studied glaciers does not appear to be a major factor regulating lichen growth rates therefore we developed two lichenometric curves for dating glacier fluctuations in wetter and drier sites in the patagonian andes during the past 450 yrs application of the developed curves to moraine dating allowed us to complement glacial chronologies previously obtained by tree ring analyses a first chronosequence for moraine formation in the torrecillas glacier 42 s is presented our findings confirm the utility of lichenometry to date deglaciated surfaces in the patagonian andes

dating san andreas fault earthquakes with lichenometry regionalrockfalleventsinthesierranevadaofcaliforniaare caused by distant earthquakes on the northern and southern san andreasfaultaswellasbylocalearthquakes lichenometricdating of synchronous pulses of rockfalls that are presumed to be caused by five historical earthquakes suggests an accuracy of 2 2 3 5 yr 95 confidence level for dating young events comparison of lichenometric ages for prehistorical rockfalls with precise radiocarbon ages of surface rupture times at the pallett creek and wrightwood paleoseismology sites indicates that earthquakes on the southern san andreas fault caused rockfalls 200 to 400 km to the north a major rockfall event at about a d 1690 supports the fumal et al 1993 model for a san andreas fault earthquake that was not detected at pallett creek the a d 1690 event in the chronology indicates that the earthquake recurrence interval was shorter and that the degree of clustering of times of earthquakes was less on the mojave segment of the san andreas fault than previously thought

a rhizocarpon geographicum growth curve for the cascade range of washington and northern oregon usa lichen thallus measurements from 22 surfaces of known age on mount baker mount hood and mount rainier are used to construct a regional rhizocarpon geographicum growth curve for the cascade range of washington and northern oregon growth rates determined by measuring the largest thallus diameters on the same surfaces at mount rainier in 1976 and 2002 are used for comparison with lichenometric data from mount baker and mount hood similar lichen thallus diameter vs age relationships identified in the data from the three mountains suggest the presence of uniform growth rates over the 400 km range a regional growth curve developed during our study shows three growth phases of successively slower growth a rapid phase from 8 to 20 yr a linear phase from 20 to 145 yr and a slow phase of unknown duration beyond ca 145 yr uncertainty in lichen growth rates beyond 145 yr limits projection of the curve beyond that age however the age range of the constrained growth curve covers an important period of recent climate variability when applied in appropriate settings our growth curve can be used to determine numeric ages to 10 yr for surfaces between 20 and 145 years old in areas where other techniques are not applicable or do not provide unique or well constrained ages

aeolian microtextures in silica spheres induced in a wind tunnel experiment comparison with aeolian quartz abstract microtextures in quartz attributed to aeolian transport principally bulbous edges and abrasion fatigue have seldom been tested in the laboratory under controlled conditions a wind tunnel experiment was conducted using glass spheres 70 sio 2 as a proxy for quartz with the objective of determining the extent of mechanical damage to silica glass transported in a mixture with quartz beach sand the microspheres were microscopically imaged prior to transport in a wind tunnel subjected at velocities ranging from 4 to 13 m s in sequential runs of 10 min the range in velocity is capable of lifting grains into the air column or saltating quartz grains and silica glass spheres to produce mechanical impact i e abrasion commonly experienced in aeolian transport with increasing velocity silica glass spheres which displayed minor imperfections prior to transport began to show significant grain damage exhibiting increasing depth into the silica glass fabric a result of mechanical contact as well as increasing frequency of craters dislodged plates and abrasion fatigue while pits appear earlier in the experiment 8 m s dislodged plates and abrasion fatigue need a threshold velocity of near 10 m s to become more frequent bulbous edges on the grain surface often considered the hallmark of aeolian transport are not seen in the grain population analyzed possibly because of the initial near perfect sphericity of the silica glass spheres the experiment proved that aeolian transport throughout short distances and during a relatively short period of time is enough to imprint significant abrasion marks in microspheres in fact the microtextures produced were fresh surfaces fractures and abrasion that imprinted areas of different sizes a comparison of microtextural imprints on silica glass spheres relative to coastal dune sands was made to better understand energy thresholds required to achieve grain damage

flood alluviation and entrenchment holocene valley floor development and transformation in the british uplands the morphology sedimentary properties and sequence of recent coarse grained flood deposits and earlier holocene alluvial fills were investigated in thinhope burn a small 12 km2 catchment in the northern pennine uplands northern england twenty one large flood events are recorded by distinctive cobble boulder bars sheets and splays and boulder berms and lobes lichenometric analysis showed that all but one of these floods dated from the mid eighteenth century the timing of large floods between 1766 and 1960 corresponds with major hydroclimatic trends evident in northern britain and northwest europe over this period discharge estimates suggest that flood magnitudes have decreased since the mid eighteenth century channel and flood plain metamorphosis in late roman times and in the eighteenth century following major valley floor entrenchment locally as much as 8 m would appear to have been caused by increased runoff and flood magnitude this was linked to a shift to a wetter climate with flow augmented by iron age and roman woodland clearance and drainage of the catchment in more recent times results from this study suggest that current models of longer term holocene and pleistocene valley floor development in the british uplands may need to be re evaluated

preservation of elemental and isotopic source identification of sedimentary organic matter the amount and type of organic matter in the sediments of lakes and oceans contribute to their paleoenvironmental and paleoclimatological records only a small fraction of the initial aquatic organic matter survives destruction and alteration during sinking and sedimentation selective degradation modifies the character of the surviving small fraction of organic matter which becomes incorporated in bottom sediments organic matter alterations can continue to sub bottom depths of hundreds of meters corresponding to millions of years source and paleoenvironmental information nonetheless remains preserved in the molecular elemental and isotopic compositions of organic matter c n and 13c values of total organic matter in particular appear to retain paleoenvironmental information for multi myr time periods

middle paleolithic occupation on a marine isotope stage 5 lakeshore in the nefud desert saudi arabia major hydrological variations associated with glacial and interglacial climates in north africa and the levant have been related to middle paleolithic occupations and dispersals but suitable archaeological sites to explore such relationships are rare on the arabian peninsula here we report the discovery of middle paleolithic assemblages in the nefud desert of northern arabia associated with stratified deposits dated to 75 000 years ago the site is located in close proximity to a substantial relict lake and indicates that middle paleolithic hominins penetrated deeply into the arabian peninsula to inhabit landscapes vegetated by grasses and some trees our discovery supports the hypothesis of range expansion by middle paleolithic populations into arabia during the final humid phase of marine isotope stage 5 when environmental conditions were still favorable

photosynthetic rate and thallus size are not related in alpine yellow green rhizocarpon crustose lichens implications for lichenometry and growth abstract lichenometry first proposed at the beginning of the xxth century is a technique that uses growth rates of saxicolous crustose lichens to date exposed surfaces over an age range of 500 years from present despite of the wide use of the methodology it has been strongly criticized by several authors who consider that biological aspects involved in growth rates of lichens used are not sufficiently considered and that this will contribute to uncertainty in the final surface dating the assumption important for direct lichenometric measurements that crustose lichens have constant growth rates through all their life span is controversial with some works pointing to a change in growth rate with thallus size in yellow green rhizocarpon sp samples the most widely lichens used for surface dating this change in growth rate with size would contribute to inaccuracy in dating in this work we contribute to the discussion with a novel approach in which we measure several physiological parameters linked to carbon gain in 42 rhizocarpon sp samples of different sizes collected in the same locality we found no significant relationship between thallus photosynthetic rate and thallus size indicating that possible growth rate variations over rhizocarpon life span are not linked to carbon gain the experiment performed provides a new data set to include in lichenometric modelling with the aim to obtain a better understanding of crustose lichens biology before attempting more feasible and accurate surface dating strategies measurements of length of activity periods and carbon allocation in rhizocarpon are recommended to achieve future improvements in this direction

lichen dating of earthquake generated regional rockfall events southern alps new zealand synchronous regional rockfall events triggered by large earthquakes in the southern alps of new zealand were used to evaluate and improve the lichenometry method for surface exposure dating digital calipers were used to measure the maximum diameter of the largest lichen on many rockfall blocks using a fixed area largest lichen fall sampling strategy regional significance of fall peaks can be tested by confirming the occurrence of a coeval peak at multiple sites and by showing an increase in peak size toward the earthquake epicenter significance of fall peaks at a local site can be described in terms of peak size relative to a uniform density of fall sizes measurements of 34 000 fall sizes on fully exposed rockfall blocks and outcrop joint faces at 90 sites allow precise dating of geomorphic events of the past 300 to 500 yr uncertainties at the 95 confidence interval can be reduced to a level better than 10 yr for ages within the calibrated time range represented by the lichen growth equation recognition of prehistorical regional rockfall events in 1833 1836 and 1840 demonstrates the excellent resolution of this dating method precise dates result from exceptionally low measurement errors of lichen sizes relative to their growth rate tightly clustered fall sizes for earthquake induced rockfall events and substrate exposure times for calibration sites that are known to the year or day fall peaks for synchronous rockfall events are the same for 20 sites with diverse climate altitude and substrate lithology a regionally consistent lichen growth rate allows use of a single growth rate equation for most species of rhizocarpon subgenus rhizocarpon on the south island of new zealand a nonlinear growth equation suggests that the first colonization on average occurs in the 5th yr after formation of new rock surfaces 0 5 m 2 unit areas and is followed by rapid exponentially declining growth for about 20 yr greatgrowth phase that is largely completed by the 24th yr then linear growth persists at about 15 mm per century uniform growth phase

geomorphological effects of tsunami run up and backwash abstract geomorphological processes associated with tsunami run up and backwash are highly complex to date most studies have considered the sedimentology of palaeo tsunamis while almost no detailed studies have been undertaken in areas known to have been affected by tsunamis in recent times research on contemporary tsunamis show that coastal landscapes may be greatly altered not only by direct tsunami run up orthogonal to the shoreline but also by episodes of vigorous backwash and by water flow sub parallel to the coastline the combined effect of these processes produces hitherto unrecognised coastal landforms that are dominated by the effects of high magnitude erosion and deposition deposition of large boulders is also associated with severe tsunamis while in adjacent areas run up processes often result in the deposition of continuous and discontinuous sediment sheets in many instances the upper limit of sediment deposition lies well below the upper limit of wave run up which is frequently marked by a well defined zone of stripped vegetation and soil the processes described have considerable implications for models of coastal evolution it may even be the case that the evolution of particular stretches of coastline are dominated by such high magnitude low frequency events

transgressive sand sheet covering the shelf and upper slope off sendai northeast japan abstract a thin sand sheet deposited during the last major transgression from 14 000 to 6000 yrs b p covers the shelf and upper slope off sendai northeast japan the sand sheet overlies the sediments deposited during the last low sea level stand and is partly overlain by modern offshore muds this sheet is regarded as palimpsest sediment formed during the transgression in water depths of 50 m the sand sheet is 50 150 cm thick and consists of alternations of poorly sorted thin sand layers and mud layers that are several millimeters to a few centimeters thick it bears mixed environment molluscan shells and small amounts of glauconite scour and fill structures are frequently found gravel with shell fragments is common near the base of the sheet

a development of the lichenometric method applied to the dating of glacially influenced debris flows in southern chile lichenometry is a dating technique that has problems relating to questionable assumptions the development of a size frequency approach previously used in attempts to resolve some of the problems is described and applied to the dating of four debris flows marginal to the san rafael glacier in southern chile this study provides examples of the development s application its problems and directions for further work the size frequency approach based on new assumptions uses parameters derived from population size frequency distributions of the lichen species placopsis patagonica to provide relative and absolute dating for rock surfaces changes in the shapes of distributions suggest the relative age of populations absolute dating is based on a curve spanning a 24 year time period derived from mean diameter size age correlations a stratified random sampling design permits the use of inferential statistics standard deviations and confidence intervals show error margins the degree of relatedness between neighbouring populations and populations that are anomalous one way analysis of variance is used to indicate where populations may safely be grouped the size frequency approach appears to be particularly suitable for use on unstable debris flows where secondary movements are common the approach also demonstrates that lichen growth and colonization are sensitive to aspect differences and other variations in microhabitat

an early mis 3 pluvial phase in southeast arabia climatic and archaeological implications climatic changes in arabia are of critical importance to our understanding of both monsoon variability and the dispersal of anatomically modern humans amh out of africa the timing of dispersal is associated with the occurrence of pluvial periods during marine isotope stage mis 5 ca 130 74 ka after which arid conditions between ca 74 and 10 5 ka are thought to have restricted further migration and range expansion within the arabian interior whilst a number of records indicate that this phase of aridity was punctuated by an increase in monsoon strength during mis 3 uncertainties regarding the precision of terrestrial records and suitability of marine archives as records of precipitation mean that the occurrence of this pluvial remains debated here we present evidence from a series of relict lake deposits within southeastern arabia which formed at the onset of mis 3 ca 61 58 ka at this time the incursion of monsoon rainfall into the arabian interior activated a network of channels associated with an alluvial fan system along the western flanks of the hajar mountains leading to lake formation multiproxy evidence indicates that precipitation increases intermittently recharged fluvial systems within the region leading to lake expansion in distal fan zones conversely decreased precipitation led to reduced channel flow lake contraction and a shift to saline conditions these findings are in contrast to the many other palaeoclimatic records from arabia which suggest that during mis 3 the latitudinal position of the monsoon was substantially further south and did not penetrate the peninsula additionally the occurrence of increased rainfall at this time challenges the notion that the climate of arabia following mis 5 was too harsh to permit the further range expansion of indigenous communities

a 2000 year lichen snowkill chronology for the colorado front range usa measurements of rhizocarpon subgenus rhizocarpon thalli in fixed area 100 m 2 sample plots at 295 randomly selected localities above timberline in the colorado front range suggest six episodes of widespread shallow lichen snowkill during and immediately following the audubon glacial interval recolonization of lichen free areas began in cal ad 210 375 570 700 1025 and 1255 in contrast to the little ice age when snowkill was restricted to narrow bands peripheral to modern late lying snowpatches audubon snowkill destroyed all crustose lichens in more than 90 of the study area heavy april or may snowstorms occurring after redistribution of snow by wind had diminished are thought to have been responsible cool cloudy summers and warm subnivean winter temperatures may also have been involved audubon snowkill episodes lasted for relatively brief periods and were superimposed on the broader pattern of late holocene climatic change they did not necessarily trigger glaciation or cause geomo

a tsunami deposit at the cretaceous tertiary boundary in texas at sites near the brazos river texas an iridium anomaly and the paleontologic cretaceous tertiary boundary directly overlie a sandstone bed in which coarse grained sandstone with large clasts of mudstone and reworked carbonate nodules grades upward to wave ripple laminated very fine grained sandstone this bed is the only sandstone bed in a sequence of uppermost cretaceous to lowermost paleocene mudstone that records about 1 million years of quiet water deposition in midshelf to outer shelf depths conditions for depositing such a sandstone layer at these depths are most consistent with the occurrence of a tsunami about 50 to 100 meters high the most likely source for such a tsunami at the cretaceous tertiary boundary is a bolidewater impact

little ice age glacial activity in peter lougheed and elk lakes provincial parks canadian rocky mountains dendrochronological lichenometric and i4c studies at 14 glacier sites in peter lougheed and elk lakes provincial parks were used to develop a chronology of little ice age glacial events the earliest indications of glacial activity are represented by moraines deposited prior to the 16th century a major glacial expansion in the 17th century is recorded at three sites where i4c dates show glaciers reached their maximum down valley positions lichenometric dates and tree growth suppression records show a phase of glacial activity early in the 18th century for which there is only sparse morainic evidence most moraines in the area date from a glacial advance culminating in the mid 19th century and moraine formation was complete everywhere by the late 1800 s recessional moraines are rare in the study area and indicate that ice front retreat has been relatively continuous since the 19th century the glacial chronology developed in this work is comparable to that reconstructed for both the main ranges of the canadian rockies and the coast ranges of the southern cordillera resum6 les ctudes dendrochronologique 1ichcnomctrique et radiomktrique au i4c de 14 sites rcalisces dans les parcs provinciaux de peter lougheed et de elk lakes ont servi a ctablir une chronologie des cvbnements glaciaires survenus durant le petit bge glaciaire les plus anciens indices de l activitk glaciaire sont reprcsentcs par les moraines dcposces anttrieurement au xvie sibcle une expansion glaciaire majeure durant le xviie sibcle est enregistrke sur trois sites ou les dates au 14c rcvklent la prksence de glaciers avec leurs positions de progression maximale vers le bas de la vallce les datations fondces sur la 1ichcnomctrie et sur les registres de cessation de la croissance des arbres montrent la prcsence d une phase d activitk glaciaire au debut du xviiie sibcle qui a iaissc peu de dcp8ts morainiques dtcelables la plupart des moraines qui apparaissent dans la rcgion datent d une avancce glaciaire qui avait atteint son apogce d extension au milieu du xixe sikcle et leur construction fut complctce vers la fin des annces 1800 les moraines de rkcession sont rares dans la rcgion ctudik cependant elles indiquent que depuis le xixe sibcle il y a eu un retrait relativement continu du front glaciaire la chronologie glaciaire ktablie dans la prcsente ctude est analogue i celle reconstruite pour les chaines principales des rocheuses du canada et pour le domaine c8tier de la cordillbre mkridionale traduit par la raaction

the little ice age maximum in the southern alps new zealand preliminary results at mueller glacier lichenometric dating studies using the yellow green rhizocarpon subgenus at mueller glacier in the region of mt cook southern alps new zealand reveal a little ice age maximum about ad 1725 1730 differences from previous studies are shown to result from different methods especially the type of mathematical functions used for calculating the lichenometric dating curves previous work also used variable sample sizes distal moraine slopes and to some extent different fixed points schmidt hammer measurements enable the differentiation of little ice age from pre little ice age frontal moraines in the outer glacier foreland and confirm the status of the little ice age as a separate glacier advance among several advances during the holocene

transitional morphology in west deuteronilus mensae mars implications for modification of the lowland upland boundary abstract west deuteronilus mensae which lies along the lowland upland boundary of mars at 45 latitude 345 longitude exhibits both gradational l a rossbacher 1985 in models in geomorphology woldenberg ed pp 343 372 allen unwin boston and fretted terrain r p sharp 1973 j geophys res 78 4073 4083 boundary types to the west the boundary is gradational and to the east it is defined by fretted terrain the two types of boundaries do not merge with one another within the west deuteronilus mensae region however the gradational boundary materials appear to overlap the fretted terrain by about 500 km contacts between units associated with the gradational boundary and the fretted terrain boundary can both be recognized in the region of overlap the fretted terrain can be identified as much as 300 km north of the gradational boundary in this region lowland units associated with the gradational boundary embay canyons of the fretted terrain in a topographically conformal fashion changes in the fretted terrain across the gradational boundary from uplands to lowlands include a reduction of canyon wall slopes and depths such that the fretted terrain north of the gradational boundary appears mantled but not obscured there are at least two major classes of processes which might explain the lateral overlap 1 erosion of stratified upland terrain and 2 deposition of plains materials onto the sloping upland margin and fretted terrain erosion of stratified upland terrain does not adequately explain the plainward decrease in crater densities across the gradational boundary nor is it consistent with evidence that lowland plains material appears to onlap the sloping upland margin in several places of the possible plains emplacement mechanisms eolian deposition would not produce the sharp apparently topographically conformal gradational unit contacts volcanics plains emplacement would not preserve the complex geometry of the underlying fretted terrain sediment deposition in either a liquid or ice covered sea could produce the draped appearance of the fretted terrain outflow channels along the lowland upland boundary particularly those of the circum chryse and west elysium regions may have flooded the northern lowlands to depths of tens to hundreds of meters the gradational unit contacts may represent the shorelines of such a sea the scale of characteristic morphologies along these contacts may require an unfrozen condition of sufficient duration to allow lacustrine style wave erosion and redistribution of material along the contacts our limited understanding of the martian paleoclimate and h 2 o inventories allows the possibility of clement periods in the past and other geological evidence e g small valley networks and outflow channels strongly suggests an extensive role of liquid water

growth rates of rhizocarpon geographicum lichens a review with new data from iceland this paper reviews evidence from previous growth rate studies on lichens of the yellow green species of subgenus rhizocarpon the family most commonly used in lichenometric dating new data are presented from rhizocarpon section rhizocarpon thalli growing on a moraine in southern iceland over a period of 4 33yr measurements of 38 lichen thalli between 2001 and 2005 show that diametral growth rate dgr mmyr 1 is a function of thallus size growth rates increase rapidly in small thalli 50 mm diameter mean dgr in southern iceland between 2001 and 2005 was 0 64 mm yr 1 sd 0 24 the resultant growth rate curve is parabolic and is best described by a third order polynomial function the striking similarity between these findings in iceland and those of armstrong 1983 in wales implies that the shape of the growth rate curve may be characteristic of rhizocarpon geographicum lichens the difference between the absolute growth rate in southern iceland and wales ca 66 faster is probably a function of climate and micro environment between the two sites these findings have implications for previous lichenometric dating studies namely that those studies which assume constant lichen growth rates over many decades are probably unreliable british geological survey natural environment research council copyright 2006

latent outflow activity for western tharsis mars significant flood record exposed observations permitted by the newly acquired mars observer laser altimeter data have revealed a system of gigantic valleys northwest of the huge martian shield volcano arsia mons in the western hemisphere of mars northwestern slope valleys nsvs these features which generally correspond spatially to gravity lows are obscured by veneers of materials including volcanic lava flows air fall deposits and eolian materials geologic investigations of the tharsis region suggest that the system of gigantic valleys predates the construction of arsia mons and its extensive associated lava flows of mainly late hesperian and amazonian age and coincides stratigraphically with the early development of the outflow channels that debouch into chryse planitia similar to the previously identified outflow channels which issued tremendous volumes of water into topographic lows such as chryse planitia the nsvs potentially represent flooding of immense magnitude and as such a source of water for a northern plains ocean

eustatic and climatic controls on the development of the wahiba sand sea sultanate of oman aeolian sand sea accumulations can serve as valuable archives of climate change in continental environments the wahiba sand sea is situated at the northern margin of the area presently affected by indian summer monsoon circulation and it records environmental changes associated with this major climatic boundary over the last 160 000 years the internal stratigraphy and evolution of the sand sea is investigated using a combination of outcrop borehole seismic and luminescence data proximity to the indian ocean means that the sand sea succession shows the influence of sea level changes on the sedimentary architecture and composition of the dune deposits during the last two glacial periods low global sea level was associated with a high input of bioclastic grains reflecting the significance of subaerially exposed shelf areas as one of the main sources of aeolian sediment the onset of aeolian sediment transport and deposition was related to the breakdown of stabilizing vegetation during arid periods that equate with sea level lowstands the preservation of aeolian sediments by the formation of supersurfaces and associated palaeosoils took place during times of increased wetness and elevated groundwater tables this interplay of constructive and destructive periods greatly influenced the sedimentary architecture oscillations of wet and dry periods between 160 000 and 130 000 years and 120 000 105 000 years ago are attributed to the evolution of a wet aeolian system younger periods of aeolian deposition around and after the last glacial maximum were characterized by dry aeolian conditions no soil horizons developed during these times

reduced early holocene moisture availability in the bayan har mountains northeastern tibetan plateau inferred from a multi proxy lake record abstract a late glacial and holocene lake sediment record from the northeastern tibetan plateau was investigated using ostracod and geochemical analysis after lake koucha was established about 16 cal ka bp oligohaline conditions gradually converted to mesohaline conditions about 10 cal ka bp clearly suggesting that the water body was a closed basin lake from about 10 cal ka bp the salinity of the lake rose continuously until hyperhaline levels were reached about 7 5 cal ka bp this increase in salinity was accompanied by a falling lake level extreme rainfall and flooding events in a generally dry climate hit the shallow saline lake around 8 5 cal ka bp causing a unique thin gravel containing layer within the continuous fine grained lake sediments the age control of our record does not allow us to correlate this event exactly to the widely recorded 8 2 cal ka bp event however the recovered sediments from lake koucha provide strong evidence that climate changes around 8 5 cal ka bp had significant environmental implications in northeastern tibet after about 7 3 cal ka bp the available moisture significantly increased causing a continuous salinity decline until the present day freshwater conditions of a through flow lake were established about 6 5 cal ka bp in lake koucha this major shift from a shallow saline to a deeper freshwater lake was probably accompanied by a fundamental change from a macrophyte dominated to a phytoplankton dominated lake a slight reduction in available moisture in comparison to the periods before and afterward was recorded between 4 3 and 2 0 cal ka bp in phase with numerous records from monsoonal asia the reconstructed overall change in moisture availability from dry conditions before about 7 3 cal ka bp to wetter conditions afterwards contradicts most palaeoclimate records from the tibetan plateau and its surroundings which show that wetter conditions in the early holocene were replaced by drier and probably cooler conditions in the mid and late holocene however in the semi arid region of lake koucha with a mean annual precipitation of about 500 mm the insolation driven strengthened monsoon in the early holocene may have resulted in a temperature rise and higher evaporation rates which outweighed the increase in precipitation and therefore led to significantly lower moisture availability our record provides further evidence for a regionally non uniform response of the available moisture evolution to the overall monsoonal signal in the holocene climate history of central asia

on the accuracy of lichenometric dates an assessment based on the little ice age moraine sequence of nigardsbreen southern norway families of lichenometric dating curves are constructed using four historically dated moraine ridges on the glacier foreland of nigardsbreen jostedalsbreen ice cap southern norway a further 20 little ice age moraine ridges are dated in terms of median predicted dates derived from the families of curves four approaches are used to assess the accuracy of the median predicted dates 1 the extent to which the dates form a temporal sequence 2 the extent to which they agree with local independent evidence of glacier variations 3 the extent to which dates agree when the moraine sequences on the two sides of the glacier foreland are dated separately and 4 the extent to which they agree when section rhizocarpon is differentiated from lichens of the rhizocarpon subgenus as a whole it is concluded that under conditions favourable for lichenometric dating median predicted dates have attained an accuracy of 10 on the little ice age timescale realistic error limits are considered to be of the o

limits to lichenometry abstract lichenometry is a straightforward and inexpensive method for dating holocene rock surfaces the rationale is that the diameter of the largest lichen scales with the age of the originally fresh rock surface that it colonised the success of the method depends on finding the largest lichen diameters a suitable lichen growth model and a robust calibration curve recent critique of the method motivates us to revisit the accuracy and uncertainties of lichenometry specifically we test how well lichenometry is capable of resolving the ages of different lobes of large active rock glaciers in the kyrgyz tien shan we use a bootstrapped quantile regression to calibrate local growth curves of xanthoria elegans aspicilia tianshanica and rhizocarpon geographicum and report a nonlinear decrease in dating accuracy with increasing lichen diameter a bayesian type of an analysis of variance demonstrates that our calibration allows discriminating credibly between rock glacier lobes of different ages despite the uncertainties tied to sample size and correctly identifying the largest lichen thalli our results also show that calibration error grows with lichen size so that the separability of rock glacier lobes of different ages decreases while the tendency to assign coeval ages increases the abundant young

rhizocarpon calibration curve for the aoraki mount cook area of new zealand development of rhizocarpon growth curve from the aoraki mount cook area of new zealand provides a means to assess little ice age glacier behaviour and suggests approaches that have wider application employing a sampling strategy based on large populations affords the oppor tunity to assess which of various metrics e g single largest average of five largest mean of an entire population best characterise rhizocarpon growth patterns the 98 quantile from each population fitted with a quadric curve forms a reliable representation of the growth pattern since this metric does not depend on the original sample size comparisons are valid where sample strategy must be adapted to local situations or where the original sample size differs for the aoraki mount cook area a surface 100 years old will have a 98 quantile lichen diameter of 34 3 mm whereas a 200 year old surface will have a lichen diameter of 73 7 mm in the southern alps constraints from the age range of calibration points the flattening of the quadric calibration curve and ecological factors limit the useful age range to approximately 250 years copyright 2005 john wiley sons ltd

episodic flood inundations of the northern plains of mars throughout the recorded history of mars liquid water has distinctly shaped its landscape including the prominent circum chryse and the northwestern slope valleys outflow channel systems and the extremely flat northern plains topography at the distal reaches of these outflow channel systems paleotopographic reconstructions of the tharsis magmatic complex reveal the existence of an europe sized noachian drainage basin and subsequent aquifer system in eastern tharsis this basin is proposed to have sourced outburst floodwaters that sculpted the outflow channels and ponded to form various hypothesized oceans seas and lakes episodically through time these floodwaters decreased in volume with time due to inadequate groundwater recharge of the tharsis aquifer system martian topography as observed from the mars orbiter laser altimeter corresponds well to these ancient flood inundations including the approximated shorelines that have been proposed for the northern plains stratigraphy geomorphology and topography record at least one great noachian early hesperian northern plains ocean a late hesperian sea inset within the margin of the high water marks of the previous ocean and a number of widely distributed minor lakes that may represent a reduced late hesperian sea or ponded waters in the deepest reaches of the northern plains related to minor tharsis and elysium induced amazonian flooding

lichenometric dating of slope movements nant ffrancon north wales abstract over the last 50 years frequent debris flows on the oversteepened slopes crossed by the main a5 road in nant ffrancon north wales have presented a significant traffic hazard this study uses two approaches to lichenometry to date earlier debris flows the first approach provides dating estimates based on size age correlations of the lichen rhizocarpon geographicum subspecies prospectans growing in two local churchyards the correlations supplied a growth rate of 1 47 mm year 1 for the species over a 140 year period with a delay before colonization of 18 years remeasurement of the same lichens after a 4 25 year interval confirmed the growth and colonization rates in the churchyards the second lichenometric approach based on population size frequency distributions with size increments dated using the churchyard growth rate provided controls for the nant ffrancon study site with peaks in rhizocarpon population size frequency distributions correlating with debris flow dates recorded by gwynedd council highways department circumstantial evidence supporting adoption of the growth rate on the nant ffrancon slopes was also supplied by data from archival and meteorological sources the lichenometric dating estimates suggest that these slopes have a history of periodic debris flows covering at least the last 110 years with major flows occurring in the 1890s followed by further flows in the early decades of the twentieth century

reconstruction of the main parameters of old large earthquakes in soviet central asia using the paleoseismogeological method abstract the paleoseismogeological method has been improved on the basis of the frequent occurrence of recent seismogenic dislocations in soviet central asia the possibilities are studied and methods for reconstructing epicentral zones and determining the magnitude and age of large earthquakes in the past are proposed worldwide and regional scales of magnitude determination by dislocations are compared on the basis of concrete data new methods of age determination are cited examples are given in which parameters of previously unknown large paleoearthquakes at the pamirs tien shan boundary zone are studied the first for soviet central asia experience in map making for paleoseismodislocations and paleoearthquakes in one of the seismically active and dangerous areas in soviet central asia is described the existing limitations of the method are analysed

a 350 000 year summer monsoon multi proxy stack from the owen ridge northern arabian sea five summer monsoon proxies from the northern arabian sea are combined using stacking and principal components analysis pca to create two very similar multi proxy records of summer monsoon variability the five individual proxies all respond to monsoon variability but are largely independent in terms of the processes that complicate their interpretation as summer monsoon indicators e g preservation dissolution diagenesis sediment reworking as such stacking and pca average out non monsoon variance yielding a more pure monsoon signal these stacked and pca records hereafter summer monsoon stack and summer monsoon factor allow evaluation of relative monsoon strength through time as well as the relative concentration of variance within orbital bands these two parameters are less reliable when estimated from individual proxy records in fact the summer monsoon factor smf accounts for only 33 of the total variance in the five records suggesting that relative amplitude variations in each individual proxy time series are influenced by non monsoon processes the summer monsoon stack sms and smf are spectrally very similar dominated by variance in the 41 k y obliquity and 23 k y precession bands there is very little variance at the 100 k y eccentricity band associated with large scale changes in global ice volume indeed equally strong monsoons occur in both glacial and interglacial intervals within the 23 k y precession cycle monsoon maxima fall at 121 relative to precession minima june 21 perihelion maximum northern hemisphere nh summer insolation this phase falls midway between 18o minima 78 and december 21 perihelion 180 indicating that two mechanisms exert equal influence in determining the timing of strong summer monsoons within the precession band 1 sensible heating of the asian plateau which is maximized at times of ice volume minima 78 and 2 latent heat export from the southern subtropical indian ocean which is maximized at times of december 21 perihelion 180 the seasonal cycle at december 21 perihelion is characterized by warm southern hemisphere sh summers followed by cold sh winters a combination that preconditions the ocean to export latent heat during the boreal summer monsoon season summer monsoon winds transport this latent heat into asia where it is released during precipitation enhancing the asian monsoon low within the 41 k y obliquity cycle monsoon maxima are in phase with obliquity maxima this indicates that two mechanisms quite similar to those in the precession band influence the timing of strong summer monsoons in the obliquity band 1 sensible heating of the asian plateau but with no ice volume delay and 2 latent heat export from the southern subtropical indian ocean which is maximized at times of obliquity maxima again the seasonal cycle at obliquity maximum is characterized by warm sh summers followed by cold sh winters ideal for maximizing latent heat export during the boreal summer monsoon

hydrodynamic evolution from quartz microtextures of a beach ridge in qinghai lake china abstract beach ridges are landforms that exist on beach shorelines and can supply abundant information regarding palaeoenvironments to better understand the hydrodynamic processes of beach ridges a quartz microtexture analysis was carried out in this study the microtextural features of a total of 1063 quartz grains from seven beach ridge samples and eight reference samples from rivers a dune and a nearby beach were observed and analysed by scanning electron microscopy the qualitative and quantitative results suggest that the quartz microtextures of the beach ridge samples present more fresh surfaces and percussion marks than the river samples but less angularity the upper sequence samples from the beach ridge present higher values of fresh surfaces and percussion marks and lower dissolution than the lower sequence samples a cluster analysis shows that the hydrodynamic conditions of qinghai lake underwent pronounced changes from weak to strong and then to weak at the present time furthermore quantitative analyses indicate that the beach ridge and river sedimentary environments can be distinguished through the microtextural features of the 250 125 m size fraction however more grain size fractions should be observed and analysed to interpret the hydrodynamic conditions the quartz microtextural analysis of beach ridges may be an effective method reflecting the palaeohydrodynamic conditions

speleothem based paleoclimate record from northern oman u th age dating and stable isotope measurements of speleothems from hoti cave in northern oman yield paleoclimate information from the region extending to 125 ka the results 1 provide further confirmation of an early holocene wet period in southern arabia extending from some time prior to 9 7 ka and ending at 6 2 ka 2 demonstrate a second period of wetness closely coinciding with the last interglacial period marine isotope stage mis 5e 3 indicate that during mis 5e southern arabia was considerably wetter than during the early holocene and 4 demonstrate that periods of increased monsoon wind strength based on data from marine sediments do not always coincide with evidence of greatly increased precipitation even from nearby continental areas

macroscopic and microscopic evidence of quaternary glacial features and esr dating in the daweishan mountain area hunan eastern china whether quaternary glaciers existed in the daweishan mountain area is of great significance to the reconstruction of the quaternary environments in the yangtze valley this study investigated the macroscopic and microscopic features of quaternary glacial features in the daweishan mountain area and applied electron spin resonance esr dating to the clay and gravel sediments to determine their age aster gdem with a resolution of 30 m combined with field investigation recognized the glacial landforms in the daweishan mountain area cirques and firn basins were distinguished using a flat index of f l 2d and a length width ratio of g l w scanning electron microscopy sem identified glacial traces on quartz sand grains of the clay and gravel sediments esr dating of 6 sections showed that the sediments were formed in 2 stages 205 262 ka and 377 425 ka equivalent to the late stage and middle stage of the middle pleistocene respectively there were at least 2 glaciations in the daweishan mountain area in the late stage and middle stage of the middle pleistocene the yangtze valley was influenced by a cold trough and promoted glaciations developed in the daweishan mountain area

late pleistocene palaeolake in the interior of oman a potential key area for the dispersal of anatomically modern humans out of africa relict fluvial and lacustrine deposits in the interior of oman near saiwan consist of waterlain breccias with pebble imbrications and current ripples covered by algal laminites containing calcified reeds and charcoal pieces geomorphological evidence suggests that the palaeolake covered a maximum surface of 1400 km2 and had a maximum depth of about 25 m optically stimulated luminescence osl and thermally transferred osl dating indicate that this palaeolake existed sometime between 132 and 104 ka the rich archaeological evidence in the area suggests substantial human occupation possibly at the time when palaeolake saiwan existed interestingly the lithic traditions of the archaeological material show no clear relation to coeval findings from neighbouring areas putting a question mark on the origin of the culture found at saiwan this finding raises questions concerning the origin of the population inhabiting saiwan as the site lies along one possible route for the dispersal of anatomically modern humans out of africa copyright 2011 john wiley sons ltd

the 2011 japanese 9 0 magnitude earthquake test of a kinetic energy wave model using coastal configuration and offshore gradient of earth and beyond abstract based on geological investigations of coastal geometry and stratigraphy offshore gradient variation wave velocity energy and quartz grain microtexture analysis of key sites inundated by tsunamis during the holocene we have developed a postulated model that could be used to assess modern and ancient onshore environmental conditions during tsunami emplacement given that tsunami waves can travel up to 900 km h the kinetic energy of the wave is determined by frictional release on the offshore slope to seabed nearshore sand and sediment supply and coastal geomorphology specifically coast linearity or embayments that constrict wave energy with gentle offshore gradients and relatively linear coastlines the kinetic energy of the tsunami is decreased by friction with the seabed and radiated outward along the coast thus producing reduced flooding of the affected coast and fewer collisions of entrained grains in contrast steep offshore gradients reduce friction to mere milliseconds of wave impact and embayments specifically narrow coastal constrictions increase wave energy both of which increase on land run up heights and importantly to our proposed model grain collision effects damage to quartz grains deposited by tsunamis along coastal extents ranges from slight on linear coasts with gentle offshore gradients to highly resurfaced mineral surfaces on coasts with steep offshore gradients and narrow embayments our model can be further tested through collection analyses and comparison of quartz grains in relatively low and high energy environments of the recently tsunami impacted northeastern coast of japan for example the location of the fukushima nuclear plant along a linear coastline with a less steep offshore gradient may have attenuated the energy of the incoming wave and thus yielding less resurfaced grains when compared to the coastline located to the north of sendai city where coastal embayments of variable size coupled with steep offshore gradients would produce higher energy waves of greater magnitude as attested by greater penetration inland with considerable loss of life and property damage and resulting highly deformed grain surfaces the model could be applicable for assessing modern and ancient coastal environmental conditions on earth and postulated ancient marine conditions on the red planet

dendrochronology and lichenometry colonization growth rates and dating of geomorphological events on the east side of the north patagonian icefield chile this paper highlights the importance for dating accuracy of initial studies of delay before colonization for both trees and lichens and tree age below core height particularly in recently deglaciated terrain where colonization and growth rates may vary widely due to differences in micro environment it demonstrates for the first time how dendrochronology and lichenometry can be used together in an assessment of each other s colonization and growth rates and then cross correlated to provide a supportive dating framework the method described for estimating tree age below core height is also new the results show that on the east side of the north patagonian icefield in the arco and colonia valleys nothofagus age below a core height of 112 cm can vary from 5 to 41 years and delay before colonization may range from a maximum of 22 years near water to a minimum of 93 years on the exposed flanks of the arenales and colonia glaciers tree age plus colonization delay supplied a maximum growth rate of 4 7 mm year for the lichen placopsis perrugosa and lichen colonization is estimated to take from 2 5 to approximately 13 years a minimum lichenometric date of 1883 was estimated for an ice formed trimline at the junction of the arenales and colonia glaciers and a maximum dendrochronological date of 1881 for a water formed trimline in the arco valley tree and lichen ages around the valley suggest that a glacial outburst drained the 1881 high level lake releasing approximately 265 million cubic metres of water repeated flooding with a minimum of 38 high lake levels is suggested by horizontal sediment lines on the arco valley walls and moraine flanks dating confirmed diminishing flood levels with a last minor flood in 1963 the wider significance of the work is that it should produce more accurate dating of recent glacier fluctuations around the north patagonia icefield an area where dated reference surfaces are extremely scarce

a record of holocene climate change from lake geochemical analyses in southeastern arabia lacustrine sediments from southeastern arabia reveal variations in lake level corresponding to changes in the strength and duration of indian ocean monsoon iom summer rainfall and winter cyclonic rainfall the late glacial holocene transition of the region was characterised by the development of mega linear dunes these dunes became stabilised and vegetated during the early holocene and interdunal lakes formed in response to the incursion of the iom at approximately 8500 cal yr bp with the development of c3 dominated savanna grasslands the iom weakened ca 6000 cal yr bp with the onset of regional aridity aeolian sedimentation and dune reactivation and accretion despite this reduction in precipitation the lake was maintained by winter dominated rainfall there was a shift to drier adapted c4 grasslands across the dune field lake sediment geochemical analyses record precipitation minima at 8200 5000 and 4200 cal yr bp that coincide with bond events in the north atlantic a number of these events correspond with changes in cultural periods suggesting that climate was a key mechanism affecting human occupation and exploitation of this region

proportion of glacially to fluvially induced quartz grain microtextures along the chitina river se alaska u s a abstract certain micrometer scale fractures or microtextures on grain surfaces are the result of specific transport processes accordingly these transport induced microtextures are used to infer depositional setting in ancient deposits multiple transport histories complicate the microtextural record because modification of grain surfaces can reduce or eliminate the signal of earlier transport episodes this study utilizes scanning electron microscopy to analyze surface microtextures to assess the role of fluvial overprint on glacially derived grains along 188 km of the proglacial chitina river se alaska results indicate that occurrence frequency of glacially induced microtextures i e straight and curved grooves deep troughs and crescentic gouges negatively correlates to distance downstream yet these microtextures persist in every sample conversely occurrence frequency of fluvially induced microtextures i e v shaped cracks and edge rounding positively correlate to distance downstream at least in the chitina river watershed the ratio of fluvially to glacially induced microtextures f g ratio generally records physiographic variation including increase in fluvial signal after a major tributary confluence and decrease downstream from the intersection of valley glaciers these results suggest that analysis of quartz grain microtextures in ancient fluvial deposits can be used to infer glacial influence when other diagnostic sedimentologic indicators of glaciation are lacking other potential uses for the proxy may exist but need to be assessed after other modern proglacial systems are studied including 1 estimates of distance to paleo ice margins using the respective downstream trends of glacially or fluvially induced microtextures and 2 paleogeography of ancient glacio fluvial systems through f g ratio analysis

impact tsunami eltanin employing classical tsunami theory and elementary assumptions about the initial shape of impact cavities we compute tsunami from the eltanin asteroid collision at 2 15 ma an eltanin impactor 4 km in diameter would have blown an initial cavity as deep as the ocean and 60 km wide into the south pacific and delivered a 200 300 m high tsunami to the antarctic peninsula and the southern tip of south america 1200 1500 km away new zealand 6000 km distant would have met 60 m waves generalizing these results to other size impactors we fit simplified tsunami attenuation laws to maximum tsunami heights extracted from the full wave calculations if eltanin was 1 km in diameter instead of 4 km its waves would have been at least five times smaller an asteroid the size of chicxulub 10 km diameter had it fallen into water deeper than 1000 m would have sent a 100 m tsunami out to 4000 km distance even if shoaling amplifications are neglected r 2002 elsevier science ltd all rights reserved

geochemical evidence for abrupt changes in relative strength of the arabian monsoons during a stadial interstadial climate transition the occurrence and propagation of abrupt climate change between the high and low latitudes has become an important focus of paleoclimatic and paleoceanographic research the causes of abrupt change have significant implications for understanding future manifestations of similar forcings under late holocene anthropocene boundary conditions of particular interest are signals indicative of sub millennial scale climate change in the sub tropics of similar magnitude and frequency to those recorded in greenland ice cores earlier research in the arabian sea has highlighted the sensitivity of sedimentary organic carbon and nitrogen isotope measurements for recording the state of the sw monsoon and associated arabian sea oxygen minimum zone in this study we exploit the unprecedented fidelity of the sedimentary 15n record to identify a 20 cm interval at odp site 723 containing a stadial inter stadial interval between 43 42 kyr bp we employ sedimentary nitrogen isotopes chlorin pigment and alkenone abundances major and minor element analyses of highly resolved 2 mm 10 yr samples across this interval to compare a comprehensive multi proxy data set to understand a the processes contributing to the 15n signal in the longer records of denitrification and b the associated climatic events especially the relative intensity of summer and winter monsoons at these times a lack of evidence for bioturbation in excess of our 2 mm sampling resolution facilitates decadal scale oceanographic and climatic reconstructions using a four component flux dilution model we show that the deposition of carbonate decreased in parallel with an increase in total organic matter flux from stadial to inter stadial time this interval is also marked by a significant drop in lithogenic dust accumulation analogous to a similar decrease noted during deglaciation in the western arabian sea combined with alkenone u37k derived estimates for sea surface temperature sst we conclude that the climatological shift from stadial to inter stadial conditions at low latitudes was characterized by repeated switches in mean monsoon state approximately every 200 yr the winter monsoon was the dominant mode during maximum stadial conditions conversely the summer monsoon was dominant during maximum interstadial like conditions however each interval was separated by a distinct inter monsoon mode indicated by a higher continental dust flux but warmer sst proxy records for changing bottom water oxygenation show near identical results down to the mm scale but hint at increased export production leading the onset of anoxia during the stadial inter stadial transition the coherence of all sedimentary signals depicts a wholesale reorganization of the arabian sea climate and marine ecosystem over approximately 200 years a period that may be associated with monsoon modulation by small oscillations in solar irradiance

tectonic evolution of the japanese island arc system abstract growth of the japanese arc system which has mainly taken place along the continental margin of asia since the permian is the result of subduction of the ancient pacific ocean floor backarc basin formation in the tertiary shaped the present day arc configuration the neotectonic regime which is characterized by strong east west compression has been triggered by the eastward motion of the amur plate in the quaternary the tectonic evolution of the japanese arc system includes formation of rock assemblages common in most orogenic belts because the origin and present day tectonics of these assemblages are better defined in the case of the japanese arc system study of the system provides useful insight into orogenesis and continental crust evolution

lichen dating of coseismic landslide hazards in alpine mountains abstract studies of rockfalls and block slides provide insight about seismic shaking hazards in alpine mountains subject to earthquakes large samples of the longest axis of the largest lichen on each block can be used to identify regional landslide events lichen size distributions for many sites cluster consistenly at the same sizes the coseismic rockfall lichenometry model can be used to 1 date and locate prehistorical earthquakes 2 document regional frequency of earthquakes and 3 describe regional patterns of seismic shaking determination of colonization time great growth phase and especially uniform phase rates of lichen growth are essential for dating regional landslide events rocks that tumble downhill during historical earthquakes allow accurate calibration of the growth rate for rhizocarpon subgenus rhizocarpon these plentiful fresh substrates are dated to their day of formation an initial calibration of uniform growth rate based on historical and tree ring dated landslides was fine tuned by assigning earthquake dates to mean values of lichen size peaks for regional rockfall events that increase in abundance towards epicenters of historical earthquakes calibration for each new site is unnecessary in the southern alps of new zealand and in the sierra nevada of california because several species of yellow rhizocarpons within each climatic region have constant growth rates that are independent of altitude or substrate lithology

a holocene tsunami deposit in eastern scotland a thin regionally extensive laterally persistent sand layer identified within the holocene coastal sequences of eastern scotland dated to 7000 years bp is suggested to be a tsunami deposit the likely source of the tsunami wave is the earthquake induced second storegga slide on the norwegian continental slope at least 750 km northeast of the deposit

marine target craters on mars an assessment study observations of impact craters on earth show that a water column at the target strongly influences lithology and morphology of the resultant crater the degree of influence varies with the target water depth and impactor diameter morphological features detectable in satellite imagery include a concentric shape with an inner crater inset within a shallower outer crater which is cut by gullies excavated by the resurge of water in this study we show that if oceans large seas and lakes existed on mars for periods of time marine target craters must have formed we make an assessment of the minimum and maximum amounts of such craters based on published data on water depths extent and duration of putative oceans within contacts 1 and 2 cratering rate during the different oceanic phases and computer modeling of minimum impactor diameters required to form longlasting craters in the seafloor of the oceans we also discuss the influence of erosion and sedimentation on the preservation and exposure of the craters for an ocean within the smaller contact 2 with a duration of 100 000 yr and the low present crater formation rate only 12 detectable marine target craters would have formed in a maximum estimate with a duration of 0 8 gyr as many as 1400 craters may have formed an ocean within the larger contact 1 meridiani with a duration of 100 000 yr would not have received any seafloor craters despite the higher crater formation rate estimated before 3 5 gyr on the other hand with a maximum duration of 0 8 gyr about 160 seafloor craters may have formed however terrestrial examples show that most marinetarget craters may be covered by thick sediments ground penetrating radar surveys planned for the esa mars express and nasa 2005 missions may reveal buried craters though it is uncertain if the resolution will allow the detection of diagnostic features of marine target craters the implications regarding the discovery of marine target craters on mars is not without significance as such discoveries would help address the ongoing debate of whether large water bodies occupied the northern plains of mars and would help constrain future paleoclimatic reconstructions

tsunami sedimentary facies deposited by the storegga tsunami in shallow marine basins and coastal lakes western norway sedimentary successions in small coastal lakes situated from 0 to 11 m above the 7000 year bp shoreline along the western coast of norway contain a distinctive deposit very different from the sediments above and below the deposit is interpreted to be the result of a tsunami inundating the coastal lakes an erosional unconformity underlies the tsunami facies and is traced throughout the basins with most erosion found at the seaward portion of the lakes the lowermost tsunami facies is a graded or massive sand that locally contains marine fossils the sand thins and decreases in grain size in a landward direction above follows coarse organic detritus with rip up clasts here termed organic conglomerate and finer organic detritus the tsunami unit generally fines and thins upwards the higher basins 6 11 m above the 7000 year shoreline show one sand bed whereas basins closer to the sea level 7000 years ago may show several sand beds separated by organic detritus these alternations in the lower basins may reflect repeated waves of sea water entering the lakes in basins that were some few metres below sea level at 7000 years bp the tsunami deposit is more minerogenic and commonly present as graded sand beds but also in some of these shallow marine basins organic rich facies occur between the sand beds the total thickness of the tsunami deposit is 20 100 cm in most studied sites an erosional and depositional model of the tsunami facies is developed

holocene and pleistocene pluvial periods in yemen southern arabia arabia is an important potential pathway for the dispersal of homo sapiens out of africa yet because of its arid to hyper arid climate humans could only migrate across southern arabia during pluvial periods when environmental conditions were favorable however knowledge on the timing of arabian pluvial periods prior to the holocene is mainly based on a single and possibly incomplete speleothem record from hoti cave in northern oman additional terrestrial records from the arabian peninsula are needed to confirm the hoti cave record here we present a new speleothem record from mukalla cave in southern yemen the mukalla cave and hoti cave records clearly reveal that speleothems growth occurred solely during peak interglacial periods corresponding to marine isotope stages mis 1 early to mid holocene 5 1 5 3 5 5 eemian 7 1 7 5 and 9 of these humid periods highest precipitation occurred during mis 5 5 and lowest during early to middle holocene

monitoring the variations of the socotra upwelling system during the last 250 kyr a biogenic and geochemical approach abstract a combination of changes in the species composition of the radiolarian populations and in the sediment chemical composition content and mass accumulation rates of carbonate organic carbon and selected major and trace elements with special attention paid to ba is used to reconstruct the variations in upwelling activity over the last 250 kyr in the socotra gyre area somali socotra upwelling system nw indian ocean in the socotra gyre core md 962073 at 10 n the variations in upwelling intensity are reconstructed by the upwelling radiolarian index uri while the thermocline surface radiolarian index tsri testifies to productivity variations during non upwelling intervals despite an origin related both to marine and terrigenous inputs the geochemical records of organic carbon silica and trace elements ba p cu and zn normalized to al are controlled by the variations in surface paleoproductivity the data indicate a continuous increase in upwelling intensity during the last 250 kyr with a maximum activity within the mis 3 while high productivity periods in between the upwelling seasons occurred both during glacial and interglacial intervals a comparison of our data with published observations from another gyre of the somalian upwelling area located at 5 n in the somali gyre area shows differences regarding periods of upwelling activity and their geochemical imprint three hypotheses are proposed to explain these differences 1 changes in the planktonic community resulting in more silica rich deposits in the socotra gyre and more carbonate rich deposits in the somali gyre that are controlled by differences in the source water of the upwelling 2 a more important terrigenous input in the southern gyre and 3 a different location of the sites relative to the geographic distribution of the upwelling gyres and hydrologic fronts

accurate surface exposure dating with lichens lichenometry accurately dates exposure times of glacial moraines and landslides when measuring the longest axis of the largest crustose lichen on many blocks as demonstrated by numerous examples in sweden the sizes of rhizocarpon subgenus rhizocarpon describe five pulses of glacial moraine creation in 120 yr six historic california earthquakes between ad 1800 and 1906 caused many landslides that constrain lichen growth as linear with a dating accuracy of 0 5 yr crustose lichen sizes date earthquake created additions to sierra nevada talus with an accuracy of 5 yr the oldest lichen ages are 400 yr for lecanora sierrae 800 yr for lecidea atrobrunnea and 1100 yr for acarospora chlorophana and rhizocarpon subgenus rhizocarpon lichen sizes also record differing spatial attenuation of ground shaking from the magnitude m w 7 9 san andreas earthquake of ad 1857 and the more distant smaller san jacinto ad 1800 earthquake which both caused sierra nevada rockfalls ad 1800 seismic shaking was relatively stronger than that of ad 1857 farther north perhaps expressing stronger love and rayleigh styles of surface waves from the north trending ad 1800 surface rupture that were particularly efficient in causing rockfalls at greater distances

paleoclimatic reconstruction in northern oman based on carbonates from hyperalkaline groundwaters abstract a paleoclimatic reconstruction for the past 35 000 years for northern oman is based on an unusual approach using travertines and fracture calcites associated with hyperalkaline springs high ph groundwaters ph up to 11 9 discharge from the mantle sequence of the oman ophiolite as the product of modern low temperature serpentinization under arid climatic conditions hyperalkaline discharge occurs at the surface uptake of atmospheric co 2 precipitates characteristic laminated travertines accompanied by strong kinetic depletion of 13 c and 18 o pluvial climates supporting a shallow bicarbonate groundwater flow system and vegetation are recorded by fracture calcites with equilibrium stable isotope contents and calcite replaced roots and stems all such carbonates have modern initial 14 c contents allowing radiocarbon dating and paleoclimatic reconstruction for the late pleistocene and holocene our reconstruction shows a dominantly wet late pleistocene up to 19 000 yr b p when a phase of climatic deterioration began leading to a period of hyperaridity which dominated from ca 16 300 to 13 000 yr b p the early holocene pluvial occurred from 12 500 to ca 6500 yr b p and was followed by renewed climatic deterioration and the current phase of hyperaridity comparison of this paleoclimatic reconstruction with that for lacustrine deposits from the a rub al khali of central saudi arabia and the summer insolation driven monsoon record of east africa and the arabian sea is remarkably good

scanning electron microscopy of pleistocene sands from yamal and taz peninsulas ob river estuary northwestern siberia coastal sediments in the ob river estuary of northwestern siberia are considered to have either glacial and or estuarine alluvial origins one school of thought argues for interconnected ice domes on the continental shelf that linked the fenno scandinavian and siberian ice grosswald thesis another school of thought argues for an estuarine alluvial origin danilov vtyermin thesis the key to solving the problem of the origin of these sediments lies in detailed stratigraphic oxygen 18 and scanning electron microscopic sem analysis of sediments both the stratigraphy and sem results support the hypothesis of very limited pleistocene glacial activity on yamal gydan and taz peninsulas the sem analysis points to a vast majority of rounded quartz grains with v shaped percussion microfractures and a great range of preweathered microtextures the sem microtextures support a fluvial origin for the sediments far removed from any glacial source a companion paper in this volume by fred michel discusses the 18o analysis of ground ice in the area

humid periods in southern arabia windows of opportunity for modern human dispersal arabia is a key area for the dispersal of anatomically modern humans amh homo sapiens out of africa given its modern hostile environment the question of the timing of dispersal is also a question of climatic conditions fresh water and food were crucial factors facilitating amh expansions into arabia by dating relict lake deposits four periods of lake formation were identified one during the early holocene and three during the late pleistocene centered ca 80 ca 100 and ca 125 ka favorable environmental conditions during these periods allowed amh to migrate across southern arabia between ca 75 and 10 5 ka arid conditions prevailed and turned southern arabia into a natural barrier for human dispersal thus expansion of amh through the southern corridor into asia must have taken place before 75 ka possibly in multiple dispersals

lichenometric dating science or pseudo science the popular technique of estimating ages of deposits from sizes of lichens continues despite valid criticism and without agreement on range of utility treatment of error and methods of measurement sampling and data handling a major source of error is the assumption that the largest lichen s colonized soon after deposition and will survive indefinitely recent studies on lichen mortality suggest that this assumption is untenable meanwhile the use of growth curves constructed from independently dated substrates is problematic for many reasons but this has not prevented the publication of baseless claims of accuracy and ages that are extrapolated well beyond data experiments indicate that numeric lichenometric ages are not reliable and in general do not advance the cause of quaternary science there are a few studies suggesting reliability and indeed there may be cases where lichens and growth curves actually provide realistic numerical ages but it cannot be foretold which lichen assemblages will provide good ages and which bad ages the logical conclusion is that no assumption of good ages can be made and that it is folly to assign numerical ages to a deposit on the basis of lichen sizes

sedimentation and hydrodynamic processes associated with the tsunami generated by the 1755 lisbon earthquake abstract an unusual sedimentary horizon believed to have been deposited by the tsunami associated with the 1755 lisbon earthquake has been identified at boca do rio in southern portugal this horizon marks a distinct sedimentological and micropalaeontological break from the deposits enclosing it the sedimentary characteristics of the horizon which consists of several distinct sub units vary greatly in both vertical and horizontal section detailed textural analysis through vertical sections of these sub units shows abrupt changes in particle size characteristics the highly variable nature of the horizon appears to be due to rapid variation in the hydrodynamic characteristics of the depositional event the lowermost section of the deposit appears to have been deposited from a highly turbulent water mass which was able to transport gravel sized clasts as well as gravel sized mud balls eroded from underlying material the water mass rapidly lost energy leading to the deposition of predominantly sand silt and clay particles sharp breaks in textural characteristics are likely to be due to changes in current direction caused by wave reflection or swash backwash interference the main sources of sand sized material within the deposit are the seaward barrier beach foredune system the tsunami deposit at boca do rio shares many of the sedimentary characteristics of tsunami deposits from other sites around the world

a comparison of the lichenometric and schmidt hammer dating techniques based on data from the proglacial areas of some icelandic glaciers abstract measurements of rhizocarpon section and schmidt hammer r values are reported from the proglacial geomorphic features on the forelands of the icelandic glaciers of kviarjokull holarjokull and heinabergsjokull oraefi and south vatnajokull sandfellsjokull and oldufellsjokull east m rdalsjokull and bruarjokull eyjabakkajokull and west snaefell north vatnajokull these data are used in reconstructions of patterns of glacier recession since the little ice age maximum and the geomorphic signals of climatic versus non climatic events are discussed age control was obtained from various dated substrates by utilizing historical accounts aerial photographs and grave stones three lichen growth rates are calculated a 0 51 mm a 1 corrected to 0 50 mm a 1 with a colonization lag time of

evaporation precipitation changes in the eastern arabian sea for the last 68 ka implications on monsoon variability 1 variations in sea surface temperature sst 18o of sea water 18ow and salinity were reconstructed for the past 68 ka using a sediment core aas9 21 from the eastern arabian sea eas in order to understand the changes in evaporation and precipitation associated with the monsoon system the mg ca derived sst record varies by 4 c it shows that marine isotope stage mis 4 was warmer than mis 3 that the last glacial maximum was 4 c cooler than the present and that there was a 2 c increase within the holocene mis 4 records higher 18ow and salinity values than mis 2 suggesting variable flow of low salinity bay of bengal flow into the eas during glacial periods the transition from mis 4 to mis 3 was marked with a conspicuous shift from higher to lower 18ow values which reflects a decrease in the evaporation precipitation budget in the eas perhaps due to the strengthening of southwest monsoon monsoon reconstructions based on 18ow reveal that monsoon driven precipitation was higher during mis 3 and mis 1 and was lower during mis 2 and mis 4 this is consistent with earlier monsoon reconstructions based on upwelling indices from the western arabian sea however the amplitude of monsoon fluctuations derived through upwelling indices and 18ow varies significantly which may indicate spatial variability of monsoon rainfall

linking tsunami deposits submarine slides and offshore earthquakes abstract the recognition that many tsunamis are associated with coastal sedimentation has been of great value in the study of tsunamis prehistorically geological investigation of such sediments has resulted in the identification of a series of palaeotsunamis that appear to have taken place in different areas of the world in most cases however it has proved difficult to link former tsunamis to specific source mechanisms studies of modern tsunamis have also faced difficulties in the recognition of the specific source mechanisms for example offshore earthquakes may trigger submarine slides that combine to produce complex patterns of tsunami flooding at the coast

little ice age glacier variations in jotunheimen southern norwvay a study in regionally controlled lichenometric dating of recessional moraines with implications for climate and lichen growth rates a new approach to regional lichenometric dating is developed and applied to little ice age moraine ridge sequences on 16 glacier forelands in jotunheimen southern norway lichenometric dating curves based on the rhizocarpon subgenus are constructed independently for west central and east jotunheimen although there are differences between the subregions a composite regional moraine chronology for jotunheimen identifies 12 episodes of moraine formation in ad 1743 1750 the regional little ice age glacier maximum 1762 1771 1782 1790 1796 1802 1811 1818 1833 1838 1845 1854 1860 1868 1871 1879 1886 1898 1915 1922 and 1927 1934 spatial and temporal patterns in glacier behaviour between the subregions and between jotunheimen and the neighbouring jostedalsbreen are explained in terms of the interaction of annual to decadal variations in summer temperature and winter precipitation glacier advances and moraine formation events driven primarily by winter precipitation variations exhibit subregio

monsoon triggered formation of quaternary alluvial megafans in the interior of oman a vast bajada consisting of coalescing low gradient 0 3 alluvial fans exceeding 100 km in length formed along the southwestern margin of the oman mountains it comprises an old fan sequence of inferred miocene to pliocene age termed barzaman formation diagenetically highly altered to dolomitic clays and a thin veneer of weakly cemented quaternary gravels a combination of remote sensing lithological analyses and luminescence dating is used to interpret the complex aggradation history of the quaternary alluvial fans from the interior of oman in the context of independent regional climate records from satellite imagery and clast analysis four fans can be discerned in the study area while two early periods of fan formation are tentatively correlated to the miocene pliocene and the early pleistocene luminescence dating allows the distinction of five phases of fan aggradation during the middle late pleistocene these phases are correlated with pluvial periods from marine isotope stage mis 11 through 3 when southern arabia was affected by monsoonal precipitation it is concluded that the aggradation of the alluvial fans was triggered by the interplay of increased sediment production during arid periods and high rainfall with enhanced erosion of hillslopes and transport rates during strong monsoon phases however the lack of fine grained sediments bioturbation and organic material implies that although the quaternary fans are sourced by monsoonal rains they formed in a semi arid environment thus it appears that in contrast to the oman mountains the interior was not directly affected by monsoonal precipitation

imprints in silica grains induced during an open channel flow experiment determination of microtextural signatures during aqueous transport abstract the aim of this work is to identify and characterize microtextural signatures in silica glass grains used as analogous to quartz that are produced during aqueous transport at different flow velocities with variable sediment concentrations transport distances and time intervals to achieve this an open channel flow experiment was conducted with a mixture of sand and silica glass microspheres in varying conditions velocity from 0 67 to 1 4 m s duration 1 or 10 minutes distance 0 to 2 5 m and sediment concentration 60 or 80 experimental conditions were used to replicate natural phenomena such as river superficial velocity or coastal swash processes before the experiment the microsphere surfaces were imaged and clear of any microtextural imprint increasing velocity distance and sediment concentration exhibited a strong correlation with higher numbers of surfaces abundantly covered with microtextures of mechanical origin i e craters abrasion marks and v shaped percussion marks sem microphotographs of silica were analyzed and classified to provide examples of the specific microtextures produced during the open channel flow experiment the purpose of the experiment was to characterize surface microscopic signatures in quartz grains replicating hydrodynamic conditions of coastal and fluvial environments the results demonstrated a strong correlation between higher velocities and higher sediment concentrations and a larger presence of microtextural mechanical imprints in the grains analyzed thus demonstrating a clear relation between microtextural imprints and water flow modes these results have important implications for future microtextural works analyzing grain imprints and their relation to sediment transport types an example demonstrated here is that the higher presence of v marks could be used as an indicator of supercritical flow conditions

lichenometric application to historical and subrecent dynamics and sediment transport of a corsican stream figarella river france abstract lichenometry has been applied to blocks canyon walls and terrace deposits a growth curve specific to corsica was made based on information obtained from tombstones old monuments from the genoese occupation of corsica and roman megaliths this allowed us to create a curve going as far back as 2000 years the curve is similar to those developed in mediterranean environments cevennes and eastern pyrenees but is very different from those developed in alpine and arctic regions lichens present on boulders of the bedload allow the time at which the boulders were laid down to be determined the lichenometric study of the figarella shows firstly that there is high stream competence blocks approximately 100 cm wide are moved during the 5 year flood recent important flood events were identified in 1973 and 1869 these correspond well with historical sources other older and much more important floods were also identified this analysis has allowed us to extend the specific streampower curves proposed by costa geol soc am bull 94 1983 986 and williams geogr ann 65a 1983 227 to blocks of more than 2 m wide lichens present on the canyon walls and on terrace sides in the plain allowed the last main incision phase to be dated to the little ice age aerial photograph analysis has shown that the present braided system in the lower course of the river is no longer active

characteristics of recessional moraines at a temperate glacier in se iceland insights into patterns rates and drivers of glacier retreat icelandic glaciers are sensitive to climate variability on short term timescales owing to their north atlantic maritime setting and have been undergoing ice marginal retreat since the mid 1990s recent patterns rates and drivers of ice frontal retreat at skalafellsjokull se iceland are examined using small scale recessional moraines as a geomorphological proxy these small scale recessional moraines exhibit distinctive sawtooth planform geometries and are constructed by a range of genetic processes associated with minor ice margin re advance including i combined push squeeze mechanisms ii bulldozing of pre existing proglacial material and iii submarginal freeze on remote sensing investigations and lichenometric dating highlight sequences of annually formed recessional moraines on the northern and central parts of the foreland conversely moraines are forming on a sub annual timescale at the southeastern skalafellsjokull margin using annual moraine spacing as a proxy for annual ice margin retreat rates imrrs we demonstrate that prominent periods of glacier retreat at skalafellsjokull are coincident with those at other icelandic outlet glaciers as well as those identified at greenlandic outlet glaciers analysis of imrrs and climate data suggests summer air temperature sea surface temperature and the north atlantic oscillation have an influence on imrrs at skalafellsjokull with the glacier appearing to be most sensitive to summer air temperature on the basis of further climate data analyses we hypothesise that sea surface temperature may drive air temperature changes in the north atlantic region which in turn forces imrrs the increase in sea surface temperature over recent decades may link to atmospheric driven variations in north atlantic subpolar gyre dynamics

stratigraphy depositional environments and level reconstruction of the last interglacial lake samra in the dead sea basin in this paper we describe the stratigraphy and sediments deposited in lake samra that occupied the dead sea basin between 135 and 75 ka this information is combined with u th dating of primary aragonites in order to estimate a relative lake level curve that serves as a regional paleohydrological monitor the lake stood at an elevation of 340 m below mean sea level msl during most of the last interglacial this level is relatively higher than the average holocene dead sea 400 30 m below msl at 120 and 85 ka lake samra rose to 320 m below msl while it dropped to levels lower than 380 m below msl at 135 and 75 ka reflecting arid conditions in the drainage area lowstands are correlated with warm intervals in the northern hemisphere while minor lake rises are probably related to cold episodes during mis 5b and mis 5d similar climate relationships are documented for the last glacial highstand lake lisan and the lowstand holocene dead sea yet the dominance of detrital calcites and precipitation of travertines in the dead sea basin during the last interglacial interval suggest intense pluvial conditions and possible contribution of southern sources of wetness to the region

the impact of recent climate change on flooding and sediment supply within a mediterranean mountain catchment southwestern crete greece maas g s macklin m g 2002 the impact of recent climate change on flooding and sediment supply within a mediterranean mountain catchment southwestern crete greece earth surface processes and landforms 27 10 1087 1105

a 9000 year oxygen and carbon isotope record of hydrological change in a small ethiopian crater lake the stable isotope composition of authigenic calcites in a core from lake tilo a small crater lake in the ethiopian rift valley provides a subcentury scale record of lake response to climatic change over the last 8850 14c yrs 9850 cal yrs an unusually high range of 18o and 13c values 15 is attributed in part to major changes in hydrothermal groundwater flux although hydrothermal groundwater influx to the lake was high during the early holocene its flow rate was relatively stable and thus climatically induced changes to the water budget can be inferred from variations in 18o and 13c ratios a major decline in hydrothermal groundwater input from 5500 14c yrs bp increased lakewater residence time and led to substantial increases in 18o and 13c before the mid holocene transition to more arid conditions during the last 2700 14c years diagenetic processes have resulted in extremely varied 18o and 13c values the holocene isotope record from lake tilo challenges the widely held assumpti

a 160 000 year record of dune development and atmospheric circulation in southern arabia aeolian deposits in the wahiba sands sultanate of oman reveal patterns of atmospheric circulation over the past 160 000 years luminescence dating indicates a correlation of dune activity with periods of low global sea level and decreased monsoon intensity evidence from dune orientation and sedimentary structures shows exclusively northbound transport of sand during times of high latitude glaciation these results are in contrast to the current paleocirculation model that assumes an increase of northwesterly winds because of a southward shift of the intertropical convergence zone our results indicate that the circulation pattern during glacial times was comparable to that of the present

a new approach to lichenometry dating single age and diachronous surfaces a new approach to lichenometry based on large samples of the single largest lichen on each boulder is presented on surfaces of uniform age lichen sizes measured in this way are near normally distributed so the mean value can be used in constructing lichenometric dating curves by combining mean values from several sites statistically defined confidence limits can be assigned to predicted dates in a pilot study dates obtained for little ice age moraines of two glaciers in southern norway are consistent with those obtained using other approaches unlike standard lichenometry the new approach can be used to investigate the age frequency of boulders on diachronous surfaces formed by continuous or periodic accretion or disturbance it has been used successfully to access the record of late holocene snow avalanche activity retained on avalanche boulder ramparts in upper jostedalen western norway pilot studies are also presented of its use on a talus slope solifluction lobes and periglacial pattern

use of the geochemical and biological sedimentary record in establishing palaeo environments and climate change in the lake ngami basin nw botswana sediment samples from a continuous 4 6 m profile in the dry bed of lake ngami in nw botswana were analysed for geochemistry and dated using both 14c and tl methods certain units in the profile were found to be diatom rich and these with the geochemical results were used as indicators of high and low lake levels within the basin the lake ngami sediments contain a high proportion of sio2 51 92 5 wt avg 72 4 wt and variable levels of al2o3 2 04 17 2 wt avg 8 88 wt based on elevated al2o3 and organic matter loiorgc results lacustrine conditions occurred at ca 42 ka until 40 ka and diatom results suggest that relatively deep but brackish conditions prevailed at 40 ka the lacustrine sedimentary record was terminated abruptly possibly by tectonic activity at ca 19 ka shallow aerobic turbulent conditions were prevalent but lake levels were at this time increasing to deeper water conditions up until ca 17 ka this period coincides with the late glacial maximum a period of increased aridity in the central southern africa region generally increasing sr ca ratios and decreasing loiorgc and al2o3 from ca 16 to 5 ka suggest decreasing inflow into the basin and declining lake levels based on the enrichment of lree results slightly alkaline conditions prevailed at ca 12 ka diatom results also support shallow alkaline conditions around this time these lake conditions were maintained primarily by local rainfall input as the region experienced a warmer wetter phase between 16 and 11 ka lake levels rose rapidly by 4 ka probably in response to enhanced rainfall in the angolan catchment these results indicate that lake levels in the lake ngami basin are responding to rainfall changes in the angolan catchment area and local rainfall the results confirm that the present day anti phase rainfall relationship between southern africa and regions of equatorial africa was extant during the late quaternary over the angolan highlands and nw botswana

changing moisture sources over the last 330 000 years in northern oman from fluid inclusion evidence in speleothems speleothems from hoti cave in northern oman provide a record of continental pluvial periods over the last 330 000 yr periods of rapid speleothem deposition occurred from 6000 to 10 500 78 000 to 82 000 120 000 to 135 000 180 000 to 200 000 and 300 000 to 330 000 yr ago with little or no growth during the intervening periods during each of these five pluvial periods d values of water extracted from speleothem fluid inclusions dfi are between 60 and 20 vsmow and 18o values of speleothem calcite 18oc are between 12 and 4 to vpdb these values are much more negative than modern rainfall for d or modern stalagmites for 18o previous work on the isotopic composition of rainfall in oman has shown that northern and southern moisture sources are isotopically distinct combined measurements of the d values of fluid inclusion water with calculated 18o values from peak interglacial speleothems indicate that groundwater was predominantly recharged by the southern indian ocean moisture source when the monsoon rainfall belt moved northward and reached northern oman during each of these periods

ancient ocean on mars supported by global distribution of deltas and valleys the climate of early mars could have supported a complex hydrological system analysis of ancient deltaic deposits and valley networks reveals the presence of a planet wide equipotential surface in the northern lowlands indicative of the existence of a vast ocean on mars 3 5 billion years ago

late quaternary chronology of major dune ridge development in the northeast rub al khali united arab emirates the northeastern sector of the rub al khali desert in the eastern united arab emirates uae is dominated by large ne sw trending dune ridges orientated perpendicular to the currently prevailing northwesterly wind regime in this study extensive use has been made of artificially exposed sections through these major dune ridges that reveal internal sedimentary structures and allow an intensive high resolution sampling programme to be carried out here we present the optical dating results for samples from 7 sections the results indicate that dune activity and preservation occurred within the periods 7 3 ka 16 10 ka and 22 20 ka with evidence of earlier preservation during marine oxygen isotope stages mis 3 and 5 with net accumulation rates in the range 2 2 25 m ka 1 in several instances hiatuses in the preserved record of dune accumulation coincide with stratigraphic bounding surfaces visible in the exposed section profiles with associated truncation of internal sedimentary structures caution must be exercised when interpreting such gaps in the recorded accumulation chronologies of these dunes since these may simply constitute phases of low preservation potential rather than phases of low aeolian activity other factors such as sediment supply and availability in relation to sea level dynamics may be significant and are also considered

sorted circles relative age dating and palaeoenvironmental reconstruction in an alpine periglacial environment eastern jotunheimen norway lichenometric and weathering based approaches lichenometric and weathering based techniques are employed in an investigation of the chronology of large scale sorted circles in jotunheimen southern norway comparison of diameter measurements of rhizocarpon geographicum agg with local growth curves and size frequency analysis of lichen population data indicate that all the sorted circles originated prior to the mid eighteenth century little ice age maximum parts of the circle borders appear to have been stable since before the twelfth century although minor disturbances to border clasts were widespread between about ad 1640 and 1740 large proportions of the smaller surface clasts in circle centres have stabilized only since the little ice age maximum the thickness of surface weathering rinds and measurements of rock surface hardness r values obtained using a schmidt hammer indicate long periods of clast exposure in circle borders at least 1500 years at some sites and shorter exposure times for central clasts despite difficulties in inf

possible ancient giant basin and related water enrichment in the arabia terra province mars a circular albedo feature in the arabia terra province was first hypothesized as an ancient impact basin using viking era information to test this unpublished hypothesis we have analyzed the viking era information together with layers of new data derived from the mars global surveyor mgs and mars odyssey mo missions our analysis indicates that arabia terra is an ancient geologic province of mars with many distinct characteristics including predominantly noachian materials a unique part of the highland lowland boundary a prominent paleotectonic history the largest region of fretted terrain on the planet outflow channels with no obvious origins extensive exposures of eroded layered sedimentary deposits and notable structural albedo thermal inertia gravity magnetic and elemental signatures the province also is marked by special impact crater morphologies which suggest a persistent volatile rich substrate no one characteristic provides definitive answers to the dominant event s that shaped this unique province collectively the characteristics reported here support the following hypothesized sequence of events in arabia terra 1 an enormous basin possibly of impact origin formed early in martian history when the magnetic dynamo was active and the lithosphere was relatively thin 2 sediments and other materials were deposited in the basin during high erosion rates while maintaining isostatic equilibrium 3 sediments became water enriched during the noachian period and 4 basin materials were uplifted in response to the growth of the tharsis bulge resulting in differential erosion exposing ancient stratigraphic sequences parts of the ancient basin remain water enriched to the present day

how wet is wet precipitation constraints on late quaternary climate in the southern arabian peninsula it is generally recognized that the southern arabian peninsula has had two wet periods in the late quaternary to quantify wet a 28 000 year old capillary surface associated with a paleowater table was mapped and used as a surrogate for the water table in a ground water model analysis of this model suggests 1 4 mm year 1 of recharge is necessary to support the water table at the mapped elevations during the wet period climatic relations between rainfall and recharge in arid areas infer that annual rainfall during this wet period was approximately 200 50 mm year 1 or approximately five times the present rate

glacier change from the early little ice age to 2005 in the torngat mountains northern labrador canada abstract the glaciers of the torngat mountains of northern labrador are the southernmost of the canadian arctic and the easternmost of continental north america currently 195 small mountain glaciers cover an area in excess of 24 km2 confined mostly to small cirques and upland depressions using a combination of field and remote sensing methods this study reconstructs and dates the areal extent of torngat glaciers at their neoglacial maximums enabling the first assessment of regional glacier change over the past several centuries mapped glacier paleomargins n 165 are compared to current 2005 glaciers and ice masses showing a 52 5 reduction in glacier area with at least 11 former glaciers altogether disappearing glacier change is spatially homogenous and independent of most geographic and topographic factors however glacier elevation and glacier size mitigated total change previously established lichen growth stations were revisited and growth rates recalculated based on 30 year long records enabling the construction of locally derived low and high altitude lichen growth curves using growth rates and in situ lichen measurements the retreat from maximum neoglacial moraine extents are suggested to have occurred between a d 1581 and 1673 these findings indicate a similar magnitude of post lia retreat to mountain glaciers elsewhere yet a much earlier timing 200 years of retreat than other glaciers in the eastern canadian arctic though no definitive answer explaining this discrepancy is presented evidence suggests that regional climate dynamics and the importance of solar radiation for torngat glaciers may play an important role in local glacierization

surface textural analysis of quartz grains by scanning electron microscopy sem from sample preparation to environmental interpretation abstract surface microtextures on quartz grains provide an insight into the sedimentary history of clastic sediments not only information on the depositional environment is provided but also in some cases successive sedimentary cycles can be recognised sample preparation and sem imaging are the initial and therefore crucial steps in the study of microtextures a sample preparation procedure using 15 hydrochloric acid and 50 g l tetrasodium pyrophosphate solutions removes most of the grain coatings and adhering particles the study of microtextures on 1300 quartz grains from a wide variety of environments was complemented with the reference works and atlases krinsley and doornkamp 1973 le ribault 1977 higgs 1979 mahaney 2002 to construct an interpretation scheme allowing to differentiate between fluvial marine eolian glacial and diagenetic alteration environments based on microtextures in a case study the known littoral setting of two samples was confirmed by using the interpretation scheme for quartz microtextures furthermore successive reworking of the grains in eolian and intertidal environments was recognised by presenting the research of microtextures from starting point to interpretation new researchers may find this review a useful and practical introduction into the technique

glacier variations in breheimen southern norway dating little ice age moraine sequences at seven low altitude glaciers moraine sequences in front of seven relatively low altitude glaciers in the breheimen region of central southern norway are described and dated using a multi proxy approach to moraine stratigraphy lichenometric dating based on the rhizocarpon subgenus is used to construct a composite moraine chronology which indicates eight phases of synchronous moraine formation ad 1793 1799 1807 1813 1845 1852 1859 1862 1879 1885 1897 1898 1906 1908 and 1931 1933 although the existence of a few cases of older moraines possibly dating from earlier in the eighteenth or late in the seventeenth centuries cannot be ruled out by lichenometry schmidt hammer r values from boulders on outermost moraine ridges suggest an absence of holocene moraines older than the little ice age twenty three radiocarbon dates from buried soils and peat associated with outermost moraines at three glaciers tverreggibreen storegrovbreen and greinbreen also indicate that the little ice age glacier maximum was the neoglacial maximum at most if not all glaciers several maximum age estimates for the little ice age glacier maximum range between the fifteenth and seventeenth centuries with the youngest from a buried soil being ad 1693 a pre little ice age maximum cannot be ruled out at greinbreen however where the age of buried peat suggests the outermost moraine dates from ad 981 1399 at variance with the lichenometric evidence glaciofluvial stratigraphy at tverreggibreen provides evidence for minor glacier advances about ad 655 963 and ad 1277 1396 respectively copyright 2003 john wiley sons ltd

orbital insolation forcing of the indian monsoon a motor for global climate changes abstract both modern and ancient indian summer monsoons are driven by transequatorial pressure differences directly coupled with the insolation difference between the northern and southern subtropical hemispheres a high resolution record of upwelling and dust flux from the western arabian sea resembles an insolation based indian summer monsoon index this index and the observed monsoonal climate variations share major elements on the orbital obliquity and precessional band with the specmap marine oxygen isotope record representing global ice volume the long term evolution of the index mirrors almost exactly the insolation changes at 65 n showing that the forcing of low latitude climate variability has a structure similar to that of the insolation forcing in the high northern latitudes moreover insolation forcing in the low latitudes directly controls atmospheric processes in the african indian and asian monsoon being responsible for a huge amount of transequatorial water vapour and therefore latent heat transport millennial scale variability of the monsoonal climate is concentrated at periodicities near 1100 1450 1750 and 2300 years these cycles are not strictly periodic but occur in bands with specific activity phases and amplitude increases during warm stages and interstadials for the 1100 and 1750 yr cycles whereas the 1450 yr cycle dominates the cold intervals