seasonal variability of sea surface height in the south china sea observed with topex poseidon altimeter data topex poseidon altimeter measurements along 16 ground tracks in the south china sea from november 1992 to october 1997 were used to observe the seasonal variability of sea surface height ssh in winter november december january and february the ssh images are generally characterized by a sea surface tilting downward toward the east high sea levels on the western side of the sea have a little monthly change and a low minus sea level peak is centered in the northeastern deep basin in spring march and april a single high sea level peak hp centered at 14 n 114 e becomes a dominant feature in summer may june july and august the ssh images show a sea surface tilting downward toward the west the hp moves from 14 n 114 e in may to the northwest of luzon island in july low sea levels are centered in the offshore of the northern and southern vietnamese coast in fall september and october the appearance of an eastward low sea level jet in the western basin between 12 and 14 n constitutes a major feature of the ssh images these results are comparable with previous results and drifter measurements

optically stimulated luminescence age controls on late pleistocene and holocene coastal lithosomes north carolina usa luminescence ages from a variety of coastal features on the north carolina coastal plain provide age control for shoreline formation and relative sea level position during the late pleistocene a series of paleoshoreline ridges dating to marine isotope stage mis 5a and mis 3 have been defined the kitty hawk beach ridges on the modern outer banks yield ages of 3 to 2 ka oxygen isotope data are used to place these deposits in the context of global climate and sea level change the occurrence of mis 5a and mis 3 shorelines suggests that glacio isostatic adjustment gia of the study area is large ca 22 to 26 m as suggested and modeled by other workers and or mis 3 sea level was briefly higher than suggested by some coral reef studies correcting the shoreline elevations for gia brings their elevation in line with other sea level indicators the age of the kitty hawk beach ridges places the holocene shoreline well west of its present location at ca 3 to 2 ka the age of shoreline progradation is consistent with the ages of other beach ridge complexes in the southeast usa suggesting some regionally contemporaneous forcing mechanism

evidence for a transgressive barrier within a regressive strandplain system implications for complex coastal response to environmental change clastic depositional strandplain systems have the potential to record changes in the primary drivers of coastal evolution climate sea level and the frequency of major meteorological and oceanographic events this study seeks to use one such record from a southern brazilian strandplain to highlight the potentially complex nature of coastal sedimentological response to small changes in these drivers following a 2 to 4 m highstand at ca 5 8 ka in southern brazil falling sea level reworked shelf sediment onshore forcing coastal progradation smoothing the irregular coastline and forming the 5 km wide pinheira strandplain composed of ca 500 successive beach and dune ridges sediment cores grab samples and 11 km of ground penetrating radar profiles reveal that the strandplain sequence is composed of well sorted fine to very fine quartz sand since the mid holocene highstand the shoreline prograded at a rate of ca 1 to 2 m yr 1 through the deposition of a 4 to 6 m thick shoreface unit a 1 to 3 m thick foreshore unit containing ubiquitous ridge and runnel facies and an uppermost beach and foredune unit however the discovery of a linear 100 m wide barrier ridge with associated washover units a 3 to 4 m deep lagoon and 250 m wide tidal inlet within the strandplain sequence reveals a period of shoreline transgression at 3 3 to 2 8 ka during the otherwise regressive developmental history of the plain the protected nature of pinheira largely buffered it from changes in precipitation patterns wave energy and fluvial sediment supply during the time of its formation however multiple lines of evidence indicate that a change in the rate of relative sea level fall probably due to either steric or ice volume effects may have affected this coastline thus whereas these other potential drivers cannot be fully discounted this study provides insights into the complexity of decadal scale to millennial scale coastal response to likely variability in sea level change rates

annual layers revealed by gpr in the subsurface of a prograding coastal barrier southwest washington u s a abstract the southwest washington coastline has experienced extremely high rates of progradation during the late holocene subsurface stratigraphy preserved because of progradation and interpreted using ground penetrating radar gpr has previously been used successfully to document coastal response to prehistoric storm and earthquake events new gpr data collected at ocean shores washington suggest that the historic stratigraphy of the coastal barrier in this area represents a higher resolution record of coastal behavior than previously thought gpr records for this location at 200 mhz reveal a series of gently sloping seaward dipping reflections with slopes similar to the modern beach and spacings on the order of 20 45 cm field evidence and model results suggest that thin 1 10 cm possibly magnetite rich heavy mineral lags or low porosity layers left by winter storms and separated by thick 20 40 cm summer progradational sequences are responsible for generating the gpr reflections these results indicate that a record of annual progradation is preserved in the subsurface of the prograding barrier and can be quantified using gpr such records of annual coastal behavior where available will be invaluable in understanding past coastal response to climatic and tectonic forcing

rapid flooding of the sunda shelf a late glacial sea level record the increase in sea level from the last glacial maximum has been derived from a siliciclastic system on the tectonically stable sunda shelf in southeast asia the time from 21 to 14 thousand calendar years before the present has been poorly covered in other records the record generally confirms sea level reconstructions from coral reefs the rise of sea level during meltwater pulse 1a was as much as 16 meters within 300 years 14 6 to 14 3 thousand years ago

controls on fan development evidence from fan morphometry and sedimentology sierra nevada se spain abstract we have studied the morphology and the morphometric relations between alluvial fans and drainage basins in a bajada system including more than 20 coalescent fans developed since the late pleistocene as a result of the recent uplift of the sierra nevada betic cordillera spain three allocycles of tectonic origin were recognised across which there is a clear evolution from debris flow to sheet flow dominated fans in connection with a decrease in the volume of fines available in the source areas the larger volume of accommodation space created by higher tectonic subsidence in the northern sector favoured vertical accumulation of sediment with the appearance of less elongated fans in the rest of the system where subsidence is less more elongated fans appear with the development of incised channels and irregular distribution of sediment in depositional lobes this involves the appearance of markedly asymmetric transverse profiles as well as lengthy recurrence between the sedimentation events on particular sectors of the fans where headward eroding gullies develop the lithology of the source area where intensely fractured rocks are found is responsible for an important sediment supply and a significant degree of clast sorting from the source area consequently a weak longitudinal trend in particle size can be recognised which influences the predominance of longitudinal constant slope profiles and anomalous relations between both fan area and fan slope and their drainage areas recent intense tectonic activity has caused the appearance of abnormally low slopes in upper sectors of some catchments where mass flows are trapped and the fans present a subsequently higher proportion of sheet flows recent piracy phenomena can be recognised in some of the drainage basins which indicate rejuvenation of the source area in which case the fan presents a rapid increase in the proportion of mass flows with the development of a segmented longitudinal profile due to the recent nature of the processes the morphometric relations in the fan fed by the basin affected by capture do not coincide with the other fans in the area

holocene sea level changes in the indo pacific holocene sea level reconstructions exist from many locations in the indo pacific region despite being a large geographical region the nature of holocene sea level change is broadly similar in all locations differences do exist however in the timing and magnitude of the mid holocene high stand mhhs and the nature of late holocene sea level fall across the region when the indo pacific is subdivided into smaller regions these discrepancies do not disappear and in some cases the discrepancies are large within a single coastline it is clear from this analysis that the fundamental criteria to produce accurate local relative sea level curves are hardly ever met there are serious problems associated with the correct interpretation of sea level indicators and their relationship to mean sea level and with the quality of age determinations a consistent methodology throughout the indo pacific for the analysis of sea level data is lacking future sea level analysis from far field locations must involve the application of a consistent methodology in order to allow meaningful comparison between studies this should help to resolve the ongoing debate about the magnitude and timing of the mid holocene high stand and the nature of late holocene sea level fall across the region

sea level changes in the tectonically stable malay thai peninsula abstract the malay thai peninsula is part of sundaland a geological region of relative crustal stability therefore the positions of old shorelines of the past 20 000 years or so can be considered to indicate positions of actual past sea levels over 200 shoreline indicators at positions below as well as above present sea level have been radiocarbon dated these dated positions indicate that prior to 6 ka the sea rose from at least 90 m below present sea level at rates that initially amounted to 15 mm year and later became 6 mm year at ca 6 ka the rising sea surpassed its current position and at ca 5 ka it reached 5 m during this maximum marine inundation the peninsula was narrower since the low coastal plains did not yet exist in the period following this maximum transgression the available shoreline data indicate that regional sea level subsided through a series of fluctuations that were characterized by amplitudes of 2 m and periods of about 2000 years the peaks and troughs of the fluctuations became progressively lower the latest peak was at about 1 7 m or 0 7 m above present high tide a few hundred years ago the cause of these fluctuations is not yet known but the trend suggests that in the near future regional sea level may subside at annual rates between 1 5 mm and 2 mm this rate of descent is 25 to 30 of the estimated rate of sea level rise that may result from global warming in other words for the malay thai peninsula the effect of sea level rise on account of manmade greenhouse gases will be partly compensated by actual subsidence of regional sea level

the equation of state of a molten komatiite 1 shock wave compression to 36 gpa the equation of state eos of an initially molten 1550 c komatiite 27 wt mgo was determined in the 5 36 gpa pressure range via shock wave compression shock wave velocity u s and particle velocity u p kilometers second follow the linear relationship u s 3 13 0 03 1 47 0 03 u p based on a calculated density at 1550 c 0 bar of 2 745 0 005 g cm 3 this u s u p relationship gives the isentropic bulk modulus k s 27 0 0 6 gpa and its first and second isentropic pressure derivatives k s 4 9 0 1 and k s 0 109 0 003 gpa 1 the calculated liquidus compression curve agrees within error with the static compression results of agee and walker 1988 to 6 gpa but is less dense than their extrapolated values at higher pressures we determine that olivine fo 94 will be neutrally buoyant in komatiitic melt of the composition that we studied near 8 2 gpa clinopyroxene would also be neutrally buoyant near this pressure liquidus garnet majorite may be less dense than this komatiitic liquid in the 20 24 gpa interval however pyropic garnet and perovskite phases are denser than this komatiitic liquid in their respective liquidus pressure intervals to 36 gpa liquidus perovskite may be neutrally buoyant near 70 gpa at 40 gpa the density of shock compressed molten komatiite would be approximately equal to the calculated density of an equivalent mixture of dense solid oxide components this observation supports the model of rigden et al 1989 for compressibilities of liquid oxide components using their theoretical eos for liquid forsterite and fayalite we calculate the densities of a spectrum of melts from basaltic through peridotitic that are related to the experimentally studied komatiitic liquid by addition or subtraction of olivine at low pressure olivine fractionation lowers the density of basic magmas but above 13 14 gpa this trend is reversed all of these basic to ultrabasic liquids are predicted to have similar densities at 13 14 gpa and this density is approximately equal to the density of the bulk preliminary reference earth model mantle in this pressure range this suggests that melts derived from a peridotitic mantle may be inhibited from ascending from depths greater than 400 km

tectonic and climatic controls of alluvial fan size and source catchment relief the geometries of alluvial fans and their upland catchments subject to known rates of basin subsidence v and upland precipitation p respectively are compared with predictions from a quantitative analysis of an idealized landscape we find that the dimensionless ratio v p explains systematic trends in relative fan size and source catchment relief previously reported from environmentally wide ranging regions worldwide and contributes to the interpretation of recently reported observations of fan like phenomena on mars

recent coastal evolution and sea level rise setiu wetland peninsular malaysia abstract sea level reconstructions based on foraminiferal assemblage data are common for temperate salt marsh settings in comparison the widespread mangrove swamps of equatorial to subtropical settings have received considerably less attention due to enhanced taphonomic loss of specimens extensive bioturbation abundant infaunal foraminifera and irregular intertidal topography the tropics however provide the best possible estimate of eustatic function and thus are important for testing earth ice models in this paper we use foraminiferal data in a chronologic framework provided by optically stimulated luminescence radiocarbon and pb 210 age estimates to determine coastal evolution and rates of sea level rise in the setiu wetland of northeastern peninsular malaysia on the western margin of the southern south china sea over the past ca 200 years foraminiferal data from three surface transects across fringing mangrove swamps were used to interpret four cores from mid to high mangrove swamp settings patterns of foraminiferal distribution were determined by correspondence analysis canonical correspondence analysis and detrended canonical correspondence analysis of dead assemblage data we used weighted averaging as the transfer function model to reconstruct sea level curves for the cores and to provide a composite reconstruction for the last ca 200 years based on one c 14 estimate sea level rose during the 19th century at 1 26 mm yr 1 the rate increased to 3 2 0 6 mm yr 1 around 1900 ce roughly coincident with rate increases recorded globally however the 20th century rate in the setiu wetland is considerably greater than that of global estimates ca 1 8 mm yr 1 for this period rates of sea level rise in the gulf of thailand immediately to the north of the setiu wetland determined from gps corrected tide gauge data and multi satellite altimetry are geographically variable but also greater than the global rate the data from the setiu wetland provide the first foraminifera based sea level reconstruction of the past few hundred years from the southeastern south china sea scs and they represent the first time the early 20th century increase in rate of sea level rise has been identified using proxy foraminiferal data in an equatorial setting

the sudbury structure controversial or misunderstood the origins of the sudbury structure and associated igneous complex have been controversial most models call for a major impact event followed by impact induced igneous activity although totally igneous models are still being proposed much of the controversy is due in our opinion to a misunderstanding of the size of the original sudbury structure by analogy with other terrestrial impact structures the spatial distribution of shock features and huronian cover rocks at the sudbury structure suggest that the transient cavity was 100 km in diameter which places the original final structural rim diameter in the range of 150 200 km theoretical calculations and empirical relationships indicate that the formation of an impact structure of this size will result in 104 km3 of impact melt more than sufficient to produce a melt body the size of the igneous complex present volume 4 8 103 km3 for the igneous complex to be an impact melt sheet it must have a composition similar to that of the target rocks evidence for this has been presented previously for sr and nd isotopic data which suggest a crustal origin here we also present new evidence from least squares mixing models that the average composition of the igneous complex corresponds to a mix of archean granite greenstone terrain with possibly a small component of huronian cover rocks this is a geologically reasonable mix based on the interpreted target rock geology and the geometry of melt formation in an impact event of this size the igneous complex is differentiated which is not a characteristic of previously studied terrestrial impact melt sheets this can be ascribed however to its great thickness and slower cooling that large impact melt sheets can differentiate has important implications for how the lunar samples and the early geologic history of the lunar highlands are interpreted if this working hypothesis is accepted namely that both the sudbury structure and the igneous complex are impact in origin then previous hybrid impact igneous hypotheses can be discarded and the sudbury structure can be studied specifically for the constraints it provides to large scale cratering and the formation of basin sized multiring impact structures

a below the present late holocene relative sea level and the glacial isostatic adjustment during the holocene in the malay peninsula abstract this study has reconstructed the holocene relative sea level history in the relatively tectonically stable malay peninsula with two specific objectives quantifying the sea level indicative meanings of mangrove sediments and producing new high quality sea level index points in this study a wetland on the east coast of the peninsula was extensively surveyed the elevational relationship between habitat zones and their pollen and diatom assemblages was established and a number of indicative meanings were precisely quantified for this wetland this quantified relationship is extrapolated to other coastal sites of the peninsula for re calibration of previously published mangrove based sea level data the reconstructed sea level history from the new and re calibrated data demonstrates a period of rapid sea level rise at a rate of 15 8 3 9 mm a between 10 500 cal a bp at 35 0 4 3 m and 9000 cal a bp at 14 2 1 6 m the rate of rising sea level was gradually reduced to zero from 9000 to 5000 cal a bp and by the end of this period the relative sea level reached a highstand of c 3 3 0 2 m over the past 5000 years relative sea level fell to its lowest point at 0 6 0 1 m by 800 cal a bp this far field sea level history has been driven by the global ice volume change and glacial isostatic adjustment and it matches well with the modelled ice volume equivalent sea level

controls on fan depositional processes in the schist ranges of the southern alps new zealand and implications for debris flow hazard assessment sixteen morphometric and vegetation cover variables associated with 32 debris flow and 28 fluvial fans and their basins in the schist ranges of the southern alps of new zealand are examined the results show statistically significant differences in the area length planimetric shape relief ratio melton s ruggedness r and forest and total vegetation cover between debris flow and fluvial basins and in the apex and toe elevations area and upper and average axial gradients between debris flow and fluvial fans all of these variables except the apex and toe elevations of the fans reflect differences between debris flow and fluvial processes and environmental controls on them discriminant analysis indicates that the relief ratio and melton s r of the basin and upper and average gradients of the fan axis are able to correctly classify debris flow and fluvial fans with almost equally good results obtained by employing only a pair of variables either basin relief ratio and upper fan gradient or basin melton s r and basin shape the lower thresholds at debris flow sites and upper thresholds at fluvial sites for the relief ratio and melton s r of the basin and upper and average gradients of the fan are identified and these as well as the mean values of these variables show significant differences from fans in nearby sedimentary ranges of the southern alps with important implications for the assessment of debris flow hazard on fans fan gradient is found to be closely associated with basin size area and length at debris flow sites but with basin ruggedness relief ratio at fluvial sites both fan types show a weak association between their size and the size of the contributing basin

controls on modern tributary junction alluvial fan occurrence and morphology high atlas mountains morocco abstract modern tributary junction alluvial fans cone shaped depositional landforms formed in confined valley settings were analysed from a 20 km long reach of the dades river in the distal part of the fold thrust belt region in the south central high atlas mountains of morocco here a deeply dissected network of ephemeral tributary streams and a perennial trunk drainage characterised by an arid mountain desert climate are configured onto a folded and thrust faulted mesozoic sedimentary sequence out of 186 tributary streams only 29 16 generated alluvial fans at their tributary junctions the fan generating catchments possess higher relief longer lengths lower gradients and larger areas than nonfan generating catchments whilst geologically fan generating catchments are underlain by folded steeply dipping weak bedrock conducive to high sediment yield tributary junction fans are built from debris flow or fluvial processes into open or confined canyon trunk valley settings the proximity of the perennial trunk drainage combined with the valley morphology produces lobate or foreshortened trimmed fan forms analysis of fan area gradient process catchment area relief length gradient and tributary valley width variables reveals weak morphometric relationships highlighted by residual plots that show dominance of smaller and lower gradient than expected fan forms these morphometric relationships can be explained by interplay between the catchment and trunk drainage geology morphology climate and flood regime that are combined into a conceptual build and reset model ephemeral tributary junction fans develop progressively during annual localised winter spring storm events attempting to build towards a morphological equilibrium however the fans never reach an equilibrium morphological form as they are reset by rare 10 year large floods along the river dades that are linked to regional incursions of atlantic low pressure troughs the model highlights the spatial and temporal variability of tributary junction fan building and illustrates the connectivity coupling importance of such features in dryland mountainous terrains

lunar ferroan anorthosites and mare basalt sources the mixed connection global overturn of a hot gravitationally unstable lunar mantle immediately following the solidification of a magma ocean and essentially complete by 4 4 ga explains several characteristics of lunar petrology lunar mare basalt sources are inferred to be depleted in europium and alumina these depletions are consensually attributed to complementary plagioclase floating from a magma ocean however the connection cannot be so simple and direct in contrast to the mare basalt source parent magma the ferroan anorthosite parent magma was more evolved by virtue of its lower mg fe ratio and ni abundances although less evolved in its poverty of clinopyroxene constituents flat rare earth pattern and lower incompatible element abundances the europium anomaly in mare sources is inferred to be present at 400 km depth too deep to have been directly influenced by plagioclase crystallization massive overturning of the post magma ocean mantle would have carried down clinopyroxene ilmenite and phases containing fractionated rare earths europium anomalies and some heat producing radionuclides these phases contributed to deep mare basalt sources upward moving phases would have been magnesian mafic minerals their immediate melting on pressure release contributed the magnesian suite of plutonic norites and troctolites that post date the anorthosites in the highlands crust

sedimentology and morphodynamics of a barrier island shoreface related to engineering concerns outer banks nc usa abstract forty nine vibracores were collected from a barrier island shoreface following 12 4 years of biweekly profile surveying the sedimentologic architecture of the shoreface was linked to time series elevation change and profile shape to determine relationships between morphodynamics facies development erosional processes profile closeout and cross shore transport the modern shoreface mass which erosionally overlies a tidal inlet associated complex attains a maximum thickness of 3 4 m below the beach to middle profile before pinching out seaward between 9 and 12 m depth concave erosional surfaces overlain by cross stratified fine to medium sand and gravel make up most of the lower half of the shoreface prism below the beach through middle profile reflecting longshore trough incision and subsequent current dominated aggradation at the landward margin gravel rich laminae record episodic seaward progradation of beach surfaces over coarse inner trough settings seaward a parallel laminated fine sand facies dominates the upper part of the prism recording intermittent shoal zone buildup including trough filling under high velocity plane bed conditions similarly a bioturbated parallel laminated fine to very fine sand facies makes up the entire prism below the outermost lower ramp sector again indicating buildup under high velocity conditions however accretion of the lower ramp results from major storms that cause trough scour along landward locations and simultaneous displacement of fine sand onto the lower ramp conversely lower ramp erosion typically occurs during less energetic conditions as sediment is slowly returned shoreward causing inner shoreface buildup close spacing of major storms during some years led to net progradation of the shoreface the upper and lower limits of surveyed elevation change ule and lle repeatedly develop similar limit profile shapes over shoreface accretion erosion cycles the ule reflects accretion maxima resulting from beach bar and lower ramp buildup the lle and lower sedimentologic limit lls along the inner 250 to 300 m of the active shoreface are a product of storm trough scour down to a maximum depth of 5 5 m below the lower ramp facies the lle and lls are primarily products of less energetic wave erosion down to 5 m shoreward and 9 m offshore depths the lle closely matches the lls documenting that 90 of the shoreface prism was reworked during the 12 4 year period whereas actual ages for erosional events indicate a potential of 2 to 4 years for complete reworking of the shoreface mass textural distribution indicates net long term transport direction and loci of deposition for different sized material the coarsest material is concentrated at landwardmost locations and well sorted fine to very fine sand at seaward locations medium sand to gravel tends to remain within the trough zone even during extreme storm events the ule and lle also represent the upper and lower limits for profile closure events a location of about 4 5 m depth at 300 to 350 m from shoreline marks the boundary between inner profile and lower ramp associated closure events the boundary between trough associated and lower ramp facies and the lower ramp morphologic break all of which correspond to the juncture between longshore current and shoaling wave dominated zones the lower ramp zone of closure is a zone of seaward decreasing storm transport in which fine to very fine sand is the typical bedload material

warmer or cooler late holocene marine palaeoenvironments interpreting southeast australian and brazilian sea level changes using fixed biological indicators and their δ18o composition abstract relic inter tidal assemblages of sessile organisms which are referred to as fixed biological indicators fbis are shown to be useful proxies for late holocene climatic and environmental changes as well as direct indicators of short term fluctuations in sea level a detailed comparison of change in the inter tidal assemblages of two southern hemisphere sites at comparable latitudes port hacking new south wales south east australia and the laguna imbituba region of southern brazil indicates periods of marked similarities in the timing and nature of changes at 5200 3800 cal years bp and differences after 2400 cal years bp there is sufficient concurrence of cooling phases and falling sea levels to strongly suggest that in some cases global rather than regional forcing factors are at work the value of inter tidal organisms as indicators of changed environments is developed by identifying the past and present distributions of the common marker species tubeworms barnacles and mussels the 18 o content of these extant specimens at port hacking confirmed changes in ocean water temperature and associated sea level behaviour corresponding to invasion or extinction of temperature sensitive species a similar pattern is repeated although in a less marked fashion in the laguna imbituba region of southern brazil

barrier island response to late holocene climate events north carolina usa the outer banks barrier islands of north carolina usa contain a geologic record of inlet activity that extends from ca 2200 cal yr bp to the present and can be used as a proxy for storm activity optically stimulated luminescence osl dating 26 samples of inlet fill and flood tide delta deposits recognized in cores and geophysical data provides the basis for understanding the chronology of storm impacts and comparison to other paleoclimate proxy data osl ages of historical inlet fill compare favorably to historical documentation of inlet activity providing confidence in the technique comparison suggests that the medieval warm period mwp and little ice age lia were both characterized by elevated storm conditions as indicated by much greater inlet activity relative to today given present understanding of atmospheric circulation patterns and sea surface temperatures during the mwp and lia we suggest that increased inlet activity during the mwp responded to intensified hurricane impacts while elevated inlet activity during the lia was in response to increased nor easter activity a general decrease in storminess at mid latitudes in the north atlantic over the last 300 yr has allowed the system to evolve into a more continuous barrier with few inlets

depositional process and alluvial fan drainage basin morphometric relationships near banff alberta canada two distinct types of alluvial fans occur in the bow river valley alberta canada fluvially dominated and debris flow dominated large gently sloping fans dominated by fluvial processes are associated with large and less rugged drainage basins and small rugged basins have produced small steep fans dominated by debris flow processes quantitative analysis demonstrates that strong fan basin morphometric relationships occur despite a short fan history statistical analysis of fan area basin area relationships indicate that debris flow fan areas do not increase in size as quickly as contributing basins the relationship of fluvial fan area to basin area is not statistically significant however this relationship is probably affected by fan erosion examination of fan slope to basin ruggedness relationships indicates that fan slope increases more rapidly than basin ruggedness for both fan types this is likely related to non linear discharge and sediment size effects on fluvial fans and reworking of larger fan surfaces by fluvial processes on debris flow fans

on the origin of late holocene sea level highstands within equatorial ocean basins abstract late holocene sea level highstands of amplitude 3 m are endemic to equatorial ocean basins these highstands imply an ongoing and moderate sub mm yr sea level fall in the far field of the late pleistocene ice cover that has long been linked to the process of glacial isostatic adjustment gia clark et al 1978 mitrovica and peltier 1991 coined the term equatorial ocean syphoning to describe the gia induced sea level fall and they provided the first physical explanation for the process they argued that water migrated away from far field equatorial ocean basins in order to fill space vacated by collapsing forebulges at the periphery of previously glaciated regions we provide a complete physical explanation for the origin of equatorial ocean syphoning and the associated development of sea level highstands using numerical solutions of the equation that governs meltwater redistribution on spherical viscoelastic earth models in particular we separate the total predicted sea level change into contributions associated with ice and meltwater loading effects and by doing so isolate a second mechanism that contributes significantly to the ocean syphoning process ocean loading at continental margins induces a levering of continents and a subsidence of offshore regions that has also long been recognized within the gia literature walcott 1972 we show that the influx of water into the volume created by this subsidence produces a sea level fall at locations distant from these margins indeed over the major ocean basins that is comparable in amplitude to the syphoning mechanism isolated by mitrovica and peltier 1991

analysis of dynamic sedimentary environments in alluvial fans of some tributaries of the upper yellow river of china based on ground penetrating radar gpr and sediment cores abstract there are ten ephemeral tributaries of the yellow river in the inner mongolia of china as their catchments are covered by loose materials and are dominated by an intense interaction between wind and water erosion these tributaries have had a high sediment yield and alluvial fans have been formed at the confluences of the tributaries with the yellow river however there is a lack of understanding in the deposition model of the alluvial fans and the roles of fluvial and aeolian processes in sediment accumulation in this paper we used ground penetrating radar 100 mhz and sediment cores to investigate the sediments in channels and alluvial fans of four out of the ten tributaries radar reflection profiles of sedimentary strata are dominated by horizontal or sub horizontal layers with a large scale showing that the fluvial deposition on the alluvial fans has been dominated by a vertical accretion pattern the reflection features like reflection free inclined reflections discontinuous undulate chaotic sinuous reflections and channel fill exist to a lesser extent a few gpr profiles send signs of intense erosion and the one near the apex of an alluvial fan reveals that erosion had been active likely during the early holocene and the channel position should be relatively fixed the information extracted from this profile and the widely exposed late pleistocene strata in the upper parts of the alluvial fans according to the geological map of the study area indicates that sediment accumulation has been slow in the upper alluvial fans since the early holocene the sediment cores indicate that sedimentary strata under the alluvial fans are mainly composed by sand and silt deposited in a fluvial environment and rarely reworked by wind actions also according to the core data the sediment deposits in the west fans were coarser than those in the east fans likely suggesting that the hydrodynamic force of the western tributaries was stronger than that of the east ones the hydrodynamic environment of the tributaries was usually unstable historically and hyperconcentrated flows might occur with a higher frequency in one of the tributaries in history

pristine lunar glasses criteria data and implications major element analyses of several thousand glasses from all of the apollo landing sites have resulted in the identification of 25 groups of pristine i e volcanic glass the nickel in these pristine glasses is shown to be indigenous not meteoritic contamination and to be correlated with mg the chemical data indicate that these glasses are consistently better candidates for primary magmas than the majority of crystalline mare basalts the pristine glasses support the view that assimilative processes ringwood and kesson 1976 involving two cumulate systems in the differentiated mantle operated during mare petrogenesis the reality of those assimilative interactions is evident by the occurrence of two linear arrays among the chemistries of the glasses data suggest that these cumulate components in the differentiated mantle persist for lateral distances of at least 1000 km and therefore appear to be products of a vast magma ocean that existed early in lunar history alternative hypotheses claiming that the highlands crust and mare source regions were produced by serial magmatism without a magma ocean have not yet considered all of the constraints derived from the pristine glasses

assimilation by lunar mare basalts melting of crustal material and dissolution of anorthite we discuss techniques for calculating the amount of crustal assimilation possible in lunar magma chambers and dikes based on thermal energy balances kinetic rates and simple fluid mechanical constraints assuming parent magmas of picritic compositions we demonstrate the limits on the capacity of such magmas to melt and dissolve wall rock of anorthitic troctolitic noritic and kreep quartz monzodiorite compositions significant melting of the plagioclase rich crustal lithologies requires turbulent convection in the assimilating magma and an efficient method of mixing in the relatively buoyant and viscous new melt even when this occurs the major element chemistry of the picritic magmas will change by less than 1 2 wt diffusion coefficients measured for al2o3 from an iron free basalt and an orange glass composition are 10 12 m2 s 1 at 1340 c and 10 11 m2 s 1 at 1390 c these rates are too slow to allow dissolution of plagioclase to significantly affect magma compositions picritic magmas can melt significant quantities of kreep which suggests that their trace element chemistry may still be affected by assimilation processes however mixing viscous melts of kreep composition with the fluid picritic magmas could be prohibitively difficult we conclude that only a small part of the total major element chemical variation in the mare basalt and volcanic glass collection is due to assimilation fractional crystallization processes near the lunar surface instead most of the chemical variation in the lunar basalts and volcanic glasses must result from assimilation at deeper levels or from having distinct source regions in a heterogeneous lunar mantle

morphotectonics of the northern bogd fault and implications for middle pleistocene to modern uplift rates in southern mongolia abstract assessing the activity of strike slip faults is often facilitated by cumulative offsets of morphological features the december 4th 1957 mongolia earthquake generally referred to as the gobi altai or bogd earthquake had mw 8 1 and created long and complex surface ruptures of c 350 km length along the bogd fault that cuts across the foothills of the gurvan bogd mountains several left laterally and vertically displaced quaternary alluvial fans and morphogenic markers show cumulative offsets allowing for an assessment of the effect of repeated earthquakes and active tectonics on landscape evolution we propose to expand the active tectonic record along this fault up to a middle pleistocene time scale that spans regional climatic fluctuations i e repeated glacial interglacial cycles and hence varying erosional and depositional rates five main drainage areas crosscutting the north ikh bogd segment of the bogd fault were analysed and compared in terms of hypsometry drainage steepness and alluvial fan slope inclination along the mountain front deposits from all drainages form multiple alluvial fan levels that reflect recurring deposition incision cycles previously published ages as well as the spatial distribution of these fan levels suggest that their incision and abandonment is induced by regionally dominant climate fluctuations however the increase of fan slope angles over time and the increased intensity of sub surface folding observed in ground penetrating radar profiles suggests that cumulative tectonic uplift also has a strong impact on alluvial fan morphology estimates of the increase of fan slope angles as a result of cumulative tectonic uplift imply that middle pleistocene to modern vertical slip rates along the north ikh bogd segment of the bogd fault are in the order of 0 9 1 mm yr however much slower vertical slip rates along individual fault segments ranging between 0 06 0 01 mm yr and 0 28 0 07 mm yr indicate that uplift of the ikh bogd plateau occurs as a result of distributed deformation across multiple parallel fault strands within bedrock as well as alluvial fans our results emphasise the importance of regional studies along active faults that take into account the complexity of surface ruptures as well as the occurrence of related structures that can accommodate deformation

influence of lithologic erodibility on alluvial fan area western white mountains california and nevada differences in lithologic erodibility and sediment storage within a drainage basin affect the relationship between alluvial fan area and drainage basin area along the western white mountains large fans are produced by basins underlain by resistant rocks which have steep and narrow trunk stream canyons with little sediment in storage small fans are produced by basins composed of erodible lithologic units which have wider valley floors lower valley side slopes and considerably more sediment stored along trunk stream canyons than is the case in basins underlain by resistant rocks

the ferroan anorthositic suite the extent of primordial lunar melting and the bulk composition of the moon the geochemical bimodality among compositionally pristine lunar rocks is strong evidence that a major component of the moon s crust is fundamentally unrelated to the plagioclase flotation crust that accumulated over the primordial magma ocean the ferroan anorthositic suite fas has all the characteristics expected for a series of magma ocean plagioclase flotation cumulates but we estimate based on mass balance for al2o3 that 30 wt of the crust and 20 wt of the crust s total al2o3 or roughly 15 of the bulk moon al2o3 content assumed to be 3 4 wt was emplaced by postmagma ocean mg suite serial magmatism remelting of plagioclase bearing magma ocean cumulates cannot plausibly account for the late emplacement of al2o3 because the only plagioclase rich cumulates produced by a deep ultramafic magma ocean would have mg ratios too low to engender the mg suite conceivably remelting of garnet rich magma ocean cumulates supplied the late al2o3 but only if the bulk moon al2o3 content is substantially higher than generally assumed high pressures in the magma ocean acted to enhance the py pyroxene pyroxene olivine ratio of the mo cumulates and the al2o3 content of whatever pyroxene formed remelting of pyroxene rich mo cumulates could conceivably have supplied the late mg suite al2o3 to the crust the source region would have to encompass roughly 40 wt of the mantle another possible source for late al2o3 addition is a large portion of the deepest mantle that avoided more than a slight degree of partial melting and thus remained al rich during formation of the magma ocean the source region would have to encompass 20 30 wt of the mantle ascent of diapiric masses from the lowermost mantle would likely coincide with trigger or be triggered by a large scale overturn of the gravitationally unstable mo cumulate pile with concomitant pressure release melting in which case the mg suite parental melts would be derived from a mix of deepest mo cumulates and the even deeper primitive mantle the popular giant impact hypothesis of lunar origin implies an extremely hot beginning for the moon suggesting that the deep interior was either molten or depleted in al2o3 by differentiation in hot protomoons as it formed origin of 30 wt of the moon s crust by postmagma ocean serial magmatism is more consistent with coaccretion models that form the moon without a giant hot impact in any scenario with a large fraction of the crust originating by partial remelting of deep magma ocean cumulates mass balance for al2o3 implies that the bulk moon normative py ratio must be greater than roughly 0 5 i e significantly higher than generally estimated in this respect the moon appears more compositionally similar to chondritic silicates than to the earth s upper mantle

xenolith digestion in large magma bodies xenolith digestion during sinking in a corrosive magma is treated with a surface controlled dissolution relation suggested from recent experiments on silicate crystals the relation is shown to apply to a wide range of dynamical regimes from analog experiments on nacl dissolution in water using this relation xenolith penetration by sinking into magmas is shown to be strongly dependent on xenolith size crystal sinking is unimportant but sinking of meter sized chunks can be a major process of mass and heat transport in planetary scale magma body evolution this evolution cannot be adequately treated with current information

forced regressions in a sequence stratigraphic framework concepts examples and exploration significance sequence stratigraphic concepts suggest that stratal geometries develop and are largely controlled by changes in relative sea level on the shelf lowstand deposits which form during falls and subsequent stillstands of relative sea level can be recognized by the presence of an unconformity at the base the isolated and basinward position relative to the previous shoreline and the abrupt seaward translation of shallow water and shoreline facies into the basin across an unconformity surface this seaward translation of facies and shoreline regression in response to relative sea level lowering is termed a forced regression a forced regression is independent of variations of sediment flux and is in contrast with normal regressions that occur in response to excess sediment flux relative to space available on the shelf i e accommodation forced regressions commonly are associated with a zone of sedimentary bypass subaerial exposure and possible fluvial erosion between the newly formed and preceding shorelines certain shelf sands previously interpreted as offshore or mid shelf sand bodies thus can be reinterpreted as stranded lowstand shorelines associated with forced regressions this alternative interpretation has economic significance insofar as it suggests different subsurface correlations and reservoir geometries with the potential for development of new play types and enhanced recovery in o der fields examples of forced regression can be observed at a variety of scales and ages several such examples include the modern east coulee fan delta and the lower cretaceous viking formation in alberta canada the quaternary rhone delta and the quaternary hudson valley system

western pacific coral δ18o records of anomalous holocene variability in the el nino southern oscillation 1 skeletal oxygen isotope ratios in holocene porites corals from northern papua new guinea record decreases in sea surface temperature sst and rainfall during el nino events threshold analysis of seven fossil coral 18o records spanning the period 7 6 5 4 ka thousand years ago shows 8 12 el nino events century significantly less than the 23 events century recorded by the nino3 4 index the coral reconstructions also show a 15 reduction in el nino event amplitude for 7 6 5 4 ka compared to today which is greater than the suppression given by model studies in contrast large and protracted el nino events are identified for 2 5 1 7 ka taken together the results indicate a non linear atmospheric response to holocene changes in el nino sst anomalies we propose that small changes in tropical sst gradients the positioning of the intertropical convergence zone and the pacific tradewind climatology modify the impact of el nino events on western pacific rainfall

anorthosite assimilation and the origin of the mg fe related bimodality of pristine moon rocks support for the magmasphere hypothesis the lunar magma ocean or magmasphere hypothesis always controversial has required considerable revision in recent years the geochemical bimodality of pristine rocks epitomized by a diagram of na na ca versus mg ratio has led to proposals that a major fraction of the crust the mg rich suite formed as cumulates in numerous intrusions slightly younger than the magmasphere the precise origin of the bimodality has been elusive however one previous suggestion was that na was lost as a volatile before the ferroan anorthosites crystallized from the magmasphere whereas the mg rich intrusives retained all of their original na however this model cannot fully explain the bimodality because the same bimodal pattern is manifested by plotting eu al a ratio of involatile elements versus mg ratio assimilation probably helped to engender the bimodal patterns mass energy balance calculations indicate that large proportions of plagioclase were probably assimilated from the older magmasphere generated ferroan anorthosite crust by most of the mg rich intrusive melts the magmasphere in the absence of assimilation probably did not yield appreciable plagioclase the ferroan anorthosite crust until fractional crystallization of mafic silicates had diminished the melt mg ratio to about 0 42 however assuming identical initial melt composition an mg rich intrusion assimilating ferroan anorthosite and perhaps also a small proportion of urkreep would have reached plagioclase saturation at much higher mg about 0 66 the current version of the magmasphere hypothesis ferroan anorthosites magmasphere flotation cumulates mg rich rocks products of slightly younger localized intrusions appears to be the only plausible mechanism for engendering the mg fe related bimodality

grain size distribution and subsurface mapping at the setiu wetlands setiu terengganu a study was carried out around the lagoon and coastal area of setiu wetlands to determine the general characteristics and grain size distribution of their sediments sediment samples were collected from 39 stations of the lagoon area and 8 stations of the coastal area and were analyzed for their sedimentological characteristics mean sorting skewness and kurtosis the sediment mean size ranged between 0 06 2 52 and 2 12 2 69 phi o for both lagoon and coastal sea bottom sediments respectively generally the sediments in the study area consist mostly of coarse to fine particles the major portions of the sediment are negatively skewed this indicates that the study area is under the influence of the rather strong wave and current action the study also encompassed the geophysical survey that was conducted near the coastal zone of the study area the high resolution seismic sub bottom profiling technique is the standard method employed to map geological features and locate structures below the surface of the seafloor data obtained from seismic records were used to interpret the seismic reflectors three main reflectors layers which consist of the seabed and the seabed multiple were traced using sonar web pro software and the results showed a uniform distribution pattern for all stations surveyed it is envisaged that this method could be an effective way to image the marine subsurface structures thus its use is anticipated in the higher degrees of sedimentary research and marine resource exploration

geologic influences on fluvial hydrology and bedload transport in small mountainous watersheds northern new mexico u s a discharge characteristics in six adjacent mountainous watersheds in northern new mexico u s a vary substantially between basins underlain by different lithologies relatively resistant gneisses and granites underlie two basins drainage areas 43 and 94 km2 that have high unit discharge 0 010 to 0 14 m3s 1 km 2 high bankfull discharge and sustained high discharge less resistant sandstones and shales underlie four basins drainage areas 96 to 215 km2 that have relatively low unit discharge 0 001 to 0 005 m3s 1 km 2 relatively low bankfull discharge and peak discharges that are not sustained as long as those in the crystalline terrane analysis of snowmelt runoff water budgets suggests that three factors control hydrologic conditions in the basins first area elevation distributions appear to control the timing and amounts of water input these distributions probably reflect the erosional resistance of the different lithologies second lithology appears to control runoff production in areas having minor amounts of storage third glacial deposits in headwater regions control discharge duration and timing via storage and return flow releases the amount of return flow released by glacial deposits however is probably controlled by the permeability of underlying bedrock therefore it appears that the duration timing and magnitude of discharge events in the study area are controlled both directly and indirectly by lithology stream power and shear stress estimates derived from bankfull discharge and bed material size data suggest that higher bedload transport rates and larger bedload particle sizes exist in streams draining crystalline rocks than in streams draining sedimentary terrane it appears that source area lithology by controlling discharge production also influences stream power bedload transport capabilities and therefore total amounts of bedload transport

quantifying long term catchment changes of alluvial fan systems in mountain areas affected by uplift significant reorganization of drainage networks can occur through river capture this modification can dramatically affect sediment flux and routing into adjacent sedimentary basins it is thus important to obtain information on rates and direction of changes in catchment areas in such environments this can be achieved where the original precapture catchments can be compared with the postcapture scenario this paper examines three modern mountain catchments from southeast spain that were affected by river capture and that fed relict pliocene pleistocene alluvial fan systems morphometric data have been collated for complete quaternary mountain catchment piedmont fan systems these data are used to establish regressions to determine catchment area and basin relief from a combination of fan characteristics area and gradient these relationships are then used to predict the original catchment characteristics for the three pliocene pleistocene relict fans and compared with the modern catchments to quantify the magnitude and direction of changes which have affected the drainage basins since fan abandonment in the early pleistocene the figures suggest that the catchment areas are responding to regional uplift most significantly by drainage net expansion facilitated by river capture rather than lowering of surface relief as a result sediment routing into the sedimentary basins has been radically altered

holocene evolution of the chan may coastal embayment central vietnam changing coastal dynamics associated with decreasing rates of progradation possibly forced by mid to late holocene sea level changes abstract southeast asian coastal environments are undergoing massive transformations with unprecedented population and infrastructure development these transformations are occurring on a backdrop of intense natural and anthropogenic environmental change which are increasing the risk to the burgeoning coastal population little is known about how central vietnamese coastal environments have changed naturally since the mid holocene sea level highstand and how recent anthropogenic change and sea level variation have affected the coastal system the chan may embayment in central vietnam allows us to examine how recent changes in both anthropogenic development and sea level change have affected the coastline the embayment preserves a series of prograding beach ridges and is subject to intense human pressures with the construction of a large economic and industrial park and expansion of tourist facilities using ground penetrating radar and quartz optical dating we identify a switch from 6000 years of prograding beach ridges to transgressive dunes within the past century resulting in a decreasing rate of beach ridge progradation possibly in the last 100 years the recent modes of sediment deposition through washovers and a transgressive dune indicates that coastal progradation has slowed and might have stopped

tectonic controls on the morphometry of alluvial fans around danehkhoshk anticline zagros iran article i nfo alluvial fans are important landforms where their morphology and morphometry reflect changes in tectonic climate base level and drainage basin characteristics along the margins of tectonically active mountain ranges like the zagros mountains alluvial fans are generally assumed to act as useful landforms for identify ing the level of tectonic activity the purpose of this paper is to evaluate the relationship between active tec tonics and morphometric characteristics of alluvial fans around danehkhoshk anticline in the simply folded belt of zagros morphometric characteristics of alluvial fans such as area fa slope sf length of base bf width length ratio w l radius r sweep angle sa and entrenchment e as well as valley floor width to height ratio vf and strata dips of anticline limbs dal were measured the study area was sub divided into eight tectonic zones and then the mean values of the above mentioned parameters were calculated in each zone result reveals that values of sa bf and e are directly proportional to dal the poor relationships between catchment characteristics slope and area and fan parameters are probably due to extensive karstic landforms of catchments having complex hydrologic systems and hence result in complex catchment fan relations the highly entrenched fans with high sweep angles and long bases are characteristic of tectonically active fronts of danehkhoshk anticline having v shaped valleys higher vf values steep triangular facets and more rotated limbs higher dal values apart from the tectonic control on fan development the fan head entrenchment and negative accumulation spaces on most alluvial fans can be attributed to decreased sediment load and discharge the drier the present day climate regime

holocene sea levels and palaeoenvironments malay thai peninsula southeast asia sedimentological and palynological investigations of great songkhla lakes east coast of the malay thai peninsula southeast asia reveal sedimentary sequences rich in palynomorph assemblages dominated by pollen of mangroves and freshwater swamps compared with other regions in southeast asia the assemblages are of relatively low diversity geochronological data indicate that the great songkhla lakes record one of the earliest mangrove environments in southeast asia 8420 8190 cal yr bp which are subsequently replaced by a freshwater swamp at 7880 7680 cal yr bp owing to the decline of marine influence sea level observations from great songkhla lakes and other areas of the malay thai peninsula reveal an upward trend of holocene relative sea level from a minimum of 22 m at 9700 9250 cal yr bp to a mid holocene high stand of 4850 4450 cal yr bp which equates to a rise of c 5 5 mm yr the sea level fall from the high stand is steady at c 1 1 mm yr geophysical modelling shows that hydroisostasy

interglacial glacial climatic signatures preserved in a regressive coastal barrier southeastern australia abstract regressive barriers persisting in the landscape over interglacial glacial cycles are important repositories of paleoclimatic signatures such as past sea level and regional aridity the gippsland region of victoria contains a multi barrier system formed during past interglacial glacial cycles and the late holocene an extensive series of parallel foredune ridges forming the elongate inner barrier was sampled for luminescence dating with ages indicating deposition ca 125 000 108 000 years ago coinciding with the later phase of the last interglacial lig marine isotope stage mis 5e and the transition to mis 5d ground penetrating radar gpr imaged beach face reflectors within the lig barrier indicate that sea level was within 2 to 3 m of present level during mis 5e in this far field location significant reworking of the barrier system through blowout and parabolic dune activity occurred between 23 000 18 000 years ago corresponding to the last glacial maximum lgm with an estimated 160 000 000 m3 of coastal sediments eroded and redistributed the morphological changes to this coastal barrier over the most recent interglacial glacial cycle mis 5e to present also imply significant landscape instability during the lgm in southeastern australia and are further evidence for extension of the geographical range and intensity of aridity at this time

evidence for ca 7 ka maximum holocene transgression on the peninsular malaysia east coast in situ fossil coral and shelly marine deposits occur up to 50cm above mean sea level in north east peninsular malaysia the fossil reef comprises over 15 coral species and associated molluscs radiocarbon ages of corals range from 7238 to 6909 cal a bp the reef occurs adjacent to bedrock hills that formed a mainland peninsula when the coral was living abundant well preserved fossil molluscs with bivalves commonly articulated occur in ditch tailings from coastal plains flanking these hills landward a sand ridge represents part of the maximum transgression shoreline when alive the fossil coral reef required clear water and full marine conditions seaward of the peninsula the maximum transgression here occurred ca 7 ka with stable environmental conditions persisting long enough for diverse coral reef development assuming a similar tidal range to today relative sea level ca 7 ka would have been between 1 4 and 3m above present between then and ca 6 ka abundant sediment supply resulted in barrier beach construction seaward of the coral reef converting the area to a lagoonal environment unsuitable for coral and burial by muddy deposits assuming that regional relative sea level data indicate maximum holocene highstand up to 5m between 6 and 4 ka are correct then the maximum transgression preceded maximum sea level by at least 1000 years copyright 2014 john wiley sons ltd

holocene coastal response to monsoons and relative sea level changes in northeast peninsular malaysia abstract sedimentological geomorphic and ground penetrating radar gpr data are combined with optically stimulated luminescence data to define the holocene evolution of a coastal system in peninsular malaysia the setiu coastal region of northeast malaysia comprises five geological and geomorphic units representing distinct evolutionary phases of this coastline estimated marine limiting point elevations indicate deposition of an early aggradational shoreline associated with a sea level elevation of 0 1 to 1 7 m mslpmvgd datum between 6 8 ka and 5 7 ka in agreement with previous sea level studies from the malay thai peninsula a hiatus occurs in the record between 5 7 ka and 3 0 ka possibly due to a relative sea level oscillation and shoreline erosion long term relative sea level fall and possible still stands created strandplains that are interrupted by aggradational to transgressive paleo barrier and estuary formation corresponding with brief episodes of rsl rise analyses of gpr facies and osl ages suggest annual clinoform deposition with geometries dictated by variations in enso these data demonstrate the utility of high resolution studies of coastal facies as useful proxy indicators for paleoclimate studies at subdecadal to millennial time scales

a concise compilation of petrologic information on possibly pristine nonmare moon rocks ansrn q cr to facilitate systematic study of the surviving compositionally pristine endogenously igneous rocks of the ancient lunar crust a compilation has been generated of all likely samples along with key information on the petrologic characteristics and chemistry of each sample the compilation includes 260 samples besides information related to the likelihood of each sample being truly pristine i e mainly its texture and siderophile element abundances information is compiled on mineral content listing major phases present as well as basic information on mineral compositions on size expressed as mass and on whether a reasonably comprehensive chemical analysis has been published the compilation also classifies the samples into seven categories of confidence in the pristine composition of the samples reflecting an estimation of the relative likelihood that each arguably pristine sample is in fact pristine for many purposes it is crucial to avoid inclusion of polymict rocks in a data base on petrologic diagrams such as a plot of average mg mg 100 x molar mg mg fe in a low ca mafic silicate vs average an content in plagioclase rocks in the top three categories of the confidence in pristine character appear distinctly bimodal in composition with roughly half belonging to a ferroan suite characterized by high an despite relatively low mg when samples of low to moderate pristine character are included the bimodality appears less distinct sample mass can also be important with a data base restricted to samples more massive than i g there is a clear distinction in feldspar content and bulk density between ferroan and nonferroan mgsuite rocks such that only the ferroan suite rocks are likely to have formed as flotation cumulates with a data base including smaller samples the same basic pattern is seen but only in a blurred form as the two rock types show considerable overlap in their modal feldspar contents

a three component model for the bulk composition of the moon abstract using detailed analyses of lunar pristine glasses as a basis delano 1986 we present a suite of models of lunar bulk composition which are based on the following assumptions i that the early moon differentiated into two primary reservoirs 1 an feo rich magma ocean and 2 an olivine rich residuum of fo90 and ii that this magma ocean then differentiated into an olivine dominated cumulate fo80 and a primitive liquid composition ppg thus in these models the bulk composition of the moon is given by a mixture of three components an early olivine residuum a later olivine orthopyroxene cumulate and ppg liquid with the constraint that the moon possess a ci chondritic mg al ratio our model lunar compositions are grossly similar to the lunar composition of ringwood et al 1987 and when projected from feo they appear very similar to the composition of the earth s upper mantle again when projected from feo our model magma ocean compositions are very similar to the bulk lunar composition derived by taylor 1982 remelting of cumulates from the magma ocean can produce the mare basalts and the pristine glasses remelting of the early residuum may be the source of the highly magnesian olivines found in the lunar highlands our ability to relate such diverse chemistries as the earth s mantle and taylor s moon is relatively model independent the model compositions discussed above are generated by assuming that the cumulate formed by equilibrium crystallization to better determine if there is a significant difference between the feo contents of the earth and the moon we have also calculated bulk lunar compositions whose cumulate component is formed by fractional crystallization a more realistic approximation we find that if the mg si ratios of the earth and moon are similar and if the early residue is dominated by olivine then the bulk silicate moon is 25 to 50 enriched in feo over the earth s upper mantle 10 to 13 wt feo for the moon as compared to 8 wt for the earth again the ultimate basis for this estimate of lunar feo is the set of lunar pristine glasses a characteristic of all our models is that refractory lithophile elements such as ca and al are calculated to be 2 to 3 times ci in the bulk silicate moon these abundances are largely determined by our requirement that the moon possess a chondritic mg al ratio to emphasize this point we discuss the implications of the choices of various mg al and mg si ratios in the calculation of bulk planetary compositions

comparison of logistic regression and neural network models in assessing geomorphic control on alluvial fan depositional processes calabria southern italy at the outlet of steep catchments depositional processes ranging from stream flow to debris flow usually lead to alluvial fan development apart from geological and tectonic factors controlling basin sediment availability several authors highlighted the control role of basin fan morphometry on fan sedimentary processes in this framework the paper was aimed to identify the feeder basin variables that can best differentiate fan processes in southern italy to evaluate the effect of the statistical method on variable selection we compared logistic regression lr and artificial neural network ann the latter not commonly used in fan studies alluvial fans were mapped at the mouth of steep v shaped valleys dissecting the tyrrhenian coast of northern calabria where crystalline metamorphic and subordinate carbonate rocks crop out fans were classified through field survey into two groups those with f1 and those without f0 any debris flow evidence morphometric variables were derived for each basin fan system percentage of lithological units cropping out in the catchments was also considered non parametric statistics revealed that f0 and f1 significantly differ in fan size area perimeter and length main channel slope lowermost valley width melton s number and geologic index the relationships between morphometric variables were stronger for f0 than f1 the lr and ann highlighted the primary control of basin lithology on fan dynamics followed by basin mean slope although ann outperformed lr in model calibration both the approaches correctly classified most of the validation samples 87 alluvial fans with unknown depositional process were classified as belonging to the same group

refining the eustatic sea level curve since the last glacial maximum using far and intermediate field sites the eustatic component of relative sea level change provides a measure of the amount of ice transferred between the continents and oceans during glacial cycles this has been quantified for the period since the last glacial maximum by correcting observed sea level change for the glacio hydro isostatic contributions using realistic ice distribution and earth models during the last glacial maximum lgm the eustatic sea level was 125 5 m lower than the present day equivalent to a land based ice volume of 4 6 4 9 107 km3 evidence for a non uniform rise in eustatic sea level from the lgm to the end of the deglaciation is examined the initial rate of rise from ca 21 to 17 ka was relatively slow with an average rate of ca 6 m ka 1 followed by an average rate of ca 10 m ka 1 for the next 10 ka significant departures from these average rates may have occurred at the time of the younger dryas and possibly also around 14 ka most of the decay of the large ice sheets was completed by 7 ka but 3 5 m of water has been added to the oceans since that time

enso related decadal scale climate variability from the indo pacific warm pool the el nino southern oscillation enso is a climatic phenomenon that affects socio economical welfare in vast areas in the world a continuous record of holocene enso related climate variability of the indo pacific warm pool ipwp is constructed on the basis of stable oxygen isotopes in shells of planktic foraminifera from a sediment core in the western pacific ocean at the centennial scale variations in the stable oxygen isotope signal delta o 18 are thought be a representation of enso variability although an imprint of local conditions cannot be entirely excluded the record for the early holocene 10 3 6 ka bp shows in comparison with the mid to late holocene small amplitude variations in the delta o 18 record of up to 0 3 parts per thousand indicating relatively stable and warm sea surface conditions the mid to late holocene 6 2 ka bp exemplified higher variability in delta o 18 and thus in oceanic ipwp conditions climatically we interpret this change 5 5 4 2 ka bp as a phenomenon induced by variability in frequency and or intensity changes of el nino in the period 4 2 2 ka bp we identified several periods centred on 1 9 2 1 2 7 3 3 3 7 and 4 2 ka bp with in general heavy 6180 values during these periods the ipwp was relocated to a more eastward position enhancing the susceptibility for el nino like conditions at the core site over the last 2000 yr precipitation increased in the area as a response to an increase in asian monsoon strength resulting in a freshening of the surface waters this study corroborates previous findings that the present day enso activity started around 5 5 ka bp c 2006 elsevier b v all rights reserved

petrogenesis of lunar troctolites models of petrogenesis for lunar troctolites are severely constrained by the high mg 88 values of the most primitive members of the mg rich suite melts derived by partial melting of olivine cumulates to the lunar magma ocean have high mg but are strongly undersaturated with respect to plagioclase assimilation of lunar crust cannot bring these melts to the plagioclase liquidus without unduly reducing the mg values of olivine partial melts derived by melting a iherzolite primitive interior have higher normative plagioclase contents but require sources with mg 90 more terrestrial like mg 88 values are permitted if rising thermal plumes are capable of entraining the most mg rich cumulates of the magma ocean the mg values of lunar troctolites may therefore reflect a hybrid source composed of primitive mantle and mg rich cumulates of the magma ocean higher mg values may also arise from the reduction of small amounts of feo to fe alternatively the parent magmas to lunar troctolites may be impact melts of the anorthositic crust and the mg rich dunite cumulates of the magma ocean the latter were brought to the upper mantle during the overturn of the unstable cumulate pile of the magma ocean

investigating the use of alluvial fan volume to represent fan size in morphometric studies studies of the morphometric properties of alluvial fans have predominantly used a two dimensional planimetric area to represent fan size even though fans are three dimensional sediment deposits but the validity of this substitution has been questioned volumes of fans in nonsubsiding settings were estimated with the objective of investigating the relationship between fan volume and fan area a simple geometric approach was developed so that volumes of noncoalescent fans could be estimated with measurements from topographic maps data were collected from two study areas with humid temperate climates the bow valley in alberta canada and the absaroka range in wyoming usa because these landscapes were glaciated the fans are of paraglacial origin and are not related to contemporaneous tectonic subsidence using functional relation analysis results indicate that the proportional power law relationship between fan volume and fan area is not significantly different from 1 1 in both study areas morphometric relationships between fans and drainage basins are also examined with fan volume and cumulative sediment yield employed as variables

the effect of surface texture on the determination of the surface hardness of rock using the schmidt hammer the schmidt hammer is employed by geomorphologists as a convenient field instrument for measuring the hardness of rock surfaces field trials indicate that the readings obtained are a function of not only the hardness of the surfaces but also their texture smooth planar surfaces give much higher readings than rough or irregular surfaces this makes interpretation of the results particularly difficult when the hammer is used to measure the hardness of natural rock surfaces that have been roughened by weathering

modelling alluvial fan morphology a mathematical model which estimates the scale independent sediment surface profile of alluvial fans has been developed this model utilizes a diffusive sediment transport model and an unsteady radial flow conservation relationship these equations are approximately solved assuming a quasi steady state closure with appropriate modelling assumptions for two end member fan types 1 fans where most of the fan surface is depositionally active denoted here as homogeneous and 2 fans characterized by channelling and sediment sorting processes the fundamental result for these two fan types is a dimensionless sediment profile relationship which approximates most fan surfaces the model suggests that the overall dimensionless morphology of alluvial fans is governed more by fundamental diffusion principles in sediment deposition than by individual environmental or basin characteristics additionally this work potentially can be extended to model temporal variation in fan development preliminary comparison with alluvial fan profiles is reasonable indicating that this model provides useful qualitative and quantitative information relating to alluvial fan process and morphology copyright 1999 john wiley sons ltd

climate and hydrographic variability in the indo pacific warm pool during the last millennium planktonic foraminiferal mg ca and delta o 18 derived sea surface temperature and salinity records from the makassar strait indonesia show a long term cooling and freshening trend as well as considerable centennial scale variability during the last millennium the warmest temperatures and highest salinities occurred during the medieval warm period mwp while the coolest temperatures and lowest salinities occurred during the little ice age lia these changes in the western pacific along with observations from other high resolution records indicate a regionally coherent southern displacement of the inter tropical convergence zone during the lia with more arid conditions in the northern tropics and wetter conditions in the southern tropics

beach ridges definitions and significance abstract beach ridges frequent components of quaternary coastal plains and other coastal landforms have been cited as indicators of the positions of ancient seashores and associated sea levels numerous authors utilized the term beach ridge for active and relict usually wave built supratidal and or intertidal forms wind built ridges have been only occasionally included in the definition the term was applied also to submerged landward shifting eventually stranded bars a consistent redefinition of the term is highly desirable beach ridges should include all relict strandplain ridges whether dominated by wave swash built or by eolian lithosomes all active ridge like shore features regardless of dimensions morphology and origin are excluded because of the resistance of coarse clastic ridges to wave and wind erosion swash built gravel or coarse shell storm ridges may build several meters above the level of high tide swash built high berms even on pure sandy beaches exceed the highest tides during episodes of wind induced record water levels frequently but not always burying underlying low relief berm ridges of berm lithosomes sequences of relatively steep multiple foredunes are commonly named beach ridge plains the narrow subparallel relict foredunes that form these strandplains presently are designated as eolian beach ridges beach ridges thus are defined as relict semiparallel multiple wave and wind built landforms that originated in the inter and supratidal zones until separated from the shoreline by progradation sandy pebbly or shell enriched backshore berm ridges behind an active foreshore should not be considered beach ridges strandplain progradation is either continuous or with the inclusion of subtidal cat s eye ponds discontinuous contrary to claims transgressive cheniers do not represent true cheniers alone within their overall progradational context cheniers a special category of beach ridges bracketed by subtidal intertidal mudflats may be transgressive or regressive in character landward driven transgressive ridges should be designated beach ridges only after they are stabilized on intertidal flats when recognizable between clearly identifiable intertidal and overlying eolian intervals the horizontal interface between these lithosomes in beach ridges may help the reconstruction of ancient tide lake levels diagnostic sedimentary textures structures and fossils however often may be unavailable in the deposits along with various types of elevated terraces composed of raised marine deposits and certain coastal landforms of erosional origin that occur worldwide beach ridges of clearly proven wave built origin may also serve as indicators of ancient higher than present sea levels

optical dating of dune sand for the study of sea level change a new widely applicable method to obtain well constrained relative sea level records presented here relies on optical dating of inorganic coastal landforms and sediments eighteen optical ages of basal dune sand from a barrier in massachusetts united states indicate that local relative sea level rose 8 m during the past 5 5 k y a sea level curve drawn from these optical ages shows good agreement with independent evidence from salt marsh peat sampled behind the barrier demonstrating the reliability of the method optical dating will be particularly useful in analyzing coastal records that contain too few organic indicators to allow high resolution 14 c based analyses

differential effects of base level tectonic setting and climatic change on quaternary alluvial fans in the northern great basin nevada usa

osl dating of late holocene coastal sediments and its implication for sea level eustacy in hainan island southern china abstract since the sea level rise is not geographically homogeneous but rather shows great regional differences optically simulated luminescence using quartz as a natural dosimeter has proved to be a powerful and reliable dating technique to determine depositional ages of young coastal sediments around the world the samples acquired from one beach ridge and two marine terraces in coastal hainan island southern china are detected osl dating for the investigation of sea level changes the results show 1 coastal sands in hainan island were well bleached before deposition and the quartz osl can date coastal sediments younger than 200 years which could be one of good indicators for paleo relative sea level highstand records 2 three coastal sediments with 4 m 3 7 m and 2 m higher than present sea level were deposited at 2 40 0 05 ka 2 92 0 17 ka and 4 26 0 10 ka respectively which indicate that the height of highstand relative sea level are higher than both mean global sea level eustacy and those records offshore southern china 3 comparisons with tropical cyclones observations around south china sea indicates that the late holocene coastal sediments of hainan island might have been reformed by tropical cyclones with a highstand sea level

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

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

copernicus crater central peak lunar mountain of unique composition olivine is identified as the major mafic mineral in a central peak of copernicus crater information on the mineral assemblages of such unsampled lunar surface material is provided by near infrared reflectance spectra 0 7 to 2 5 micrometers obtained with earth based telescopes the composition of the deep seated material comprising the copernicus central peak is unique among measured areas other lunar terra areas and the wall of copernicus exhibit spectral characteristics of mineral assemblages comparable to the feldspathic breccias returned by the apollo missions with low calcium orthopyroxene being the major mafic mineral

a topographic fingerprint to distinguish alluvial fan formative processes we demonstrate here a topographic fingerprint derived from a 1 m high resolution elevation model dem developed from airborne laser swath mapping alsm that distinguishes between formative processes from surface form in alluvial fans generated through relatively dry debris flows df and those surfaces formed primarily by fluvial sediment transport mf we selected alluvial fans with primarily holocene age surficial deposits along the eastern side of death valley california fans were initially classified in the field into df and mf types largely on the basis of sedimentological characteristics and surface morphometry trend surface analyses were performed on dems of the individual fans in order to remove the long wavelength trends both profile and planimetric from the residual data we found that high resolution surface data distinguishes process information in two ways 1 local relief increases as a function of length scale especially at length scales less than 40 60 m and 2 local relief is significantly higher for debris flow dominated fans than for fluvially dominated fans this fingerprint which is directly related to the dominant surface processes is unavailable from standard 30 m resolution data providing significant support for the acquisition of high quality high resolution data this fingerprint can be used to help calibrate numerical simulations of alluvial fan development and has the potential for similar applications to distinguish between processes of similar landforms on other planetary bodies within our solar system