geochemistry of laterites stability of al goethite al hematite and fe super 3 kaolinite in bauxites and ferricretes an approach to the mechanism of concretion formation

onset of aridity and dune building in central australia sedimentological and magnetostratigraphic evidence from lake amadeus abstract sediments from lake amadeus a groundwater discharge playa in central australia comprise a surface playa sequence the winmatti beds varying between 0 6 and 3 m in thickness overlying a long sequence of fairly uniform fluvial lacustrine clays the uluru clay the latter extends down to at least 15 m the maximum depth cored during this study and possibly down to 65 m below the present playa surface in the cores studied the brunhes matuyama boundary 0 73 ma was identifiable in all the upper sediments typically at a depth of between 1 and 2 m but below this there are two plausible chronological interpretations of the palaeomagnetic data deposition rates are very low typically no more than 1 5 cm ka in the uluru clay beds and down to 0 2 cm ka in the winmatti beds these rates suggest that the fluvial lacustrine phase lasted for at least 5 ma the boundary between the uluru clay and the winmatti beds bears a close correspondence to the boundary between the blanchetown clay a lacustrine sequence and the tyrrell beds a playa sequence in palaeo lake bungunnia in what is now the murray basin in southeastern australia however the transition occurs at about 0 9 ma or possibly 1 6 ma at lake amadeus whereas it has been dated palaeomagnetically at less than 0 73 ma probably 0 5 ma in lake bungunnia records from other locations in southeastern australia likewise support a major change from wetter to drier conditions at or shortly after the matuyama brunhes polarity transition thus the current evidence from lake amadeus indicates that in central australia the onset of aeolian and saline gypseous deposits characteristic of arid zone facies may have pre dated the corresponding change in the southeastern part of the continent by about 0 4 ma or possibly by about 1 1 ma in common with most playas in central australia lake amadeus is surrounded by a ring of gypseous dunes derived from material deflated from the surface of the playa magnetostratigraphic evidence from auger island in the middle of lake amadeus suggests that the oldest gypseous dune formation on the island must have pre dated the start of the jaramillo subchron at 0 98 ma or possibly the start of the brunhes epoch 0 73 ma thus making these the oldest dated dunes in australia the age of the auger island dunes is probably characteristic of other gypseous dunes around the margins of playas in central australia

palaeoenvironmental change recorded in the palaeodunefields of the western murray basin south australia new data from single grain osl dating this study is concerned with the reconstruction of the palaeoenvironmental history of southeastern australia for the last 300 ka by establishing a luminescence chronology of dune sand deposition in the western murray basin south australia in the study area vast fields of palaeodunes stabilised by vegetation provide evidence of past environmental change in total 98 samples were collected from dune sand layers at 13 different dune sections the time of their deposition was determined using optically stimulated luminescence dating of single quartz grains accounting for the impact of post depositional mixing by the use of a finite mixture model the oldest depositional phase demonstrates that dune sand layers of great antiquity are preserved in the western murray basin ranging up to at least 380 ka phases of substantial dune sand deposition were identified for the periods 18 38 ka and 63 72 ka older depositional phases also exist but are poorly resolved due to relatively large errors of the luminescence ages aeolian deposition during the last termination and the holocene is relatively limited with a slight clustering of ages at the time of the antarctic cold reversal and from 5 8 ka two modern ages give evidence of very recent dune sand deposition comparison with other palaeoclimate records from the region suggests that phases with high aeolian sedimentation coincide with more arid conditions and breaks in the dune record with more humid phases thus although dune records are often discontinuous and their interpretation in palaeoclimatic terms is not always straightforward the palaeodunes of the western murray basin show a good preservation of phases of aeolian activity and provide useful information for palaeoenvironmental reconstruction

palaeogeographic climatic and tectonic change in southeastern australia the late neogene evolution of the murray basin the murray basin is a low lying but extensive intracratonic depocentre in southeastern australia preserving an extraordinary record of late neogene sedimentation new stratigraphic and sedimento logic data allow the long term evolution of the basin to be re evaluated and suggest a significant role for 1 tectonism in controlling basin evolution and 2 progressive and step wise climatic change beginning in the early pleistocene tectonic change is associated with regional uplift occurring at approximately the same rate from the early pliocene until the present day and possibly associated with changing mantle circulation patterns or plate boundary processes this uplift led to the defeat and re routing of the murray river australia s major continental drainage system key to our interpretation is recognition of timing relationships between four prominent palaeogeographic features the loxton parilla sands strandplain the gambier coastal plain palaeo megalake bungunnia and the kanawinka escarpment geomorphic and stratigraphic evidence suggest that during the early pliocene the ancestral murray river was located in western victoria flowing south along the douglas depression relatively small amounts of regional uplift 200 m defeated this drainage system dramatically changing the palaeogeography of southeastern australia and forming plio pleistocene megalake bungunnia at its maximum extent lake bungunnia covered more than 50 000 km 2 making it one of the largest known palaeo or modern lakes in an intracontinental setting magnetostratigraphic constraints suggest lake formation c 2 4 ma the formation of lake bungunnia influenced the pliocene coastal dynamics depriving the coastline of a sediment source and changing the coastal system from a prograding strandline system to an erosional one erosion during this period formed the kanawinka escarpment a palaeo sea cliff and one of the most prominent and laterally extensive geomorphic features in southeastern australia marine sediments c 800 ka to c 1 16 ma represent the time of re establishment of depositional coastal dynamics and of a permanent outlet for the murray river this age range is consistent with our best estimate of the age of the youngest lake bungunnia sediments and points towards an early pleistocene age for the demise of the lake system the youngest lake bungunnia sediment present on a number of distinct terraces suggests that progressive step wise climatic change played a role in the demise of the lake however in order for the ancestral murray river system to have been able to breach the pre existing tectonic dam it is likely that tectonic change and or temporarily enhanced discharge was also significant this scenario indicates that the modern murray river has only been in existence for at most 700 ka c 2010 elsevier ltd all rights reserved less

the occurrence and significance of biogenic opal in the regolith abstract biogenic opal produced by vascular plants diatoms and siliceous sponges have been found in soils and terrestrial sediments of all continents except antarctica since the middle of the 19th century the opal particles range in size from fine silt to fine sand almost all soils contain detectable opal up to levels of 2 3 and a significant number contain values in excess of 5 even higher values have been found from soils and sediments of all continents in a wide range of soil types the most important factor is poor soil drainage and seasonal to permanent water logging this encourages the proliferation of silica producing organisms such conditions have been found in the soils and aquatic sediments of the monsoonal tropics tropical rain forests temperate forests tropical savanna tropical islands semi arid grasslands and savanna and temperate woodland and grassland the presence of a volcanic substrate also appears favourable in some cases but is not necessary biogenic opal preferentially collects in the a horizon of soils and to a lesser extent in the b horizon this preferential distribution facilitates identification of palaeosols in stacked soil sequences biogenic opal is also a component of windblown dust even in arid environments biogenic opal is significant to regolith processes in a number of ways firstly as in the case in marine environments it is likely to be important in silica cycling and storage because of its greater lability compared to quartz secondly dissolution and reprecipitation of opal a as opal ct or micro quartz may play a role in cementation and silicification of regolith to form silica hardpans and silcrete thirdly the organisms that form biogenic opal can have considerable palaeoenvironmental significance and be valuable in reconstructing regolith evolution finally some forms of biogenic silica in particular sponge spicules can present a health hazard their high abundance in some soils and sediments needs to be considered when assessing the health implications of airborne dust

australian desert dune fields initiated with pliocene pleistocene global climatic shift development of continental aridity has been linked to late cenozoic global cooling but the evidence is indirect based on terrestrial loess deposits and eolian silt in marine sediments whereas direct dating of the inception of arid landforms has been frustrated by a lack of suitable methods here we report the first age determination of a major arid zone dune field based on cosmogenic 10 be and 26 al measurements of drill cores from dunes in the simpson desert central australia results show that the dune field began to form ca 1 ma whereas dating using quartz optically stimulated luminescence indicates episodic dune building during late quaternary ice ages less intense desertification began earlier the previous cosmogenic exposure dating showed that neighboring stony deserts began to form at the onset of quaternary ice ages 2 4 ma aridity deepened and the dune field formed when ice age cycles increased their amplitude and switched their periods from 40 k y to 100 k y ca 1 ma

numerical modelling of tsunami propagation with implications for sedimentation in ancient epicontinental seas the lower jurassic laurasian seaway abstract tsunamis are frequent events in modern marine environments but evidence of their passing in subtidal ancient epicontinental sea deposits is elusive it has been suggested that this is due to mis identification or poor preservation potential herein a numerical modelling approach is used to show that tsunami propagation in one large ancient epicontinental sea was hindered by the damping effect of shallow bathymetries and reflection refraction and diffraction from emergent landmasses the imperial college ocean model icom is used for this study and is first validated against data from the sumatra andaman tsunami of december 2004 a palaeobathymetric dataset is then presented for the hettangian lower jurassic laurasian seaway with idealised tsunami sources situated on the continental shelf and within the adjacent oceanic basin results show that tsunamis forced from within ocean basins adjacent to the epicontinental sea are rapidly attenuated over the continental slope and fail to propagate great distances onto the shelf similarly the sedimentological effect of tsunamis forced from within the epicontinental sea is also restricted it is concluded that tsunami deposits in ancient epicontinental seas are most likely to occur in relative proximity to the source region and this must contribute to their scarcity in the geological record

comments to dawson a g and stewart i 2007 tsunami deposits in the geological record sedimentary geology 200 166 183

numerical models of tsunami sediment transport current understanding and future directions abstract researchers who study tsunami deposits share common ultimate goals of their work which are to better assess the magnitude information of paleotsunamis and to contribute to the assessment of future tsunami risks numerical modeling of tsunami sediment transport is an important piece of interdisciplinary research that fills the gap between geological studies and practical utilization of tsunami deposits forward and inverse numerical models that address tsunami transport of sand and boulders have been developed over the last two decades forward models are capable of delineating the time evolution of tsunami hydrodynamics sediment transport and the resulting morphological changes associated with erosion and deposition inverse models estimate tsunami characteristics such as flow speed and depth from deposits numerical modeling can be used not only to quantify paleotsunamis but also to enhance our understanding of tsunami sedimentology and hydrodynamics to make progress towards the ultimate goal of improved tsunami risk assessment development of an in depth mutual understanding between modelers and geologists of the advantages limitations and uncertainties in both numerical modeling and geological records is an important challenge

two stage mid brunhes climate transition and mid pleistocene human diversification abstract global climate shifted to markedly warmer interglacial conditions across the mid brunhes transition mbt 400 ka however a global mbt synthesis that spans marine and terrestrial evidence remains elusive which limits our understanding of the role of the mbt in mid pleistocene human evolution we synthesize asian precipitation reconstructions within a context of global palaeoclimatic records and find that the mbt occurred in two stages first stronger warming of northern hemisphere continents weaker southern hemisphere warming and related more extensive northward displacement of the intertropical convergence zone itcz during interglacial marine isotope stage mis 13 intensified and expanded precipitation in asian monsoon regions and in other widespread northern hemisphere regions with accompanying carbon reservoir changes featuring globally high marine benthic 13c values because of vegetation expansion at 500 ka subdued southern hemisphere warming and northward itcz displacement decreased southern hemisphere precipitation simultaneously during mis 13 second a shift to globally warmer interglacials at 400 ka with elevated atmospheric co2 concentrations smaller ice volume and higher sea level resulted in sustained high interglacial precipitation in east asia from mis 11 onward and sustained high marine benthic 13c values during mis 11 we also synthesize palaeoanthropological data and find that the climate and ecosystem changes across the mbt coincided with the timing of human lineage diversification including the emergence of neanderthals and denisovans in eurasia and homo sapiens in africa and their potential coexistence with h heidelbergensis h erectus h floresiensis h naledi and other homo archaics the timing of the mbt also coincided with novel hominin behavioural developments including fire control and the transition from handaxe industries to more versatile levallois techniques combined with environmental theories of human evolution this chronological coincidence suggests a potential link between mid pleistocene environmental changes and human evolution

mineral magnetic tracing of aeolian dust in southwest pacific sediments abstract reliable magnetic signatures were sought to trace aeolian dust in tasman sea sediments where the aeolian fraction had also been chemically isolated modern dust samples from eastern australia were found to have a strong ferrimagnetic signal and a weaker antiferromagnetic afm background the ferrimagnetic component could not be detected in the deep sea sediments where a finer biogenic magnetite component prevails over a background afm and two other authigenic components the modern dust is thought to be unrepresentative of prehistoric dust probably as the result of contamination from local agricultural soils the afm component in the sediments however was found to be highly correlated with the independently determined aeolian concentration except in intervals with a high magnetic susceptibility high fd signal possibly from an authigenic component because of the non aeolian contribution to magnetic hardness sirm irm 300 and different relationships observed in different cores the magnetic tracing of aeolian dust is currently only valid as a measure of relative changes in concentration in sediments with similar chemistry and low frequency dependence of susceptibility

application of in situ produced cosmogenic 10be and 26al to the study of lateritic soil development in tropical forest theory and examples from cameroon and gabon abstract depth profiles of in situ produced cosmogenic nuclides including 10 be t 1 2 1 5 10 6 years and 26 al t 1 2 0 73 10 6 years in the upper few meters of the earth s crust may be used to study surficial processes quantifying denudation and burial rates and elucidating mechanisms involved in landform evolution and soil formations in this paper we discuss the fundamentals of the method and apply it to two lateritic sequences located in african tropical forests

sedimentological and geochemical interpretation of a transgressive sequence the late cretaceous qahlah formation in the western oman mountains united arab emirates abstract the stratigraphic and palaeogeomorphologic conditions of the qahlah formation deposition in the united arab emirates are related to the geotectonic evolution of the western oman mountains during the late cretaceous the qahlah formation ranges from a few metres to more than 70 m in thickness it is the first sedimentary deposit to onlap the obducted semail ophiolite which was subjected to extensive weathering in a tropical environment during the maastrichtian erosion accompanied the transgression of the maastrichtian sea across the region the sedimentary sequence can be divided into four facies ophiolitic breccia ophiolitic conglomerate lateritic ferruginous silstone and lithic sandstone these sediments were probably formed in a shallow marine to beach setting adjacent to a retreating cliff line of the ophiolite a comparative analysis of the principal chemical and mineralogical components of the different facies indicates a genetic relationship between them the nickel content 0 85 1 1 16 wt in the laterite facies is of economic interest as a low grade ore provided that larger reserves can be identified

comparison of deeply buried paleoregolith profiles norwegian north sea with outcrops from southern sweden and georgia usa implications for petroleum exploration abstract for the first time on the norwegian continental shelf deeply buried paleoregolith profiles have been identified as part of the petroleum reservoirs in recently discovered oil fields on the utsira high norwegian north sea reservoir properties porosity and permeability in the granitic basement on the utsira high are mainly the result of physical and chemical alteration of the rock occurring in the near surface environment during sub aerial exposure of the high in the mesozoic evaluating the reservoir potential of altered basement rocks requires a different approach than in conventional petroleum exploration in this paper macroscopic mineralogical and micromorphological alteration features observed in two deeply buried paleoregolith profiles are compared with surface paleoregoliths from ivo klack sweden and georgia usa the paleoregolith profiles are subdivided into specific weathering facies altered coherent rock facies saprock facies and saprolite facies based on the rock fabric and mechanical strength the reservoir potential of each weathering facies is controlled by the type and degree of alteration in the altered coherent rock facies porosity and permeability is mainly controlled by joints and microfractures that developed prior to subaerial exposure of the granitic pluton in the saprock facies intensified chemical dissolution of plagioclase enhanced porosity and the development of mesofractures improved the connectivity between pores in the saprolite facies progressive dissolution of plagioclase creates porosity but the precipitation of clays within voids and mesofractures has a destructive effect on the overall reservoir properties the deeply buried paleoregolith profiles from the utsira high display comparable macroscopic mineralogical and micromorphological alteration features to what was observed in surface paleoregoliths from ivo klack and georgia outcrop studies may therefore be an important tool when evaluating the reservoir potential in subsurface paleoregoliths

chronology of murrumbidgee river palaeochannels on the riverine plain southeastern australia four major periods of palaeochannel activity have been identified on the murrumbidgee sector of the riverine plain of southeastern australia on the basis of stratigraphic information the channels reveal a picture of changing flow conditions during the last full glacial cycle the ages of the periods were determined from nearly 40 thermoluminescence dates on surficial fluvial and aeolian sediments these are named the coleambally phase which occurred from 105 to 80 ka the mid to latter part of oxygen isotope stage 5 the kerarbury phase from 55 to 35 ka stage 3 the gum creek phase from 35 to 25 ka late stage 3 to early stage 2 and the yanco phase from 20 to 13 ka late stage 2 the present flow regime was established by about 12 ka stage 1 the first two phases correlate with episodes of enhanced fluvial activity in northern and central australia and with reduced dust activity globally the phases in stage 2 appear to be associated with seasonal snow melt and increased peak flows in periods flanking the last glacial maximum source bordering aeolian dunes associated with the coleambally kerarbury and yanco phases were found however the tl dates show that some have undergone aeolian reworking thermoluminescence dating and fluvial stratigraphy have revealed a detailed picture of late quaternary climate and flow regime changes that has the potential to extend to identified deposits stratigraphically older than those described here

benchmarks and sediment source s of the 1755 lisbon tsunami deposit at boca do rio estuary article standardizing the signature of tsunami deposits has been identified as a major limitation for the identifica tion of paleo tsunami deposits this limitation mostly arises from the strongly source dependent nature of these deposits which in turn determines their composition and depositional architecture and from the effect of the local morphology of the corresponding depositional environment here we provide new high resolution mineralogical geochemical and micro macrofauna data of the 1755 tsunami layer of boca do rio estuary algarve portugal with the aim of unraveling the signatures of estuarine tsunami deposits and linking them to possible sediment sources we also apply for the first time diffuse reflectance spectropho tometry drs analysis our results show that the 1755 tsunami deposit of the boca do rio estuary is featured by an enhancement in sr and ca which are linked to the input of biogenic and detrital carbonates shell frag ments and limestone clasts from the beach foreshore and a strong depletion in most terrestrial and marine sensitive indicators the latter is interpreted as resulting from the reworking of the estuarine clays and subsequent dilution within a huge volume of sand eroded from the coastal barrier it confirms that in the case of the boca do rio estuary the sediment source is essentially proximal and coastal textural and min eralogical features between the base and the top of the tsunami layer suggest the imprint of run up and back wash currents derived from a unique wave micro and macrofauna analysis and drs data of the siliciclastic fraction show slight but significant environmental changes occurring just after the tsunami which could be provoked by an eventual closure of the estuary mouth

magnetic polarity stratigraphy of the fisherman s cliff and bone gulch vertebrate fossil faunas from the murray basin new south wales australia abstract the fisherman s cliff and bone gulch local faunas are the second and third oldest mammalian fossil assemblages known in the murray basin of southeastern australia the determination of well constrained ages for these two faunas has been plagued by a lack of diagnostic microfossils or material suitable for isotopic age determinations based on previous paleomagnetic data 1 2 the ages of the fisherman s cliff and bone gulch local faunas were assigned to the gauss and lower matuyama chrons respectively however these dates were not tested by direct magnetostratigraphic studies at either locality in order to make direct correlations 22 paleomagnetic and five paleomagnetic sites respectively were collected from fisherman s cliff and bone gulch results indicate that the fisherman s cliff local fauna occurs within a zone of normal magnetic polarity whilst the bone gulch local fauna occurs within a zone of reversed polarity by correlation to the chowilla section these zones are interpreted to represent the gauss and lower matuyama chrons and ages of 2 47 2 92 and 1 88 2 47 myr are indicated for the fisherman s cliff and bone gulch local faunas respectively

quaternary stratigraphy geochronology and evolution of the magela creek catchment in the monsoon tropics of northern australia abstract magela creek a major tributary of the east alligator river in northern australia has left a detailed sedimentary record of a fluvial landscape dominated by climatic and eustatic changes associated with quaternary glacial interglacial cycles uranium series dates from young pisoliths in floodplain deposits indicate that ferruginisation is probably ongoing under present conditions while ferricretes in degraded terraces that flank the lower valley reveal a fluvial history extending back to early pleistocene or tertiary time inset within this older alluvium is a valley fill which from thermoluminescence dates was initiated about 300 kyr ago with each glacial climate change and associated fall in sea level distinct palaeochannels have been eroded into these floodplains infilling later with alluvium when climate and base level conditions were conducive to fluvial deposition radiocarbon dates show that the most recent palaeochannel beneath the modern magela creek last started to fill by downstream progradation and vertical accretion of bedload sand about 8 kyr the palaeochannel filled at an accelerating rate probably as a result of declining stream competence associated with drier conditions in the late holocene augmented by the backwater effects of sea level rise continued aggradation blocked the mouths of tributary valleys along magela creek forming alluvial dammed tributary lakes and deferred junction tributary streams from about 300 kyr cyclic episodes of channel incision and sediment evacuation in this tropical monsoon river valley have become less effective possibly because increasing aridity in the late quaternary has reduced the erosional effectiveness of australia s northern rivers reduced flow regime and rising sea level in the late holocene has resulted in the latest phase of alluvial accretion

paleosurfaces from northeastern amazonia as a key for reconstructing paleolandscapes and understanding weathering products the characterization and mapping of paleoweathering surfaces as well as their associated deposits throughout the northeastern amazonia can be a useful tool for inter basin stratigraphic correlations and for establishing the evolution of landscapes and climates through time this type of investigation has led to the recognition of five weathering surfaces developed from the upper cretaceous through the quaternary designated here as s1 to s5 surface s1 occurs at the top of late cretaceous deposits represented by the ipixuna cujupe succession as well as on older precambrian and paleozoic rocks surface s2 marks the top of an indurated massive semi flint1 unit for cases in which surfaces s1 and s2 are amalgamated a thick lateritic paleosol displaying hexagonal branched concretions is present surface s3 occurs at the top of the pirabas and lower portion of the barreiras formations of late oligocene early miocene age and it is also associated with paleosol but has no lateritization when surface s3 is amalgamated with surfaces s1 and s2 bauxite is present in association with the underlying laterites surface s4 bounds the top of the middle to upper barreiras formation of middle miocene age as well as correlatable deposits known as the belterra clay this surface is marked by a lateritic paleosol having columnar concretions surface s5 occurs between a lower unit consisting of massive light red sands of the plio pleistocene post barreiras 1 sediments and an upper unit of yellow eolian sands of the holocene post barreiras 2 sediments the paleoweathering surfaces present in the northeastern amazonia enable the reconstruction of several depositional episodes represented by thin only few meters thick sedimentary units from the late cretaceous to the quaternary the creation of new accommodation space on subsiding areas gave rise to sediment accumulation during transgressions intervening weathering surfaces formed during significant falls in relative sea level associated with tectonically stable episodes the overprinting of weathering surfaces formed during different times and thus under different climatic conditions seems to have been crucial for the development of the various weathering products observed throughout the region which include economically important laterites bauxites semi flint beds and kaolin deposits this paper shows that the genesis of these deposits was controlled by the complex interplay of tectonics climate sediment deposition and erosion resulting in a complex evolution of paleolandscapes

the paroo station mine supergene lead deposits western australia geological and geochemical constraints abstract the paroo station mine lead project is situated near wiluna in the central part of western australia it is located in an outlier of the paleoproterozoic earaheedy group overlying the southeast yerrida basin the total measured and indicated mineral resource is currently as at 31st of december 2014 estimated at 31 8 mt of ore at 4 4 pb the deposits are hosted by deeply weathered carbonate and clastic sediments of the paleoproterozoic yelma formation the lead only mineralisation contains only traces of sulfides and is composed of few supergene minerals predominantly cerussite and anglesite with minor pyromorphite and plumbogummite the paroo station mine demonstrates a high degree of supergene pb mobility which has resulted in almost complete destruction of primary pb distribution pattern and development of characteristic for the oxidation zones coupled depletion zone and subhorizontal enrichment blankets below the deposits are interpreted to have formed from mississippi valley type mvt stratabound relatively low grade sulfide pb zn mineralisation located within dolomites of the sweetwaters well member of the yelma formation the primary mineralisation based on modelling the pb distribution was controlled by a network of northeast northwest and meridional oriented fractures and small faults lead isotope study yielded from 1 80 to1 88 ga ages of the mineralisation based on the stacey and kramers 1975 two stage model the mineralising event is related to the capricorn orogeny this data is well in line with previous u pb dating of monazites interpreted to be related to the mineralisation 1 82 ga muhling et al 2012 high 238u 204pb values 10 26 10 58 are indicative of the archean basement contribution and or more likely with sediments originally derived from that basement the paroo station mine mineralisation is thought to be similar in style and formed synchronously with the mvt prospects in the teague area in the earaheedy basin approximately 120 km to the northeast the mineralisation at the paroo station mine was significantly upgraded through a multi stage supergene remobilisation and reprecipitation of lead in the course of long weathering history of the region lead was almost completely depleted from the upper zone and accumulated below as subhorizontal enrichment blankets at three levels from top to bottom 1 the base of the collapse quartz clay breccia unit marking the dolomite weathering front 2 the contact of siltstone and sandstone packages coincident with the feldspar kaolinite weathering front and 3 the mid to lower parts of the sandstone unit close to the base of weathering the lowest enrichment zone extends as a continuous blanket at a significant up to 500 m distance at a 1 pb cut off beyond the upper mineralisation projection this enrichment is interpreted to be formed by lateral pb transport in waters close to the groundwater table through the most permeable layers of weathered sandstones this active lateral lead dispersion is of high exploration significance for the region providing a much larger exploration target and vector to the primary mineralisation

field observations of sediment transport across the rocky coast of east taiwan impacts of extreme waves on the coastal morphology by typhoon soudelor abstract after the 2015 typhoon soudelor large boulders and mixed sediments deposited extensively across the beach along the east coast of taiwan field measurements of these storm related sediments provide the first hand evidence to document the impacts of extreme waves induced by typhoon soudelor although the maximum inundation distance is only 170 m due to the lack of beach buffer zone the weight of the largest boulder was estimated over 1 t and the maximum run up was estimated up to 11 9 m the clast distribution of the washover and the beach face sediments exhibited reverse directions of coarsening reflecting different stages of wave propagation our field records show that a super typhoon like soudelor can potentially leave footprints of extreme values in the geologic records therefore a comprehensive understanding on the occurrence of the sediments and the depositional environment should be carefully considered to pin down the origin of the archived extreme events in addition the formation of the higher extreme wave berm and the destruction of the lower swell berm at the yen liao beach displayed the power of the storm surges suggesting the important role of the run up on the evolution of the berm

migration of radionuclides from a granite repository migration of radionuclides in the fracture of a host rock matrix surrounding a high level waste repository is discussed in terms of two coupled one dimensional equations one for the fracture and the other for the porous rock matrix the processes considered are advection dispersion radioactive decay and adsorption on the surface of the fracture and diffusion radioactive decay and adsorption in the microfissures of the host rock the temporal and spatial distribution of concentration and flux at the outlet of the fracture for some typical radionuclides encountered in high level radioactive waste has been computed using two component leaching from the waste matrix and budgeting the total inventory it is observed that the concentration of 90sr and 239pu markedly decreases with distance along the fracture due to sorption and decay however either travel time or sorption do not present enough delay for significant decay of 129i in fracture water while the peak flux of 129i shows insignificant variation at different fracture lengths for varied fracture apertures that of 239pu has functional dependence on both parameters

the effect of organic matter on chemical weathering study of a small tropical watershed nsimi zoetele site cameroon abstract the effect of organic matter during soil water interaction is still a debated issue on the controls of chemical weathering in a tropical environment in order to study this effect in detail we focused on the weathering processes occurring in a small tropical watershed nsimi zoetele south cameroon this site offers an unique opportunity to study weathering mechanisms in a lateritic system within a small basin by coupling soil and water chemistry the lateritic cover in this site can reach up to 40 m in depth and show two pedological distinct zones unsaturated slope soils on the hills and or elevated areas and water saturated soils in the swamp zone which represent 20 of the basin surface the study present chemical analysis performed on water samples collected monthly from different localities between 1994 1997 and on soil samples taken during a well drilling in december 1997 the results suggest the existence of chemical and spatial heterogeneities of waters in the basin colored waters flooding the swamp zone have much higher concentrations of both organic matter i e doc and inorganic ions e g ca mg al fe th zr than those from springs and groundwater from the hills nevertheless these organic rich waters present cation concentrations na ca mg k which are among the lowest compared to that of most world rivers the main minerals in the soils are secondary kaolinite iron oxi hydroxides quartz and accessory minerals e g zircon rutile we mainly focused on the mineralogical and geochemical study of the swamp zone soils and showed through sem observations the textural characterization of weathered minerals such as kaolinite zircon rutile and the secondary recrystallization of kaolinite microcrystals within the soil profile water chemistry and mineralogical observations suggest that hydromorphic soils of the swamp zone are responsible for almost all chemical weathering in the basin thus in order to explain the increase of element concentration in the organic rich waters we suggest that organic acids enhance dissolution of minerals such as kaolinite goethite and zircon and also favors the transport of insoluble elements such as al fe ti zr and ree by chemical complexation sio2 aq concentrations in these waters are above saturation with respect to quartz dissolution of phytholithes amorphous silica may be responsible for this relatively high sio2 aq concentration al mg ratios obtained for the soil and the mengong river waters show that a significant amount of al does not leave the system due to kaolinite recrystallisation in the swamp zone soils geochemical data obtained for this watershed show the important contribution of vegetation and organic matter on chemical weathering in the swamp zone quantitatively we propose that the increasing amount in total dissolved solid tds due to organic matter and vegetation effect is about 35 in summary this interaction between soils and waters occurs mostly in soils that are very depleted in soluble elements thus the low concentration of major elements in these water is a direct consequence of the depleted nature of the soils

the late pleistocene evolution of palaeo megalake bungunnia southeastern australia a sedimentary record of fluctuating lake dynamics climate change and the formation of the modern murray river abstract the ephemeral lacustrine carbonates of the bungunnia limestone deposited in palaeo megalake bungunnia preserve a detailed record of pleistocene palaeoenvironmental and palaeoclimatic change in southeastern australia five distinct lake shorelines lake levels 0 4 are visible on digital elevation models ranging in elevation from around 70 m to 30 m above sea level the bungunnia limestone is preserved on the three lowest terraces ranging over 20 m in elevation lake levels 2 4 on the two higher of these terraces bungunnia limestone contains ooids and stromatolites and is calcite and aragonite dominated whereas on the lower terrace level bungunnia limestone is dolomite gypsum and magnesite dominated and preserves tepee structures and mud cracks thus lacustrine conditions are interpreted to have become increasingly saline and evaporitic over time reflecting an overall trend to more arid climatic regimes the highest lake level level 0 at around 70 m above sea level appears to relate to a period of significantly increased rainfall that allowed the lake to overflow for the first time marking the initiation of the modern murray river subsequently the lake fluctuated between 1 a steady state open lake system where water was overflowing across the padthaway high spillpoint and active gorge cutting was proceeding and 2 a closed lake system with no overflow that resulted in carbonate precipitating conditions during 1 shoreline erosion was occurring within the basin providing the terraces on which the bungunnia limestone carbonates were deposited during 2 in this 1 is likely to correspond with significantly wetter late pleistocene interglacial and 2 with arid glacial conditions the formation of the modern murray river and the demise of palaeo megalake bungunnia were therefore consequences of a combination of gorge cutting and increasing aridity resulting from interglacial glacial climate oscillation superimposed on significant overall climatic change

the record of continental dust from australia in tasman sea sediments abstract the flux of aeolian dust from australia to sediments of the tasman sea has increased during glacial stages of the last four glacial cycles low fluxes of dust from australia before 350 ka were followed by an increase in stage 10 and high fluxes in peak glacial periods thereafter the initiation of higher dust fluxes in stage 10 is consisten with previous estimates of the age of onset of aridity in the source area dust flux to the tasman sea is thought to record the intensity of deflation from the source area in interior southeastern australia which was marked by arid conditions and possibly greater windiness during the last glacial a transect of five cores from the central tasman sea revealed consistently low dust fluxes north of 33 s increasing southward to approximately 40 s glacial to interglacial movement of the northern boundary of the dust plume governed by the position of the subtropical ridge was less than 6 latitude probably closer to 3 350 km the position of the dust plume determined in this study and its response to climate change are significantly different from a previous reconstruction based on the measurement of quartz content of the non biogenic sediment fraction

analysis of environmental controls on tsunami deposit texture abstract tsunamis transport large amounts of sediment and can leave recognisable signatures in the landscape the form and composition of onshore tsunami deposits are a function of wave dynamics sediment availability and characteristics of the local environment the latter of which also partially controls preservation of the deposit this research reviews these relationships in a global context and assesses the connection between tsunami deposit particle size and four controlling parameters climate temperature and rainfall density of tsunami sediments degree of coastal protection and distance between tsunami source and sediment deposition an international dataset of tsunami deposit locations and texture was compiled from published literature and existing databases values for environmental variables were calculated for each location from global datasets of temperature rainfall coastline shape and tsunami source locations spearman s rank order correlation principal component analysis pca and hierarchical cluster analysis ca were used to analyse relationships between these variables pca results show an inverse relationship between particle size and sediment density climate variables and distance from source ca results support this suggesting a cluster structure controlled primarily by particle size and secondly by climate and sediment density these relationships can be explained by the influence of the environment on antecedent morphology and the composition of sediments available for tsunami transport

spatial variability and hydrologic evolution of australian lake basins analogue for pleistocene hydrologic change and evaporite formation abstract processes evident in basins across hydrologic gradients from humid to arid regions today provide analogues for systems that may have operated in some individual basins during periods of past hydrologic change thus lakes in humid regions today with low salinity sedimentary facies and with morphology controlled largely by wave action may closely resemble past lacustral pluvial phases experienced in zones which today are relatively arid and saline conversely playas controlled today by groundwater and in some cases subject to defletion may resemble those arid and dune building stages experienced by basins in sub humid regions today as they underwent glacial age desiccation in any such sequence of spatial or temporal gradients from humid to more arid conditions the frequency of basin filling and drying modulates the rate of evaporitive loss of interstitial waters from the exposed basin surface this in turn controls the salinity evolution of the interstitial and local groundwaters the notion of closed systems for terminal lakes while satisfactory for analysis of surface water budgets is quite inapplicable to the evolution of brines where surfacewater groundwater exchange during the high salinity drying stages becomes a controlling factor affecting all salt budgets in these systems evaporites may only be preserved when the sub surface waters have evolved to salinites near saturation for the salts concerned if sub surface waters are frequently diluted by surfacewater groundwater exchange evaporites will not be preserved in the record even though the surface system appears hydrologically closed the process of interstitial water evolution which controls efflorescence deflation and salt weathering exerts a dominating influence on basin geomorphic expression as well as on hydrochemical fractionation

erratum to identification of tsunami induced deposits using numerical modeling and rock magnetism techniques a study case of the 1755 lisbon tsunami in algarve portugal physics of the earth and planetary interiors volume 182 issues 3 4 pages 187 198 october 2010 abstract storm and tsunami deposits are generated by similar depositional mechanisms making their discrimination hard to establish using classic sedimentologic methods here we propose an original approach to identify tsunami induced deposits by combining numerical simulation and rock magnetism to test our method we investigate the tsunami deposit of the boca do rio estuary generated by the 1755 earthquake in lisbon which is well described in the literature we first test the 1755 tsunami scenario using a numerical inundation model to provide physical parameters for the tsunami wave then we use concentration ms sirm and grain size arm arm b1 2 arm sirm sensitive magnetic proxies coupled with sem microscopy to unravel the magnetic mineralogy of the tsunami induced deposit and its associated depositional mechanisms in order to study the connection between the tsunami deposit and the different sedimentologic units present in the estuary magnetic data were processed by multivariate statistical analyses our numerical simulation show a large inundation of the estuary with flow depths varying from 0 5 to 6 m and run up of 7 m magnetic data show a dominance of paramagnetic minerals quartz mixed with lesser amount of ferromagnetic minerals namely titanomagnetite and titanohematite both of a detrital origin and reworked from the underlying units multivariate statistical analyses indicate a better connection between the tsunami induced deposit and a mixture of units c and d all these results point to a scenario where the energy released by the tsunami wave was strong enough to overtop and erode important amount of sand from the littoral dune and mixed it with reworked materials from underlying layers at least 1 m in depth the method tested here represents an original and promising tool to identify tsunami induced deposits in similar embayed beach environments

the age of the palaeodunefield of the northern murray basin in south australia preliminary results abstract a vast field of old desert dunes extends from northwestern eyre peninsula across yorke peninsula and the northern adelaide plains into the murray basin and northwestern victoria there are patches of parabolic forms but the sand ridges under review are of seif linear or longitudinal type they trend nw se in the west and west east in the east here we record luminescence dates for three dune sites in the waikerie district of the northwestern murray basin they range from respectively 151 25 3 ka 157 33 3 ka and a basal age of 59 6 ka with sand movement also indicated around 1906 and 1933 ce apart from the last named no unconformities are discernible in the sampled sections

palaeomagnetic stratigraphy of lake bungunnia plio pleistocene precursor of aridity in the murray basin southeastern australia abstract the murray darling river system in southeastern australia formerly flowed into a large lake lake bungunnia before reaching the sea fine grained clastics of this system the blanchetown clay formation extend over an area of about 68 000 km2 underlying the mallee region with its surface array of dunes and salt lakes palaeomagnetic analyses are used to date the major hydrologic transition from the expansive freshwater system to the saline deflation playas and dunes that characterize this landscape today two sites were selected for sampling one a cliff section on the left bank of the murray river at chowilla the other from within sediments of lake tyrrell a saline playa cut into sediments of the older freshwater system two sequences were sampled at tyrrell one by coring to 30 m in the basin centre the other a composite cliff and 5 m core on the western margin of the playa post bungunnia sediments representing modern landforms were sampled in both surficial dune palaeosol units of the woorinen formation and in saline sediments the tyrrell beds within the modern saline playa the sequence of multiple aeolian units of the woorinen formation and gypseous sediments of the tyrrell beds are normally magnetized indicating deposition within the past 0 7 million years by contrast the uppermost horizons of bedded blanchetown clay below a surface zone of pedogenic alteration are reversed the brunhes matuyama b m boundary key to the age of draining of lake bungunnia by deepening the overflow channel to the sea is obscured within the zone of pedogenesis separating unaltered blanchetown clays from overlying aeolian deposits the onset of aeolian and saline gypseous deposits characteristic of the arid zone facies is placed soon after the b m boundary about 500 000 years ago sequences through the blanchetown clay pass down through the matuyama reversed chron into the gauss normal chron with the lowermost section on the tyrrell west bank recording a basal reversed zone of possible gilbert age thus the origins of lake bungunnia extend back beyond basal pleistocene into the late pliocene the lake s duration covers more than 2 million years spanning the plio pleistocene boundary in this important region of southeastern australia

stratigraphy sedimentology chronology and palaeohydrology of quaternary lacustrine deposits at madigan gulf lake eyre south australia abstract madigan gulf is a large bay at the southern end of lake eyre north a major ephemerally flooded playa in arid central australia at the southwestern margin of a vast 1 300 000 km2 internal drainage basin the stratigraphy and chronology of the quaternary sequence in the gulf is described from 8 cores and a cliff exposure at the gulf margin a number of depositional environments are recognised and their distinctive sedimentary components are described facies recognised include deep and shallow water lacustrine environments dominated by surface water processes and dry or ephemerally flooded playa environments dominated by groundwater controlled processes sedimentary components include terrigenous clastics from river inflow and shoreline erosion carbonates of detrital inorganic or biological origin and gypsum and halite evaporites carbonates and gypsum evaporites precipitated within the basin are frequently reworked as clastic components the establishment of a preliminary chronology for the sequence by the application of thermoluminescence uranium thorium disequilibrium amino acid racemization and radiocarbon dating techniques has allowed a reconstruction of the last 130 ka of lake eyre palaeohydrology the wettest phase occurred during the last interglacial early in oxygen isotope stage 5 when an enlarged lake eyre was up to 25 m deep subsequently there has been a number of dry periods separating successively less effective wet phases culminating in the deposition of a substantial halite salt crust around the time of the glacial maximum the dry interludes are characterised by deflation of salts and sediment from the basin a process controlled by lowering of the watertable the record from madigan gulf demonstrates the dramatic and repetitive impact of lake deflation on the quaternary record of lake eyre in the early holocene a minor but mostly perennial lacustrine event was terminated at about 3 4 ka when the modern ephemeral playa regime was established the major catchment of lake eyre is located in the monsoon watered areas of northern australia as demonstrated by large floodings of the modern ephemeral regime major lacustrine episodes must indicate enhanced monsoon precipitation in northern australia in the holocene the lake has not risen to levels achieved during the early stage 5 lacustral phase indicating a marked reduction in the effectiveness of the monsoon in the present interglacial by comparison with its predecessor

quaternary soil salinity events and australian vegetation history abstract a late quaternary history of australian soil salinization is produced by comparing chenopodiaceae and casuarina pollen curves although salinity development varied between sites its occurrence was generally associated with arid phases and when high rainfall or high sea level caused regionally high groundwater tables soil salinization contributed to the shift from casuarina to eucalyptus dominance of interglacial sclerophyll vegetation the deposition of saline sediments deflated from the murray basin seems more likely than aboriginal burning to have caused the decline of casuarina at lake george soil salinization probably resulted in other vegetation changes and must be taken into account in environmental reconstructions the renewed increase in soil salinity caused by european land use practices and an associated decline in casuarina are evident in the pollen records of many sites

analyzing the spatial occurrence of high alumina clays brazil using electrical resistivity tomography ert mottled and high alumina clay horizons gleysols above dismantled iron crusts ferralsols are widespread in the soils that developed on the flat sedimentary plateau located in western minas gerais state brazil field exploration shows that the deposits of high alumina clays are located at a lower topographic position mottled horizons suggesting a lateral transformation system two dimensional and pseudo three dimensional electrical resistivity tomography ert techniques have been tested to investigate the distribution of high alumina clay layers in a thick lateritic mantle and to assess the potential of the technique to delimitate ore reserves the figures of resistivity based on spatial variations of electrical properties of the weathering layers showed spatial changes in the subsurface structure of weathering mantle expanding the distribution of iron crust and the high alumina clay layers which are strongly influenced by aquifer combining 2d and pseudo 3d geophysical images with soil morphology and geochemistry we delimitate the high alumina clay layer and discuss its genesis the ore is located exclusively on the edge of the plateau and is closely linked to the development of hydromorphic soils exactly where the vertical water flow is restrained by the iron crust this distinct water regime defines the geochemical transfers in soil mantle depleting fe2o3 from gleysol and correspondingly increasing al2o3 and sio2 this study aimed to evaluate the potential of ert as a prospecting tool for supergene ore and as a technique with reduced environmental impact in the mineral research when compared to the pre existing exploration methods trenches drill holes and extraction that are applied on this sensitive wetland system in which high alumina clays may occur

late miocene pliocene coastal acid sulphate system in southeastern australia and implications for genetic mechanisms of iron oxide induration abstract ferricrete sediment cemented by iron oxides and hydroxides is common in subaerial weathering environments around the world formed under alternating oxidising and reducing conditions ferricretes record pedogenetic processes of translocation and concentration of iron and trace elements in the soil given their stability and high preservation potential ferricretes can provide insights to ancient soil forming and weathering processes in this study the key processes controlling ferricrete geochemistry in a neogene strandplain are identified and interpreted in the context of a coastal acid sulphate weathering system textural and geochemical variations in sediment indurated by hematite and goethite represent a record of in situ induration erosion and reworking this development took place within an environment of fluctuating ph and eh and subaerial wetting and drying cycles we distinguished depositional and post depositional processes based on the results of whole rock geochemistry hyperspectral mineralogy and major and trace element maps of petrographic thin sections the ferricretes have three morphological types flat lying indurations concentric pisoliths and rounded nodules with fragmented internal textures successive laminae of fe oxides and hydroxides in all morphological types of ferricrete have variable fe al and si abundances reflecting cyclic precipitation and groundwater chemistry changes episodic wetting and drying of near coastal sediments was superimposed on a long term trend of marine regression and local tectonic uplift from 7 ma to present this resulted in the diachronous exposure of relatively reduced shoreline sediments and concomitant acid production due to ferrolysis and the oxidation of biogenic sulphide local landform variations contributed to a wide variety of pedogenic processes and subsequent ferricrete formation acid sulphate weathering recorded by these indurated sediments is similar to conditions that are observed at present in the shallow water estuary of the lower lakes near the mouth of the murray river

14c analysis of aliphatic hydrocarbon fractions from the hypersaline lake tyrrell southeast australia conventional biomarker studies typically interpret the distribution structure and stable isotopic e g 13c d composition of sedimentary hydrocarbons and polar compounds however compound and compound class specific 14c analysis csra is becoming increasingly relevant for characterising millennial scale residence and mobilisation of sedimentary organic carbon oc here the 14c content of the aliphatic and bulk fractions from shallow cores from the hypersaline playa lake tyrrell southeast australia were compared the aliphatic hydrocarbon fractions predominantly n alkanes were substantially older than the corresponding bulk fractions indicating the presence of active reservoirs of ancient carbon likely derived from aeolian reworking of sediments the 14c ages of the aliphatic hydrocarbons in the core revealed two noticeable shifts in age and source of ancient oc that were not apparent using biomarker composition and sedimentology alone the study shows that aliphatic hydrocarbons are relatively simple to isolate even from organically lean ca 0 05 toc terrestrial sediments and their 14c ages yield information about carbon mobilisation and preservation not amenable to conventional analysis

mineral sands occurrences in the murray basin southeastern australia the murray basin in southeastern australia is proving to be a major mineral sand province that eventually will replace australia s east and west coasts in production of rutile zircon and ilmenite concentrations of relatively coarse grained heavy mineral occur as beach placers in the pliocene loxton parilla sands in the upper part of the murray basin sequence these formed as 400 km long barrier complexes in the murravian gulf under the action of long period ocean swell waves we think the main source of barrier sand at least initially was from erosion of miocene sands on the bed of the murravian gulf progradation was a response to sea level fluctuations linked to milankovitch climatic cycles in the pliocene in most areas the resulting 400 km wide barrier strand plain is now overlain by fluvial aeolian and lacustrine deposits typically the heavy mineral deposits are ilmenite rich with 30 to 40 percent rutile and zircon they occur as single or as multiple stacked strandline deposits are often more than 10 m thick have mineral grades that exceed 20 percent in places are several hundred meters wide and 10 to 25 km long some contain up to several million tonnes of heavy mineral the rutile and zircon are comparable in grain size and quality to minerals traditionally mined in australia many of the deposits are associated with topographic ridges the neckarboo and iona ridges are the best known that appear to be fault bounded blocks deposits of major commercial significance found so far contain a total of over 12 million tonnes mt of rutile zircon and ilmenite the total coarse grained mineral sand resources in the murray basin are conservatively estimated to be over 50 mt the distribution of mineral sands in the murray basin seems to be associated with two aspects of the region s geology and geomorphology 1 a zone bordering the central part of the basin where the pliocene barriers were derived from underlying miocene sands that probably already contained some mineral concentrations and 2 growth faulting with deposits preferentially occurring on upfaulted blocks especially in the zone defined by 1 above we speculate that localized uplift during the formation of the loxton parilla barriers was sufficient to modify coastal processes on uplifted blocks so as to increase the rate of alongshore sediment bypass compared to nearby areas this phenomenon has been simulated in computer modeling where the barrier sands were already enriched in heavy minerals winnowing by storm waves formed beach placers on the uplifted fault blocks based on criteria 1 and 2 the prospective areas of the murray basin account for 80 percent of the beach placers found to date

alluvial evidence for major climate and flow regime changes during the middle and late quaternary in eastern central australia as a low gradient arid region spanning the tropics to the temperate zone the lake eyre basin has undergone gentle late cenozoic crustal warping leading to substantial alluvial deposition thereby forming repositories of evidence for palaeoclimatic and palaeohydrological changes from the late tertiary to the holocene auger holes and bank exposures at five locations along the lower 500 km of cooper creek a major contributor to lake eyre in the eastern part of the basin yielded 85 luminescence dates tl and osl that combined wit a further 142 luminescence dates from northeastern australia have established a chronology of multiple episodes of enhanced flow regime from about 750 ka to the holocene mean bankfull discharges on cooper creek upstream of the innamincka dome at 250 230 ka or oxygen isotope stages ois 7 6 are estimated to have been 5 to 7 times larger than those of today however substantially less reworking has occurred during and after ois 5 than before lower cooper creek appears to have similarly declined in the tirari desert adjacent to lake eyre there is evidence of widespread alluvial activity perhaps during but certainly before the middle pleistocene yet the river became laterally restricted in ois 7 to 5 while the quaternary has been characterised by a dramatically oscillating wet dry climate since oxygen isotope stage ois 7 or 6 there has been a general decline in the magnitude of the episodes of wetness to which the eastern part of central australia has periodically returned during the last full glacial cycle cooper creek s periods of greatest runoff and sand transport were not during the last interglacial maximum of ois 5e 132 122 ka but later in ois 5 when sea levels and global temperatures were substantially below those of 5e or today fluvial activity returned in ois 4 and 3 but not to the extent of mid and late ois 5 strongly seasonal but still powerful flows transported sand and fed source bordering dunes in ois 5 and 3 this chronology of fluvial activity in the late quaternary broadly coincides with that for rivers of southeastern australia and suggests that the wet phases in eastern central australia have not been governed as much by the northern monsoon as by conditions in the western pacific close to the east coast both north and south flow confinement within the innamincka dome has locally amplified cooper creek s energy and here evidence exists for short but high magnitude episodes of flow during the last glacial maximum and in the early to middle holocene conditions that were capable of forming large palaeochannels but that were not long lived enough to rework the river s extensive floodplains elsewhere along its length

the epigenetic replacement of kaolinite by hematite in laterite petrographic evidence and the mechanisms involved abstract this paper describes the petrographical and mineralogical transformations accompanying the accumulation of iron oxides within the deep mottled layer of a laterite from burkina faso in this layer the proportions of purple red hematitic spots or nodules which form at the expense of volumes occupied by a soft microporous kaolinite plasma increase as the surface of the soil is approached the antagonism between hematite and kaolinite was observed at different levels in all cases from the border to the core of the hematitic domains kaolinite experiences corrosion soon followed by complete destruction at this later stage hemalite crystals are organized into thin lamellar structures showing clearly the shapes of former kaolinite platelets a mechanism explaining coincidence of the accumulation of hematite with the destruction of kaolinite is proposed we postulate that in the deep layers of laterites fed by fe 2 solutions the protons necessary to dissolve kaolinite are generated by a reaction similar to the oxidation hydrolysis step of ferrolysis in the mottled layer of this laterite therefore the progressive building up of a high concentration of iron appears to be the result of two closely related processes i e the precipitation of iron oxides from solution and the concommitant dissolution of kaolinite

lake bungunnia a plio pleistocene megalake in southern australia abstract between 2 5 ma and 0 7 ma a plio pleistocene megalake lake bungunnia existed in the western murray basin australia study of hydrologic and geologic constraints on this lake has enabled the climate of southeastern australia during the late pliocene and early pleistocene to be partly quantified modelling shows that lake bungunnia could not exist under current climatic conditions and that an average rainfall of at least 500 mm yr 1 over the catchment of the murray darling river system was likely considerably more than at present minor changes in climate caused large fluctuations in the shoreline of the shallow lake which are reflected in the geologic record possible histories for lake bungunnia are suggested in the light of this evidence demise of the megalake heralded the onset of aridity in southern australia and modern landforms date from that time salt lakes in part of the western murray basin may have directly descended from lake bungunnia

late quaternary lake level changes and climates of australia abstract spatial and temporal patterns in lake level data from 38 sites in australia and papua new guinea provide a basis for reconstructing changes in water balance and atmospheric circulation during the past 30 000 years the reconstructions are consistent with hydrological changes inferred from pollen analysis and palaeowind directions inferred from dunes generally wetter conditions between 30 000 and 24 000 bp are consistent with a strong walker circulation with the sta near its present position general aridity at the glacial maximum until 12 000 bp with higher than present lake levels in the southeastern interior of australia implies that the southern margin of the subtropical anticyclone belt was expanded southward and the southern westerlies were correspondingly displaced this southward shift appears in all gcm simulations of the 18 000 bp climate and may be a result of the increased vigour of the northern hemisphere circulation a northward migration of the belt of high lake levels between 11 000 and 6000 bp suggests that the sta shifted back equatorward to north of its present position relaxation to modern conditions occurred after 6000 bp interrupted by an unexplained dry phase 6000 5000 bp in tasmania and queensland

tectonism and eustasy across a late miocene strandplain the loxton parilla sands murray basin southeastern australia abstract sediments of the loxton parilla sands form a progradational strandplain that stretches for over 350 km across the murray basin in southeastern australia the strandplain comprises over 600 individual ridges with stratigraphic and strontium isotope data indicating these strandlines are late miocene to early pliocene in age with deposition beginning before 7 2 ma and terminating at approximately 5 0 ma post pliocene uplift along the padthaway high due to regional compressive intraplate tectonism was responsible for altering the orientation of strandlines and drainage systems as well as contributing to increased erosion across the strandplain this uplift both restricted and starved the coastline of sand sized sediment changing the depositional environment from one of progradation to active erosion this produced a series of scarps along the southwestern murray basin and ultimately contributed to the formation of the kanawinka escarpment a large erosional cliff feature whose formation was not exclusively the result of fault related tectonism this evidence for pliocene tectonism along southeastern australia together with the depositional ages inferred from strontium isotope analysis indicates that contrary to previous work the strandlines of the loxton parilla sands do not represent an unbroken record of late miocene pliocene glacioeustatic change we estimate that approximately 3 ma of depositional history may be missing from the sedimentary record between the southwestern most loxton parilla sands strandlines and those of the pleistocene bridgewater formation

radiocarbon dating of playa lake hydrologic changes examples from northwestern china and central australia accurate radiocarbon dating of arid zone playas is restricted by shortage of suitable organic matter analyses from two large systems in australia lake frome and china qarhan playa in the qaidam basin demonstrate the problems associated with the use of carbonates for dating organic carbon although requiring treatment of large samples 1 2 kg provides the most accurate basis for establishing chronologic control in qarhan a deposit of halite averaging about 30 m thick extends over an area of 5800 km2 carbonate in the system is dominantly derived as clastics from loess transported by northwesterly winds the large component of dead carbon thus involved explains anomalous patterns of dates derived from these materials such results are consistently much older than those based on organic carbon in lake frome subject to a more maritime climate in central australia the carbonate component is dominantly authigenic lacustrine in origin contaminated by a small detrital component it provides ages about one half life older than those from organic carbon the sequence from qarhan supplemented by evidence of lacustral pluvial episodes in two other sub basins in qaidam kunteyi and xiao qaidam illustrates the presence there of expanded waterbodies persisting from at least 40 000 to about 15 000 yr b p in areas where little surface water persists today the large evaporite deposits formed between about 25 000 to sometime after 15 000 yr b p holocene climate appears to have remained hyperarid like that of today at lake frome an early lacustral phase gave way before 18 000 yr b p to drying and aeolian activity water had returned to the system by 16 000 yr b p signalling a decline if not the end of aridity lacustrine conditions persisted through early holocene with drying and development of playa facies about 7000 yr b p after a brief return to lacustrine conditions between about 6000 4000 yr b p a dry playa environment has continued to the present day the frome and qarhan playas although in comparable latitudes lie in very different climatic and tectonic settings their palaeohydrologic records are neither in phase nor in distinct anti phase emphasizing the complexity of comparing palaeoclimatic records from different circulation systems

soil evolution evidence from southern australia abstract soil evolution in southern australia has been studied by stratigraphic analysis of the regolith the sedimentary record shows that tectonics is followed by marine transitional and continental deposition and finally soil formation these episodes are repeated on a time scale shortening geometrically soil is formed in the upper layered part of the regolith where materials and processes are involved in and with the biosphere both physical and chemical layers are included in the concept where a break in soil formation is followed by the development of younger material either sediment or soil a paleosol can be recognised the layer in the paleosol of prime importance from a stratigraphic point of view is the horizon of accumulation which characterises the soil of the time paleosols record climates of the past which prevailed over wide areas soil formation is episodic assemblages of paleosols constitute soil profiles and record interrupted pedogenesis soil zonation begins with the development of paleosols at particular times in the past there is general distribution of great soil groups in southern australia from older soils with fossil silcrete pans and fossil lateritic soils of the inland to younger poorly differentiated coastal sands and solonchaks of the coastal margin this is due partly to uplifting of the older basin margins inland and downwarping near the coast and to cyclic incision of exoreic drainage on the continental margin as a result of the interplay between climate and first and second order geomorphic structures a similar but local relationship occurs between older soils in the ranges and younger soils in saline depressions inland or estuarine plains on the coastal margin

process based modeling of tsunami inundation and sediment transport 1 the infrequent and unpredictable nature of tsunamis precludes the use of field experiments to measure the hydrodynamic and sediment transport processes that occur instead these processes are often approximated from laboratory numerical and theoretical studies or inferred from observations of the resultant sediment deposits here delft3d a three dimensional numerical model is used to simulate the inundation and sediment transport of a tsunami similar in magnitude to the 26 december 2004 indian ocean tsunami over one measured and three idealized morphologies the model is first shown to match well the observations taken at kuala meurisi sumatra and then used to examine in detail the processes that occur during the tsunami the model predicts that at a given cross shore location the onshore flow accelerates rapidly to a maximum as the wavefront passes and then gradually decelerates before reversing direction and flowing offshore the onshore flow does not tend to zero everywhere at maximum inundation but instead flow reversal occurs near the shoreline even as the wavefront continues to inundate landward while some sediment is eroded by the passing wavefront the suspension of sandy sediment is dominated by the long duration high velocity backwash that occurs along the beach face and offshore of the shoreline some of the sediment suspended during backwash is advected shoreward by the subsequent wave creating large spatial gradients in the suspended sediment concentrations which may not be in equilibrium with the local hydrodynamics the inundation and transport of sediment during a tsunami can be affected by complexities in the morphological profile and interactions between multiple waves and many of the hydrodynamic and sediment transport processes predicted here are similar to analogous processes previously observed in the swash zone

self organization in chemical lateritic weathering abstract ferruginous laterites consist of different superposed horizons characterized by their mineralogical and structural composition climatic changes are foremost among the parameters used to explain variations of mineralogy and structures however several types of structures can be explained as the spontaneous and autonomous change of the geochemical soil system without the intervention of external factors such as climate or tectonics two examples illustrate this self organization of lateritic horizons formation of a ferruginous nodular horizon and formation of a conglomeratic iron crust self organization results from reaction transfer feedbacks between permanently precipitated and dissolved minerals and continuously percolating solutions allowing the geochemical soil system to be in constant search of equilibrium

subdividing the pleistocene using the matuyama brunhes boundary mbb an australasian perspective abstract the last major reversal of the earth s magnetic field the matuyama brunhes boundary mbb dated at 0 78 ma is widely identified in australian and new zealand pleistocene deposits in new zealand the mbb is precisely located in shallow marine sediments of wanganui basin where it corresponds with the base of the new zealand putikian substage a combination of marine biostratigraphy sequence stratigraphy and tephrostratigraphy permit correlation from wanganui basin to other on land sections and deep sea cores in australia the mbb is identified in many continental sequences particularly saline lake basins however chemical weathering has resulted in variable brunhes age normal overprints that are sometimes difficult to remove australasian tektites are a potential lithostratigraphic marker just prior to the mbb but have yet to be identified in the same on land section as the mbb in australia identification of reverse polarity magnetisation in weathered deposits including soils provides a minimum age of 0 78 ma for these materials a widespread arid shift in paleoclimate succeeded the mbb in australia placement of the lower middle pleistocene boundary at the mbb would constitute the most recognisable chronostratigraphic marker in weathered continental deposits

magnetic polarity stratigraphy of the pleistocene section at portland victoria australia abstract three to seven oriented paleomagnetic samples were collected from 16 sites in the nelson bay and bridgewater formations at portland victoria which contains the recently discovered nelson bay local fauna l f the entire section has reversed polarity these results along with globorotalia truncatulinoides within the section and the presence of underlying middle pliocene dated basalts indicate that the portland section and the included nelson bay l f was deposited within the late matuyama chron between 1 66 and 0 73 myr ago this represents the first well documented pre 14c pleistocene mammalian fauna in australia calibrated in direct stratigraphic context with absolute dating methods in addition the reversed polarity for the bridgewater formation confirms the previous hypothesis that the depositional history of this beach sand deposit is time transgressive across the brunhes matuyama boundary

identification of tsunami induced deposits using numerical modeling and rock magnetism techniques a study case of the 1755 lisbon tsunami in algarve portugal abstract storm and tsunami deposits are generated by similar depositional mechanisms making their discrimination hard to establish using classic sedimentologic methods here we propose an original approach to identify tsunami induced deposits by combining numerical simulation and rock magnetism to test our method we investigate the tsunami deposit of the boca do rio estuary generated by the 1755 earthquake in lisbon which is well described in the literature we first test the 1755 tsunami scenario using a numerical inundation model to provide physical parameters for the tsunami wave then we use concentration ms sirm and grain size arm arm b1 2 arm sirm sensitive magnetic proxies coupled with sem microscopy to unravel the magnetic mineralogy of the tsunami induced deposit and its associated depositional mechanisms in order to study the connection between the tsunami deposit and the different sedimentologic units present in the estuary magnetic data were processed by multivariate statistical analyses our numerical simulation show a large inundation of the estuary with flow depths varying from 0 5 to 6 m and run up of 7 m magnetic data show a dominance of paramagnetic minerals quartz mixed with lesser amount of ferromagnetic minerals namely titanomagnetite and titanohematite both of a detrital origin and reworked from the underlying units multivariate statistical analyses indicate a better connection between the tsunami induced deposit and a mixture of units c and d all these results point to a scenario where the energy released by the tsunami wave was strong enough to overtop and erode important amount of sand from the littoral dune and mixed it with reworked materials from underlying layers at least 1 m in depth the method tested here represents an original and promising tool to identify tsunami induced deposits in similar embayed beach environments

geomorphic and pedogenic evolution in coastal sediments central california abstract studies of soil chronosequences on marine terraces facilitate the use of terraces for tectonic and paleoclimatic interpretation however many areas on the california coast have received substantial eolian deposits after pedogenesis began so do not qualify as chronosequences these areas are worthy of study because they are widespread coastal landscape features and they enable us to interpret pedogenic and geomorphic processes in sandy regolith the objective of this study was to use soil and deep regolith morphology and chemistry to interpret pedogenic and geomorphic evolution on a sequence of four marine terraces san luis obispo county california the terraces are numbered 1 2 3 and 4 from oldest to youngest the eroded terrace platforms have been tentatively dated at 560 420 or 480 320 and 120 ka respectively the sand deposits on each platform may be considerably younger the amount of land surface dissection and the depth of stream incision increase with increasing terrace age and elevation morphological features suggest that the soils xeropsamments on terrace 4 haploxerolls on terrace 3 on the two youngest terraces are well drained and their morphological development is typical of soils in eolian sand deposits morphological and chemical features of the basal regolith contrast with those of the soils clay fe oxides and opaline silica were deposited by groundwater flow above the bedrock platform above the shoreline angle where the deep regolith receives additional groundwater from higher terraces redoximorphic features have developed gray mottles are larger more common and more distinct in the basal regolith of progressively older terraces erosion has removed much of the overburden on terraces 2 and 1 and soils epiaqualfs on terrace 2 epiaqualfs on terrace 1 have developed in what was once deep regolith the landscape soils and deep regolith show an evolution of processes whereby the path and direction of water movement through the regolith is controlled first by terrace morphology and stratigraphy then by the development of pedogenic features in the soil and deep regolith and by terrace dissection

paleosols in laterite and silcrete profiles evidence from the south east margin of the australian precambrian shield abstract laterite and silcrete profiles are common in the arid and semi arid areas of the australian precambrian shield a vast planar surface masked by the regolith much of the geological history of the shield subsequent to its early development is recorded in ancient cover rocks and younger basin sediments which occur in important stratigraphic sequences particularly on the margins of the shield within these sequences stratigraphically associated or as companion materials weathering zones and paleosols were developed which individually and as assemblages of layers and horizons record the history of weathering and of soil formation since the proterozoic laterite and silcrete profiles are seen to be assemblages of paleosols stratigraphically associated deposits and companion materials which were formed in response to changes in groundwater conditions at particular times in the past the paleosols record the evolution of the regolith older weathering zones and bleached rocks were features of successive landscapes after the early palaeozoic ferruginous mottling ferricrete and silcrete pans were formed after the early cainozoic ferricretes and mottled clay paleosols some of which have been described as laterite were formed during and after the pliocene materials in laterite and silcrete profiles are overlain in places by calcretes formed after the early pleistocene and by younger soils the assemblages are distinctive and are characteristic of particular morpholithogical provinces

stratigraphy of washover deposits in florida implications for recognition in the stratigraphic record abstract twelve washover deposits were cored on the west central gulf coast of florida to provide data to permit development of a model to help identify washover facies in the stratigraphic record typical modern washover stratigraphy displays landward dipping plane beds comprised of well sorted sand with distinct laminae of shells and heavy minerals five subfacies are delineated which show variations in composition texture and bioturbation throughout the washover facies these subfacies represent differences in flow conditions during overwash position relative to sea level and variable degrees of reworking after deposition three shell assemblages aid in identification of washover deposits backbarrier sediments composed of shoreface open water species or mixed shoreface backbarrier species may potentially be washover in origin sediments with purely backbarrier quiet water shell species are likely to have been deposited independently of washover activity examination of washover deposits of differing ages reveals that preservation of washover stratigraphy is not exclusively a function of time reworking of small scale stratification can occur in as short as a decade however this same stratification was found to be preserved in deposits several hundred years old destruction of original washover signatures is related to the position of the deposits relative to sea level and the rate and depth of burial even after the destruction of small scale stratigraphic features washover deposits may still be identified as such due to their texture composition and shell assemblages key features in recognizing the facies after bioturbation and reworking are 1 the presence of clean sand in otherwise muddy backbarrier sediments 2 the landward thinning of the facies and 3 the presence of shoreface shells or mixed shoreface backbarrier shells on landward portions of the barrier island system if reworking is severe and or there are limited subsurface data distinguishing washovers from genetically similar deposits e g flood tidal deltas and spillover deposits in the stratigraphic record is difficult and when considered out of stratigraphic context may not be recognizable

petrological and geochemical differentiation of lateritic iron crust profiles abstract lateritic iron crust profiles developed from metabasic rocks in west africa burkina faso were studied from a petrographical and geochemical point of view at the base of profiles a thick gray purple kaolinitic horizon occurs with frequent macroscopic preservation of original pre existing structures in such an horizon chemical balances clearly show that part of kaolinite crystals could be explained by an absolute accumulation from circulating solutions higher up in the profiles fe accumulation leads to two main facies purplered hematitic spots and nodules and yellow kaolinitic and goethitic spots mottled clay horizon hematite and goethite distribution in that horizon is regulated by water activity in microenvironments hematitic nodules form as kaolinite crystals are completely dissolved in goethitic spots fe accumulation is much less abundant and the first generation of well crystallized kaolinite is replaced by a poorly crystallized and smaller kaolinite crystals showing a greater substitution of al 3 for fe 3 in the upper part of profiles all the kaolinite is gradually dissolved and the maximum of ferruginous concretion formation leads to a hard and nodular iron crust

sandstone weathering a century of research and innovation abstract a review of sandstone weathering research particularly in the past 100 years reveals a trajectory of enquiry from early description and classification of features to development of process based explanations to decreasing scales of investigation and a disparity between understanding of process es and explanations of the genesis of sandstone weathering features developments in expositions on mesoscale weathering features on sandstone surfaces are discussed demonstrating a range of approaches to weathering phenomena field based and laboratory based that must be linked to provide an explanation of observed features on a landform scale throughout the twentieth century a thematic chronology highlights certain trends in research description of forms often in arid and semi arid environments single process form models an emphasis on experimentation difficulties in measuring weathering rates and a persistent emphasis on physical causes of breakdown a new research agenda is promoted in which biodeterioration and chemical processes gain parity a holistic approach based on conceptual modeling of weathering systems gains prominence and scale issues are addressed more rigorously

tsunami sediments and their foraminiferal assemblages abstract tsunami hazard assessment begins with a compilation of past events that have affected a specific location given the inherent limitations of historical archives the geological record has the potential to provide an independent dataset useful for establishing a richer chronologically deeper time series of past events recent geological studies of tsunami are helping to improve our understanding of the nature and character of tsunami sediments wherever possible geologists should be working to improve the research tool kit available to identify past tsunami events marine foraminifera single celled heterotrophic protists have often been reported as present within tsunami deposited sediments but in reality little information about environmental conditions and by analogy the tsunami that deposited them has been reported even though foraminifera have an enormous capacity to provide meaningful palaeo environmental data here we review what foraminifera are describe their basic form and significance summarise where they have been reported in tsunami sediments and identify what can be learnt from them we review the gaps in our understanding and make recommendations to assist researchers who examine foraminiferal assemblages in order to enhance their use within tsunami geology

stratigraphic architecture resulting from late quaternary evolution of the riverine plain south eastern australia the riverine plain of south eastern australia is the result of prolonged cenozoic fluvial activity single thread anabranching and distributary channels and floodplains and associated aeolian dunes characterize the uppermost sequences based on detailed interpretations of late quaternary fluvial sedimentation and surficial stratigraphy for this 77 000 km2 basin earlier prior stream and ancestral stream models of fluvial deposition deduced from limited stratigraphic and chronological evidence are replaced with aggradational palaeochannel and migrational palaeochannel models thermoluminescence dating reveals four distinct phases of palaeochannel activity between 105 and 12 ka the first coleambally phase late in oxygen isotope stage 5 the second kerarbury phase in stage 3 the third gum creek phase before and the fourth yanco phase after the last glacial maximum lgm in stage 2 the first three of these phases were characterized by mixed load laterally migrating sinuous palaeochannels with occasional transitions to a straighter bedload dominated mode and vice versa the first two phases concluded with a bedload dominated episode resulting in aggradational palaeochannels on the surface of the plain and the third phase prior to the lgm did also in its downstream reaches the phase following the lgm was characterized entirely by large mixed load sinuous migrational palaeochannels these exhibited no terminating bedload episode because the onset of holocene climates reduced the size of the flood peaks greatly diminished the supply of bedload from the upper catchments and resulted in streams evolving to their present highly sinuous suspended load form the result is a complex stratigraphic architecture consisting of vertically and laterally accreted units extending over hundreds of kilometres in the form of channel sand stringers sand sheets and derivative aeolian dunes partially or wholly encased in overbank fines

aeolian fluvial interaction and climate change source bordering dune development over the past 100 ka on cooper creek central australia abstract this study provides an interpretation of interrelated quaternary fluvial and aeolian activity related to climate change on cooper creek in the lake eyre basin in southwestern queensland central australia the extensive muddy floodplain is characterised by buried sandy palaeochannels now almost entirely invisible but stratigraphically connected to source bordering dunes that emerge as distinctive sandy islands through the floodplain surface luminescence dating has identified pronounced periods of fluvial activity represented by abundant sandy alluvium from marine isotope stages mis 8 3 while all these sandy fluvial episodes on cooper creek were much more powerful than anything subsequent they appear to be ranked in order of declining activity mis 8 6 saw reworking of almost the entire floodplain whereas subsequent phases of reworking were far less extensive source bordering dunes were derived from active sandy channels in late mis 5 85 80 ka and mid mis 3 50 40 ka after 40 ka sand channel activity largely ceased and the floodplains and channels were inundated with mud isolating the dunes as emergent features although aeolian reworking of the upper parts of some dunes has continued to the present they show remarkable resilience having survived without appreciable migration for at least 40 ka whilst the channels once determined the location of source bordering dunes in an interesting role reversal the remnant dunes now determine the position of many contemporary flood channels and waterholes by deflection and confinement of overbank flows

last glacial cycle hydrological change at lake tyrrell southeast australia abstract lake tyrrell is the largest playa in the murray basin of southeast australia optical dating of transverse dune lunette sediments extends the lake s radiocarbon chronology to the last interglacial period the highest lake level was attained 131 000 10 000 yr ago forming lake chillingollah a megalake that persisted until around 77 000 4000 yr ago pedogenesis of its sandy lunette continued until buried by a silty clay lunette deflated from the lake floor 27 000 2000 yr ago the dated soil stratigraphic units correlate with the upper tyrrell beds and contain evidence that humans visited the lakeshore before 27 000 yr ago the lake chillingollah megalake was synchronous with very high lake levels in monsoon dominated australia yet it was not influenced by tropical monsoon systems it was filled instead by increased winter rainfall from westerly low pressure fronts greater effective precipitation across australia is evident the result of a weakened subtropical high pressure zone

indonesian throughflow drove australian climate from humid pliocene to arid pleistocene late miocene to mid pleistocene sedimentary proxy records reveal that northwest australia underwent an abrupt transition from dry to humid climate conditions at 5 5 million years ma likely receiving year round rainfall but after 3 3 ma climate shifted toward an increasingly seasonal precipitation regime the progressive constriction of the indonesian throughflow likely decreased continental humidity and transferred control of northwest australian climate from the pacific to the indian ocean leading to drier conditions punctuated by monsoonal precipitation the northwest dust pathway and fully established seasonal and orbitally controlled precipitation were in place by 2 4 ma well after the intensification of northern hemisphere glaciation the transition from humid to arid conditions was driven by changes in pacific and indian ocean circulation and regional atmospheric moisture transport influenced by the emerging maritime continent we conclude that the maritime continent is the switchboard modulating teleconnections between tropical and high latitude climate systems

responses of quaternary rainforest vertebrates to climate change in australia a new previous termmiddle pleistocenenext term vertebrate fossil record from eastern australia dated by u disequilibrium series records the first quaternary record of an australian tropical rainforest fauna this exceptionally rich fauna underwent extinction after a long period of relative faunal stability spanning several glacial cycles and persisted probably until 280 000 years ago some time between 280 000 and 205 000 years ago the rainforest fauna was replaced by a xeric adapted fauna since that time the xeric adapted fauna was replaced by a mesic adapted fauna which was established by the holocene this is the first vertebrate faunal evidence in australia of the previous termmiddle pleistocenenext term mid brunhes climatic event mbe a major climatic reorganisation that led to increased aridity in northern australia from around 300 000 years ago several independent palaeoclimate proxies suggest that the climatic shift to aridity was due to increased climatic variability and weakened northern monsoons which may be manifested in the extinction of the aseasonal rainforest fauna and its replacement by an arid adapted fauna we extend the temporal ranges of several taxa from the pliocene into the previous termmiddle pleistocene next term we also reveal a longer palaeobiogeographic connection of rainforest taxa and lineages shared between new guinea and australia than was previously thought and show that their extinction on mainland australia occurred sometime after 280 000 years ago

sedimentary features of tsunami deposits their origin recognition and discrimination an introduction the occurrence of numerous recent large tsunami suggests that they are a common natural event yet tsunami deposits in the geological record are rare this apparent anomaly may be due to a real infrequency of events and or poor preservation potential but alternatively may be due to misidentification robust criteria for the discrimination of tsunami deposits from other sources such as storms is still lacking establishing these criteria is essential if we are to improve our understanding of tsunami frequency over geological timescales by this means we will improve the identification of tsunami hazard and improve risk assessment this special issue focuses on tsunami deposits identifying their characteristics and their discriminating features from other sources such as storms although perhaps not as common as other event sediments it is considered likely that a reappraisal of the geological record is required to place them in their representative context

desert aeolian origin of late cenozoic regolith in arid and semi arid southwestern australia abstract using a sedimentary geology approach the late cenozoic regolith of southwestern australia is interpreted as basement saprock and saprolite unconformably overlain by sequences of continental sedimentary deposits the sedimentary deposits which overlie saprock and saprolite are allochthonous variously altered and mainly partly to wholly desert aeolian sediments they include aeolian and fluvial sandy clayrock facies e g deposits which resemble the pallid and mottled zones of weathered precambrian bedrock of the traditional laterite profile altered aeolian sand and sandy dust facies e g hardpan lower parts of duplex soils red sandy silt claystone and calcrete valley fills altered sandy duststones e g bauxite laterite and ferricrete of the traditional laterite profile and bioturbated aeolian sand sheets e g sandplain soils lateritic sandplains of the traditional laterite profile and upper parts of duplex soils the allochthonous and desert aeolian views proposed here differ fundamentally from the traditional residual colluvial and erosional views consequently there is a need for both traditional and alternative views to be critically appraised from the perspective of sedimentary geology

lateritization and bauxitization events laterites and bauxites are produced in tropical soils by weathering which enriches iron of laterites and alu mina of bauxites as well as trace elements such as nickel gold phosphorus and niobium to ore grade la terites and bauxites can be redeposited into sedimentary sequences and remain as ores if not transported far and diluted with other materials the age of redeposited laterites and bauxites and of bauxitic and lateritic pa leosols can be established from the geologic age of overlying rocks an approach especially effective in pale osols within sequences of isotopically datable volcanic rocks lateritic profiles can also be dated by paleomag netic inclination in special cases in which land masses such as in australia and india drifted long distances northward during cenozoic time in addition cryptomelane and other k mn oxides can be dated by k ar and 40ar 39ar techniques to obtain multiple ages from different crystals in a single relict paleosol compilation of new and more accurate laterite and bauxite ages reveals unusually widespread and intense laterite and bauxite formation during events of less than 100 k y duration at 2 12 16 35 48 55 65 and 100 ma such events can also be inferred at times older than 100 ma from paleolatitudinal distribution of laterites and bauxites but these are poorly sampled laterite and bauxite peaks were coeval with times of global high warmth and pre cipitation elevated atmospheric carbon dioxide oceanic anoxia exceptional fossil preservation and mass ex tinction these co2 greenhouse events and attendant titration of carbonic acid with soils are interpreted as transient fluctuations in the atmosphere produced by meteorite impact flood basalt volcanism and methane outbursts concentration of bauxite and laterite resources in particular stratigraphic horizons formed during greenhouse crises suggests the usefulness of an event stratigraphic approach to exploration and exploitation of these and related ores

geomorphology stratigraphy and thermoluminescence dating of the lunette dune at lake victoria western new south wales abstract lake victoria 13 km long and 10 km wide is the largest lunette lake attached to the murray river in southeastern australia the lake occupies the western part of a larger basin at least twice the size of the present lake the larger basin has been incised nearly 30 m into the regional sand plain surface and into the early middle pleistocene blanchetown clay within the larger basin east of the lunette of the present lake victoria various landforms have developed including alluvial terraces salt pans small dry basins and multiple small lunettes among these an arcshaped sand ridge possibly an old lunette was dated by tl as 82 ka the present lunette of lake victoria is up to 40 m high and consists of 3 units nulla nulla sand 30 m thick talgarry sand up to 10 m thick and the reworked dunedin park sand the nulla nulla sand consists dominantly of pure medium to fine grained sand sequences with a few red palaeosols indicating long standing high lake levels with a few lunette stable intervals deposition of the nulla nulla sand ended around 20 ka starting at least 40 ka ago and probably much earlier the talgarry sand overlying a prominent red palaeosol on top of the nulla nulla sand consists of pure sand horizons interbedded with at least 3 gypseous clayey silt layers the gypseous sediments indicate a major change of hydrologic conditions in the lake basin fluctuation of lake levels and periodically high salinity the talgarry sand was deposited from 17 to 10 ka as dated by tl and previous 14c dates after 10 ka lunette accretion stopped possibly the result of incision of the murray river channel reducing the water and sediment input to the basin however erosion and deflation of the lunette formed an apron of sediment on the lower lake facing slope and sand transport to the lee side long slope leaving islands of old sediment along the lunette crest zone

architecture of the deep critical zone in the rio icacos watershed luquillo critical zone observatory puerto rico inferred from drilling and ground penetrating radar gpr

the norwest bend formation implications for the evolution of neogene drainage in southeastern australia abstract strontium isotope data indicate that sediments of the norwest bend formation were deposited within a large estuarine system during the latest miocene to early pliocene probably 5 ma the norwest bend formation is divisible into two members a lower sand dominated member and an upper oyster coquina member these two units are separated by an irregular erosion surface that has no correlative within the adjacent loxton parilla sands tectonism in the western murray basin adjacent to the adelaide foldbelt has exerted a considerable control over the formation of these estuarine sediments the lower norwest bend formation occupies a paleodrainage system that was restricted to a region west of the hamley fault and was presumably incised following uplift of this western block flooding of this paleodrainage system produced the lower norwest bend estuarine system later tectonism on the hamley fault resulted in the formation of the erosion surface within the norwest bend formation we suggest that the norwest bend estuarine system owes its existence to marginal tectonism associated with the young uplift of the mt lofty flinders ranges the paleodrainage system incised prior to deposition of the norwest bend formation differs markedly in geometry from the present murray river gorge system this suggests that the modern murray river system developed after deposition of the late miocene pliocene norwest bend formation