evolution of the eastern volcanic ridge of the canary islands based on new kar data the results of 64 new k ar age determinations together with 32 previously published ages show that after a period of erosion of the basal complex miocene volcanic activity started around 20 ma in fuerteventura and 15 ma in lanzarote forming a tabular succession of basaltic lavas and pyroclastics with a few salic dykes and plugs this series includes five separate volcanic edifices each one with its own eruptive history in fuerteventura several miocene eruptive cycles have been identified in the central edifice one around 20 17 ma followed by two others centred around 15 and 13 ma in the southern edifice the maximum of activity took place around 16 14 ma whereas in the northern one the main activity occurred between 14 and 12 ma in lanzarote a first cycle of activity took place in the southern edifice between 15 5 and 14 1 ma followed by another between 13 6 and 12 3 ma in the northern edifice three pulses occurred 10 2 8 3 6 6 5 3 and 3 9 3 8 ma an important temporal gap greater in fuerteventura than in lanzarote separates series i from the plio quaternary series ii iii and iv formed by multi vent basaltic emissions in fuerteventura the following eruptive cycles have been identified 5 2 9 2 4 1 8 1 7 0 8 0 4 and 0 1 ma in lanzarote the activity was fairly continuous from 2 7 ma to historic times with a maximum in the lower pleistocene eruptive rates in the series i edifices were on the average 0 1 0 01 km3 ka comparable but slightly smaller than in similar edifices in tenerife and la gomera but much lower than in gran canaria average post miocene eruptive rates were about 0 013 0 027 km3 ka in lanzarote and 0 003 0 007 km3 ka in fuerteventura all these volcanic edifices show a similar general sequence fissural eruptions erosion multi vent volcanism repeated at different periods in different parts of the eastern islands of the canaries the model of growth of the series i edifices is comparable to those in tenerife and la gomera long periods of activity sometimes greater than 6 m y with pulses separated by gaps however salic and intermediate differentiates frequent in tenerife and la gomera are very scarce in these islands the fuerteventura lanzarote ridge shows a decrease in volcanic activity with time and also a certain ssw nne polarity in the temporal development of volcanism

iconic imagery pleistocene rock art development across northern australia there is general agreement that the peopling of sahul was achieved sometime before 45 000 years ago with most parts of the continent colonised by 30 000 rock art both engraved and painted is present in all areas where these early people left their mark did this artistic endeavour come with these people or was this an expression of being in sahul certainly there are aspects like the cupules and hand stencils which have parallels outside the continent however there are many features that suggest separate artistic traditions and conventions that were present and have continued since these early times spread over an area greater than one million sq km 386 000 sq miles stretching in an arc over 2 000 km from the pilbara coast through the kimberley and into arnhem land is a vast body of rock art that demonstrates there to be differentiation in the symbolic structuring of people s lives relatively early after colonisation this supports the notion that regionalisation within sahul is not simply a holocene expression

reappraisal of the extinction of canariomys bravoi the giant rat from tenerife canary islands abstract all the quaternary endemic rodents of the canary islands are currently extinct the lava mouse malpaisomys insularis inhabited the easternmost islands whereas the giant rats canariomys bravoi and canariomys tamarani lived in the central islands of tenerife and gran canaria respectively bones of c bravoi have appeared in archaeological sites together with shellfish and butchery remains traditionally they have been considered as an evidence of the sporadic consumption of c bravoi by the aboriginal people in some instances as recently as the time of the first european contact 14th century ad accordingly the extinction of c bravoi has been linked to the european colonization of tenerife the plausibility of this extinction date has been explored through new radiocarbon dates obtained on selected c bravoi bones and through a reappraisal of the published dates our analysis allowed us to establish an earlier last documented occurrence age for c bravoi prior to the third century cal bc much earlier than previously assumed the analysis of formerly published 14 c dates of archaeological remains from tenerife shows that samples with confidence intervals 95 54 that are older or overlap with the last documented record of c bravoi were performed on materials with large sources of error such as wood charcoal or bulk ash sediments conversely the new radiocarbon dates and analyses presented herein are in agreement with the occurrence of an earlier rapid extinction linked to the first human presence on the island

small vertebrate taphonomy of la cueva del llano a volcanic cave on fuerteventura canary islands spain palaeoecological implications abstract cueva del llano is a volcanic tube of pleistocene age on fuerteventura island a strand of it ramal nuevo contains a complex sedimentary infill which has been divided into three sedimentary units and contains at least eight fossiliferous levels of holocene age the taphonomic analysis of small vertebrates found in the sediments revealed a scatological origin for the vertebrate assemblage and that the barn owl tyto alba is the main agent responsible for this concentration of bone remains furthermore the taphonomic analysis allows to reconstruct the changes in the palaeodiet of barn owls during the holocene of fuerteventura canary islands and infer the alterations produced in the vertebrate comunity during that time in the upper units of the sedimentary infill the appearance of the house mouse mus musculus is observed this immigration is correlated that is associated to a decrease of the lava mouse malpaisomys insularis proportions in the fossil assemblage also the study of small vertebrate accumulation in ramal nuevo shows that volcanic tubes can be referred to as very useful concentration trap for taphonomic studies

on playfair s law of accordant junctions geomorphologists since playfair have apparently accepted that fluvial confluences will be morphologically accordant in distinction to the hanging junctions of glaciated troughs a view reinforced by gilbert s law of declivities the issue has been largely ignored despite field instances of discordant fluvial junctions and widespread engineering practice which favours discordant confluences in non erodible materials six categories of fluvial junctions are defined accordant hanging discordant barred impeded disrupted and disturbed the study focuses principally on the first two classes and defines discordance purely morphologically in terms of relative depth of incision of the confluent thalwegs likely controls of accordance discordance are identified as flow magnitudes synchroneity of flow regimes channel boundary materials and debris calibre field investigations in malawi france west malaysia and new zealand in small 100 km2 basins on a variety of rock types are described barred junctions are relatively rare but complex in character a high proportion of confluences are distinctly discordant and there is a general continuum from accordant cases tectonic control is improbable and the principal cause identified is the degree of difference in channel forming discharges estimated by stream magnitude and channel area some evidence for lithologic control is also apparent it appears that many confluences behave as if the tributary junction is non erodible and not in the fashion predicted by the law of declivities it is argued that the observed relation is a necessary result of the general down stream changes in hydraulic geometry limited comparison with glacial trough confluences reveals a difference in degree but not in nature although the relationship between discordance and channel size is affected by cross section geometry a 10 fold difference in the cross sectional areas of channels meeting at a junction produces on average a 2 4 fold difference in mean channel depths for fluvial cases and a 4 fold difference for glacial troughs the role of varying flow regimes seems to require attention nevertheless it is maintained that playfair s law is a misleading description of the morphology of fluvial junctions which behaves fundamentally in the same fashion as glacial troughs

a reappraisal of the stratigraphy of cueva del llano fuerteventura and the chronology of the introduction of the house mouse mus musculus into the canary islands abstract major ecological changes related to anthropogenic activities begin on islands with initial human settlement key factors to understanding insular holocene ecological changes are the arrival dates of both humans and alien species to the islands in this context finely stratified fossil sites are powerful tools to study the chronology and causes of these changes previous work based on conventional 14c ages of land snails coming from the finely stratified site cueva del llano at fuerteventura canary islands eastern atlantic ocean indicates that one of the major ecological changes that took place in this archipelago the arrival of house mouse mus musculus occurred around 7000 yrs ago thus before the first arrival of humans to the islands to extend these studies we obtained 14c ages by accelerator mass spectrometer ams directly on bone collagen from selected bones of rodents lava mouse malpaisomys insularis and house mouse from seven sites cueva del llano cueva de villaverde and malpais de la arena i ii fuerteventura el bebedero and jameo de la puerta falsa lanzarote and barranco de la baranda la palma the new ages derived from the upper levels of cueva del llano cll 9 1 9 2 indicate a very young age for these materials between 1667 1949 and 1261 1391 cal ad these results support a more recent and very different chronology for the holocene ecological changes that occurred on these islands compared to previous studies explanations for the stratigraphically anomalous age shown in previous papers are put forward on the other hand the available 14c ages indicate that the house mouse arrived on the eastern canary islands some time between 756 cal bc 313 cal ad and probably from there spread to the other islands before european contact

high resolution chronologies for loess comparing ams 14c and optical dating results the nuxloch loess section in south west germany is famous in central europe for its thick deposits from the last glacial maximum it has therefore been intensively studied during the past few years and offers an excellent opportunity to compare the performance of different dating techniques covering the period 15 45 ka here we present results fromoptical and ams 14 c dating the silt sized polymineral fraction of the clastic sediments and a multiple aliquot approach was used for ir osl dating 14 c dating was carried out on organic macro remnants and humin fractions extracted fromthe sedim ents with the exception of samples taken from the uppermost 1 5 m of the section ir osl and calibrated 14 c ams ages are consistent over the entire period the inconsistencies in the upper meters are thought to be due to disturbances during soil formation in the holocene the good agreement obtained on the remaining sequence demonstrates the high accuracy of both methods when studying loess sections for the ir osl ages no significant age underestimations are obvious the results clearly document that accurate chronologies can be developed for such continental sedimentary sequences this gives access to archives that can now be studied with a high temporal resolution and allows the establishment of new paleoclimatic proxies for the study of terrestrial responses to past climatic changes r 2003 elsevier science ltd all rights reserved

multidisciplinary approaches to australian island pasts late pleistocene to historical perspectives on australian island use in this review volume we bring together researchers and institutions involved in australian island research to provide a contemporary synthesis and benchmark on archaeological and palaeoenvironmental research of australian island environments the last major overview of australian islands archaeological research appeared 16 years ago in the volume australian coastal archaeology hall and mcniven 1999 at that time the main geographical areas of dynamic islands research in australia were northwest western australia and central and southeast queensland since 1999 torres strait has developed as the most dynamic region of islands research in australia and this new volume showcases the range of recent research from torres strait and the adjacent region of southern papua new guinea all five inqua commissions coastal and marine processes humans and the biosphere palaeoclimates stratigraphy and chronology terrestrial processes deposits and history are represented in the papers in the volume key environmental themes explored through the volume are geoarchaeology taphonomy impacts of sea level rise and climate change chronology of island formation and colonisation anthropogenic environmental modifications island terrestrial and marine resource management and intra and inter island occupation mobility and exchange relationships key socio cultural themes explored include ritual and ceremonial sites mortuary practices canoe voyaging and responses to colonial impact site types discussed include shell deposits cultural and natural villages long houses gardens rock art ritual shrines artificial reefs and ceremonial stone arrangements the contributions represent diverse multidisciplinary approaches adopting coordinated methodologies to the task of understanding the diversity of human use and modification of islands in the australian context culturally and chronologically the volume surveys the depth and breadth of australian island societies including studies of late pleistocene island use in northwest australia late holocene deltaic island societies of papuan lowland rainforests early to mid holocene tropical island use of torres strait and the great barrier reef and holocene selective occupation and abandonment of bass strait and other southern ocean islands the volume s geographic coverage is thus broadscale spread from the hot and humid tropical north to the cold temperate waters of the southern ocean uniquely the papers in this volume reveal the diversity and complexity of cultural practices e g subsistence mobility technology socio religious institutions cosmology resource manipulation and management and historical contingencies that structure and mediate long term human use engagement and modification of islands

correspondence on erosion rates and weathering history of rock surfaces associated with aboriginal rock art engravings petroglyphs on burrup peninsula western australia from cosmogenic nuclide measurements by brad pillans and keith fifield quaternary science reviews 69 98 106

the potential for discovery of new submerged archaeological sites near the dampier archipelago western australia abstract the islands of the dampier archipelago preserve a probable 30 000 year archaeological record that reflects the change from a continental to an island environment following post glacial sea level rise the geomorphological history of the dampier archipelago region in combination with preliminary hydrodynamic modelling of past tidal regimes provides the basis for a new model of how the shelf landscape may have developed between the last glacial maximum c 20 ka bp through the holocene marine transgression and up to the present day using first order geomorphological principles an assessment is made of the key late pleistocene and holocene sediment bodies that may preserve archaeological deposits we show that archaeology is most likely to be present in deposits associated with the early phases of inundation of the dampier archipelago dating from around 9 7 ka bp at this time relative sea levels were around 30 m to 15 m which was when coastal configuration was complex and the variety and scale of intertidal and shallow sub tidal environments wide in contrast we anticipate that coastal archaeology older than 12 ka bp when the post glacial sea levels were below 50 m will have been exposed to a phase of faster tidal currents on the continental shelf and hence eroded or poorly preserved our study aims to improve prospection for and later management of the as yet unknown submerged elements of west australia s rich archaeological heritage

the pilbara coast a riverine coastal plain in a tropical arid setting northwestern australia abstract the unifying feature of the pilbara coast of northwestern australia is that it is a sedimentary repository for a range of rivers that drains a high relief precambrian rocky hinterland and discharges sediments along a coastal plain which fronts a wave dominated environment in a tropical arid climate the combination of fluvial and shoreline accretion processes coastal cementation coastal erosion and ancestral landform architecture such as residual pleistocene limestone ridges and large outcrops of precambrian bedrock has produced a complex coastal system during the quaternary as a result the coast is dominated by active deltas beach dune shores inactive eroding parts of deltas and their barriers limestone barrier coasts bays associated with eroded limestone barriers and archipelago ria coasts quaternary sediments throughout the area while varied in their distribution and history at the smaller scales exhibit a recurring pattern of lithotopes and lithologies in the region there are three main quaternary suites pleistocene red siliciclastic sediments alluvium deltaic sediments and aeolian sand that form an inland zone pleistocene limestones that form local barriers and a holocene system within which are the sedimentary suites of deltas beach dunes tidal flats and tidal embayments

post glacial sea level changes around the australian margin a review abstract it has been known since rhodes fairbridge s first attempt to establish a global pattern of holocene sea level change by combining evidence from western australia and from sites in the northern hemisphere that the details of sea level history since the last glacial maximum vary considerably across the globe the australian region is relatively stable tectonically and is situated in the far field of former ice sheets it therefore preserves important records of post glacial sea levels that are less complicated by neotectonics or glacio isostatic adjustments accordingly the relative sea level record of this region is dominantly one of glacio eustatic ice equivalent sea level changes the broader australasian region has provided critical information on the nature of post glacial sea level including the termination of the last glacial maximum when sea level was approximately 125 m lower than present around 21 000 19 000 years bp and insights into meltwater pulse 1a between 14 600 and 14 300 cal yr bp although most parts of the australian continent reveals a high degree of tectonic stability research conducted since the 1970s has shown that the timing and elevation of a holocene highstand varies systematically around its margin this is attributed primarily to variations in the timing of the response of the ocean basins and shallow continental shelves to the increased ocean volumes following ice melt including a process known as ocean siphoning i e glacio hydro isostatic adjustment processes several seminal studies in the early 1980s produced important data sets from the australasian region that have provided a solid foundation for more recent palaeo sea level research this review revisits these key studies emphasising their continuing influence on quaternary research and incorporates relatively recent investigations to interpret the nature of post glacial sea level change around australia these include a synthesis of research from the northern territory queensland new south wales south australia and western australia a focus of these more recent studies has been the re examination of 1 the accuracy and reliability of different proxy sea level indicators 2 the rate and nature of post glacial sea level rise 3 the evidence for timing elevation and duration of mid holocene highstands and 4 the notion of mid to late holocene sea level oscillations and their basis based on this synthesis of previous research it is clear that estimates of past sea surface elevation are a function of eustatic factors as well as morphodynamics of individual sites the wide variety of proxy sea level indicators used their wide geographical range and their indicative meaning some progress has been made in understanding the variability of the accuracy of proxy indicators in relation to their contemporary sea level the inter comparison of the variety of dating techniques used and the nuances of calibration of radiocarbon ages to sidereal years these issues need to be thoroughly understood before proxy sea level indicators can be incorporated into credible reconstructions of relative sea level change at individual locations many of the issues which challenged sea level researchers in the latter part of the twentieth century remain contentious today divergent opinions remain about 1 exactly when sea level attained present levels following the most recent post glacial marine transgression pmt 2 the elevation that sea level reached during the holocene sea level highstand 3 whether sea level fell smoothly from a metre or more above its present level following the pmt 4 whether sea level remained at these highstand levels for a considerable period before falling to its present position or 5 whether it underwent a series of moderate oscillations during the holocene highstand

three dimensional structure of flow at a confluence of river channels with discordant beds this paper presents three dimensional data of the mean and turbulent structure of flow collected at a natural confluence of rivers with discordant beds to 1 describe the three dimensional flow field of a natural junction of channels 2 assess the role of changes in bed morphology occurring during transport effective events on the structure of flow at a confluence and 3 examine how the three dimensional structure of flow varies with changes in the ratio of momentum flux between the two confluent streams three dimensional measurements of velocity were reconstructed from the measurements obtained with an array of four two component electromagnetic current meters six detailed velocity profiles were taken at five cross sections in a wide range of flow conditions the mean field of flow is characterised by 1 the acceleration of flow in the downstream portion of the post confluence channel but by lower velocities upstream in the mixing layer area 2 a stagnation zone at the apex of the junction 3 a zone of flow deviation and strong fluid upwelling close to the avalanche face and at the margin of the tributary mouth bar and 4 reduced velocities over the depositional bar at the downstream junction corner the position and extent of these zones vary with changes in the ratio of momentum flux very high intensity of turbulence peaks up to 50 and turbulent kinetic energy were observed in the mixing layer region distortion of the mixing layer characteristic of flow where bed discordance is present between the two tributary channels was evident from mean and turbulent flow data this field study suggests that the effects of bed discordance on flow sediment transport and the resultant bed morphology must be incorporated into conceptual and numeric models of these sites of complex flow

glacial and deglacial climatic patterns in australia and surrounding regions from 35 000 to 10 000 years ago reconstructed from terrestrial and near shore proxy data abstract this study forms part of a wider investigation of late quaternary environments in the southern hemisphere we here review the terrestrial and near shore proxy data from australia indonesia papua new guinea png new zealand and surrounding oceans during 35 10 ka an interval spanning the lead up to the last glacial maximum lgm the lgm proper 21 2 ka and the ensuing deglaciation sites selected for detailed discussion have a continuous or near continuous sedimentary record for this time interval a stratigraphically consistent chronology and one or more sources of proxy climatic data tropical australia indonesia and png had lgm mean annual temperatures 3 7 c below present values and summer precipitation reduced by at least 30 consistent with a weaker summer monsoon and a northward displacement of the intertropical convergence zone the summer monsoon was re established in northwest australia by 14 ka precipitation in northeast australia was reduced to less than 50 of present values until warmer and wetter conditions resumed at 17 16 ka followed by a second warmer wetter phase at 15 14 ka lgm temperatures were up to 8 c lower than today in mainland southeast australia and up to 4 c cooler in tasmania winter rainfall was much reduced throughout much of southern australia although periodic extreme flood events are evident in the fluvial record glacial advances in southeast australia are dated to 32 2 5 19 1 1 6 and 16 8 1 4 ka with periglacial activity concentrated towards 23 16 ka deglaciation was rapid in the snowy mountains which were ice free by 15 8 ka minimum effective precipitation in southern australia was from 14 to 12 ka in new zealand the glacial advances date to 28 21 5 and 19 ka with the onset of major cooling at 28 ka or well before the lgm there is no convincing evidence for a younger dryas cooling event in or around new zealand but there are signs of the antarctic cold reversal in and around new zealand and off southern australia there remain unresolved discrepancies between the climates inferred from pollen and those inferred from the beetle and chironomid fauna at a number of new zealand sites one explanation may be that pollen provides a generalised regional climatic signal in contrast to the finer local resolution offered by beetles and chironomids sea surface temperatures ssts were up to 5 c cooler during the lgm with rapid warming after 20 ka to attain present values by 15 ka the increase in summer monsoonal precipitation at or before 15 ka reflects higher insolation warmer ssts and steeper thermal gradients between land and sea the postglacial increase in winter rainfall in southern australia is probably related to the southward displacement of the westerlies as ssts around antarctica became warmer and the winter pack ice and antarctic convergence zone retreated to the south

stratigraphy chronology and paleoenvironmental reconstruction of the quaternary sedimentary infilling of a volcanic tube in fuerteventura canary islands abstract la cueva del llano is a volcanic tube of pleistocene age on fuerteventura island in the canary islands part of it is infilled with sediments of external origin these deposits are exceptional in stratigraphic complexity and thickness compared with other known tube infillings and they comprise nine stratigraphic units deposited in five phases in phase i which has not been dated sedimentation of cinder from a nearby cone occurred phase ii began ca 16 830 900 14 c yr b p whereas phase iv dates to 9280 370 14 c yr b p the interpretation of sedimentary features shows that phases iii and v correspond to a dry climate similar to the present one whereas the climate was much wetter during phases ii and iv this paleoclimatic sequence agrees with those suggested by the study of deposits formed in other sedimentary environments not only in fuerteventura but on other islands of the canary group and the sud maroc region

i must go down to the seas again or what happens when the sea comes to you murujuga rock art as an environmental indicator for australia s north west the dampier archipelago properly known as murujuga is a rich rock art province in north western australia which documents an arid maritime cultural landscape but this archipelago of 42 islands has only existed since the mid holocene when people started to engrave art here the granophyre bedrock was part of an inland range more than 160 km from the coast the pilbara archaeological record demonstrates human responses through over forty thousand years of environmental change this paper discusses how rock art across murujuga can give insights to changing dynamics of people in place as well as depicting major environmental change a predictive model is developed to assist in understanding the social changes which have been wrought by sea level rise and consequential environmental changes 2014 elsevier ltd and inqua all rights reserved

sediment transport and bed morphology at river channel confluences river channel confluences form important morphological elements of every river system being points at which rapid changes in flow sediment discharge and hydraulic geometry must be accommodated this article presents results of a quantitative investigation of sediment transport at channel confluences accomplished through both scaled laboratory flume simulation and complementary monitoring of a natural channel confluence bed morphology at channel confluences is characterized by three distinct elements avalanche faces at the mouth of each confluent channel a deep central scour and a bar within the separation zone formed at the downstream junction corner these elements are controlled predominantly by the confluence angle and the ratio of discharges between the tributary and mainstream channels as confluence angle and discharge ratio increase the sediment contributions from the confluent channels are progressively segregated in their paths through the junction with sediment being transported around rather than through the centre of the confluence this segregation of sediment loads is accompanied by the retreat of the main channel avalanche face from the confluence an increase in the scour depth a change in the orientation of the scour and an increase in the size of the separation zone bar field measurements closely replicate the flume simulation a model of sediment transport and bed morphology links these features to the fluid dynamics of these sites an understanding of confluence dynamics is important not only in considerations of channel morphology and design criteria but must form the basis for the interpretation of confluence sediments in the ancient record

late pleistocene and early holocene exploitation of estuarine communities in northwestern australia this contribution synthesizes archaeological studies of human economies from the barrow montebello islands and uses the area s archaeological record to determine the effects of late pleistocene and early holocene sea level rise on regional coastlines at the height of the last glacial maximum lgm australia s north western coast extended much further west than the present day shoreline during subsequent sea level rise the gently prograding continental shelf was inundated and with it nearly all archaeological evidence for coastal occupation the barrow and montebello islands are one of the few exceptions as they corresponded to inland hinterland ranges during the lgm with the coastline lying some 50 km to their west evidence from all late pleistocene and holocene occupation phases of the barrow montebello islands demonstrate that foragers continued to visit the coast and engage in the exploitation of both terrestrial and marine environments during the late pleistocene when the shoreline was 10 15 km away coastal exploitation is seen through the presence of transportable estuarine and rocky shore gastropods by the early holocene when sea levels were within close proximity of the sites there is a marked increase in marine fauna including reef fish estuarine and reef shellfish crustaceans and estuarine crocodile together this suggests that the nearby muddy procumbent coastlines were productive as well as an important component of coastal and hinterland economies

erosion rates and weathering history of rock surfaces associated with aboriginal rock art engravings petroglyphs on burrup peninsula western australia from cosmogenic nuclide measurements abstract the burrup peninsula and surrounding dampier archipelago in western australia contain the world s largest known gallery of rock art engravings petroglyphs estimated to number up to 1 million images the peninsula is also the site of major industrial development and there are concerns that industrial emissions may adversely affect the stability and longevity of the rock art we have studied the natural processes and rates of weathering and erosion including the effects of fire that affect the stability of rock surfaces and hence the longevity of the rock art using cosmogenic nuclides the concentration of 10 be in quartz yields erosion rates in the range 0 15 0 48 mm 1000 years on horizontal rock surfaces and 0 34 2 30 mm 1000 years on vertical rock faces the former largely caused by mm scale surface flaking are amongst the lowest erosion rates measured by cosmogenic nuclides anywhere in the world the latter are inferred to represent a combination of mm scale flaking and very rare centimetre to metre scale block falls controlled by failure along joint planes such low erosion rates result from a combination of resistant rocks low relief and low rainfall favouring long term preservation of the petroglyphs long enough to encompass the known period of human settlement in australia

effect of the sediment discharge on the equilibrium bed morphology of movable bed open channel confluences abstract the objective of this study was to characterize the influence of sediment discharge on the morphology of movable bed asymmetric open channel confluences for this purpose fifteen experiments were performed on rough turbulent flows through an experimental confluence by running a single combination of confluent discharges and using a single bed material with three different sediment loads in the main channel combined with five different sediment loads in the tributary channel the experiments were run until equilibrium was reached physical interpretations of the influence of the sediment amount fed into the system on the most important variables and parameters of the confluent flows and confluence morphology were provided morphological variables considered included the height of the tributary mouth bar the depth of the scour hole located in the vicinity of the tributary mouth the deviation angle of the tributary flow and the dimensions of the bank attached bar the hydrodynamic parameters of the confluent flows studied included the unit momentum flux the unit stream power or the ratio of confluent unit momentum fluxes the crucial importance of the sediment load entering the system was highlighted since it was documented that i both channels upstream of the confluence adapted their respective bed slope flow depth and average flow velocity to respond to the independent sand amounts entering the system ii the characteristic dimensions and shape of the most important confluence features changed consistently with the imposed changes on the sediment discharge ratio and concentration iii for a given water discharge ratio the unit momentum flux ratio depended on the sediment amounts flowing through the confluence instead of being an independent parameter