cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

inbank and overbank velocity conditions in an arid zone anastomosing river relative to those at sub bankfull flow hydraulic conditions at overbank flow whether in the channel or on the floodplain are poorly understood here velocity conditions are analysed over an unusually wide range of flows in the arid zone river of cooper creek with its complex system of anastomosing channels and large fluctuations in floodplain width at a station hydraulic geometry relationships reveal sharp discontinuities in velocity at the inbank overbank transition the nature of the discontinuity varying with the degree of flow confinement and the level of channel floodplain interaction however despite inter sectional differences velocities remain modest throughout the flow range in this low gradient river and the large increases in at a station discharge are principally accommodated by changes in cross sectional area velocity distribution plots suggest that within channel conditions during overbank flow are characterized by a central band of high velocity which penetrates far toward the bed helping to maintain already deep cross sections floodplain resistance along cooper creek is concentrated at channel bank tops where vegetation density is highest and the subsequent flow retardation is transmitted across the surface of the channels over distances as large as 50 70 m the rough floodplain surface affects flood wave transmission producing significant decreases in wave speeds downstream the character of the wave speed discharge relationship also changes longitudinally from log linear in the upper reaches to nonlinear where the floodplain broadens appreciably the nonlinear form is similar in several respects to relationships proposed for more humid rivers with flood wave speed reaching an intermediate maximum at about four fifths bankfull discharge before decreasing to a minimum at approximately q2 33 it does not regain the value at the intermediate maximum until the 10 year flood by which time floodplain depths have become relatively large and broad floodways more active copyright 2002 john wiley sons ltd

preservation potential for late quaternary river alluvium valley sequences of late quaternary alluvial units reflect alluvial preservation as well as alluvial production factors effects of lateral channel migration incision aggradation and channel stability on preservation potential are explored and then considered in the light of 14 available data sets cartographically dated and model data based on lateral channel migration well mapped and dated late quaternary valley unit surveys and composite age frequency plots for dated alluvial units and flood sediments despite much expectable variation between sites and the complex effects of river activity combinations a common characteristic of the data sets examined is the significance of preservation factors lateral migration tends to eliminate older units as it creates new alluvial deposits whereas incision may lead to the preferential preservation of older units beyond the incision slot aggradational environments are likely to preserve more complete records although simultaneous lateral migration may eliminate possibly repeatedly the upper parts of alluvial units the common pattern of inset and incised streams within pleistocene and early holocene fills or bedrock gives finite extent to later units within narrowing valleys so that development of new valley floor units is necessarily at the expense of reprocessing earlier ones floods associated with both slack water deposits and berms are also responsible for the removal of accessible earlier materials thus limiting the preserved record of earlier events in light of these censoring effects of river activities the sequence of preserved late quaternary units within uk sequences is reconsidered it is concluded that preservation potential factors have led to spatial and temporal bias in the alluvial record and that both here and elsewhere preservation potential needs to be considered systematically alongside variable sedimentation resulting from allogenic environmental factors when interpreting the alluvial archive copyright 2003 john wiley sons ltd journal of quaternary science

real and apparent changes in sediment deposition rates through time 1 field measurements show that estimated sediment deposition rate decreases as a power law function of the measurement interval this apparent decrease in sediment deposition has been attributed to completeness of the sedimentary record the effect arises because of incorporation of longer hiatuses in deposition as averaging time is increased we demonstrate that a heavy tailed distribution of periods of nondeposition hiatuses produces this phenomenon and that observed accumulation rate decreases as t 1 over multiple orders of magnitude where 0 1 is the parameter describing the tail of the distribution of quiescent period length by using continuous time random walks and limit theory we can estimate the actual average deposition rate from observations of the surface location over time if geologic and geometric constraints place an upper limit on the length of hiatuses then average accumulation rates approach a constant value at very long times our model suggests an alternative explanation for the apparent increase in global sediment accumulation rates over the last 5 million years

late quaternary aeolian and fluvial interactions on the cooper creek fan and the association between linear and source bordering dunes strzelecki desert australia abstract the innamincka dome and associated low gradient fan in the strzelecki desert is the product of cenozoic crustal warping that has aided formation of an extensive array of palaeochannels source bordering transverse dunes and superimposed linear dunes these dunes have impeded the course of cooper creek and provided a repository of evidence for quaternary climate change as well as the interactive processes between transverse and linear dune formation at turra gidgealpa and sites nearby are extensive fluvial and aeolian sand bodies that date from marine isotope stages mis 8 3 and the last glacial maximum lgm and are now surrounded or buried by overbank mud the sandy alluvium was deposited on the downstream slope of the dome by large channels transporting abundant bedload subsequently blown northward to form transverse dunes from what were probably seasonally exposed bars in a palaeo cooper system thermoluminescence tl and optically stimulated luminescence osl ages demonstrate that the base of the dune complex is at least mis 7 in age 250 ka but that it has been subsequently reworked by wind with additional sand blown from the river source bordering dunes formed during a period of enhanced river flow and sand supply from 120 to 100 ka with another short episode of the same at 85 80 ka and from 68 to 53 the lgm was associated with enhanced flows and the supply of dune sediment from 28 to 18 ka pronounced river flow and dune activity occurred in the early to mid holocene but there is no evidence of dunes being supplied from cooper creek since the lgm the dunes forming the oldest basal sand units appear to be largely transverse in form and are aligned roughly parallel to adjacent east west trending palaeochannels linear dunes have formed from and over these and yield basal ages ranging from mis 5 or mis 4 but continuing to accrete and rework through to the holocene the study results in one of the few detailed chronological investigations of the interaction between transverse and linear dunes it is apparent that long distance sand transport has played no significant role in dune formation here for the linear dunes show no significant downwind decline in ages linear dunes appear to have accreted vertically from underlying transverse dunes a wind rift vertical accretion model with only minor lengthwise extension is the dominant mode of linear dune formation in this section of the strzelecki desert the bulk of dune sediment being sourced from adjacent swales since the lgm

anabranching rivers their cause character and classification anabranching rivers consist of multiple channels separated by vegetated semi permanent alluvial islands excised from existing floodplain or formed by within channel or deltaic accretion these rivers occupy a wide range of environments from low to high energy however their existence has never been adequately explained they occur concurrently with other types of channel pattern although specific requirements include a flood dominated flow regime and banks that are resistant to erosion with some systems characterized by mechanisms to block or constrict channels thereby triggering avulsion the fundamental advantage of an anabranching river is that by constructing a semi permanent system of multiple channels it can concentrate stream flow and maximize bed sediment transport work per unit area of the bed under conditions where there is little or no opportunity to increase gradient on the basis of stream energy sediment size and morphological characteristics six types of anabranching river are recognized types 1 3 are lower energy and types 4 6 are higher energy systems type 1 are cohesive sediment rivers commonly termed anastomosing with low w d ratio channels that exhibit little or no lateral migration they are divisible into three subtypes based on vegetative and sedimentary environment type 2 are sand dominated island forming rivers and type 3 are mixed load laterally active meandering rivers type 4 are sand dominated ridge forming rivers characterized by long parallel channel dividing ridges type 5 are gravel dominated laterally active systems that interface between meandering and braiding in mountainous regions type 6 are gravel dominated stable systems that occur as non migrating channels in small relatively steep basins anabranching rivers represent a relatively uncommon but widespread and distinctive group that because of particular sedimentary energy gradient and other hydraulic conditions operate most effectively as a system of multiple channels separated by vegetated floodplain islands or alluvial ridges

eroding australia rates and processes from bega valley to arnhem land we report erosion rates determined from in situ produced cosmogenic 10 be across a spectrum of australian climatic zones from the soil mantled se australian escarpment through semi arid bedrock ranges of southern and central australia to soil mantled ridges at a monsoonal tropical site near the arnhem escarpment climate has a major effect on the balance between erosion and transport and also on erosion rate the highest rates averaging 35 m ma 21 were from soil mantled transport limited spurs in the humid temperate region around the base of the se escarpment the lowest averaging about 1 5 m ma 21 were from the steep weathering limited rocky slopes of kings canyon and mt sonder in semi arid central australia between these extremes other factors come into play including rock type slope and recruitment of vegetation we measured intermediate average erosion rates from rocky slopes in the semi arid flinders and macdonnell ranges and from soil mantled sites at both semi arid tyler pass in central australia and the tropical monsoonal site at soil mantled sites in both the se and tropical north soil production generally declines exponentially with increasing soil thickness although at the tropical site this relationship does not persist under thin soil thicknesses and the relationship here is humped results from tyler pass show uniform soil thicknesses and soil production rates of about 6 5 m ma 21 supporting a longstanding hypothesis that equilibrium soil mantled hillslopes erode in concert with stream incision and form convex up spurs of constant curvature moreover weathering limited slopes and spurs also occur in the same region the average erosion rate for rocky sandstone spurs at glen helen is 7 m ma 21 similar to the tyler pass soil mantled slopes whereas the average rate for high quartzite spurs at mount sonder is 1 8 m ma 21 the extremely low rates measured across bedrock dominated landscapes suggest that the ridge valley topography observed today is likely to have been shaped as long ago as the late miocene these rates and processes quantified across different undisturbed landscapes provide critical data for landscape evolution models

does decreasing paraglacial sediment supply slow knickpoint retreat in four rivers in western scotland for which there is a well constrained record of relative base level fall the rate of postglacial bedrock erosion is quantifi ed by measuring the concentration of in situ cosmogenic 10be on strath terraces downstream of headward retreating knickpoints along channel gradients in 10be exposure age show two distinct trends upstream younging and constant age which we interpret as diagnostic of knickpoint retreat and diffusive transport limited incision respectively we show that bedrock channel incision and regional formation of strath terraces began shortly after deglaciation ca 11 5 ka and that knickpoint retreat rates peaked in the early to mid holocene erosion rates have since decreased by two orders of magnitude converging in the late holocene to low rates independent of stream power per unit channel area we infer this regional slowing in postglacial knickpoint retreat to be the result of the depletion of paraglacial sediment supply over the holocene leading to a defi ciency in tools for bedrock erosion our results imply that episodes of major fl uvial erosion may be in tune with glacial cycles and that sediment depletion following glacial interglacial transitions may be an important cause of bedrock erosion rate variations in rivers draining glaciated landscapes

why some alluvial rivers develop an anabranching pattern anabranching rivers have been identified globally but a widely accepted and convincing theoretical explanation for their occurrence has remained elusive using basic flow and sediment transport relations this study analyzes the mechanisms whereby self adjusting alluvial channels can anabranch to alter their flow efficiency sediment transport capacity per unit of stream power it shows that without adjusting channel slope an increase in the number of channels can produce a proportional decrease in flow efficiency a finding particularly relevant to understanding energy consumption in some braided rivers however anabranching efficiency can be significantly increased by a reduction in channel width as occurs when vegetated alluvial islands or between channel ridges form the counteracting effects of width reduction and an increasing number of channels can cause with no adjustment to slope an otherwise unstable system underloaded or overloaded to achieve stability as with other river patterns anabranching can be characterized by stable equilibrium or accreting disequilibrium examples copyright 2007 by the american geophysical union

lowland river responses to intraplate tectonism and climate forcing quantified with luminescence and cosmogenic 10be intraplate tectonism has produced large scale folding that steers regional drainage systems such as the 1600 km long cooper ck en route to australia s continental depocentre at lake eyre we appl

fluvial response to tectonic activity in an intra continental dryland setting the neales river lake eyre central australia abstract geomorphological studies in the centre of the australian continent have emphasised the antiquity of the australian landscape typically considered tectonically stable evidence from the neales river on the western shore of lake eyre indicates that mild epeirogenic forces have deformed sediments of miocene age deformed bedding planes small scale folds and fracture systems reflect consistent miocene and younger tectonic activity in central and southern australia this compression was mild resulting in broad gently plunging folds these folds are evident in the miocene strata but not in the overlying quaternary strata elsewhere in the study area the landscape has been rearranged to preserve features in the geomorphic record that indicate a second phase of tectonic activity in the early to mid pleistocene these include stream diversions preserved on alluvial fans and floodplains formed downstream of faults

functional relationships between vegetation channel morphology and flow efficiency in an alluvial anabranching river 1 water and sediment flux interactions are examined in magela creek an alluvial anabranching sand bed river in the northern australian tropics dense riparian vegetation stabilizes the channels and floodplains thereby preventing erosional instability at flow depths up to 6 2 times bankfull and discharges up to 15 times bankfull narrow anabranching channels characterize 92 of the alluvial reach and transport bed load more efficiently than short reaches of wide single channels yet overall 29 12 of the bed load is sequestered and the average vertical accretion rate is 0 41 0 17 mm yr 1 along the 12 km study reach the most effective discharge for transporting sediment 40 45 m3 s 1 is consistent at all 5 stations 10 channels examined and is equivalent to the channel forming discharge it has an average recurrence interval of 1 01 years occurs for an exceptionally long portion 13 15 of the annual flow duration and averages a remarkable 2 1 times bankfull the high flow efficiency i e bed load transport rate to stream power ratio of the anabranches is facilitated by low width depth channels with banks reinforced by vegetation colonnades of bank top trees confine high velocity flows overbed i e over the channel bed at stages well above bankfull at even larger overbank flows momentum exchange between the channels and forested floodplains restrains overbed velocities in some cases causing them to decline thereby limiting erosion magela creek exhibits a complicated set of planform cross sectional and vegetative adjustments that boost overbed velocities and enhance bed load yield in multiple channels while restraining velocities and erosion at the largest discharges

continuous 150 k y monsoon record from lake eyre australia insolation forcing implications and unexpected holocene failure our reconstructed history of lake eyre provides the first continuous continental proxy record of australian monsoon intensity over the past 150 k y this continental record s broad correspondence to the marine isotope record demonstrates that this very large catchment with its hydrology dependent on a planetary scale climate element responds to milankovitch scale climate forcing abrupt transitions from dry phases to wet phases ca 125 and 12 ka coincide with northern hemisphere winter insolation minima rather than southern hemisphere summer insolation maxima indicating that northern hemi sphere insolation exerts a dominant control over the intensity of the australian monsoon stratigraphic and dating uncertainties of other wet phases preclude conclusive correlation to specific insolation signals but within the uncertainties are consistent with northern hemisphere forcing regardless of the hemispheric forcing the low intensity of the early holocene australian monsoon by comparison with the last interglacial and particularly the last high level lacustrine event at 65 60 ka when all forcing elements were modest is an enigma that can be explained by a change in boundary conditions within australia

bedrock incision rock uplift and threshold hillslopes in the northwestern himalayas the topography of tectonically active mountain ranges reflects a poorly understood competition between bedrock uplift and erosion dating of abandoned river cut surfaces in the northwestern himalayas reveals that the indus river incises through the bedrock at extremely high rates 2 12 mm yr 1 in the surrounding mountains the average angles of hillslopes are steep and essentially independent of erosion rate suggesting control by a common threshold process in this rapidly deforming region an equilibrium is maintained between bedrock uplift and river incision with landsliding allowing hillslopes to adjust efficiently to rapid river down cutting

cainozoic stratigraphy palaeoenvironments and geological evolution of the lake eyre basin abstract for a large part of inland australia weathering and erosion prevailed from the cenomanian to the late paleocene subsidence commencing in the late paleocene produced a depocentre the lake eyre basin in which sedimentation occurred in three main phases 1 fluviolacustrine sand silt clay and carbonaceous horizons from latest paleocene to middle eocene 2 dolomite and magnesium rich clay and sand deposited in extensive shallow alkaline lakes from latest oligocene miocene and 3 red clay silt and sand were deposited in fluvial lacustrine and aeolian settings during the pliocene and quaternary widespread weathering and silicification of sediments occurred in the late eocene oligocene and again in the pliocene the latter also accompanied by ferruginisation the silcrete sheets were folded into broad domes during the oligocene and again in the pliocene when faulting marginal to the southern ranges also occurred from the late paleocene to early eocene the basin supported rainforest growing in megathermal to mesothermal conditions by the middle eocene vegetation had changed to localised riparian forest in valley bottoms and more open sclerophyllous woodland in the hinterland indicating monsoonal conditions for most of this early tertiary interval deposition was by broad braidstreams flowing northwards in the miocene scattered elements of megathermal forest still existed but open woodland was far more extensive strong climatic seasonality and elevated temperatures promoted the deposition of thick dolomites in giant alkaline lakes the lakes and the diverse vegetation were home to a rich aquatic and terrestrial fauna by the pliocene climate was semiarid and vegetation mainly open casuarinaceae dominated woodland with very rare stands of forest confined to edaphically suitable sites increasing aridity during the quaternary was punctuated by pluvial intervals vast lakes formed during the interglacials largely as a result of higher rainfall in queensland drier windier conditions during the glacials particularly the last led to the development of extensive dunefields

river incision or diversion in response to bedrock uplift introductionmany researchers have examined the long term behavior of alluvialrivers i e schumm et al 1987 snow and slingerland 1990 paola et al 1992 on long time scales alluvial rivers act as sediment transport systemsthat broadly deposit sediment over low areas in their basins i e tucker andslingerland 1996 the behavior of bedrock rivers is less well understood although most workers agree that bedrock erosion is some function of streampower howard and kerby 1983 seidl and dietrich 1992 howard et al 1994 accordingly researchers addressing a river s response to bedrock up lift equate incision with relatively high stream power and diversion with rela tively low stream power e g burbank et al 1996 however these studiesassume that the erosion rate of the bedrock channel across the mountainrange controls the eventual outcome they have not examined the behavior ofthe alluvial river upstream and downstream of the uplift we propose to lookat the entire erosional and depositional river system and examine the long term response of a coupled alluvial bedrock river system to tectonic uplift our motivation is general and aims at a greater understanding offluvial and tectonic interactions but our model is necessarily both specificand simplified the tectonic uplift of a bedrock massif into the path of a later ally unconstrained alluvial river such a scenario has two possible out comes either the river maintains its original course and incises through theuplift or the river diverts and forms a new course around the uplift a sig nificant complication in the analysis of this scenario is that the evolvingriver system is partial alluvial and partial bedrock channeled because thebehaviors of these two river types are different modeling requires couplingdiverse systems we construct an analytical model to perform a first orderanalysis of this coupled system our objective is to identify the specific fac tors that determine the final outcome of river diversion or incision our model focuses on long time scales 10

response of alluvial rivers to slow active tectonic movement alluvial rivers respond to valley slope deformation caused by active tectonics in various ways depending on the rate and amount of surficial deformation and on the type of river on the basis of experimental results and field examples hypothetical models of river response to anticlinal uplift and synclinal subsidence were developed for different types of alluvial rivers an experimental braided channel responded to anticlinal uplift across the channel with degradation and terrace formation in the central part of the uplift with subsidence aggradation in the central reach was the main response transverse bars developed downstream of the subsidence axis an experimental meandering channel responded to slope steepening with a sinuosity increase bank erosion and point bar growth occurred downstream of the anticlinal axis and upstream of the synclinal axis upstream of the uplift axis and downstream of the subsidence axis where the slope was flattened water flooded over bars local convexity in longitudinal profiles of the middle rio grande new mexico is considered to be formed by a domal uplift local aggradation and degradation could be explained by the effect of uplift the san joaquin river california which is now highly controlled does not show clear adjustment to the rapid subsidence due to ground water withdrawal it shows however a channel pattern adjustment to active tectonic subsidence that has been occurring for a long time the san antonio and guadalupe rivers in texas both increase their sinuosity significantly where monoclinal movements steepen valley slopes

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

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

geomorphic and sedimentary response of rivers to tectonic deformation a brief review and critique of a tool for recognizing subtle epeirogenic deformation in modern and ancient settings abstract rivers are extremely sensitive to subtle changes in their grade caused by tectonic tilting as such recognition of tectonic tilting effects on rivers and their resultant sediments can be a useful tool for identifying the often cryptic warping associated with incipient and smaller scale epeirogenic deformation in both modern and ancient settings tectonic warping may result in either longitudinal parallel to floodplain orientation or lateral normal to floodplain orientation tilting of alluvial river profiles alluvial rivers may respond to deformation of longitudinal profile by 1 deflection around zones of uplift and into zones of subsidence 2 aggradation in backtilted and degradation in foretilted reaches 3 compensation of slope alteration by shifts in channel pattern 4 increase in frequency of overbank flooding for foretilted and decrease for backtilted reaches and 5 increased bedload grain size in foretilted reaches and decreased bedload grain size in backtilted reaches lateral tilting causes down tilt avulsion of streams where tilt rates are high and steady down tilt migration combing where tilt rates are lower each of the above effects may have profound impacts on lithofacies geometry and distribution that may potentially be preserved in the rock record fluvial sedimentary evidence for past tilting is traditionally based on the assumption that depositional features reminiscent of modern fluvial tectonic effects are evidence for past tectonic effects where it is closely associated with historically active structures or where non tectonic causes cannot be invoked however caution must be exercised when using these effects as criteria for past or current tectonic warping as these effects may be caused by non tectonic factors these non tectonic causes must be eliminated before tectonic interpretations are made

quantitative resolution of the debate over antiquity of the central australian landscape implications for the tectonic and geomorphic stability of cratonic interiors we report the first measure of long 100 myr and short 1 myr term denudation rates from key geologically stable landforms in the davenport range central australia these landforms have previously been assigned a cambrian age which arguably places them amongst the oldest persistent landforms on the continent if not on earth our results from combined apatite fission track thermochronology and in situ cosmogenic radionuclide analyses using 10 be and 26 al show that while average exhumation rates are low the denudation history for this cratonic region is incompatible with extreme sub aerial longevity and long term tectonic and geomorphic stability our revised model for the landscape evolution of this region is consistent with one of maximum burial prior to and during the mesozoic followed by a phase of kilometre scale exhumation that was largely complete by the beginning of the cainozoic we suggest that a similar process of burial and exhumation has probably been responsible for the sub aerial preservation of seemingly ancient landforms elsewhere in australia

a detailed receiver function image of the sedimentary structure in the bohai bay basin abstract if the site at which receiver functions are constructed is filled by sediments then the waveforms from these receiver functions are dominantly controlled by the sedimentary structures within the first few seconds after the direct p arrival based on this observation waveform data collected at 44 temporary seismic stations have been used to image the sedimentary structure of the bohai bay basin a major continental petroliferous basin in eastern china an adapted hybrid global waveform inversion method was applied to the receiver functions to extract structural information beneath each of the stations the derived s velocity structure provides for the first time a basin scale seismic image of detailed sedimentary stratification the sedimentary cover of the basin is about 2 12 km thick consisting of cenozoic mesozoic and paleozoic strata from top to bottom the structural features presented in the s velocity image coincide quite well with the depression uplift type of tectonic system in the bohai bay basin the reconstructed morphology of the sedimentary layers provides seismological evidence for the two stage evolution of the intracontinental basin that were caused by an intensive tectonic regime transition in late mesozoic immediately following the lithospheric reforming of the eastern china continent