an isotopic mixing model for the origin of granitic rocks in southeastern australia a simple mixing process was a significant element in the genesis of many southeastern australian granitic rocks major and trace element abundances are near linearly correlated nd and sr initial isotopic compositions define a simple hyperbolic trend and many initial 87sr 86sr ratios are a regular function of rb sr ratios geological arguments and regression of geochemical variation diagrams place limits on the nature of the end members the high si end member is meta sedimentary derived magma comparable in composition to the cooma granodiorite the one pluton in the region surrounded by and clearly derived from regional metamorphic rocks the low si end member is basaltic material with similarities to rare gabbros also found in the area isotope dilution calculations based upon initial sr and nd isotopic compositions deduced for the end members yield realistic hypothetical sr and nd concentrations for the end members in a demonstration of the internal consistency of the model all of the granitic rocks from hornblende tonalites to cordierite granodiorites are a single broad family products of variable mixing between distinct batches of basaltic material and a uniform partial melt of the regional basement

fractional crystallization of mantle derived melts as a mechanism for some i type granite petrogenesis an example from lachlan fold belt australia the mt buller igneous suite in the southeastern lachlan fold belt encompasses a large variety of rock types from gabbros through diorites to granites mafic rocks and enclaves have primitive mantle like initial 87 sr 86 sr values 0 7037 0 7045 and nd values 5 6 to 4 1 the granites do not show distinctively more radiogenic initial 87 sr 86 sr values suggesting they are derived from the same parent as the gabbros most of the mt buller rocks do not show a positive correlation between silica and initial 87 sr 86 sr or between silica and 143 nd 144 nd values indicating that neither crustal contamination nor mixing between mantle and crustal derived melts has been important and that these rock types are likely to have formed by fractional crystallization from a common mantle derived parent some scatter in compatible trace elements particularly in granites and diorites may be explained by mixing geochemical modelling confirms a comagmatic origin of the suite magma generation probably took place in the subduction modified upper mantle this mechanism may play an important role in i type granite petrogenesis in particular tectonic settings such as during an efficient slab roll back or sinking of oceanic crust in divergent subduction conditions

catchment clearing accelerates the infilling of a shallow subtropical bay in east coast australia abstract understanding processes that govern the transport and distribution of terrestrial sediments to and within bays is critical for interpreting the drivers of long term changes in these ecosystems on the east coast of australia increased soil erosion and sediment delivery following extensive land clearing in the contributing catchments associated with european settlement is highlighted as a key driver of the decline of numerous nearshore habitats including seagrass meadows and in shore coral reefs here we use optical radiocarbon and radionuclide dating to estimate mass accumulation rates and type of terrestrial sedimentation in central moreton bay during the holocene we compare the long term rates of infilling within the central basin with the recent past and show a 3 9 fold increase in sediment accretion over the last 100 years compared to the long term last 1500 to 3000 yrs average infilling during the holocene is not spatially uniform with preferential deposition occurring within the now submerged palaeochannels of the brisbane and pine rivers we suggest that modern turbidity regimes in moreton bay are the result of the compounded effect of both a historical increase in fine sediment supply and a rapid decline in the effective storage capacity of the basin

determination of airflow across the alpine ridge by a combination of airborne doppler lidar routine radiosounding and numerical simulation summary the wind infrared doppler lidar wind instrument was eown on board the aircraft falcon of the deutsches zentrum fur luft und raumfahrt on two missions during the special observing period sop of the mesoscale alpine programme map during the erst eight two complete sections of horizontal wind speed and direction were sampled up to a height of 7 km from innsbruck to the po basin and back from the second mission 11 wind soundings from 11 km downwards are presented along a route from a jet stream of up to 45 m s i1 above berlin towards the alps a routine radiosounding from milano and episode type simulations with the meso nh modelling system are used for detailed comparisons and to obtain comparative statistics

human impacts on fluvial systems in the mediterranean region the long history of substantial human impacts on the landscape of the mediterranean region and their effects on fluvial systems is documented these effects have included impacts of deforestation and other land use changes agricultural terracing on a wide scale water transfers and irrigation schemes during the 20th century major changes were made directly to channels through channelisation construction of dams of various sizes and extraction of gravel and indirectly by reforestation these changes have caused a major phase of incision on some rivers runoff and soil erosion have been affected by types of crops and agricultural practices as well as by the varying extent of cultivation and grazing some recent agricultural practices involve wholescale relandscaping of the topography and alteration of surface properties of material the importance of analysing the connectivity within different land units and of the spatial position of human activity within a catchment is illustrated the analysis of connectivity is the key to understanding the variability of impact and the extent of propagation of effects

estuarine abandoned channel sedimentation rates record peak fluvial discharge magnitudes abstract fluvial sediment deposits can provide useful records of integrated watershed expressions including flood event magnitudes however floodplain and estuarine sediment deposits evolve through the interaction of watershed marine sediment supply and transport characteristics with the local depositional environment thus extraction of watershed scale signals depends upon accounting for local scale effects on sediment deposition rates and character this study presents an examination of the balance of fluvial sediment dynamics and local scale hydro geomorphic controls on alluviation of an abandoned channel in the salinas river lagoon ca a set of three sediment cores contained discrete flood deposits that corresponded to the largest flood events over the period of accretion from 1969 to 2007 sedimentation rates scaled with peak flood discharge and event scale sediment flux but were not influenced by longer scale hydro meteorological activities such as annual precipitation and water yield furthermore the particle size distributions of flood deposits showed no relationship to event magnitudes both the responsiveness of sedimentation and unresponsiveness of particle size distributions to hydro sedimentological event magnitudes appear to be controlled by aspects of local geomorphology that influence the connectivity of the abandoned channel to the salinas river mainstem well developed upstream plug bar formation precluded the entrainment of coarser bedload into the abandoned channel while salinas river mouth conditions open closed in conjunction with tidal and storm surge conditions may play a role in influencing the delivery of coarser suspended load fractions channel adjacent sediment deposition can be valuable records of hydro meteorological and sedimentological regimes but local depositional settings may dominate the character of short term interdecadal signatures

post fire hydrological response and suspended sediment transport of a terraced mediterranean catchment in july 2013 a wildfire severely affected the western part of the island of mallorca spain during the first three post fire hydrological years when the window of disturbance tends to be more open the hydrological and sediment delivery processes and dynamics were assessed in a representative catchment intensively shaped by terracing that covered 37 of its surface area a nested approach was applied with two gauging stations covering 1 2 km2 and 4 8 km2 built in september 2013 that took continuous measurements of rainfall water and sediment yield average suspended sediment concentration 1 503 mg l 1 and the maximum peak 33 618 mg l 1 were two orders of magnitude higher than those obtained in non burned terraced catchments of mallorca this factor may be related to changes in soils and the massive incorporation of ash into the suspended sediment flux during the most extreme post fire event 50 mm of rainfall in 15 minutes reaching an erosivity of 2 886 mj mm ha 1 h 1 moreover hysteretic counter clockwise loops were predominant 60 probably related to the increased sensitivity of the landscape after wildfire perturbation though the study period was average in terms of total annual precipitation even higher in intensities minimal runoff 2 and low sediment yield 6 3 t km 2 y 1 illustrated how the intrinsic characteristics of the catchment i e calcareous soils terraces and the application of post fire measures limited the hydrosedimentary response despite the wildfire impact

paleohydraulic reconstruction of flash flood peaks from boulder deposits in the colorado front range nine watersheds in the colorado front range with steep bedrock channels were used to test the accuracy of paleohydraulic reconstruction of large flash floods using boulder deposits the nine basins consist of eight small ungauged basins ranging in size from 1 6 to 29 km2 and the big thompson river at the mouth of the big thompson canyon draining 790 km2 between 1923 and 1976 all nine basins had had one catastrophic flash flood the magnitude of which has been estimated by the conventional slope area method in each basin coarse boulder deposits of the large flash floods were identified and three axes of the five largest boulders were measured along with at least two profiles of the valley cross section a simple arithmetic average of two theoretical and two empirical relationships was used to estimate average flood velocity using boulder size and shape average depth was estimated as the arithmetic average of four values computed from the manning equation a regression equation for boulder size and unit stream power a relative smoothness equation and a modified shields relationship the appropriate flood width for the estimated average depth was found by iteration using the valley cross sections the paleohydraulic discharges thus computed generally underestimate conventional slope area discharge estimates on small streams by as much as 75 although the average amount is only 28 too low and the reconstructed discharge in one stream was 31 too large the big thompson river flood of 1976 was overestimated by 76 reasons for discrepancy in reconstructed peaks could include 1 the possibility that floods may have been able to move boulders larger than those available to be moved 2 overestimation of the slope area discharge because high water marks were set prior to erosion of the channel 3 underestimation of original roughness coefficients and 4 macroturbulent effects during fast deep flows the paleohydraulic technique is applied to two other streams in colorado with sedimentological evidence of large flash floods but no conventional indirect discharge estimates a small tributary to the big thompson river draining 1 8 km2 has a paleohydraulic reconstructed flood peak of about 60 m3 s from a flood in 1976 using boulders excavated from a foundation site in holocene alluvium along boulder creek in boulder colorado a paleohydraulic reconstructed flood peak of between 860 and 1 512 m3 s is calculated this is 1 4 to 2 4 times the magnitude of the estimated 500 yr flood

catchment controls and human disturbances on the geomorphology of small mediterranean estuarine systems abstract geographic signatures are physical and human induced characteristics or processes that identify comparable or unique features of estuaries along latitudinal gradients in mediterranean areas the microtidal regime and the strong seasonal and inter annual contrasts cause an alternation between relatively high runoff and arid conditions furthermore the long history of human settlement also increases the complexity in the study of these estuarine systems this study investigates these signatures of the estuaries located within the mallorcan eastern coast which are geomorphologically homogeneous because of a similar bedrock geology and holocene history a multi method approach focused on the integration of geomorphometry hydraulics historical sources and statistics was used we explore the role played by catchment morphometric parameters severe flash flood events and human disturbances in controlling the geomorphology of 10 beach barrier enclosed fluvial incised lagoons most of the lagoons discharge into calas ranging in size from 1345 to 17 537 m 2 and their related catchments are representative of the mediterranean hydrological systems multiple regression models illustrate that the size slope and drainage network development of the catchments explain the variance in length r 2 0 67 volume r 2 0 49 area r 2 0 64 circularity r 2 0 72 and average width r 2 0 81 of the lagoons depending on these catchment morphometric variables the shape of the lagoons is also determined by the occurrence of catastrophic flash floods which cause scouring and dredging whereas the ordinary flood events and sea storms promote refilling and sedimentation a historical analysis since 1850 documented 18 flood events 5 of which were catastrophic with destructive effects along the catchments and large morphological changes in coastal lagoons high intensity rainfall up to 200 mm in 2 h the geomorphometry of the catchments and the massive construction of terraces and transverse walls are involved in the generation of catastrophic flood events additionally the lagoons were altered considerably by human intervention for flood control and to allow for an increased amount of human activities within the surrounding areas although the high recurrence of catastrophic flood events causes a persistent difficulty in the human battle to dominate these ecosystems therefore the area occupied by lagoons increased between 1956 and the present time from 31 981 m 2 to 63 802 m 2 because of the high recurrence of catastrophic flood events furthermore tourism demand and a social conservation consciousness have promoted restoration and preservation since the 1990s this study has improved the geomorphological knowledge of small mediterranean estuaries affected by human disturbances in the high energy environment found in mallorca

he sr and nd isotopes in xenoliths from hawaii and other oceanic islands abstract isotopic analyses on he whole rock and sr nd separated clinopyroxenes are reported for ultramafic and gabbroic xenoliths from the hawaiian islands canary islands kerguelen gough and madeira the he isotopic compositions in samples of varied petrologic type from hawaii show a remarkably narrow range r ra 8 2 9 5 are within the previously reported range for hawaiian xenoliths and are indistinguishable from the range of 3he 4he ratios seen in morb in contrast sr and nd isotopic compositions show a significant range samples from the canary islands kerguelen gough and madeira considered as a group show a similar trend with a restricted range in 3he 4he 5 2 7 ra contrasted by sr and nd isotopic compositions extending over almost the entire range of oceanic basalts the relationship between he and sr nd isotopes of ocean island xenoliths are strikingly similar to that observed for continental ultramafic xenoliths by porcelli et al 1986 1 these systematics suggest metasomatic introduction of lithophile sr and nd and volatile he elements into the lithosphere beneath ocean islands overprinting depleted mantle isotopic characteristics the addition of volatiles must be accomplished by a different process to that of lithophiles probably due to selective transport most likely migration of a lithophile poor co2 h2o fluid consideration of he sr data for oceanic basalts suggests that similar fluid related processes may operate prior to or during mantle melting if so the interpretation of he sr relationships of oceanic basalts in terms of simple mixing between isotopically well defined sources is likely to be invalid

controls on late quaternary incised valley dimension along passive margins evaluated using empirical data incised valleys are canyon like features that initially form near the highstand shoreline and evolve over geological time as rivers erode into coastal plains and continental shelves to maintain equilibrium gradient profiles in response to sea level fall most of these valleys flood during sea level rise to form estuaries incised valley morphology strongly controls the rate of creation of sediment accommodation valley fill facies architecture and the preservation potential of coastal lithosomes on continental shelves and affects coastal physical processes nonetheless little is known about what dictates incised valley size and shape and whether these metrics can be used to explain principal formation processes the main control on alluvial channel morphology over human time scales is discharge this is based on numerous empirical studies and is well constrained because all variables are easily measured at this short time scale knowledge of long term river evolution over a complete glacio eustatic cycle on the contrary remains largely conceptual experimental and based on individual systems because variables that are thought to drive morphological change are not easily quantified in spite of this difficulty existing models of incised valley formation at the coast suggest that valley evolution is driven largely by downstream forcing mechanisms highlighting sea level and shelf gradient morphology as the dominant controls on valley incision although valleys are cut by rivers whose channels are a direct reflection of discharge little empirical data exist in coastal areas to address the degree to which valley evolution is governed by upstream controls the late quaternary is the best time period to examine because it provides the most complete sedimentary record and many variables including sea level tectonics substrate lithology and drainage network characteristics are accurately constrained here 38 late quaternary valleys along the coast of two different passive continental margins are compared which suggests that valley shape and size are governed primarily by upstream intrinsic controls such as discharge valley width depth and cross sectional area are found to be predictable at the highstand shoreline and are scaled with the size of their drainage basin which has important implications for estimating sediment discharge to continental shelves and deep water environments during periods of low sea level

structurally controlled drainage basin development in the south of menorca western mediterranean spain abstract the south of menorca consists of a gently folded upper miocene carbonate platform over which a drainage system has developed three areas with different drainage characteristics have been delimited the central area the eastern area and the western area the central area is characterised by deep streams with steep slopes whereas the western and eastern areas have slightly incised streams with gentle slopes the drainage development has been controlled by the inversion of a normal fault in pliocene times resulting in a wide anticline with a nne ssw orientation the deep streams of the central area follow the faults associated with this anticline the amount of incision achieved by these streams depends on the proportion of impermeable rocks exposed in the drainage basin the streams draining basins with a large proportion of impervious rocks have concave longitudinal profiles whereas those from catchments with a smaller area of impermeable materials have concave convex profiles streams with minor incision are found in the western and eastern areas of the carbonate platform given that their drainage basins are constituted by permeable materials

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

shape and microstructure of microgranitoid enclaves indicators of magma mingling and flow abstract at tarandore point 328 km south of sydney new south wales australia two tonalite phases are in contact with a gabbroic diorite all belonging to the moruya batholith lobate to crenulate contacts pillowing of the more mafic phase in the more felsic phase net veining of the more mafic phase by the more felsic local chilling of the more mafic phase against the more felsic and an abundance of rounded to elongate microgranitoid enclaves all suggest mingling of magmas at the site of emplacement therefore all phases were emplaced before the others solidified and an order of intrusion cannot be determined the variety of microgranitoid enclaves suggests that repeated magma mingling has occurred linear geochemical trends indicate either magma mixing or restite unmixing as a prime cause of variation in the members of the moruya suite of granitoids direct evidence of mixing is not present but evidence that the magmas were substantially liquid at the time of emplacement sugests that mixing is possible restite unmixing is unlikely to be the prime process because near minimum melts which would occur in all granitoid phases according to that model should mix easily rather than mingling in fact mingling has occurred between tonalite phases of very similar composition which would not be expected if the liquid parts of enclaves were minimum melts available experimental and theoretical data on mixing in both magma chambers and conduits cannot be applied directly to the occurrence at tarandore point owing to inadequately constrained parameters but mixing generally should be favoured by higher temperatures which is consistent with our inference that relatively high proportions of melt were present in the granitoid phases at the time of emplacement conduit mixing may be reflected in a local zone of strong to extreme elongation of enclaves in which the distortion has been accomplished by magmatic flow without solid state deformation as evidenced by strong dimensional preferred orientations coupled with a lack of microstructural evidence of intragranular plastic strain this suggests that elongate enclaves should not be used as indicators of solid state deformation or as tectonic strain markers without microstructural evidence that suitably strong intracrystalline plastic deformation has taken place

petrology and geochemistry of cambrian boninites and low ti andesites from heathcote victoria in the heathcote greenstone belt of central victoria a sequence of boninites and low ti andesites is overlain and intruded by tholeiitic basalts with affinities to backarc basin basalts two suites of boninites have been identified one type a with ti zr ratios of 63 4 la yb n of 2 3 and hree 5 times chondritic levels the other suite type b overlies type a boninites and has ti zr ratios of 23 3 and lower tio2 and hree contents 2 3 chondrite but shows significantly greater lree enrichment with la yb n greater than 5 fractionation within both suites was largely controlled by the low ca pyroxenes protoenstatite and enstatite plagioclase phyric low ti high mg andesites occur in fault contact with the boninites and have ti zr and la yb n ratios very close to those of type b boninites but at higher absolute abundances of tio2 and hree they are not related to either boninite suite by any realistic fractionation scheme but originated from the same source as type b boninites by approximately half the degree of partial melting that generated the boninites

mixing of cordierite granitoid and pyroxene gabbro and fractionation in the santa olalla tonalite andalucia abstract the asymmetricaly zoned santa olalla pluton consists of several facies gabbro a tonalitic group that includes both hornblende diorite and cordierite bearing quartz monzonite granitic dykes and enclaves enclaves are an ubiquitous component and in places they occur in swarms the tonalites and enclaves display extremely abundant disequilibrium microstructures pyroxene replaced by actinolite actinolite by hornblende hornblende by biotite biotite by hornblende and both calcic plagioclase and biotite phenocrysts have been corroded in a disequilibrium melt phase most of these microstructures can develop during the evolution of a single magma but the replacement of biotite suggests that crystal melt disequilibrium through magma mixing is responsble hornblende and actinolite occur in clots enclosing pyroxene the growth of actinolite was probably metastable at magmatic temperatures and replacement of pyroxene was controlled by diffusion of al subsequently hornblende replaced actinolite with a melt phase present plagioclase microstructures and compositions are consistent with batches of phenocrysts immersed in a disequilibrium melt that resulted from a bulk compositional change in the magma with which they re equilibrated bulk rock geochemistry indicates that the series gabbro through tonalite to granitic dykes cannot be simply related by a single fractionation trend gabbros vary by pyroxene fractionation the tonalites are a mixture of a cordierite bearing s type magma and a somewhat fractionated pyroxene gabbro thus it is h hybrid type plutonism not i type the granitic dykes developed after mixing by segregation of a residual melt from the hybrid tonalites there is evidence of some degree of fractionation of the tonalite facies after mixing the presence of aplites granitic dykes and divergence of incompatible trace elements from simple mixing ratios no variation can be attributed to restite unmixing

on morphometric properties of basins scale effects and hydrological response one of the important problems in hydrology is the quantitative description of river system structure and the identification of relationships between geomorphological properties and hydrological response digital elevation models dems generally are used to delineate the basin s limits and to extract the channel network considering pixels draining an area greater than a threshold area s in this paper new catchment shape descriptors the geometric characteristics of an equivalent ellipse that has the same centre of gravity the same principal inertia axes the same area and the same ratio of minimal inertia moment to maximal inertia moment as the basin are proposed they are applied in order to compare and classify the structure of seven basins located in southern france these descriptors were correlated to hydrological properties of the basins responses such as the lag time and the maximum amplitude of a geomorphological unit hydrograph calculated at the basin outlet by routing an impulse function through the channel network using the diffusive wave model then we analysed the effects of the threshold area s on the topological structure of the channel network and on the evolution of the source catchment s shape simple models based on empirical relationships between the threshold s and the morphometric properties were established and new catchment shape indexes independent of the observation scale s were defined this methodology is useful for geomorphologists dealing with the shape of source basins and for hydrologists dealing with the problem of scale effects on basin topology and on relationships between the basin morphometric properties and the hydrological response copyright 2002 john wiley sons ltd

the role of extreme floods in estuary coastal behaviour contrasts between river and tide dominated microtidal estuaries abstract contrasting modes of sedimentation and facies arrangement in tide and river dominated microtidal estuaries arise from the degree to which river or tidal discharge and sediment supply influences an estuary a distinct facies gradation exists in tide dominated systems from sandy barrier tidal delta associated environments at the coast through deep mud dominated middle reaches to fluvial sediment in the upper reaches in river dominated systems fluvial sediment extends to the barrier and flood tidal deltas are poorly developed or absent from the estuary a number of independent observations during extreme floods on the south african coast indicate that these types of estuary respond differently to extreme river floods and that the mode of response corresponds to estuary type tide dominated systems exhibit preferential erosion of noncohesive barrier and tidal delta sediments during river floods while the middle reaches remain little modified river dominated systems experience consistent erosion throughout their channel length during extreme floods the increased cohesion of riverine sediments and stabilisation of bars by vegetation in river dominated channels means that higher magnitude floods are necessary to effect significant morphological change barrier erosion including the tidal delta results in deposition of an ephemeral delta composed almost entirely of sands from these deposits in tide dominated estuaries in river dominated systems eroded channel sediments and material from the river catchment may augment barrier sediments in the ephemeral delta deposit post flood wave reworking of ephemeral delta sediments acts to restore barriers to pre flood morphology within a few years however in river dominated systems the additional sediment volume may produce significant coastal progradation that requires several years or decades to redistribute these different modes of flood response mediated by the nature of the estuary have implications for coastal behaviour at the time scale of months to several decades estuary coastal behaviour at river dominated estuaries may be influenced for several decades by post flood morphological adjustment tide dominated estuaries however respond more rapidly in reworking flood eroded sediment and are typically fully adjusted to modal wave and tidal conditions within a few months to a few years in addition the facies arrangement within the two estuary types renders tide dominated estuaries more responsive to minor floods while river dominated estuaries by virtue of more cohesive channel sediments require greater discharges to effect significant morphological change

palaeoclimate and palaeoenvironmental responses in the western mediterranean over the last 140 ka evidence from mallorca spain climatic change in the western mediterranean basin over the last 140 ka has been investigated from sediment and soil sequences along the coast of the northeastern part of mallorca spain palaeoclimate and palaeoenvironments are reconstructed from sediment and soil structures marine and terrestrial molluscan fauna grain size distributions mineral magnetics sediment and soil chemistry sem and oxygen isotope values dating is by osl and amino acid geochronometry along with marine molluscan faunal assemblages all oxygen isotope stages and substages from ois 6 to 1 are recorded mean annual temperatures m a t of c 19 2 c for the climatic optimum of the last interglacial compare with c 17 3 c for the present and are associated with high sea level extensive woodland and stable soils although wide temperature ranges are detected during this stage with values as low as c 10 3 c through ois 5d to 5a m a t fluctuated from 8 2 c to 17 9 c low sea level open vegetation effective river activity and aeolian sand and dust deposition characterize 5d and 5b while relatively high sea level and soil development on stable landscapes dominate ois 5c and 5a ois 4 is represented by m a t of c 4 9 c with aeolian sand and loess deposition limited river activity and weak soil development loess deposition persisted into ois 3 but at this time the m a t was c 13 c and with higher humidity and vegetation growth during the lgm ois 2 m a t was c 8 1 c and effective river slope and aeolian processes along with associated with limited vegetation cover were responsible for the most extensive changes in the landscape major rates of change occur during periods of climatic deterioration when the high levels of geomorphic energy were imposed on a landscape undergoing a breakdown of vegetation cover

control of upstream variables on incised valley dimension abstract it is well documented that sea level fell during the last glacial maximum shifting graded stream profiles out of equilibrium and causing rivers to incise into continental shelves although incised valleys have been heavily researched the interplay between upstream and downstream controls on incised valley dimension are not well constrained to address this lack of understanding we examined the cross sectional dimension of nine incised valleys located across the northern gulf of mexico margin and bounded by the sequence boundary associated with the last sea level lowstand these incised valleys are distinguished by drainage basins that vary in size by three orders of magnitude cover a margin that presently has a steep climate gradient and extend across a continental shelf that varies along strike in width and gradient incision depths vary for valleys that have similar gradient profiles but different drainage basin areas suggesting significant control of upstream variables on incised valley morphology additionally these data show a strong linear correlation between drainage basin area and incised valley cross sectional area this suggests applicability of the empirically derived relationship between modern discharge and cross sectional channel area to incised valleys when compared at the maximum highstand shoreline of the previous sequence incised valley dimension adjusts over a longer period than the lowstand and is in equilibrium with drainage basin area which is considered a proxy for long term discharge although base level fall promotes incision upstream variables control incised valley dimensions