quaternary glaciations in the southern hemisphere an overview abstract large glacier systems in antarctica have existed at least since the early miocene glaciers in the patagonian andes advanced in the late miocene and fluctuated several times during the pliocene as did ice masses elsewhere in the southern hemisphere sedimentological evidence of glaciation during the early and middle quarternary is best preserved in volcanic regions patagonia new guinea africa but is poorly constrained by dating there is evidence of glaciation during oxygen isotope stages 10 8 and 6 in several parts of the southern hemisphere but the only well dated advance of the middle quarternary is that of stage 6 in the transantarctic mountains during the last glaciation montane glaciers in parts of the southern hemisphere were as large during isotope stage 4 as during isotope stage 2 the last glaciation maximum stage 2 is well dated in tasmania new zealand and patagonia culminating as 21 18 ka bp following slight recession from the lgm limits late glacial advances peaked at 15 14 ka bp and at 12 10 ka bp major holocene advances occurred on at least three occasions during the last 5 ka in areas presently glacier covered

purely erosional cyclic and solitary steps created by flow over a cohesive bed an erodible surface exposed to supercritical flow often devolves into a series of steps that migrate slowly upstream each step delineates a headcut with an associated hydraulic jump these steps can form in a bed of cohesive material which once eroded is carried downstream as washload without redeposition here the case of purely erosional one dimensional periodic or cyclic steps in cohesive material is considered the st venant shallow water equations combined with a formulation for sediment erosion are used to construct a complete theory of the erosional case the solution allows wavelength wave height migration speed and bed and water surface profiles to be determined as functions of imposed parameters the analysis also admits a solution for a solitary step or single headcut of self preserving form

drainage basin evolution in the rainfall erosion facility dependence on initial conditions four experiments in alluvial drainage basin evolution were carried out in the rainfall erosion facility ref at colorado state university to investigate the dependence of basin evolution on initial topography basins were initially undissected each experiment began with a unique initial condition representing various end members of relief and hypsometry drainage network development hillslope processes basin denudation and basin response to base level lowering all depended strongly on the initial topography no classic model of drainage network evolution was found to be generally applicable initially planar slopes first developed subparallel channels that extended headward dendritically during an early phase of extension channel incision occurred first in the interior of the basin where saturation overland flow was greatest not at the basin outlet as assumed in most classic models of network development channels widened over time initiating lateral migration and drainage capture in the downslope portion of the watershed before transferring lateral migration upslope planar basins of larger initial gradient grew headward more quickly and become more deeply entrenched inhibiting late stage lateral migration an experiment with initial relief concentrated at a plateau edge evolved in several unique ways a high ratio of subsurface to surface flow gave rise to mass movements at the plateau edge and outlet channels deep channels were quickly cut initially but did not extend far upslope because slope instability undermined channel head migration leaving the plateau undissected and hence very slow to erode these results suggest that the distribution of relief within a basin exerts an important control on drainage network pattern and basin denudation in addition erosional basins may evolve in several distinct modes characterized by particular combinations of hypsometry hillslope processes and mean denudation rate

palaeoclimates in central and south america since 18 000 bp based on pollen and lake level records abstract the last 18 ka of palaeoclimates are discussed at 3 ka intervals based on palaeoenvironmental changes shown in pollen and lake level records from central and south america a total of 61 pollen records fulfill the requirements of continuity and chronology to be used in this synthesis 8 records from tropical and subtropical lowlands in central and south america 7 records from the central american highlands 26 records from the high andes north and south of the equator 2 records from the southern subtropics and 18 from the southern andes and subantarctic islands palaeoclimatic interpretation of the pollen records is semiquantitative based on bioclimatic parameters such as e g elevational temperature gradients or latitudinal precipitation gradients that can be related to vegetation zonation additional palaeoclimatic information is obtained from lake level records derived either from dated shorelines or from the limnological history of lake sediment sections large scale palaeoclimatic comparison of the proxy data records indicates that full and late glacial climates throughout central and south america were cooler than today by about 4 to 5 c but that moisture patterns showed regional differentiation thus in both the southern subtropics and high latitudes in southern chile conditions were substantially moister than today during full and late glacial times whereas everywhere else conditions were far drier than today in terms of palaeocirculation this scenario can be interpreted as a poleward shift of the subtropical as well as the westerly circulation a scenario that has been suggested by palaeoclimatic simulations from general circulation models gcm another major palaeoclimatic aspect predicted by the gcm simulations is the suppressed early holocene summer monsoon in the southern subtropics although proxy records are few from this zone their palaeoenvironmental history during that time shows a period of aridity that would support the model one of the most controversial aspects of south american palaeoclimates concerns the existence of a younger dryas equivalent a cold period between 11 and 10 ka bp based on the existing data from south america that show a great diversity of palaeoclimatic trends the concept of an interval that is characterized by the same climatic signal as documented for the north atlantic seems too simplistic moreover at this point only very few records have been analysed in sufficient detail to yield unambiguous climatic information for the interval in question the principal outcome of this palaeoenvironmental and palaeoclimatic synthesis is the better understanding of the type and quality of data available at present and the realization of regions and periods where much more and concerted effort is needed to address problems of intra and interhemispheric palaeoclimatic correlations only then can questions concerning the mechanism of climatic change be tackled successfully

topographic evolution and morphology of surfaces evolving in response to coupled fluvial and hillslope sediment transport 1 this paper quantifies how the ratio of sediment transport on hillslopes to sediment transport in channels influences surface and channel network morphologies and the dynamics of topographic evolution this problem is investigated by development and investigation of a simple deterministic model incorporating mass balance of sediment and runoff coupled with a law combining dispersive and concentrative sediment transport processes our analysis includes the identification of a new nondimensional parameter de that is a function of rainfall system size rock type and hydraulic regime and that is a measure of the relative importance of fluvial and hillslope sediment transport we show that de has an important influence on the surface morphology e g total exposed surface area and interface width which reflects surface roughness and relief channel network form e g channel sinuosity channel spacing and timescale of surface evolution surface and channel network morphologies are also strongly influenced by the overall surface slope relative to the magnitude of initial topographic roughness topographic evolution occurs in distinct phases of relief growth and decay the transition between which is controlled by a saturation phenomenon related to the growth of spatial correlations the scaling behavior of simulated topography with respect to both time and space is obtained and is shown to be independent of de roughness exponents are found to be independent of de but dependent on the magnitude of initial roughness interface width is shown to grow and decay as a logarithm of time

late pleistocene climate and water budget of the south american altiplano abstract geomorphic evidence from the peruvian bolivian altiplano indicates that during episodes prior to 28 000 and around 12 500 11 000 yr b p lakes covered an area about six and four times as large as at present respectively within the constraints of the heat and water budget model calculations are used to estimate the precipitation rate that would allow hydrologic equilibrium on this basis it is suggested that rainfall on the altiplano during the episodes of enlarged lakes was respectively some 300 and 200 mm annum 1 larger than at present representing increases of about 75 and 50 respectively field evidence suggests that the episodes of enlarged lakes on the altiplano may have preceded or coincided with periods of maximum glaciation in the neigh boring andes in this region with high elevation of the ice equilibrium line increased precipitation is particularly conducive to glaciation

hydrodynamic description for advective sediment transport processes and rill initiation a physically based model for advective sediment transport during rill initiation is developed based on 1 a short wavelength rescaling of the momentum balance equations for the surface water flux 2 a deforming coordinate system which characterizes local morphological changes of the surface during erosion and 3 a generalized transport function for the surface sediment flux which distinguishes the contributions of diffusive and advective transport a linear stability analysis of the coupled system indicates that an intrinsic minimum transverse length scale for rill initiation is forced by the cross slope pressure gradient in the surface water the wavelength of this initial rill spacing is dependent upon the relative significance of the advective component of sediment transport and the hydraulic efficiency of the surface water flux and is independent of the total length of the hillslope the hydrodynamic model presented can also be used to evaluate the nonlinear development of rills and rill networks subsequent to initiation

catchment drainage network scaling laws found experimentally in overland flow morphologies the scaling relation between the drainage area and stream length hack s law along with exceedance probabilities of drainage area discharge and upstream flow network length is well known for channelized fluvial regions we report here on a laboratory experiment on an eroding unconsolidated sediment for which no channeling occurred laser scanning was used to capture the morphological evolution of the sediment high intensity spatially nonuniform rainfall ensured that the morphology changed substantially over the 16 hr experiment based on the surface scans and precipitation distribution overland flow was estimated with the d8 algorithm which outputs a flow network that was analyzed statistically the above mentioned scaling and exceedance probability relationships for this overland flow network are the same as those found for large scale catchments and for laboratory experiments with observable channels in addition the scaling laws were temporally invariant even though the network dynamically changed over the course of experiment

basin self similarity hack s law and the evolution of experimental rill networks while the hierarchical organization of river basins has been well described little physical evidence exists on how such signatures change in time as a function of drainage network evolution using a soil mantled experimental landscape a fourth order rill network was developed in response to applied rainfall and base level lowering drainage basin area and tributary length scales were determined at discrete times during the evolution of the rill network results show that rill basin area exhibited self similarity across rill order space and as the network grew in time and that the coefficient of hack9s law once the network began to grow also was invariant with time this experimental evidence strongly supports the use of scaling arguments for drainage basin evolution and for the prediction of rill network development and organization on hillslopes and agricultural fields

the interaction between hydrology and geomorphology in a landscape simulator experiment an experimental landscape simulator has been developed which uses a rainfall simulator to create overland flow and erosion the simulator uses rainfall sprinklers that eliminate rainsplash and an artificial soil which has little cohesion experimental landscapes developed in the simulator evolved according to howard s headward growth model elements of glock s model could be identified during evolution i e initiation and maximum extension but other stages of this model were not observed i e extension and integration the horton concept of cross grading and micropiracy and stream piracy was not observed despite the dominance of overland flow nor the groundwater headward growth mechanism proposed by dunne the latter due to experimental design which eliminated any perched groundwater table the experimental apparatus produced model landscapes that are scaled down analogues of real world processes copyright 2001 john wiley sons ltd

theoretical basis for at many stations hydraulic geometry citation gleason c j wang j 2015 theoretical basis for at many stations hydraulic geometry geophysical research letters 42 17 7107 7114 doi 10 1002 2015gl064935

hillslope and channel evolution in a marine terraced landscape santa cruz california a flight of marine terraces along the central california coastline provides a unique setting for the study of topographic evolution wavecut platforms mantled by 2 6 m of marine terrace cover deposits are separated by 10 50 m tall decaying sea cliffs paleocliff edges become more rounded with age yet the details of the profiles and frequent bedrock exposure on the upper slopes imply weathering limited transport five bedrock stream channels etched through the marine terrace sequence display one to three distinct convexities in their longitudinal profiles detailed hand level surveys of the hillslopes and of the stream channel longitudinal profiles constrain hillslope evolution and channel incision components of a numerical model of landscape evolution we account for regolith production as a function of regolith depth in accord with the field observation that hillslope processes are presently dominated by the activities of burrowing rodents the transport process is taken to be diffusive stream incision is assumed to be controlled by stream power for which we use the surrogate of local drainage area slope product best fits of the numerical model to field data imply hillslope diffusivity is 10 m2 kyr 1 regolith production rate on bare bedrock is 0 3 m kyr 1 and falls off rapidly with regolith cover and the constant controlling the efficiency of stream incision is 5 to 7 10 7m 1 kyr1

the relationship between drainage density erosion rate and hilltop curvature implications for sediment transport processes drainage density is a fundamental landscape metric describing the extent of the fluvial network we compare the relationship between drainage density dd and erosion rate e using the channel hillslope integrated landscape development child numerical model we find that varying the channel slope exponent n in detachment limited fluvial incision models controls the relationship between dd and e with n 1 resulting in increasing dd with e if all other parameters are held constant this result is consistent when modeling both linear and nonlinear hillslope sediment flux we also test the relationship between dd and e in five soil mantled landscapes throughout the usa feather river ca san gabriel mountains ca boulder creek co guadalupe mountains nm and bitterroot national forest id for two of these field sites we compare dd to cosmogenic radionuclide crn derived erosion rates and for each site we use mean hilltop curvature as a proxy for erosion rate where crn derived erosion rates are not available we find that there is a significant positive relationship between dd e and hilltop curvature across every site with the exception of the san gabriel mountains ca this relationship is consistent with an n exponent greater than 1 suggesting that at higher erosion rates the transition between advective and diffusive processes occurs at smaller contributing areas in soil mantled landscapes

albedo changes milankovitch forcing and late quaternary climate changes in the central andes late quaternary humidity changes resulted in substantial modifications of the land surface characteristics in the altiplano of the atacama desert central andes reconstructions of surface albedo top of atmosphere toa albedo and short wave net radiation in the andes of northern chile for 20 14 10 7 and 0 ka suggest that surface and toa albedo increased substantially during periods of relatively humid environmental conditions i e with large palaeolakes glaciers and dense vegetation the decrease of summer shortwave net radiation and seasonality during the late glacial early holocene humid phase 14 to 10 ka due to earth s surface and atmospheric characteristics added to the effect of orbitally driven negative deviations of southern hemisphere austral summer insolation and minimum seasonality at 20 s therefore in situ radiative forcing is in contrast to the northern hemisphere tropics not a suitable explanation for enhanced convective precipitation and ultimately humid climatic conditions our results suggest that late quaternary humidity changes on the altiplano reflect a collective response to 1 environmental changes in the source area of the moisture e g re expansion of the rain forest and increased release of latent heat over amazonia and the chaco warm sea surface temperatures in the e pacific and 2 large scale circulation patterns and wave structures in the upper troposphere strength and position of the bolivian high divergent flow stimulating convection over the altiplano or that they even reflect a response to 3 interhemispherical teleconnections

erosive dynamics of channels incised by subsurface water flow 1 we propose a dynamical model for channels incised into an erodible bed by subsurface water flow the model is validated by the time resolved topographic measurements of channel growth in a laboratory scale experiment surface heights in the experiment are measured via a novel laser aided imaging technique the erosion rate in the model is composed of diffusive and advective components as well as a simple driving term due to the seeping water steady driving conditions may exist whenever channels are incised into a flat and level erodible bed by a water table replenished via steady on average rainfall under such steady driving conditions the model predicts an asymptotically self similar growing shape for the channel transects conversely given a transect shape that evolved under steady driving conditions and an estimate of the erosion rate at the bottom of the channel granular transport coefficients can be inferred from the static channel shape we report an estimate of these transport coefficients for a system of ravines incised into unconsolidated sand in the apalachicola river basin florida

a preliminary investigation of chlorine xanes in silicate glasses 1 chlorine speciation in silicate melts affects volatile exsolution rheology and thermodynamic properties of the melt but is poorly known x ray absorption near edge structure xanes spectra have been used to investigate cl speciation in 26 silicate glasses and to test the hypothesis that cl in silicate melts is hosted by species that combine cl and network modifying cations such as ca and mg results indicate that cl in cmas cao mgo al2o3 sio2 plus na2o k2o or mno silicate glasses exists as a combination of ca clx and mg clx species or possibly as mixed ca mgy clx species the geometry and stoichiometry of the proposed species is unknown but there are similarities between spectra from ca bearing melts and the spectra of hydrated cacl2 2h2o suggesting that the ca clx species could have a salt like atomic arrangement and ionic bonding further investigations using xanes alternative spectroscopic techniques and forward modeling approaches are required to distinguish between these possibilities

the origin of brines and salts in chilean salars a hydrochemical review abstract northern chile is characterized by a succession of north south trending ranges and basins occupied by numerous saline lakes and salt crusts collectively called salars fossil salt crusts are found to the west in the extremely arid central valley while active salars receiving permanent inflows fill many intravolcanic basins to the east in the semiarid cordillera sea salts and desert dust are blown eastward over the cordillera where they constitute an appreciable fraction of the solute load of very dilute waters salt content evaporative concentration of inflow waters leads to sulfate rich or calcium rich near neutral brines alkaline brines are almost completely lacking the alkalinity calcium ratio of inflow waters is lowered by the oxidation of native sulfur reducing alkalinity and the deposition of eolian gypsum increasing ca concentration theoretically so4 rich inflow waters and their derived so4 rich brines should be found in the intravolcanic basins of the cordillera because of the ubiquity of native sulfur while ca rich brines should prevail in sedimentary basins where ca rich minerals are abundant this relation is perfectly observed in the salar de atacama the largest in chile however several salars located within the volcanic cordillera belong to the ca rich group inflows and brines may have acquired their ca rich composition in pleistocene time when their drainage basins were mainly sedimentary later on recent lava flows and ignimbrites covered the sedimentary formations underground waters may have kept their early sedimentary signature by continuous recycling however the weathering of volcanic rocks tend to slowly shift the water compositions from the ca rich to the so4 rich type

paleohydrology of the laguna lejia north chilean altiplano and climatic implications for late glacial times paleoenvironmental and sedimentological data from laguna lejia 23 30 s 67 42 w 4325 m in the high altiplano of the chilean atacama desert indicate that climatic conditions during late glacial times were significantly wetter than today a water and energy budget model was used to simulate climatic scenarios that would have resulted in the observed changes in the water levels water surfaces water volumes and salinity during the time interval different climatic scenarios for the laguna lejia catchment include precipitation increases of over 100 up to 400 500 mm yr today 200 mm yr to account for the late glacial lake levels with shorelines 15 25 m higher than at present and a lake surface of 9 11 km2 compared to the present 2 km2 during the lake maximum about 13 500 11 300 yr b p finely laminated sediments consisting of mg calcite diatoms and sometimes gypsum were deposited the paleoenvironmental evidence indicates that north easterly wind direction prevailed and the summer rainfall resulted from a seasonal poleward shift of the tropical circulation the lake history of laguna lejia is representative for the altiplano area between 21 and 24 s

controls on the spacing of first order valleys 1 many landscapes are composed of ridges and valleys that are uniformly spaced even where valley locations are not controlled by bedrock structure models of long term landscape evolution have reproduced this phenomenon yet the process by which uniformly spaced valleys develop is not well understood and there is no quantitative framework for predicting valley spacing here we use a numerical landscape evolution model to investigate the development of uniform valley spacing we find that evenly spaced valleys arise from a competition between adjacent drainage basins for drainage area a proxy for water flux and that the spacing becomes more uniform as the landscape approaches a topographic equilibrium valley spacing is most sensitive to the relative rates of advective erosion processes such as stream incision and diffusion like mass transport such as soil creep and less sensitive to the magnitude of a threshold that limits the spatial extent of stream incision analysis of a large number of numerical solutions reveals that valley spacing scales with a ratio of characteristic diffusion and advection timescales that is analogous to a peclet number we use this result to derive expressions for equilibrium valley spacing and drainage basin relief as a function of the rates of advective and diffusive processes and the spatial extent of the landscape the observed scaling relationships also provide insight into the cause of transitions from rill like drainage networks to branching networks the spatial scale of first order drainage basins the contributing area at which hillslopes transition into valleys and the narrow range of width to length ratios of first order basins

fluvial and slope wash erosion of soil mantled landscapes detachment or transport limited many numerical landform evolution models assume that soil erosion by flowing water is either purely detachment limited i e erosion rate is related to the shear stress power or velocity of the flow or purely transport limited i e erosion deposition rate is related to the divergence of shear stress power or velocity this paper reviews available data on the relative importance of detachment limited versus transport limited erosion by flowing water on soil mantled hillslopes and low order valleys field measurements indicate that fluvial and slope wash modification of soil mantled landscapes is best represented by a combination of transport limited and detachment limited conditions with the relative importance of each approximately equal to the ratio of sand and rock fragments to silt and clay in the eroding soil available data also indicate that detachment entrainment thresholds are highly variable in space and time in many landscapes with local threshold values dependent on vegetation cover rock fragment armoring surface roughness soil texture and cohesion this heterogeneity is significant for determining the form of the fluvial slope wash erosion or transport law because spatial and or temporal variations in detachment entrainment thresholds can effectively increase the nonlinearity of the relationship between sediment transport and stream power results from landform evolution modeling also suggest that aside from the presence of distributary channel networks and autogenic cut and fill cycles in non steady state transport limited landscapes it is difficult to infer the relative importance of transport limited versus detachment limited conditions using topography alone copyright 2011 john wiley sons ltd

transformative geomorphic research using laboratory experimentation abstract laboratory experiments in geomorphology is the theme of the 46th annual binghamton geomorphology symposium bgs while geomorphic research historically has been dominated by field based endeavors laboratory experimentation has emerged as an important methodological approach to study these phenomena employed primarily to address issues related to scale and the analytical treatment of the geomorphic processes geomorphic laboratory experiments can result in transformative research several examples drawn from the fluvial and aeolian research communities are offered as testament to this statement and these select transformative endeavors often share very similar attributes the 46th bgs will focus on eight broad themes within laboratory experimentation and a diverse group of scientists has been assembled to speak authoritatively on these topics featuring several high profile projects worldwide this special issue of the journal geomorphology represents a collection of the papers written in support of this symposium

a new estimate of the holocene lowstand level of lake titicaca central andes and implications for tropical palaeohydrology new evidence from piston cores and high resolution seismic reflection data shows that water levels in lake titicaca were as much as 100 m below the present level during the early to mid holocene between 6 and 3 8 14c kyr bp climatological and modelling studies indicate that lake titicaca rainfall depends on convective activity in upwind amazonia the lake level data therefore suggest a drier amazon basin during this time this view is bolstered by an excellent match between the titicaca lake level curve and decreased methane concentrations in greenland ice previously ascribed to drying of low latitude wetlands blunier et al 1995 the postglacial history of lake titicaca fits a global pattern of lake level change in the tropics characterized by opposite phasing between the southern and northern hemispheres this pattern is most likely the result of orbital controls over the intensity of summer insolation

recent glacial history and paleoclimate of the peruvian bolivian andes abstract radiocarbon dates of glacial deposits in the peruvian bolivian andes are used to place the observed phases of glaciation in a common chronological framework the climatic conditions that may determine modern snowline are examined in order to understand the types of climatic forcing to which glaciers may have been sensitive in the past also considered are independent proxies of climatic change including pollen sequences lake level history and ice core data late pleistocene glaciation in central peru between 24 ka and 12 ka bp appears to have occurred during colder and perhaps drier conditions in bolivia a glacial maximum is dated to phases of late holocene glaciation in peru that correspond in part to the little ice age in the northern hemisphere appear to have been caused by a combination of colder and wetter conditions an overall warming trend may be the cause for the retreat of many glaciers in the region since the mid 19th century

low holocene level 7700 to 3650 years ago of lake titicaca bolivia abstract preliminary results of sedimentological and paleontological analysis of two cores taken in lake titicaca bolivia indicate that between 7700 and 3650 yr b p the lake level was up to 50 m lower than at present evaporitic deposits occurred at the maximum low lake level

the origin and distribution of salts on alluvial fans in the atacama desert northern chile the atacama desert has been predominantly hyperarid since the middle miocene combined ionic and x ray diffraction analysis shows that calcium sulphate is prevalent on three similar alluvial fans in salar basins across a transect of different environments in antofagasta province northern chile differences between the fans were largely due to the effect of local factors on salt input secondary redistribution and deposit preservation thus carbonate was notable in the high andes fan c and pre cordillera fan b whereas in the central valley fan a greater qualities of the more soluble salts chlorides and nitrates probably reflect the higher level of aridity and an oceanic source the camanchaca calcium sulphate distribution on the alluvial fans and on adjacent hilltops indicates an aeolian origin evidence from the pre cordillera fan b however suggests that salt input may have been episodic related to changes in conditions within the general aridity and possibly to stone pavement and soil development calcium sulphate sources range from an input in andean precipitation and the camanchaca to abundant regional evaporite deposits it is probable however that products of andean volcanism constitute the dominant primary source of calcium sulphate and that the salt has subsequently been distributed widely within the endoreic basins of the region by a combination of groundwater surface flow and the wind 1997 john wiley sons ltd

vegetation invasions into absolute desert a 45 th000 yr rodent midden record from the calama salar de atacama basins northern chile lat 22 24 s plant macrofossils percentage abundance of grass taxa fecal pellet d13 c and plant cuticle contents from 49 fossil rodent middens dated by 14 c record changes in local vegetation and precipitation since 45 ka calibrated or measured to thousands of calendar years before present in the central atacama desert lat 228 248s of northern chile the midden sites are along the hyperarid upper margin 2400 3100 m of the absolute desert in an extreme environment sparsely vegetated by annual herbs and halophytic shrubs conditions between 40 and 22 ka may have been at least intermittently dry and possibly cooler as implied by four middens with low species richness we infer a large increase in summer rainfall between 16 2 and 10 5 ka on the basis of the lowering of steppe grasses by as much as 1000 m prominence of c4 grasses and summer annuals high species richness and displacement of northern species at least 50 km south of their modern ranges the precipitation increase was greatest for a cluster of middens between 11 8 and 10 5 ka abrupt drying evident in a dramatic decrease in grass abundance occurred after 10 5 ka at all four midden localities increased percentages of