late quaternary pollen records from two ugandan mires evidence for environmental changes in the rukiga highlands of southwest uganda abstract high resolution pollen data from two mires in the rukiga highlands southwest uganda ahakagyezi swamp and muchoya swamp provide detailed evidence of the environmetal history of the region since ca 42 000 yr b p according to these data there a was period pre ca 42 000 yr b p when climatic conditions were similar to the present conditions considerably colder and drier than the present occurred during two periods in the past pre ca 42 000 yr b p to ca 32 000 yr b p and ca 21 000 yr b p to ca 12 000 yr b p the most recent period of climatic improvement began ca 14 000 yr b p moist lower montane forest colonised the muchoya catchment by ca 11 100 yr b p and the ahakagyezi catchment by ca 10 600 yr b p indicating the establishment there of climatic conditions broadly similar to the present pollen data from both mires reveal forest disturbances beginning ca 2200 yr b p this disturbances is likely to have been human induced

tectono climatic signatures during late quaternary in the yunam basin baralacha pass upper lahaul valley india derived from multi proxy records abstract this study provides evidence of the monsoon record over the past 25 ka from the kilang sarai palaeolake which is located in nw himalaya in the rain shadow zone of the indian summer monsoon ism the multi proxy study by using geomorphology carbon isotopes mineral magnetism clay mineralogy and elemental chemistry of a 8 m thick laminated lacustrine sediments indicates that the area experienced fluctuating precipitation conditions during the last 25 ka the time period between 12 and 5 ka bp can be regarded as a very wet interval of the last glacial to mid holocene due to a combined effect of ism and westerlies followed by aridity after 5 ka bp tectonic triggers may have caused the development of terraces and closure of lake at the millennial time scale a correlation of precipitation and vegetational changes between our data and other records from similar geographical settings suggests that kilang sarai basin responded to periods of strengthening in precipitation during the last glacial to early holocene

boulders as a signature of storms on rock coasts this paper is the first review of coastal boulder studies it serves as a peer reviewed introduction to a special issue on the topic of boulders as a signature of storms on rock coasts since 2004 and the indian ocean tsunami most coastal boulder research has been focused on using boulders as sedimentary signatures of palaeo tsunami events and the most commonly used transport equations typically suggest that large boulder deposits are products of tsunami rather than storms there is growing empirical evidence demonstrating on inter annual to century timescales that storm waves are capable of transporting and depositing boulders of significant size at elevations well above sea level current process studies of how boulders are eroded transported and deposited have not received wide attention by rock coast geomorphologists or palaeoenvironmental reconstruction scientists this special issue is framed around the goal of highlighting our current understanding of the role of storm waves as a driving mechanism for boulder erosion transport and deposition here we review the current state of knowledge about boulder dynamics boulder responses to storms and boulders as sedimentary signatures of storm events we identify gaps in our conceptual and quantitative understanding lastly we propose means of addressing research gaps improving consistency between researchers and collecting multi purpose data this review and the papers contained within the special issue provide an improved understanding of coastal dynamics particularly the role storms can play in influencing erosion rates and depositional patterns of coarse material i e boulders or larger which has hitherto been under represented in the literature

progradational gravel beach sequences in a moderate to high energy microtidal marine environment the anatomy of progradational gravel beaches was analysed in two different tectonic settings the strongly subsiding messinian foreland basin of the eastern southern alps and the rising pleistocene marine terraces of the outer margin of the apenninic chain progradation took place near the mouths of fan delta or braid delta distributaries debouching in microtidal landlocked basins palaeo adriatic and palaeo ionian seas a wind wave climate comparable to that of the present day was characterized by periodic intense storm activity most of the beachface progradation is thought to have taken place during the post storm recovery and fair weather stages whereas the impact of storms is mostly recorded by the cutting of erosional surfaces on the beachface and by emplacement of poorly sorted and coarse grained gravels on the shoreface by storm intensified seaward trending flows and behind the highest berms by washover processes analysis of the sequences led to the identification of a number of typical divisions which are differently developed in the two settings compared here the characteristics of the apenninic sequences suggest a strongly variable wind wave climate with periodic changes from a relatively dissipative barred morphology during storms accompanied by strong longshore currents and rip development to a more reflective state typical of recovery and fair weather stages the southern alpine sequences on the other hand are characterized by poor evidence of barred morphology and of longshore currents and widespread effects of shear and gravity sorting in the lower beachface gravels these features indicate a comparatively more reflective average state due to location of beaches along the deeply embayed head of the palaeo adriatic and the very narrow directional width of the incoming wave spectrum which was almost shore normal most of the time in addition to well developed shape zonation of gravels the common presence of wave generated gravel megaripples in the southern alpine sequences indicates the greater influence of long period waves due to the greater available fetch distances in both settings the cyclicity is thought to be genetically related to minor changes of sea level

a 25 000 year record of climate induced changes in lowland vegetation of eastern equatorial africa revealed by the stable carbon isotopic composition of fossil plant leaf waxes the debate of climate versus co2 in controlling the long term dynamics of tropical african vegetation has focused on events at the upper tree line since the relevant paleodata tend to be from mid elevation sites 2000 3000 m less well known is the relative importance of co2 in regulating the dynamics of tropical lowland 1500 m vegetation particularly that of the dry open woodlands bush and grasslands covering much of eastern equatorial africa here we examine the stable carbon isotopic composition of n alkanes in the sediment record of lake challa a lowland crater lake near mt kilimanjaro covering the last 25 000 years the distributions of the n alkanes with dominance of the long chain odd carbon numbered components and their isotopic composition reveal a mixed origin the c23 and c25 n alkanes are depleted in 13c with 13c values between 30 and 50 in shallow lakes these n alkanes are thought to derive from non emergent aquatic plants but this is unlikely in this steep sided crater lake as it lacks a significant littoral habitat the c27 n alkanes are predominantly derived from leaf wax lipids of terrestrial plants brought into the lake predominantly by local soil run off their 13c values in particular that of the n c31 alkane reveal a marked transition in local lowland vegetation from being dominated 70 100 by c4 plants during the glacial period until 16 5 cal kyr bp to a more mixed c3 c4 composition 30 60 c4 during the holocene the start of the late glacial trend towards a greater proportion of c3 plants coincided with the start of increasing monsoon rainfall 1500 years after the onset of the rise in atmospheric co2 and 3500 years after the onset of post glacial warming the transition was interrupted during the dry younger dryas period 13 0 11 7 cal kyr bp when c4 plants again became much more prevalent almost reaching their glacial period abundance notably the principal trend in leaf wax 13c values infers c4 dominance during both wet and dry phases of the glacial period and a mixed c3 c4 vegetation during both wet and dry phases of the holocene our results indicate that long term variation in pco2 exerted important control on the composition of drought adapted savanna vegetation in this currently semi arid lowland region of equatorial east africa

late quaternary vegetation dynamics in a biodiversity hotspot the uluguru mountains of tanzania abstract late quaternary vegetation history and environmental changes in a biodiverse tropical ecosystem are inferred from pollen charcoal and carbon isotope evidence derived from a 48 000 yr sedimentary record from the uluguru mountains a component of the eastern arc mountains of kenya and tanzania results indicate that eastern arc forest composition has remained relatively stable during the past 48 000 yr long term environmental stability of the eastern arc forests has been proposed as a mechanism for the accumulation and persistence of species during glacial periods thus resulting in the diverse forests observed today the pollen and isotope data presented here indicate some marked changes in abundance but no significant loss in moist forest taxa through the last glacial maximum thereby providing support for the long term environmental stability of the eastern arc anthropogenic activities including burning and forest clearance were found to play a moderate role in shaping the mosaic of forest patches and high altitude grasslands that characterise the site today however this influence was tempered by the inaccessibility of the mountain

the kashiru pollen sequence burundi palaeoclimatic implications for the last 40 000 yr b p in tropical africa abstract a continuous pollen record from a central african highland site 3 28 s 29 34 e with 15 radio carbon dates spans at least the last 40 000 yr both modern and fossil pollen have been investigated a clear pattern of changes in vegetation and climate is suggested prior to 30 000 yr b p the occurrence of the montane conifer forest including the upper forest limit indicates climatic conditions colder and drier than now but more humid than in late glacial time between 30 000 and 15 000 yr b p grassland with afroalpine indicators expanded down to 2500 2000 m altitude as a result of dry and most probably cool climate the montane forest persisted in refuges although much reduced forest vegetation with the same floristic composition as today appeared after 13 250 200 yr b p suggesting more humid conditions the occurrence of a possible short term humid episode about 21 500 yr b p is correlated with some high lake level stages in east africa and with organic deposits in deep sea cores from the mediterranean and the atlantic ocean

late pleistocene and holocene history at mubwindi swamp southwest uganda abstract deposits beneath mubwindi swamp provide a partial record of vegetation history since at least 43 000 yr ago we studied pollen from two cores and obtained nine radiocarbon ages from one of these cores and three radiocarbon ages from the other pollen deposited before and soon after the last glacial maximum represents vegetation very different from the modern vegetation of the mubwindi swamp catchment although species now associated with higher altitudes were dominant some elements of moist lower montane forest persisted possibly because of favorable soils or topography the pollen data provides evidence for a late glacial montane forest refuge near mubwindi swamp moist lower montane forest became much more widespread soon after the glacial maximum the only irrefutably holocene sediments from mubwindi swamp date to the past 2500 yr during this time a combination of climatic and human induced changes in vegetation can be seen in the pollen records

lowland forest collapse and early human impacts at the end of the african humid period at lake edward equatorial east africa in africa the early holocene was characterized by wetter warmer conditions than today followed by rapid aridification at 5 2 ka however a lack of lowland vegetation records has prevented a detailed evaluation of forest response to holocene climate change additionally although modern vegetation communities are linked to human disturbance few studies have addressed how prehistoric human activities helped engineer the character of modern african ecosystems understanding the architecture of lowland and highland forests is important to prevent further degradation from climate land use change we present an 11 000 yr fossil pollen record from lake edward uganda we show that guineo congolian forests dominated the highlands and lowlands in equatorial east africa in the early holocene highlighting the importance of rainfall and temperature in controlling forest communities these forests remained until 5 2 ka when the climate became drier the lacustrine ecosystem response to aridification was abrupt however forest decreased gradually replaced by deciduous woodlands woodlands dominated until after an arid period at 2 ka however forest did not recover increased disturbance indicators and grasses suggest that the arrival of iron age people resulted in the modern fire tolerant vegetation although late holocene climate played a role in vegetation opening the modern ecosystem architecture in east africa is linked to early human activities

a late quaternary pollen record from the transvaal bushveld south africa pollen spectra from cores of organic spring deposits from the transvaal provide evidence for the climatic evolution of the province during the last 35 000 yr b p or more the past climatic phases are derived from palynological reconstructions of past vegetation types by comparison of fossil pollen data with modern surface pollen spectra from various localities evidence is provided for an early moist cool phase with relatively mesic bushveld and expanded montane forest in the central transvaal followed by a drier period with drier bushveld which probably lasted until approximately 25 000 yr b p during the next phase which at the latest ended about 11 000 yr b p the temperatures were probably 5 6 c cooler than at present at that time bushveld vegetation in the central transvaal was replaced by open grassland with macchia elements climatic amelioration came and semiarid savanna returned to the plains at first gradually and then developing into a warm kalahari thornveld type vegetation after 6000 yr b p it apparently became slightly wetter and a more broad leafed bushveld developed about 4000 yr b p it again became cooler and slightly wetter and the bushveld vegetation on the central and northern plains was comparable to present open upland types after 2000 yr b p conditions gradually became warner until about 1000 yr b p when the modern climate of the central transvaal bushveld originated

late holocene hydrological history of lake tanganyika east africa from isotopic data on fossil stromatolites abstract lake tanganyika situated in the western branch of the east african rift system shows a slightly positive water budget and generates a small outflow through the lukuga river dependent mainly on the ruzizi river inflow from lake kivu in the northern part of the basin conditions more arid than those presently observed closed the kivu basin from 3800 to 1300 yr b p previous studies esimated that the closure of the corresponding tanganyika basin lowered the lake level by 75 150 m in this paper we present the results of isotopic and morphologic analyses of fossil stromatolites the stromatolites formed as thick incrustations on hard substrates and are found at depths between 6 and 60 m below the modern lake level their isotopic composition 18o 13c 14c very precisely document late holocene water levels and hydrologic fluctuations in the lake tanganyika basin with reference to the actual situation a major low stand at 10 m below present level is identified from 3400 to 1900 yr b p with a rapid recession and gradual rise to modern levels maximum 18o values vs pdb in the stromatolites rose from ca 3 5 at 3400 yr b p to 6 at 2500 yr b p then decreased progressively to 1 6 at 1300 yr b p these values are interpreted as a maximum aridity episode culminating at ca 2500 yr b p at which time a negative precipitation evaporation p e ratio resulted in a much higher residence time of paleolake waters and thus a noticeable enrichment in 18o the observed decoupling of the isotopic ratio 18o 16o and water volume responses is thought to be linked to the inertia of the large rift aquifers which controlled the paleolake level

gravelly shoreface deposits a comparison of modern and ancient facies sequences the morphology and dynamics of modern gravel shorefaces are poorly documented this hinders the interpretation of possible ancient counterparts a comparative study of a modern chesil beach england and an ancient baytree member of the cardium formation alberta gravel shoreface shows that the two systems are very similar close to and above sea level with a high about 1 m gravel plunge step lying below plane bedded sands and gravels of the beachface the shoreface at chesil beach is dominated by asymmetrical gravel wave ripples these are oriented offshore near the toe of the shoreface and onshore in shallower depths this may reflect offshore movement during storms and landward reworking during fair weather the baytree member is over 12 m thick and comprises over 80 conglomerate conglomerate is decimetre bedded massive or cross bedded with sets over 60 cm thick produced by gravel bedforms migrating alongshore it is interbedded with discontinuous cm to dm bedded sandstones which may be cross bedded pebble fabric and cross bed orientation both indicate strong alongshore sediment transport near the base of the section pebble orientations suggest that gravel wave ripples developed below the zone of strong longshore flows differences between these two examples may be attributed to different directions of wave approach

numerical interpretation of a high resolution holocene pollen record from burundi the holocene history of the tropical montane forest is reconstructed using a high resolution pollen record from a valley swamp 3 35 s 29 41 e at 2000 m elevation the post glacial establishment of the montane rain forest is evidenced at ca 10 600 yr b p numerical analysis combines the correspondence analysis with the cluster analysis of both 38 modern and 101 fossil pollen spectra including 125 identified pollen taxa four distinct successionnal stages of forest development have been identified the past vegetation recorded during the early holocene period 10 600 3800 yr b p was more closely related to modern pollen spectra from secondary forest rather than to primary forest samples from burundi at 3800 yr b p a sharp decrease of arboreal pollen percentages and a noticeable increase of celtis a semi decidous tree indicate the opening of montane forest due to a drier climatic event the beginning of the anthropogenic impact evidenced after at 3500 yr b p contemporaneously with the early iron age in burundi follows the late holocene climatic shift

human environment interactions in an agricultural landscape a 1400 yr sediment and pollen record from north pare ne tanzania abstract a sediment and pollen record from the north pare mountains in north eastern tanzania provides evidence for strong anthropogenic landscape transformations since the 7th century ad and demonstrates that shortly after the arrival of early iron age farmers agricultural land use became the main driving force of vegetation and landscape change predominating over external climatic factors the absence of pollen characteristic for the corresponding altitudinal submontane forest implies widespread forest clearance and agriculture land use prior to the onset of the sedimentary record land clearance soil erosion and corresponding accumulation of colluvial slope deposits on the valley floor triggered paludification and the establishment of the lomwe palaeowetland in the 7th century ad accelerated soil erosion and rapid alluvial burial of the palaeowetland between ad 1200 and ad 1500 represent an environmental tipping point with important repercussions for present day land degradation and resource restraints age control is complicated by radiocarbon date reversals and draws on introduced forest taxa cupressus and eucalyptus as biostratigraphic markers of the 20th century geoarchives from agricultural landscapes that are shaped by long term settlement and land use such as the pare mountains can enhance archaeological occupation histories and provide crucial information for both the identification of ecological thresholds and for the reconstruction of environmental transitions during anthropogenic landscape transformations

after the deluge mediterranean stagnation and sapropel formation in an east mediterranean marine core the upper sapropel begins soon after the start of a global event a very heavy precipitation which occurred in the equatorial latitudes during the late glacial early holocene this heavy precipitation in africa channelled by the nile river across 35 of latitude produced a low salinity surface layer in the east mediterranean in this confined basin with high bottom salinity the steep salinity gradient stratified the water column the stagnant bottom waters triggered the sapropel formation cretaceous sapropels in the tropical oceans may result from the same chain of events in warm humid climates with contrasting wet and dry seasonal rhythm

orbital scale vegetation change in africa abstract palynological records of middle and late pleistocene marine sediments off african shores is reviewed in order to reveal long term patterns of vegetation change during climate cycles whether the transport of pollen and spores from the source areas on the continent to the ocean floor is mainly by wind or predominantly by rivers depends on the region despite the differences in transportation accumulation rates in the marine sediments decline exponentially with distance to the shore the marine sediments provide well dated records presenting the vegetation history of the main biomes of western and southern africa the extent of different biomes varied with the climate changes of the glacial interglacial cycle the mediterranean forest area expanded during interglacials the northern saharan desert during glacials and the semi desert area in between during the transitions in the sub saharan mountains ericaceous scrubland spread mainly during glacials and the mountainous forest area often increased during intermediate periods savannahs extended or shifted to lower latitudes during glacials while the representation of the tropical rain forest fluctuated with summer insolation and precession that of the subtropical biomes showed more obliquity variability or followed the pattern of glacial and interglacials

oxygen isotopes in cellulose from modern and quaternary intertropical peatbogs implications for palaeohydrology abstract cellulose 18o values were measured in modern peatbog plants in recent peats and in mountain peatbog cores from burundi in a study of the hydrologic control of the frsol 18o 16o ratio in intertropical peat cellulose modern plants and waters were collected under various altitudes 800 2500 m a s l with mean annual relative humidity ranging from 0 72 to 0 82 the water 18o values i vary between 4 and 2 5 the cellulose water enrichment is of 25 3 0 5 for aquatic plants of 24 6 emergent plant species the scatter in the cellulose 18o values in vary between 4 and 2 5 the cellulose water enrichment is cellulose 18o values of emergent plantss tend to decrease with increasing elevation 0 6 to 0 07 per 100 m and relative humidity 0 5 to 0 1 per mean emergent plant 18o values are approximated within 0 6 by available cellulose 18o models relating cellulose 18o to the relative humidity h and the environmental water 18o except in a large swampy system peats were subsampled in core ka 2 kashiru burundi 3 28 s 29 34 e 890 cm long 2240 m a s l altitude and for control in the topmost 50 cm of core ku 2 kuruyangwe 3 35 s 29 41 e 2020 m a s l altitude similar 18o vaues 26 to 28 5 were found in the topmost 50 cm of both cores they compare well with the mean 18o for modern emergent plants at kashiru ams 14c dating showed that core ka 2 spans the last 30 ka celluloses are mainly derived from emergent plants and yield 18o values ranging from 19 to 29 with the highest values between 2 1 and 0 ka and the lowest values 19 to 23 5 between 6 and 4 5 ka for the period between 6 and 4 5 ka the models yield a decrease in in of 4 to 2 5 relative to present for an h increase of 6 to 11 before 11 7 ka the models yield a in value close to the present value for an h increase of 6

simulated climate and biomes of africa during the late quaternary comparison with pollen and lake status data new compilations of african pollen and lake data are compared with climate ccm1 ncar boulder and vegetation biome 1 2 gsg lund simulations for the last glacial maximum lgm and early to mid holocene emh the simulated lgm climate was ca 4 c colder and drier than present with maximum reduction in precipitation in semi arid regions biome simulations show lowering of montane vegetation belts and expansion of southern xerophytic associations but no change in the distribution of deserts and tropical rain forests the lakes show lgm conditions similar or drier than present throughout northern and tropical africa pollen data indicate lowering of montane vegetation belts the stability of the sahara and a reduction of rain forest the paleoenvironmental data are consistent with the simulated changes in temperature and moisture budgets although they suggest the climate model underestimates equatorial aridity emh simulations show temperatures slightly less than present and increased monsoonal precipitation in the eastern sahara and east africa biome simulations show an upward shift of montane vegetation belts fragmentation of xerophytic vegetation in southern africa and a major northward shift of the southern margin of the eastern sahara the lakes indicate conditions wetter than present across northern africa pollen data show an upward shift of the montane forests the northward shift of the southern margin of the sahara and a major extension of tropical rain forest the lake and pollen data confirm monsoon expansion in eastern africa but the climate model fails to simulate the wet conditions in western africa

sedimentology of rocky shorelines 1 a review of the problem with analytical methods and insights gained from the hulopoe gravel and the modern rocky shoreline of lanai hawaii abstract hypotheses advanced concerning the origin of the pleistocene hulopoe gravel on lanai include mega tsunami abandoned beach multiple event rocky shoreline and for parts of the deposit native hawaiian constructions and degraded lava flow fronts uplift of lanai shorelines has been suggested for deposits occurring up to at least 190 m these conflicting hypotheses highlight problems with the interpretation of coarse gravel deposits containing marine biotic remains the geological records of the processes implied by these hypotheses should look very different discrimination among these or any other hypotheses for the origins of the hulopoe gravel will require careful study of vertical and lateral variations in litho and biofacies facies architecture contact relationships and stratal geometries of this deposit observations of modern rocky shorelines particularly on lanai adjacent to hulopoe gravel outcrops have shown that distinctive coarse gravel facies are present several of which occur in specific geomorphic settings tectonic isostatic and eustatic changes which cause rapid shoreline translations on steep slopes favour preservation of former rocky shorelines and associated sedimentary deposits both above and below sea level the sedimentary record of those shorelines is likely to be complex the modern rocky shoreline sedimentary environment is a hostile one largely neglected by sedimentologists a range of high energy processes characterize these shorelines long period swell tsunami and storm waves can erode hard bedrock and generate coarse gravel they also erode older deposits depositing fresh ones containing mixtures of materials of different ages additional gravelly material may be contributed by rivers draining steep hinterlands to fully evaluate rocky shoreline deposition in the broadest sense for both the hulopoe gravel and other deposits sedimentary facies models are needed for rocky shorelines occurring in a range of settings recognition and description of rocky shoreline deposits are crucial for correctly interpreting the geological history of oceanic and volcanic arc islands for distinguishing between ancient tsunami and storm deposits and for interpreting coarse grained deposits preserved on high energy coasts of continents problems include not only the absence of appropriate sedimentary facies models linking rocky shoreline deposits and environments but also until recently lack of a systematic descriptive scheme applicable to coarse gravel deposits generally two complementary methods serve to integrate the wide range of bed and clast attributes and parameters which characterize complex coarse gravel deposits the composition and fabric caf method has a materials focus providing detailed description of attributes of the constituent clasts petrology the proportions of gravel sand and mud and the ways in which these materials are organized the sedimentary facies model building fmb method emphasizes the organization of a deposit on a bed by bed basis to identify facies and infer depositional processes the systematic use of a comprehensive gravel fabric and petrography log gfpl in conjunction with detailed vertical profiles provides visual representations of a range of deposit characteristics criteria useful for distinguishing sedimentary facies in the hulopoe gravel are grain size modes amount of matrix bed geometry sedimentary structures bed fabric and clast roundness

holocene paleohydrology and glacial history of the central andes using multiproxy lake sediment studies here we document at century to millennial scale the regional changes of precipitation evaporation from the late pleistocene to present with multiproxy methods on a north south transect of lake sites across the eastern cordillera of the central andes the transect of study sites covers the area from v14 s to 20 s and includes core studies from seven lakes and modern calibration water samples from twenty three watersheds analyzed to constrain the down core interpretations of stable isotopes and diatoms we selected lakes in different hydrologic settings spanning a range of sensitivity to changes in the moisture balance these include 1 lakes directly receiving glacial meltwater 2 overflowing lakes in glaciated watersheds 3 overflowing lakes in watersheds without active glaciers and 4 lakes that become closed basins during the dry season the results of our current work on multiple lakes in the bolivian andes show that while the overall pattern of holocene environmental change is consistent within the region conditions were not always stable over centennial to over millennial timescales and considerable decadal to centuryscale climate variability is evident abbott et al quat res 47 1997 70 80 quat res 47 1997 169 180 quat sci rev 19 2000 1801 1820 polissar master s thesis university of massachusetts 1999 comparison of the paleoclimate record from one well studied site lago taypi chaka kkota ltck with others within the region illustrates a consistent overall pattern of aridity from the late glacial through the middle holocene previous work noted a difference between the timing of water level rise in lake titicaca v5 0 3 5 ka b p abbott et al quat res 47 1997 169 180 cross et al holocene 10 2000 21 32 rowe et al clim change 52 2002 175 199 and the onset of wetter conditions at 2 3 ka b p in ltck a lake that drains into the southern end of lake titicaca abbott et al quat res 47 1997 70 80 sedimentary and oxygen isotope evidence from paco cocha 13 54ps located in the northern reaches of the expansive 57 000 km 2 titicaca watershed which spans v14 s to 17 s indicates that

late quaternary climatic changes in the eastern kumaun himalaya india as deduced from multi proxy studies abstract an event of neotectonic activity on an ne sw trending subsidiary fault in the zone of e w running intracrustal boundary thrust south almora thrust in the champawat district of eastern kumaun himalaya resulted in creation of a lake at ca 21 5 bp the lake drained in the late holocene leaving behind a 5 0 m thick sedimentary sequence of mostly black and carbonaceous mud with a minor magnetic reversal between 20 5 and 19 7 ka bp at the base the profile studied by using multi proxies e g carbon isotopes pollen analysis palaeo and mineral magnetism and clay minerals has recorded globally well established abrupt climatic events in the last 20 000 years such as the lgm older dryas od younger dryas yd holocene warming 8 2 ka and 4 2 ka events most events estimated assuming a constant rate of sediment accumulation for similar lithologies may be related to the rapid changes in the local climate and albedo structure the itcz may have played a key role in controlling the behavior of the southwest monsoon from the lgm

crestal overtop and washover sedimentation on a fringing sandy gravel barrier coast carnsore point southeast ireland abstract storm sedimentation on a fringing sandy gravel barrier system in southeast ireland is examined recent wave overtopping and overwashing during severe onshore storms have resulted in a distinctive pattern of crest and backbarrier sedimentation this is not easily matched with available models of washover sedimentation drawn from the barrier islands of the eastern united states beach crest overtopping occurs at heights up to 6 m mhws and is related to the development of upper beach swash ramps that are plastered against storm wave eroded dune scarps located at the barrier crest ramp sediments comprise coarse basal beach gravels overlain by coarsening upward units and finally topped by distinctive seawarddipping fine grit coarse sand couplets in places where ramps reach the dune cre t overtopping swash has deposited a fine marine gravel veneer

chronological potential of palaeomagnetic oscillations recorded in late quaternary sediments from lake tanganyika abstract the measurements of depositional and post depositional remanent magnetizations drm and pdrm in two piston cores collected at water depths of 140 m core mpu3 and 422 m core mpu12 in the southern lake tanganvika mpulungu sub basin zambia provide a palaeomagnetic record for south east central africa which spans over the last 25 5 ka ages on a conventional 14c time scale for the most characteristic inclination peaks were estimated by correlating the palaeomagnetic record with the lake barombi mbo cameroon and the western europe secular variation type curves ams 14c ages on total organic matter tom measured in mpu12 core appear to be 2 to 4 ka older in the lower part of the record from ca 25 to 15 ka bp i e during the last arid episode of the late pleistocene these apparent 14c ages exceed pdrm acquisition lagtimes evaluated to be about 800 years at most and also account for residence time of carbon in tom prior to its sedimentation therefore magnetostratigraphic correlations are believed to provide a better overall chronology for the late pleistocene and early holocene changes in lake tanganyika level major drops shown by breaks of deposition in core mpu3 at 1000 cm and 825 cm sub bottom are respectively dated at ca 21 5 ka bp and between 17 and 15 ka bp

shape evolution and fabric in a boulder beach monument cove maine abstract unequal spacing of nearly vertical joints and sheeting in hornblende granite at monument cove maine forms large tabular blocks which accumulate as talus on the backbeach the blocks are subsequently rounded by wave action to form a pocket boulder and cobble beach measurements of the talus blocks and boulders indicate that the initial structurally controlled bladed and elongate habits are manifested in the boulders however as abrasion progresses more compact spherical and more platy discoidal boulders evolve the data suggest that the greatest change is toward compactness and that the ultimate clast shape at monument cove would be spherical the orientations of the l i planes and the l axes of the rounded clases were also measured the l i planes are well oriented dipping m inly offshore the l axes orientations form three main clusters one subparallel to the shoreline one down the dip of the beach and one oblique to the shoreline the latter two clusters lie within the modal dip of the l i planes

environmental change in montane southwest uganda a pollen record for the holocene from ahakagyezi swamp the environmental history of montane southwest uganda over the last c 12 300 years is described using data from a 22 84 m long core of sediment from ahakagyezi swamp rukiga highlands these data include plant microfossils and macrofossils charcoal and nine radiocarbon dates according to evidence from plant fossils and radiocarbon dates vegetation in the ahakagyezi catchment was very different to the expected climax today until c 10500 bp the surface of the swamp was dominated by sedges whilst the adjacent hillsides were largely devoid of trees changes in pollen suggest that a form of dry montane scrub was replaced by moist lower montane forest from c 11000bp subsequent fluctuations in pollen indicate that once established the composition of moist lower montane forest varied during the holocene and that unreversed forest reduction commenced in the ahakagyezi catchment at c 800 bp on the surface of the swamp itself syzygium dominated swamp forest increased in extent from c 5800 bp and mor

orientation of cobble and boulder beach clasts abstract this study of cobble and boulder sized clast orientations in pocket beaches indicates that the l i planes dip seaward at angles steeper than the foreshore slope and that the modal dip direction is generally not perpendicular to the shoreline trend l axes are oriented parallel perpendicular and at about 45 to the beach trend shoreline trends based on orientation data may be estimated incorrectly by as much as 30 because of wave refraction

climate of east africa 6000 14c yr b p as inferred from pollen data this paper presents a spatial reconstruction of climate in east africa at 6000 14c yr b p two different approaches using pollen data have been used the standard best modern analogues method and the new plant functional type method based on groups of pollen taxa both methods have been applied to 32 fossil pollen spectra dated at 6000 14c yr b p for each site we have estimated two climatic parameters annual precipitation and mean annual temperature three bioclimatic parameters ratio of actual to potential evapotranspiration and the mean temperature of the coldest and warmest months results show that the temperature lapse rate was less steep at 6000 14c yr b p than it is today the climate was wetter north of 3 s precipitation anomalies 50 mm yr and slightly drier farther south precipitation anomalies 50 mm yr the ratio of actual to potential evapotranspiration also indicates conditions similar to or wetter than today north of 3 s anomalies 10 the climate was warmer than today by 2 c north of the equator and was cooler southward 1 c although both methods indicate similar climatic patterns the plant functional type method provides more consistent results

pollen evidence of late quaternary vegetation and inferred climate changes in congo a detailed palynological analysis of two cores recovered from a swamp in the southern bateke plateaux congo provides information on the botanical history of this region during the last 24 000 yr b p rich and well diversified pollen counts exhibit changes in the vegetational communities related to hydrological and climatic fluctuations around 24 000 yr b p the occurrence of hydromorphous forest elements gives evidence of a humid phase between 24 000 and around 13 000 yr b p swampy herbaceous communities expanded indicating slightly drier climatic conditions from approximately 13 000 yr b p onward the beginning of a humid episode is reflected by the development of mesophilous forests the decrease of these forests is documented since 3000 yr b p grasslands are found to extend locally whereas elaies guineensis oil palm spreads out indicating both climatic change but also anthropogenic activities

palaeoclimatic conditions in the late pleistocene wadda lake eastern kumaun himalaya india abstract an episode of neotectonic activity on an east west trending fault in the zone of active intracrustal north almora thrust in the eastern kumaun himalaya resulted in the formation of a lake around 36 000 yr b p a 13 m continuous sequence made up largely of carbonaceous mud represents the lake that disappeared around 10 000 yr b p due to the revival of neotectonic activity on the basis of radiocarbon dating it appears that the rate of sedimentation varied from time to time during the existence of the lake palaeomagnetic studies show normal polarity except for a major deviation in the upper part of the section palynological investigations testify to the occurrence of three temperate humid and at least two well defined arid climatic phases which are correlated with previously documented late quaternary climatic changes as recorded in the himalaya as well as in tibet around 10 000 yr b p widespread deposition of a tectonically induced debris flow occurred in the lake basin at the terminal stage of the lake s life the two events ca 36 000 and 10 000 yr b p thus seem to represent two major neotectonic events in the kumaun lesser himalaya

farmers smelters and caravans two thousand years of land use and soil erosion in north pare ne tanzania abstract slope deposits in north pare provide evidence of two millennia of anthropogenically driven land clearance soil erosion and land degradation drawing on deposit stratigraphy soil magnetic parameters stable carbon isotope composition and radiocarbon dating three phases of soil erosion are distinguished characterized by distinct surface processes and increasing levels of agricultural land use onset of slope deposit formation in pare since about 300 bc documents soil erosion as an immediate consequence of new land use practices associated with the spread of agriculture and iron working across northern tanzania by ad 500 slope deposits extended into valley bottoms and to middle slopes suggesting catchment wide land clearance and soil erosion in the 15th century ad progressive anthropogenic soil erosion had exhausted the topsoil resource and material changes of the slope deposits reflect widespread subsoil erosion the exposure of subsoils represents an ecological tipping point and triggered the transition to a new morphodynamic framework dominated by runoff based erosion processes that are recorded as sand lenses and sand layers the most recent deposits show ongoing accelerated erosion and severe land degradation whilst cessation of sand lens preservation indicates pre colonial intensification of agricultural land use land use changes and socioeconomic transitions associated with the establishment of the ugweno chiefdom and the 19th century caravan trade are discussed as possible responses to imperceptible long term land degradation in pare the study demonstrates that anthropogenic soil erosion and not external climatic drivers shaped landscape development in pare and shows that the identification of environmental thresholds is essential for the assessment of resilience in human dominated ecosystems

desert paleoenvironmental data from cave speleothems with examples from the chihuahuan somali chalbi and kalahari deserts abstract pollen bearing lake bog and spring sediments are relatively scarce in many arid and semiarid regions of the world and few are dateable beyond the 14c range we have obtained pollen spectra from speleothems collected from caves in the somali chalbi and kalahari deserts suggesting that these deposits may be an important future source of desert paleovegetation data as cave speleothems can be dated by the 230th 234u method to c 350 000 yr b p and by the tl and esr methods potentially to 1 m y b p and can sometimes give paleotemperature and paleohydrologic data they could provide a first glimpse of desert paleoenvironments during isotope stages 4 9 ages of speleothems from the chihuahuan kalahari and somali chalbi deserts suggest that there was more available moisture in the southwestern u s a and in northwestern bostwana during glacials and interstadials of the last c 300 000 years but that wetter conditions in the horn of africa corresponded with interglacials and perhaps to a lesser extent with interstadials pollen from three northern somalia speleothems indicate more mesic conditions in the horn of africa at 10 000 11 800 and 176 500 yr b p while speleothem pollen spectra from matupi cave in northeastern zaire presently surrounded by tropical rainforest suggest a savanna grassland at this cave c 14 000 yr b p