eolian depositional phases during the past 50 ka and inferred climate variability for the pampean sand sea western pampas argentina abstract the pampean sand sea which occurs from the argentinian pampas to the eastern andean piedmont hosts presently stabilized dune fields spanning the late quaternary this study integrates previous results and presents new geomorphic stratigraphic sedimentological and chronologic data for nineteen 2 m thick eolian successions for the san luis paleo dune field western pampas to better constrain the depositional history six eolian depositional phases are identified spanning the past 50 ka interposed with paleosols and or bounded by erosive surfaces age control was from 61 osl ages of small aliquots of quartz grains from eolian stratigraphic units the inferred timing of eolian phases are at ca 70 10 yr 190 20 yr 12 to 1 ka 22 to 17 ka 29 to 24 ka and 40 to 32 ka a maximum span for periods of pedogenesis at ca 12 to 17 ka 22 to 24 ka and 29 to 32 ka was provided by bounding osl ages which broadly overlap with high stands of pluvial lakes and glacier advances in the central andes we infer that the added precipitation may reflect expansion of the southern hemisphere monsoon associated with northern hemisphere heinrich events leading to episodes of significantly wetter conditions 350 mm map to at least 35 s most of the holocene 12 ka to 0 8 ka was characterized by sand sheet deposit under drier than present conditions 100 450 mm map associated with monte type vegetation shrub steppe the latest two eolian depositional phases occurred at ca 190 and 70 yr ago during the historic period with european settlement and are related to anthropogenic landscape disturbance though the youngest phase was concomitant with 1930s drought wet conditions dominated since ca ad 1970 with new lakes and rivers forming across this eolian terrain an incongruous environmental response in reference to drier conditions for most of the holocene

micromorphology of the lower pleistocene loess in the iranian loess plateau and its paleoclimatic implications abstract the loess deposits in iran are a valuable archive of regional paleoclimatic and paleoenvironmental information extensive sedimentological and chronological studies have been carried out on the middle to upper pleistocene loess successions during the past decades but there is an absence of comparable research in the older loess deposits recently a 19 m thick loess paleosol sequence was discovered in the central iranian loess plateau ilp which was paleomagnetically dated to 2 4 1 8 ma and thus represents by far the oldest loess known in northern iran here we present the results of a detailed micromorphological investigation of these lower pleistocene loess paleosol sequences red sequence from the ilp our main findings are as follows 1 the agh band red sequence deposits are an extremely thick soil complex comprising paleosols in different stages of development 2 the micromorphological index of soil development miseca suggests that the moderately and well developed paleosols in the red sequence formed in an environment with mean annual precipitation ranging from around 450 to 650 mm respectively and 3 miseca suggests that the red sequence formed under a semi arid to sub humid climate and thus under wetter and more favorable conditions than the overlying late pleistocene loess and modern soils

pedogenic modification of loess significance for palaeoclimatic reconstructions abstract this review considers the role of pedogenic processes in modifying wind blown dust loess concentrating particularly on the ways that resulting properties may be interpreted as indicators of past climatic conditions and changes emphasis is placed on the sequences of palaeosols developed within loess deposits that are frequently regarded as some of the best terrestrial equivalents of marine sediment records of long term global climatic change a palaeosol is generally interpreted in terms of the broad pedogenic processes and environments assumed to be currently responsible for that type of soil forming at the present surface even the very presence of a palaeosol may have palaeoclimatic significance however in that it is often taken to indicate a period of relative land surface stability and warmer and or moister conditions between cold and or arid phases of loess accumulation in reality it may be more useful to consider many loess palaeosol sequences in terms of changing balances between pedogenesis and loess accumulation over geological time in most regions it seems that the balance swings towards pedogenesis during interglacials or interstadials when sediment supply and transport are limited and the climate is warmer and or wetter where accumulation rates are still appreciable during these soil forming intervals however the soils and palaeosols may be accretionary with surface build up keeping pace with pedogenesis welding may also occur where covering sediments are insufficiently thick to isolate an underlying palaeosol from the effects of pedogenesis active at a new land surface further complications occur due to reworking of palaeosols and syndepositional pedogenic alteration of loess units generally such pedocomplexes can only be deciphered if the different pedogenic geomorphic and sedimentary processes are identified and ordered within a pedosedimentary reconstruction a recent trend has been to treat some loess palaeosol sequences as quasi continuous time series particularly when comparing depth functions of climatic proxy properties such as magnetic susceptibility and grain size with marine and ice core isotope curves

sedimentological maps of the typical loessic units in north pampa argentina abstract application of grain size data allowed the construction of maps of two typical loessic formations of north pampa a sand sea covering the central argentine plain and a peripheral loess belt to the northeast compose the pampean aeolian system a region of 20 000 km 2 in the loess belt santa fe and cordoba provinces was studied thick loess outcrops are located in this region the tezanos pinto loess upper pleistocene lower holocene in age and the san guillermo fm late holocene in age are analysed in this article the silt content has been taken as the main parameter for mapping in general the pattern of the isoplethic curves is similar in both maps these maps show that the silt content in both loessic units progressively increases from ssw to nne in the loess belt the silt content increases from 55 to 60 in the ssw at the transition belt to the sand sea up to 75 80 in the nne along a distance of 120 200 km other sedimentological data of the outcropping loess paleosols sequences are presented as complementary information

late quaternary paleosols stratigraphy and landscape evolution in the northern pampa argentina the field properties micromorphology grain size geochemistry and optically stimulated luminescence osl ages of two late quaternary sections have been used to reconstruct the sequence of pedosedimentary processes and to provide insights into landscape evolution in part of the northern pampa of argentina paleosols developed in paludal sediments adjacent to the parana river at baradero and in loess at lozada can both be correlated and linked to other sites thus enabling for the first time the tentative recognition and tracing of a diachronous soil stratigraphic unit that probably spans the equivalent of at least part of marine oxygen isotope stage ois 5 the paleosol at lozada was truncated and buried beneath fluvial sediments during the time span of ois 4 and 3 eolian gradually replaced paludal inputs at baradero over this period and there were also two clearly defined breaks in sedimentation and development of paleosols the period corresponding to ois 2 was marked by significant loess accumulation at both sites with accretion continuing into the mid holocene only at lozada the more developed nature of the surface soil at baradero probably reflects a combination of a moister climate and a longer soil forming interval

a cratonic middle jurassic paleopole callovian oxfordian stillstand j 2 cusp rotation of the colorado plateau and jurassic north american apparent polar wander 1 paleomagnetic results have been obtained from two sequences of the upper middle jurassic upper callovian summerville formation which are located on the north american craton north central new mexico the thicker of the two sections trujillo exhibits a well defined dual polarity remanence forming a magnetostratigraphy of at least 12 relatively short polarity intervals the high reversal frequency is consistent with that recorded by the oceanic crust at this time the second section romeroville is thin gypsiferous and poorly indurated consequently only a short interval 5 m was successfully sampled the characteristic magnetization was wholly normal polarity in the rapid reversals of the thicker section that thickness of normal polarity is unique and thus forms the basis of magnetostratigraphic correlation between the two sections a cratonic late middle jurassic paleomagnetic pole at 148 2 e 57 3 n k 30 3 95 6 0 was obtained from the larger trujillo sequence despite large confidence limits the small sample population of the romeroville sequence displayed the same pole throughout the western united states the summerville formation is overlain with little or no discordance by the morrison formation although the two stratigraphic units are commonly reported to be separated by an unconformity designated j 5 the new mexico paleopoles of the summerville and overlying lower morrison formations are statistically identical at the 95 confidence level a similar situation exists between summerville and lower morrison paleopoles of the colorado plateau the presence of the same geomagnetic field direction in both the summerville and the lower morrison formations suggests that the j 5 unconformity which separates them may encompass little time perhaps representing only a minor break in deposition the two newly investigated summerville sites are located east of the rio grande rift hence representative of the north american craton their paleopoles are displaced counterclockwise relative to those of the colorado plateau and in amounts consistent with other coeval craton colorado plateau pole pairs together six coeval paleopoles indicate that the colorado plateau has rotated clockwise by about 9 0 3 since late pennsylvanian time the cratonic summerville paleopole also removes the uncertainty over the jurassic north american apparent polar wander path the statistically identical summerville and lower morrison paleopoles form a substantial data set five paleopoles which indicate that na apw traced a path roughly along 60 latitude the five paleopoles stand in stark contrast to the paleopole from the slightly older 5 8 ma moat volcanics spreading rates in the central atlantic do not allow na plate motion that would include both paleopoles positions because the weight of the data five paleopoles from widely spaced localities and different tectonic blocks the moat volcanics pole cannot be representative of north america in the middle jurassic

true tracks undertracks and eroded tracks experimental work with tetrapod tracks in laboratory and field abstract to be able to distinguish between true tracks undertracks and tracks altered by erosion is of great importance in tetrapod track ichnotaxonomy this paper reports three experimental approaches to the study of undertracks using the footprints of an emu dromaius novaehollandiae experiment 1 describes successive horizontal sections down through a plaster cast of an emu footprint emplaced in soft mud revealing a steady downward decrease in the area of the track particularly the length this is the result of the movements of the trackmaking limb during impact forward swing of the body and final kick off experiments 2 and 3 describe vertical sections cut through footprints emplaced in packages of layered coloured cement admixed with water to produce different consistencies firm and semi fluid after hardening the cement block was serial sectioned vertically and removal of a lightly cemented layer gave access to two undertrack bedding plane views successive undertracks downward show an increase in horizontal dimensions and decrease in vertical topography of the structure representing gradual degradation of the track anatomy with depth in experiment 3 the true track at the tracking surface was deformed by collapse and flow of the substrate after withdrawal of the foot in this case the undertracks that were formed in layers subjacent to the foot reproduced the morphology of the foot more faithfully than did the true track

tropical westerlies over pangaean sand seas cross equatorial westerly winds are key features of tropical circulation in monsoonal regions although prominent in numerical climate models of pangaea the supercontinent straddling earth s equator late palaeozoic to early mesozoic such flow has not been confirmed previously by migration directions of ancient dunes wind blown sandstones that span 100 million years of earth history are widely exposed in south western usa if recent palaeomagnetic data from the colorado plateau are used to correct mesozoic palaeogeographic maps the plateau is placed about 10 further south than previously assumed and the prevailing north westerly surface winds recorded by dune deposited sandstones are explicable as cross equatorial westerlies the hallmark of modern monsoon circulation permian to early jurassic dunes were driven by north westerlies produced by a steep pressure gradient spanning the supercontinent during december january february although winds are light in most modern near equatorial settings the east african jet accounts for more than half the cross equatorial flow in june july august the thicknesses of annual depositional cycles within the navajo sandstone indicate that the near equatorial north westerly winds that drove these particular dunes were stronger than the modern east african jet the early jurassic dunes that deposited the thick cycles were positioned west of the dominant southern hemisphere thermal low and against highlands to the west a setting very similar to the east african jet the mountains along the western coast of pangaea not only enhanced wind strength but also cast a rain shadow that allowed active dunes to extend very close to the palaeoequator

chronology of late pleistocene pampa loess from the cordoba area in argentina in argentina loess palaeosol sequences were studied from the two sections at monte ralo and corralito located near to the city of cordoba in the east of the pampean ranges infrared optically stimulated luminescence irsl and thermoluminescence tl dating techniques were applied to set up a more reliable chronological framework for the upper pleistocene loess record irsl ages increase with depth and are stratigraphically consistent the oldest loess exposed correlates at least to the penultimate glaciation the luminescence dating study gives evidence for humid climate conditions with soil formation during the last interglacial period and the middle pleniglacial correlating to marine isotope stage mis 5 and 3 respectively three extended periods of soil formation are recorded in the loess palaeosol sequences at the corralito section these buried soils most likely correlate with the last interglacial and early last glacial period during the middle pleniglacial two palaeosols are intercalated in the loess successions in the cordoba area the periods of increased loess accumulation and deposition of loessic sediments correlate with more arid and glacial periods during the early pleniglacial the middle pleniglacial and the late glacial copyright 2009 john wiley sons ltd

a review of late quaternary inland dune systems of south america east of the andes abstract inland dune systems of south america occur in a variety of environmental settings under different climatic conditions from humid subhumid to semiarid arid this contribution provides the state of the art on dune research of inland systems east of the andes tropical northern 10 n 10 s including the dune fields of llanos del orinoco and the amazonian basin are mainly formed from parabolic blowout or deflation basins and linear dunes developed on river floodplains aeolian activity was reported to occur near the late pleistocene holocene boundary in llanos del orinoco over the last 17 ka in the branco river basin and 32 6 ka in the negro river basin both in the amazonian region in general the attributed aeolian origin is controversial the morphology difficult to determine and the chronology still extremely limited and rather debatable in some cases the southern tropical region 10 s 22 s includes aeolian systems situated across the extensive lowlands of the gran chaco and those located in fluvial basins related to the cratonic brazilian shield sao francisco river pantanal and mato grosso the oldest barchanoid barchan ridges at the gran chaco were dated 36 33 ka and subsequent aeolian sand accumulation occurred at 18 ka 14 12 ka 10 9 ka and mid to late holocene times parabolic dunes at the sao francisco river floodplain show an oldest episode generated between 28 and 11 ka followed by eolian activity during the early to mid holocene no chronological data is available for the linear and lunette dunes described at the pantanal linear ridges were distinguished in the upper parana river mato grosso with associated sand accumulation at different intervals of the holocene the last reviewed region is the andean piedmont and western pampas at subtropical eastern south america comprising a large variety of dune morphologies barchan barchanoid linear parabolic transverse and lunette dunes deflation basins and sand sheets luminescence ages suggest the occurrence of aeolian activity intervals during late glacial times and the holocene the general understanding on the dynamic of south american dune systems is hampered by the paucity of chronological information and the representativeness of some dune records whether they reflect local or regional environmental conditions is still a matter of discussion in several areas that need further studies

paleoenvironmental reconstruction of quaternary valley fill successions in summit paleosurfaces of southern sierras pampeanas cordoba province argentina abstract climatic and environmental changes were inferred from the study of late quaternary sequences that represent paleo valleys filling in the summit pampas at the center south of the sierra de comechingones cordoba province argentina a representative sedimentological section p1 was described and sampled and sediments age 14 c granulometric characteristics and organic matter content were determined in the analyzed succession four main stratigraphic units were recognized and interpreted the stratigraphic and pedological characteristics diatom levels presence geomorphological features and altitude conditions of the study area allow us to conclude that 1 valley fill deposits are holocene from 8310 110 yr bp to present days and composed exclusively of loessic loessoid material from surrounding areas 2 the dominant transport mechanism could have been laminar and or hyperconcentrated flows mainly associated with slope evolution processes sheet flow and high density flows 3 isolated swamps with important biological activity were the dominated environments in to the valleys these environments suggest an alternating pedogenic cycles were the most important was the middle late holocene indicating a landscape stabilization tendency 4330 130 yr bp 4 temperate wet climatic conditions and high seasonality characterized middle early holocene hypsithermal period more arid conditions dominated late holocene from 1500 to 1000 bp to the present temperate wet climatic conditions occurred and this period was interrupted by the little ice age 5 in the mountains both in wet and dry periods the rainfalls were probably higher as well as the temperature must be lower than the surrounding plain especially in winters perhaps reaching periglacial conditions during more arid periods

geomorphology and chronology of late quaternary dune fields of western argentina abstract stabilized dune fields are common in western argentina and potentially reflect drought variability in the late quaternary this study focussed on deciphering geomorphic and stratigraphic record of three vegetated dune fields from east to west san luis medanos negros and medanos grandes with a mean annual precipitation from 700 to 91 mm optically stimulated luminescence single aliquot regeneration protocols yield ages on eolian quartz grains constraining depositional events the san luis dune field the wettest area exhibits evidence for repeated activation during the last glaciation ca 33 20 ka generally coincident with regional loess deposition these dunes were locally reformed in the past 100 years which is apparently coincident with intensified agrarian use and drying in the late 19th and early 20th century the two driest and western most dune fields medanos negros and medanos grandes show reactivation at ca 2 5 ka 0 9 and 0 5 ka and ca 4 3 4 2 1 and 0 6 0 4 ka respectively eolian depositional events at ca 2 5 2 1 ka and 0 6 0 4 ka may be coeval for medanos grandes and negros dune fields sustained drought conditions conducive for eolian activity is associated with warmer sea surface temperatures in the south atlantic a weakened south american convergent zone and a dispersed and southeasterly flow of tropical moisture from the low level chaco jet this nascent analysis indicates drought variability beyond historic observations with potentially at least four dune reactivation events in the past ca 4 5 ka

revisiting the chronology and environmental conditions for the accretion of late pleistocene early holocene pampean loess argentina abstract the present research work reviews the age models of three previously studied loess sections across 700 km in the loess belt of the pampean region in central argentina the loess sections were investigated for the first time through high resolution luminescence dating in order to determine the chronology of the loess deposits and its temporal correlation with important palaeoclimatic records of the southern hemisphere reliable estimations of mass accumulation rates mars for loess were used to infer the temporal dust flux variation during the last glacial interglacial transition in southern south america the new age models have significant differences compared to the previously published ones of likely last glacial maximum lgm ages the three studied sections showed general bimodal grain size distributions consistent with multiple sources contributing dust to the pampas it is observed that higher mars values are associated with an increased presence of finer loess increases in loess accumulation are coeval with climatic transitions from wetter to drier periods in the puna altiplano plateau and high mars are related to synchronous climatic shifts to humid conditions in the pampean plain contrasting with dust fluxes observed in the more distal palaeoarchives i e the south atlantic ocean and the antarctic ice sheet the new data suggest increased dust accumulation in the pampas during the antarctic cold reversal acr and the holocene this supports the idea that changes related to atmospheric transport efficiency can better explain dust flux variations observed over glacial interglacial periods in distant palaeoarchives

micromorphological study of irrigation canal sediments landscape evolution and hydraulic management in the middle gila river valley phoenix basin arizona during the hohokam occupation the hohokam were a long lived 300 1450 ad agrarian society in the deserts of southern arizona with an efficient irrigation system and a complex socio political organization dependent on environmental conditions they coped with hydrological and geomorphic changes which potentially had an impact on their cultural evolution irrigation canals were regularly maintained and or abandoned and their fills record secondary signatures of fluvial dynamics landscape change and land use micromorphological studies allow for the creation of a typology of canal fills based on semi quantitative measurements a synchronous and diachronic analysis of canal systems can then be undertaken by means of pedosedimentary correlation as part of cultural resource management projects on the gila river indian reservation south of phoenix studies have been conducted on the prehistoric santan irrigation system in use from the 10th to the 15th century ad phases of low flow were identified followed by alluvial fan flooding and seasonal deposition between the 10th 14th century ad sedentary early classic period during the 14th 15th century ad late classic period evidence of active erosion is initially recorded in the sediments followed by seasonal water supply and ultimately canal abandonment despite probable efficient irrigation

full glacial paleosols in perennially frozen loess sequences klondike goldfields yukon territory canada perennially frozen loess deposits in the klondike goldfields include paleosols formed in full glacial environments correlated by alaskan distal tephra with marine isotope stages mis 2 and 4 patterns of organic and inorganic carbon and clay distribution microstructures and profile morphologies indicate that soil formation occurred in a base rich environment in which organic matter accreted predominantly as root detritus at sites approximately 20 km apart the expression of cryoturbation and ice wedge development decreases in strength upward in loess paleosol sequences correlated with mis 4 suggesting increasing aridity configurations of cryoturbation features and ice wedge thaw unconformities the presence of numerous ground squirrel burrows and an absence of peat accumulation suggest that these substrates were predominantly welldrained with active layers of equal or greater thickness than in modern soils on similar sites in the west central yukon some characteristics of these paleosols are similar to those of modern steppe and tundra soils consistent with plant macrofossil evidence for local ecological diversity during full glacial conditions in eastern beringia

first cosmogenic ages for glacial deposits from the plata range 33 s new inferences for quaternary landscape evolution in the central andes this paper presents the first numerical cosmogenic ages of glacial deposits from the eastern slope of the plata peak 6000 in the arid central andes 32 s the moraines are distributed along three different valleys vallecitos angostura and las mulas in the first only one moraine was identified and no blocks could be sampled for dating the other two have evidence of two glacial advances angostura i and angostura ii the advances loma de los morteritos i and ii were recognised in the las mulas valley in both cases first and second advances are preserved at a similar altitude surface boulders on the top of moraines were sampled for be10 obtained ages are all similar and late pleistocene in age they fit very well with local stratigraphy and regional paleoclimate evidence the loma de los morteritos moraine ii located at 3000 masl dated to 25 000 years ages of 8 000 and 12 000 years were found for the angostura ii deposit 3300 masl an age was obtained for the outwash deposit identified along the el salto valley 69 000 years associated with a late pleistocene drift quantitative datings presented here improve knowledge about the glacial chronology of the plata range and quaternary stratigraphy of the central andes even though they represent a maximum age for these glacial advances new findings support the occurrence of two late pleistocene glacial advances and an older one in the blanco river valley adjusted ages around 8 000 and 25 000 years for younger stage could be evidence of the last glacial maximum lgm period for this region

vertebrate track bed stratigraphy at new megatrack sites in the upper wellenkalk member and orbicularis member muschelkalk middle triassic in carbonate tidal flat environments of the western germanic basin this article examines the high resolution track horizon and track bed stratigraphy at two new middle triassic megatrack sites in nw germany the first megatrack site consists of the localities hagen and detmold and spans over a distance of about 30 km in the upper wellenkalk member of the uppermost lower muschelkalk pelsonian the second megatrack site was found between niederlistingen and ostheim over a distance of 10 km in the orbicularis member of the lowermost middle muschelkalk illyrian at all track sites the track beds are mud cracked microbial laminates and yellow dolomites products of microbial mats in carbonate tidal flat environments vertebrate tracks rhynchosauroides tirolicus abel procolophonichnium haarmuehlensis holst smit veenstra as well as scratch marks and undichna isp are abundant recently 11 track beds have become known from the upper roet member upper bunter to the marl dolomite member middle muschelkalk in the germanic basin six of these track beds build megatrack sites with an extent of 10 400 km the result is a completely different picture of the bathymetry during bithynian to illyrian in the germanic basin a flatter basin with a surrounding carbonate tidal flat belt changing its position periodically

the pedosedimentary evolution and chronology of tortugas a late quaternary type site of the northern pampa argentina new micromorphological magnetic susceptibility geochemical and geochronological data have been collected from tortugas a key late quaternary type site of the northern pampa argentina thus enabling the detailed reconstruction of the pedogenic and sedimentary history of this loess paleosol sequence paleosols developed in the ceres formation and the overlying lower member of the tezanos pinto formation retain evidence for leaching bioturbation and particularly clay translocation processes being dominant both paleosols are truncated evidence for water sorting and sediment reworking as well as continued bioturbation and redistribution of carbonates suggests that intervening depositional phases were complex the previously recorded hypsithermal soil developed in the upper member of the tezanos pinto formation has similar characteristics to the buried paleosols yet does not appear to have been truncated at this site and is only covered by a thin layer of sediment san guillermo formation this latter unit has been pedogenically welded onto the hypsithermal soil thus creating the present day surface soil complex a series of optically stimulated luminescence dates from throughout the sequence provide a stratigraphically consistent chronological framework ca 1 150 ka for the pedosedimentary reconstruction yet conflict with the previously reported thermoluminescence based chronology for the site and region ca 1 90 ka

analysis of the interaction between neotectonic and surface processes in a low land intracratonic setting of south america abstract the quaternary sedimentary record in the continental interiors has generally been studied taking into consideration the climatic forcing however episodes of uplift controlling the development of landforms have often been dismissed the interiors of continents are typically considered to have low deformation rates lower than the rates of exogenous processes deformation in the middle of the pampean plains an intracratonic setting of south america has been observed to have generated an elevated area surrounded by lowland plains this elevated area is susceptible to fluvial erosion from this fact we developed a geomorphologic modelling constrained from geomorphic markers in order to estimate the relative incidence of the different factors that control erosion in lowland landscapes an adapted erosion code was employed which combines fluvial incision equation the stream power law an uplift function spatially distributed and the hillslope diffusion equation a low dem was achieved for restoring an initial non deformed topography affected by low fluvial incision it represents a palaeosurface chrono stratigraphically constrained the estimation of the model parameters was achieved by applying the inversion method the best fit between the numerical solution calculated topography and the measured topography simulated by means a dem was approached by comparison of the stream longitudinal profiles the yield numerical approach suggests that a geomorphological modelling based on the stream power law is possible to be applied in low land landscapes for this a large scale change of the magnitude of the processes modelling the landscape should be expected in comparison with mountain erosional environments remarkably low k empirical values k 5 10 6 6 10 6 yr 1 suggest that the extremely low slopes exert a larger influence on the stream power in low land landscapes also the diffusion coefficient d values resulted largely lower 3 10 4 1 9 10 3 cm 2 yr than presented in tectonically active landscapes 0 03 cm 2 yr regional uplift rates can be higher 0 35 mm yr than it is generally expected in low uplift rate settings 0 1 0 25 mm yr these estimations evidence highly dynamic surface and tectonic processes controlling the landscape evolution over intermediate time scales in an intracratonic setting

three dimensional preservation of foot movements in triassic theropod dinosaurs dinosaur footprints have been used extensively as biostratigraphic markers environmental indicators measures of faunal diversity and evidence of group behaviour1 2 3 4 trackways have also been used to estimate locomotor posture gait and speed6 7 8 9 10 11 but most prints being shallow impressions of a foot s plantar surface provide little evidence of the details of limb excursion here we describe late triassic trackways from east greenland made by theropods walking on substrates of different consistency and sinking to variable depths that preserve three dimensional records of foot movement triassic theropod prints share many features with those of ground dwelling birds but also demonstrate significant functional differences in position of the hallux digit i foot posture and hindlimb excursion

pedogenesis in a pleistocene fluvial system of the northern pantanal brazil sedimentology and hydrology seem to play a predominant role in soil formation in the pantanal since the fluvial systems of this wetland provided quaternary sediments and shaped the landscape however pedogenic processes are active in this region mainly due to the floods that occur during the summer and fall season the goal of this work was to study the pedogenesis in a representative transect on the sao lourenco fluvial fan which has an area of about 16 000 km2 and is one of the largest sedimentary compartments of the northern pantanal west central brazil a transect of 125 m was studied in the late pleistocene sedimentary lobe of the fluvial fan where four landform elements were identified paleo channel paleo levee paleo floodplain and mound and described to show the soil horizon boundaries along the landform unit samples were collected from trenches auger holes and boreholes and were analyzed for soil description and characterization soil analyses carried out were macro and micromorphological physical chemical mineralogical c isotope fractionation and osl dating analyses the set of evidence shows that the studied transect originated from pleistocene sediments due to the activity of the sao lourenco fluvial fan the following soil landform element relationships developed quartzipsamments in the paleo channel plinthaquults in the paleo levee and paleo floodplain and natrustalfs in the mound evidences of pedogenic processes in the transect are a clay eluviation and illuviation resulting in formation of the bt horizon in the soils at the lower part of the transect and mound b gleization and plinthization mainly at the lower part of the transect resulting in formation of mottles reduced soil matrix and nodules plinthite and petroplinthite c bioturbation responsible for addition of materials at the soil surface assisting in the formation maintenance of the mound and d the sodium concentration observed in soils that have higher clay contents which are highest in the mound has the highest levels

pedosedimentary reconstruction of a thick loess paleosol sequence near lanzhou in north central china abstract a 38 m well section near lanzhou at the semiarid western margin of the loess plateau china contained a continuous high resolution loess paleosol sequence spanning the last 130 000 yr depth functions of micromorphological features magnetic susceptibility calcium carbonate organic carbon and median grain size provide the basis for pedosedimentary and associated paleoenvironmental reconstructions of three paleosol complexes s1 sm and s0 each pedosedimentary stage reflects the interaction of changing intensities of controlling monsoonal forces three periods of reduced dust inputs and enhanced pedogenic activity notably bioturbation and weak leaching can be identified from within the s1 pedocomplex these soil forming intervals were separated by phases of varying land surface instability characterized by arid dust deposition semiarid accretionary pedogenesis water reworking and crust formation or even freeze thaw modification the sm pedocomplex represents an interval of relatively rapid dust accumulation with only minimal syndepositional modification and minor pedogenic alteration at ephemeral land surfaces the s0 pedocomplex is clearly more pedogenically developed although erosion reworking and mixing by water have partly homogenized the property depth functions

preservation and erosion of theropod tracks in eolian deposits examples from the middle jurassic entrada sandstone utah u s a abstract the middle jurassic entrada sandstone exposed near the town of escalante southern utah consists of large scale cross bedded eolian deposits that are interbedded with horizontally laminated sand sheets and thin sets of eolian cross strata representing periods with a moister climate the flat bedded units contain numerous tracks and trackways from small to large sized theropod dinosaurs these tracks are today exposed in several distinct erosional states allowing detailed studies of track and undertrack formation in eolian deposits tracks that originally were emplaced on sloping surfaces show in their present day erosional state a morphology distinct from those originally emplaced on horizontal surfaces further the range of eroded track morphologies can help identify badly eroded tracks from nonbiogenic structures in similar deposits

a review of current research on tl dating of loess abstract the thick loess deposits of china central europe and north america are particularly suitable for the application of the thermoluminescence tl dating method because individual grains are likely to have travelled large distances and thus been well exposed to light before deposition wind blown silt grains collected close to glacial rivers in alaska have been shown to give a zero age of not more than 2 ka demonstrating the efficiency of the zeroing mechanism differences in laboratory procedures can cause differences in the tl ages reported particularly for loess over 100 ka tl ages for interstadial soils in europe are in agreement with the very few radiocarbon dates on reliable material such as charcoal on the other hand tl dates from sites in belgium and north western germany indicate that the previously accepted chronology which was based on two radiocarbon dates on humic rich sediments is incorrect the use of the last interglacial palaeosol for assessing the tl dates on loess above and below it is limited by the uncertainty in the timing of termination of soil forming processes 107 and 71 ka are the limits suggested by the astronomically derived time scale results on deposits from china north america alaska and europe are discussed in this context

pliocene pedosedimentary cycles in the southern pampas argentina well developed bt horizons of five palaeosols p1 p5 have been recorded previously within a 20 m thick succession of pliocene siltstones and clayey siltstones in the southern part of the buenos aires province of argentina this paper reports a detailed field and micromorphological thin section investigation of a 6 m portion of the sequence encompassing p2 and p3 large scale faunal burrow infillings occur throughout other bioturbation features in the form of channel and spongy microstructures are mainly confined to the siltstones the intervening clayey siltstones bt horizons have been affected more by shrink swell disruption as evidenced by slickensides and a range of striated b fabrics in thin sections clay coatings indicative of illuvial accumulation of clay translocated in suspension from overlying a or e horizons occur in both the siltstones and clayey siltstones the types microstratigraphic associations and depth functions of features are interpreted in terms of changing interactions balances and dominances between sedimentary pedogenic and erosional processes over time thus providing the basis for the pedosedimentary reconstruction of landscape evolution in the region during part of the pliocene represented by the whole p1 p5 sequence 4 5 ma bp it is envisaged that this period was dominated by aeolian deposition although fluvial and mass movement processes probably led to reworking and redistribution of some of the materials overall rates of subaerial deposition however were not substantial pedogenic processes were active throughout the balance between sedimentation and pedogenesis varying over time in a cyclical fashion phases of reduced deposition and establishment of relatively stable land surfaces were marked by the development of argillic soil profiles with clearly defined eluvial and illuvial horizons intervening periods of more rapid accumulation of coarser material were characterized by accretionary soil development and welding of new pedological features on existing soils as the surface accreted first transforming existing eluvial horizons into bct ae horizons siltstones and then encouraging the syndepositional upward extension of these complex horizons the primary basis of the alternating units of siltstones bct ae horizons and clayey siltstones bt horizons lies in the cyclical change in size of particles deposited although pedogenic translocation processes enhanced these textural differences the underlying driving mechanism behind the pedosedimentary cycle can only be speculated upon although it is tempting to relate the sedimentation pattern to climatic fluctuations linked to glacial advances and retreats in the patagonian andes during the pliocene

a multi proxy study of argentina loess marine oxygen isotope stage 4 and 5 environmental record from pedogenic hematite abstract a 12 m loess paleosol section la angostura from tafi del valle tucuman argentina was studied using rock magnetic measurements geochemistry mossbauer effect particle size and nd isotopes in order to elucidate changes in paleoenvironment at the site combining the results of these experiments allowed us to separate the effects of the two major controls parent material and pedogenesis on the measured parameters two behavior regimes were identified in the sediment 1 in the lower half of the section pedogenic processes though weak dominate the variation of the sediment s physical properties and 2 for the upper half of the section subtle changes in parent material control the majority of the measured parameters even those typically controlled by pedogenesis e g clay fraction applying rock magnetic mossbauer and bulk geochemistry measurements in concert we calculated an iron budget for the loess 80 of the iron in the sediment is in paramagnetic minerals 20 of the iron is in hematite 1 6 of the sediment s mass and 1 of the total iron is present as magnetite maghemite 0 1 of the sediment s total mass neither the pedogenic formation nor the depletion of ferrimagnetic material with increasing pedogenesis was consistently observed in this sediment throughout the entire section the concentration of hematite is argued to be sensitive to in situ alteration and it is further surmised to be sensitive to the available moisture at the site finally we present a curiosity within the error of our chronology the concentration of hematite seems to correlate with the coeval climate record from antarctica vostok it is possible that the sedimentary magnetic record from la angostura is a proxy for the strength of the south american summer monsoon

origins and implications of soil layering abstract layering is common in soils due to a variety of pedologic and geologic processes and has important consequences for the interpretation of soils and landscapes layering can derive from original sedimentary layering depositional upbuilding episodic surface erosion deposition and stability soil production by weathering vertical or lateral translocation bioturbation and various combinations of these complex and polygenetic models incorporate both geogenic and pedogenic processes and allow for physical and biological processes as well as both vertical and horizontal movements we review these conceptual frameworks and synthesize them into a vertical contrast model vcm for interpreting layered surficial materials the vcm incorporates a variety of geologic and pedologic processes which may create destroy enhance or obscure vertical contrasts the model is illustrated via application to sites in the ouachita mountains usa and northwest saxonian lowlands germany the examples illustrate the importance of a comprehensive pedogeomorphic interpretation of layering since neither standard stratigraphic or top down pedogenetic principles necessarily apply the examples also show that the same process can sometimes contemporaneously both create and destroy vertical contrasts

recycled loesses a micromorphological approach to the determination of local source areas of weichselian loess the article presents the results of micromorphological studies of selected neopleistocene loess palaeosol sequences broader studies of thin sections are presented for the polanow samborzecki zlota site they served as models for analysis for similar targeted observations in other sequences on their basis 3 groups of microfeatures litho pedo and cryogenic were described an additional group are pedogenic features clay concentrations selected fe and mn fe nodules as well as charcoals documented in non soil locations generally limited to loess macroscopically defined as primary an analysis of these features shows that these are redeposited pedogenic microfeatures occurring in a secondary location according to this genetic interpretation they can be identified as pedorelicts and possibly also as lithorelicts these features clearly show that the older pedogenically modified layers were involved in the formation of younger loesses these studies show that the younger loesses are partially built of older loess material

change in atmospheric mineral aerosols in response to climate last glacial period preindustrial modern and doubled carbon dioxide climates desert dust simulations generated by the national center for atmospheric research s community climate system model for the current climate are shown to be consistent with present day satellite and deposition data the response of the dust cycle to last glacial maximum preindustrial modern and doubled carbon dioxide climates is analyzed only natural non land use related dust sources are included in this simulation similar to some previous studies dust production mainly responds to changes in the source areas from vegetation changes not from winds or soil moisture changes alone this model simulates a 92 33 and 60 change in dust loading for the last glacial maximum preindustrial and doubled carbon dioxide climate respectively when impacts of carbon dioxide fertilization on vegetation are included in the model terrestrial sediment records from the last glacial maximum compiled here indicate a large underestimate of deposition in continental regions probably due to the lack of simulation of glaciogenic dust sources in order to include the glaciogenic dust sources as a first approximation we designate the location of these sources and infer the size of the sources using an inversion method that best matches the available data the inclusion of these inferred glaciogenic dust sources increases our dust flux in the last glacial maximum from 2 1 to 3 3 times current deposition

short paper fossil vertebrate tracks and indenter mechanics a reconnaissance study is outlined showing how an improved understanding of the formation and character of fossil vertebrate tracks in soft sediments is provided by the application of the mechanical engineer s indenter theory supported by complementary scaled laboratory experiments only the footprint at the bottom of the shaft cut by the animal9s limbs in general offers the best preservation of the shape of the underside of the foot the character of the foot is less well preserved in the deformed bedding beneath the footprint and among laminae deposited in the shaft after the passage of the animal this understanding will help to reduce errors in the use of tracks in taxonomic biostratigraphic palaeoecological behavioural and environmental studies when a limbed vertebrate traverses yielding sediment the limbs deform the substrate into tracks which vary with the nature size and gait of the animal the forcefulness of its limb movements and the sediment properties most previous geological work on tracks and trackways has emphasized their taxonomic biostratigraphical palaeocological and behavioural significance lockley 1986 leonardi 1987 but without an adequate understanding of their environmental implications lockley 1986 and in particular their genesis and preservation as trace fossils the response of an elastic plastic material to an indenter or punch both in terms of theory calladine 1969 hill 1971 johnson et al 1982 and in the light of qualitative laboratory experiments provides a general mechanical model for track formation and a basis for the assessment of track preservation in sediments the indenter represents the animal9s

long lived pluvial episodes during deposition of the navajo sandstone abstract the navajo sandstone of the american southwest was deposited at approximately 190 ma in a giant subtropical dune field near the western margin of pangea from this unit we report thick intervals of dune cross strata that were churned by insects and trampled by reptiles although dunes continued to migrate freely the distribution of trace fossils shows that plant life in wet interdune areas sustained high levels of animal activity on the dunes for many thousands of years we interpret this suite of structures as the record of a pluvial episode climatologically similar to the period of greening in the sahara 4000 10 000 yr ago a high percentage of the rainfall on the navajo erg recharged the water table and led to the development of highly dilute local groundwater flow systems that discharged into interdune areas

burrow architecture and burrowing dynamics of ctenomys in foredunes and paleoenvironmental implications abstract ctenomys sp also known as tuco tuco is a solitary subterranean small rodent that inhabits sandy soils in south america we studied burrow system architecture of ctenomys flamarioni communities from the foredunes of the southern brazil coastal plain by inserting plaster of paris and excavating the tunnels the structure of the burrow system is complex with interlinked tunnels one occasionally open entrance multiple chambers and turnarounds blind laterals varying slopes t junctions bifurcations and two different levels a specific isolated chamber is used as a latrine while another is used as a nest the burrow entrance is open only when the rodent is taking out sand or feeding the tunnels have an average depth of 35 cm deepest at 55 cm and the most superficial at 15 cm near the entrance the average burrow length ranges from 190 to 500 cm the tunnels have different heights and widths varying from 5 5 9 3 cm wide to 6 11 cm high the entrance is inclined 28 the central part of the burrow system has a steeper slope with an inclination of 38 the plaster molds preserve claw marks of four digits of up to 4 mm in depth collapsed burrows are rapidly sealed to avoid the entrance of predators ctenomys sp burrows provide a suitable microhabitat which is used by the animals as protection from adverse environmental conditions particularly during the winter when wind impacts the coastal area the extensive interlinking tunnels provide underground routes to escape from predators ctenomys burrows in coastal dune environments are appreciably more complex than those excavated in arid environments which are shallower with no chambers and a slope of up to 20 such difference in the architecture of the burrows can be used as a criterion to reconstruct the paleoenvironment of burrow systems in the rock record

synchrony of southern hemisphere late pleistocene arid episodes a review of luminescence chronologies from arid aeolian landscapes south of the equator abstract luminescence dating chronologies that have been reported in various studies of late pleistocene arid land aeolian sequences from australia southern africa and south america are reviewed with the objective of determining whether any pan hemispheric synchroneity existed in the timing of landscape responses to late quaternary climate changes south of the equator the results broadly show that contemporaneous regional arid land aeolian activity occurred in australia and southern africa during the periods ca 65 41 and 36 9 ka the relatively limited luminescence data from the south american subcontinent also point to recurrent arid land aeolian deposition between 63 and 8 ka with increasing frequency in the period ca 32 8 ka records from all three continents suggest a period of reduced aeolian activity between 41 and 36 ka overall the data are indicative of extensive landscape instability of the low to mid latitudes in the southern hemisphere during the last glacial period particularly at the last glacial maximum which accords with mainstream opinions aeolian activity during the holocene has generally been localised the rigour with which comparisons can be made between the different studies however is constrained by variations in practices between laboratories and changes that have occurred to luminescence dating procedures over the years

historical climatic extremes as indicators for typical scenarios of holocene climatic periods in the pampean plain abstract the holocene has been marked by two different climatic periods in the pampas one 8 5 3 5 kyr b p characterized by temperatures and precipitation higher than today and the other 3 5 1 4 kyr b p semiarid generating parabolic dunes the humid period produced intense pedogenesis down to 40 lat s and a mobilization of iron oxides to 30 lat s which means tropical climate with temperatures above 20 c and precipitation higher than 2000 mm yr sand deflation and development of parabolic dunes occur under climates with 300 400 mm yr this contribution is based on geological and physical proxies typical weather scenarios of those climates are sporadically reproduced today during extremely humid or dry periods on that basis meteorological parameters of years beyond the thresholds of 2000 and 400 mm yr were processed dry periods were characterized by a large thermal amplitude frosts and stronger winds reproducing the continental anticyclonic circulation of the late holocene humid extremes were warmer than normal lower thermal amplitude with rains produced by local convection processes typical scenarios with precipitation above 2000 mm yr are 21 c mean temperature ca 1 c higher than the present record 27 c maximal annual temperatures 16 c minimal annual temperatures more than 1 c higher than the present as a consequence thermal amplitude was smaller than today virtually without frosts characteristic parameters of the late holocene were mean annual precipitation ca 350 mm yr 15 c mean temperature 22 c maximal annual temperatures 8 c minimal annual temperatures showing significative shifts in the dry season lower than normal monthly maximal and mean temperatures higher than today the result is a thermal amplitude larger than today probably higher quantity of frosts per year stronger winds and lower relative air humidity in comparison with the humid climate extreme complete the scenario

climate change evidences from the end of the little ice age to the current warm period registered by melincue lake northern pampas argentina abstract geochemical sedimentological historical and instrumental information from melincue lake 33 43 s 61 28 w was analyzed in order to reconstruct main hydro climatic changes along the pampean region considering the end of the little ice age lia and the current warm period cwp climatic phases elemental x ray fluorescence determinations were performed on a dated short core extracted from the deepest part of the lake chemical ca sr al k si ti and fe variation was analyzed along with physical magnetic susceptibility dry bulk density and medium particle size and mineralogical proxies as well as carbon and nitrogen contents organic and inorganic carbon and organic nitrogen multicomponent statistical analyses allowed the identification of the main environmental processes ruling sedimentation which included carbonate precipitation detrital input and primary productivity homogeneous carbonate rich detrital rich and organic matter poor deposits reflect very shallow and ephemeral lake conditions during the last years of the lia period very low sedimentation rates and the presence of discontinuities in the sedimentary record pointed to episodes of extensive lake shrinkages and probable lake floor subaerial exposures bedded and laminated organic rich muds accumulated in perennial lake conditions after ca ad 1880 reveal an important environmental change concurrent with the onset of the current warm period the contrast of sediment composition and lithological characteristics with the instrumental record of the cwp allowed us to consider the development of a shallow saline lake system enhanced detrital input and carbonate precipitation during dry periods in turn higher lake levels and thus more diluted lake waters during wetter periods resulted in enhanced organic lake productivity and lower carbonate precipitation the comparison of the paleolimnological reconstruction from melincue lake to different hydrological and paleoclimatic records i e limnimetric measurements and ocean temperature changes suggests that the moisture variation registered between the lia and the cwp was consistent with and likely forced by large scale climatic oscillations the present study provides new evidences to evaluate the climate and environmental changes in central argentina related to the dynamics of the south american monsoon system during the last five centuries

pedostratigraphy and pedological and geochemical characterization of las carreras loess paleosol sequence valle de tafi nw argentina abstract the las carreras loess paleosol sequence is considered the most complete quaternary pedostratigraphic record in south america it consists of 32 paleosols formed during the past 1 15 ma chronological control is provided by magnetostratigraphy sediment and paleosol characterization is based on a variety of methods including soil chemistry geochemistry and micromorphology the main pedogenic processes identified are carbonate leaching and reprecipitation ped formation and translocation of clay and organic matter in many cases the boundaries between individual paleosols are not clearly defined due to indistinct transitional zones based on both pedological and sedimentological characteristics the sequence was subdivided into three units with paleosols in units i and iii designated as luvisols and paleosols in unit ii tentatively classified as luvic kastanozems this subdivision reflects environmental changes associated with the mid pleistocene transition overall geochemical variability is low and largely related to pedogenesis the homogeneity suggests a rather constant provenance that seems to be linked to the central andes pursuant to the chaco model of iriondo 1997 models of deposition of loess and loessoids in the upper quaternary of south america journal of south american earth sciences 10 71 79 and includes direct volcanic ash falls and local sources in a subordinate manner in a paleoclimatic context loess paleosol alternation is interpreted to reflect climatic cycles that were primarily caused by the variability of the south american monsoon system

magnetic properties of modern soils and quaternary loessic paleosols paleoclimatic implications the magnetic properties of paleosols developed in quaternary sequences of loess have been used for stratigraphic definition correlation with other terrestrial and deep sea sequences and paleoclimatic paleorainfall reconstruction in some loess paleosol sequences including those of the chinese loess plateau tajikistan and the czech republic maxima in magnetic susceptibility values correspond with the paleosol horizons and minima with the least weathered loess layers in other loess soil sequences including those of siberia alaska and argentina the relationship is completely opposite with susceptibility minima associated with the most developed paleosols to account for these opposite relationships the respective roles of 1 magnetic enhancement and 2 magnetic depletion and or dilution in determining soil magnetic properties are investigated for a range of modern soil types most magnetic enhancement is seen in the upper horizons of well drained cambisols absence or loss of magnetic iron oxides is apparent in acid podsol profiles and waterlogged soils for the cambisol profiles significant correlation is found between susceptibility and organic carbon cation exchange capacity and clay content the mineralogy morphology and grain size of soil magnetic carriers extracted from three modern enhanced soils and a paleosol from the chinese loess plateau are also identified by independent petrographic means microscopy and x ray diffraction of magnetic extracts magnetite and maghemite of ultrafine grain size from 0 4 to 0 001 i m are the major contributors to the magnetically enhanced soils weathering can concentrate detrital magnetic grains especially in the fine silt size fractions of soils the magnetic data from the modern soils indicate that interpretation of paleosol magnetic properties must be done on a site specific basis taking into account the possibilities of pedogenic enhancement pedogenic dilution or depletion and allochthonous inputs of magnetic minerals excessively arid wet or acid soils are unable to form significant amounts of pedogenic ferrimagnets well drained intermittently wet dry soils with reasonable buffering capacity and a substrate source of fe show most magnetic enhancement for those soils which favour magnetic enhancement processes correlation has been found between the maximum value of the pedogenic susceptibility and the annual rainfall the almost unique pedogenic system in the chinese loess plateau where variation in soil forming factors other than climate is reduced to a global minimum allows use of the paleo susceptibility values as proxy paleorainfall values to identify the mechanism of any link between magnetic properties for example susceptibility and climate change the mineralogy and grain size of soil magnetic carriers requires detailed investigation given the prospect of 1 quantitative paleorainfall records from continental loess records 2 predictions of present and future climate change and 3 the value of paleoclimate data for testing of numerical climate models such magnetic investigations can contribute significantly to our understanding of past and future environmental change

upper quaternary geology of the lower carcarana basin north pampa argentina abstract the geological evolution of the lower carcarana basin reflects a sequence of dry and humid climates from a geomorphological point of view the area belongs to the pampean eolian system the geomorphological units comprise several fluvial geoforms partially masked by a loess carpet on which eolian erosive forms developed the sedimentary record is not simple the typical profile begins with a predominantly eolian unit composed of silty sand and including two pedogenic levels carcarana fm the formation is the result of the reworking of a dune field in the pampean sand sea is4 it is upper pleistocene in age is 3 another somewhat different climatic deterioration followed related to the begining of the last glacial maximum is 2 which caused the deposition of a loessic mantle tezanos pinto fm subsequent evolution of the climate involved a shift to humid conditions during the hypsithermal period generating a well developed soil at the top of the formation an upper holocene eolian layer san guillermo fm covers the whole sequence at the river margins of the basin the late pleistocene lower holocene eolian deposits are replaced by a complex silty clayey sequence mainly paludal with a soil complex in the middle of the section lucio lopez fm

late quaternary paleoenvironments and paleoclimatic conditions in the distal andean piedmont southern mendoza argentina abstract the andean piedmont of mendoza is a semiarid region covered by extensive and partially vegetated dune fields consisting of mostly inactive aeolian landforms of diverse size and morphology this paper is focused on the san rafael plain srp environment situated in the distal andean piedmont of mendoza 34 30 s and reports the sedimentology and osl chronology of two representative exposures of late quaternary deposits including their paleoenvironmental and paleoclimatic significance eleven facies including channel floodplain fluvio aeolian interaction and reworked pyroclastic and aeolian deposits were described and grouped into two facies associations fa1 and fa2 fa1 was formed by unconfined sheet flows minor channelized streams and fluvial aeolian interaction processes fa2 was interpreted as aeolian dune and sand sheet deposits osl chronology from the srp sedimentary record indicates that between ca 58 39 ka and ca 36 24 ka mis 3 aggradation was governed by ephemeral fluvial processes fa1 under generally semiarid conditions during mis 2 the last glacial maximum ca 24 12 ka a major climatic shift to more arid conditions is documented by significant aeolian activity fa2 that became the dominant sedimentation process north of the diamante atuel fluvial system the inferred paleoenvironmental conditions from the srp sections are in broad agreement with regional evidence

significance of thin sets of eolian cross strata abstract thin cosets composed of thick sets of trough cross strata record episodes when ergs were sand saturated and erg buildup exceeded the rate of subsidence and water table rise interdunes were enclosed and dry thin sets with irregular set boundaries accumulated when ergs were unsaturated as at white sands dune field in southern new mexico interdunes were flat extensive and moist thin lenses of cross strata with irregular upper surfaces are the erosional remnants of lowermost portions of dunes that were within the zone of capillary rise thin flat bedded to massive interdune deposits were also preserved in this setting due to low sand supply upbuilding of the erg surface was limited to the rate of subsidence water table rise like sediments deposited in shallow subaqueous settings bu unlike most colian sands bed by bed accumulation of the thin sets was limited by short term accommodation space the allogenic interpretation presented above contrasts strongly with the widely accepted climbing interdune autogenie interpretation of the entrada we question this gradualistic interpretation not only on the basis of stratal relationships between dune and interdune deposits but on theoretical grounds as well to maintain moist wet interdunes when large bedforms are climbing to preserve thick tabular sand bodies deposition must not exceed the rate of groundwater rise we have seen very few irregular erosion surfaces between thick sets of eolian cross strata they are extremely common between thin sets widespread moist interdunes in modern ergs and evidence of high water tables in ancient eolian sequences are signals of low sand supply thin eolian sets with irregular upper b unding surfaces record the birth and demise of ergs as well as the fluctuations of erg margins the absence of animal tracks in the thick jurassic cross strata and their great abundance in and adjacent to the thin sets may be a result of an erg margin origin of the thin sets or of ameliorated climatic conditions during their deposition because they accumulate in zones and episodes of low sand supply cosets composed of thin sets are akin to deflation surfaces in for example the permian cedar mesa sandstone the movement of the groundwater table after the initial deflationary phase slow rise in the jurassic rapid drop in the permian may reflect the higher amplitude of late paleozoie sea level fluctuations

physical properties and gas hydrate at a near seafloor thrust fault hikurangi margin new zealand the p paku fault zone drilled at iodp site u1518 is an active splay fault in the frontal accretionary wedge of the hikurangi margin in logging while drilling data the 33 m thick fault zone exhi

tracks and trackways of myotragus balearicus bate artiodactyla caprinae in pleistocene aeolianites from mallorca balearic islands western mediterranean tracks and trackways of the ruminant goat myotragus balearicus bate 1909 are abundant in the late pleistocene aeolianites of the south coast of mallorca spain the carbonate aeolianites form impressive dunes and related sand ramps that were initiated as echo dunes in front of a 20 40 m high paleocliff of miocene reefal limestone where the dunes built up to the cliff top they covered it as an aeolian ramp the dunes and sand ramps were active during the dry summer months but were passive during the wet winter period the small goat like animals were abundant on the island and for unknown reasons crossed the aeolian accumulations in large numbers this study deals with the tracks formed in the dune deposits all preserved trackways indicate impression into moist sand special features of the tracks include the structure produced by the withdrawal of the foot here called the axis and a disturbance zone of plastic deformation around this on dune crests the disturbance zone surrounds the axis more or less symmetrically however in addition a pressure pad of dislocated slightly rotated sediment bound by curved microfaults is commonly produced posterior to the axis by propulsive pressure of the foot on steep stoss and lee slopes the pressure pad becomes oriented in a down slope position as a result of gravitational slip of the walking animal combination of disturbance of the sediment in this way by manus followed by overprinting of similar disturbance by pes produces highly complicated track structure this structure may be characteristic of artiodactylous mammals in soft sand particularly aeolian deposits the structure is designated as bifidipes aeolis isp nov