holocene loess in illinois revealed by osl dating implications for stratigraphy and geoarchaeology of the midwest united states abstract most uplands in illinois are blanketed by late wisconsinan peoria loess and the conventional wisdom is that little or no dust accumulation occurred during the holocene 11 7 ka to present in a recent effort to investigate if illinois holocene loess was deposited and preserved we applied optically stimulated luminescence osl dating to seven locations where loess is thick these include four sites along the mississippi river in westernmost illinois and three loess bluffs south of the illinois river in central illinois our results suggest that holocene aged loess is preserved along the mississippi river in the state of illinois in contrast no holocene loess was found south of the illinois river in the central portion of the state in addition to its spatially limited distribution holocene loess thicknesses range only up to 1 m nevertheless loess stratigraphy and osl dating results provide the first holocene loess reported east of the missouri river our new finding also resolves the long time archeological puzzle that a number of artifacts of several thousand years old were buried by upland loess along the mississippi river

a full glacial biota from southeastern iowa usa wisconsinan full glacial silts filling a swale exposed in conklin quarry johnson co iowa contain a large and diverse biota that includes pollen bryophytes vascular plant macrofossils small mammals molluscs and insects radiocarbon dates on wood from the top middle and bottom of the swale fill respectively were 16710 270 17 170 205 and 18090 190 yr bp the pollen diagram is dominated by picea spruce pinus pine and cyperaceae sedge and it records low pollen accumulation rates plant macrofossils include a number of tundra species along with picea and larix larch needles and small pieces of wood the insect fauna contains many species now confined to the forest tundra transition zone of northwestern yukon and alaska small mammals include the tundra indicators dicrostonyx collared lemming and probably microtus miurus singing vole together with boreal forest taxa the molluscs include extinct and relict species and show the widest range in present geographic distribution but rocky mountain and especially northern elements predominate in the swale fill all these lines of evidence lead to consistent palaeoclimato logical interpretation and palaeoecological reconstruction the dominant habitats represented by the biota and sedimentary environment collectively included open calcareous silty to sandy or gravelly upland sites minerotrophic fens wetlands pond or stream side clayey to sandy shores and shallow possibly ephemeral cold clear water ponds mean july temperatures were probably 11 to 13 c cooler than at present the biota indicates that a picea larix krummholz with extensive tundra openings was present in southeastern iowa between 18090 and 16710 yr bp

interannual variability of the korea strait bottom cold water and its relationship with the upper water temperatures and atmospheric forcing in the sea of japan east sea 1 a 35 yearlong temperature data set is analyzed to investigate the long term temperature variability in the korea strait and its relationship with the temperature variability in the upper layer of the sea of japan east sea the second cyclostationary empirical orthogonal function mode of the vertical temperature section in the korea strait describes the interannual variability of the korea strait bottom cold water ksbcw according to the corresponding principal component time series the strength of the ksbcw fluctuates yearly with a major spectral peak around 3 years multiple regression analysis shows that the interannual ksbcw variability is closely linked with the temperature variability in the southwestern region of the sea of japan east sea at about 50 100 m depth along 40 n the source of the ksbcw is traced at about 50 m extending eastward from the east coast of korea to about 135 e at 37 n the source is traced at a deeper level about 50 100 m confined more toward the east coast of korea with a hint of double core characteristics the interannual ksbcw variability is also related to the southward wind stress along the east coast of korea it appears that strong cooling warming of upper water temperature induced by the basin scale wind stress results in the interannual ksbcw variability this connection is verified by showing a reasonable interannual covariability between the ksbcw and the basin scale wind stress

late holocene eolian activity in the mineralogically mature nebraska sand hills abstract the age of sand dunes in the nebraska sand hills has been controversial with some investigators suggesting a full glacial age and others suggesting that they were last active in the late holocene new accelerator mass spectrometry radiocarbon ages of unaltered bison bones and organic rich sediments suggest that eolian sand deposition occurred at least twice in the past 300014c yr b p in three widely separated localities and as many as three times in the past 80014c yr at three other localities these late holocene episodes of eolian activity are probably the result of droughts more intense than the 1930s dust bowl period based on independent great plains climate records from lake sediments and tree rings however new geochemical data indicate that the nebraska sand hills are mineralogically mature eolian sands in nebraska have lower k feldspar and k2o rb and ba contents than most possible source sediments and lower k feldspar contents than dunes of similar age in colorado the most likely explanation for mineralogical maturity is reduction of sand sized k feldspar to silt sized particles via ballistic impacts due to strong winds over many cycles of eolian activity therefore dunes of the nebraska sand hills must have had a long history probably extending over more than one glacial interglacial cycle and the potential for reactivation is high with or without a future greenhouse warming

age of colluvium indicates accelerated late wisconsinan hillslope erosion in the upper mississippi valley colluvium on foot slopes in parts of north america and europe has been attributed to a major mass wasting episode during the last glacial period stratigraphic evidence and 14 c ages support this hypothesis for the northern part of the upper mississippi valley colluvium in this region grades laterally into or interfingers with fluvial sediment beneath the late wisconsinan savanna terrace colluvial foot slopes are truncated by fluvial surfaces postdating the incision that created the savanna terrace between 13 and 11 ka samples from within the colluvium have 14 c ages between 18 6 and 12 ka ages of 28 9 and 20 3 ka have been obtained from beneath colluvium and fluvial sediment inset into colluvial foot slopes has yielded ages between 12 5 and 9 8 ka widespread permafrost during the late wisconsinan glacial maximum may explain the onset of accelerated mass wasting that produced the colluvium although mass wasting apparently continued for some time during subsequent climatic warming the results described here imply major long term climatically driven fluctuations in sediment supply from hillslopes to the fluvial system in this region

propagation and initiation mechanisms of the madden julian oscillation 1 an observational study of the propagation and onset mechanisms of the madden julian oscillation mjo is performed using cyclostationary empirical orthogonal function analysis and a kelvin rossby wave decomposition method for the noaa outgoing longwave radiation and the ncep ncar reanalysis data in these analyses two different regions of surface convergence are observed ahead of mjo convection by different wind components as previously found in a sst coupled gcm simulation at the leading edge of enhanced convection the friction induced meridional convergence appears during the developing phase when the enhanced convection is located over the indian ocean and the maritime continents another region of surface convergence is identified just east of an enhanced convection core and this tends to pull the convective core to the east the surface convergence is formed by zonal wind convergence and kelvin and rossby waves both play a comparable role in the formation of the convergence zone therefore the frictional kelvin rossby wave cisk conditional instability of the second kind is regarded as a primary factor for the eastward propagation of the mjo over the western indian ocean moistening in the boundary layer occurs 2 weeks earlier than the beginning of a new mjo cycle this moistening accompanies low level convergence by encircling kelvin waves which propagated from the region of enhanced convection during the previous cycle as well as by rossby waves generated from the region of reduced convection over the indian ocean this earlier formation of the boundary layer moisture convergence provides a favorable environment for triggering new convection this interaction of kelvin and rossby waves also accounts for the suppression of convection from the western side of the convection core for example over the indian ocean anomalous surface divergence appears at the western edge of the enhanced convection due to both circumnavigating kelvin waves from the region of reduced convection of the previous cycle and rossby waves from the region of the enhanced convection itself thus the mjo is a self maintaining and self generating form of tropical variability through the interaction between convection and large scale circulation in the presence of boundary layer dynamics

the effect of surface curvature on the deposition of loess a physical model summary a physical model for the deposition of fine dusty material loess on curved surfaces is presented the model is tested in a sedimentation experiment with a symmetrical hill with length axis perpendicular to the flow direction in a wind tunnel it appears both from the model and the experiment that loess deposition will occur preferably on windward slopes and not on leeward ones in contrast to the widespread wind shadow concept below the deflation threshold loess deposition increases as wind speed increases above the deflation threshold an effective accumulation of the loess layer on the surface will occur within a well defined wind speed interval the loess layer on the surface will erode away only if wind speed has exceeded this interval for flat and dry surfaces free of roughness elements the upper limit of the interval is 7 m s free stream velocity for wet surfaces however it may be considerably higher 15 m s and more

complex response of a midcontinent north america drainage system to late wisconsinan sedimentation abstract the geomorphic evolution of mud creek basin in eastern iowa u s a serves to illustrate how geomorphic influences such as sediment supply valley gradient climate and vegetation are recorded in the alluvial stratigraphic record sediment supply to the fluvial system increased significantly during the late wisconsinan through a combination of periglacial erosion and loess accumulation subsequent evolution of the holocene alluvial stratigraphic record reflects long term routing of the late wisconsinan sediment through the drainage basin in a series of cut and fill cycles whose timing was influenced by hydrologic response to change in climate and vegetation when viewed in a regional context the alluvial stratigraphic record appears to reflect a long term complex response of the flu ial system to increased sediment supply during the late wisconsinan hydrologic and sediment supply changes accompanying the spread of euroamerican agriculture to the basin in the 1800s dramatically upset trends in sedimentation and channel behavior established during the holocene

morphology and paleoenvironmental significance of quaternary sand veins sand wedges and composite wedges tuktoyaktuk coastlands western arctic canada sand and sand ice fillings of quaternary thermal contraction cracks on summer and hadwen islands western arctic canada comprise sand veins sand wedges and composite wedges sand wedges in diamicton poor ice diamicton rich ice and ice rich sand generally have simple v shapes whereas those in ice poor sand vary from v shaped to irregular forms and may contain inclusions of host sand these morphological differences are explained in terms of the relative tensile strength of the wedge and host materials bundles of sand veins within sand wedges indicate discrete stages of wedge growth criteria previously proposed for identifying relict sand wedges are reevaluated 1 not all wedges are v shaped some are irregular forms with offshoot sand veins 2 a vertical or steeply dipping lamination is not apparent within all wedges some appear to have a massive fill suggesting that the sand source can be texturally and mineralogically very uniform 3 individual sand veins and groups of veins can be just as common within sandy host materials as the better known sand wedges composite sand ice wedges at crumbling point summer island commenced growth as composite wedges continued as sand wedges were modified by thermokarst and in some cases recommenced at a stratigraphically higher level as ice wedges the sand wedge and ice wedge stages reflect environmental change from cold arid and windy proglacial conditions during oxygen isotope stage 2 to warmer and wetter interglacial conditions during oi stage 1

a new model of topographic effects on the distribution of loess a model of topographic influence on the regional transport and accumulation of loess in sparsely vegetated landscapes is proposed based on the critical role played by saltating eolian sand in the entrainment and long distance transport of finer grained suspended dust in this model long term accumulation of loess occurs mainly downwind of topographic obstacles that limit eolian transport of sand and associated re entrainment of dust regional and local patterns of distribution of late wisconsinan loess in parts of the upper mississippi river basin are closely related to the distribution of topographic obstacles to sand transport these cases of topographic influence occur in a region where evidence exists for sparse tundra like vegetation during the deposition of loess in the late wisconsinan similar topographic effects may not be evident further south in the missouri and mississippi river basins because vegetation density was generally sufficient to prevent the movement of eolian sand out of source valleys thus topographic obstacles and dense vegetation may have similar effects on loess distribution under different environmental conditions

movement and structural variation of warm eddy we92 for three years in the western east japan sea abstract approximately three years of longitudinal research from december 1992 to may 1995 examined movement and structural variation of a specific warm eddy we92 in the western east japan sea we92 found off the south of ulleung island in the east japan sea moved northward west of ulleung island and then eastward along the polar front the intrusion of east japan sea intermediate water and lateral mixing between the warm eddy and intermediate water in the summer and fall of 1993 gradually reduced we92 s diameter 150 170 km and maximum depth about 310 m the east korean warm current ekwc and we92 converged around ulleung island and the ekwc supplied we92 with high temperature and high salinity water high salinity water which flowed into the edge of the warm eddy gradually expanded into the inner portion of we92 in summer and fall before convective mixing occurred in winter energy from the ekwc replenished vorticity in the warm eddy which had been gradually declining a homogeneous layer lens caused by atmospheric cooling in the core of we92 formed from the surface layer to a maximum depth of 250 m throughout the winter the temperature of the mixed layer at the surface near ulleung island was almost homogeneous averaging approximately 10 c the first winter and lower than 8 c in the other two winters if a warm eddy moves north several times throughout the winter and then moves east a much lower temperature can be expected in the mixed layer at the eddy s center the maximum velocity of the warm eddy 30 60 cm s nearly equaled that of the ekwc but the depth of maximum velocity 50 150 m exceeded that of the ekwc based on the effects of the ekwc on we92 the currents of the warm eddy flowed fastest on the west side of we92

interannual to interdecadal variability in the japan sea based on a new gridded upper water temperature dataset a new gridded water temperature dataset of upper 400 m depths 0 50 100 200 300 and 400 m for the japan sea or east sea is produced by using an optimal interpolation technique from 1930 to 1996 based on oceanographic observations collected in the world ocean database 1998 the temperature data are analyzed by a complex empirical orthogonal function ceof with six levels combined using the data for a period from 1957 to 1996 during which most of gridded data are available before calculating the ceofs low pass or highpass filters cutoff period at 7 yr are applied to separate interannual and decadal temperature changes respectively one interannual and two decadal ceof modes are identified the interannual first ceof mode is characterized by the energetic variability around and south of the subpolar front in the western japan sea accompanied by northward and northeastward phase propagations emanating from the tsushima strait the decadal first ceof mode exhibits a broad structure prevailing over the whole japan sea but large amplitudes are trapped by the subpolar front with 608 908 phase lags between the northeastern and southwestern japan sea the decadal second ceof mode has a localized structure with strong correlations in the yamato basin the relation between the atmosphere and ocean is analyzed by a correlation analysis of wintertime sea level pressures slps onto the temporal coefficients of the ceof modes the interannual first ceof mode is accompanied by the slp anomalies over the western north pacific ocean with steep slp gradients over the japan sea suggesting that this mode is forced by local wind anomalies associated with the slp changes over the western north pacific the decadal first ceof mode is likely to be caused by changes of the east asian winter monsoon due to the slp variability of the northern part of the siberian high which is closely associated with the decadal fluctuations of the arctic oscillation and the north atlantic oscillation the second decadal ceof mode is accompanied by high slp correlations over the central north pacific associated with strength changes of aleutian lows suggestive of remote forcing from the central north pacific

decadal variability of the upper ocean heat content in the east japan sea and its possible relationship to northwestern pacific variability 1 the upper ocean heat content variability in the east japan sea was investigated using a 40 year temperature and salinity data set from 1968 to 2007 decadal variability was identified as the dominant mode of variability in the upper ocean 0 300 m aside from the seasonal cycle the decadal variability is strong to the west of northern honshu west of the tsugaru strait and west of southern hokkaido temperature anomalies at 50 125 m exhibit a large contribution to the decadal variability particularly in the eastern part of the east japan sea the vertical structure of regressed temperature anomalies and the spatial patterns of regressed 10 c isotherms in the east japan sea suggest that the decadal variability is related to upper ocean circulation in the east japan sea the decadal variability also exhibits an increasing trend which indicates that the regions showing large decadal variations experienced warming on decadal time scales further analysis shows that the decadal variability in the east japan sea is not locally isolated but is related to variability in the northwestern pacific

dust transport and the question of desert loess formation although contemporary dust storms are frequent in arid and semi arid areas desert loess deposits are poorly developed much of the world s loess occurs in mid latitude areas which experienced glaciation during the pleistocene ocean core evidence indicates that dust transport from sub tropical deserts increased during cold stages of the pleistocene but loess formed only on certain desert margins for reasons which have not been fully explained this paper re examines the mechanisms of dust transport and deposition and the circumstances leading to the accumulation of thick loess typical loess is composed mainly of medium silt grains which are transported in short term suspension a few metres above the ground significant thicknesses of loess form only when dust is trapped within a limited area often relatively close to the source dust particles finer than 20 m are transported mainly in long term suspension over a greater height range and may be widely dispersed the availability of silt and the frequency magnitude and direction of dust transporting winds are important factors governing the potential for loess formation but the existence of a suitable dust trap is particularly important traps may be formed by topographic obstacles areas of moist ground or vegetated surfaces vegetation adjacent to glacial outwash plains and braided meltwater streams trapped dust in mid latitudes during the pleistocene dust blown during glacial periods from certain deserts notably in sinai soviet central asia and china accumulated as loess in neighbouring semi arid regions on the margins of other deserts loess formation was inhibited partly by the absence of vegetation traps during most of the holocene net dust deposition rates in all desert marginal areas have been too low for significant loess accumulation this is mainly due to a reduction in silt availability and a tendency towards landscape stability reported dust storm frequencies during the past 50 years over estimate the longer term holocene dust flux due to the effects of human activities much modern dust owes its origin to erosion of cultivated soils in semi arid areas and is finer than typical loess

origin and paleoclimatic significance of late quaternary loess in nebraska evidence from stratigraphy chronology sedimentology and geochemistry muhs d r bettis iii e a aleinikoff j n mcgeehin j p beann j skipp g marshall b d roberts h m johnson w c benton r 2008 origin and paleoclimatic significance of late quaternary loess in nebraska evidence from stratigraphy chronology sedimentology and geochemistry gsa bulletin 120 11 12 1378 1407

transport direction of wisconsinan loess in southeastern minnesota a study of wisconsinan loess in part of southeastern minnesota confirms earlier suggestions that much of the loess in this region was not derived flora the floodplain of the mississippi river two wisconsinan loess units the peoria loess and roxana silt occur in the study area peoria loess 1 8 m thick fines systematically eastward from an abrupt western border toward the mississippi there are no apparent grain size trends away from other adjacent rivers peoria loess thickness generally decreases eastward but is highly variable probably because of differential erosion potential sources for this unit are pre wisconsinan sediments on the iowan erosion surface immediately west of the border of thick loess and wisconsinan glacial sources tens or hundreds of kilometers to the west the underlying roxana silt up to 1 m thick occurs only near the mississippi and fines away from that river the roxana silt deposit could reflect aggradation of the mississippi floodplain because of glacial activity upstream and does not have clear implications for upland vegetation near the study area by contrast transport of the peoria loess from distant glacial sources or wind erosion of upland surfaces closer to the loess deposit both imply extensive very sparsely vegetated surfaces west of the study area when the peoria loess accumulated

plant and insect remains from the wisconsinan interstadial stadial transition at wedron north central illinois abstract organic material exposed within a small swale fill in pit 6 of the wedron silica sand co near wedron in lasalle county illinois includes well preserved pollen plant macrofossils and insect remains this material occurs in slackwater sediment in the lower part of the peddicord formation which was deposited as existing valleys were dammed by fluvial aggradation during the initial late wisconsinan advance of laurentide ice into the wedron area wood from the organic horizon has a radiocarbon age of 21 460 470 yr b p isgs 1486 the pollen spectrum is dominated by picea pinus and cyperaceae plant macrofossils comprise a mix of boreal forest taxa including picea larix laricina and the moss campylium stellatum subarctic species including betula glandulosa empetrum nigrum and selaginella selaginoides along with the predominantly arctic vaccinium uliginosum var alpinum dryas integrifolia and rhododendron lapponicum the insect fauna contains the western montane ground beetle opisthius richardsoni several arctic subarctic ground beetles including diacheila polita helophorus sibiricus and pterostichus cryobius caribou and a diverse assemblage of insects that today inhabit the boreal forest we interpret the biotic record to record a phase in the transition from closed boreal forest to open tundra as climatic conditions deteriorated in advance of continental glaciation

loess studies in central united states evolution of concepts abstract few words in the realm of earth science have caused more debate than loess it is a common term that was first used as a name of a silt deposit before it was defined in a scientific sense because this loose deposit is easily distinguished from other more coherent deposits it was recognized as a matter of practical concern and later became the object of much scientific scrutiny loess was first recognized along the rhine valley in germany in the 1830s and was first noted in the united states in 1846 along the lower mississippi river where it later became the center of attention the use of the name eventually spread around the world but its use has not been consistently applied over the years some interpretations and stratigraphy correlations have been validated but others have been hotly contested on conceptual grounds and semantic issues the concept of loess evolved into a complex issue as loess and loess like deposits were discovered in different parts of the us the evolution of concepts in the central us developed in four indefinite stages the eras of 1 discovery and development of hypotheses 2 conditional acceptance of the eolian origin of loess 3 bandwagon popularity of loess research and 4 analytical inquiry on the nature of loess toward the end of the first era around 1900 the popular opinion on the meaning of the term loess shifted from a lithological sense of loose silt to a lithogenetic sense of eolian silt however the dual use of the term fostered a lingering skepticism during the second era that ended in 1944 with an explosion of interest that lasted for more than a decade in 1944 r j russell proposed and h n fisk defended a new non eolian property based concept of loess the eolian advocates reacted with surprise and enthusiasm each side used constrained arguments to show their view of the problem but did not examine the fundamental problem which was not in the proofs of their hypothesis but in the definition of the term between 1944 and about 1950 the debates about loess reached a maximum level of complexity the main semantic problem was submersed in peripheral arguments about physical properties and genetic interpretations the scholarly treatment of the subject by fisk and russell stimulated quality responses from a diversity of earth scientists interested in academic and applied studies particularly geo history pedology soil mechanics and stratigraphy the long lasting popularity of loess studies during the bandwagon era lasted to about 1970 by that time the analytical and technical interests had attracted the mainstream into the fourth era with a focus beyond the old arguments although fisk and russell found themselves defending an unpopular theory they stimulated a scientific interest in the late quaternary history of the mississippi valley that may never be exceeded

the nature origin and accumulation of loess abstract loess can be defined simply as a terrestrial clastic sediment composed predominantly of silt size particles which is formed essentially by the accumulation of wind blown dust there are three fundamental requirements for its formation 1 a sustained source of dust 2 adequate wind energy to transport the dust and 3 a suitable accumulation site most loess has been modified to some degree by local reworking bioturbation and syn depositional weathering but a process of loessification is not necessary for a dust deposit to qualify as loess the terms primary loess and secondary loess have previously been used to described wind deposited loess and redeposited loess respectively but it is more accurate to describe material reworked and redeposited by non aeolian processes as loess derived colluvium or loess derived alluvium during the quaternary loess formed in three main situations 1 mid continental shield areas beyond the limits of ice sheets periglacial loess 2 on the margins of high mountain ranges perimontane loess and 3 on the semi arid margins of some lowland deserts peridesert loess peridesert loess is relatively poorly developed partly due to the limited efficiency of silt generating mechanisms in low land deserts compared with glaciation but also important is the tendency in arid areas for dust to be dispersed over a wide area and to be rapidly reworked after deposition particularly in areas which experience frequent climatic changes the remarkably thick loess of china and central asia results from an unusual combination of conditions which has persisted for much of the last 2 3 million years namely rapid uplift of the tibetan plateau and surrounding mountain ranges high rates of sediment production and supply to adjacent basins a strong northwesterly and westerly wind regime and the existence of effective dust traps downwind of the source regions

spatial and temporal variability of the north korean cold water leading to the near bottom cold water intrusion in korea strait abstract in the deepest region of korea strait the surface temperature is highest in august lowest in march while the near bottom temperature is lowest in september highest in may cross spectral analysis of the monthly temperature data between the two layers shows high coherence at the annual frequency with phase of 154 why and how does such a nearly opposite phasing occur between the surface and the near bottom temperatures there this study aims at answering these questions using historical and recently observed data cold and relatively fresh subsurface water flowing southward along the east coast of korea and known as the north korean cold water nkcw becomes noticeable in april near the sokcho coast the zonal temperature gradient there is largest around june the width of the nkcw becomes larger from april to august after october the nkcw retreats back toward the coast the southward movement of the nkcw is thus strong over a period of six to seven months and weak in winter especially in february the nkcw flows southward relatively quickly along the coast in april to october and arrives at the ulleung basin within one to two months because of the sill between the ulleung basin and korea strait this water cannot continue to flow to south but piles up for about two to three months before it moves over the sill the convergence of the subsurface cold water in the ulleung basin displaces the isopycnals upward and this water then intrudes over the sill along the isopycnals this explains why in april or may when this water appears noticeably at the sokcho coast the near bottom water in korea strait is warmest and in august or september when the nkcw which is piled up enough at the southern end of the ulleung basin intrudes to korea strait the near bottom temperatures there are at their lowest the origin of the nkcw seems to be the water of salinity less han 34 1 psu and surface density of 27 or higher which sinks in the northwestern east sea in january march the sinking of the water results from surface cooling in winter and is intensified due to the strong negative windstress curl the cold and relatively fresh water formed in the northwestern east sea is hypothesized to flow to the ulleung basin along three major paths along the east coast of korea through the channel north of ulleung do island and through the channel between ulleung do and dok do islands

loess of the upper mississippi valley driftless area abstract loess of the driftless area includes four distinct late quaternary lithostratigraphic units the wyalusing new loveland roxana and peoria formations erosion has removed parts or all of the pre late wisconsian loess at many sites these formations consist largely of loess and retransported loess that typically occurs on uplands terraces and valley margins in the region the oldest widespread formation probably 125 000 yr b p is here formally named the wyalusing formation the three younger formations correlate with the loveland probably 125 000 yr b p roxana 55 000 25 000 yr b p and peoria 25 000 12 000 yr b p loesses recognized elsewhere in the midcontinental united states the soil stratigraphic morphology of the wyalusing loveland and roxana peoria couplets appears to represent two distinct loess sedimentation sequences related to major expansion and contraction of the laurentide ice sheet during oxygen isotope stages 6 and 3 2 respectively the occurrence frequency of loess units is inversely related to age illustrating the erosional nature of the driftless area landscape the occurrence of four loess units at some sites in driftless area stratigraphic sections corroborates loess stratigraphy along the length of the mississippi valley where typically not more than four or five loess units are found and they represent only the late and middle pleistocene

water masses and decadal variability in the east sea sea of japan abstract water masses in the east sea are newly defined based upon vertical structure and analysis of ctd data collected in 1993 1999 during circulation research of the east asian marginal seas creams a distinct salinity minimum layer was found at 1500 m for the first time in the east sea which divides the east sea central water escw above the minimum layer and the east sea deep water esdw below the minimum layer escw is characterized by a tight temperature salinity relationship in the temperature range of 0 6 0 12 c occupying 400 1500 m it is also high in dissolved oxygen which has been increasing since 1969 unlike the decrease in the esdw and east sea bottom water esbw in the eastern japan basin a new water with high salinity in the temperature range of 1 5 c was found in the upper layer and named the high salinity intermediate water hsiw the origin of the east sea intermediate water esiw whose characteristics were found near the korea strait in the southwestern part of the east sea in 1981 kim k chung j y 1984 on the salinity minimum and dissolved oxygen maximum layer in the east sea sea of japan in t ichiye ed ocean hydrodynamics of the japan and east china seas pp 55 65 amsterdam elsevier science publishers is traced by its low salinity and high dissolved oxygen in the western japan basin ctd data collected in winters of 1995 1999 confirmed that the hsiw and esiw are formed locally in the eastern and western japan basin creams ctd data reveal that overall structure and characteristics of water masses in the east sea are as complicated as those of the open oceans where minute variations of salinity in deep waters are carefully magnified to the limit of ctd resolution since the 1960s water mass characteristics in the east sea have changed as bottom water formation has stopped or slowed down and production of the escw has increased recently

seasonal variation of the korea strait bottom cold water and its relation to the bottom current 1 analysis of high resolution hydrographic and current data revealed that the korea strait bottom cold water ksbcw flowed into the korea strait from may to january and contained two temperature minimums one in august september and another in december january with the main current flows confined within 70 km of the korean coast maximum southwestward bottom currents corresponded with the temperature minimums time series of bottom current and temperature near the korean coast clearly showed that the bottom temperature decreased as the bottom current strengthened seasonal variation of the ksbcw was linked to the combined effects of the barotropic and baroclinic current variations in the korea strait the annual minimum bottom temperature of the ksbcw was associated with the maximum southwestward baroclinic component the ksbcw had a secondary maximum southwestward bottom current and secondary minimum temperature in december january when the tsushima warm current twc flowing into the east japan sea ejs had the minimum volume transport

chronologic evidence for multiple periods of loess deposition during the late pleistocene in the missouri and mississippi river valley united states implications for the activity of the laurentide ice sheet abstract the loess stratigraphy of the mid continental u s is an important proxy record for the activity of the laurentide ice sheet in north america one of the most outstanding problems is deciphering the age of loess deposits in this area during the late pleistocene radiocarbon dating of snails and thermoluminescence dating of the fine silt fraction 4 11 m from loess at the loveland loess type section loveland iowa and a recent excavation at the pleasant grove school section madison county illinois provide new chronologic control on loess deposition in the mississippi missouri river valley chronology indicates that the loveland loess is illinoian in age 135 20 ka but is not correlative with the teneriffe silt which is dated to 77 8 ka concordant radiocarbon and thermoluminescence age estimates demonstrate that the roxana silt and a correlative loess in iowa the pisgah formation is probably 40 30 ka old these age estimates in conjunction with previous results indicate that there were four periods of loess deposition during the last 150 ka at 25 12 ka 45 30 ka 85 70 ka and at ca 135 20 ka this chronology of loess deposition supports the presence of both a late illinoian and early wisconsinan loess and associated soils thus there may be more than one soil in the loess stratigraphy of the mid continental u s with morphologies similar to the sangamon soil the last three periods of loess deposition may be correlative with periods of elevated dust concentrations recorded in the dye 3 ice core from southern greenland this is particularly significant because both areas possibly had the same source for eolian particles reconstructions of atmospheric circulation for glacial periods show a southerly deflected jet stream that could have transported dust from the mid continental usa to southern greenland lastly the inferred record of loess deposition is parallel to a chronology for deglaciation of the laurentide ice sheet deciphered from chronologic and stratigraphic studies of raised glacial and marine sediments in the hudson bay lowlands canada these chronologies indicate that the laurentide ice sheet was quite dynamic during the late pleistocene advancing and retreating across north america at least four times during the last 150 ka

high frequency pn sn velocities some comparisons for the western central and south pacific high frequency pn sn velocities for earthquakes originating in the subduction zones of the western pacific suggest that the travel paths of these phases recorded in the range of 12 to 30 may be significantly different from those of pn sn phases recorded at distances less than 12 or greater than 30 this suggestion is supported by high frequency pn sn velocities for intra plate earthquakes in the central and south pacific

roxana silt of the upper mississippi valley lithology source and paleoenvironment significant lithological differences exist between the middle wisconsinan roxana silt loess of the upper mississippi valley the valley north of 41 5 and that of the type area near st louis missouri primary differences are that the upper mississippi valley roxana silt is much thinner finer textured and more weathered than that of the type area extrapolation of radiocarbon dates brackets sedimentation of upper mississippi valley roxana silt between 55 and 27 ka which is in close agreement with dates from the type area radiocarbon dates and paleobotanical data indicate that the upper mississippi valley roxana silt accumulated at a maximum long term average sedimentation rate of about 7 cm 1 000 yr within a boreal forest environment whereas the type area roxana silt accumulated at a maximum long term average sedimentation rate of about 60 cm 1 000 yr within a prairie like environment multiple regression analysis shows that more than 75 of the variance in thickness and texture between the upper mississippi valley roxana silt and that of the type area is explained by parameters of source valley width source valley azimuth and distance of the depositional site from the source valley this indicates that although the lithologic characteristics and sedimentation rates between the two regions are quite different they are consistent with a unified loess sedimentation sys tem linked to the ancient mississippi river valley a proglacial source for the roxana silt and a middle wisconsinan advance of the lauren tide ice sheet is a topic of scientific debate because recent findings show a lack of roxana correlative till deposits in the midwest alternative hypotheses include a glaciolacustrine source a regional slope erosion source and a cold climate desert dust source tests of these hypotheses support a proglacial origin for the roxana silt multiple regression analysis of loess thickness and texture along with paleobotanical evidence indicates that the roxana silt was blown from the ancient mississippi valley rather than from a cold climate desert source or from flood plains linked to a glaciolacustrine source geochemical and mineralogical composition of the upper mississippi valley roxana silt compared to out wash derived peoria loess indicates that detritus from regional hillslope erosion is not a unique component of the roxana silt combined data indicate that the midcontinental roxana silt was derived as loess blown from flood plains of middle wisconsinan proglacial rivers between 55 and 27 ka

currents in korea tsushima strait during summer 1999 results are presented from continuous current measurements across korea tsushima strait between may and october 1999 the data are from eleven bottom mounted acoustic doppler current profilers that recorded full depth profiles of currents along two lines one at each end of the strait the two sections show markedly different mean flow regimes at the southern entrance the cross section flow varies smoothly across the channel showing a broad maximum at mid channel the northern section is marked by strong spatial variability but in the mean consists of two streams one on each side of the strait between the two is a regime of highly variable flow with a weak mean presumably indicating the wake from tsushima island flow variability in time is described by statistical measures and by representative snapshots