micromorphology of a welded sangamonian to wisconsinan age paleosol in southwestern wisconsin abstract micromorphological characteristics indicate that in southwestern wisconsin pedogenesis transgressed the sangamonian wisconsinan chronostratigraphic boundary in conjunction with colluvial and eolian sedimentation the use of micromorphology helps to distinguish between pedological colluvial and eolian components in the paleosol horizon sequence which can be difficult to resolve and interpret solely from field investigations and from other laboratory analyses results show that a basal loess mixed zone within the welded paleosol profile contains features that are the products of colluvial reworking processes we present micromorphology data which support stratigraphic relationships suggesting that colluvial processes were important in the formation of basal loess mixed zones in addition to other possible mixing processes such as pedoturbation and bioturbation

late quaternary chronostratigraphic framework of terraces and alluvium along the lower ohio river southwestern indiana and western kentucky usa abstract the lower ohio river valley is a terraced fluvial landscape that has been profoundly influenced by quaternary climate change and glaciation a modern quaternary chronostratigraphic framework was developed for the lower ohio river valley using optically stimulated luminescence osl dating and allostratigraphic mapping to gain insights into the nature of fluvial responses to glacial interglacial stadial interstadial transitions and holocene climate change river deposits t0 youngest to t7 oldest were mapped along a 75 km reach of the lower ohio river and were dated using 46 osl and 5 radiocarbon samples the examination of cores combined with osl and radiocarbon dating shows that fluvial sediments older than marine oxygen isotope stage mis 2 are present only in the subsurface aggradation during mis 6 illinoian glaciation filled the valley to within 7 m of the modern floodplain and by 114 ka mis 5e sangamon interglacial the ohio river had scoured the mis 6 sediments to 22 m below the modern floodplain surface there were no fluvial sediments in the valley with ages between mis 5e and the middle of mis 3 the mis 3 ages 39 ka and stratigraphic position of t5 deposits suggest the ohio river aggraded 8 14 m during mis 4 or mis 3 near the end of mis 3 the ohio river incised the mid last glacial mid wisconsinan deposits 10 m and began aggrading again by 30 ka aggradation continued into mis 2 with maximum mis 2 aggradation occurring before 21 ka which is coincident with the global last glacial maximum lgm as the ohio river adjusted to changing fluxes in sediment load and discharge following the lgm it formed a sequence of fill cut terraces in the mis 2 outwash that get progressively younger with decreasing elevation ranging in age from 21 ka to 13 ka from 14 ka to 13 ka the ohio river rapidly incised 3 m to form a new terrace and by 12 ka at the onset of the holocene the ohio river established a meandering channel pattern the river formed a broad floodplain surface from 12 ka to 6 ka and then incised 1 m and formed a fill cut terrace from 6 ka to 5 ka after 5 ka likely in response to mid holocene drought in north america the ohio river incised 5 m and by 4 ka the river began aggrading again the ohio river has aggraded 4 m since aggradation began at 4 ka the chronostratigraphic framework and reconstructed history developed here suggest that the lower ohio river is highly sensitive to glacial interglacial transitions and abrupt holocene climate change and responds rapidly to these allogenic forcings

quaternary aminostratigraphy of mississippi valley loess five pleistocene loess units in the mississippi valley that contain terrestrial gastropod fossils are differentiated by amino acid ratios aile ile values in the total acid hydrolysate of the fossil terrestrial gastropods hendersonia occulta catinella and succinea late wisconsin peoria loess which has been independently dated by radiocarbon and thermoluminescence methods is identified by alle ile values in fossil gastropods which progressively increase from northern illinois to southern louisiana early to middle wisconsin roxana silt is characterized by alle ile values in hendersonia only slightly greater and values in catinella and succinea distinctly greater than those of the peoria loess aiie ile values in hendersonia suggest that the chinatown silt informal term in illinois and the loveland silt in arkansas are the same age independent geologic evidence suggests that they predate the sangamon last interglacial aile ile values in hendersonia from the sicily island loess informal term in louisiana indicate that it is significantly older than the loveland silt and the chinatown silt the oldest loess unit recognized by alle ile values in hendersonia from the mississippi valley is the county line silt informal term in illinois the study shows that amino acid ratios in fossil gastropods from loess are an extremely valuable relative age indicator and provide a means of long distance correlation of midcontinent loess deposits

modern sangamon and yarmouth soil development in loess of unglaciated southwestern illinois abstract the thebes section in unglaciated southwestern illinois contains a well preserved 500 kyr loess paleosol sequence with four loesses and three interglacial soils various magnetic mineralogical and elemental properties were analyzed and compared over the thickness of soil sola these proxies for soil development intensity have the following trend yarmouth geosol sangamon geosol modern soil quartz plagioclase zr sr and tio 2 na 2 o ratios were most sensitive to weathering frequency dependent magnetic susceptibility and anhysteretic remanent magnetization greatest in a horizons also correspond well with soil development intensity neoformed mixed layered kaolinite expandables suggestive of a warm humid climate were detected in the sangamon and yarmouth soil sola clay illuviation in soils was among the least sensitive indicators of soil development differences in properties among interglacial soils are interpreted to primarily reflect soil development duration with climatic effects being secondary assuming logarithmic decreases in weathering rates the observed weathering in the sangamon geosol is consistent with 50 kyr of interglacial weathering oxygen isotope stage 5 compared to 10 kyr for the modern soil oxygen isotope stage 1 we propose that the yarmouth geosol in the central midwest formed over 180 kyr of interglacial weathering including oxygen isotope stages 7 9 and 11

age genesis and paleoclimatic interpretation of the sangamon loveland complex in the lower mississippi valley u s a for more than a century the sangamon paleosol the sangamon has been an integral part of geologic and pedologic investigations in the central united states including the upper mississippi and lower missouri river valleys compositional pedologic micromorphologic stratigraphic and age data indicate that the prominent reddish paleosol developed in silt rich deposits of the lower mississippi valley from southernmost illinois to northwestern mississippi represents multiple periods of soil formation and is wholly or in part time equivalent to the sangamon of the central united states thermoluminescence data for localities where the sangamon developed in loess indicate that the primary period of loess deposition was from 190 to 130 ka oxygen isotope stage ois6 that loess deposition continued intermittently from 130 to 74 ka ois5 and that deposition was wholly or in part coeval with loveland loess deposition in the central united states beryllium 10 chemical and pedologic data indicate that in the lower mississippi valley 1 the sangamon represents a minimum time period of 60 80 k y 2 there were at least two periods of soil formation ca 130 90 ka and 74 58 ka ois4 and 3 rates of weathering and pedogenesis equaled or exceeded the net loess accumulation rate until at least 46 ka ois3 and resulted in development of a paleosol in the overlying basal roxana silt along a n s transect from southern illinois to western mississippi sangamon macroscopic characteristics as well as the micromorphology chemistry and mineralogy suggest a regional paleoclimate during periods of soil formation that 1 was warm to hot with a wider range in temperature precipitation and evapotranspiration than present 2 had seasonal to decadal or longer periods of drought and 3 had down valley southward trends of increasing temperature and precipitation and decreasing seasonality and variation in annual to decadal precipitation

a loess paleosol record of climate and glacial history over the past two glacial interglacial cycles 150 ka southern jackson hole wyoming abstract loess accumulated on a bull lake outwash terrace of marine oxygen isotope stage 6 mis 6 age in southern jackson hole wyoming the 9 m section displays eight intervals of loess deposition loess 1 to loess 8 oldest each followed by soil development our age depth model is constrained by thermoluminescence meteoric 10 be accumulation in soils and cosmogenic 10 be surface exposure ages we use particle size geochemical mineral magnetic and clay mineralogical data to interpret loess sources and pedogenesis deposition of mis 6 loess was followed by a tripartite soil thin loess complex soils 8 7 and 6 apparently reflecting the large climatic oscillations of mis 5 soil 8 mis 5e shows the strongest development loess 5 accumulated during a glacial interval 76 69 ka mis 4 followed by soil development under conditions wetter and probably colder than present deposition of thick loess 3 43 51 ka mis 3 was followed by soil development comparable with that observed in soil 1 loess 1 mis 2 accumulated during the pinedale glaciation and was followed by development of soil 1 under a semiarid climate this record of alternating loess deposition and soil development is compatible with the history of yellowstone vegetation and the glacial flour record from the sierra nevada

ams radiocarbon age of the upper mississippi valley roxana silt abstract accelerator mass spectrometer radiocarbon ages of the roxana silt loess along the upper mississippi valley of wisconsin and minnesota indicate that loess sedimentation of the roxana silt occurred between about 55 000 and 27 000 14 c yr b p however due to local environmental controls the basal age at any given site may range from 55 000 to 35 000 14c yr b p the radiocarbon ages presented here are in agreement with previous radiocarbon ages for the roxana silt in its type area of west central illinois but indicate that long term sedimentation rates along the bluffline of the upper mississippi valley were very slow 4 8 cm 1000 yr compared to long term sedimentation rates along the bluffline of the type area 40 70 cm 1000 yr comparison of radiocarbon ages for midcontinent middle wisconsinan loess deposits indicates that sedimentation along the mississippi river valley may have preceded loess sedimentation along the missouri river valley by as much as 20 000 yr or that basal ages for middle wisconsinan loess along the missouri valley are erroneously young the bracketing ages for the upper mississippi valley roxana silt indicate that the mississippi river valley was receiving outwash sedimentation between 55 000 and 27 000 14c yr b p

absence of altonian glaciation in illinois abstract illinois was free of glacier ice from about 130 000 to 25 000 yr b p deposits of this time interval in northeastern illinois represented by core samples from test hole isgs s 30 are composed of leached nonglacigenic stratified or pedoturbated silty sediments that typically are organic rich and pedogenically modified these deposits overlie the sangamon soil which is identified by its stratigraphic position soil morphology and distinct alteration products in the clay mineral fraction including a variably swelling vermiculite like phase and a randomly interstratified kaolinite 10 a phase the regional extent of these deposits suggests that if altonian ice existed in the lake michigan basin it did not extend westward beyond the cuesta of silurian dolomite that rims the southwestern shore of lake michigan

stratigraphy and palaeoclimatic significance of late quaternary loess palaeosol sequences of the last interglacial glacial cycle in central alaska abstract loess is one of the most widespread subaerial deposits in alaska and adjacent yukon territory and may have a history that goes back 3 ma based on mineralogy and major and trace element chemistry central alaskan loess has a composition that is distinctive from other loess bodies of the world although it is quartz dominated central alaskan loess was probably derived from a variety of rock types including granites metabasalts and schists detailed stratigraphic data and pedologic criteria indicate that contrary to early studies many palaeosols are present in central alaskan loess sections the buried soils indicate that loess sedimentation was episodic or at least rates of deposition decreased to the point where pedogenesis could keep ahead of aeolian input as in china loess deposition and pedogenesis are likely competing processes and neither stops completely during either phase of the loess soil formation cycle loess deposition in central alaska took place before and probably during the last interglacial period during stadials of the mid wisconsin period during the last glacial period and during the holocene an unexpected result of our geochronological studies is that only moderate loess deposition took place during the last glacial period our studies lead us to conclude that vegetation plays a key role in loess accumulation in alaska factors favouring loess production are enhanced during glacial periods but factors that favour loess accumulation are diminished during glacial periods the most important of these is vegetation boreal forest serves as an effective loess trap but sparsely distributed herb tundra does not thus thick accumulations of loess should not be expected where tundra vegetation was dominant and this is borne out by modern studies near the treeline in central alaska much of the stratigraphic diversity of north american loess including that found in the central lowlands the great plains and alaska is explained by a new model that emphasizes the relative importance of loess production factors versus loess accumulation factors

paleoenvironmental interpretation of multiple soil loess sequence at milford reservoir northeastern kansas abstract a loess soil section near the republican river in northeastern kansas includes three superposed soils paleosols in at least three superposed loess units including peoria loess pl the gilman canyon formation gcf and loveland loess ll the gcf coincides with a composite soil with a 1 3 m thick buried organic rich a horizon that yields ams radiocarbon ages from 30 3 to 22 4 ka or 35 7 to 26 9 ka when calibrated that overlies a 1 6 m oxidized b horizon complex the b subhorizons stratigraphically and morphologically resemble the reddish pedocomplex described elsewhere in kansas and illinois that dates between about 69 and 35 ka the upper ll yields a tl age of about 136 and 130 30 ka thus pl the gcf and ll were probably deposited mainly during the late wisconsinan middle wisconsinan and illinoian oxygen isotope stages ois 2 3 and 6 or about 12 to 24 24 to 60 and 130 to 188 ka respectively soils 1 2 and 3 then formed mainly during ois stages 1 3 and 5 respectively or about 12 to 12 60 to 60 and 73 to 130 ka in comparison with other dated stratigraphic sections in the great plains soils paleosols have relatively simple cumulic horizon sequences as is typical at sites distal from principle loess source regions nonetheless they record a complex pedosedimentary history that reflects climatically driven variations in rates of sedimentation and pedogenesis soil 1 is an udic argiustoll with 21 cm a mollic 69 cm bt argillic 60 cm bk horizons that formed under modern type grassland and climate soil 3 the sangamon paleosol includes a 3 m thick highly rubified and clay rich argillic horizon that based on its morphological properties probably formed under a relatively warm moist equable climate and deciduous type forest soil 2 coincides with the gcf and as such is a pedolithostratigraphic unit that includes a 1 3 m mollic horizon and to 1 6 m oxidized 3btb and 3bcb horizons whereas the oxidized b horizons apparently represent relatively warm moist climatic conditions between about 65 to 35 ka the upper cumulic mollic a horizons of the gcf probably formed under progressively cooling climate and grassland between about 35 7 and 26 9 calibrated radiocarbon ka estimated mean accumulation rates mars of loess range from 0 12 m k yr for the gcf to about 0 5 m k yr for pl

liquefaction susceptibility mapping in the city of memphis and shelby county tennessee abstract earthquake induced sand dikes have been identified in cut banks of the wolf and loosahatchie rivers in the city of memphis and shelby county tennessee most of the dikes are near the mouths of these rivers within the city limits of memphis but one dike occurs 36 km upstream in the bank of the wolf river in collierville the dikes range in width from 1 to 50 cm and at some localities can be traced vertically as much as 4 m from their source bed to within 50 cm of the flood plain surface the age of the dikes is unknown but they are interpreted to be from the great 1811 1812 new madrid earthquakes because they are locally buried by historical sediments containing bricks the larger number of dikes and upstream extent of liquefaction along the wolf river suggests that liquefaction susceptibility is greater in the wolf river flood plain than in other flood plains in shelby county this greater liquefaction susceptibility of the wolf river flood plain appears to be due to the sand in its basal point bar sequence and a relatively thin overbank silt clay cap geologic and geologically based liquefaction susceptibility maps 1 24 000 were made of the memphis northwest and collierville 7 5 quadrangles of shelby county the liquefaction susceptibility maps show very high susceptibility for mississippi wolf and loosahatchie river flood plains high susceptibility in areas of artificial fill on these three flood plains moderate susceptibility along other flood plains and terraces in these quadrangles and low susceptibilities in the interfluve areas

stratigraphy and chronology of mississippi valley loess in western tennessee the stratigraphy and chronology of loess deposits in the mississippi valley provide an important proxy record of the number and timing of glacial advances into the upper mississippi drainage basin the stratigraphy of loess and paleosols from two exposures in northwestern tennessee reveals three major loess units that are correlated with the loveland loess roxana silt and peoria loess from oldest to youngest detailed measurements of clay and secondary pedogenic iron contents suggest that the loveland loess may consist of multiple loess units which have been pedogenically welded to one another to form a composite sangamon soil the mineralogy of the coarse silt fraction from one exposure reveals both primary mineralogical differences between the peoria loess and the roxana silt and pedogenic overprinting by the sangamon soil grain size and iron data suggest that the degree of pedogenic alteration increases from west to east away from the loess source area which probably reflects the role of sedimentation rate on the degree of pedogenic alteration of loess however only the peoria loess shows the expected exponential eastward decrease in thickness the thickness of older loess units appears to be controlled more by the occurrence of localized erosion than by distance from source area most samples are resistant to solar resetting of the thermoluminescence signal which if unrecognized could yield thermoluminescence ages that significantly underestimate the true age of the deposits the best match between thermoluminescence age using the total bleach method and radiocarbon age of the peoria loess and roxana silt is achieved when either long durations of optical bleaching by sunlight 32 hr or artificial ultraviolet uv light are applied to define the residual thermoluminescence level partial bleach analysis indicates that long duration optical bleaching by sunlight or uv lamp bleaching does not systematically overbleach samples of peoria loess and roxana silt three thermoluminescence age estimates between 38 4 1 and 53 5 ka from the basal half of the roxana silt and six age estimates between 18 2 and 25 3 ka from the basal half of the peoria loess are consistent with numerous finite radiocarbon dates from around the central mississippi valley thermoluminescence age estimates suggest that the oldest of the intra loveland loess units is 127 12 ka one age and may have been deposited during marine oxygen isotope stage 6 the younger two of these loess units were deposited between 113 10 and 70 6 ka three ages this latter age range for loess that underlies the top of the presumed sangamon soil is problematic because it requires that pedogenesis may have begun as late as approximately 70 ka moreover loess deposited between about 120 and 70 ka suggests that the southern margin of the laurentide ice sheet was within some part of the upper mississippi valley during this interval this conflicts with some glacial geologic evidence but it is consistent with global sea level and 18o records of ice volume which indicate several intervals of moderate glaciation during this time

continuity of the reelfoot fault across the cottonwood grove and ridgely faults of the new madrid seismic zone previous investigators have argued that the northwest striking reelfoot fault of northwest tennessee and southeastern missouri is segmented one segment boundary is at the intersection of the northeast striking cottonwood grove and ridgely strike slip faults with the reelfoot fault we use seismic reflection and geologic mapping to locate and determine the history of the reelfoot south fault across this boundary zone one reflection profile revealed a southwest dipping 81 reelfoot south reverse fault that displaces the top of the paleozoic 65 m cretaceous 40 m paleocene 31 m eocene wilcox group 20 m and eocene memphis sand 16 m a second reflection profile reveals a north dipping 84 reverse fault 4 3 km south of the reelfoot south fault which defines the southwest margin of the tiptonville dome a geologic profile of the base of the 3 1 ma upland complex mississippi river terrace alluvium within the mississippi river bluffs reveals 6 m of displacement across the reelfoot south fault similarly quaternary stream terrace distribution suggests 6 m of reelfoot south hanging wall tiptonville dome uplift that is probably holocene fault strike trends show the reelfoot fault and its hanging wall tiptonville dome are not laterally offset across the cottonwood grove and ridgely faults the reelfoot south fault northwest and southeast of the cottonwood grove and ridgely faults has very similar vertical displacement on common stratigraphic marker horizons in the upper 900 m these data indicate the reelfoot fault tiptonville dome has acted as one continuous fault zone across the cottonwood grove and ridgely faults since late cretaceous

new insights on illinoian deglaciation from deposits of glacial lake quincy central indiana abstract the deposits of glacial lake quincy overlie a diamicton associated with the classically defined illinoian limit in central indiana this lake covered at least 180 km 2 with a depth of 20 m and developed when the illinoian ice sheet retreated 15 km from the maximum limit causing lake impoundment against devore ridge overflow from glacial lake quincy eroded across the ridge forming a number of steeped walled outlets a section along mill creek exposes a sedimentologic sequence associated with glacial lake quincy from a subglacial diamicton to ice proximal to ice distal glacial lacustrine sediments we report new optical ages by multiple aliquot regenerative dose procedure for the fine grained rhythmically bedded sediments presumed to represent the lowest energy depositional facies dominated by suspension settling which maximized sunlight exposure in turn optical ages were determined on the fine grained 4 11 m polymineral and quartz fractions under infrared and blue excitation which yielded statistically similar ages optical ages span from ca 170 to 108 ka with the average of 16 optical ages indicating deglaciation at ca 135 ka generally coincident with marine oxygen isotope stage 6 to 5 transition and rise in global sea level

a multi proxy palaeoecological and palaeoclimatic record within full glacial lacustrine deposits western tennessee usa the fulton section along the mississippi river in western tennessee usa is a 1 km continuous exposure 20 m vertically of quaternary fluvial and lacustrine deposits inset within eocene sediments and buried by thick loess fossiliferous slackwater lake sediments record maximum aggradation during the last two major glaciations with deposition between ca 190 140 ka and q1 24 18 14 c ka bp based on amino acid and radiocarbon chronology respectively during the onset of full glacial conditions ca 24 22 14 c ka bp a relatively permanent shallow lake environment is indicated by ostracodes aquatic molluscs and both pollen and macrofossils of aquatic plants by 21 8 14 c ka bp increasing emergent plants amphibious gastropods pomatiopsis and heavier d 18 o compositions suggest marsh like conditions in a periodically drying lake the surrounding uplands consisted of picea pinus woodlands mixed with cool temperate hardwoods e g quercus populus carya grasses and herbs more open conditions ensued ca 20 14 c ka bp with loess and slopewash gradually infilling the former lake by 18 14 c ka bp modern analogue analyses of ostracodes and palaeontological evidence imply a full glacial climate similar to today s mixed boreal zone in central minnesota usa about 98c cooler in mean annual temperature than present day western tennessee copyright 2009 john wiley sons ltd

geochemistry and mineralogy of late quaternary loess in the upper mississippi river valley usa provenance and correlation with laurentide ice sheet history abstract the midcontinent of north america contains some of the thickest and most extensive last glacial loess deposits in the world known as peoria loess peoria loess of the upper mississippi river valley region is thought to have had temporally varying glaciogenic sources resulting from inputs of sediment to the mississippi river from different lobes of the laurentide ice sheet here we explore a new method of determining loess provenance using k rb and k ba values in k feldspars and micas in loess from a number of different regions in north america results indicate that k rb and k ba values can distinguish loess originating from diverse geologic terrains in north america further different loess bodies that are known to have had the same source sediments using other criteria have similar k rb and k ba values we also studied three thick loess sections in the upper mississippi river valley region at each site the primary composition of the loess changed over the course of the last glacial period and k rb and k ba values parallel changes in carbonate mineral content and clay mineralogy we thus confirm conclusions of earlier investigators that loess composition changed as a result of the shifting dominance of different lobes of the laurentide ice sheet and the changing course of the mississippi river we conclude that k rb and k ba values are effective robust and rapid indicators of loess provenance that can be applied to many regions of the world

stratigraphy and structure of the eocene memphis sand above the eastern margin of the reelfoot rift in tennessee mississippi and arkansas usa in total 1249 geophysical well logs were interpreted to map the stratigraphy and structure of the eocene memphis sand in west tennessee northwest mississippi and crittenden county arkansas where it overlies the southeastern margin of the reelfoot rift the memphis sand is a 300 m thick reworked fluvial sand deposited on a low relief subsiding plain with limited accommodation space the memphis sand has experienced syn and postdepositional faulting of four types in the region 1 west trending grabens were active during eocene claiborne deposition these grabens also appear to control modern drainage and thus may extend to the surface 2 the n33 e shelby faults pass through shelby county tennessee into northwest mississippi and extend to or near the surface they were right lateral normal faults during eocene memphis sand deposition but they became inverted reverse faults in the late eocene 3 the n67 e striking gibson faults are high angle normal and reverse faults with a component of right lateral strike slip these faults were active during memphis sand through lower cockfield deposition north of the hatchie graben and appear to be due to faulting above an outboard fault of the reelfoot rift 4 the n43 e striking lauderdale faults are high angle normal and reverse faults that reflect right lateral strike slip reactivation of the southeastern margin of the reelfoot rift the structure and stratigraphy revealed in this mapping indicate that the geology of the memphis sand is more complex than previously recognized faulting of the memphis sand and overlying sediments reveals potentially seismogenic faults in western tennessee eastern arkansas and northwestern mississippi this study provides fundamental data for future groundwater modeling and seismic hazard analysis

paleopedology plus tl 10be and 14c dating as tools in stratigraphic and paleoclimatic investigations mississippi river valley u s a thick 35 m loess deposits are present on ridges and high bluffs in the northern half of the lower mississippi valley lmv u s a detailed descriptions of the loess sections and pedologic physiochemical and mineralogic analyses and tl 14c and 10be age determinations allow preliminary paleoclimatic reconstructions for the late quaternary of central north america no age data are available for the oldest fifth loess 10be and tl age data suggest a 250 200 ka age for the fourth or crowleys ridge loess and indicate that the loveland or third loess is time equivalent to oxygen isotope stage 6 190 120 ka a weakly developed paleosol is present in the basal half of the loveland the sangamon geosol is present in the upper 5 m and represents all of oxygen isotope stage 5 130 60 ka it formed in a climate as warm as but drier and or with greater variation in precipitation than the present the roxana silt second loess was deposited during oxygen isotope stages 4 and 3 65 26 ka the early wisconsinan interglacial glacial transition represented by the sangamon geosol and the unnamed paleosol in the basal roxana silt was slow the paleoclimate during the 35 k yr of roxana deposition was cool to cold and wet age and pedologic data indicate that deposition of the peoria loess the youngest began around 25 ka when the area s climate changed abruptly from cool or cold and wet to cold and dry with periods of sustained high winds

dental anatomy of the apex predator sinraptor dongi theropoda allosauroidea from the late jurassic of china the dental morphology of the holotype of the theropod sinraptor dongi from the jurassic shishugou formation of china is comprehensively described we highlight a combination of dental features that

loess stratigraphy in central china abstract the loess deposits in central china record world wide climate changes of the last 2 5 ma numerous climatic oscillations are marked by alternating loess and soil units with continuous coverage of the matuyama and brunhes epochs magnetic susceptibility of the deposits correlates closely with the oxygen isotope record of the deep sea sediments and provides an independent measure of climate and time the key marker bed of the chinese loess sequence is the paleosol s5 the time equivalent of the mid brunhes oxygen isotope stages 13 14 and 15 it marks a prolonged interval of warm humid climate lasting from approximately 615 to 470 thousand years ago several episodes of river downcutting coincide with deposition of the exceptionally thick loess units l1 oceanic oxygen isotope stages 2 to 4 l2 stage 6 l5 stage 12 l6 stage 16 l9 stage 22 l15 stage 38 about 1 15 ma and ws4 about 2 3 ma these erosional events are interpreted as a result of episodic uplift of the loess plateau the deposition of the earliest loess layers between 2 5 and 2 3 ma ago marks a first order shift from warm and humid environments toward harsh continental steppes comparable to those of the middle and late pleistocene little if any lithologic or paleontologic changes were noted within or above the olduvai magnetozone so that the proposed plio pleistocene boundary at approximately 1 65 ma has no lithostratigraphic and biostratigraphic representation in the chinese loess series comparison with the deep sea drilling program core 552a in the north atlantic and with the santerno river section near bologna shows that the occurrence of the earliest loess in china coincides with the timing of the first significant ice rafting in the north atlantic and with the appearance of cold water foraminifers in the marine deposits of northern italy an extension of the stage system of the oxygen isotope signal extended back to the gauss matuyama boundary is proposed

allochthonous surface alteration of ni laterites abstract lateritic weathering sections over ultramafic rocks in burma puerto rico venezuela malagasy and brazil display anomalous chemical variations in their upper parts these variations are not due to weathering of ultramafics but to the addition of varying amounts of weathered material from other rocks this contribution can cause a considerable increase in si al ti and zr and decrease in fe cr and ni in the surficial parts of the limonite zone in other occurrences the admixture of foreign material can only be recognized by strongly elevated ti and zr amounts in surface layers which is atypical for ultramafic rocks and their weathering products in most of the occurrences the foreign material was probably transported by colluvial alluvial processes but an eolian derivation is also possible sedimentary processes may cause large amounts of foreign material to be mixed with ni limonite smaller amounts of foreign clayey material can also be washed downwards into clearly autochthonous limonite the ni laterite deposit on the tagaung taung burma which has been explored in detail by drill holes provides an excellent example for the processes discussed above which can also influence the composition of the weathering mantle above other parent rocks

last glacial loess in the conterminous usa the conterminous united states contains an extensive and generally well studied record of last glacial loess the loess occurs in diverse physiographic provinces and under a wide range of climatic and ecological conditions both glacial and non glacial loess sources are present and many properties of the loess vary systematically with distance from loess sources united states midcontinent last glacial loess is probably the thickest in the world and our calculated mass accumulation rates mars are as high as 17 500 g m 2 yr at the bignell hill locality in nebraska and many near source localities have mars greater than 1500 g m 2 yr these mars are high relative to rates calculated in other loess provinces around the world recent models of last glacial dust sources fail to predict the extent and magnitude of dust flux from the mid continent of the united states a better understanding of linkages between climate ice sheet behaviour routing of glacial meltwater land surface processes beyond the ice margin and vegetation is needed to improve the predictive capabilities of models simulating dust flux from this region r 2003 elsevier ltd all rights reserved

location and expression of fragic soil properties in a loess covered landscape southern illinois usa abstract fragic soil properties often develop in thin loess units overlying residual parent materials in the midwest usa morphologic indicators of these fragic properties are often weakly expressed making consistent mapping of soils difficult this study was initiated in a small watershed in union county illinois to determine location and degree of development of fragic materials and fragipans on the landscape we also sought to assess factors influencing the degree of expression of these features and document accessory soil properties that reflect the presence of these fragic soil materials nine pedons from two catenas were sampled and selected chemical physical and mineralogical analyses were conducted results indicate that loess thickness across the watershed ranged from about 2 to 4 m fragic soil properties were observed in argillic horizons on side slope and head slope geomorphic components at depths ranging from 51 to 111 cm depths to horizons meeting fragipan criteria ranged from 140 to 175 cm discontinuity between two loess units peoria and roxana silts was verified by both particle size analysis fine coarse silt ratios clay free fine and coarse silt and magnetic susceptibility these data suggest that the development of fragic soil properties is not controlled solely by the discontinuity between loess deposits fragipans are weakly developed based on rupture resistance morphological features such as structure bulk density

soil evolution over the quaternary period in a mediterranean climate se spain palaeosols in the granada basin se spain have been studied in two different situations surface soils on geomorphically stable surfaces since the early pleistocene with younger pedogenic overprinting and buried soils on unstable surfaces from the middle late pleistocene on which successive erosional depositional episodes have alternated with pedogenic episodes for each soil clay and iron accumulation indices the fet alt sit ratio clay mineralogy and micromorphological features were used to estimate the degree of soil development from the early to the early late pleistocene the main pedogenic processes were the leaching of carbonates weathering illuviation and rubification which resulted in bt horizons with red colours clay texture clay coatings and kaolinite neoformation the degree of weathering and the development of these bt horizons varied over time and the soils that formed on the surfaces from the early pleistocene show strongest weathering and development however after their formation there were periods in which they were partially truncated and recalcified resulting in polygenetic soils the different degrees of development of the buried soils during the last 474 000 years indicate that the wettest warm period was stage 7 and the driest stage 5 stages 9 and 11 must have had climates with intermediate wetness since the clay accumulation and iron oxide accumulation indices the differences in fet alt sit ratio between bt and c horizons the extent of kaolinite neoformation and the micromorphological features of the soils formed during stage 7 are all similar to the surface soils that formed on early pleistocene deposits these features cannot be used to date surfaces older than 242 000 bp by contrast the soils that formed during stage 7 and later periods show different extents of development and thus can be used for the approximate dating of landforms d 2002 elsevier science b v all rights reserved

episodic holocene loess deposition in central nebraska abstract the mirdan canal section in central nebraska usa provides evidence for multiple episodes of holocene loess deposition in the central great plains this irrigation canal cut exposes more than 4 m of holocene sediment that overlies the late wisconsinan peoria loess the oldest holocene sediment is local slopewash that fills gullies but overlying beds are interpreted as holocene loess bignell loess three buried soil profiles occur within the holocene sediment and have yielded uncalibrated 14 c ages of 3010 yr bp uppermost buried soil and 8790 yr bp third buried soil from top a fourth buried soil yielded an age of 9330 yr bp and is correlated with the brady soil the bignell loess has a darker color slightly more organic matter more clay more coarse silt and sand less smectite and less volcanic glass than the underlying peoria loess the bignell loess is most plausibly interpreted as dust from local flood plains containing a mixture of reworked peoria loess and older silts with contrasting mineralogy episodes of loess deposition occurred in the early middle and late holocene probably during periods of dry climate but possibly also as a consequence of large erosive floods that made wind erodible sediment available on nearby flood plains

stratigraphy geochemistry and thermoluminescence ages of lower mississippi valley loess four periods of loess deposition in the lower mississippi valley can be identified on the basis of geochemical and mineralogical criteria radiocarbon dating and thermoluminescence dating these are designated loess units 1 2 3 and 4 in order of increasing age carbonate rich unit 1 loess comprises more than 70 per cent of the thickness of the loess profiles 14c and tl dates indicate this loess was deposited between 9 000 and 20 000 years ago a maximum sedimentation rate of 2 17 mm yr 1 has been recorded near vicksburg just after the last laurentide glacial maximum between 17 190 and 15 580 years ago the unit 2 loess which is thin and partly decalcified was deposited slowly between about 25 000 and 20 000 years ago the unit 3 and unit 4 loess formations which are both highly weathered have yielded tl ages of 76 000 85 000 years and 119 000 132 000 years suggesting they were deposited during the altonian substage of the early wisconsinan and the illinoian glacial stage respectively the four loess units are stratigraphically equivalent to the peoria farmdale roxana and loveland loess formations previously recognized in illinois the source of dust in both areas was glacial outwash in the mississippi valley during interglacials and interstadials when the supply of glacial debris was reduced and the mississippi river changed from a braided to a meandering regime dust sedimentation in southern mississippi virtually ceased allowing weathering and pedogenesis to proceed

the record of major quaternary sea level changes in a large coastal plain estuary chesapeake bay eastern united states abstract seismic reflection surveys of the chesapeake bay combined with geologic mapping and analysis of boreholes on the delmarva peninsula provide evidence of at least three generations of the susquehanna river system and three generations of the chesapeake bay the evidence for ancient courses of the susquehanna river is preserved as three distinct paleochannels and evidence for ancient versions of the chesapeake bay is preserved as three sets of paleochannel fill beneath the bay and three generations of barrier spit deposits on the southern delmarva peninsula the paleochannels represent relative sea level minima and the channel fill and barrier spit deposits represents relative sea level maxima a history of three major marine transgressions is recorded in the stratigraphy preserved in the filled paleochannels and in the overlying barrier spit complexes three systematic progressions from fluvial to estuarine to bay or nearshore marine environments this sea level record seems to be compatible with the saw toothed pattern of the marine oxygen isotope record and with the concept of glacial interglacial terminations it also seems to have a climax character in which most of the preserved evidence is related to the largest terminations and to the extreme sea level positions that bound those terminations the three paleochannel fill and barrier spit complexes appear to correspond to oxygen isotope stages 1 5 and either 7 or 11 the three related paleochannels correspond to stages 2 6 and either 8 or 12

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

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

long quaternary record in eastern washington u s a interpreted from multiple buried paleosols in loess loess that is from a few meters to 75 m thick covers an area of more than 20 000 km2 on the columbia plateau in washington idaho and oregon the region of deepest loess is in eastern washington and is called the palouse the palouse is downwind of the channeled scabland through which massive outburst floods from glacial lake missoula flowed repeatedly during glacial stages of the pleistocene the deepest stratigraphic section yet studied is in a remnant of the once continuous loess cover that is surrounded by scabland channels a normal over reverse magnetic polarity zonation in this section supports an age of more than 790 000 yr but 15 35 m of loess may be present beneath this section so a total of 1 5 2 million yr is possible upward fining of texture in some layers in the loess at this site and stratigraphic evidence at nearby sites suggest that at least some pulses of loess deposition were triggered by episodes of cataclysmic floods nineteen or more individual paleosols can be recognized in 26 m of section based on field morphology physical and chemical properties and micromorphology the paleosols consist of calcic petrocalcic and duripan horizons many of which are associated with cambic horizons less strongly developed soils in this and other sections have been obscured by partial overlap of soil development in an episodically rising loess landscape paleosols in the loess at other sites reflect a dry to moist climatic gradient from west to east across the region during the pleistocene that was grossly similar to today s accumulation of pedogenic carbonates and silica dominates in a western zone where the present day mean annual precipitation is less than about 450 mm translocation of silicate clays and leaching of carbonates dominate in a central steppe zone where precipitation is between 450 and about 700 mm fragipans are common in an eastern zone along the steppe forest transition at present day precipitation of over 700 mm reconnaissance study suggests that these climatic pedogenic zones have been somewhat stable during many of the episodes of soil development preserved in the loess although some paleosols have different features from the majority of the paleosols in that zone e g paleosols with fragipans in a sequence of paleosols with argillic horizons which suggests that some episodes of soil development took place under different climatic conditions

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr