pedogenic carbonate proxies for amount and seasonality of precipitation in paleosols the depth to carbonate nodular bk horizon in soils d in cm is correlated with mean annual precipitation p in mm so that bk horizons are deep in subhumid regions but shallow in semiarid regions previous quantifications of this relationship are unchanged by this new compilation of 807 soils p 137 24 6 45 d 0 013 d 2 where r 2 0 52 and standard error s e 147 mm in most north american postglacial soils the bk horizon is thin and well defined whereas in monsoonal tropical soils of pakistan and kenya the bk horizon is thick and diffuse data from 675 modern soils define the relationship between the thickness of soil with nodules t in cm and mean annual range of precipitation m in mm difference between monthly means of wettest and driest months m 0 79 t 13 71 where r 2 0 58 and s e 22 mm the relationship between carbonate nodule size s in cm and soil age a in ka is quantified by 9 radiocarbon dated soils from las cruces new mexico a 3 92 s 0 34 where r 2 0 57 and s e 1 8 k y these transfer functions are applied to reconstructing paleoclimatic change from paleocene eocene paleosols of the north horn formation and flagstaff limestone of axhandle canyon utah the terminal paleocene spike of warmth recorded by fossil plants in nearby wyoming was coincident with a brief peak in both mean annual precipitation and mean annual range of precipitation in utah

holocene paleoceanography of the northwest passage canadian arctic archipelago abstract a series of cores box and piston were collected at 2 key locations in lancaster sound cores 2004 804 009 bc and pc and barrow strait cores 2005 804 004 bc and pc in the canadian arctic archipelago to document the evolution of sea surface conditions in the main axis of the northwest passage during the holocene time period reconstruction of sea surface parameters summer temperature and salinity duration of sea ice cover were estimated based on transfer functions using dinoflagellate cyst assemblages as proxy indicators the chronology of these cores is based on calibrated ams 14c dates 210pb analyses and correlations between paleomagnetic secular variations of the geomagnetic field and a predicted spherical harmonic model of the geomagnetic field cals7 k 2 our age models for both cores indicate that 009 pc spans the last 11 100 cal bp while 004 pc encompasses the last 10 800 cal bp calculated sedimentation rates are in the range of 43 140 cm kyr for core 009 pc and 15 118 cm kyr for core 004 pc allowing for a millennial time scale resolution in each core our results indicate relatively harsh conditions in lancaster sound between 10 800 and 9000 cal bp summer temperatures 2 c cooler than at present which we associate with the presence of active ice streams in northernmost baffin bay and a weak west greenland current this is followed by a warming trend up to 3 c higher than present that took place between 8500 and 5500 cal bp which we associate with the holocene thermal maximum and to a large scale atmospheric pattern such as the arctic oscillation operating at the millennial time scale this is concomitant with an increase in the relative abundance of phototrophic dinoflagellate cyst taxa a gradual cooling of sea surface temperature and increased sea ice follow this from 5500 cal bp until the modern period in barrow strait harsh sea surface conditions prevailed from 11 100 to 5500 cal bp with summer temperatures as low as 4 c cooler than at present the warming trend occurred later in this region between 5500 and 1000 cal bp after which a gradual cooling is observed until the modern period the apparent shift or opposite warming trends between lancaster sound and barrow strait after 5500 cal bp could be the result of a change in atmospheric circulation patterns related to a possible shift in the ao mode from ao to ao comparison of ice core 18o record from devon island ice cap and the reconstructed sea surface temperature from core 009 pc suggests a strong atmospheric oceanic coupling throughout the holocene in this area

late wisconsinan glaciation of amund and ellef ringnes islands nunavut evidence for the configuration dynamics and deglacial chronology of the northwest sector of the innuitian ice sheet geomorphic and chronologic evidence from amund and ellef ringnes islands documents the configuration dynamics and collapse of the northwest sector of the innuitian ice sheet these data record the inundation of the ringnes islands by northwestward flowing ice from divides spanning the alpine and lowland sectors of the innuitian ice sheet ice flow indicators and granite dispersal along eastern amund ringnes island suggest massey sound was filled by an ice stream discharging coalescent alpine and lowland ice from norwegian bay in contrast the interior of amund ringnes island was overridden by predominantly non erosive granite free ice from a divide in the lowland sector of the ice sheet glacial landforms on ellef ringnes island record coverage by largely non erosive ice but it remains uncertain whether these features relate to northward flowing lowland ice or a cold based local ice cap deglaciation of the ringnes islands commenced 10 000 14c years ago deglacial dates between 9 7 and 9 2 ka bp rec

holocene delevelling of devon island arctic canada implications for ice sheet geometry and crustal response the raised beaches and deltas of devon island contain an abundance of dateable materials a large set of radiocarbon dates 228 154 of which are new are used to construct relative sea level curves and isobase maps for the island the best materials for this purpose are driftwood logs 61 dates and bowhead whale bones 74 dates from raised beaches and mollusc shells from marine limit deltas 20 dates or from altitudes close to marine limit 14 dates during the last glacial maximum the island is thought to have lain beneath the southeastern flank of the innuitian ice sheet the relative sea level history is congruent with that inferred ice configuration the island spans half the ice sheet width relative sea level curves are of simple exponential form except near the glacial limit where an early holocene emergence proceeded to a middle holocene lowstand below present sea level which was followed by submergence attending the passage of the crustal forebulge the response times of relative sea lev

deciphering patterns of postglacial sea level at the junction of the laurentide and innuitian ice sheets western canadian high arctic abstract recent sampling of deglacial and postglacial raised marine sediments across melville and eglinton islands in the western canadian high arctic yielded over 200 new radiocarbon dates on molluscs driftwood and other organic materials from this database eight relative sea level curves and an isobase map for the 9 5 cal ka bp shoreline were constructed the forms chronology and pattern of the relative sea level curves across the study area reflect the complex glacial history of this region including the asynchronous retreat of the formerly coalescent laurentide and innuitian ice sheets zone i relative sea level curves which show continuous emergence to present were observed in areas closer to greater last glacial maximum ice sheet loading at more distal sites transitional zone i ii curves display emergence followed by submergence in the mid to late holocene still ongoing related to forebulge migration and collapse an independent record of late holocene submergence is provided by radiocarbon dated driftwood which is accumulating at modern sea level due to re deposition during transgression geomorphic evidence of submergence at the modern coastline is widespread but does not distinguish areas that experienced a late holocene lowstand and subsequent transgression from those that are currently at their lowstand of special interest are the relative sea level histories of two areas that experienced earlier deglaciation by the laurentide ice sheet while remaining in the peripheral depression of the more stable and adjacent innuitian ice sheet the flat topped relative sea level curves from these sites appear to record unusually slow rates of glacioisostatic emergence for 1500 years immediately following deglaciation the relative sea level data presented in this paper provide important comparisons for sea level models which have been shown to fit poorly with previously published data from this region

subterranean ant nests trace fossils past and future many species of ants excavate complex species typical nests in soil the basic structural units of many nests are descending tunnels connecting flattened generally horizontal chambers of oval to lobed outline the species typical structure of many nests results from variation in the size shape number and arrangement of these basic elements nest architecture can be rendered by filling subterranean nests with a thin slurry of orthodontal plaster then excavating and reconstructing the hardened cast photographs of such nest casts of nine species of ants from northern florida show the range and type of variation of architecture preservation conditions under which ant nests could form complex trace fossils are discussed and reports of such traces reviewed the images presented in this paper will help to alert trace fossil specialists to the potential range of appearance of such nest fossils 2002 elsevier science b v all rights reserved

the identification and interpretation of reptile ichnofossils in paleosols through modern studies abstract the soil ecosystems of modern floodplains of north america south america the caribbean africa europe and western asia are the habitat of a group of limbless fossorial reptiles order amphisbaenia although body fossils are relatively abundant in north american paleocene and neogene paleosols no ichnofossils are attributed to these organisms largely because the morphologies present in modern burrows have not been studied because ichnofossils tend to have a higher preservation potential than body fossils knowledge of the architectural and surficial burrow morphologies of such burrowing vertebrates as amphisbaenians can lead to the knowledge of their true stratigraphic and geographic ranges the behavioral responses of a common south american amphisbaenian to variations in soil composition moisture and cohesion were studied in the laboratory so that the architectural and surficial morphology of their burrows could be tied to these environmental changes qualitative and quantitative models were designed to describe the morphology of the amphisbaenian burrows and then used to distinguish them from other floodplain burrowers including skinks scorpions and crayfish amphisbaenians were found to produce unique two and three dimensional biogenic structures that could be both distinguished from those of other organisms and tied to specific environmental conditions from these data variations in the morphology of amphisbaenian ichnofossils can provide more accurate interpretations not only of the paleoecology paleoenvironment and paleoclimate of floodplain paleosols but also of rates of sedimentation

predatory digging behavior by dinosaurs minimal direct evidence exists in the rock record of dinosaurs and mammals behaving as predators and prey respectively a newly discovered late cretaceous trace fossil association of digging traces of maniraptoran theropod dinosaurs and mammalian den complexes indicates a predator prey relationship three distinct associated trace fossils occur within a floodplain siltstone mudstone bed of the upper cretaceous wahweap formation in southern utah united states one trace fossil morphology and its extramorphological variants record digging by a maniraptoran theropod dinosaur possibly a dromeosaurid or troodontid the other two are interpreted as mammalian den complexes the proximal association of these trace fossils suggests that dinosaurs used excavation techniques to prey on mammals

quaternary ice transport in the canadian arctic and extent of late wisconsinan glaciation in the queen elizabeth islands most of the ice rafted debris in channels off the queen elizabeth islands nunavut is of local origin particularly in the inner part of the archipelago but samples from the arctic shelf contain as much as 40 grains from sources as far away as 2000 km including the siberian shelves particle transport by drifting sea ice from distant shelves is an important process on the arctic continental shelf of the queen elizabeth islands in the interior of the queen elizabeth islands and in the viscount melville and lancaster sounds particle transport is limited to distances of approximately 200 km mixing is more common among grains of coarse silt to fine sand than in the 250 m fraction but even the latter contains debris from sources far apart during the late wisconsinan the northern southern and eastern queen elizabeth islands were covered by glaciers flowing radially from ice centers on the islands into the inter island channels queens channel was completely filled by ice and a glacier lobe moved

helical burrows as a palaeoclimate response daimonelix by palaeocastor the extra effort needed to dig a helical burrow versus a straight burrow with the same passage radius has been quantified in an equation that depends only on the angles of incline for the helical burrows daimonelix of the miocene beaver palaeocastor fossor extra and or unusual effort was needed for the helical passage versus a straight passage that effort for the helical passage was probably not justified to avoid the small likelihood of burrow interference by straight passages among closely packed burrows since there was already a greater chance but so far unobserved of interference with their living chambers which had a larger diameter and a smaller average angle of incline that effort was probably not justified either as a deterrent to predators since smaller predators such as zodiolestes daimonelixensis have already been found in these helical burrows the type of beaver remains found in the burrows suggest predation and the great and consistent depth would not have been needed helical burrows are more likely a response to palaeoclimates since the extra and or unusual effort for helical passages did result in corresponding increases in both burrow subsurface air volume and burrow wall surface area and or in limiting air circulation which would have provided the environmental advantages of increased heat loss or gain resulting in more consistent subsurface temperature and humidity when there were seasonal or extreme surface conditions

synapsid burrows and associated trace fossils in the lower jurassic navajo sandstone southeastern utah u s a indicates a diverse community living in a wet desert ecosystem abstract enigmatic structures in the lower jurassic navajo sandstone near moab utah occur at three localities below carbonate beds that record interdune lake deposits these structures are interpreted as mammal and therapsid burrows based on their architectural and surficial burrow morphologies type i large diameter and type ii mega diameter burrows type i burrows include sinuous tunnels y and t branched tunnels sinuous ramps and chambers and weather into mounds averaging 33 m 22 m and extend 1m above the surface type i burrows are dorsoventrally flattened in cross section averaging 9 3 cm wide and 4 2 cm high and are sand filled and structureless type i burrows mostly have smooth walls though some have scalloped walls type ii burrows are simple inclined tunnels 35 cm wide and 20 cm high and exhibit well preserved bilobate morphology along the underside of the tunnel the walls preserve a series of 3 or 4 thin 4 8 mm inclined scratch marks from the upper part of the wall and along the floor the great complexity and high density of type i burrow systems is best explained by multiple individuals living together in social groups these burrows are more complex than early triassic therapsid burrows from south africa and are most similar to burrows of extant social e g voles and eusocial mammals e g naked mole rats type ii burrows were likely constructed by therapsids based on burrow size and comparison to permian and triassic therapsid burrows from south africa and antarctica

the laurentide and innuitian ice sheets during the last glacial maximum the late wisconsinan advance of the laurentide ice sheet started from a middle wisconsinan interstadial minimum 27 30 14 c ka bp when the ice margin approximately followed the boundary of the canadian shield ice extent in the cordillera and in the high arctic at that time was probably similar to present ice advanced to its late wisconsinan stage 2 limit in the northwest south and northeast about 23 24 14 c ka bp and in the southwest and far north about 20 21 14 c ka bp in comparison to some previous reconstructions of ice extent our current reconstruction has substantially more late wisconsinan ice in the high arctic where an innuitian ice sheet is generally acknowledged to have existed in the atlantic provinces where ice is now thought to have extended to the continental shelf edge in most places and on eastern baffin island where ice probably extended to the fiord mouths rather than to the fiord heads around most of the ice margin the late wisconsinan maximum ice extent either exceeded the extent of earlier wisconsinan advances or it was similar to the early wisconsinan advance ice marginal recession prior to 14 14 ck a bp occurred mainly in deep water and along the southern terrestrial fringe however heinrich event 1 probably drew down the entire central ice surface at 14 5 14 c ka bp sufficiently to displace the labrador sector outflow centre 900 km eastward from the coast of hudson bay the onset of substantial ice marginal recession occurred about 14 14 c ka bp in the northwest southwest and south but not until about 10 11 14 c ka bp in the northeast and in the high arctic thus the period of maximum ice extent in north america generally encompasses the interval from b24 21 to 14 14 c ka bp or considerably longer than the duration of the lgm defined as occurring during a period of low global sea level as well as during a time of relative climate stability b18 14 c ka bp the interval of advance of much of the laurentide ice sheet to its maximum extent between b27 14 c ka bp and b24 14 c ka bp coincides with a suggested interval of rapid fall in global sea level to near lgmlevels r 2001 elsevier science ltd all rights reserved

reconnaissance of upper jurassic morrison formation ichnofossils rocky mountain region usa paleoenvironmental stratigraphic and paleoclimatic significance of terrestrial and freshwater ichnocoenoses seventy five types of ichnofossils documented during a four year reconnaissance study in the upper jurassic morrison formation demonstrate that highly diverse and abundant plants invertebrates and vertebrates occur throughout most of the morrison or equivalent strata invertebrate ichnofossils preserving the most environmentally and climatically sensitive in situ behavior of morrison organisms are in nearly all outcrops terrestrial ichnofossils record biotic processes in soil formation indicating soil moisture and water table levels freshwater ichnofossils preserve evidence of water depth salinity and seasonality of water bodies ichnofossils categorized as epiterraphilic terraphilic hygrophilic and hydrophilic new terms reflect the moisture regime where they were constructed the ichnofossils are vertically zoned with respect to physical chemical and biological factors in the environment that controlled their distribution and abundance and are expressed as surficial shallow intermediate and deep the sedimentologic stratigraphic and geographic distribution of morrison ichnofossils reflects the environmental and climatic variations across the basin through time marginal marine tidal to brackish water ichnofossils are mainly restricted to the windy hill member very large to small termite nests dominate the salt wash member similar size ranges of ant nests dominate the brushy basin member soil bee nests dominate in the salt wash decreasing in abundance through the brushy basin deeper and larger insect nests indicate more seasonal distribution of precipitation and rainfall shallower and smaller insect nests indicate either dry or wet substrate conditions depending on the nest architecture and paleopedogenic and sedimentologic character of the substrate trace fossil indicators of flowing or standing water conditions are dominant in the tidwell member and in fluvial sandstones of the salt wash and brushy basin members large communities of perennial freshwater bivalve traces are abundant in the tidwell and brushy basin members but to a lesser extent in the salt wash member shallow crayfish burrows indicating a water table level close to the surface 1 m are restricted to channel bank and proximal alluvial deposits in the salt wash recapture and brushy basin members sauropod theropod pterosaur and other vertebrate tracks occur throughout the morrison formation associated with alluvial lacustrine and transitional marine shoreline deposits ichnofossils and co occurring paleosols in the morrison reflect the local and regional paleohydrologic settings which record the annual soil moisture budget and were largely controlled by the climate in the basin contributions to near surface biologic systems by groundwater from distant sources were minor except where the water table perennially seasonally or ephemerally intersected the ground surface the jurassic morrison formation in the southern portion of the basin experienced a mosaic of seasonal climates that varied from a drier tidwell windy hill deposition to a wetter lower and middle salt wash deposition and slightly drier upper salt wash deposition tropical wet dry climate returning to a wetter tropical wet dry climate near the end of morrison deposition brushy basin deposition the northern part of the basin experienced similar trends across a mosaic of mediterranean climate types the range and mosaic pattern of wet dry morrison climates is analogous to the range of climates and their seasonal variability that dominates the african savanna today

out of the woods driftwood insights into holocene pan arctic sea ice dynamics the collation of 913 driftwood samples from across the western arctic with spatiotemporal distribution and available provenance data enabled the production of a high resolution proxy based reconstruction of holocene arctic ocean surface current and sea ice dynamics regionally bounded driftwood based sea ice reconstructions studies suggest spatiotemporally complex past arctic sea ice extent and movement however a large scale compilation of holocene arctic driftwood has not previously been developed sparse driftwood in the early holocene 8 2 cal ka b p deglacial period was followed by increased driftwood deposition in the warmer mid holocene 8 2 4 2 cal ka b p characterized by an enhanced transpolar drift tpd 7 cal ka b p leading to sea ice loss through the fram strait driftwood incursion peaks show spatial e w progression from the eurasian archipelagos to greenland and the canadian arctic archipelago suggesting a progressive shift in the orientation of the tpd on centennial millennial time scales and intermediate phases in the arctic oscillation late holocene cooling 4 2 cal ka b p is indicated by increased influx of probably north american picea via a strengthened beaufort gyre bg which enhanced sea ice recirculation starting in the western arctic and progressing eastward in recent millennia 2 cal ka b p a more variable driftwood record alternates between bg and tpd dominance on centennial time scales to further constrain a spatiotemporal reconstruction of variations in holocene ocean current and sea ice dynamics a more definitive determination of driftwood provenance is recommended to build upon the current framework such as through radiogenic isotope tracing and adna analysis

lower eocene alluvial paleosols pedogenic development stratigraphic relationships and paleosol landscape associations abstract two kinds of cumulative floodplain paleosols red and grey paleosols formed on overbank deposits of the willwood formation in the sand coulee area of the bighorn basin wyoming although both kinds experienced down profile iron movement due to seasonal saturation of a clay rich a horizon the red paleosols were better drained and their b horizons were rubified various redoximorphic features indicate that the grey paleosols were poorly drained the red paleosols show progressive increases in the degree of profile development away from an associated channel sandstone a paleosol landscape relationship termed pedofacies by bown and kraus 1987 although the grey paleosols show relatively systematic changes in hydromorphy consistent pedofacies changes were not recognized furthermore no lateral relationship between the red and grey paleosols was observed these features suggest that because of the retarding effects of poor drainage on soil weathering poorly drained soils are not amenable to pedofacies modelling and that the landscape associations of well drained and poorly drained soils may be difficult to document without unusually extensive exposures results of this study also show that the pedofacies model is limited by sediment accumulation rates and the kind of fine grained facies on which paleosols developed although readily observable in sand coulee pedofacies are difficult to recognize in the elk creek area where accumulation rates were approximately half as rapid as in sand coulee the attainment of steady state conditions is believed to have obscured pedofacies in the elk creek area finally pedofacies are only developed on true overbank deposits which in the willwood formation and probably many other ancient alluvial sequences make up only a fraction of the fine grained deposits only immature soils formed on the remainder of the fine grained facies because they were deposited very rapidly as a result of channel avulsion

early holocene delevelling and deglaciation of the cumberland sound region baffin island arctic canada radiocarbon cosmogenic surface exposure and relative sea level data are used to examine deglaciation and glacioisostatic adjustment of cumberland sound and cumberland peninsula and southeastern baffin island in the context of a new model for the glacial history of the eastern canadian arctic over the last decade a multidisciplinary effort on easternmost baffin island has documented far greater ice expansion during the last glacial maximum than previously believed including low gradient glaciation in marine embayments coexisting with ice free or thin cold based ice on adjacent upland crystalline terrain this study documents that the cumberland sound region underwent about twice as much glacioisostatic movement during the last glacial maximum as shown in previous reconstructions however the loading impact of the laurentide ice sheet and local glaciation on adjacent cumberland peninsula was limited the mapped zero isoline on emergence shows that postglacial eustatic rise exceeded glacial isostatic uplift for much of the eastern peninsula a finding that is consistent with that of prior studies the center of loading and the major source of glacial ice for the entire cumberland sound region were foxe basin and western baffin island strandlines dated 10 500 and 8500 1 4 c yr b p show that slow deglaciation of cumberland sound was punctuated by at least two periods of faster grounding line retreat coastal southeastern cumberland peninsula was deglaciated before 9400 1 4 c yr b p and other areas surrounding cumberland sound were deglaciated after ca 9000 1 4 c yr b p these land areas experienced relatively slow glacial retreat and restrained rebound cosmogenic surface exposure ages on glacially scoured bedrock support the 1 4 c based inferred timing for deglaciation of the sound although inheritance of nuclides from prior exposure is evident in samples indicating limited bedrock erosion in many areas for central cumberland sound a rapid rise of relative sea level of 4 5 m 100 1 4 c yr 4 6 m 100 yr and a half life for crustal response of 720 1 4 c yr 1400 yr are consistent with those values obtained in other studies of isostatic adjustment around the edges of the former northern hemisphere ice sheets where lithospheric influences were relatively dominant

cosmogenic 10be and 26al ages for the last glacial maximum eastern baffin island arctic canada a chronology for the last glacial maximum based on cosmogenic exposure dating in the pangnirtung fjord area eastern baffin island arctic canada is at odds with many decades of land based glacial stratigraphic research most previous chronologies focused primarily on relative weathering criteria and suggested that ice extent was restricted during the late wisconsinan ca 24 8 ka in contrast by directly dating glacial features we conclude that late wisconsinan ice was far more extensive than previously believed there are 36 gneissic boulders and 8 samples of ice molded gneissic bedrock that yield late wisconsinan 10 be and 26 al exposure ages for the last glaciation of pangnirtung fjord the prominent duval moraines which were previously interpreted to represent a significant early wisconsinan 100 60 ka ice advance on southern cumberland peninsula were actually deposited between 24 and 9 ka two boulders from a raised glaciomarine delta stratigraphically related to the duval moraines date to about 10 ka two recessional moraines and striated bedrock along pangnirtung fjord as well as erratics on the floor of the kolik river valley a tributary to pangnirtung fjord indicate that deglaciation began between 12 and 9 ka in situ produced 10 be and 26 al abundances indicate that ice filled pangnirtung fjord for about 15 k y either continuously or intermittently prior to 10 ka which is compatible with 14 c chronologies for adjacent cumberland sound thus our data support other recent studies that suggest the northern and southern margins of the laurentide ice sheet were generally in phase during the latest wisconsinan contrary to earlier interpretations

classification of paleosols despite increased interest in paleosols during the past decade no satisfactory classification is in current use presented here is a largely descriptive classification system that utilizes those pedogenic features that have the highest preservation potential in the rock record emphasized in the classification are morphological and mineralogical features that are easily recognizable in the field and through the petrographic microscope the classification is based on evaluation of the relative prominence in a paleosol of six pedogenic features or processes organic matter content horizonation redox conditions in situ mineral alteration illuviation of insoluble minerals compounds and accumulation of soluble minerals the most prominent of these six features processes provides the key to classifying a paleosol into one of nine orders four of the order names are borrowed from soil taxonomy histosol spodosol oxisol vertisol whereas the other five order names are presented here for the first time calcisol gypsisol gleysol argillisol protosol the orders may be preceded by one or more subordinate modifiers that describe other important features of the paleosol the classification is relatively easy to apply to the rock record and should enhance communication and aid in the standardization of terminology

alluvial response to the paleocene eocene thermal maximum climatic event polecat bench wyoming u s a abstract the stratigraphic interval spanning the paleocene eocene thermal maximum in the northern bighorn basin wyoming shows changes in the alluvial record that can be tied to a high resolution climate record the complexity and stratigraphic spacing of paleosols change through the study section comparison to the climate record reconstructed from paleosols indicates the changes correspond to paleocene eocene thermal maximum climatic fluctuations in particular the middle of the section contains thick welded paleosols and thin avulsion deposits that link to times of well drained floodplains and lower mean annual precipitation stratigraphic intervals below and above the main part of the paleocene eocene thermal maximum interval correspond to times of less well drained floodplains and higher mean annual precipitation these strata contain thinner paleosols and thick avulsion deposits differences in paleosol complexity and spacing suggest that sediment flux to the depositional site varied in response to precipitation fluctuations associated with the paleocene eocene thermal maximum welded paleosols and thin avulsion deposits indicate reduced floodplain accretion during deposition of the middle of the paleocene eocene thermal maximum intervals with widely spaced paleosols indicate more rapid accretion we hypothesize that drier episodes associated with warming caused reduced vegetation in source areas and promoted erosion and increased sediment yield because precipitation was reduced much of that sediment was stored in upstream reaches of the fluvial system rather than moving to the depositional basin welded paleosols formed because of diminished sediment supply to the basin with a return to wetter conditions during the recovery phase of the paleocene eocene thermal maximum upstream water flux increased stored sediment moved to the basin and vertically spaced thinner paleosols developed the results demonstrate how vertical sections of alluvial paleosols can provide information on how climate fluctuated through time and how the fluvial system responded to climate change

canadian geomorphology 2000 geomorphology has a distinguished history in canada as old as the country itself initially the science of geomorphology of canada drew on rich british and french scientific traditions but later it developed its own character strongly influenced by the richness and diversity of the canadian landscape the strong imprint of glaciation and the importance of periglacial processes permafrost and sea ice canada is the second largest country in the world its coastline is longer and more varied than that of any other country nearly one third of canada is underlain by permafrost some up to 700 m thick the country s physiography ranges from nearly flat coastal and interior plains to the glacierised mountains of baffin and ellesmere islands british columbia and the yukon its climate and vegetation are equally diverse ranging from the cold semiarid tundra of the high arctic to the temperate rainforest of the pacific coast given this diversity it is not surprising that canada is active in many areas of geomorphic research an incredible spectrum of landforms and geomorphic processes has fostered world class research in canada both by canadians and by scientists from other countries much of this research is field based and empirical rooted in field observation in recent decades however there have been important advances in inductive laboratory and

possible burrows of mylagaulids rodentia aplodontoidea mylagaulidae from the late miocene barstovian pawnee creek formation of northeastern colorado abstract the massive siltstone beds of the late miocene barstovian pawnee creek formation in logan county northeastern colorado contain abundant terrestrial vertebrate burrows among these are distinctive claw marked burrows attributable to the extinct mylagaulid rodent pterogaulus mylagaulus laevis korth 2000 these burrows differ in several respects from the spiraling daemonelix burrows of fossorial beavers the pawnee creek burrows are slightly ovate in cross section tubular and sinuous rather than helical they consist of primary tunnels of up to at least 7 m long and range from 11 to 18 cm in diameter they occasionally branch into secondary tunnels burrow walls and terminations show prominent parallel ridges in sets of two to three up to 9 3 mm deep and 3 7 mm wide the burrows are too large to have been made by anything but a vertebrate and their considerable length and complexity implies a mammalian excavator the meandering branching morphology resembles the burrow systems of extant fossorial rodents such as pocket gophers geomys and mole rats spalax myospalax skeletal remains of p laevis are abundant at sites where the burrows occur with at least eight individuals represented by humeri in a collected sample although mylagaulid remains are not unequivocally associated with fossil burrows the curved laterally compressed claws and phalangeal arrangement of mylagaulids produce marks very similar in size and morphology to the ridges on the burrows position and pattern of the ridges indicate downward and backward motions of the mani possibly supplemented by motions of the pedes to kick loosened soil backward a new ichnogenus alezichnos and new ichnospecies chelecharatos are erected to describe these burrows

paleosols in devonian red beds from northwest china and their paleoclimatic characteristics abstract paleosols have been discovered in the late devonian famennian shaliushui formation near pingchuan city gansu province china and are recognized by evidence of root traces soil horizons and soil structures root traces are remnants of substantial woody plants reaching deeply within profiles as clayey infills and as drab haloed root traces soil horizons include thick layers of large calcareous nodules bk horizon and subsurface accumulations of clay bt horizon and slickensided claystone vertic bw horizon soil structures include blocky peds and calcareous nodules the nodules and drab haloed root traces formed syndepostionally during the late devonian because they were also observed in clasts of paleosol and nodules in fluvial conglomerates interbedded with the paleosols analyses for rb sr and ba sr ratios and magnetic susceptibility measurements confirm that the more strongly developed paleosols with larger calcareous nodules and higher clay content are also more chemically differentiated and have higher magnetic susceptibility under semi arid climates this suite of paleosols is evidence of semi arid to sub humid highly seasonal climate under dry woodlands and shrublands paleosols of the shaliushui formation are a potentially valuable archive of late devonian palaeoclimates of northwest china

cenozoic expansion of grasslands and climatic cooling abstract mountains ocean currents forests and swamps have played an important role in regulating global climate for hundreds of millions of years but the truly novel event of the cenozoic was the evolution and expansion of grasslands with their uniquely coevolved grasses and grazers neogene expansion of the climatic and geographic range of grasslands at the expense of woodlands is now revealed by recent studies of paleosols fossils and their stable isotopic compositions grasslands and their soils can be considered sinks for atmospheric co2 ch4 and water vapor and their cenozoic evolution a contribution to long term global climatic cooling grassland soils are richer in organic matter than are woodland and desert soils of comparable climates and when eroded their crumb clods form sediment unusually rich in organic matter grasslands also promote export of bicarbonate and nutrient cations to lakes and to the oceans where they stimulate productivity and c burial this increased productivity and

paleohydrologic and stratigraphic significance of crayfish burrows in continental deposits examples from several paleocene laramide basins in the rocky mountains abstract paleocene crayfish burrows are present locally in great abundance in the greater green river hanna wind river and piceance basins of wyoming and colorado in the washakie sub basin of the greater green river basin burrows are found in 1 lenticular cross bedded sandstones of fluvial channel origin 2 massive sandstones and mudrocks of floodplain origin that surround and interfinger with the cross bedded sandstones and 3 thin sandy ironstone beds of overbank and crevasse splay origin the burrows which represent crayfish activity in proximal to distal floodplain settings are assigned to camborygma symplokonomos c eumekenomos and c litonomos on the basis of their architectural morphologies c araioklados is not present crayfish burrows are part of pedogenically modified channel and overbank deposits in all the basins studied burrows are abundant only in non coal bearing rocks the presence of elongate burrows indicates that the landscape was imperfectly drained on a seasonal basis and the burrow depths suggest the paleo water table was 1 4 m below the paleosurface swampy conditions prevailed in areas where carbonaceous shales and coals formed and thus crayfish did not construct deep burrows the crayfish burrows and associated lithologies suggest a warm humid wet seasonal climate in the eastern washakie basin the vertical and lateral distribution of burrows and their abundance reflect changes in the paleohydrologic regime over space and time burrow depth and overall abundance decreases towards local basin lowlands where they are rare the paleohydrologic regime coupled with a progressively less seasonal climate through time allowed the formation of the cherokee coal zone in the late paleocene in an otherwise lithologically homogeneous non variegated deposits stratigraphically significant surfaces may be indicated only by the tops of burrowed intervals and by other types of paleosols the tops of burrowed intervals represent paleosurfaces of varying environmental stability on which there are different frequency and magnitude of sedimentation events immature cumulative paleosols characterized by less intensely burrowed beds or bedsets record higher sedimentation rates more intensely burrowed beds or bedsets reflect the activity of many generations of crayfish hence the tops of these layers record longer durations of exposure and pedogenic modification with infrequent or no sedimentation paleosols represented by burrowed intervals in conjunction with sandstone and mudrock stacking patterns can be used to identify significant stratigraphic surfaces such as parasequences and sequence boundaries in fully continental environments

complex palaeosol ichnofabrics from late jurassic early cretaceous volcaniclastic successions of central patagonia argentina abstract late jurassic early cretaceous volcaniclastic continental deposits from central patagonia argentina were analyzed for an integral characterization of palaeosol ichnofabrics these units contain complex continental ichnofabrics that were also recorded in other late jurassic late miocene extended volcaniclastic successions from patagonia according to a recently proposed method ichnofabric pedofabric and original bedding of selected intervals were measured separately in order to determinate the degree in which the deposits are affected by soil features besides the ichnofabrics four recurrent ichnofabrics were recognized in studied palaeosols the loloichnus large taenidium beaconites diffuse boxwork and dagnichnus ichnofabrics the loloichnus ichnofabric is characterized by sub vertical loloichnus baqueroensis and subordinate similarly arrenged large taenidium barretti and beaconites coronus l baqueroensis is a crayfish dwelling structure while large t barretti and b coronus are assigned to locomotion of the same organisms root traces are additional components of this ichnofabric the large taenidium beaconites ichnofabric is formed by large irregular and curved t barretti and b coronus and by l baqueroensis in low proportion this ichnofabric is also assigned to crayfish activity the diffuse boxwork ichnofabric is characterized by a pervasive and intricate three dimensional boxwork of burrows occasionally joined to subspherical chambers possible castrichnus the diffuse boxwork is interpreted as an earthworm burrow system and the associated chambers are probably for aestivation rare and scattered discrete trace fossils in this ichnofabric include l baqueroensis t barretti and b coronus the dagnichnus ichnofabric is formed by dagnichnus titoi root traces and subordinately loloichnus baqueroensis cellicalichnus meniscatus and tangled groups of meniscate burrows d titoi and c meniscatus has been interpreted as crayfish breeding structures and the tangled groups of meniscate burrows are probably related to juvenile crayfish activity the studied ichnofabrics were formed in weakly to moderately developed palaeosols in lowland areas with frequent reworking of pyroclastic material by unconfined flows the recognized ichnofabrics show that in patagonia for the late jurassic early cretaceous times crayfishes and earthworms were the dominant soil organisms and along with plants rapidly colonized deposits exposed subaerially after sediment deposition and with high soil moisture content or high water table crayfishes probably crawled in moist sediments forming the large taenidium beaconites ichnofabric with a better drained soil profile or lower water tables the loloichnus ichnofabric representing the dwelling structures of adult crayfishes overprinted the previous ichnofabric the diffuse boxwork ichnofabric usually located in the uppermost portion of palaeosols correspond to extensive fossil earthworm burrow systems the dagnichnus ichnofabric occurs in very weakly developed palaeosols and probably reflects the optimal palaeoenvironmental conditions for breeding crayfish

biolaminated sedimentation in a high arctic freshwater lake a laminated sequence of lacustrine sediment from an arctic coastal lake was examined for potential chronological and successional information the laminae are microbially induced sedimentary structures the unlithified precursor of stromatolites and are previously unreported in the arctic the inferred annual sequence was interpreted to contain a basal clastic unit overlain with successive cyanobacterial and extracellular polymeric substance units the complex succession of laminae and inconclusive dating provide a challenge for identifying the chronological nature of the sedimentary structures markov chain and time series analyses suggest that a plausible quasi annual sequence can be identified to provide a context for palaeo environmental reconstruction recognition of sedimentary structure in recent biolaminated sediments offers a first step towards the palaeo environmental evaluation of the geomicrobiological sequence

paleosol and ichnofossil evidence for significant neotropical habitat variation during the late middle miocene serravallian we use paleopedology and ichnology to elucidate the habitat of the late middle miocene fossil site of quebrada honda southern bolivia the paleosols represent three pedotypes type 1 and type 2 paleosols are interpreted as inceptisols eutrudepts and entisols udifluvents respectively which formed on proximal and distal floodplains in a seasonal sub humid to humid wooded grassland like vegetative community type 3 paleosols are interpreted as inceptisols calciustepts that formed in more densely vegetated wooded grassland like vegetative communities on distal floodplains in a strongly seasonal sub humid to semi arid environment the ichnofossil assemblage of quebrada honda includes celliforma coprinisphaera taenidium fictovichnus planolites skolithos katarrhedrites and root traces and represents heterogeneous communities dominated by soil arthropods and plants the physical and geochemical properties of the paleosols including low maturity poor development of horizons and the overall moderate estimates of mean annual precipitation indicate changes in soil moisture due to seasonal precipitation and flooding and low but varying degrees of temporal stability the diverse ichnofossil assemblage of quebrada honda reflects environments with greater primary productivity and temporal stability than those of nearby cerdas bolivia which are several million years older quebrada honda s inferred paleoenvironments differ markedly from those of la venta colombia indicating that dissimilar habitats may partly or principally account for the vastly different faunas of these two well sampled and contemporaneous fossil localities

stability of active mantle upwelling revealed by net characteristics of plate tectonics global scale mantle flow patterns can be deduced from the net behaviour convergence and divergence of surface plate motions persistent quadrupole divergence in central africa and the central pacific suggest sustained stationary upwelling beneath these locations in the mantle earth s long history of intense geological activity mountain building and plate tectonic motion included is correlated with viscous flow of the underlying mantle clinton conrad and co authors show here that despite their apparent complexity the net characteristics of plate tectonics reflect simple and steady large scale patterns of viscous flow within the underlying mantle they tracked the geographic locations of net convergence and divergence from tectonic reconstructions covering the past 250 million years and found that the positions of divergence have not moved significantly and are found above two large upwellings beneath africa and the pacific ocean the authors conclude that these lowermost mantle regions may have remained relatively stationary over geological time and thereby organized global mantle flow viscous convection within the mantle is linked to tectonic plate motions1 2 3 and deforms earth s surface across wide areas4 5 6 such close links between surface geology and deep mantle dynamics presumably operated throughout earth s history but are difficult to investigate for past times because the history of mantle flow is poorly known7 here we show that the time dependence of global scale mantle flow can be deduced from the net behaviour of surface plate motions in particular we tracked the geographic locations of net convergence and divergence for harmonic degrees 1 and 2 by computing the dipole and quadrupole moments of plate motions from tectonic reconstructions8 9 extended back to the early mesozoic era for present day plate motions we find dipole convergence in eastern asia and quadrupole divergence in both central africa and the central pacific these orientations are nearly identical to the dipole and quadrupole orientations of underlying mantle flow which indicates that these net characteristics of plate motions reveal deeper flow patterns the positions of quadrupole divergence have not moved significantly during the past 250 million years which suggests long term stability of mantle upwelling beneath africa and the pacific ocean these upwelling locations are positioned above two compositionally and seismologically distinct10 regions of the lowermost mantle which may organize global mantle flow11 as they remain stationary over geologic time12

late wisconsinan glaciation of the central sector of the canadian high arctic abstract geomorphic and chronological evidence from cornwall island in the canadian high arctic archipelago provides direct evidence for the age and dynamics of the center and northern flank of the innuitian ice sheet that covered the islands during the late wisconsonian glacial maximum dispersal of erratics and glacial landforms indicate that ice flowed north across the island and converged with ice flowing northwest from norwegian bay cornwall island was initially deglaciated at 9000 14c yr b p in near synchrony with widely separated sites in adjacent parts of the archipelago this regional chronology suggests rapid breakup of a marine based innuitian ice sheet that was destabilized by rapid eustatic sea level rise and ice thinning during the early holocene this evidence provides strong support for a recently proposed ice divide spanning the central part of the canadian high arctic and indicates that most if not all of the region was glaciated during the late wisconsinan

late oligocene bunch grassland and early miocene sod grassland paleosols from central oregon usa abstract fossil soils burrows and mammals of the upper john day formation in central oregon are evidence of bunch grasses and open semiarid vegetation as old as late oligocene earliest arikareean 30 ma root traces in these paleosols include both stout tapering tubes like roots of trees as well as sinuous filamentous tubes similar to roots of grasses paleosol structure is fine subangular blocky with patchy distribution of grass like roots as in wooded grassland and sagebrush steppe with bunch grasses cursoriality in horses mesohippus miohippus and hypsodonty in rhinos diceratherium is also evidence for open grassy vegetation trace fossils of pallichnus dung beetle boli and edaphichnium earthworm chimneys are characteristic of wooded grassland paleosols whereas taenidium cicada burrows dominates desert shrubland paleosols as has also been found in quaternary paleosols and soils of eastern washington in both oligocene and quaternary paleosol sequences arid shrubland and semiarid grassland paleosols alternate on milankovitch frequencies 23 41 100 ka the oldest known paleosols in oregon with crumb structure and abundant fine fossil root traces characteristic of sod grasslands are dated by mammalian biostratigraphy as hemingfordian early miocene ca 19 ma wooded grassland habitats are indicated by scattered chalcedony calcite rhizoconcretions from large woody plants and by fossil chalicotheres moropus camels gentilicamelus paratylopus and horses parahippus silty texture and silcrete horizons are evidence of semiarid to arid paleoclimate and are in striking contrast to highly calcareous and clayey underlying paleosols of the john day formation these silcrete paleosols may represent the miocene onset of summer dry mediterranean seasonality as opposed to a summer wet monsoonal pattern of seasonality found in this region during the oligocene oregon s early rangelands can be compared with those in the north american great plains granular structured calcareous paleosols of the brule formation of south dakota are evidence of dry bunch grasslands as old as 33 ma early orellan early oligocene and crumb structured paleosols of the anderson ranch formation of nebraska are evidence of sod grasslands as old as 19 ma late arikareean early miocene although grasses were a conspicuous part of dry rangelands well back into the oligocene early and middle miocene sod grasslands in north america were restricted to regions estimated to have had less than 400 mm mean annual precipitation

holocene sediments from a coastal lake on northern devon island nunavut canada sediment cores from lake dv09 northern devon island nunavut canada 75 34 34 n 89 18 55 w were studied to reconstruct the lake ontogeny through analysis and interpretation of the sediment stratigraphy the lake was uplifted from marine inundation 7600 cal bp after a millennium of rapid sediment accumulation which coincided with the holocene thermal maximum in the region accumulation rates decreased over the past 6000 years as the arctic became colder this resulted in the deposition of very fine laminae that were interpreted as varves the uppermost laminated sediments provided a 1600 year history of annual sediment transport and deposition into the lake during periods of warmer temperatures such as between 6000 and 7500 cal bp and during the medieval climate anomaly 950 1300 ce ce christian era hydroclimatic and permafrost slope processes increased sedimentation rates into the basin

a paleopedologic and ichnologic perspective of the terrestrial pennsylvanian landscape in the distal appalachian basin u s a abstract the conemaugh group of southeastern ohio contains numerous ichnofossil bearing paleosols in both the lower glenshaw and upper casselman formations which were deposited during the kasimovian and gzhelian 305 301 ma along the distal edge of the appalachian basin this study examined the small scale twenty four stratigraphic sections were measured from ten sites in athens county ohio from which thirty paleosols were identified and described detailed field descriptions allowed differentiation of four distinct pedotypes one in the glenshaw formation and three in the casselman formation the glenshaw pedotype gpt is a vertisol that formed on a proximal to distal floodplain the three casselman pedotypes represent entisols inceptisols cpti alfisols cptii and vertisols cptiii all four types contain evidence of alteration by post pedogenic processes such as drowning by migrating river channels or rising sea level or a gradual transition from one alluvial subenvironment to another as a result of channel migration eight morphologically distinct ichnofossils were observed in the conemaugh group paleosols including three types of rhizoliths lined and unlined vertical to subhorizontal shafts chambers sinuous burrows with and without bioglyphs and general burrow mottling these ichnofossils occur in distinct assemblages that form unique ichnocoenoses within each of the four pedotypes they were produced by various plants arthropod detritivores carnivores and herbivores as well as amphibians and early reptiles as temporary to permanent members of complex soil ecosystems pedogenic properties combined with ichnofossil diversity abundance and distribution increase the understanding of the complexity of late pennsylvanian soil ecosystems and provide details on the small scale variations in paleosols due to short term autogenic changes in alluvial environments although broad regional studies across 10 2 10 3 of kilometers are important small scale variations over less than 1 km are needed to understand the effects of localized changes in hydrology topography organisms and sedimentary processes on soil formation and soil biodiversity consideration of these types of localized studies is also vital when attempting to interpret regional to global scale aspects of environment such as climate from paleosols

significance of different modes of rhizolith preservation to interpreting paleoenvironmental and paleohydrologic settings examples from paleogene paleosols bighorn basin wyoming u s a abstract different modes of preservation of root traces rhizoliths provide information on soil moisture regimes in alluvial paleosols in the paleogene fort union and willwood formations of the bighorn basin wyoming u s a this paper links different styles of rhizolith preservation to paleosols whose other pedogenic attributes provide information on ancient soil drainage consequently the paleodrainage significance of different rhizolith preservation patterns is established more confidently rhizoliths consisting of elongate gray mottles rhizohaloes with red rims are common in relatively well drained red paleosols the gray zones are depleted of iron fe whereas the color of the rims indicates hematite accumulation these features are typical of surface water gley processes that caused fe and manganese mn to move from the root channel outward to the soil matrix calcareous rhizocretions either calcareous tubular concretions or micro accumulations of carbonate within gray rhizotubules are also common in moderately well drained red paleosols more poorly drained purple paleosols also have rhizoliths consisting of fe depletion zones however the rhizohaloes are surrounded by yellow brown goethite rims rather than red hematitic rims in many paleosols the red and yellow brown accumulation rims were partly removed by continued depletion producing abundant irregular shaped mottles the nature of the rhizohalo and the color of the fe oxide rim provide information about the intensity of gleying that a paleosol underwent the poorly drained paleosols also show rhizoliths preserved as goethite accumulations contained within gray depletion zones indicating movement of reduced fe from the matrix towards the root channel probably as a result of groundwater gley processes the goethite accumulations are intermingled locally with lignite representing preservation of the root organic material some rhizoliths are preserved as tube shaped concentrations of small 0 1 0 2 mm diameter black spheres whose color indicates a mix of mn and fe oxides these are most common in paleosols with low chroma gray matrix colors indicating very poor drainage the very poorly drained paleosols also show rhizoliths preserved in jarosite which is an oxidation product of pyrite careful observational and geochemical analysis of rhizoliths which are common in continental deposits can help produce a clearer and more thorough interpretation of ancient drainage conditions information about degree of ancient soil wetness or moisture is important for understanding past climatic conditions and for reconstructing terrestrial paleolandscapes

ant nest ichnofossils in honeycomb calcretes neogene ogallala formation high plains region of western kansas u s a abstract two new ant nest trace fossils are described from calcic sandy paleosols of the neogene ogallala formation in western kansas the ichnofossils are preserved within and below calcrete beds weathering in positive relief as carbonate filled casts or as cavities in negative relief daimoniobarax ichnogenus nov is established for burrow systems composed of vertically tiered horizontally oriented pancake shaped chambers connected by predominantly vertical and cylindrical shafts 0 8 cm in diameter ichnospecies of daimoniobarax are differentiated based on differences in the plan view outline of chambers shaft orientation and junctions between chambers and shafts daimoniobarax nephroides ichnospecies nov is composed of an 24 76 cm long vertical sequence of distinctly lobed chambers 2 20 cm wide and 1 cm high arranged along sinuous to helical shafts chamber shape in plan view ranges from small teardrops to larger kidney and u shaped forms shafts intersect at chamber edges such that chambers appear to bud from the central shafts daimoniobarax nephroides is most similar to the nests of extant seed harvester ants of the new world genus pogonomyrmex such ants are specialized granivores and prefer sandy soils in arid to semi arid grassland and desert regions daimoniobarax tschinkeli ichnospecies nov is 30 80 cm in vertical extent chambers 2 30 cm wide and 1 cm high are circular to elongate or pseudopodial in plan view vertical shafts are straight to slightly sinuous and intersect most often toward the center of the chambers the generalized architecture of d tschinkeli is similar to that of the nests or nest portions of several extant ant genera though it does not closely resemble any known modern nest ant ichnofossils provide valuable information on hidden biodiversity paleohydrologic regimes paleopedogenic processes and paleoclimate during the time of nest occupation depth related changes in chamber size and vertical spacing may also help interpret paleosurfaces and paleodepths and serve as geopetal features

faunal burrows as indicators of paleo vegetation in eastern washington usa abstract the palouse loess deposits in the pacific northwestern united states contain buried paleosols with distinctive biological fabrics the washtucna soil formed 40 000 15 000 yr ago during the last full glacial contains up to 90 by volume distinctive cylindrical pedotubules that are 1 2 cm in diameter formed by burrowing fauna the overlying post glacial loess and modern surface soils that support perennial grasslands lack these cylindrical burrows we investigated the paleoecological significance of the burrows observations of several types of burrowing fauna under native vegetation indicated that nymphs of cicadas homoptera cicadidae are responsible for cylindrical back filled burrows that match those in the washtucna soil we measured the abundance of active cicada burrows in soils in four native vegetation zones soil sites establishing that cicada burrows comprise 19 of the rooting zone volume in sagebrush steppe but just 1 3 of the rooting zone volume in bunchgrass steppe meadow steppe and coniferous forest this suggests strongly that abundant cicada burrows in paleosols are a proxy for the geographic extent of plant communities that contained sagebrush to assay the activity of cicada nymphs through time we measured burrowed volume by depth from the soil surface down through the washtucna soil i e from the present to ca 40 000 yr bp at five stratigraphic research sites paleosol sites cicada burrowed volume is generally less than 5 in the rooting zone of the surface soils and throughout holocene loess but is up to 94 in the rooting zone of the washtucna soil at paleosol sites that currently support bunchgrass steppe outside the present day sagebrush steppe zone cicada host preferences in vegetation zones today suggest that sagebrush was the dominant shrub as the washtucna soil formed from this reconstruction combined with information from studies of pollen and plant opal we infer that periglacial steppe plant communities dominated by sagebrush spread from 40 000 to 15 000 yr bp into areas of the columbia plateau that support bunchgrass steppe meadow steppe and even some coniferous forest today trace fossils of soil fauna in paleosols are indicators of fluctuations in biological activity in response to climatic changes of the quaternary period in palouse loess deposits

forms response times and variability of relative sea level curves glaciated north america abstract relative sea level curves from glaciated north america reveal coherent spatial patterns of response times in the laurentide ice sheet area curve half lives range from 1 2 1 4 ka at the uplift centre to 1 7 2 ka in a ridge of high values inboard of the glacial limit half lives decline from this ridge to less than 1 ka along the margin in the innuitian ice sheet area half lives are about 2 ka at the uplift centre and decline to less than 1 ka at the margin the central laurentide response times are about half those of central fennoscandia this accords with the theoretical expectation that central response times are inversely proportional to ice sheet radius for ice loads large enough that rebound at the centre is insensitive to lithospheric thickness the innuitian central response time indicates that rebound at the centre of this ice sheet which is much smaller than the fennoscandian ice sheet remains sensitive to lithospheric thickness radial gradients in response times reflect the increasing influence of the lithosphere at sites increasingly closer to the margin along this gradient rebound progresses as though at the centres of smaller and smaller ice sheets that is the effective spatial scale of the ice load decreases toward the margin near the glacial limit postglacial isostatic adjustment is complicated by forebulge migration and collapse this is seen most strongly in the relative sea level record of atlantic canada which has subsided during the holocene more than 20 m more than the adjacent american seaboard the relative sea level history of some areas notably the st lawrence estuary is complicated by tectonic processes

paleoenvironmental analysis of the neotropical fossil mammal site of cerdas bolivia middle miocene based on ichnofossils and paleopedology abstract the early middle miocene langhian age site of cerdas in the southern bolivian altiplano has produced a diverse fauna of extinct mammals 15 species in seven orders and 11 families in this study we use paleosols and ichnofossils to reconstruct its paleoenvironment and the conditions in which its fossils were preserved the described paleosols represent three pedotypes and three distinct landscape surfaces in an alluvial system type 1 paleosols are interpreted as haplusteps inceptisols that formed on a proximal floodplain in a subhumid to humid patchy shrubland with seasonal variation in precipitation and associated changes in soil moisture conditions landscape 1 type 2 paleosols are interpreted as dystrudepts that formed on a well vegetated distal floodplain in a seasonal humid climate with ground covering shrubland vegetation landscape 2 type 3 paleosols are interpreted as calciustolls mollisols that formed in a shifting alluvial environment in a seasonal sub humid to semi arid open environment landscape 3 ichnofossil assemblages of cerdas include skolithos planolites macanopsis parowanichnus rhizohaloes and rhizotubules these were produced by detritivorous herbivorous and faunivorous soil arthropods as well as plant roots and represent soil communities not normally preserved as body fossils that were living within a heterogeneous alluvial environment the physical and geochemical properties of the paleosols and associated ichnofossil assemblages indicate that the paleolandscapes were composed of shrublands and open environments that experienced changes in moisture regimes due to seasonal precipitation and flooding events and had varying degrees of temporal stability our analysis is the first detailed study of pre pleistocene cenozoic paleosols and trace fossils from the southern tropics mid latitudes of south america and one of the few focused on important fossil mammal bearing sediments

tetrapod burrows from the middle upper triassic chanares formation la rioja argentina and its palaeoecological implications abstract we describe tetrapod burrows from the uppermost middle lower upper triassic latest ladinian early carnian chanares formation ischigualasto villa union basin la rioja province northwestern argentina the burrows were found in different localities of the unit but restricted to the lowermost 17 m of the formation they occur at the same interval as a tetrapod assemblage composed of erpetosuchid and basal paracrocodylomorph pseudosuchians basal traversodontid and chiniquodontid eucynodontians and stenaulorhynchine rhynchosaurids this assemblage differs from the typical chanares fauna that occurs in stratigraphically higher levels the burrows were found within the deposits of moderately developed palaeosols formed in volcanically influenced braided fluvial facies under semi arid climate conditions the burrow systems are cylindrical to sub cylindrical in cross section up to 25 cm in diameter and characterized by long multiple branching tunnels several metres long that meander horizontally or are slightly inclined

miocene vertebrate and invertebrate burrows defining compound paleosols in the pawnee creek formation colorado u s a abstract ichnofossils from two compound paleosols in the middle miocene pawnee creek formation pcf of northeastern colorado u s a indicate a diverse soil ecosystem that included plants invertebrates and vertebrates the 2 4 m thick paleosols are characterized by blocky textures shallow depth calcareous horizons overlying silty bioturbated horizons calcareous nodules dense mats of fine ichnofossils attributed to ground beetles ants reptiles and mammals represent a complex variety of behaviors including temporary to permanent dwelling nesting and food storing rhizoliths and burrows used to interpret media consistency organic content soil moisture and water table level are tiered from shallow intermediate to deep levels within paleosols with respect to physical and biological factors separate bioturbated intervals permits the recognition of two different paleosols that otherwise might not have been recognized such well developed paleosols with high densities of terrestrial burrows have substantial sequence stratigraphic significance since they define surfaces of low sedimentation base level and accommodation the pcf ichnofossil assemblages represent at least three distinct ichnocoenoses the kladosystemites ichnocoenosis with kladosystemites polychoredrites parowanichnus and 1 10 mm diameter rhizoliths is present in the upper profile of well drained consolidated and nutrient rich paleosols with dense concentrations of small to large plants at the surface the beaconites ichnocoenosis with beaconites katarrhedrites and 5 10 mm rhizoliths is present in the lower profile of moderately organic paleosols above the influence of the water table but subject to seasonally variable saturated and unsaturated conditions due to precipitation the daimonelix ichnocoenosis with daimonelix beaconites small to large katarrhedrites and 5 10 mm diameter rhizoliths is present in the lower profile of very organic rich paleosols generally above the influence of the water table but subject to seasonally variable saturated and unsaturated conditions integration of data from body fossils ichnofossils paleosols and sedimentary environments provides new insight into neogene ecosystems paleosol properties combined with the ichnofossil distribution abundance and diversity indicates that miocene pcf paleosols formed under a seasonal climate subject to wide variation in temperature and precipitation the diverse assemblage of burrow morphologies records adaptation of the local fauna to these environmental conditions the response of soil ecosystems to short and long term changes in climate is therefore vital to any study of the effects of climate change in the geologic record

striking similarities in temporal changes to spring sea ice occurrence across the central canadian arctic archipelago over the last 7000 years abstract a 7000 year spring sea ice record for victoria strait arc 4 and dease strait arc 5 in the canadian arctic archipelago caa has been determined by quantification of the sea ice diatom derived biomarker ip 25 in two marine sediment piston cores obtained in 2005 the chronologies of the arc 4 and arc 5 cores were determined using a combination of 14 c ams dates obtained from macrobenthic fossils and magnetic susceptibility measurements the ages of the tops of the piston cores were estimated by matching chemical and physical parameters with those obtained from corresponding box cores these analyses revealed that while the top of the arc 4 piston core was estimated to be essentially modern ca 60 cal yr bp a few hundred years of sediment appeared to be absent from the arc 5 piston core downcore changes to ip 25 fluxes for both cores were interpreted in terms of variations in spring sea ice occurrence and correlations between the individual ip 25 flux profiles for victoria strait dease strait and barrow strait reported previously were shown to be statistically significant at both 50 and 100 year resolutions the ip 25 data indicate lower spring sea ice occurrences during the early part of the record ca 7 0 3 0 cal kyr bp and for parts of the late holocene ca 1 5 0 8 cal kyr bp especially for the two lower latitude study locations in contrast higher spring sea ice occurrences existed during ca 3 0 1 5 cal kyr bp and after ca 800 cal yr bp the observation of consecutively lower and higher spring sea ice occurrence during two periods of the late holocene coincides broadly with the medieval warm period and little ice age epochs respectively the ip 25 data are complemented by particle size and mineralogical data although these may alternatively reflect changes in sea level at the study sites the ip 25 data are also compared to previous proxy based determinations of palaeo sea ice and palaeoclimate for the caa including those based on bowhead whale remains and dinocyst assemblages the spatial consistency in the proxy data which most notably indicates an increase in spring sea ice occurrence around 3 cal kyr bp provides a potentially useful benchmark for the termination of the holocene thermal maximum for the central caa