field test of autogenic control on alluvial stratigraphy ferris formation upper cretaceous paleogene wyoming internally generated autogenic sedimentary processes can obscure signals of tectonic movements climate conditions or sea level fl uctuations in alluvial basins the stratigraphic effects of autogenic dynamics have been considered negligible on time scales of 10 4 10 6 yr however recent physical and numerical models have shown that over basin fi lling time scales self organization in sedimentary systems can produce stratigraphic patterns similar to those resulting from changing basin boundary conditions here we present the fi rst fi eld based test for autogenic control on stratigraphy in an ancient alluvial basin the ferris formation upper cretaceous paleogene hanna basin wyoming is composed of clusters of closely spaced channel deposits separated by intervals dominated by overbank material a pattern that has been proposed as an example of a potentially autogenic stratigraphy in order to evaluate controls on ferris formation stratigraphy spatial patterns of key channel properties were analyzed these variables including sand body dimensions paleofl ow depth maximum clast size paleocurrent direction and sediment provenance were chosen because they can change in response to climate tectonic or sea level forcing and are commonly measurable in ancient alluvial successions no clear statistical trends were detected in the measured variables which suggests that external forces did not likely control stratigraphic organization in the unit this study demonstrates that autogenic dynamics in natural fi eld scale systems can produce organized stratigraphic patterns over much larger spatial and temporal scales than is typically presumed this fi nding emphasizes the need for further understanding of autogenic stratigraphy and greater care interpreting climate tectonic and eustatic changes from alluvial basins

terrestrial crustacean breeding trace fossils from the cretaceous of patagonia argentina palaeobiological and evolutionary significance abstract the breeding trace fossils described herein along with the high density of loloichnus baqueroensis in the cretaceous formations of patagonia suggest that crayfishes were soil engineers along the cretaceous in southern south america and that they had acquired many of the k breeding behaviours recorded by insects in latest and post cretaceous soils such as pelletal constructions and excavation of breeding cells the k t event was probably responsible for changes in environmental conditions in such a way that crayfishes finally became restricted to two small distributional areas in southern south america and k breeding insects replaced them as keystone organisms in cainozoic and modern soils dagnichnus titoi igen and isp nov and cellicalichnus meniscatus isp nov are created to include the new trace fossils attributable to crayfishes from the cretaceous of patagonia argentina the attribution to crayfishes is based on their association and morphological affinities with the crayfish fossil burrows l baqueroensis from the same geologic units d titoi is represented by hemispherical chambers surrounded by thick and short meniscate burrows which can be arranged in two or three tight whorls in the more regular specimens meniscate burrows are curved downwards and have no neck walls are unlined c meniscatus are necked horizontal and straight cells showing meniscate fillings attached to sub vertical shafts which are relatively much wider than the neck of cells both shafts and cells show a thin and smooth lining the presence of cells or burrows smaller than the putative parental burrows and comparisons with breeding traces of marine decapoda support the interpretation of breeding traces calichnia of terrestrial crustaceans c meniscatus is interpreted as cells excavated from parental burrows whereas d titoi are probably breeding structures completely produced in a different palaeoenvironment where the female release juveniles

magnetic properties and potential field modeling of the peculiar knob metamorphosed iron formation south australia an analog for the source of the intense martian magnetic anomalies an extremely intense 120 a m 1 remanence directed steeply upward this ancient remanence reinforces the local earth s field inclination 63 a simple geological model constrained by drilling and physical property measurements explains both the observed magnetic and gravity anomalies consistent with the poisson theorem koenigsberger ratios qs of 10 and greater as found here are rare in nature we postulate that acquisition of a thermoremanent magnetization trm by the ore during

crayfish burrows from the latest cretaceous lower cantwell formation denali national park alaska their morphology and paleoclimatic significance abstract latest cretaceous strata of the lower cantwell formation denali national park central alaska range contain an abundance of megafloral remains and invertebrate and vertebrate trace fossils though dominated by herbivorous dinosaur footprints the abundance and diversity of fossil bird tracks are unique we present newly discovered crayfish burrows from several areas along a 50 km transect with denali national park most crayfish burrows from the lower cantwell formation are preserved only in cross section and range from approximately 5 10 cm in diameter where preserved in full relief and terminations present burrow depth is generally the cantwell formation fills the cantwell basin a 135 km long and up to 35 km wide east west trending basin bracketed by the hines creek fault to the north and the mckinley fault to the south basin fill comprises up to 4000 m of continental deposits interpreted as braided rivers alluvial fans floodplains swamps and ponds crayfish burrows provide evidence of water table level soil moisture fluctuations as well as insight into mean annual temperatures at the time of deposition of the lower cantwell formation a late cretaceous high latitude paleoecosystem despite a relatively high latitudinal setting 71 n paleolatitude the late cretaceous i e campanian maastrichtian mean annual temperature based on the distribution of similar present day crayfish burrows was more like that of southernmost ontario canada where the northernmost burrowing crayfish are found today the burrow depth suggests 1 no permafrost was present and 2 the phreatic zone was 30 50 cm below the paleo ground surface based on the presence of these crayfish burrows the paleoclimate is interpreted as humid continental koppen scheme with average summer high temperatures between 25 c and 28 c and average winter low temperatures between 6 c and 0 c these estimates compare somewhat favorably with previous clamp estimates of a warm monthly mean temperature of 17 08 1 6 c and a cold monthly mean temperature of 2 31 1 9 c

estimating bedrock depth in the case of regolith sites using ambient noise analysis abstract subsurface geometry particularly the depth of bedrock is crucial in seismic hazard studies because the basin geometry has been shown to play an important role in the altering of seismic waves estimating the bedrock surface using ambient seismic noise analysis has been undertaken by many researchers with most studies focusing on sites with a strong impedance contrast between the bedrock and the overlying materials the application of this technique at regolith sites which is subjected to impedance contrasts in the low to high range is underdeveloped and requires further attention this study seeks to address this need and is focused on the city of adelaide in south australia which exhibits site amplification and is associated with various impedance contrasts analyses of ambient noise data are carried out using the generic function gf of the classic horizontal vertical spectral ratio hvsr method and the spatial autocorrelation spac technique to estimate the depth to bedrock comparison of the bedrock depth predictions from the seismic methods with boreholes drilled in close proximity to the measured sites demonstrate that the spac method provides superior estimates especially to those obtained from the other approach this work demonstrates that the microtremor spac method is an effective tool for estimating bedrock structure at regolith sites

palaeoenvironmental reconstruction of the late cretaceous sânpetru formation haţeg basin romania using paleosols and implications for the disappearance of dinosaurs abstract paleosols of the late cretaceous s npetru formation ha eg basin romania are the subject of macroscopic microscopic and geochemical investigation in order to reconstruct the palaeoenvironmental and palaeoclimatic conditions in which dinosaurs lived study of overbank deposits present in an 860 m thick stratigraphic interval of the s npetru formation exposed along the sibisel valley reveals the presence of one facies and five different pedotypes 1 finely laminated gray green mudstones and siltstones interpreted as pond deposits 2 bioturbated gray green mudstones lacking macroscopic pedogenic features interpreted as very poorly developed hydromorphic paleosols 3 bioturbated gray green mudstones containing carbonate concretions interpreted as poorly developed hydromorphic paleosols 4 mottled gray green mudstones containing carbonate concretions and limited illuvial clay accumulation interpreted as moderately developed paleosols characterized by a high but fluctuating watertable 5 bioturbated brown red mudstones lacking macroscopic pedogenic features other than the occasional mottles interpreted as poorly developed paleosols that formed on the higher and better drained floodplains and 6 bioturbated brown red mudstones containing carbonate nodules interpreted as moderately developed calcareous paleosols that formed on distal floodplain settings although limited exposure prevents the documentation of lateral relationships of pedotypes the presence of paleosol profiles that display characteristics of two different pedotypes suggests that they represent a lateral continuum on the landscape related to local differences in hydrology and relief i e catena the pedotype assemblage reveals that the s npetru landscape was a mosaic of wetlands seasonal wetlands and better drained floodplain habitats similar to the present day indogangetic plains pedogenic features and paleosol geochemistry indicate that the maastrichtian climate of romania was subhumid the distribution of pedotypes through the s npetru formation reveals small and large scale palaeoenvironmental changes associated with the shifting of a complex mosaic of wet and dry habitats in response to shifts in river position on the alluvial plain however a major palaeoenvironmental change occurs in the upper s npetru formation where the region was transformed into extensive wetlands such dramatic changes coincide with river competence increase change in palaeocurrent directions and dearth of macrovertebrate remains which had been previously misinterpreted as evidence for the disappearance of dinosaurs at the cretaceous tertiary boundary these palaeoenvironmental changes induced by tectonism are responsible for the shift from preservation of macrofossils concentrated by hydraulic processes into conspicuous lenticular bonebeds in the lower s npetru formation to preservation of microfossil and more rarely macrofossil remains in hydromorphic calcareous paleosols in the upper s npetru formation the consequences of palaeoenvironmental changes on vertebrate preservation mode must be considered in the search for fossils and interpretation of the fossil record

organism substrate interactions and astrobiology potential models and methods abstract organism substrate interactions and their products biogenic structures are important biosignatures on earth this study discusses the application of ichnology the study of organism substrate interactions to the search for present and past life beyond earth three main questions are addressed 1 why to look for biogenic structures i e traces and ichnofabrics beyond earth 2 what biogenic structures to expect on other planets moons and asteroids 3 how to study extraterrestrial biogenic structures review of terrestrial evidence highlights a set of properties that make traces and ichnofabrics important for the search of potential extraterrestrial life trace fossils preserve the activity of soft bodied organisms biogenic structures are resilient to processes that obliterate other biosignatures i e mechanical and chemical degradation diagenesis tectonism and metamorphism traces are very visible biosignatures traces indicate environment and behaviour traces can be universal biosignatures i e biosignatures ideally suited for detecting any type of life a model of organism substrate interactions beyond earth is here proposed expected extraterrestrial traces are those that manifest behaviours that allow to maintain homeostasis excavations meandering traces and biodeposition structures most of the existing rovers and orbiters provide basic instruments for searching these traces it is here suggested that the search for extraterrestrial biogenic structures by rovers would also benefit from artificial adjustable lighting gpr lidar and drilling equipment with optical televiewer in this study open access databases of rover and orbiter imagery have been searched for traces and ichnofabrics but no unquestionable evidence of biogenic structures beyond earth has been found besides those produced by humans this sounds along the lines of the famous fermi paradox if the universe is teeming with aliens where are their traces results of this search show that habitable environments are not the only place to look for biogenic structures non habitable environments such as moons without atmosphere can favour the preservation of shallow tier traces the better preservation potential of traces compared to other biosignatures greatly widens the issue of planetary protection including the interaction between astronauts or vehicles and the substrate may produce disturbances although this study highlights a new direction of study with the tools and concepts of ichnology dialogue between the astrobiological and ichnological communities is needed to use its full potential and possibly answer one of the major questions of science does life exist beyond earth

palaeomagnetism and magnetic anisotropy of proterozoic banded iron formations and iron ores of the hamersley basin western australia abstract rock magnetic properties and palaeomagnetism of weakly metamorphosed banded iron formations bifs of the palaeoproterozoic hamersley group western australia and proterozoic bif derived iron ores have been investigated the bif units sampled here are slightly younger than 2500 ma at paraburdoo mount tom price and mount newman iron ore formation was completed before 1850 ma sampling was mainly from the mount tom price and paraburdoo mining areas and for the first time a palaeomagnetic fold test on fresh unweathered and unaltered bif samples has allowed the nature of the remanence of the bifs to be defined the remanence of the bifs is carried by late diagenetic low grade metamorphic magnetite after primary haematite this remanence is pre folding and is unlikely to be greatly affected by the high anisotropy because the palaeofield inclination was demonstrably low determination of palaeofield directions from measured remanence directions is complicated by self demagnetization effects in strongly magnetic highly anisotropic bif specimens we present a method for correcting measured directions for the effects of self demagnetization and anisotropy for typical bifs the effect of magnetic anisotropy on measured remanence inclinations and inferred palaeolatitudes is minor for low palaeolatitudes but can lead to large errors in calculated palaeopoles for intermediate to moderately steep palaeolatitudes anisotropy also causes cones of confidence to be underestimated due to compression of the range of inclinations in principle deflection of post folding remanence towards the bedding plane by high magnetic anisotropy can produce an apparent syn folding signature with best agreement between directions from different fold limbs after partial unfolding thus high anisotropy cannot only bias estimated palaeofield directions and cause underestimation of errors but can also mislead interpretation of the time of remanence acquisition the anisotropy of anhysteretic remanent magnetization arm probably yields an upper limit to the anisotropy of the chemical remanent magnetization crm carried by the bifs therefore from the anisotropy of arm a maximum inclination deflection of 9 is suggested for the sampled bifs this corresponds to less than 5 change of palaeolatitude the palaeomagnetic pole position calculated for bifs at paraburdoo is 40 9 s 225 0 e dp 2 9 dm 5 8 after tilt correction but without correction for anisotropy other pole positions reported include that from flat lying bifs from wittenoom at 36 4 s 218 9 e dp 4 6 dm 9 1 from mount tom price iron ore at 37 4 s 220 3 e dp 5 7 dm 11 3 and from paraburdoo ore at 36 4 s 209 9 e dp 4 7 dm 8 8 the poles from the bifs the paraburdoo ore and the part of the tom price deposit that was sampled in this study are indistinguishable from each other and from the mount jope volcanics overprint pole the magnetization of the bifs was probably acquired during burial metamorphism of the hamersley group soon before the main folding and uplift event in the southern part of the hamersley province this tectonic event exposed magnetite rich bifs to near surface oxidizing conditions producing extensive martite goethite orebodies and also appears to have produced the syn folding overprint magnetization recorded by the mount jope volcanics of the underlying fortescue group ages of magnetization are tentatively interpreted as 2200 100 ma for the bifs 2000 100 ma for the supergene enrichment of bif to martite goethite ore recorded by the parabudoo and mount tom price orebodies and 1950 100 ma for the metamorphic martite microplaty haematite ore recorded as an overprint by the tom price orebody and as the only surviving magnetization of the mount newman orebody

ichnology and sedimentology reveal depositional characteristics of bay margin parasequences in the miocene amazonian foreland basin abstract proposed depositional models for miocene amazon foreland basin strata pebas formation peru are controversial recent depositional models include lacustrine and tidally influenced brackish water embayment this paper presents data that support tidally influenced brackish water deposition for at least part of pebas time 10 14 ma two parasequences are presented santa julia and tamshiyacu both crop out along the amazon river in upper amazonia near iquitos peru at these locations abundant evidence of brackish water tidally influenced deposition is documented including marginal marine bioturbation sedimentary couplets semidiurnal couplets preserved in burrows and pinstripe lamination the deposits are locally highly bioturbated at both locations ichnogenera normally associated with marine to brackish water depositional environments are common three normally marginal marine ichnofabrics are reported 1 a chondrites reburrowed planolites ichnofabric resident only in massive appearing muds 2 a scolicia laminites thalassinoides ophiomorpha ichnofabric that is manifested as intensely bioturbated silty sands and 3 a thalassinoides generated ichnofabric that is interpreted to have descended into consolidated substrates and is thus representative of the glossifungites ichnofacies several trace fossils contain laminated infills organized into distinct sedimentary couplets that are best interpreted as resulting from semidiurnal processes six conclusions are arrived at 1 sedimentological and ichnological data consistently indicate that sediment accumulation dominantly occurred in sporadically dysaerobic marine to brackish water under a tidal influence 2 sediment accumulation occurred in bay margin environments that prograded into a shallow quiescent bay 3 a stratified water column is indicated by the ichnofauna 4 low accommodation space repetitive and rapid adjustments of relative sea level shallow wave base and a stratified water column combined to generate an atypical parasequence architecture 5 previously published isotopic data are consistent with sediment accumulation in brackish to marine water and 6 marine incursion into amazonia occurred during the middle miocene

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

drilling induced isothermal remanent magnetization the recovery of core samples is important in petroleum exploration mineral exploration and scientific drilling projects and often complete orientation of the samples azimuth and plunge is desirable recovered cores are usually not azimuthally oriented because of the costs associated with deployment and operation of downhole orientation tools inexpensive paleomagnetic orientation methods have been used with considerable success in the borehole environment van der voo and watts 1978 kodama 1984 bleakly et al 1985a b evans and mailol 1986 layer et al 1988 mcwilliams and pinto 1988 in some cases the technique has been hampered by secondary magnetizations associated with the drillstring and or coring tool magnetizations which have partially or completely overprinted the primary and secondary magnetizations used for orientation

trace fossil suites and composite ichnofabrics from meandering fluvial systems the oligocene lower freshwater molasse of switzerland abstract the oligocene lower freshwater molasse of switzerland is host to spectacular outcrops of fluvial deposits in distal areas of the swiss molasse basin deposits of a north eastward draining meandering system are exposed combined sedimentologic and ichnologic observations in the chli sunnhalde and roggwil quarries allow an improved understanding of animal substrate interactions in deposits of meandering fluvial systems strata include meander belt sandstone levee sandstone and mudstone crevasse channel and splay sandstone floodplain mudstone and sandstone and paleosols while the meander belt and the more proximal crevasse channel deposits are typically unbioturbated the more distal deposits show a clear biogenic overprint with distal crevasse channel crevasse splay and floodplain deposits being intensely bioturbated simple grazing and locomotion trails included in the cochlichnus anguineus helminthoidichnites tenuis suite were formed subaqueously in ponded areas of the floodplain meniscate burrows taenidium isp suite and root trace fossils occur along the margin of these floodplain water bodies and at the top of crevasse splay deposits some of the floodplain crevasse splay and crevasse channel deposits are pervasively bioturbated by crayfish burrows camborygma litonomos suite crevasse splay deposits locally host escape trace fossils where cross cutting relationships are apparent a colonization sequence can be established as follows the cochlichnus anguineus helminthoidichnites tenuis suite is cross cut by the taenidium isp suite which in turn is cross cut by the camborygma litonomos suite and root trace fossils composite ichnofabrics are common in these meandering river deposits recording progressive lowering of the water table in overbank subenvironments frequency of depositional events was a first order control on degree of bioturbation position of the water table and degree of substrate consolidation exerted considerable influence over the types of trace fossils produced distinct bioturbation phases may result in the formation of different trace fossil suites representative of disparate ichnofacies preserved on a single bedding plane this study further supports the notion that meandering fluvial systems are characterized by trace fossil suites belonging to the scoyenia camborygma and or mermia ichnofacies

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

large camborygma isp in fluvial deposits of the lower permian asselian dunkard group southeastern ohio u s a abstract the lower washington formation of the lower permian asselian dunkard group in southeastern ohio contains large burrows exposed in cross section in a laterally discontinuous sandstone bed this study examined the morphology of the burrows and their associated lithofacies to interpret the environmental conditions under which they were produced as well as the behavior and identity of the trace maker mudstone facies below and above the burrow bearing sandstone consist of reddish brown to variegated paleosols containing rhizohaloes argillans and large scale slickensides as well as thinly laminated organic rich shales containing plant fossils the sandstone facies is 94 147 cm thick thinly bedded to massive and fine to medium grained the lithofacies are interpreted as deposits of crevasse splays abandoned channels and proximal to distal floodplains sixty burrows consist of vertical subvertical j shaped y shaped and complex networks of branching shafts and tunnels the burrows range from 5 to 180 cm in length and 0 8 3 6 cm in width the main shaft s angles are typically 90 although are rarely 30 70 branching angles of subvertical and y shaped burrows vary from 0 to 90 many burrows extend to the top of the sandstone bed but others turn into or out of the bed the morphology of the burrows is most similar to camborygma known from continental deposits of the permian to recent while camborygma has been previously reported from the permian this is the first occurrence in the late paleozoic appalachian basin extending its geographic range the dunkard burrows are similar to those of modern freshwater decapods particularly crayfish decapod body fossils are not known from the dunkard group yet these burrows are highly suggestive of their presence therefore these fossil burrows contribute to the paleoecological interpretation of the dunkard group helping to fill in gaps of the terrestrial fauna not otherwise preserved in the fossil record decapod burrow morphologies are highly variable depending on burrow function and environment the dunkard burrows are similar to secondary dwellings with few open water attachments multiple branches and shafts likely extending to the water table

avulsion deposits in lower eocene alluvial rocks bighorn basin wyoming abstract eocene alluvial rocks in the northern bighorn basin can be subdivided into three major kinds fine grained deposits on which cumulative paleosols developed lithologically heterogeneous packages associated with immature paleosols and major sheet sandstone bodies the heterogeneous packages which alternate vertically with the cumulative paleosols are dominated by fine grained deposits and also contain ribbon sandstone bodies and thin 1 m sheet sandstone bodies most ribbon sandstones are less than 3 m thick and are more common in the middle and upper parts of the packages cut and fill deposits with fine grained fills are locally important because the lithologic packages are readily apparent in the field because of the immature or simple paleosols developed on the fine grain d facies they are referred to as simple paleosol packages the major sheet sandstones were deposited by meandering trunk rivers and locally overlie and truncate the other deposits contrary to classical models of meandering streams only a portion of the fine grained rocks in the study area were deposited by overbank flooding of a trunk channel on the basis of their stratigraphic position and few ribbon sandstones the upper parts of some simple paleosol packages are interpreted as ancient levee deposits associated with a trunk channel farther from the trunk channel overbank floods deposited alluvium on which the cumulative paleosols formed the greater parts of the simple paleosol packages including their fine grained deposits were deposited rapidly during channel avulsion ribbon sandstone bodies represent ancient splay channels on the avulsion belt simple paleosol packages in the willwood formation support the contention of smith et al 1989 that n many meandering river systems a significant portion of the fine grained deposits were deposited as the trunk channel avulsed deposits that resemble the simple paleosol packages may provide a means of recognizing avulsion episodes in other alluvial sequences

sequence stratigraphic distribution of coaly rocks fundamental controls and paralic examples significant volumes of terrigenous organic matter can be preserved to form coals only when and where the overall increase in accommodation approximately equals the production rate of peat accommodation is a function of subsidence and base level for mires base level is very specifically the groundwater table in paralic settings the groundwater table is strongly controlled by sea level and the precipitation evaporation ratio peat accumulates over a range of rates but always with a definite maximum rate set by original organic productivity and space available below depositional base level groundwater table below a threshold accommodation rate nonzero no continuous peats accumulate due to falling or low groundwater table sedimentary bypass and extensive erosion by fluvial channels this is typical of upper highstand lowstand fan and basal lowstand wedge systems tracts higher accommodation rates provide relatively stable conditions with rising groundwater tables mires initiate and copyright 1997 the american association of petroleum geologists all rights reserved 1manuscript received september 7 1995 revised manuscript received november 25 1996 final acceptance may 5 1997 2exxon production research company 3120 buffalo speedway houston texas 77096 3exxon production research company 3120 buffalo speedway houston texas 77096 present address conoco inc p o box 2197 houston texas 77252 we benefited from the input and assistance of many people of special assistance were the teams involved in collaborative studies with esso australia and esso malaysia p moore m sloan j emmett b burns a partridge s creaney hanif hussein r hill r lovell and m feeley we also thank the rock springs team r beauboeuf p mclaughlin w devlin a carroll y y chen g grabowski jr k miskell gerhardt m farley r webster and j schwalbach group members d curry and j yeakel were always helpful we also enjoyed and profited from many discussions of these concepts with our colleagues outside exxon c diessel r boyd k shanley b zaitlin p mccabe m hendricks a cohen and m kirschbaum we thank the reviewers of company reports whose careful comments on several generations of this work improved it s creaney m feeley j van wagoner f wehr j yeakel and a young f weber and j zullig provided extensive management support k linke translated our sketches into the fine figures herein we value all the help

palaeosols in westphalian coal bearing and red bed sequences central and northern england westphalian a c coal bearing strata and red beds in the pennine basin of central and northern england contain a wide variety of palaeosols in coal bearing facies associations alluvial gley semi gley organic and rare well drained palaeosols reflect the predominance of poor drainage conditions during deposition in red beds more evolved ferruginous and ferallitic palaeosols testify to free drainage conditions during deposition catenary relationships can be inferred between most of the palaeosols in both facies associations providing further information on the palaeogeomorphology of the depositional systems and assisting in the understanding of the environments and conditions of coal seam formation

palaeomagnetism of iron formation from the late palaeoproterozoic frere formation earaheedy basin western australia palaeogeographic and tectonic implications abstract oriented cores of unweathered frere formation 1 9 1 8 ga including shaly and peloidal iron formation were obtained from two holes drilled to 116 m depth on opposite limbs of an anticline in the southern earaheedy basin at the northeastern margin of the yilgarn craton anisotropy of magnetic susceptibility measurements indicated that the frere formation in this area was unaffected by regional metamorphism the predominant magnetic mineral in the iron formation is hematite but a small amount of magnetite also is present in some samples stepwise thermal demagnetisation was conducted for 263 specimens many specimens acquired spurious components of magnetisation after treatment to 300 500 c ascribable to the oxidation of siderite to magnetite on heating however other specimens displayed a stable high temperature 680 c dual polarity component a carried by hematite that gave a bedding dip corrected direction of d 314 3 i 24 8 k 38 5 95 2 6 n 78 a fold test was positive at 99 level of confidence indicating acquisition of remanence prior to stanley folding in the earaheedy basin that occurred at 1 78 ga near the end of capricorn orogenesis the presence of polarity reversals in the stratigraphic section from one drill hole and within some specimens argues for the identification of a dipole field axis and the sufficient averaging of secular variation to define a palaeopole for the frere formation located at 45 2 s 220 0 e dp 1 3 dm 2 4 component a is ascribed to a chemical remanent magnetisation crm acquired soon after deposition and indicates a palaeolatitude of 13 0 1 5 for the frere formation the frere pole plots adjacent to but is still significantly different from late to post capricorn orogeny overprint poles from the hamersley province of the southern pilbara however vertical axis relative anticlockwise rotation of 10 15 for the frere pole brings it close to these pilbara overprint poles the data imply that the earaheedy basin and possibly the yilgarn craton underwent clockwise rotation of 10 15 relative to the pilbara craton during stanley folding this finding accords with evidence for tectonic settings marked by sinistral strike slip deformation adjacent to the yilgarn pilbara cratonic boundary during deposition and subsequent folding in the earaheedy basin the data also imply that the west australian and north australian cratons were in close proximity by 1 8 ga

paleogeographic and paleotectonic setting of laramide sedimentary basins in the central rocky mountain region in the rocky mountain region between central montana and central new mexico sedimentologically isolated nonmarine basins were produced by basement deformation during the laramide orogeny within the area formerly occupied by a broad late cretaceous foreland basin in which laterally continuous marine facies had accumulated previously laramide structures of varying trend and scale reflect heterogeneity of crustal strain caused by shear between the continental lithosphere and an underlying subhorizontal slab of subducted oceanic lithosphere laramide basins include perimeter basins along the cratonic periphery of the arcuate laramide province axial basins along a north south intramontane trend and ponded basins located farther west closer to the overthrust belt twelve specific stratigraphic and sedimentologic criteria for the onset duration and termination of laramide deformation allow the chronology of basin development to be inferred independently for each basin maastrichtian initiation of laramide deformation was approximately synchronous throughout the laramide province but termination of laramide deformation was systematically diachronous from north to south between early and late eocene time widespread eocene erosion surfaces truncate syntectonic laramide sequences and are overlain by largely volcanic and volcaniclastic post laramide strata of eocene age in the north and oligocene age in the south fluvial depositional systems draining toward the great plains were dominant in perimeter and axial basins but ponded basins were occupied at times by large lakes that served as regional sediment traps paleocene drainages from ponded basins also led eastward toward the continental interior but partly interconnected lakes that developed within several ponded basins by mid eocene time were either closed hydrologically or else they drained westward into the tyee paleoriver of the pacific northwest

where is the fossil evidence for gondwanan crayfish abstract crayfish body and ichnofossils recently reported from lower permian and lower triassic strata of antarctica have been reinterpreted to be the body fossils of euthycarcinoid arthropods and the burrows of small to large sized therapsids mammal like reptiles the earliest fossil evidence of crayfish presence and activity in continental deposits is still from the laurasian continents of pangea this evidence is in the form of body fossils and burrows from the upper triassic and burrows from the lower permian of the american southwest for that matter nearly all ichno and body fossils have been described from laurasian rocks with the exception of the occurrence of an isolated claw of a parastacid crayfish from paleogene deposits in queensland australia where is all the fossil evidence for gondwanan crayfish there is a rich extant diversity of parastacid crayfish in australia and they are dispersed between other gondwanan continents with the exception of africa and antarctica paleontological and ichnological evidence when taken into consideration with paleogeographic reconstructions indicates that they originated early during or slightly after the formation of pangea thus at the very least there should be trace and body fossil evidence in australia indicating the long evolutionary history of the parastacids evidence for ancient gondwanan crayfish in terrestrial and freshwater ecosystems should occur in rocks of similar ages to those in north america where ichno and body fossils have been identified

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

crayfish burrows from late jurassic late cretaceous continental deposits of patagonia argentina their palaeoecological palaeoclimatic and palaeobiogeographical significance abstract the trace fossil loloichnus baqueroensis igen and isp nov from late jurassic late cretaceous continental deposits of patagonia argentina includes thickly lined mostly passively filled and y branched burrows other important features of this ichnofossil are the inner surface texture of lining showing transversal elongated and adjacent grooves and less commonly the pelletal filling of burrows l baqueroensis is recorded from the bajo grande bajo tigre punta del barco and laguna palacios formations which were deposited in different volcaniclastic environments of the deseado massif and san jorge basin geological provinces respectively the described burrows are found in many levels of palaeosols developed in reworked piroclastic deposits where they are the main component of the ichnofabrics in association with meniscate and thinly lined burrows and a diffuse and complex boxwork of small diameter burrows root traces are also present and in many cases occur inside l baqueroensis considering general morphology surface texture filling types palaeoenvironments in which they occur and comparisons with extant and fossil decapod burrows the likely trace makers of l baqueroensis were crayfishes decapoda astacidea probably parastacidae the producers of l baqueroensis inhabited soils where their burrows probably reached the water table and contained roots that were used for feeding considering climatic preferences of extant parastacids it is proposed a temperate climate for central patagonia during the deposition of the studied units the widespread presence of crayfishes during late jurassic late cretaceous times in central patagonia supports the monophyletic origin of this group during the triassic and suggests that the present restricted geographic distribution in southern south america is a relict of a broader one

paleomagnetism of the 1 88 ga sokoman formation in the schefferville knob lake area quebec canada and implications for the genesis of iron oxide deposits in the central new quebec orogen abstract thirty nine oriented block samples of iron formation were collected at 13 sites including opposite limbs of major folds from the 1 88 ga sokoman formation knob lake group in the schefferville knob lake area of the central new quebec orogen northern quebec the samples assayed up to 80 24 fe2o3t 54 08 fe implying fe enrichment of the iron formation up to ore grade anisotropy of magnetic susceptibility measurements on 245 standard specimens indicate a well preserved bedding parallel fabric in the iron formation suggesting minimal alteration of the magnetic mineralogy since deposition and or a mimetic secondary magnetic mineralogy the iron formation has not been internally deformed since the magnetic mineralogy was established analyses by variable field translation balance and x ray diffraction showed that the predominant magnetic mineral is hematite but a small amount of magnetite also is present in most samples following low temperature pre treatment as appropriate stepwise thermal and alternating field demagnetization of 218 specimens revealed a low temperature post folding component maximum tub 400 c d 27 1 i 20 1 95 10 9 from seven sites pole position of 40 6 s 257 0 e and components carried by magnetite maximum tub 580 c d 35 8 i 3 9 95 9 1 from 10 sites pole position of 29 6 s 250 9 e and hematite maximum tub 680 c d 40 0 i 1 6 95 18 6 from seven sites pole position of 26 8 s 247 0 e the components carried by magnetite and hematite are pre syn and post folding depending on the sampling site indicating that the magnetization was acquired continuously with deformation in the new quebec orogen at 1 84 1 83 ga no evidence was found for acquisition of magnetization during the mesozoic when many of the iron oxide orebodies in the schefferville knob lake area are thought to have formed our findings imply that an episode of fe enrichment of iron formation in the sokoman formation involved the circulation of hydrothermal fluids related to late paleoproterozoic orogenesis such orogenic circulation of fluids may have contributed to the development of hematitic orebodies in the central new quebec orogen

volcanic and tectonic controls of lacustrine and alluvial sedimentation in the stephanian coal bearing sequence of the malpas sort basin catalonian pyrenees the infill of a small variscan basin shows a complex succession of lacustrine and alluvial sediments whose pattern of distribution through time appears to have changed in response to contemporaneous volcanism following initial deposition of pyroclastic breccias and extrusion of lavas small lakes were established on the floor of the basin their infills were probably locally controlled by relief on top of the lavas but the pattern was disrupted by phases of mass movement from the basin margin which emplaced debris flows and a sedimentary melange containing large blocks of limestone and led to extensive soft sediment deformation this complex sequence of events culminated in the emplacement of a widespread ash flow bed an alluvial plain established during a period of rather uniform subsidence was rapidly drowned to give an extensive lake whose progradational infill led to re establishment of an alluvial plain the deposition of a widespread airfall tuff coincided with the onset of differential subsidence during which major channel sandstones were stacked in association with poorly drained palaeosols in the east of the area whilst a mudstone dominated sequence characterized by well drained palaeosols developed in the west a return to more uniform subsidence appears to have coincided with the cessation of volcanic activity

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

effect of fine scale microstructures in titanohematite on the acquisition and stability of natural remanent magnetization in granulite facies metamorphic rocks southwest sweden implications for crustal magnetism mid proterozoic granulites in sw sweden having opaque minerals hematiteilmenite with minor magnetite and occurring in an area with negative aeromagnetic anomalies have strong and stable reversed natural remanent magnetization 9 2 a m with 100 remaining after demagnetization to 100 mt samples were characterized by optical microscopy electron microprobe emp transmission electron microscopy tem and rock magnetic measurements earliest oxide equilibrium was between grains of titanohematite and ferri ilmenite at 650 600 c initial contacts were modified by many exsolution cycles hematite and ilmenite ilm hosts and lamellae by emp are ilm 24 25 ilm 88 93 like titanohematite and ilmenite above 520 c on burton s diagram 1991 finer hosts and lamellae by tem are ilm16 3 and ilm 88 4 like coexisting antiferromagnetically ordered af hematite and ilmenite below 520 c on burton s diagram this may be the first example of analytical identification in one sample of former hematite now finely exsolved and af hematite tem microstructures consist of gently curving semicoherent ilmenite lamellae within hematite flanked by precipitate free zones and abundant ilmenite disks down to unit cell scale 1 2 nm strain contrast of disks suggests full coherence with the host and probable formation at the reaction titanohematite af hematite ilmenite at 520 c magnetic properties are a consequence of chemical and magnetic evolution of hematite and ilmenite with bulk compositions ilmenite richer than ilm 28 that apparently exsolved without becoming magnetized down to 520 c where hematite broke down to af hematite plus ilmenite producing abundant af hematite below its neel temperature intensity of magnetization is greater than possible with hematite alone and tem work suggests that ultrafine ilmenite disks in af hematite are associated with a ferrimagnetic moment due to local imbalance of up and down spins at coherent interfaces

paleoclimatic implications of crayfish mediated prismatic structures in paleosols of the paleogene willwood formation bighorn basin wyoming u s a abstract paleosols at polecat bench northern bighorn basin wyoming show prismatic structures not previously described in the paleogene willwood formation prisms are densely spaced 15 50 mm diameter cylinders with vertical to slightly sinuous paths up to 400 mm long subangular to rounded vertical faces and slightly concave to convex tops prism exteriors are coated commonly by 1 mm thick clay films exteriors also commonly show knobby and striated surficial morphologies prismatic structures are nearly exclusive to thin bedded 1 m thick compound paleosols composed of red to red purple sandy mudrock overlying gray to green gray heterolithic units composed chiefly of fine grained sandstone in addition to prismatic structures these paleosols are characterized by large gray mottles slickensides and calcareous rhizocretions which crosscut or more typically follow prism exteriors the architectural and surficial morphology of the soil prisms suggest strongly that these are pedogenically modified freshwater crayfish burrows of the ichnospecies camborygma litonomos at polecat bench an 40 m interval of the willwood formation records a transient episode of global warming known as the paleocene eocene thermal maximum petm the petm interval is characterized by a series of predominantly red cumulative paleosol profiles and increased soil carbonates prismatic soil structures and crayfish burrows are rare or absent in cumulic paleosols typical of the petm whereas they are locally abundant in red compound paleosols outside the petm interval the changes in paleosol morphology and a sharp decrease in crayfish burrows within the petm interval suggest significantly improved soil drainage conditions and lower water tables on the willwood floodplain during the global warming event

interactions of a paleocene river a rising fold and early diagenetic concretions abstract the relative rates of sediment accumulation erosion and structural uplift determine whether a growing fold develops positive topographic relief is beveled by antecedent streams or is buried under thick growth strata when folds rise in subsiding basins upward convergent flow of groundwater through the permeable growth strata that underlie antecedent streams enhances the flux of ions required for concretion growth early diagenetic concretions that grow in such alluvial strata may constitute the only clasts larger than sand size available for transport when antecedent streams become erosive the first reworked concretions deposited by these streams should accurately mark the transition from aggradation to erosion as folds rise into the paths of streams in this situation the ability to differentiate reworked from in situ concretions is crucial the west vergent simpson ridge anticline a n s trending thick skinned laramide structure in east central wyoming separates the larger hanna basin from the carbon basin near the north nose of this anticline in situ iron oxide rich concretions are abundant in folded paleocene strata ferris formation and just to the east large reworked iron rich concretions are abundant in younger more gently dipping conglomerates in the basal hanna formation of the backlimb smaller reworked concretions are also present near the base of the hanna formation at least 7 km south of the anticlinal nose and just east of the fold9s axis at the anticlinal nose in situ non reworked concretions up to 3 m 1 m 1 m are abundant at the top of an 7 km thick sequence of sandstones and siltstones that constitute the late cretaceous early paleocene ferris formation reworked concretions are absent in the strata hosting these in situ concretions but reworked concretionary clasts up to 2 m in diameter are present in exposures of conglomerates in the lowermost hanna formation that lie just above the in situ ferris concretions and southeast of the anticlinal nose these early diagenetic concretions were originally cemented by siderite feco 3 oxidation of some small rinded siderite cemented clasts took place after their fluvial transport into the hanna formation but abundant angular un rinded iron oxide cemented clasts indicate that many large in situ siderite concretions had resided in the vadose zone before they were entrained the distribution of reworked concretions and the orientations of crossbeds show that antecedent hanna streams eroded a swath at least 5 km wide across the rising structure these streams transported ferris formation concretions southeastward into the carbon basin and deposited them in a conglomeratic sandstone body in the hanna formation large calcite cemented concretions many with a pipe like morphology then grew within hanna crossbeds in many cases these in situ concretions enclose transported iron rich concretions but there is no evidence any calcite cemented concretions were reworked the nw se alignment of the pipes record southeastward flow of groundwater and thus also provide evidence together with the orientation of the crossbeds of the original continuity of the hanna formation across the anticline reworked concretions reveal the interplay of deposition diagenesis and erosion due to convergent groundwater flow over growing anticlines early diagenetic concretions both in situ and as reworked clasts are especially likely to be found in growth strata

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

ichnofossils of the alluvial willwood formation lower eocene bighorn basin northwest wyoming u s a abstract the ichnofossil assemblage of the lower eocene willwood formation consists of at least nine distinct endichnia that are preserved in full relief four forms three ichnogenera and four ichnospecies are new and represent fodinichnia and domichnia of oligochaete worms an insect or spider an unknown vertebrate probably a mammal and domichnia of an unidentified organism other potential trace makers of the ichnofauna include insects mollusks and decapods in contrast to an egyptian oligocene fluvial ichnofauna produced largely by animals that burrowed in stream channel deposits the willwood assemblage is principally of flood plain origin though the ichnofauna occurs in a variety of paleosol types most of the fossils are restricted in distribution to specific sediment and soil types and within paleosols to specific identifiable horizons this attribute will make them valuable indiced of paleoenvironment once they are better known in other ancient alluvial sequences the environment suggested by the willwood trace fossils damp but not wet soils with fluctuating water tables is consistent with the warm temperate to subtropical possibly monsoonal conditions that are interpreted for the willwood formation by independent evidence of body fossils and paleopedology

paleoclimate controls on stratigraphic repetition of chemical and siliciclastic rocks climate is a primary control on sediment flux from continental sources into sedimentary systems in warm climates siliciclastic input is greatest under highly seasonal rainfall nonseasonal conditions favor formation of end member chemical rocks perennially wet climates are conducive to coal formation whereas dry climates produce carbonates and or evaporites stratigraphic repetition of siliciclastic and chemical rocks therefore appears to be related to paleoclimate cycles as well as to transgressive regressive events and tectonics