deformation sequence of baltimore gneiss domes usa assessed from porphyroblast foliation intersection axes abstract the ne sw trending gneiss domes around baltimore maryland usa have been cited as classic examples of mantled gneiss domes formed by diapiric rise of migmatitic gneisses eskola p 1949 the problem of mantled gneiss domes quarterly journal of geological society of london 104 416 461 476 however 3 d analysis of porphyroblast matrix foliation relations and porphyroblast inclusion trail geometries suggests that they are the result of interference between multiple refolding of an early formed nappe a succession of six fia foliation intersection axes sets based upon relative timing of inclusion texture in garnet and staurolite porphyroblasts revealed 6 superposed deformation phases the successions of inclusion trail asymmetries formed around these fias document the geometry of deformation associated with folding and fabric development during discrete episodes of bulk shortening exclusive top to nw shear asymmetries of curvature were recorded by inclusion trails associated with the vertical collapsing event within the oldest fia set ne sw trend this strongly indicates a large ne sw striking nw verging nappe had formed early during this deformation sequence this nappe was later folded into ne sw trending up right folds by coaxial shortening indicated by an almost equal proportion of both inclusion trail asymmetries documented by the second n s trending fia set these folds were then amplified by later deformation as the following fia sets showed an almost equal proportion of both inclusion trail asymmetries

formation and paleoenvironment of rhizoliths of shiyang river basin tengeri desert nw china abstract rhizoliths found in bed of the late quaternary paleolake zhuyezhe minqin basin central tengeri desert nw china were studied vegetation coverage is present at some locations in the paleolake area although much of the bed area is covered with moving dunes rhizoliths are occasionally eroded out and exposed to the air the morphology of the rhizoliths resembles singular or branching carbonated tubules which are hollow in their central part the rhizoliths are black to grey and are broken and scattered randomly on the sand surface of the lake bed the lacustrine deposits are black greenish silt or silty clay with a large quantity of white petite lake snail shells the possible plant types sources and formation conditions of carbon dioxide and calcium the sedimentary and diagenetic environments and the process of rhizolith formation were discussed via examining rhizoliths macromorphology studying the micromorphology and mineralogy by microscopy cathodoluminescence and scanning electron microscope and studying the chemical compositions of cementing minerals and fragments by energy dispersive x ray spectra the original roots of the rhizoliths belong to hydrophytes such as typha latifolia scirpus maritimus and carex stenophylla lake snails and previous pollen data indicate that the rhizoliths formed in a sedimentary environment of shallow fresh water lake like marginal or palustrine areas during the holocene shallow lake water disturbance by desert wind above the loose sandy sediment or soil was favoring the rhizoliths formation a continuous supply of oxygen through water disturbance led to complete oxidation of roots and producing carbon dioxide dissolution of co2 in water and so carbonic acid production resulted in minerals weathering such as feldspar and primary carbonate particles and the release of k and ca2 ions at presence of co2 and ca2 saturated in the pore water around the roots of hydrophytes within the sediments or soil carbonate precipitation occurred around the root channel and led to rhizoliths formation as tubules the petrifaction process therefore has happened in margin of the paleolake with shallow water and weak redox condition which implies the suitability of rhizolith for reconstructing paleoenvironment

calcic paleosols of the plio pleistocene camp rice and palomas formations southern rio grande rift usa abstract seventy four separate paleosols are recognized in the plio pleistocene camp rice and palomas formations of the southern rio grande rift seven types of profiles are present a bw bk c a bt bk c bw bk c bt bk c bt k c bk c and ak calcic and petrocalcic horizons bk and k commonly overlain by argillic horizons bt dominate most paleosol profiles greater pore size and enhanced permeability typical of sandy and silty parent material favored the development of argillic horizons however micrite is the dominant form of calcium carbonate in bk and k horizons regardless of parent material grain size non calcified a horizons are typically lighter in color than adjacent subsurface pedogenic intervals due to their oxidized nature or lower clay content they are only rarely preserved probably due to erosion prior to final burial calcified root mats ak are not directly associated with other pedogenic horizons abundant horizontal roots suggest root mats formed under high water table conditions restriction of ak horizons to the distal piedmont lithofacies supports their development as spring or pond deposits near the toes of alluvial fans individual pedogenic horizons can often be traced hundreds of meters to kilometers normal and parallel to a basin s axis paleosol maturity and preservation potential are greatest for symmetrical basins especially where pedogenesis was far removed from active channels within the axial fluvial system or within distal piedmont settings of asymmetrical basins

paleoclimatic records of late triassic paleosols from central ethiopia abstract the present study documents the major paleosols types within the lower adigrat sandstone in the blue nile basin of central ethiopia with the aim of unraveling the paleoclimatic signatures embedded in them the paleosols developed within an 80 m thick siliciclastic succession deposited in a mixed tide and wave dominated incised valley estuary during the late triassic based on down profile variations in pedogenic features three major paleosol types i e types i ii and iii were identified type i paleosols dominate the lower part of the section and are interpreted as moderately well drained argillic vertisols the dominant pedogenic process was shrinking and swelling of expandable clays i e smectite through repeated wetting and drying cycles the morphologies and the mineralogy of the paleosols provide persuasive evidence for pedogenesis under semi arid subtropical climatic conditions with pronounced wet dry seasonality highly fluctuating soil moisture regime and deep groundwater table the presence of a calcic bk horizon deep in the profiles is consistent with elevated soil moisture deficits and low to moderate mean annual precipitation map type ii paleosols interpreted to represent vertic gleysols are more common in the middle part of the section the pervasive gleying reflects poor soil drainage and a shallow groundwater table where the soil is waterlogged most of the year these paleosols suggest a humid tropical climate characterized by alternating wet dry seasonality but with more wet months per year the top of the unit is dominated by type iii paleosols that represent gleyed oxisols reflecting a more humid equatorial climate marked by wet seasons elevated annual soil moisture content and a high water table the presence of plinthite laterite is in agreement with a wet equatorial climate characterized by extensive chemical weathering and long periods of landscape stability the observed vertical progression in the major paleosol types from vertsols to gleysols and oxisols implies a systematic change in the number of wet months most probably in response to regional tectonics and long term climate change because the number of wet months is in part related to latitude and monsoonal climates the upward stratigraphic trend in paleosol orders is interpreted to signal the northward or equatorward migration of the blue nile basin and central ethiopia within pangea from dry subtropical low latitudes in the early late triassic carnian norian toward the humid wet equatorial possibly monsoonal paleoclimatic zone in the late triassic norian rhaetian

stratigraphy and sedimentology at bir sahara egypt environments climate change and the middle paleolithic abstract bir sahara situated in northeast africa contains a set of sedimentary sequences that imply episodic changes in climate and environment during the middle and late pleistocene some of the stratigraphic contexts are associated with middle paleolithic artifact assemblages the artifact assemblages are typically in sands that underlie deposits composed of high amounts of carbonate or fine clastics muds indicative of expanding lakes and wetter climates the wetter climates may have provided landscapes that were periodically inhabitable by pleistocene hominids

sedimentological and ichnological analyses of the continental to marginal marine centenario formation cretaceous neuquen basin argentina reservoir implications abstract the upper valanginian lower aptian centenario formation is a significant producer of oil and gas in the neuquen basin western argentina this formation is located exclusively in the subsurface of the eastern and northeastern neuquen basin and is 450 1000 m thick the centenario formation laterally interfingers with the agrio formation previous studies addressing the paleogeographic history of the centenario formation are scarce and a comprehensive geological model has yet to be put forward the current study scrutinizes the centenario formation especially its lower member within the northeastern neuquen basin the study area includes the cerro hamaca oeste senal cerro bayo and volcan auca mahuida oilfields operated by yacimientos petroliferos fiscales ypf sedimentological and ichnological core data geophysical well logs and petrographic thin sections have been utilized to construct a geological model eleven sedimentary facies and three facies associations have been identified from the core dataset providing insights into the paleoenvironmental settings and their stresses on infaunal colonization basin margin deposits from the northeastern part of the study region were formed in continental environments comprising ephemeral fluvial channel complexes and floodplains and are ichnologically represented by rare skolithos and common rhizoliths the central part of the study area is interpreted as recording deposition in ephemeral lakes river dominated lake deltas and coastal lagoons and sabkhas and is represented by a combination of stressed expressions of both the skolithos and scoyenia ichnofacies river dominated storm influenced delta deposits are located towards the southwestern limit of the study area and are ichnologically represented by the skolithos and depauperate cruziana ichnofacies deltaic deposits gradually transition into the basinal facies of the agrio formation to the west overall sedimentologic characteristics suggest semi arid to arid climatic conditions during deposition

a classification of rhizogenic root formed calcretes with examples from the upper jurassic lower cretaceous of spain and upper cretaceous of southern france reply abstract studies of fluvial sequences from the upper jurassic and lower cretaceous of the cameros basin spain and the upper cretaceous of the aquitaine basin france have revealed large numbers of calcrete profiles which have formed wholly or largely through the action of plant root calcification those from spain have formed by the calcification of root mats whereas those from france resulted from the accumulation of calcified root cells microcodium these root related rhizogenic calcretes developed in stages allowing developmental time series chronosequences to be identified contrasting with existing models for calcrete profile growth they provide unique examples where vegetation has been the dominant control on profile development and probably indicate specific vegetation types and palaeoecological settings the role of root activity in forming some quaternary calcretes is also discussed

the distribution and discrimination of shallow authigenic carbonate in the pliocene pleistocene palomas basin southern rio grande rift nine types of authigenic carbonate are present in the pliocene pleistocene alluvial fan and axial fluvial sediment of the palomas half graben in the southern rio grande rift pedogenic and other vadose carbonate includes 1 pedogenic carbonate of stage ii and stage iii morphology underlying bw and bt horizons 2 mudstones in which the carbonate nodules may be pedogenic or the result of shallow groundwater invasion of the vadose zone 3 pedogenic calcic nodules and tubules in eolian sand and 4 gully bed cement of proximal fan conglomerates formed by infiltration and evaporation of surface runoff shallow groundwater carbonate exists as 5 thin 30 50 cm massive beds with an upper fringe of nodules and tubules precipitated at the water table and in the capillary fringe 6 thick 1 5 3 m massive beds deposited by lateral flow of groundwater or at springs and 7 thin 30 cm calcified root mats associated with near surface water saturated sediment or springs phreatic spar cements 8 occupy the interstices of conglomerates and sandstones and locally exist as 9 oriented concretions groundwater carbonates are best developed near the toes of the large hanging wall derived alluvial fans whereas phreatic cement preferentially exists in footwall derived alluvial fan conglomerates pedogenic carbonate is distinguished from groundwater carbonate by the association with other diagnostic paleosol horizons a predominantly vertical arrangement of root traces peds desiccation cracks and calcic tubules and by gradational contacts the 13 c and 18 o values are similar among pedogenic and shallow groundwater carbonate although locally nodules in eolian sand and gully bed cement have higher 18 o values perhaps due to the effects of evaporation some phreatic cements may be distinguished from pedogenic and shallow groundwater carbonate by lower values of 13 c and 18 o authigenic carbonate in footwall derived alluvial fan sediment has consistently higher values of 13 c than that in hanging wall derived sediment which may reflect differences in vegetative type and or density on either side of the basin

multiproxy studies of early miocene pedogenic calcretes in the santa cruz formation of southern patagonia argentina indicate the existence of a temperate warm vegetation adapted to a fluctuating water table abstract the lower miocene santa cruz formation in southern patagonia austral basin argentina contains several horizons of pedogenic calcretes which record 17 5 myr old vegetation adapted to a shallow and fluctuating water table at paleolatitude of 56 s to reconstruct the paleoenvironment paleoclimate and paleoecosystem we performed a multiproxy study of the calcretes examining abiotic and biotic components the calcretes exhibit a variety of morphologies horizontal and vertical rhizoliths laminar structure nodules massive crusts microfabrics beta predominant over alpha microfabrics and 18o and 13c values that fluctuate within each morphotype and throughout the analysed interval microfossils and phytoliths in the host material of the calcretes indicate fluctuating terrestrial freshwater and marine conditions and record an ecosystem dominated by herbaceous plants and arboreal elements in association with a typical coastal santacrucian vertebrate fauna we propose that the calcretes developed in soils in a coastal fluvial setting during pauses in floodplain aggradation that typically lasted between 8 25 ka and 400 ka years variable sedimentation rates in different parts of the coastal fluvial floodplain the fine texture of the host sediment and the influence of a fluctuating water table also influenced the formation of the calcrete a high water table in low relief areas of the floodplain created the conditions necessary to form a horizontally extended rhizolithic system that jointly with the biotic proxy can be correlated with a radicular pattern similar to the arboreal elements from coastal settings abiotic and biotic proxies of the studied interval attest to environmental fluctuations recorded at different scales that took place under temperate warm and subhumid climates with a marked rainfall seasonality with a slight increase in the aridity towards the top of the studied interval under these conditions a subtropical fauna and a c3 dominated ecosystem developed coincident with the onset of the mid miocene climatic optimum in patagonia

constraining uncertainty in interpretation of seismically imaged clinoforms in deltaic reservoirs troll field norwegian north sea insights from forward seismic models of outcrop analogs forward seismic modeling of outcrop analogs has been used to characterize the seismic expression of clinoforms in different deltaic depositional environments and thus constrain uncertainty in interpretation of intra reservoir clinoforms imaged in seismic data from the troll field norwegian north sea three outcrop analogs from the cretaceous western interior seaway united states were studied to quantify the geometry distribution and lithologic character of clinoforms in fluvial dominated and mixed influence deltaic deposits outcrop derived geometric data were calibrated to sedimentological and petrophysical data from the krossfjord and fensfjord formations in the troll field and then used to create a suite of forward seismic models for comparison with real seismic reflection data from the troll field clinoforms were imaged in the forward seismic models in which they were 1 spaced wider than the tuning thickness 10 m 33 ft 2 marked by pronounced interfingering of facies associations with different acoustic properties and or 3 lined by relatively thick 50 cm 20 in carbonate cemented layers however where clinothems are thinner than the vertical resolution limit of seismic data destructive interference occurred creating misleading geometrical relationships furthermore our ability to image clinoforms is dependent on 1 the frequency of the seismic wavelet 2 the overburden velocity and or 3 the acoustic impedance contrast at the boundary between the overburden and the clinoform bearing target the established methodology has allowed characterization of deltaic clinoformal architectures in reservoir seismic data from the troll field and has facilitated a more robust interpretation by bridging the critical gap in resolution between well and seismic data

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

lower miocene gypsum palaeokarst in the madrid basin central spain dissolution diagenesis morphological relics and karst end products the miocene sedimentary record of the madrid basin displays several examples of palaeokarstic surfaces sculpted within evaporite formations one of these palaeokarstic surfaces represents the boundary between two main lithostratigraphic units the miocene lower and intermediate units of the madrid basin the palaeokarst formed in lacustrine gypsum deposits of aragonian age and corresponds to a surface palaeokarst epikarst further buried by terrigenous deposits of the overlying unit karst features are recognized up to 5ae5 m beneath the gypsum surface exokarst and endokarst zones are distinguished by the spatial distribution of solution features i e karren dolines pits conduits and caves and collapse breccias sedimentary fills and alteration of the original gypsum across the karst profiles the development of the gypsum palaeokarst began after drying out of a saline lake basin as supported by recognition of root tubes later converted to cylindrical and funnel shaped pits at the top of the karstic profiles the existence of a shallow water table along with low hydraulic gradients was the main factor controlling the karst evolution and explains the limited depth reached by both exokarst and endokarst features synsedimentary fill of the karst system by roughly laminated to massive clay mudstone with subordinate carbonate and clastic gypsum reflects a punctuated sedimentation regime probably related to episodic heavy rainfalls typical of arid to semi arid climates duration of karstification is of the order of several thousands of years which is consistent with previous statements that gypsum karstification can develop rapidly over geologically short time

paleoenvironmental interpretation of lake margin deposits using δ13c and δ18o results from early pleistocene carbonate rhizoliths olduvai gorge tanzania isotope analyses of lake margin rhizoliths from paleo lake olduvai ca 1 75 ma form the basis of a new model proposed here for interpreting stable isotope values of phreatic rhizolith carbonates average 18o and 13c values from rhizoliths formed in transgressive lacustrine waxy claystones are relatively low low 18o averages 5 5 reflect meteoric water values consistent with increased precipitation during wet periods that would increase the outflow of fresh water from subsurface seeps and shift a brackish groundwater zone lakeward low 13c averages 4 1 could indicate little atmospheric exchange high plant decay and or increased groundwater low 13c flow higher averages in 18o 3 6 and 13c 2 0 occur during dry periods and lake regressions earthy claystones when hydraulic head is reduced the lake recedes and water within the wetlands is subjected to intense evaporation and gas exchange with the atmosphere the isotope ratios of the rhizoliths from lowermost bed ii change in response to groundwater hydrology on milankovitch time scales but the isotopes also provide evidence of shorter term decadal to centennial scale climate fluctuations the orbitally driven climate changes are recorded faithfully by lithologic variations and stable isotope patterns

using petrography and geochemistry to determine the origin and formation mechanism of calcitic plant molds rhizolith or tufa rhizoliths root casts and rhizocretions are prolific in the geologic record and their morphology and isotopic signatures can be important indicators of paleoenvironment and paleoclimate in a semiarid playa in nevada the calcite plant encrustations preserved at the playa surface resemble rhizoliths morphologically and would seem to indicate pedogenesis and root activity the features are preserved as short thin upright and or overturned tubes that often exhibit an apron at the base branching is rare and the tubes can be filled with sediment or calcite or left open however detailed macroscopic microscopic and geochemical analyses of these features reveal that they are instead macrophyte stem encrustations that form in standing water while these features form in a manner similar to paludal tufa they do not resemble typical tufa deposits e g barrages mounds cascades instead they mimic rhizoliths this study describes the macroscopic and microscopic characteristics of these features and distinguishes them from rhizoliths so that they can be accurately identified in the geologic record furthermore this study identifies a more appropriate method of interpreting the stable isotope values of these tufa like plant molds these types of carbonates are faithful recorders of ambient aquatic conditions e g geochemistry as well as local hydrologic parameters e g water depth when the playa surface is flooded but their geological application is restricted to a partial annual signal e g plant growing season presence of standing water on the playa it is important to correctly identify these types of plant encrustations in the geologic record since 1 their presence indicates a shallow standing body of water rather than a paleosol and 2 their isotopic composition records not only an ambient aquatic signal but an extremely restricted climatic signal that should not be interpreted with models for pedogenic carbonates

trace fossils and rhizoliths as a tool for sedimentological and palaeoenvironmental analysis of ancient continental evaporite successions abstract recognition of evaporite formations from continental tertiary basins of spain provides evidence that trace fossils including rhizoliths can be abundant in some saline lake systems and their study helps in palaeoenvironmental interpretation of ancient continental evaporite sequences six main types of trace fossils have been distinguished and include 1 networks of small rhizoliths 2 large rhizoliths 3 tangle patterned small burrows 4 isolated large burrows 5 l shaped traces and 6 vertebrate tracks rhizoliths were related to both marginal areas of hypersaline lakes and lakes of moderately high saline waters in these settings pedoturbation resulted from colonization by grasses and bushes of distinct lake subenvironments the activity of burrowing invertebrate faunas was especially intense in lakes of moderately concentrated brines from which gypsum was the main evaporite mineral deposited a specific gypsum lithofacies bioturbated gypsum deposits forming thick massive beds has a widespread occurrence in many of the basins tangle patterned small burrows and minor isolated large burrows constitute the typical trace fossil types within the gypsum the traces are interpreted as having been caused by burrowing insect larvae probably chironomids coleopterans and annelids the behaviour of these organisms in recent lake environments yields information about the salinity range of lake waters from which gypsum precipitated concentration values averaging 100 150 g l may be thus deduced though some organisms involved in the formation of the traces can tolerate higher salinities the combined analysis of lithofacies and trace fossils from the lacustrine evaporite sequences contributes to the study of distinct saline lake subenvironments as well as changes in the sedimentary evolution of the lake systems consequently trace fossils can provide valuable insight for palaeoenvironmental analysis of at least some evaporite formations that accumulated in continental settings

paleosols as indicators of paleoenvironment and paleoclimate paleosols are ancient soils that have been incorporated into the geological record soils form in response to interactions among the lithosphere hydrosphere biosphere and atmosphere so paleosols potentially record physical biological and chemical information about past conditions near earth s surface as a result paleosols are an important resource for terrestrial environmental and climatic reconstructions long standing paleosol research topics include morphology classification and clay mineralogy all of which provide information about pedogenic processes and local paleoenvironments paleosols are also used to infer processes involved in the development of stratigraphic architecture and basin evolution recent paleosol research has introduced semiquantitative and quantitative measures for environmental and chronometric reconstructions that provide insight into major regional to global changes in temperature precipitation and atmospheric pco2 these new proxies focus on morphological and chemi

paleoenvironments of root casts from the koobi fora formation kenya a study of fossil mots and root casts from east turkana kenya has shown them to be useful paleoenvironmental indicators fossil root casts were obtained from the pleistocene upper member of the koobi fora formation deposited within the east turkana embayment of the lake turkana basin lithofacies and biofacies analysis of the study locality allows the discrimination of several important environments which contain root casts notably fluvial channels and shallow lacustrine conditions five common root cast morphologies have been observed 1 horizontal planar root mats 2 vertical or vertically branching structures 3 horizontal or horizontally branching structures 4 diagonally branching structures and 5 root balls concretionary structures root cast morphology is shaped both by the original root morphology and post mortem diagenetic development line transect surveys of fossil root casts reveal two striking lithofacies root cast associations laminated siltstones of the shallow lacustrine environment primarily contain root mats and horizontal roots whereas sandstone conglomerates of the fluvial paleochannels contain predominantly vertical and diagonal root casts with no root mats studies of plant associations in the lake turkana area and work on modern root morphologies suggest a probable explanation for these associations in arid environments water availability is a dominant factor in root morphology plants growing along intermittent streams or floodplains must frequently rely on perched water bodies or deeper phreatic water therefore sending out long vertical tap roots to take advantage of this resource plants living in permanent shallow lacustrine environments or other areas where phreatic water is quite shallow have no such requirement since their roots are nearly continuously immersed in ground water during floods the plant stalk itself is subaqueous the roots of these plants tend to extend laterally in thin mats over large areas thus a study of root cast morphologies may allow for an assessment of paleogroundwater conditions in nonmarine sediments

biogenic structures in exhumed surfaces around saline lakes an example from lake bogoria kenya rift valley abstract five overprinted suites of animal and plant traces around saline alkaline lake bogoria kenya are described from a set of interfingering late pleistocene and holocene exhumed surfaces that reveal a complex story of changes in lake level and environmental controls on trace assemblages through time these stratigraphic surfaces are amalgamated and form a co planar surface the sediments were first deposited during intermediate lake levels then reworked and cemented during low lake levels and were subsequently overlain by transgressive lacustrine sediments during higher lake levels ongoing exhumation of the surface near the present shoreline has reactivated the sediments as a substrate for the activities of epifaunal and infaunal animals as well as plant growth the modern environmental setting at lake bogoria is very similar to that of the preserved exhumed surfaces which allows comparisons between observed sets of environmental factors affecting animal behaviour and their representation in the fossilized examples pronounced lateral environmental heterogeneity around saline and hypersaline lakes may lead to concentrations of life around sites with vital resources such as freshwater at lake bogoria groups of fault controlled hot springs represent these oases and have been a relatively consistent feature in and around the lake during the development of the exhumed surfaces together the diverse assemblage of animal trace suites from lake bogoria represent the mermia and scoyenia ichnofacies but can be divided into five suites that reveal details of laterally heterogeneous sets of environmental factors and are useful indicators of lake level substrate moisture content substrate cohesion etc suite 1 comprises the traces of chironomid larvae diptera chironomidae formed in subaqueous lacustrine settings suite 2 includes the traces of flamingos phoeniconaias minor and phoenicopterus ruber formed at the shoreline suite 3 compares well with the mermia ichnofacies and comprises trails and burrow systems associated with relatively fresh saturated to extremely shallow subaqueous substrates suite 4 is comparable to both the pre and post desiccation suites of the scoyenia ichnofacies is the most diverse suite at lake bogoria and mainly comprises the burrows of beetles earwigs and their larvae as well as a diverse set of rhizoliths and vertebrate tracks suite 5 contains a moderately diverse set of traces attributed to termites and ants

biogenic features in calcretes developed on mudstone examples from paleogene sequences of the himalaya india abstract calcrete occurring in the paleogene sequences of the western himalayan foreland basin offers very useful information regarding climate and paleogeography of northern part of the indian subcontinent these calcretes possess variety of biogenic features beta fabrics that include rhizoliths alveolar septal and vermiform fabric and microcodium the microcodium rosettes show filamentous structures the rhizoliths and alveolar septal fabric formed by the precipitation of carbonate in soil vadose zone and the vermiform fabric may be a root mat perhaps microbes helped in dissolution of carbonate fillings and they were instrumental in precipitation of calcite in the form of rosettes and filaments here the filamentous structure in the microcodium is significant we suggest that the microcodium formed as a result of fungal dissolution and microbial mediation the lighter values of 13 c and 18 o