observations on the dispersion and aggregation of clays by humic substances i dispersive effects of humic acids abstract although humic substances are normally considered as aggregating agents in soil formation processes we have shown that within a certain concentration range humic substances are also able to disperse soil particles the dispersive effect was particularly evident at humic acid concentrations of around 40 mg l 1 at higher concentrations the action was less effective at 40 mg l 1 humic acids were between 20 and 30 less effective than the commonly used hexametaphosphate at 0 4 no significant differences were observed between the performance of humic acids at 40 mg l 1 and calgon at 0 5 when the performance of humic acid was compared with that of hexametaphosphate of equal strength 40 mg l 1 the former appeared approximately 140 times more effective for the dispersion of the fine clay fraction

sedimentation organic maturity and petroleum potential of the oligocene miocene oil shale deposits yayu basin southwestern ethiopia studies initiated in the search for domestic energy supplies for ethiopia have confirmed the presence of oil shales in the yayu basin this article presents some of the characteristics of these shales the basin is located in the southwest of ethiopia and consists of precambrian basement and cenozoic volcanic and sedimentary rocks three sedimentary successions reach a cumulative maximum thickness of 165 m 541 ft two oil shale horizons have been identified in the upper and lower sedimentary successions and reach a maximum thickness of 35 and 20 m 115 and 65 ft respectively sedimentation in the basin occurred in fluvial and lacustrine depositional environments the sandstone facies was deposited in a fluvial environment whereas the oil shale bearing sediments were deposited in a lacustrine environment algal amorphous materials and minor amounts of woody materials characterize the studied oil shales with botryococcus and pediastrum indicating a lacustrine environment the studied oil shales are characterized by high total organic carbon values up to 61 2 and s2 hydrocarbon generating potential values ranging from 10 78 to 119 07 hc g kg indicating excellent source rocks most of the oil shales are at the immature to early mature stage for hydrocarbon generation vitrinite reflectance measurements on the oil shale samples are less reliable because of the presence of abundant algal materials gas chromatogram results also indicate source rocks the yayu basin is estimated to have up to 1 billion metric tons of oil shale reserves

late paleozoic glacial episodes in gondwanaland reflected in transgressive regressive depositional sequences in euramerica the late paleozoic glaciation of gondwanaland comprised two short episodes in the famennian i and visean ii confined to brazil and adjacent northwest africa and a long episode that started in the namurian iiia of eastern australia and bolivia argentina expanded to cover much of gondwanaland in the stephanian asselian iiib and collapsed in the early sakmarian iiic dropstones in eastern australia indicate that small ice centers lingered to the kazanian across the belt of low latitudes north of gondwanaland short ranging fossils in widespread shallow marine and paralic deposits indicate synchronous deposition of transgressive regressive sequences in different parts of euramerica these sequences correlate with glacial events in gondwanaland at three levels a four major regressions in euramerica in the famennian 1 visean 2 namurian 3 stephanian 4 and the tastubian transgression that preceded the sterlitamakian regression 5 also recorded in gondwanaland correlate with glacial episodes i ii and iiia iiib and iiic b the time interval of cyclothemic deposition in euramerica brigantian or latest visean to sterlitamakian correlates with that of glacial episode iii and c the dominant period of the euramerican cyclothems as estimated from the middle and late pennsylvanian deposits of the mid continent of north america and of the thickest known gondwanaland glacigenic sediment the earliest permian lyons group of western australia is 0 4 ma equivalent in turn to the long orbital eccentricity period of the quaternary ice age and the dominant period of fluctuation of the late miocene antarctic ice cap the three levels of correlations confirm wanless and shepard9s 1936 hypothesis that the late paleozoic cyclothems are controlled largely by sea level fluctuations related to the gondwanaland glaciation

milankovitch forcing of fluctuations in the level of tropical lakes from 18 to 0 kyr bp an atmospheric general circulation model has been used to simulate the climates of january and july at 3 000 yr intervals from 15 kyr bp onwards the model simulates a strengthened monsoon circulation and increased precipitation in the northern hemisphere tropics culminating at 9 6 kyr bp the computed hydrological budgets were used to estimate the area of closed lakes between 8 9 and 26 6 n giving with minor exceptions results in good agreement with geological evidence

facies sequences of a semi arid closed basin the lower jurassic east berlin formation of the hartford basin new england u s a the lower jurassic east berlin formation exposed in the centre of the hartford basin can be divided into six facies 1 laminated black mudstone is composed of very finely laminated organic bearing clay stone with common millimetre scale lenses of dolomitic siltstone 2 planar laminated mudstone is commonly mudcracked and composed of thickly laminated red green or grey mudstone with common centimetre scale lenses of sandstones 3 disrupted mudstone has a complex desiccation cracked fabric 4 planar and large scale trough cross stratified sandstones are composed of moderately well sorted medium to coarse grained arkoses 5 small scale cross stratified silty sandstones with common climbing ripple structure and 6 interbedded sandstones and mudstones which commonly carry desiccation cracks mudstone facies are organized into repetitive metre scale facies sequences which change gradationally upwards from laminated black mudstones to planar laminated mudstones to disrupted mudstones facies sequences have sharp tops and bottoms and record increasing desiccation upwards there are 15 such cycles in the upper 100 m of the formation in central connecticut they record long periods of dry playa mudflat aggradation punctuated by the rapid expansion and contraction of perennial lakes the sandy facies occur as single decimetre scale sedimentation units or as two or more stacked sedimentation units up to 1 m thick these record sheet floods across ephemeral floodplains

sequential architecture and cyclicity in permian desert deposits brodick beds arran scotland this study of ancient desert deposits permian brodick beds tests the possibility that cyclicityin these interbedded aeolian fluvial and lacustrine deposits was orbitally controlled the 740 m thicksuccession of desert deposits forms one sequence which can be divided into three genetic units a majordeflation surface forms the basal sequence boundary and represents a drop in base level groundwatertable on top of the sequence boundary are rather uniform aeolian dune and sand sheet sediments unit1 formed in an erg during low base level with increasing rates of base level rise they are followed byinterbedded aeolian dune aeolian sand sheet and flood reworked aeolian sediments unit 2 representingerg margin deposits formed during increasing rates of base level rise the uppermost part of the sequenceis composed of gravel sheets unit 3 representing alluvial fan deposition during a high base level withdecreasing rates of base level rise the succession is cyclic and spectral analysis of sedimentary andgeochemical parameters reveal cycles with a thickness of 25 7 29 3 m 34 5 m and 64 5 m and fieldworkreveals cycles of 155 m and 675 m these sedimentary cycles are thought to reflect climatic oscillations the lack of detailed time control makes it diffcult to link these climatic fluctuations to orbital cycles although the detected cyclicity matches well with milankovitch theory

chemical and mineralogical properties of soils in southeastern nigeria in relation to aggregate stability abstract the objective of this study was to relate the major chemical and mineralogical properties of soils formed on sedimentary deposits in southeastern nigeria to the stability of their aggregates at both the macro and micro colloidal levels five profiles and twenty five topsoil samples representing four major geological formations were studied the soils are classified as entisols and ultisols the soils are low in exchangeable cations at both the macro and colloidal levels of aggregation these cations and cec were found not to have any positive influence on structural stability a positive correlation coefficient r 0 86 existed between fe 2 o 3 and aggregated silt clay asc and water unstable aggregates wsa r 0 80 the major aggregating agent at the colloidal level was found to be fe 2 o 3 the mineralogy of the soils is dominated by kaolinite while the smectite observed in some wetland soils are assumed to be transported from drier areas soils containing smectites were more weakly aggregated and hence more structurally fragile than soils dominated by kaolinite

proterozoic fluvial styles response to changes in accommodation space rivieradal sandstones eastern north greenland abstract fluvial styles recorded by the uppermost part of the neoproterozoic rivieradal sandstones succession of eastern north greenland reflect variations in rate of generated accommodation space and possibly climatic changes three facies associations arranged in two genetic sequences are recognised within the succession the lower sequence initially records little available accommodation space a high degree of reworking results in sheet like high energy bed load dominated braided river deposits lacking recurrent facies patterns as accommodation space increases upwards through the sequence reduction in reworking is recorded by the development of fining and thickening upward muddy fluvial cycles evidence of desiccation or prolonged periods of drought are absent within the deposits and climate was probably relatively humid channel deposits in the lower sequence reflect mixed load braided fluvial systems with stable channel banks and floodplains and the gradient appears to have been low to moderate these features are generally considered favourable for the establishment of meandering river systems but channels nevertheless retained an overall braided character and their deposits show no evidence of meandering despite indications of a climatic setting without significant periods of drought sediments indicate that large fluctuations in discharge occurred within the mixed load streams and this is suggested to be the main cause for the absence of meandering the swift and rather dramatic response of the fluvial systems to changes in precipitation probably resulted from rapid runoff rates caused by the absence of vegetation the upper sequence shows an initial return to shallow sandy braided river deposition recording little available accommodation space a subsequent increase in the rate of generated accommodation space is indicated by the presence of alternating sheet sandstones and sand streaked mudstones with abundant desiccation cracks the sheet sandstones show evidence of high energy unconfined ephemeral fluvial flash flood deposition while the mudstones are interpreted to represent muddy floodplain deposits the change in fluvial style combined with the widespread evidence of desiccation suggest an evolution towards a more semi arid climate in the upper sequence this climatic change could account for the reduced clastic input seen in the overlying marine succession which culminated in carbonate platform deposition the present study suggests that even under conditions considered favourable for the formation of meandering streams these will rarely occur in proterozoic deposits due to the lacking influence of vegetation although meandering deposits cannot be ruled out as having formed in pre vegetational times the conditions for their formation appear to have been even more restricted than previously realised

erg margin deposits in the lower jurassic moenave formation and wingate sandstone southern utah the moenave formation dinosaur canyon member and the closely associated wingate sandstone in southern utah represent the southwestern erg margin of the lower jurassic wingate erg the erg margin deposits which extend across a 50 to 100 km wide region are composed of dune eolian sand sheet mud flanked eolian sabkha ephemeral stream and lacustrine facies the succession is divided into a basal erg margin association 8 27 m dominated by eolian facies and an overlying erg margin association as much as 90 m thick composed mainly of fluvial and lacustrine facies the sediments of the basal association are composed of three drying upward or locally drying wetting upward sequences that can be traced from the erg margin 100 km slightly upwind that is toward the west northwest into the outer erg margin zone sequences of the inner erg margin zone contain dune facies in their upper parts sequences in the intermediate erg margin zone contain sand sheet facies and those in the outer erg margin zone contain sabkha facies the basal association thins markedly toward the west northwest sediments of the overlying association contain up to six drying upward or drying wetting upward sequences but are apparently only fully preserved in the outer erg margin zone individual sequences show much lateral variation but characteristically contain lower muddy ephemeral stream deposits and upper sandy ephemeral stream deposits sand sheet deposits or incipientdune deposits the general time trend is interpreted as a gradual change toward a more humid climate the stacked drying upward or drying wetting upward sequences suggest that this long term climatic change was characterized by a number of fluctuations between relatively arid and humid conditions these climatic fluctuations apparently controlled both sediment yield to the basin and the depositional conditions in the erg margin region during arid intervals ephemeral braided streams transported sandy bed load into the erg margin area where eolian reworking took place during humid intervals sheet floods and high sinuosity rivers transported a more mud rich sediment load into the basin where eolian activity was minimal

a 2 3 million year lacustrine record of orbital forcing from the devonian of northern scotland detailed sedimentological examination of onshore sections through cyclic lacustrine deposits of the middle devonian succession of northern scotland has been augmented with offshore data to allow the construction of a continuous 2 3 myr record of orbital forcing these data provide an important record of climatic variance through the devonian which by comparison with other records from this time can significantly improve our understanding of the devonian global climatic system precessional and eccentricity cycles are shown to be dominant by the direct measurement and extrapolation of depositional rates in well exposed sections as well as the analysis of ratios between primary and modulating cycles spectral analysis has confirmed the presence of regular cycles throughout the offshore data which provide a far longer record of orbitally forced cyclicity than previously available the presence of a half precession cycle is also suggested similar up section variations in cycle thicknesses are recorded from both the onshore and offshore succession these variations and those in cycle symmetry are related to a trend from an underfilled to a balanced fill basin state of further importance in controlling cycle thickness is the period of each cycle during which lacustrine conditions and therefore lake level controlled accommodation existed

lower eocene alluvial paleosols willwood formation northwest wyoming u s a and their significance for paleoecology paleoclimatology and basin analysis abstract the lower eocene willwood formation of northwest wyoming is a 700 m thick accumulation of alluvial floodplain and channel mudstones and sandstones nearly all of which show paleopedogenic modifications pedogenesis of willwood sandstones is indicated by taproot and vertebrate and invertebrate bioturbation early local cementation by calcium carbonate and thin illuviation cutans on clastic grains pedogenesis in willwood mudstones is indicated by plant bioturbation insect and other invertebrate burrow casts and lebensspuren free iron aluminum and manganese mobilization including hydromorphic gleying sesquioxide and calcareous glaebule formation in lower parts of the solum presence of clay rich and organic carbon rich zones and well differentiated epipedons and albic and spodic horizons probable a horizons are also locally well developed occurrence of variegated paleosol units in thick floodplain mudstone deposits and their association with thin lenticular and unconnected fluvial sandstones in the willwood formation of the central and southeast bighorn basin suggest that these soils formed during times of rapid sediment accumulation the tabular geometry and lateral persistence of soil units as well as the absence of catenization indicate that willwood floodplains were broad and essentially featureless all willwood paleosols were developed on alluvial parent materials and are complex in that b horizons of younger paleosols were commonly superimposed upon and mask properties of suspected a and b horizons of the next older paleosols the soils appear to be wet varieties of the spodosol and entisol groups aquods and ferrods and aquents respectively though thick superposed and less mottled red purple and yellow paleosols resemble some ultisols most willwood paleosols resemble warm temperate to subtropical alluvial soils that form today under alternating wet and dry conditions and or fluctuating water tables the up section decrease in frequency of gley mottles increase in numerical proportion and thickness of red versus orange coloration and increase in abundance of calcrete glaebules indicate better drained soils and probably drier climate in late willwood time this drying is believed to be related to creation of rain shadows and spacing of rainfall but not necessarily decrease in absolute rainfall due to progressive tectonic structural elevation of the mountainous margins of the bighorn basin

sedimentology and hydrogeology of two braided stream deposits abstract two approaches were used to quantify the spatial distribution of hydrofacies in braided stream deposits one approach involved mapping a 50 by 60 by 3 3 m section of a proximal braided stream deposit in a second study we generated a 400 by 400 by 2 6 m section of a medial braided stream deposit using a computer model in both cases we produced three dimensional images showing connected hydrofacies with high permeabilities that form preferential flow paths this information was input to a groundwater flow model and flow paths were analyzed by following the transport of imaginary particles in both systems particles that were uniformly distributed at the up gradient end of the model clustered along preferential flow paths during transport showing that connection among high permeability facies is a critical factor in hydrogeological investigations involving assessment of contaminant movement and remediation

sea level changes an integrated approach sea level changes an integrated approach in october 1985 sepm sponsored a four day conference entitled sea level changes an integrated approach the purpose of the conference was to provide a forum for an interdisciplinary exchange of ideas on sea level changes and to provide an opportunity for integrating various types of evidence in approaching unresolved issues the conference was successful in bringing together scientists from industry academia and government representing all of the major geosciences disciplines presentations of many new papers plus significant releases of data that were previously held proprietary provided fertile ground for discussion this much cited volume represents the best of the material presented at the conference includes the early vail chart

geostatistical analysis of aquifer heterogeneity from the core scale to the basin scale a case study this study examines the spatial variability of conductivity within the sandstone wabiskaw member of the lower cretaceous middle mannville in the alberta basin the wabiskaw is an important regional hydrostratigraphic unit vertical variability within the aquifer is characterized by downhole variograms of log conductivity from core measurements they are found to exhibit pseudoperiodic structures due to alternating sand and shale layers horizontal spatial variability is characterized using variograms of log transmissivity and indicator data these variograms show a steady increase in spatial variability over length scales ranging from 400 m to 100 km characteristic of self similar or fractal behavior they also reveal distinct correlation structures related to both high and low transmissivity depositional features this study also considers the upscaling of conductivity vertically from the core to the well scale and horizontally from the well to the basin scale it is shown that traditional vertical upscaling of conductivities by arithmetic averaging causes an overestimation of transmissivity in two dimensional areal flow models an alternative approach based on power averaging is proposed transmissivities derived by vertical upscaling of core measurements are compared with values derived from drill stem tests in the same well no correlation between these quantities is observed an average transmissivity for the wabiskaw in the study area is determined by geometric spatial averaging however the highly clustered spatial distribution of well locations requires a weighting of sample values using ordinary kriging

quantitative integration of hydrogeophysical data conditional geostatistical simulation for characterizing heterogeneous alluvial aquifers high resolution geophysical parameter information as it can be provided for example by crosshole georadar and seismic tomography has proven to provide useful spatial information to complement traditional hydrological methods such as core analyses logging techniques and tracer or pumping tests quantitative integration of these diverse database components is one of the major challenges in the field of high resolution hydrogeophysics because of their different scales of measurement and the usually weak petrophysical relations among the measurements in this study we systematically explore the usefulness of a conditional stochastic simulation approach based on simulated annealing for this purpose first we generate a realistic model of an alluvial aquifer consisting of a 2d scale invariant porosity field on the basis of this model we generate synthetic neutron porosity logs and crosshole georadar tomographic surveys we then use the proposed geostatistical simulation approach to integrate this hydr

pedogenesis significantly decreases the stability of water dispersible soil colloids in a humid tropical region abstract the stability of soil colloids influences soil physicochemical properties soil development and transfer of nutrients and contaminants to surface and ground waters a better understanding of soil colloids stability dynamics during soil evolution is important for the evaluation of soil s capacity to retain nutrients and or accommodate toxic contaminants this study was aimed to determine changes in the stability of water dispersible soil colloids that accompany mineral transformation and surface charge evolution during pedogenesis using a well characterized chronosequence derived from basalt in the humid tropical region of hainan island south china the results demonstrated that the ph dependent colloid stability decreased significantly with tropical soil development which we attribute to the substantial changes in clay mineral compositions and colloid surface charge properties clay minerals in the studied chronosequence were characterized by an increase of kaolinite gibbsite and fe oxides and a decrease of quartz and halloysite towards more advanced stages of weathering which resulted in the decline of permanent negative charges in the older soils the point of zero charge phpzc increased while ph decreased across the tropical soil chronosequence being in good agreement with the observed lower colloid stability in aged soils dominated by kaolinitic minerals our study of colloid stability at long term pedogenic time scale suggests young tropical soils

hydrogeology of formation waters northeastern alberta basin the hydrogeological study of formation waters in the northeastern part of the alberta basin defined as the area from 55 to 58 n and from 110 to 114 w is based on information from 12 475 wells 3187 formation water analyses 2531 drill stem tests and 452 030 core plug analyses because the study area covering approximately 76 000 km2 is located at the feather edge of the basin local topography and physiographic features particularly the athabasca river system exert a strong influence on the flow of formation waters in most of the aquifers generally temperature seems to be the main controlling factor on salinity distributions the salinity of formation waters increases in the vicinity of evaporitic beds and decreases close to the surface beca se of mixing with fresh meteoric water introduced through local flow systems the lower and middle devonian pre prairie aquifer systems beneath the regionally extensive prairie aquiclude are characterized by regional topographically driven flow updip to the northeast this updip flow is opposed by buoyancy forces caused by salinity increase with temperature downdip to the southwest the post prairie devonian aquifers are characterized by transitional flow regimes because of erosion at the sub cretaceous unconformity and outcrop at the athabasca river local physiographic influences are superimposed on basin scale regional flow in these aquifers hydraulic communication between the beaverhill lake cooking lake and grosmont aquifers is inferred in places caused by cooking lake reefs penetrating the intervening shales of the lower ireton aquitard finally the retaceous aquifers all can be described as having local flow regime characteristics with no buoyancy effects as a result of recharge in topographically high areas and discharge in low regions along the valleys of the athabasca river system the flow of formation waters in northeastern alberta played an important role in the formation of the huge athabasca oil sands deposits hydrocarbons that migrated into the area from the west were trapped into local reservoirs and biodegraded and washed by fresh meteoric water introduced by local flow systems environmentally the subsurface hydrogeology in the area imposes specific constraints on waste disposal in deep formations mostly because of the absence of a thick continuous regional aquitard and because most aquifers subcrop at shallow depth or crop out and discharge along the valleys of the athabasca river system and at the basin edge

early syn rift evolution in the west cameros basin upper jurassic nw iberian range spain abstract alluvial systems are sensitive sedimentary systems that can preserve useful information about tectonics drainage area lithology and size and climate however research on this subject over the last three decades has made it evident that the interaction of these three factors and their control over the alluvial architecture and facies are complex the stratigraphic and sedimentological analysis of the earliest syn rift sedimentary record tithonian in the west cameros basin has confirmed that sedimentation during the beginning of extension in this area took place in a series of halfgraben basins in which three different types of fan shaped alluvial systems were deposited two relatively large systems specifically a highly channelized alluvial fan system and a distributive fluvial fan system changing downstream to an axial tributary fluvial system were the exception and small poorly channelized alluvial fan systems were the norm a semiarid climate is inferred during this earliest syn rift sedimentary record from the steady and extensive calcrete development this semiarid climate should play an important role both in how coarser sediment discharges to the rift halfgraben basins occurred and in the dominant transverse organization of the alluvial depositional systems however the climate and source area lithology can be considered steady factors so the main factors considered as the cause of these sedimentary and architectural heterogeneities are the tectonics and drainage area sizes and specifically the different behavior of each extensional structure in terms of the rate of tectonic uplift and subsidence this indicates how fault activity and drainage area sizes during the earliest stages of a rift system can generate high degrees of heterogeneity in the architecture of alluvial basins and how this heterogeneity is recorded by the alluvial systems in the form of differences in their facies association and architecture therefore this work concludes that both tectonics and catchment sizes exerted primary control on the sedimentary characteristics of associated alluvial systems in basins generated from this type of extensional setting and care must be taken when making climatic and tectonic interpretations using the sedimentary record of these alluvial systems because many changes that traditionally have been attributed to climate variability can be explained solely by the differential behavior of each extensional structure and or changes in its associated drainage area

reinterpretation of middle cambrian stratigraphy of the rifted western laurentian margin burgess shale formation and contiguous units sauk ii megasequence rocky mountains canada abstract until recently research on the renowned fossil animals of the burgess shale has advanced to a greater degree than an understanding of the rocks in which they are found studies addressing lithostratigraphy and hydrothermal petrography of the so called inner carbonate belt and adjacent chancellor group however have begun to re evaluate long standing hypotheses on the middle cambrian of western canada tectonic activity along the kicking horse rim buried remnants of neoproterozoic rifting during the cambrian period had more influence on local sedimentation than previously thought notably large scale collapse of the cathedral carbonate platform margin at 509 ma bp is evidence of reactivated basement faults these failures produced listric megatruncation surfaces having near vertical escarpments 150 m in height where they terminate against the platform the majority of what have been interpreted as shed olistoliths from the cathedral platform margin is herein shown instead to be carbonate mud mounds these grew in situ along the face of the cathedral escarpment and are associated with fossiliferous intervals in overlying basinal mudstones at three distinct stratigraphic horizons two within the burgess shale during the delamaran and marjuman stages the mounds nucleated where deep seated normal faults intersected the seafloor building primarily during periods of relative sea level transgression mound growth is associated with syndepositional exhalative activity inferred from stratigraphic relations sedimentology and geochemistry the new name monarch formation is proposed for the initial post collapse beds and mounds deposited against the cathedral escarpment early glossopleura zone the variably defined term takakkaw tongue is thereby confined to pre collapse slope deposits coeval to and correlative with the cathedral formation

a statistical test for significance of thinning and thickening upwards cycles in turbidites abstract in turbidite successions asymmetric cycles identified in vertical sections are often used as indicators of sedimentary processes in submarine fan models thickening and coarsening upwards cycles are thought to characterize depositional lobes whereas thinning and fining upwards cycles are believed to be produced by filling and abandonment of channels a non parametric statistical test based on the signs of differences between consecutive bed thickness values may be used to determine whether the cycles in a particular measured section are statistically significant the test can be modified to deal with bed thickness values that have been smoothed by moving averages and with multiple partial sections in an incompletely exposed unit

fluvial processes and cyclicity in terminal fan deposits an example from the late devonian of southwest ireland abstract the gun point formation is a sandstone dominated sequence approximately 1 5 2 5 km thick which forms part of a major 6 km late devonian alluvial basin fill succession in southwest ireland it is interpreted as the deposits of a southerly flowing terminal fan system which operated under a semi arid climate the proximal zone was characterized by low sinuosity gravelly feeder channels which passed downstream into a medial zone dominated by a sandy braidplain further south in the distal zone phases of high energy flood activity were centred on transient low sinuosity ephemeral channels and were separated by more quiescent periods of shallow sheetflooding subaerial exposure and non deposition sedimentary parameters such as set thickness coset thickness channel sand body density and maximum sand body thickness all exhibit regular cyclic fluctuations with a periodicity of 160 180 m the cycles are interpreted as evidence of regular discharge variations which may have been a response to the 412 ka orbital eccentricity cycle a second periodicity of approximately 700 m has also been detected and is thought to reflect long term variations in basin subsidence

effects of lime and gypsum on clay dispersion and infiltration in samples of a brazilian oxisol samples of the surface layer of an acid oxisol were treated with various amounts of caco3 lime or with caso4 gypsum and incubated in the laboratory to study possible effects on clay dispersion and infiltration the treatments consisted of incorporation of gypsum and lime or superficial application of lime infiltration rates were determined with a rainfall simulator and clay dispersion by measuring clay concentration in runoff effects of treatments with lime or gypsum were similar in some respects but different in others incorporating lime increased clay dispersion and reduced infiltration rates significantly incorporating gypsum in contrast increased clay dispersion and reduced infiltration slightly as compared with the control highly significant correlations were found between ph and both clay dispersion and infiltration rates as well as between clay dispersion and infiltration rates the relationship between increased clay dispersion and lower infiltration rates was linear application of lime to surfaces of soil samples reduced clay dispersion less than did incorporation covering the samples with wheat straw reduced clay dispersion and maintained high infiltration rates on the whole effects from additions of gypsum were more favorable than those of lime the more favorable results suggest further tests through field trials

millennial scale climatic fluctuation in the fluvial record during mis3 very high resolution seismic images from ne hungary abstract alluvial architectures of a meandering river existing in mis3 were observed on very high resolution vhr single channel waterborne seismic profiles 20 30 m below the tisza river in the pannonian basin hungary the study investigated the spatial and temporal variations of two more than 2 km long continuous series of inclined reflections interpreted as laterally accreted point bar complexes the phases of natural meander migration were reconstructed in 3d based on the changes in the geometry and dip of the inclined reflections a channel forming discharge curve extending over approximately 2 5 ky was calculated by using paleo width and depth data derived from the lateral accretion surfaces systematic analysis of the geometrical variations coupled with the discharge curve evaluation on each point bar complexes indicates millennial scale discharge fluctuations 40 50 ky ago to that the river responded principally by incision and infilling the primary periodicity comparable to the sub milankovitch cycles is superimposed by shorter periods ca 500 year cycles reflect the phases of unidirectional meander development while the smallest ones reflect the recurrence interval 150 200 years of the highest floods river bed incisions happened step by step related to extreme floods when the meander development also changed the smaller scale and more rapid fluctuations within a development unit were represented in variations of the channel width although the poor geochronology of the sandy fluvial deposits cannot allow any direct correlation to the climatostratigraphic events the millennial scale climate variations of mis3 were pronouncedly characteristic in the discharge fluctuations

milankovitch cyclicity recorded from devonian non marine sediments hydrographically closed basins are sensitive to environmental change at all scales the influence of climate being particularly strong some devonian basins contain non marine successions which appear to represent the deposits of such basins climatic fluctuations may be recorded by sediments in the form of milankovitch band cyclicity two novel records of climatically related cyclicity are discussed well 12 13 1 in the north sea penetrates a fine grained old red sandstone succession which is thought to be comparable to the largely lacustrine middle devonian deposits of the orcadian basin which outcrop onshore the gamma ray log through the devonian interval reveals periodic large peaks which correlate with u rich fine grained intervals deposited during periods of greatest lake expansion the peaks are cyclical power spectrum of the gamma ray data reveal periodicities of c 8 and 40 m which are thought to correlate with the 21 000 yr precession and 100 000 yr eccentricity milankovitch cycles the sherkin sandstone formation of the munster basin sw ireland is a thick 1000 m succession of largely alluvial deposits which were deposited by a terminal fan network detailed analysis of channel body sandstones and sedimentary structures contained within them reveals a cyclical variation in the dimensions of the bedforms camed by the channels the same cyclicity is evident in the proportion of channel deposits this variation reflects fluctuations in palaeodischarge probably related to climatic variation the main cycles are approximately 130 m thick spectral analysis reveals two further strong periodicities at approximately 36 and 55 m estimated sediment accumulation rates suggest that the cycles represent periods of the order of lo4 years it is proposed that the longer cycles reflect the 412 000 yr orbital eccentricity cycle and that the shorter cycles are either harmonics or components of the 100 000 yr eccentricity cycle

a paleopedological approach to the interpretation of terrestrial sedimentary rocks the mid tertiary fossil soils of badlands national park south dakota sedimentology is concerned with processes environments and products of sedimentation whereas paleopedology is concerned with soil formation on these materials between times of sedimentation both approaches can contribute much to an understanding of ancient terrestrial environments fossil soils can be recognized from irregular vertical tubular structures fossil root traces and burrows massive bioturbated layers with gradational contacts soil horizons complex cracking and veining peds and cutans and distinctive petrographic textures sepic plasmic fabrics in badlands national park south dakota numerous other features such as patterns of fossil bone accumulation horizons of calcareous nodules and layers and local variations in mineralogy and trace and major chemical elements were also evidence of fossil soils in the pinnacles area of badlands national park there are at least 87 successive fossil soils in 143 m of stratigraphic section ancient soil formation is a kind of early diagenesis which can be obscured by additional changes after burial of the soil late diagenesis in badlands national park those few late diagenetic features identified did not seriously alter traces of ancient soil formation fossil soils can be mapped and named in the field using the soil mapping procedures of the u s department of agriculture at least ten such nongenetic units fossil soil series can be recognized among fossil soils of the pinnacles area of badlands national park each represents a particular ancient environment in most cases these fossil soil types could be identified within modern soil classifications such as those of the u s department of agriculture and the australian c s i r o in addition fossil soils can be evidence of past soil forming factors such as climate organisms topographic relief parent material and time of formation climatic interpretations from fossil soils may be useful confirmation of other data although some immature or waterlogged soils reveal nothing of climate the kind of former vegetation such as woodland or grassland can be interpreted from fossil soils even where direct fossil evidence of its floristic composition is lacking fossil soils may be a guide to the degree nature and location of preservational biases of animal and plant fossils fossil soils can also be used to assess the degree of adaptation of associated fossil mammals because they are evidence of vegetation independent of other fossils from features of fossil soils related to waterlogging or drainage it may be possible to assess paleotopographic changes as well as some aspects of their tectonic control little altered parent material is usually preserved under fossil soils in some cases as in the region of the south dakota badlands during the oligocene parent material appears to have been complexly interrelated with vegetation climate and fluvial regimen times of formation of fossil soils can be estimated by comparison with studies of modern soil formation from such estimates which for the sequence in the pinnacles area of badlands national park appear to be crude but not unrealistic the completeness and rates of sediment accumulation of different parts of a sequence can be compared providing insights into changing factors in the long term behavior of fluvial systems

oscillations of global sea level elevation during the paleogene correspond to 1 2 myr amplitude modulation of orbital obliquity cycles abstract the mechanisms involved in the formation of 1 to 2 myr long third order stratigraphic sequences through the phanerozoic have been extensively debated but the main underlying forcings remain uncertain in this study we investigated third order sequences of paleocene eocene age in the east china sea shelf basin identifying a prominent 1 2 myr periodicity in the 405 kyr tuned gamma ray profile of the wp 1 borehole we infer that this 1 2 myr cycle which corresponds to long period amplitude modulation of obliquity was the main driver of third order sea level changes and sequence development this modulation entails variation in the range of obliquity amplitude between a maximum of 2 4 i e 24 5 22 1 and a minimum of 0 3 i e 23 3 23 0 as a result of interactions among the three primary parameters of earth s orbit i e eccentricity obliquity and precession we anchored our floating astronomical time scale ats to the t42 seismic horizon a major sequence boundary between the lin feng and mingyuefeng formations that corresponds to the top of nannofossil zone np8 reported age of 57 7 ma this yields a fixed ats for the late paleocene to middle eocene interval spanning 60 84 to 48 71 ma finally we evaluated our findings relative to the third order sequence stratigraphy of the east china sea shelf basin and to records of early cenozoic eustasy and global events

effects of clay type and rate of wetting on the mellowing of compacted soils abstract soil clays differing widely in mineralogy were individually mixed with sand and silt fractions from an alfisol the mixtures dominated by ca 2 were wet and dried ten times to simulate field conditions and promote microaggregation of the soils compacted cores were prepared at fixed water contents and tensile strengths of the cores were measured before and after a number of wetting and drying cycles wet at either fast or slow rates compacted soils which were dominated by randomly interstratified minerals rim exhibited higher tensile strengths before wetting and drying cycles tensile strengths of the compacted soils decreased with increasing number of wetting and drying cycles to different extents for fast and slow rates of wetting the results of the equilibrium tensile strength and the mellowing ratio of the compacted soils in relation to the properties of the clay fractions e g cation exchange capacity cec surface area and percentage of rim and shrink swell potential of the soils clearly showed that the higher the shrink swell potential the higher the aggregation and soil softening the degree of reversibility of soil compaction by development of microcracks caused by natural processes e g wetting and drying cycles increased as the percentage of shrink swell potential and rate of wetting increased

flow of formation waters in the cretaceous miocene succession of the llanos basin colombia this study presents the hydrogeological characteristics and flow of formation waters in the post paleozoic succession of the llanos basin a mainly siliciclastic foreland sub andean sedimentary basin located in colombia between the cordillera oriental and the guyana precambrian shield the porosity of the sandy formations is generally high in the range of 16 20 on average with a trend of de creasing values with depth permeabilities are also relatively high in the 102 and 103 md range the salinity total dissolved solids of formation waters is generally low in the 10 000 20 000 mg l range suggesting that at least some strata in the basin have been flushed by meteoric water the shaly units in the sedimentary succession are weak aquitards in t e eastern and southern parts of the basin but are strong in the central western part the pressure in the basin is close to or slightly subhydrostatic the underpressuring increases with depth particularly in the central western area the flow of formation waters in the upper units is driven mainly by topography from highs in the southwest to lows in the northeast local systems from the foothills and from local topographic highs in the east feed into this flow system the flow of formation waters in the lower units is driven by topography only in the southern eastern and northern parts of the basin in the central western part the flow is downdip toward the thrust fold belt driven probably by pore space rebound induced by erosional unloading which also is the cause of underpressu ing hydrocarbons generated in the cretaceous organic rich shaly gacheta formation probably have migrated updip and to the north northeast driven by buoyancy and entrained by the topography driven flow of formation waters however the downdip flow of formation waters in cretaceousoligocene strata in the central western part of the basin could have created conditions for hydrodynamic entrapment of hydrocarbons

the sedimentary environment of the late devonian east greenland tetrapods the late devonian early tetrapods in east greenland occur in the celsius bjerg group key occurrences are located in a detailed stratigraphic section used here to interpret the sedimentary palaeoenvironments the palaeoenvironment for the britta dal formation which contains both ichthyostega and acanthostega is reinterpreted the britta dal formation channels have flat bases are poorly channelized are of low sinuosity and are part of a very major distributory system that periodically experienced extreme flooding the tetrapod fossils were recovered from an ephemeral system that was not permanently habitable in the immediate area plant megafossils are poorly preserved casts and impressions dominated by lycopsids and fern like plants the overbank siltstones are dominated by arid soil forming processes and comprise a spectacular sequence of vertisols the 1174 m in situ ichthyostega locality in paralleldal was relocated and occurs just below the midpoint of the second megacycle in the britta dal formation

deficiencies of secondary fe oxy hydroxides associated with phyllosilicates and organic carbon limit the formation of water stable aggregates in fe ore tailings abstract the formation of water stable hierarchical aggregate structure is one of the critical processes in eco engineering iron fe ore tailings into soil like medium for sustainable rehabilitation of fe ore mine site through systematically comparing physical structure and mineralogical differences between fe ore tailings aggregates and fe rich native soil aggregates at a magnetite fe ore mine the present study captured the microstructure mineralogy and organic matter composition of aggregates in aged 4 years old tailings in comparison with those in native soils a suite of micro spectroscopic methods have been employed to elucidate their physical mineralogical and morphological characteristics including synchrotron based fe k edge x ray absorption fine structure spectroscopy xafs and backscattered electrons bse scanning electron microscopy energy dispersive x ray spectroscopy sem eds the results revealed significant differences in physical structure of aggregates in fe ore tailings and natural soils rich in fe which was attributed to their different mineralogical and organic components and characteristics especially it was found that the secondary fe oxy hydroxides i e goethite ferrihydrite and their interactions with al si rich secondary phyllosilicates or aluminosilicates were required in the formation of amorphous fe si al rich gels that acted as cementing agents for agglomerating si rich particles e g quartz in soil in contrast tailing aggregates rich in more crystalline primary minerals such as magnetite and biotite lacked these gels resulting in poor stability comparatively natural soil aggregates contained more recalcitrate organic carbon groups e g aromatic carboxyl and aliphatic c than tailing aggregates which would have also contributed to the improvement of aggregate stability through organo mineral associations this study has improved our understanding of key limiting geochemical factor s involved in the aggregation of fe rich soils which would provide the basis for formulating effective eco engineering inputs to accelerate the development of soil like structure in the fe ore tailings for sustainable rehabilitation

paleozoic paleogeography of north america gondwana and intervening displaced terranes comparisons of paleomagnetism with paleoclimatology and biogeographical patterns new paleomagnetic data have become available in the past 5 yr that require modifications in previously published paleogeographic reconstructions for the silurian and devonian in this paper the new paleopoles are compared to published paleogeographic models based on paleoclimatologic and biogeographic data the data from the three fields of paleomagnetism paleoclimatology and biogeography are generally in excellent agreement and an internally consistent paleogeographic evolutionary picture of the interactions between north america gondwana and intervening displaced terranes is emerging during the interval of the ordovician silurian and devonian north america stayed in equatorial paleoposition while rotating counter clockwise the northwest african part of gondwana was in high southerly latitudes during the late ordovician and was fringed by peri gondwanide terranes such as southern europe armorica and avalonian basement blocks now found in eastern newfoundland nova scotia the boston basin the appalachian piedmont and northern florida subsequently gondwana and the peri gondwanide terranes displayed rapid drift with respect to the pole this drift translates into the following pattern of movement for northwest africa during the latest ordovician early silurian this area moved rapidly northward from polar to subtropical latitudes followed by equally rapid southward motion from subtropical to intermediate about 50 s paleolatitudes during the late silurian middle devonian it is likely that significant east to west motion accompanied the latter shift in paleolatitudes with the caledonian acadian orogeny the result of silurian to early devonian convergence and collision between gondwana and north america this collision sandwiched several of the intervening displaced terranes between gondwana and north america subsequent to this collision gondwana was separated in the late devonian by a medium width ocean from north america and the avalonian and southern european blocks which were left behind adjacent to north america this new ocean closed during the carboniferous and the resulting convergence and collision were the cause of the hercynian alleghanian orogenic belt problems remaining for future research besides the further gathering of reliable paleopoles involve the uncertain pre devonian position of the southern british isles in this scenario and the very rapid velocity with respect to the pole that results from the rapid late ordovician silurian apparent polar wander for gondwana

african monsoons an immediate climate response to orbital insolation the croll milankovitch astronomical theory of climate1 3 has received strong support from the evidence of a linear climatic forcing by obliquity and precession although nonlinearity had to be assumed for eccentricity4 5 moreover interglacials have appeared to be controlled by the orbital insolation6 although a phase shift of 6 000 5 000 yr is seen between an astronomical climate index and terrestrial climate indicators dominated by the northern ice sheet dynamics climate proxy data of low latitudes are less directly dependent on the ice sheets here it is shown that during the past 464 000 yr african monsoons signalled by the east mediterranean sapropels were heaviest always and only when a northern summer monsoon index computed from the orbital variation of insolation reached maximum values this occurred during all the interglacials but also twice during glacial periods thus tropical aridity is not the single climatic pattern of glacial periods an immediate terrestrial climate response to orbital variations of insolation is established

uncertainties in the stratigraphic analysis of fluvial deposits from the loranca basin central spain abstract a detailed stratigraphic and sedimentological analysis is given of late oligocene to early miocene continental sediments in a small area 1 km2 of the loranca basin province of cuenca the studied exposure is a part of the tortola fluvial fan and mainly consists of superimposed meander belt sediments the ages of base and top of the sedimentary succession were obtained by a combination of biostratigraphic and palaeomagnetic data thus allowing us to estimate the mean sedimentation rates of the section 10 cm ka our estimation of the sediment accumulation rate based on the analysis of palaeosols 18 cm ka appears to be reasonably reliable for short term accumulation rates the small size of palaeochannels and the relatively wide basin section may have allowed the development of a distributary fluvial system and may have caused the low vertical recurrence of relatively episodic sedimentation the time interval covered by the sediments studied shows a progressive trend toward drier conditions and higher temperatures inferred from qualitative and quantitative changes in fossil rodent faunas these trends coincide with a gradual decrease of maximum values of estimated discharge of our fluvial systems in these sediments it is dangerous to establish a correlation between the detected possible climatic changes and milankovitch cycles this is due to the low sedimentation rate and the frequent discontinuities in our stratigraphic record

labyrinthine facies architecture of the tortola fluvial system and controls on deposition late oligocene early miocene loranca basin spain abstract upper oligocene to lower miocene deposits of the tortola fluvial system loranca basin central spain display a labyrinthine stratigraphic architecture comprising isolated sandstone bodies embedded in mudstone and siltstone these sandstone bodies are subdivided into seven types which are interpreted to have formed in rivers with different discharges sediment yields and channel planform patterns on the basis of their characteristics and spatial distributions four facies zones are defined these formed a continuum along the tortola fluvial system profile each being characterized by specific depositional conditions and consequently channel pattern styles gravel rich braided streams dominated zone 1 down gradient these streams graded into wide sand dominated braided streams of zone 2 which contain large bedforms and were typified by significant discharge variations zone 3 comprises belts of mixed load dominated meandering and low sinuosity channels zone 4 represents distal floodplain areas at the toe of the fluvial system depositional conditions in a facies zone varied between an upper and lower bound or geomorphic threshold a crossing of the upper or lower threshold is indicated by relatively sudden but orderly lateral and vertical changes in channel pattern that in turn reflect superposition of facies zones a facies cycle is formed by superposition of two successive downstream facies zones superposition of facies zones is inferred to have been caused by changes in sediment supply and hydraulic regime and consequently the regional gradient of the system it is argued that the tortola fluvial system developed under a weak tectonic regime during the later stages of basin filling and was possibly affected by climatic changes changes in size of the facies zones typified the long term development of the tortola fluvial system and determined the three dimensional architecture of the succession

astronomical forcing of meandering river behaviour milankovitch cycles in devonian of east greenland abstract a more than 1100 m thick succession dominated by single and multistorey sandstone bodies from the upper devonian kap graah group in east greenland is interpreted as a meandering river and associated overbank deposits the sandstone bodies display well developed lateral accretion bedding and are interpreted to be deposited as point bars in a well exposed section 215 m thick individual sandstone bodies have been analized quantitatively in order to compare the individual palaeochannel characteristics the results indicate cyclic variations in discharge channel slope and channel size the cycles are of the order of c 20 m thick with superimposed c 100 m mega cycles both are interpreted as reflecting cyclic variations in precipitation rate the cycles are interpreted as being governed by astronomical forcing of the climate reflecting milankovitch type precession cycles in the order of 20 000 years with modulation by c 110 000 years eccentricity mega cycles this study confirms that the precession and eccentricity cycles exhibit the main forcing on low latitude monsoonal climate

the sequence stratigraphy of fluvial depositional systems the role of floodplain sediment storage abstract the currently used model for alluvial sequence stratigraphy has been criticised miall 1991 and an alternative model is offered here in this model alluviation mainly takes place during transgressive and not highstand phases when accommodation space allows sediment storage the high capacity for some river systems to store floodplain sediments is a critical consideration the effects of climatic and intrinsic geomorphic changes during fluvial deposition are likely to greatly complicate simple base level controlled sequence models and recognising higher order fourth and fifth order cycles will be particularly difficult

lower to middle triassic sequence stratigraphy and climatology of the netherlands a model abstract the biostratigraphic framework for the triassic used by the nederlands aarddolie maatschappij in the netherlands has been reviewed and update this resulted in the recognition of 5 palynological zones and 8 subzones northwest european palynological assemblages have been interpreted in terms of xerophytic and hygrophytic flora elements characterising dry and humid climatic conditions the biostratigraphic zonation the climatic fluctuations both in the northwest european basin and on the northwestern margin of the tethys and the cyclic lithostratigraphical development have been integrated this leads to a climatological sequence stratigraphical model for the lower middle triassic of the netherlands during the late scythian smithian early spathian monsoonal activity was responsible for the activation of an ephemeral drainage system on the northern side of the central european highland under the influence of sealevel highstands the position of the monsoon belt shifted northwards and the northward flowing drainage system was most active leading to mass transport of erosional products from the highlands into the germanic basin based on a combination of biostratigraphic data and climatic events the lower triassic sedimentary cycles in the netherlands can be linked indirectly with the standard sequence stratigraphy and to milankovitch orbitally forced cyclicity for the marine middle triassic sediments a more direct link is envisaged

determination of anisotropy of spatial correlation structure in a three dimensional permeability field accompanied by shallow faults 1 structural planes such as fractures bedding planes schistosity and so on induce heterogeneity of permeability field in geologic bodies one of the ways to demonstrate the heterogeneity is to geostatistically infer the spatial correlation structure this paper presents a newly developed geostatistical technique for estimating the three dimensional heterogeneous permeability field in the presented method the plane directional anisotropy of spatial correlation structure of the three dimensional permeability field is determined by estimating semivariograms in multiplane directions using limited in situ measurement data of basement rock permeability a case study of a dam site shows that the spatial correlation of permeability in the direction parallel to the fault planes is greater than that perpendicular to it direction of the largest anisotropy of the spatial correlation of the permeability field is concordant with the strike of the major faults

iron oxides and particle aggregation in b horizons of some italian soils the relative importance of iron oxides to the aggregation status of soil has been evaluated for thirteen samples collected from b horizons of inceptisols and alfisols the particle size distributions before and after selective dissolution treatments were performed to assess the capacity of various iron oxides to aggregate soil particles iron extractable with nh4 oxalate was more effective in aggregation than goethite and hematite the capacity of iron oxides to aggregate clay sized particles was not significantly different in samples containing goethite and hematite from those having goethite only goethite and hematite in clay and in sand fractions had similar al substitution and mean crystallite dimensions but different reductive dissolution rates in dithionite

monsoon climate of the early holocene climate experiment with the earth s orbital parameters for 9000 years ago values for the precession and obliquity of the earth 9000 years ago indicate that the global average solar radiation for july 9000 years ago was 7 percent greater than at present when the estimated solar radiation values are used in a low resulation climate model the model simulates an intensified continent scale monsoon circulation this result agrees with paleoclimatic evidence from africa arabia and india that monsoon rains were stronger between 10 000 and 5000 years ago than they are today

cretaceous rhythmic bedding sequences a plausible link between orbital variations and climate abstract simple oscillation cycles have been recognized in cretaceous pelagic sequences as a marked periodicity in carbonate and or organic carbon content the estimated periodicities of these cycles resemble milankovitch type variations in orbital elements however during warm geologic periods the nature of the link between orbital variations and the sedimentary record has been problematic climate model studies show that the intensity of continental margin precipitation in specific low latitude regions is a function of land sea thermal contrast which is sensitive to orbital variations cretaceous climate model simulations are characterized by regions of intense precipitation the locations of which are controlled by geographic configuration in particular in the model simulation the northern margin of the tethys ocean has all the climatic characteristics necessary to exhibit a sensitivity to orbital variations detailed studies of the biota sedimentology and geochemistry of the bedding rhythms in greenhorn cyclothem in the western interior seaway of north america are best interpreted in terms of variations in precipitation runoff and stable stratification of the seaway combined the geologic and model studies support a link between orbital periodicities variations of intense precipitation associated with specific paleogeographic situations and cretaceous bedding patterns this hypothesis has important implications for the sensitivity of the atmosphere hydrosphere lithosphere system to external forcing

pangaean climates megamonsoons of the megacontinent the climate for a highly idealized geographic representation of the megacontinent of pangaea corresponding to the period 250 200 m y ago is explored using a low resolution atmospheric general circulation model that is coupled to a static mixed layer ocean of constant depth with a provision for sea ice formation and decay soil moisture is included as a predicted variable on the continent because there are large uncertainties about key factors that might influence the pangaean climate sensitivity experiments are used to examine the climate for two different mean elevations 0 and 1000 m two different snowcover prescriptions and two different levels of implied greenhouse heating and solar luminosity modern co2 concentration and modern solar luminosity fivefold increase in modern co2 concentration and a 1 decrease in modern solar luminosity in all of the experiments the large bipolar land masses of laurasia and gondwanaland joined near the equator in the west and separated by the tethys sea in the east exhibit extreme continentality with hot summers cold winters and large scale summer and winter monsoon circulations year round or seasonal aridity is simulated for all but the eastern coastal regions the tropical western coast and the regions poleward of 40 latitude the simulated climate of the idealized pangaean continent has many features that correspond qualitatively with geologic evidence for tropical warmth and aridity in the late permian and triassic however the model results serve mainly to indicate the importance of various climate forming factors geography topography heating detailed comparisons will require new experiments with better models and more accurate geologic boundary conditions

geostatistical analysis of an experimental stratigraphy 1 a high resolution stratigraphic image of a flume generated deposit was scaled up to sedimentary basin dimensions where a natural log hydraulic conductivity ln k was assigned to each pixel on the basis of gray scale and conductivity end members the synthetic ln k map has mean variance and frequency distributions that are comparable to a natural alluvial fan deposit a geostatistical analysis was conducted on selected regions of this map containing fluvial fluvial floodplain shoreline turbidite and deepwater sedimentary facies experimental ln k variograms were computed along the major and minor statistical axes and horizontal and vertical coordinate axes exponential and power law variogram models were fit to obtain an integral scale and hausdorff measure respectively we conclude that the shape of the experimental variogram depends on the problem size in relation to the size of the local scale heterogeneity at a given problem scale multilevel correlation structure is a result of constructing variogram with data pairs of mixed facies types in multiscale sedimentary systems stationary correlation structure may occur at separate scales each corresponding to a particular hierarchy the integral scale fitted thus becomes dependent on the problem size the hausdorff measure obtained has a range comparable to natural geological deposits it increases from nonstratified to stratified deposits with an approximate cutoff of 0 15 it also increases as the number of facies incorporated in a problem increases this implies that fractal characteristic of sedimentary rocks is both depositional process dependent and problem scale dependent

modeling hydraulic conductivity of a complex confining layer at various spatial scales the spatial variation of the hydraulic conductivity of a complex confining layer in the netherlands is modeled at four different scales the scale of sediment cores 10 1 100 m the scale of the numerical model blocks 101 102 m the local scale 102 103 m and the regional scale 103 105 m two stochastic methods are combined 1 conditional multiple indicator simulation of texture classes to obtain three dimensional images of the lithology of the confining layer from borehole descriptions and 2 the statistical upscaling procedure of indelman and dagan 1993a b to derive the first and second order statistics of hydraulic conductivities at the scale of the numerical model blocks when the upscaling of the core scale conductivities is ignored the local and regional scale groundwater flow through the confining layer is predicted wrongly

moving through scales of flow and transport in soil flow and transport in soil is governed by the binary geometry of solid and void this may be described at typical length scales of some millimeters and even less in contrast the problems which are supposed to be solved in soil physics are related to a scale of some meters the typical distance between soil surface and groundwater a quantitative understanding of flow and transport based on measurements of hydraulic properties and transport parameter at a given scale requires the transfer of information in space time and across scales this is the major challenge in heterogeneous soils and this has motivated many concepts for the organization of heterogeneities including macroscopic homogeneity discrete hierarchy and fractal geometry we propose a conceptual approach termed the scaleway to predict flow and transport in structured materials whatever the scale and whatever the specific type of structural organization this is based on the explicit consideration of structure that is assumed to be present at the scale of interest while the microscopic heterogeneities are replaced by averaged effective descriptions the three ingredients needed are a representation of the structure a process model at the scale of interest and corresponding effective material properties we demonstrate the scaleway for one example of solute transport in a soil column and discuss implications for future research

evolution of miocene fluvial systems in the himalayan foredeep through a two kilometer thick succession in northern pakistan abstract sedimentological variations through a kilometer thick coarsening upward succession in the miocene himalayan foredeep basin fluvial chinji and nagri formations of the siwalik group are documented in the chinji village area on the potwar plateau of northern pakistan from the chinji formation upwards into the nagri formation 1 the proportion of major sandstone bodies increase relative to mudstone dominated beds 2 average thickness and mean grainsize of channel deposits increase 3 sediment aggradation rates increase 4 there is a reported change in sediment providence 5 paleocurrents are generally to the southeast and vary little upsection and 6 paleosols are more distinct lower in the section where there is also more evidence of ponding of water on the floodplain smaller scale 100 m thick cyclic variations in the proportion of major channel sandstone bodies also occur in both formations in the modern himalayan basin sediment dispersal away from the mountain belt is associated with 1 major rivers that flow along the basin axis 2 large rivers that drain substantial areas of the mountain belt and deposit low relief sediment fans extending hundreds of kilometers into the basin and 3 smaller rivers in fan and interfan areas that drain local areas and carry finer sediment loads sediment variations through the chinji nagri formation boundary can be related to a shifting of depositional environments within such fan and interfan areas major basin axial rivers are not exposed in this area it appears that kilometer thick upsection variations in these deposits record the progradation of the sediment fan formed by a large river system river discharge on the order of 104 m3 s over the floodplain of a smaller river system river discharge on the order of 103 m3 s large scale vertical sediment variations over hundreds of meters to kilometers appear to reflect changes in the basin subsidence and the rate of sediment input to the basin over time scales on the order of 105 106 years upsection variations can not easily be related to climatic change or eustatic variations in sea level the most likely explanation for upsection changes is tectonism deposition rates and shifting positions of river systems within the basin responded more quickly to changes in basin subsidence rate whereas increases in the proportion of sandstone bodies and increases in floodplain slopes lagged behind deposit variations in the siwalik group clearly record variations between different scale river systems delivering sediment to the basin as well as the overall basin evolution

fluvial responses to climate and sea level change a review and look forward summary fluvial landforms and deposits provide one of the most readily studied quaternary continental records and alluvial strata represent an important component in most ancient continental interior and continental margin successions moreover studies of the long term dynamics of fluvial systems and their responses to external or allogenic controls can play important roles in research concerning both global change and sequence stratigraphy as well as in studies of the dynamic interactions between tectonic activity and surface processes these themes were energized in the final decades of the twentieth century and may become increasingly important in the first decades of this millennium this review paper provides a historical perspective on the development of ideas in the fields of geomorphology quaternary geology vs sedimentary geology and then summarizes key processes that operate to produce alluvial stratigraphic records over time scales of 103 106 years of particular interest are changes in discharge regimes sediment supply and sediment storage en route from source terrains to sedimentary basins as well as changes in sea level and the concept of accommodation late quaternary stratigraphic records from the loire france mississippi usa colorado texas usa and rhine meuse the netherlands rivers are used to illustrate the influences of climate change on continental interior rivers as well as the influence of interacting climate and sea level change on continental margin systems the paper concludes with a look forward to a bright future for studies of fluvial response to climate and sea level change at present empirical field based research on fluvial response to climate and sea level change lags behind a the global change community s understanding of the magnitude and frequency of climate and sea level change b the sequence stratigraphic community s desire to interpret climate and especially sea level change as forcing mechanisms and c the modelling community s ability to generate numerical and physical models of surface processes and their stratigraphic results a major challenge for the future is to catch up which will require the development of more detailed and sophisticated quaternary stratigraphic sedimentological and geochronological frameworks in a variety of continental interior and continental margin settings there is a particular need for studies that seek to document fluvial responses to allogenic forcing over both shorter 102 103 years and longer 104 106 years time scales than has commonly been the case to date as well as in larger river systems from source to sink studies of quaternary systems in depositional basin settings are especially critical because they can provide realistic analogues for interpretation of the pre quaternary rock record

use of humic substances as soil conditioners to increase aggregate stability abstract in many agricultural soils in the semi arid and and mediterranean climates exposure to cyclic wetting and drying wd can reduce aggregate stability the extent to which soil pretreatment with coal derived humic substances hs can increase aggregate stability in soils exposed to cyclic wetting and drying wd was evaluated in this study the soils studied are an acireale silty clay loam from sicily a principina silt loam from tuscany and a bovolone loam from venetia in italy on each soil eight rates of the hs 0 0 001 0 01 0 05 0 10 0 50 1 00 and 10 00 g kg of soil and four wd cycles 0 3 6 and 9 were used to assess any changes in stability on the principina and bovolone soils dominated by illitic and smectic clay minerals successive wd cycles reduced aggregate stability on the acireale soil dominated by kaolinitic clay mineral after initial decrease in stability following three wd cycles the aggregates regained stability as cyclic wd continued amending the soils with low rates of hs equivalent to 100 200 kg ha not only improved aggregate stability significantly p 0 05 on all the three soils but also reduced substantially the disaggregating effects of wd cycles this work indicates that exogenous humic substances have a potential as soil conditioners in conservation practices aimed at increasing the structural stability of soils

geostatistics based regional characterization of groundwater chemistry in a sedimentary rock area with faulted setting sophisticated modeling of a hydrogeological structure and the environment are crucial for underground construction this study characterizes hydrochemical properties of groundwater in a sedimentary rock area clarifying their spatial distribution and correlation with geologic structure and interpreting the groundwater source and chemical evolution water samples geological columns and well logs to 1 km depth were taken at 10 sites in horonobe of northern japan toward the objectives a 3d model of cl concentration was produced in conjunction with resistivity logging data through kriging estimation and sequential gaussian cosimulation variography shows that the dip of the main omagari fault is a control on the spatial correlation structure of cl concentration the 3d model shows that this fault and its auxiliary constitute a clear boundary between high and low saline waters and that cl concentrations tend to change in accord with sedimentary layer structures the integration of stable isotope analysis suggests that deep saline water with heavy d and 18o originated from fossilized seawater whereas shallow freshwater with light values is of meteoric water origin dilute saline water in the deep part of study area is partially attributable to dehydration of silica minerals vertical and lateral groundwater flows are estimated to prevail near the omagari fault and be general in other zones respectively difference in the depth of transition zones may be caused by the dominant flow among downward ascending and lateral consequently geostatistical techniques and data integration are useful to depict regional groundwater systems with a data set of water investigation limited by quantity and location

a sedimentological model for the continental upper triassic tadrart ouadou sandstone member recording an interplay of climate and tectonics argana valley south west morocco the continental upper triassic tadrart ouadou sandstone member was deposited in an extensional setting on the pangaean continent strongly influenced by a low latitude climatic regime 10 to 20 north complex interaction of basin subsidence and climatically driven processes led to high facies variability and a lack of correlatable units across the argana valley exposures a process orientated approach integrating detailed facies with architectural element analysis was undertaken which resulted in a multistage depositional model for the tadrart ouadou sandstone member the basin scale model shows that basal alluvial fan and braided river systems are confined to the centre of the argana valley exposures aeolian deposits occur throughout the sequence but dominate in the north after a phase of playa deposition prominent basin wide fluvial incision of up to 8 m marks the onset of perennial fluvial flow these well sorted internally complex and locally highly amalgamated fluvial sandstones are widespread throughout the basin and are focused in a north to south south west flowing channel system after a final stage of aeolian sedimentation sandstone deposition of the tadrart ouadou sandstone member in the argana valley is terminated rapidly by the onlap of lacustrine mudstones of the sidi mansour member the study revealed that except for one pronounced period of perennial conditions sedimentation is controlled largely by ephemeral fluvial flow alternating ground water tables deflation processes and periods with limited periodic local run off the study highlights that facies architecture in the basin is the result of complex interaction of local syn sedimentary tectonics and the climatic regime within the basin but also the climate of the catchment area to the east the data suggest a proximal to mid distal basin setting in the rain shadow to the west of a mountain range massif ancien which exerted a strong control on the depositional environments of triassic deposits exposed in this part of south west morocco

mediterranean quaternary sapropels an immediate response of the african monsoon to variation of insolation abstract in the subsurface of the east mediterranean sea eleven discrete basin wide organic rich black sapropels were deposited during the last 465 000 years they are dated by oxygen isotopic chronostratigraphy the most recent sapropel has been shown to be the consequence of heavy nile river summer floods due to increased monsoonal summer precipitation over ethiopia and not of scandinavian ice sheet meltwater influx into the east mediterranean sea as was previously believed while most sapropels were deposited during interglacials two thick sapropels formed during glacial periods as shown by their position in the oxygen isotopic stratigraphy and by their pollen record in core rc9 181 the new evidence presented here is that the sapropel sequence in this core including the two glacial sapropels correlates on a one to one basis with the highest values of an index of insolation on top of the atmosphere the concept of this index derives from an analysis of the african monsoon process the index variation is computed for the last 465 000 years from the caloric northern summer insolation in the tropical latitudes controlled by variations of the earth s orbital parameters it is conjectured that this index might be linked through the climate system to the monsoonal precipitation which in africa produces the nile river summer flood

integration of diverse physical property models subsurface zonation and petrophysical parameter estimation based on fuzzy c means cluster analyses inversions of an individual geophysical data set can be highly nonunique and it is generally difficult to determine petrophysical parameters from geophysical data we show that both issues can be addressed by adopting a statistical multiparameter approach that requires the acquisition processing and separate inversion of two or more types of geophysical data to combine information contained in the physical property models that result from inverting the individual data sets and to estimate the spatial distribution of petrophysical parameters in regions where they are known at only a few locations we demonstrate the potential of the fuzzy c means fcm clustering technique after testing this new approach on synthetic data we apply it to limited crosshole georadar crosshole seismic gamma log and slug test data acquired within a shallow alluvial aquifer the derived multiparameter model effectively outlines the major sedimentary units observed in numerous boreholes and provides plausible estimates

milankovitch scale multi proxy records from fluvial sediments of the last 2 6 ma pannonian basin hungary abstract the continuous cores of two nearly 500 m deep boreholes cutting pleistocene fluvial sequences in the eastern part of the pannonian basin hungary have been studied magnetostratigraphy indicates that the sediment sequences span the last 2 6 ma without significant hiatuses comparison of systematic variations in magnetic susceptibility with changes in grain size distribution revealed milankovitch scale cyclicity in sedimentation of 40 and 100 kyr cyclicity which also shows a correspondence with the 18o variations of the odp 677 site comparison of pollen and gastropod paleoecological data with the magnetic susceptibility proxies suggests that climate was a major allogenic control on the cyclicity zones of high magnetic susceptibility correspond closely with sandy and coarse silty parts of the borehole successions which largely coincide with pollen and molluscs indicating a warm climate on the contrary zones with low magnetic susceptibility correspond to silts and clays and in most cases coincide with cold climate indicator pollen and molluscs heavy mineral and xrd studies revealed that magnetic susceptibility reflects the absolute amount of detrital fe oxide minerals mostly magnetite variations in the amount of magnetite are related to changes in heavy mineral content which arise primarily from changes in sediment supply to the basin by rivers the depositional model for the pleistocene fluvial sediments suggests that sediment flux increased towards the basin during interglacials due to the increased discharge and transport capacity of the rivers while a decreased sediment supply to the distal parts of the basin occurred during glacials a delay between erosion and storage of weathering products near to the source area and subsequent transportation and re deposition of sediments in the basin interior setting is an important cause of this effect

colloidal stability in some tropical soils of southeastern nigeria as affected by iron and aluminium oxides abstract the stability of microaggregates in soils as opposed to its dispersion is a very important soil phenomenon that checks degradation arising from unguided tillage and soil erosion ten soils from southeastern nigeria were sampled from their typical a and b horizons for the study the aim was to identify the extent of colloidal stability of the soils and the forms of fe and al oxides in the soils contributing to their stability the soils are mostly ultisols and inceptisols formed on sandstones and shale parent materials the soils are low in soil basic cations including the soil organic carbon soc the major clay mineral is kaolinite while the soil is acid in reaction the various forms of soil fe and al oxides are high with the total forms of fe and al being most dominant and dithionite extracted fe and al oxalate extracted fe and al pyrophosphate extracted fe and al the water dispersible clay and silt wdc and wdsi which are index of dispersion in most soils are low to medium thus reflecting in the low to medium dispersion ratio dr the clay flocculation index cfi and aggregated silt clay asc were moderate to high implying the high potential stability of the soils soil organic carbon did not seem to be contributing much to the stability of the microaggregates while oxalate and pyrophosphate extractable fe feox fep and to some extent total al alt were among the different forms of oxides that act as aggregating agents we propose here that rather than soc acting as a disaggregating agent in the soils it might have acted in association with these oxides in a linkage or bridge such as c p om c to ensure stability of the soils

reconstruction of a pleistocene meandering river in east hungary by vhr seismic images and its climatic implications abstract the upper 20 30 m of the pleistocene alluvial sequence on the tisza river hungary is investigated by 200 km of vhr single channel seismic sections frequent internal configurations such as 1 bundles of inclined reflections 2 trough shaped converging and 3 horizontal parallel reflections are interpreted respectively as lateral accretion of point bars abandoned channel fills and floodplain deposits the series of 5 8 m thick inclined strata sets occurring at the same depth throughout the area suggest the presence of a meandering river dated to about 43 47 ka in the late pleistocene according to osl data newly recorded quasi 3d seismic profiles reveal that each 1 3 km long inclined series correlates with an individual point bar continuously migrating in the same direction small deviations in the direction of migration are caused by natural wandering of the meander bend morphometric parameters of point bars are used to calculate ancient channel parameters width and depth of 200 500 m and 5 8 m respectively values imply a channel forming discharge of q 400 900 m 3 s these results imply a greater amount of runoff and supply in the basin during mis3 compared to the present day long lasting meandering indicates the role of local factors and a different fluvial environment compared to the commonly anastomosing systems in nw europe our data support the thesis of the three axis drainage system for the basin new evidence is provided for the antecedent existence of a temporally active third trunk river in addition to the ancestors of danube and tisza rivers contrary to the present day two axis drainage pattern