bedload transported pedogenic mud aggregates in the lower old red sandstone in southwest wales siltstones which exhibit large scale cross stratification and three dimensional bedforms in the ridgeway conglomerate formation are interpreted as partly representing bedload transported pedogenic mud aggregates the siltstones contain mixed layer swelling clays abundant desiccation cracks calcrete nodules and pseudoanticlinal slip planes which suggest the presence of vertic palaeosols and a hot seasonal climate compaction obliterated much of the original mud aggregate texture which is retained only where quartz grains surround individual aggregates

stratigraphy and facies architecture of the fluvial aeolian lacustrine sergi formation upper jurassic reconcavo basin brazil abstract the sergi formation encompasses an upper jurassic fluvial eolian lacustrine succession deposited within a wide intracratonic basin its sand bodies represent the largest and more important reservoirs in the reconcavo basin hosting 362 million m 3 of oil in place the main goal of this paper is to provide a detailed stratigraphic analysis of the sergi formation based on core and outcrop data it was achieved through the recognition and correlation of regional surfaces that have allowed the subdivision of this unit into distinct depositional sequences and the reconstruction of its depositional history the studied succession can be subdivided into three unconformity bounded sequences sequence i is composed of lacustrine mudstone at its base which is overlain by fine to medium grained sandstone related to aeolian dune and sand sheet and ephemeral fluvial stream deposits fluvial strata indicate northeastward flowing streams whereas aeolian dune deposits suggest the action of southwestward blowing winds the regional unconformity bounding sequences i and ii denotes both a climate change and tectonic rearrangement of the basin this surface delineates a change in the depositional style from fluvial aeolian lacustrine sequence i to entirely fluvial sequence ii the latter includes coarse grained to conglomeratic sandstone deposited within northwestward flowing braided channel belts changes in fluvial palaeocurrent from sequence i to ii indicate rearrangement of the drainage system related to basin tectonism furthermore a change in the fluvial discharge regime took place as a result of a change from a drier to a wetter climate fluvial deposition in sequence i was related to ephemeral streams whereas fluvial facies architecture of the sequence ii deposits indicates perennial braided streams with significant discharge variation another regional unconformity this time related to a stratigraphic base level fall and consequent widespread basinwide aeolian deflation separates the braided fluvial facies of sequence ii from the fine to medium grained sandstones ascribed to sheet floods aeolian dunes and aeolian sand sheets of sequence iii the resumption of aeolian sedimentation indicates a return to drier conditions in the basin the abrupt change from fluvial aeolian deposits to the lacustrine deposits of the overlying itaparica formation suggest a rapid rise of the water table and consequent basinwide flooding

upper flow regime mud floodplains lower flow regime sand channels sediment transport and deposition in a drylands mud aggregate river abstract dryland rivers in which fine sediments travel as aggregates are increasingly recognized in modern and ancient fluvial systems fowlers creek australia is an ephemeral dryland mud aggregate river whose sediments provide insights into the dynamics of mud aggregate floodplains the origin of massive mudrocks from arid depositional environments and the nature of planar bedding fowlers creek s flow conditions were inferred from relationships between landforms and the sediment texture bedforms and sedimentary structures remaming after flow ceases floodplain muds consisting of fine sand and sand size mud aggregates are distributed over the floodplain in suspension as flow decelerates they are deposited as bedload the shallow depth high sediment load and low aggregate particle density promote flow conditions ranging from high in the lower flow regime to upper flow regime producing coexisting ripples scours flat beds and clay layers with time visible signs of aggregate structure are lost leaving a massive cohesive mud consolidation is not achieved by burial aggregates reappear when muds reenter fluvial transport in unchanneled reaches sheetflows deposit sediment with a pervasive horizontal fabric channel sediments coarse sands and gravels are a minor component of fowlers creek s deposits widespread lower flow regime conditions produce planar beds and 2 d dunes usually deposited without internal stratification or in horizontal laminae lower flow regime planar bedding is also observed in fine silty sands near the close of flow rapid shallowing may move channel conditions from lower to upper flow regime or from lower to higher positions in the lower flow regime bedform stability spectrum leading to unusual bedform associations in the rock record sediments from a river like fowlers creek would be characterized by structureless gravelly sands channel facies massive red mudstones floodplain facies and sediments with horizontal fabric but poorly expressed bedding sheetflow facies

early mississippian sandy siltstones preserve rare vertebrate fossils in seasonal flooding episodes this study is a contribution to the tw eed project tetrapod world early evolution and diversification a major research programme investigating the rebuilding of carboniferous ecosystems following a mass extinction at the end of the devonian smithson et al 2012 this study was funded by nerc consortium grant the mid palaeozoic biotic crisis setting the trajectory of tetrapod evolution led by professor jenny clack university museum of zoology cambridge and involving the universities of cambridge ne j022713 1 leicester ne j020729 1 southampton ne j021091 1 the british geological survey ne j021067 1 and the national museum of scotland

sediment recycling on siluro devonian floodplains some of the red mudstones in the red mark old red sandstone of llansteffan dyfed are interpreted as originating as sand sized mud aggregates pellets produced in soils and deposited from bed load in small sinuous channels by analogy with the channel country of australia such channels may represent periods of low discharge and reduced hydraulic efficiency when the floodplains were locally reworked in contrast larger channel fills with extraneous sediments may represent pluvial periods with increased discharge

structural controls on palaeozoic basin evolution and inversion in southwest wales the tectonic evolution of sw dyfed is presented in terms of a model of basin evolution and subsequent destruction by reactivation of the basin bounding faults in contractional mode movements along long lived palaeozoic extensional faults were reversed during variscan compression with the pre existing faults accommodating the contraction in addition to the development of a thin skinned thrust and fold system basin analysis of the pre variscan extensional system uses sedimentological and stratigraphical evidence to constrain the timing of movements of the basin bounding faults thus allowing division of the stratigraphy into depositional megasequences related to these extensional movements field examples on all scales illustrate active extension during the palaeozoic structural cross sections through sw dyfed demonstrate the interrelationship of the extensional and contractional deformations with palinspastic restorations of the cross sections illustrating the complexity of the pre variscan template

landscape and depositional controls on palaeosols of a distributive fluvial system upper cretaceous brazil abstract the stratigraphic record of distributive fluvial systems is commonly characterised by frequent and complex interstratification of palaeosols among channel and overbank deposits however current models focus primarily on sedimentation and pay only limited attention to palaeopedogenesis thereby failing to incorporate important palaeoenvironmental and stratigraphic information this study proposes a pedosedimentary model for distributive fluvial systems that depicts and accounts for two palaeopedogenetic trends one downdip in relation to distality from the fan apex and one along strike in relation to distance from active channel belts palaeosols are reported in detail from an upper cretaceous succession of the bauru basin southeastern brazil through the application of macro micromorphological and geochemical studies combined with facies and architectural element analyses of sediments in the downdip palaeopedogenetic trend the proximal zone of the depositional system is characterised by a dominance of well drained inceptisols that develop on amalgamated channel fills in the medial zone inceptisols occur interlayered with overbank deposits containing entisols and poorly drained vertisols the distal zone preserves more mature and poorly drained inceptisols developed on deposits of overbank and sporadic distal channel fills these pedotypes show an increase in maturity and hydromorphism moving away from the apex to the fan toe this is likely linked to i the progressive approach of the topographic surface to the water table and ii the average increase in distance to an active channel belt in distal locations the along strike palaeopedogenetic trend culminates in poorly developed palaeosols in floodplain regions that correspond to topographic depressions located between channel belts and which were subject to recurrent floods because palaeopedogenesis in the floodplain region is penecontemporaneous to sedimentation pedotypes show an increase in maturity bioinduced calcification and hydromorphism with distance from the active channels they pass laterally from entisols and inceptisols near active channels to vertisols away from active channels conversely following avulsion abandoned channel belts remain as topographically elevated alluvial ridges located at some distance from the newly active channels and positioned above the water table and this leads to the development of better drained and better developed inceptisols relative to pedotypes of the floodplain region overall both palaeopedogenetic trends demonstrate the overriding controls of topography sedimentation rate and parent material on pedogenesis with only minor climatic influence this work offers a novel pedosedimentary model for distributive fluvial systems and highlights the palaeoenvironmental significance of palaeosol trends providing new constraints for the recognition of distributive fluvial systems in the rock record

late silurian and early devonian terrestrialisation ichnological insights from the lower old red sandstone of the anglo welsh basin u k abstract late silurian to early devonian deposits from the lower old red sandstone anglo welsh basin preserve a diverse assemblage of trace fossils that collectively comprise an important record of early terrestrialisation five main palaeoenvironmental categories are represented 1 perennial rivers 2 ephemeral rivers 3 floodplain lakes 4 alluvial fan and 5 marginal marine ichnocoenoses mainly reflect the activity of aquatic and or semi aquatic animals fluvial deposits preserve evidence for colonisation by eurypterids fish and myriapods ephemeral river channel margins splays preserve the most diverse ichnofauna composed of deposit feeders burrows and trackways produced by arthropods feeding and foraging in channel margin soft grounds that were colonised after fluvial flood events high densities of deposit feeding structures may indicate of explosive population growth in response to periodic acyclical replenishment of nutrients in these aquatic settings ichnotaxa common to both perennial and ephemeral fluvial environments suggest that there might have been only one aquatic ecosystem the degree to which the channel margin ichnofaunas record a truly subaerial terrestrial arthropod signature is difficult to ascertain and most trace makers were probably semi aquatic some terrestrial animals invaded channel margin areas to feed and were also capable of inhabiting high energy alluvial fan environments however the fans contain low diversity ichnological assemblages and were likely to have been inhabited by an opportunistic fauna possibly the only truly subaerial terrestrial ichnocoenosis is that of pedogenically modified mudrock with scoyenia which represents an early soil ichnofauna the majority of ichnocoenoses described from continental palaeoenvironments could be classified under the scoyenia ichnofacies marginal marine deposits contain an impoverished skolithos cruziana ichnofacies typical of silurian devonian brackish water assemblages

alluvial facies evolution during the palaeozoic greening of the continents case studies conceptual models and modern analogues the palaeozoic greening of the continents the appearance and expansion of embryophytes land plants in terrestrial environments was arguably the most fundamental phanerozoic change to the earth system thirteen case studies of cambrian to devonian fluvial deposits from north america and europe are documented here to illustrate the evolution of fluvial style during this period during the cambro ordovician prior to the advent of terrestrial vegetation fluvial systems laid down relatively coarse sands with little mud resulting in self formed channels and an architecture dominated by broad sheets of trough cross beds sheet braided style similar deposits formed across a wide range of latitudes and passed basinward into sandy coastal deposits from the mid ordovician onwards an increase in floodplain mudstone corresponds broadly with the appearance of embryophytes which would have progressively enhanced upland weathering mud production and floodplain storage of fines during the late silurian small heterolithic channel bodies with lateral accretion sets provide the first evidence of meandering channels and floodplain mudstones contain more varied palaeosols especially calcretes which appear abundantly for the first time by the early devonian channel deposits comprise sandstone lenses channelled braided style probably due to the increased bank strength and cohesion and reduced potential for sediment sorting imparted by sand mud mixtures muddy coastal deposits are prominent by the upper devonian fluvial deposits commonly contain fossil trees and large mainstem meandering channels with lateral accretion sets indicating that rooted vegetation stabilized channels the advent of stable floodplains with levees crevasse splays and organic litter would have encouraged the diversification of terrestrial invertebrates which left alluvial ichnological signatures from the late silurian onwards

palaeosols as indicators of geomorphic stability in two old red sandstone alluvial suites south wales palaeosols fossil soils are abundant in the alluvial late silurian early devonian moor cliffs formation and rat island mudstone freshwater west formation of south dyfed south wales the palaeosols occur in thick mudstones deposited on floodplains under a seasonal semi arid climate and represent vertisol type soils simple single profiles are rare and most of the mudstone intervals exhibit complex overprinted profiles however a major difference exists between the palaeo vertisols in each of the two units studied the moor cliffs formation contains thick floodplain intervals with evidence of frequent erosion and reactivation of earlier soil horizons the associated coarser channel deposits mainly represent ephemeral streams the alluvial system was unstable flashy and prone to extensive stripping of stored floodplain sediment arroyos unstable ephemeral stream channels probably developed during this interval evidence for any marine influence on soil development is missing and previous speculations that the formation may represent deposition in an upper intertidal or supratidal system are not supported the rat island mudstone represents a complete contrast in that there was little or no stripping of floodplain sediments the channel deposits are typically of the fining upwards type representing more stable low sinuosity channels and with ephemeral stream floods by integrating the palaeosols a more detailed picture of the geomorphic history of these units can be formulated comparison with contemporary drainage basins indicates that a change in climate was a possible cause for the differences between the two units less frequent and more severe storms occurring during the deposition of the rat island mudstone

water table rise in a semiconfined aquifer due to surface infiltration and canal recharge abstract a general solution to the fluctuation of water table for unsteady state flow in a semiconfined and finite aquifer with recharge from canals and surface infiltration is presented the flow is assumed to be one dimensional in a horizontal direction with the recharging canals at different elevations the laplace transformation method is employed in the solution a numerical example is given for a flow situation in a hypothetical finite aquifer bounded by two recharging canals under vertical infiltration giving water table changes with respect to time

water table rise due to infiltration from canals abstract analytical solutions are presented for transient water table profiles in finite unconfined aquifers due to infiltration occurring from a single canal or more than one canal the aquifer boundaries are assumed to be parallel to the alignment of the canal s and the lower impervious bottom is horizontal further the aquifer is assumed to be homogeneous and isotropic losses such as evapotranspiration are ignored likewise replenishment from other sources for example rainfall is also neglected

carbonate deposition in an ephemeral siliciclastic alluvial system jurassic shuttle meadow formation newark supergroup hartford basin usa abstract nonmarine carbonate accumulation from a sedimentologic perspective has multiple possible origins clastic load springs groundwater discharge soil development biochemical seasonal changes cave speleothems and eolian influx many of these carbonates contain diagnostic textures from which origin is easy to ascertain however differentiating between clastic and spring groundwater carbonates especially in depositional systems dominated by siliciclastics is not always simple here criteria for recognition are developed subsurface hydrology and tectonic origin of the depositional basin source rocks surrounding the basin sedimentologic packaging and extent of the carbonates in question as well as their sedimentary structures and fossil content and stable isotopic analyses of the carbonates can all aid in determining carbonate origin and correctly assessing sedimentary and basin evolution the present study focuses on a nonmarine carbonate deposit found within the jurassic shuttle meadow formation of the hartford basin one of many rift basins which formed as a result of the opening of the north atlantic ocean during the late triassic to early jurassic the upper 50 m of the formation at plainville connecticut is interpreted as continental in origin and is composed of five facies red ripple cross laminated muddy siltstones to sandstones fr sr massive red siliciclastic mudstones fm buff fine to medium grained horizontally laminated sandstones sh red to white disrupted calcareous shales fl3 and rare micritic carbonates pm facies fr sr sh and fm are interpreted as an alluvial plain system in an ephemeral setting with bedload sheetflooding as the dominant depositional mechanism similar to the channel country drainage system of central australia in addition preservation of lateral accretion sandstone sheets accretionary benches indicate that the shuttle meadow alluvial system was rapidly accreting the anomalous existence of carbonate beds in facies fl3 and pm in the smf bedload dominated siliciclastic sequence is attributed mainly to the unique nature of the clastic sediment load in the basin no direct evidence for a spring groundwater input is apparent the shallow carbonate lake margin or a pond with vegetation and periodic exposure is envisioned as the depositional environment the intraclastic texture of the micrites with rare primary relict lamination indicates early diagenetic alteration from root penetration desiccation cracks and burrowing

response of infaunal macrobenthos to the sediment granulometry in a tropical continental margin southwest coast of india abstract surficial sediment samples collected from the continental margin of the southwest coast of india in july 2004 were examined for the grain size and soft bottom macrobenthic fauna to understand the sediment granulometry and its effect on the faunal distribution samples were collected using smith mcintyre grab from 20 to 200 m depth range consisting of mid shelf outer shelf and slope fine grained sediment located in the mid shelf and supported low faunal abundance polychaetes constituted the bulk of the fauna feeding guild changed with depth and sediment granulometry coexistence of deposit feeders and carnivores in outer shelf and deposit feeders and filter feeders in the slope region indicated the effective utilization of different food resources in general richness and diversity were high in the southern region depth wise the diversity and abundance were relatively high in the 50 75 m depth range correlation and bio env analysis showed that combination of different factors such as sediment texture sediment sorting and depth were found to influence the distribution of macrobenthos hence spatial variations observed in benthic community were presumably linked to the variations in sediment granulometry and the energy level conditions prevailing in the area

diversity and distribution of echinoderms in the south eastern arabian sea shelf under the influence of seasonal hypoxia abstract the south eastern arabian sea seas margin represents a tropical eastern boundary upwelling system which is subjected to intense seasonal hypoxia in the continental shelf and impingement of oxygen minimum zone omz along the continental slope this paper provides the first comprehensive information on abundance diversity and distribution patterns of echinoderms which are highly sensitive to oxygen deficiency and anthropogenic disturbances in the continental shelf 20 250 m of the seas results are based on depth stratified and seasonally resolved sampling at 241 sites representing 8 latitudinal grids 4 depth strata from inner shelf to shelf edge using naturalist dredge and smith mcintyre grab echinoderms were the numerically dominant group among epifauna 42 with significant seasonal variations in relative abundance 71 during winter and 17 during summer monsoon fifty five species of echinoderms were identified among which ophiuroids showed highest diversity 24 species followed by echinoids 11 species and asteroids 8 species species richness of echinoderms was higher in the inner and mid shelf 20 80 m while the group was nearly absent in the shelf edge 150 250 m a significant negative correlation was noted between species richness and latitude and three distinct sub regions could be delineated based on species diversity and abundance the observed distribution patterns were found to be determined chiefly by sediment texture and bottom water dissolved oxygen along with anthropogenic disturbances bottom trawling echinoderms showed maximum abundance and species richness in the well oxygenated sandy sediments of the southern seas and very low species richness and abundance in relatively silty sediments of the northern seas which were characterised by high seasonal fluctuations in dissolved oxygen seasonal hypoxia the near absence of echinoderms in the shelf edge despite the availability of sandy substrates indicates that this group is more sensitive to the perennially low oxygen conditions prevailing here

intrusion of the bay of bengal water into the arabian sea during winter monsoon and associated chemical and biological response this work was supported by the department of ocean development under the program marine research living resources mr lr jayu narvekar acknowledges the financial support from csir

reworked calcretes their significance in the reconstruction of alluvial sequences permian and triassic minorca balearic islands spain the permian and triassic of minorca balearic islands consists of a 670 m thick red alluvial succession that includes in situ calcrete profiles and reworked calcrete material in the permian succession the calcretes vary from laminar forms developed on the carboniferous basement to weakly developed nodular calcretes in fluvial sediments the palaeosols in the triassic are mostly dolomitic and the profiles reach up to stage iii of soil development spec pap geol surv am 203 1995 1 the clasts formed through reworking of the palaeosol profiles are about 0 5 10 cm across and include mosaics of calcite dolomite crystals brecciated clasts rhizolith fragments and aggregates of clay and or silt these clasts appear in three different types of deposits type 1 corresponds to lenticular bodies that fill small scour surfaces and consists only of intraformational conglomerates these deposits are interpreted as ephemeral channels and sheet floods that represent the interfluvial drainage systems that captured only the precipitation falling on the alluvial plain type 2 includes sand dune 3 d bodies with flat bottoms and convex tops these bodies are about 20 cm high and 2 m wide and were formed by floodwaters that flowed down the levees of the major streams type 3 channel deposits contain reworked calcretes and extrabasinal clasts which overlie erosive surfaces and are found in layers within cross bedded sandstones and conglomerates these are interpreted as channel floor lag deposits of major channels that entered from distant uplands and drained the alluvial plain variations in the aggradation rates of the floodplain resulted in five different infill stages in the lowstand to early transgressive interval as in stages i p1 and iv b1 the fluvial deposits filled palaeovalleys calcretes and reworked calcrete deposits were of difficult formation apart from terraces and preservation accommodation space was at its greatest in the transgressive stages ii p2 and v b2 this caused the greatest aggradation of the floodplains which are formed of thick sequences of fine grained sediments isolated meandering channels weakly developed calcretes compound and reworked calcrete deposits mostly of types 1 and 2 the density of channels notably increased in stage iii p3 highstand interval because of the reduction of accommodation space this could favour the formation of composite or even cumulative palaeosols but of difficult preservation reworked calcrete deposits are mostly of type 3 but types 1 and 2 are also recognised the reworked calcrete deposits are an important part of the permian and triassic fluvial sediments and their occurrence and characteristics are important in order to interpret the infill of terrestrial basins and the construction of floodplains

two dimensional modelling of water table fluctuation in response to localised transient recharge abstract an analytical solution of the linearised boussinesq equation is presented and used to predict the spatio temporal variation of the water table in a finite aquifer system in response to a transient recharge from an overlying rectangular basin the boundary conditions of the finite aquifer are taken as fixed heads which would apply when the aquifer system is surrounded by open water bodies application of the solution is illustrated with the help of a numerical example the results would also have applications in studying stream aquifer interaction in the presence of transient recharge

generation transport and preservation of armoured mudballs in an ephemeral gully system abstract armoured mudballs have been reported from modern fluvial catchments and preserved in ancient quaternary and older sedimentary sequences despite many descriptions of mudballs in the literature there is little systematic analysis of their physical properties genesis transport and deposition within alluvial sequences this study uses two adjacent catchments developed on identical geology in southeast spain that offer a unique opportunity to examine the key controls on armoured mudball development as one catchment produces armoured mudball whilst the second does not field survey using a total station together with laboratory tests for material composition and aggregate stability were used to examine the catchment and the armoured mudballs the results show that the generation of the armoured mudballs is heavily dependent on the correct sediment supply suitable aggregates to act as mudball seeds and suitable fragments to source the armour and good slope channel coupling within the catchment coupling is facilitated by steep gully sides which deliver the weathered blocks of marl mudball seeds to the gully floor the seeds form the core of the mudballs in the mudball factory zone if the seeds are subjected to sealing by moisture from rainfall the mudball will hold together through negative pore pressures and can be transported by the ensuing gully flow as the mudball rolls it picks up a surface armour which becomes embedded into the mudball with longer transport paths the turbulent nature of the flow creates spherical mudballs which are size sorted downstream by the hydraulics of the flow rather than attrition armoured mudball deposition occurs within unit braid bars in areas of waning flow due to transmission losses within vegetated point or mid channel bars the armoured mudballs are preferentially deposited within the coarser bar head of these depositional units with smaller marl fragments forming the finer bar tail trenching of the bars reveals that the armoured mudballs are preserved in the subsurface although they may become increasingly flattened upon burial at depth and may be difficult to recognise due to disaggregation by roots this study suggests that armoured mudballs recognised in ancient alluvial sequences imply seasonality of climate and good slope channel coupling within the catchment area and that they are capable of transporting delicate flora undamaged making them good targets for pollen recovery in ancient alluvial sequences where armoured mudballs were present but go unrecognised in the ancient record the mode and energy of transportation and deposition of the fine sediment may be misinterpreted as the fines are in fact being transported as bedload rather than suspended load the armoured mudballs have also been noted to transport pristine microfauna such as ostracod shells from the source area material this may provide challenges to palaeoenvironmental interpretations of the mud dominated unit as environmentally significant fauna may not be contemporaneous with the unit

water table fluctuations in an aquifer system owing to time varying surface infiltration and canal recharge a solution of the linearized boussinesq equation for predicting the transient position of the water table in an unconfined aquifer system which lies between two recharging canals at different elevations above the aquifer s base and receives time varying recharge from the overlying soils is presented the solution for the constant rate of recharge is shown as a special case of the present solution the effect of variation in the rate of recharge on the water table fluctuation is investigated with the help of an example

remote forcing annihilates barrier layer in southeastern arabian sea 1 time series measurements of temperature and salinity profiles were made every two hours at 74 30 e 9 13 n in the southeastern arabian sea seas during 22 march 7 april and 23 may 7 june 2003 as part of the arabian sea monsoon experiment armex the observations show that a 20 m thick barrier layer bl exists during march april owing to a surface layer of low salinity waters advected earlier during december january from the bay of bengal the bl is almost annihilated by 7 april owing to upwelling the relic bl that survives is annihilated later in may by upwelling and by the inflow of high salinity waters from the north and by mixing due to stronger winds which deepen the mixed layer we present evidence from satellite data and arguments based on existing theories to show that both the upwelling and the advection of high salinity waters are remotely forced