palaeoenvironmental reconstruction of a middle miocene alluvial fan to cyclic shallow lacustrine depositional system in the calatayud basin ne spain the middle miocene sedimentary fill of the calatayud basin in north eastern spain consists of proximal to distal alluvial fan floodplain and shallow lacustrine deposits four main facies groups characteristic of differentsedimentary environments are recognized 1 proximal and medial alluvial fan facies that comprise clast supported gravel and subordinate sandstone and mudstone the latter exhibiting incipient pedogenic features 2 distal alluvial fan facies formed mainly of massive mudstone carbonate rich palaeosols and local carbonate pond deposits 3 lake margin facies which show two distinct lithofacies associations depending on their distribution relative to the alluvial fan system i e front lithofacies a comprising massive siliciclastic mudstone and tabular carbonates or lateral lithofacies b showing laminated and or massive siliciclastic mudstone alternating with tabular and or laminated carbonate beds and 4 mudflat shallow lake facies showing a remarkable cyclical alternation of green grey and or red siliciclastic mudstone units and white dolomitic carbonate beds the cyclic mudflat shallow lake succession as exposed in the orera composite section ocs is dominantly composed of small scale mudstone carbonate dolomite cycles the mudstone intervals of the sedimentary cycles are interpreted as a result of sedimentation from suspension by distal sheet floods the deposits evolving either under subaerial exposure or water saturated conditions depending on their location on the lacustrine mudflat and on climate the dolomite intervals accumulated during lake level highstands with mg rich waters becoming increasingly concentrated lowstand to highstand lake level changes indicated by the mudstone dolomite units of the small scale cycles reflect a climate control from dry to wet conditions on the sedimentation in the area the spatial distribution of the different lithofacies implies that deposition of the small scale cycles took place in a low gradient shallow lake basin located in an interfan zone the development of the basin was constrained by gradual alluvial fan aggradation additional support for the palaeoenvironmental interpretation is derived from the isotopic compositions of carbonates from the various lithofacies that show a wide range of 1 8 o and 1 3 c values varying from 7 9 to 3 0 pdb and from 9 2 to 1 7 pdb respectively more negative 1 8 d and 1 3 c values are from carbonate rich palaeosols and lake margin carbonates which extended in front of the alluvial fan systems whereas more positive values correspond to dolomite beds deposited in the shallow lacustrine environment the results show a clear trend of 1 8 o enrichment in the carbonates from lake margin to the centre of the shallow lake basin thereby also demonstrating that the lake evolved under hydrologically closed conditions

the devonian lacustrine sediments of orkney scotland implications for climate cyclicity basin structure and maturation history the orcadian basin of northern scotland largely of middle devonian age is a major lacustrine rift basin with the widely correlateable achanarras sandwick lake bed extending for at least 800 km along the rift above this lake bed there are about 540 m of cyclic lacustrine sediments with lake sedimentation terminated by alluvial fan progadation the upper stromness flagstone formation and the rousay flagstone formation making up this lacustrine sequence are given revised and precise definitions within four reference sections from the orkney islands the sequence consists of about 45 first order cycles averaging about 12 m in thickness which resulted from long term climatic fluctuations in rainfall with a cycle time scale of about 25 000 years longer climatic fluctuations of about 100000 and 400000 years are also present these periods correspond to the precession and two eccentricity orbital cycles detailed knowledge of the stratigraphy constrains the structural and maturation history of the basin the basin formed in a series of extensional half graben and the orkney area suffered later inversion the lake sediments first reached the oil window at relatively shallow depths c 2000 m probably in the early carboniferous implying very high geothermal gradients during the early part of the basin history as corroborated by the presence of devonian volcanics in the region in the orkney area uplift probably started in the late carboniferous

orbital scale glacio eustasy in the middle devonian detected using oxygen isotopes of conodont apatite implications for long term greenhouse icehouse climatic transitions abstract results from previous paleoclimate studies indicate gondwanan glaciation marking the onset of middle paleozoic icehouse climate conditions began by the latest devonian famennian more recently 18o trends from conodont apatite suggest cooling middle devonian subtropical seasurface temperatures 20 my prior to famennian glaciation and high latitude temperatures cool enough to permit the growth of continental glaciers which controlled longer term my scale glacio eustasy this study evaluates the details and patterns of middle devonian high frequency thirteen complete middle devonian givetian subtidal cycles 0 5 3 m thick in the little cedar formation of southeastern iowa are characterized by oxygenated offshore facies transgression poorly oxygenated offshore facies maximum flooding a return to oxygenated facies and are capped by bioturbated lower shoreface facies regression lowstand which lack evidence of subaerial exposure across shelf cyclostratigraphic facies relationships suggest relatively subdued water depth changes were responsible for cycle development measured 18o values from conodont apatite range from 15 9 to 18 4 and repeated systematic intracycle trends are dominated by lower isotopic values in offshore facies and higher isotopic values in cycle capping lower shoreface facies which is consistent with glacio eustasy driving the water depth changes the average 0 6 magnitude of intracycle isotopic shift 0 2 to 1 0 total range suggests 15 23 m glacio eustatic oscillations were responsible for observed water depth changes the higher range of intracycle isotopic magnitudes may be the result of increased subtropical evaporation rates during glacial stages which locally enriched surface seawater 18o values orbital scale

lake level changes sedimentation and faunas in a middle devonian basin margin fish bed the classic devonian fossil fish site at tynet burn fochabers ne scotland has been investigated following recent excavations the fish assemblage consists of placoderms acanthodians an actinopterygian porolepiforms osteolepiforms and a dipnoan the assemblage is typical of the 9achanarras fauna9 of eifelian age which is widespread in the orcadian basin representing a time of generally high lake levels the most diverse fauna occurs in the upper nodule bed which can be divided into top and bottom levels where fish are mainly preserved in calcareous nodules and a middle level with fish in laminated limestone three fluvial to lacustrine cycles are exposed in the tynet burn in 27 m of strata fish are abundant in the upper nodule bed and are also sparsely represented in lacustrine strata both above and below this level the lacustrine laminites of the upper nodule bed were deposited following a rapid rise in lake level subsequent fall in lake level resulted in deposition of a thin shallow water massive limestone prior to exposure and desiccation of the lake floor disruption of laminites by sediment sliding and sand intrusion was followed by compaction and concretion formation chemotrophic bacteria later invaded open cracks and porosity and partially oxidized the fish remains the bacterial oxidation event being responsible for the characteristic pink red and purple colours of fossil fish from tynet burn subsequent lake level rise resulted in deposition of shales with abundant diagenetic concretions rarely containing fish with increasing clastic input alluvial sands prograded over the area from the south the rapid deepening event associated with the base of the upper nodule bed at tynet is considered to be synchronous with similar events represented in other achanarras equivalent fish beds however elements of the achanarras fish assemblage can be encountered in less persistent lacustrine intervals both above and below this level minor cyclicity superimposed on the main achanarras event resulted in repetition of fluvial to lacustrine transitions the main control on cyclicity is considered to have been climatic but subsidence and sediment supply rates were also a significant influence

lacustrine deposits in the karheen formation fortify links between alaska s alexander terrane and the old red sandstone continent in the late silurian early devonian the karheen formation of southeastern alaska alexander terrane is an 1800 m thick redbed molasse sequence that formed during the late silurian early devonian in the wake of the klakas orogeny previous research interpreted thin platy limestone in the karheen formation as marine in origin we describe new evidence including a lack of marine fossils which indicates that the rhythmically laminated limestone formed in deep stratified lakes intercalated siliciclastic lake margin facies record cycles of lake expansion and contraction comparative analysis with coeval lake orcadie deposits in scotland shows that the karheen formation is strikingly similar in age thickness lithology paleontologic characteristics and tectonic setting to the old red sandstone together with other published geologic data from southeastern alaska the karheen s lacustrine deposits strengthen paleogeographic connections between the alexander terrane and the n atlantic caledonide region in the mid paleozoic

structural development of the devono carboniferous plays of the uk north sea decades of oil and gas exploration across the north sea have led to a detailed understanding of its cenozoic mesozoic structure however the deeper basin architecture of paleozoic petroleum systems has been less well defined by seismic data this regional structural overview of the devono carboniferous petroleum systems incorporates interpretations from more than 85 000 line kilometres of 2d seismic data and 50 3d seismic volumes plus a gravity density and magnetic study from the central silverpit basin to the east orkney basin a complex picture of previously unmapped or poorly known basins emerges on an inherited basement fabric with numerous granite cored blocks these basins are controlled by devono carboniferous normal strike slip and reverse faults the main basins across quadrants 29 44 trend nw se influenced by the tornquist trend inherited from the caledonian basement north of quadrants 27 and 28 and the presumed iapetus suture the major depocentres are ne sw e g the forth approaches and inner moray firth basins to east west e g the caithness graben and wnw ese trending e g the east orkney basin reflecting the basement structural inheritance from seismic interpretation there are indications of an older north south fault trend in the inner moray firth that is difficult to image since it has been dissected by subsequent permo carboniferous and mesozoic faulting and rifting

recognising the taghanic crisis in the devonian terrestrial environment and its implications for understanding land sea interactions the late mid devonian eday marl formation from the orcadian basin scotland is a terrestrial equivalent of the marine devonian taghanic crisis the eday marl from orkney contains a high resolution archive of climatic change controlled by the relative strength of the seasonal insolation this includes several distinct and discrete episodes of basin flooding as demonstrated by the deposition of lacustrine laminites bedded evaporites marginal sheet flood sands and marine influenced bioturbated sheet sands these flooding events are intercalated with intense and sustained episodes of aridity indicating that insolation was relatively weak and the monsoon climate was ineffective at drawing in seasonal rainfall recognition of these basin flooding events has enabled the definition of three new units the wha taing roeberry and berstane members the eday marl formation can be correlated offshore and also recognised within marginal facies as an aeolian intercalation an environmental hydrological and climatic interpretation is given for the different events recognised in the eday marl this sequence of events when combined with the palynological age dates enables a detailed correlation to be made with the marine tully formation of new york state this suggests that regressions forced by climatic aridity are significant for understanding the deposition of the shallow water carbonates of the tully formation in what is otherwise a clastic depositional system comparison with the pelagic marine record shows that the latter as yet gives only limited resolution of the taghanic crisis recognising the taghanic as a rapid alternation of cool arid and relatively hotter pluvial events provides a unifying explanation for the associated collapse in the terrestrial vegetation and the parallel faunal changes in the marine realm

late palaeozoic hydrocarbon migration through the clair field west of shetland uk atlantic margin geochemical analysis of bitumen and hydrocarbon bearing fluid inclusions from the devonian carboniferous clair field indicates that the reservoirs contain a mixture of oils from different marine and lacustrine sources reconstruction of the clair field oil charge history using fluid inclusion petrography show that oil charging occurred at times of k feldspar quartz and calcite cementation temperature composition time data yielded from the integration of fluid inclusion microthermometry with high resolution ar ar dating date hydrocarbon bearing k feldspar overgrowths at 247 3 3 ma these data show that in order for oil to be trapped within primary fluid inclusions in k feldspar overgrowths hydrocarbon migration throughout the uk atlantic margin must have been taking place during the late palaeozoic and as such current industry oil play models based solely on oil charging from jurassic cretaceous marine sources are clearly incomplete and need revision apatite fission track analysis and vitrinite reflectance data were used to reconstruct thermal burial histories and assess potential oil generation from middle devonian lacustrine source rocks thermal history data from wells along the rona ridge adjacent to the clair field show that the palaeozoic section was heated to greater than 100 c at some time between 270 and 230 ma confirming that devonian source rocks were mature and expelling oil during the late palaeozoic at the time that authigenic k feldspar overgrowths were growing in the clair field

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

evaluation of parent material uniformity criteria in loess influenced soils of west central kentucky abstract parent material relations in loess influenced soils of west central kentucky were studied to better understand the nature of the loess and its impact on the soils of that area twenty one stable landscape positions were sampled on two adjoining transects trending northwest to southeast from the ohio river to the tennessee border profiles were described in the field and samples were collected for particle size mineralogical and other laboratory analyses the soils consisted of a variable thickness loess mantle overlying residuum derived materials weathered from sandstone siltstone shale and limestone diffuse lithologic discontinuities indicating a gradual change from loessial to residual materials were observed in both field and laboratory data in most cases the laboratory data supported the presence and position of lithologic discontinuities identified by field morphology loessial and residual materials were best differentiated by clay free particle size distribution and k 2 o in the coarse silt fraction soil derived from loess and residuum was mixed at the interface of those materials the mixing was more intense where loess was thin a simple index was used to identify relative influence from each parent material type in the mixed zones

comment on the ages in paleoseismology of the johnson valley kickapoo and homestead valley faults clustering of earthquakes in the eastern california shear zone by t k rockwell s lindvall m herzberg d murbach t dawson and g berger the chronology given in this comment depends primarily on thermoluminescence and optical ages obtained for several samples i present in this comment evidence that the samples dated are considerably older than the ages presented the optical ages quoted in the article were obtained from data from my laboratory but the presentation was incomplete the authors have chosen not to include the information that severe anomalous fading was observed for the two samples for which measurements were made and the optical ages should consequently have been presented as lower limits in either thermoluminescence dating or optical dating one measures the luminescence from selected mineral grains of the sample compares it with the luminescence arising from laboratory irradiation and thus determines the past radiation dose and hence age ideally the intensity of the luminescence arising from the laboratory irradiation after the required heat treatment should not depend on the length of time elapsed between irradiation and measurement if this is not the case but the intensity decreases as a function of this time there is said to occur anomalous fading it is called anomalous because it was and to some extent is still not understood this phenomenon does not seem to occur in quartz but it does occur in feldspars it was first described in

timing and temperature of decollement on hydrocarbon source rock beds in cyclic lacustrine successions abstract the generation of hydrocarbons causes lubrication of source rock bedding planes which can enhance deformation during basin subsidence and subsequent tectonic events deformation includes decollement i e gravitational sliding of rocks above the lubricated horizon in cyclic sequences such as occur in many lacustrine basins decollement is generally restricted to the organic rich beds of the cycle case studies in lacustrine successions in the devonian orcadian basin scotland and the triassic jurassic hartford deerfield basin usa show that movement of material associated with the decollement surface occurred in the current down dip direction these extensional basins experienced rapid subsidence and a high heat flow such that hydrocarbon generation and therefore decollement occurred early in the basin histories during extension half graben rotation ensured that the beds were dipping during hydrocarbon generation facilitating decollement inversion of the orcadian basin reactivated decollement surfaces involving thrust motion in some cases minerals precipitated in tension cavities associated with decollement yield fluid inclusion homogenization temperatures in the ranges 96 139 c and 85 96 c for the orcadian and hartford deerfield basins respectively these data are consistent with burial into the oil window at depths of between 1 5 and 2 0 km

a study of vertisol genesis in north eastern greece abstract four pedons from the alluvial plain of drama ne greece were investigated in order to provide detailed information on their morphology chemical physical and mineralogical properties classification and genesis the clay content of all the samples is relatively high 35 soil reaction with hcl ranges from slightly alkaline 7 2 to alkaline ph 8 3 the organic matter content ranges from 0 53 to 1 03 in the surface horizons while the other horizons contain considerably less the caco 3 equivalent content ranges between 0 1 and 18 1 due to ploughing gilgai microrelief is absent but slickenside was apparent in all of the soils studied smectite montmorillonite is the dominant clay mineral and was mainly inherited from the parent sediments and by neoformation high smectite content in combination with alternating wet dry periods xeric soil moisture regime results in the formation of the morphological characteristics that are typical for vertisols the pedons located in the highest points of the alluvial plain were classified as chromic haploxererts and those in the lowest landscape were classified as typic haploxererts free iron oxides range between 1 3 and 1 9 for the chromic haploxererts to only 0 4 0 9 for the typic haploxererts the properties of these vertisols reflect the impact of climate alternating wet dry periods landscape position alluvial plain seasonally water saturated and parent material clayey smectite dominated fluvio lacustrine highly calcareous sediments

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

vertic properties and gilgai related subsurface features in soils of south western poland abstract more than 650 subsurface concave structures 1 20 m long 0 5 7 m wide and 0 1 0 9 m deep were described in soils developed of clays overlain by loess in a large scale archeological excavation in sw poland the structures are considered to be microlows and microhighs similar to those in gilgaied vertisols which have never been reported in central europe until now soils do not have a clayey texture throughout the profile however the thick and humus rich mollic horizons as well as a clay enriched argic layers developed directly above vertic horizons have favored soil cracking and shrink swell phenomena in the clayey subsoil as a result well developed wedge shaped lenticular aggregates have formed in the clayey subsoil aggregates have grooved surfaces with an oriented matrix slickensides and are ordered under variable angles from 10 to 60 a periglacial origin of these structures has been rejected and the mid to late holocene period since the neolithic epoch has been considered to be favorable for intense shrink swell phenomena vertic horizon development and clayey mass cycling responsible for the subsurface bowl and chimney structure development a micro mosaic of soil units related to these structures has been distinguished including non or deep vertic stagnic chernozems phaeozems above the microlow centers mollic planosols vertic above the microslopes and mollic planosols protovertic over the microhighs chimneys it is concluded that a temperate climate as in central europe allows the formation of vertic properties and subsurface mass reorganization similar to those in soils with gilgai microrelief if specific conditions clayey substratum position in landscape soil moisture regime and the land use connected with vegetation type support deep seasonal changes of soil moisture and shrink swell phenomena in the subsoil

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

the recognition of multiple hydrocarbon generation episodes an example from devonian lacustrine sedimentary rocks in the inner moray firth scotland burmah well 12 27 1 drilled on a structural high in the inner moray firth penetrated over 3000 ft 914 m of lower devonian organic rich sedimentary rocks these have been analysed for source rock potential and contain a substantial proportion of oil prone thermally mature kerogen a decompacted vitrinite reflectivity profile shows that the lower part of the devonian section has a steeper thermal maturity gradient which is interpreted as indicating a high devonian geothermal gradient associated with basin extension solid bitumen reflectivities and organic petrography show that the most recent hydrocarbon generation occurred in the upper part of the devonian interval during maximum tertiary burial vitrinite reflectivity data from the jurassic rocks in the beatrice field and onshore east sutherland enable the position of the oil generation window to be predicted in relation to the depth of the top of the devonian sequence the main controls on devonian source rock potential in the inner moray firth are not the depth of mesozoic and tertiary burial but the distribution of source rocks their degree of permian truncation and the pre permian thermal maturity level

new evidence for evaporitic middle devonian lacustrine sediments with hydrocarbon source potential on the east shetland platform north sea the ukcs united kingdom continental shelf well 9 16 3 drilled on the western flank of the beryl embayment encountered a middle devonian sequence interpreted as part of the lacustrine orcadian basin an anhydrite layer found within the sequence provides confirmation of the local development of hypersaline environments within the orcadian basin detailed geochemical analysis of a representative source interval equivalent to the achanarras sandwick fish bed has revealed a close affinity with contemporaneous middle devonian source rocks found in the inner moray firth and crude oil from the beatrice oil field

constraining causes of fish mass mortality using ultra high resolution biomarker measurement lamina by lamina measurement of biomarkers at a sub millimetre resolution within the achanarras limestone member has helped to resolve the changing environmental conditions associated with a fish mass mortality horizon an anomalous proportion of c30 sterane 24 n propylcholestane marks the beginning of the horizon and likely corresponds to an influx of marine water this appears to have been short lived and was likely analogous to a modern day storm tide the subsequent laminae record an increased incidence of water column stratification and hypoxic bottom waters in the form of an elevated gammacerane index the mass mortality horizon studied was from an upper interval of the achanarras limestone member with a fossil fish assemblage comprising mostly dipterus an early dipnoan lungfish however lower intervals of the achanarras limestone member have greater assemblage diversity including species associated with marine conditions such as coccosteus and evidence higher proportions of c30 sterane indicating better connection to the marine environment therefore it appears that ingressing seawater in and of itself was not responsible for creating a stressed environment rather disconnection of the lake from marine waters stranded fish in a lake that when perturbed by storm tides killed en masse by exposing fish to hypoxic conditions in a similar way to modern water bodies affected by storm tides generated during hurricanes

shrinkage and atterberg limits in relation to other properties of principal soil types in israel abstract soil samples collected from 32 sites across israel representing major types were analyzed for their pedological characteristics and mechanical properties correlative relationships between shrinkage measured by the coefficient of linear extensibility cole atterberg limits liquid and plastic and the physical and chemical properties were established and indicate possibilities of estimating mechanical properties from known pedological data strong correlations were noted between mechanical properties and the pedological characteristics reflecting clay mineralogy and texture e g cation exchange capacity specific surface area hygroscopic moisture and clay content these relationships are useful inasmuch as clay mineralogy is usually evident from soil classification sodicity and salinity common in dry soils of semi arid regions may introduce complicating factors such as raising or lowering atterberg limits respectively shrinkage is similarly affected being accentuated at high sodium low salt levels and reduced in highly saline sodic soils organic matter was correlated with liquid and plastic limits but no relationship with shrinkage was noted calcium carbonate also had little influence on atterberg limits the relationships presented may serve as first approximations mechanical properties of the soil groups illustrate the range of values encountered among regions with differing environmental conditions

orbitally driven climate forcing in late pliocene lacustrine siderite rich clastic rhythms upper valdarno basin northern apennines italy abstract distinctive siderite rich lacustrine strata are exposed along the western margin of the upper valdarno basin northern apennines italy these late pliocene deposits belong to the castelnuovo synthem which is the oldest unconformity bounded stratigraphic unit of the basin fill facies analyses were performed on a paleomagnetically calibrated log depicting two palustrine to lacustrine systems separated by a short lived fluvial phase the lacustrine deposits are structured in rhythms and composed of lower clastic and upper siderite enriched beds the rhythmic stacking pattern has been analysed and subjected to a cyclostratigraphic analysis similar trends between a local facies derived base level curve and global isotopic stacks suggest climate forcing which is confirmed by the straightforward tuning of the lacustrine rhythms to precession related insolation phases clastic deposition has been linked to colder and drier phases involving vegetation retreat and enhanced sediment production and transport prevalent chemical deposition siderite instead occurs during hot and wet phases and is characterised by vegetation blooming and then a generalised reduction in clastic supply this mechanism is probably coupled with lake level fluctuations that are related to variations in the regional hydrological balance the orbital behaviour of the castelnuovo synthem is characterised by major sensitivity to precession but a weaker response to 100 ky eccentricity however eccentricity modulation is marked by a 400 ky minimum which recurs in correspondence with a sub aerial exposure between the two lacustrine bedsets no obliquity related rhythmicity has been recorded the succession investigated here is consistent with other pliocene palustrine to lacustrine circum mediterranean case studies the results have also been compared to a previous cyclostratigraphic framework elaborated from magnetic susceptivity allowing critical comparisons to be made between this latter proxy and the analysis of sedimentary facies cycles

orbital climate forcing in mudflat to marginal lacustrine deposits in the miocene teruel basin northeast spain abstract upper miocene mudflat and marginal lacustrine sediments were deposited on the fringes of an alluvial fan system in the low gradient endorheic southern teruel basin northeast spain the 147 m thick prado succession consists of 55 meter scale sedimentary cycles displaying a clastic rich and a carbonate rich interval the clastic rich parts are weakly pedogenically modified red to yellow orange mudstones and are interpreted as deposits of a well drained mudflat the carbonate rich sediments consist of calcretes marls and muddy limestones the calcretes range from dispersed nodules to massive nodular and are interpreted to be of pedogenic or phreatic origin the marls and muddy limestones are light to dark gray and rich in organic matter shell fragments and gastropods they are interpreted as ephemeral pond to marginal lacustrine deposits a composite sedimentary cycle model is presented summarizing the different facies and their vertical distribution throughout the prado area on a 10 m scale distinct stratigraphic intervals show lithologic trends representing alternating wetter and drier paleoenvironments cycle characteristics are laterally consistent whereby limestone beds pinch out towards the basin margin and thicken towards the central parts of the 10 km wide and 20 km long subbasin the high resolution magnetostratigraphy resolves four normal polarity and four reversed polarity intervals that are straightforwardly correlated to chron interval c5n 2n to c5ar 1r in the atnts04 time scale the resulting age control indicates a duration of 19 to 23 kyr for the meter scale lithofacies cycles suggesting control by precession driven climate change an astronomical tuning is established by correlating each cycle to the la2004 precession curve using recently recalibrated ages for the polarity reversals as a starting point the resulting astronomical ages for the reversals in the prado section are consistent with the astronomically calibrated magnetostratigraphy and cyclostratigraphy of the marine monte dei corvi section in italy at prado three intervals with thicker than average cycle thickness most likely reflect obliquity influence during 405 kyr eccentricity minima when precession amplitudes are low this corroborates the orbital forcing hypothesis of the lithofacies cycles and the astronomical tuning of the prado succession the combined magnetostratigraphy and cyclostratigraphy method applied in this study shows the high potential of this method for detecting orbital climate forcing in continental successions

vertic soils and vertisols in cryogenic environments of southern siberia russia abstract vertisols and vertic soils are known in a wide range of bioclimatic environments the aim of this research was to identify possible vertic features in ultra continental climate with gelic soil temperature regime with maat we found that vertisols can form not only in cold environments but also in ultra continental cold environments with permafrost and negative mean annual air temperatures however their areas in buryatia are limited in size to the warmest and driest positions in the landscape namely south facing slopes the discovery of vertisols in ultra continental climates will be a challenge for current soil classification systems like soil taxonomy which will need a provisional taxonomic category to accommodate such soils under gelic temperature regimes we propose to introduce gelert suborder and vertic subgroup to haplogeloll great group

devonian marine incursions into the orcadian basin scotland bp chevron well 14 6 1 drilled in the east orkney basin has penetrated devonian sedimentary rocks which can be dated palynologically as within the latest givetian to early frasnian interval this microflora contains the first substantiated record in western europe of archaeoperisaccus a spore hitherto regarded as restricted to northern laurasia three grey green intervals within the well contain marine microfossils which provide the first direct evidence for the movement of marine waters into the northern part of the old red sandstone continent onshore an eday marls section in the bay of berstane orkney contains a marine microfauna which demonstrates the presence of a marine incursion of mid late givetian age this is the first record of a devonian marine incursion in scotland combination of this palaeontological data with sedimentological studies of the eday marls and upper old red sandstone suggests that a wide flat sabkha plain extended eastwards from the onshore orcadian basin during the later stages of its infill and was subjected to episodic marine incursions these incursions are tentatively linked with marine transgressions into the argyll area of the central north sea two orders of cyclicity occur within the dated devonian interval of 14 6 1 and are interpreted as resulting from orbital cyclicity at periodicities of 39 5 and 413 9 ky this indicates that the control on the devonian sea level maxima may have been orbital cyclicity these marine incursions are speculatively correlated to high stands on the devonian sea level curve the bay of berstane marine incursion representing the taghanic onlap whilst those in 14 6 1 are the rhinestreet middlesex and genundewa transgressions reconsideration of the palaeogeography of the northern margin to the marine devonian indicates that the sea entered the orcadian basin from the east along the tornquist zone at the margin of the fenno scandian high

closed basins and vertisol formation in the rincon lagoon andalusia spain abstract a study was made of the genetic relationship between the geomorphological phenomenon of closed basins and vertisol formation in an area of southern spain the lithology of the area the low erosive power of the drainage system and the semi arid climate are factors which favour the seasonal hydromorphism responsible for the evolution of original material into vertisols depth dissolution of keuper saline materials gives rise to the creation of basins where water accumulates forming laggons although el rincon lagoon is now a closed basin in the past it formed part of a larger lacustrine area which to a great extent gave rise to the blackening of the soils

organic geochemistry petrology and palynofacies of middle devonian lacustrine flagstones in the orcadian basin scotland depositional environment thermal history and petroleum generation potential during middle devonian time a thick succession of organic rich mainly lacustrine flagstones developed within the orcadian basin these petroleum source rocks crop out in northern scotland nineteen samples were studied using organic petrology palynology and organic geochemistry in order to characterize kerogen type depositional environment thermal maturity and petroleum generation potential c org carbonate and sulphur content as well as hydrogen index hi values are quite variable e g hi from 79 to 744 mg hc g c org based on biomarker data organic material mainly originates from aquatic organic matter deposited under lacustrine conditions with oxygen depleted but not permanently anoxic bottom waters petrography reveals small quantities of vitrinite particles indicating minor input of terrestrial material this is supported by biomarker data and the palynofacies which is characterized by a high amount of oil prone amorphous organic matter aom and generally few miospores maturity of the succession studied in caithness and orkney is between immature and oil mature one dimensional basin modelling shows that a significant remaining hydrocarbon generation potential exists within the middle devonian succession in contrast to the low hydrocarbon generation in the onshore area offshore oil generation was significant especially after deposition of thick upper jurassic upper cretaceous sediments at the end of cretaceous time hydrocarbon generation ceased due to uplift the contribution to known oil fields from the devonian flagstones is a realistic scenario including a contribution to the beatrice oil field in the south of the modelled area

palaeolimnology of palaeozoic lakes focussing on a single lake cycle in the middle devonian of the orcadian basin scotland there are few palaeolimnological studies of palaeozoic lake deposits using methodologies developed for the study of quaternary lakes new research described here indicates the benefits of applying multidisciplinary high resolution sampling and analysis on the middle devonian lake deposits of the orcadian basin in order to understand lake palaeoecology and response to water chemistry change and possible climate change in a continuously sampled 4 m thick lake cycle in two correlated boreholes in caithness there are two distinct features there is a broad trend in 13c of sedimentary organic matter from high values in the shallow water deposits to lower values in the deeper water deposits attributed to changing contributions from terrestrial plant material 13corg c 28 and algal material 13corg c 33 this variation is consistent with palynological data and is best explained by proximal distal variation as the lake filled a smaller but well correlated up section decreasing 13corg trend occurs over approximately 1 m starting at the cycle centre where the lake was at its deepest since the same feature is seen in two boreholes we suggest that local effects of migrated bitumen diagenesis or facies changes are unlikely to be the cause and that changes in the carbon cycle of the lake are responsible explanations for this trend may relate to the source of carbon that algae utilised as the lake changed from a fresher to a more saline environment and to changes in the carbon isotope composition of the lake water during periods of enhanced productivity

organic maturation thermal history and hydrocarbon generation in the orcadian basin scotland the devonian orcadian basin contains thick sequences of organic rich lacustrine sediments of interest as hydrocarbon source rocks throughout the basin the range of organic maturation is large spore colours vary from yellow orange to black and vitrinite reflectance for type iii kerogens ranges from 0 7 to 10 5 maximum palaeotemperatures are estimated to range from those typical of moderate burial diagenesis 100 c to those characteristic of greenschist facies metamorphism 400 c the highest maturities are related to contact metamorphism by devonian plutons and it is postulated that a large pluton underlies much of caithness high and low maturity regions are often juxtaposed across major faults which were active during variscan inversion regionally the lowest maturity is about 0 8 r o implying uplift and erosion of 2 3 km of cover basin wide this cover was probably a sequence of late devonian and carboniferous rocks removed largely during variscan uplift geothermal gradients were high but variable during devonian extension this together with the contact metamorphic affects of the devonian plutons resulted in early maturation metamorphism of large areas of the basin most of the onshore sequence entered the oil window during devonian and carboniferous times significant generation of hydrocarbons from orcadian lacustrine facies offshore during subsequent mesozoic burial will have occurred only in those areas which escaped maturation during the palaeozoic

facies analysis of a back tilted lacustrine basin in a strike slip zone lower devonian scotland abstract lower devonian lower old red sandstone basins developed along active faults in northern scotland the dingwall strathpeffer basin is a half graben which thickens into the helmsdale polinturk fault a splay off the major strike slip great glen fault zone facies analysis allows the distinction of facies associations which represent alluvial fan perennial lake and playa mudflat ephemeral stream environments syn sedimentary faulting at the margin was the major control on alluvial fan sedimentation the lacustrine facies were fringed by alluvial facies but at times of high water level extended to the active basin margin sedimentary structures and pseudomorphs after gypsum suggest an arid to semiarid environment in which the alluvial fan stream and floodplain sedimentation was largely ephemeral during arid periods the basin centre lake environment was constricted and the surrounding mudflats experienced intense evaporation while after flooding episodes the lake increased in size the thickest lacustrine sequences occur close to the basin margin alluvial fans due to back tilting of the fault blocks fault motion and or climatic fluctuations caused significant interdigitation of the facies the mixture of alluvial fan and organic rich lacustrine facies close to the bounding fault offers some potential for trapping of hydrocarbons

ripple marks indicate mid devonian paleo wind directions in the orcadian basin orkney isles scotland abstract few climate proxies provide information on paleo wind directions however fossilized bedform elements can provide insight into the direction of flow that formed them wave formed ripple marks for example which developed in shallow waters extend transversely to the wind direction in this study middle devonian paleo wind directions are reconstructed by measuring the orientation of 511 fossilized wave ripple marks in the rousay flagstone formation on the island of westray orkney scotland the orientation of ripple marks was measured in four different localities on the island a chi squared test demonstrates that these four ripple mark subsets show the same distribution of ripple mark orientation and thus indicates that the studied ripple marks display the same distribution of paleo winds two dominant ripple mark orientations were observed at all studied localities the most abundant ripple mark orientation suggests paleo winds from the present day north or south second most abundant are ripple marks that suggest paleo winds from the present day ene or wsw 70 or 250 when a 40 clockwise rotation of orkney since the middle devonian is taken into account the ripple marks suggest that the dominant wind directions were south southeast sse and north northeast nne in the tropical setting of the orcadian basin the sse wind direction is represented by the abundant ripple marks with a present day near n s orientation of the line perpendicular to the crests these ripple marks are also characterized by the largest wavelengths the abundance of the latter ripple marks with long wavelengths is the result of a lower water level and thus a larger wave exposed surface during the dry winter season from april to july which was mainly characterized by sse paleo trade winds

structural geology of easter ross scotland implications for movement on the great glen fault zone the integration of a recently drilled exploration well sited near the town of tain ross shire with a seismic database and onshore exposures allows a new interpretation of the structure in the easter ross peninsula ne scotland it is now evident that previous interpretations which highlighted the importance of ne sw striking lineaments need some modification instead numerous n s to nne ssw trending folds and faults affect devonian sequences and show evidence of compressional reactivation of structures which had previously experienced extension these inversion structures only appear to be dissected by ne sw and e w striking faults and extensional fractures in areas adjacent to the great glen fault zone integration of the onshore data with results from adjacent offshore areas suggests that the peninsula has undergone a complex structural history since the early devonian it appears to have been characterized by early devonian probably rift related extensional faulting and subsequent mid late devonian regional thermal subsidence the restriction of similar structural relations to devonian sequences on offshore seismic lines from adjacent areas suggests that the contractional and inversion structures which similarly affect the late palaeozoic sequences in onshore areas were probably related to permo carboniferous structural events rather than younger deformation further integration of offshore data with the occurrence of jurassic sequences on the coast suggests that the peninsula may be considered an integral part of the inner moray firth basin and experienced a similar mesozoic subsidence history to offshore areas before undergoing regional uplift and dissection due to reactivation of the great glen fault zone during the cenozoic there is no evidence to suggest that this fault zone had any significant control on basin development sedimentary sequences or structural geometries during palaeozoic or mesozoic periods of extension and it probably only had minor effect during permo carboniferous inversion similarily its role in tectonic events after the early cretaceous appears to have been limited to local deformation with little evidence for any large scale strike slip offset along its length the unusual occurrence of jurassic coastal exposures in easter ross appears to represent fault bounded slices of sediment downfaulted to accommodate the formation of a negative flower structure in response to limited dextral strike slip movement the results suggest that the great glen fault zone was a strike slip fault system effectively locked during phases of extension in the inner moray firth but was reactivated during phases of inversion when extensional slip vectors sub paralleled the lineament