tectono sedimentary characteristics of late miocene quaternary extensional basins of the northern apennines italy abstract extensional and compressional regimes exist at the same time in adjacent parts of the northern apennines italy and the former regime succeeded the latter at the same place as the thrust mountain front moved eastward since miocene times numerous extensional basins have developed west of the present mountain divide the westernmost ones formed over attenuated continental crust since late miocene and have been subjected to several subsidence and uplift events with rates of subsidence generally faster than rates of sedimentation they contain continental deposits overlain by gypsum bearing upper miocene marine sequences and siliciclastic marine pliocene deposits these basins were affected by shallow magmatism and are still experiencing high geothermal gradient and late to post magmatic activities such as in the renowned thermal region of larderello to the east closer to the present mountain divide the extensional basins formed later from pliocene to quaternary contain continental fluvial and lacustrine deposits and have not experienced near surface magmatic activities the sedimentary fill architecture of the apennine extensional basins is similar to that of other european american and african extensional or transtensional systems for instance a common characteristic is the prevalence of large alluvial fan deposits at the hanging wall shoulder of half grabens coarser smaller alluvial fans at the footwall shoulder and some fluvial deposits introduced longitudinally unlike the african rifts though the sedimentary facies distribution of extensional basins which developed in active orogenic zones such as in the apennines may be strongly affected by uplifting steep mountain slopes and can have large thick coarse alluvial fans also on the footwall side of the half grabens

field design and operation of a novel deepwater wide azimuth node seismic survey many new deepwater subsalt gulf of mexico developments are afflicted by poor imaging caused by the complex nature of their salt overburdens the atlantis field is an example a poor image of its northern flank hindered development the ocean bottom seismic obs autonomous node method was applied with the goal of substantially improving the subsalt reservoir image

reverse time migration a prospect of seismic imaging methodology abstract reverse time migration rtm is a seismic imaging method to map the subsurface reflectivity using recorded seismic waveforms the practice in exploration seismology has long established a two fold approach of seismic imaging using velocity modeling building to establish the long wavelength reference velocity models and using seismic migration to map the short wavelength reflectivity structures among various seismic migration methods for different situations rtm is the only method that is capable to use all seismic wave types that can be computed numerically being initiated in early 1980 s rtm seeks an image of the subsurface reflectivity as the best match in an image space between the extrapolation of time reversed waveform data and the prediction based on estimated velocity model and source parameters judging the image quality in the same space of forming the images is more advantageous than the approaches of modeling and inversion which seek the solution in the model space but judge its fitness in data space considering that most seismic migration applications today still use primary reflection as the only signal the capability of rtm to use all computable wave types is unique and helpful reducing the imaging artifacts due to mistaking non primary waves as primary reflections hence we refer to those rtm algorithms using only primary reflections as the first generation rtm methods and the rtm algorithms making a full use of primary reflections multiple reflections and other non primary waveform data as the second generation rtm methods this paper reviews the development history of the rtm along with its major challenges current solutions and future perspectives

stratigraphy and genesis of a modern shoreface attached sand ridge peahala ridge new jersey abstract we investigated the genesis and evolution of peahala ridge a modern shoreface attached sand ridge 1 km 6 km in size and 4 7 m in bathymetric relief through an integrated sedimentologic and stratigraphic study involving vibracoring box coring grab samples high resolution seismic paleontology radiocarbon dating and oceanographic measurements near surface strata of peahala ridge include six important stratigraphic units modern shoreface upper ridge sand lower ridge sand swale inlet fill middle holocene back barrier and late pleistocene strandplain radiocarbon dating and determination of the stratigraphic relationships indicates that peahala ridge formed initially from an ebb tidal delta associated with a tidal inlet so thwestward migration of the inlet channel a vector resultant of landward coastal retreat and southerly longshore drift cut and then filled the swale separating peahala ridge from long beach island following inlet closure peahala ridge developed its present form as a shoreface attached shoreline oblique bathymetric feature hydrodynamic processes have played a major role in evolution of the ridge including considerable growth and accretion this combination of long term eustatic and short term hydrodynamic factors is the best explanation for the present morphology and internal stratigraphy of peahala ridge

facies descriptions and associations in ancient reworked transgressive shelf sandstones cambrian and cretaceous examples preferred facies trends in ancient shallow marine sediments have been determined by markov chain and substitutability analyses of detailed sections measured in lower cambrian outcrops in the southern canadian rocky mountains st piran formation 600 m of vertical section fort mountain formation 500 m of vertical section and in a cretaceous subsurface reservoir in south central alberta viking formation in the garrington field 69 cores those sections with more defined cycles are interpreted to result from progradation of shelf ridge sands and gravels examples with less defined order originated as inter ridge deposits in zones with complex palaeoflows and in areas of subdued palaeotopographic relief the highest degree of facies organization 80 significant facies transitions occurs in the cretaceous viking formation sandstone and conglomerate ridges interpreted to have had abundant sediment supply water depths between fair and storm weather wave base and a strong littoral current system a moderate degree of facies organization 70 significant facies transitions occurs in the inter ridge deposits of the cambrian fort mountain formation interpreted to have had a variable sediment supply water depths above storm weather wavebase and a variable oscillating tidal current system a poor degree of facies organization 45 significant facies transitions occur in the ridge deposits of the cambrian fort mountain and st piran formations and in the inter ridge deposits of the cambrian st piran and cretaceous viking formations this facies disorganization occurs in sites where there was continuous and rapid subsidence cambrian or in areas of subdued seafloor relief with complex current systems cretaceous the pattern of facies relationships also varies relatively short linear patterns occur in all of the shelf ridge deposits this contrasts with the inter ridge deposits in which there are long linear patterns or complex ring structures interpreted to result from complex palaeoflow patterns in areas of subdued seafloor topography various statistical techniques including markov chain and substitutability analyses can aid the interpretation of very complex lithological successions as shown by the shelf sandstones and conglomerates examined in this study

oligo miocene rift of sardinia and the early history of the western mediterranean basin the geodynamic evolution of the western mediterranean basin in spite of many studies is still uncertain there is some consensus for interpreting this basin as a kind of small oceanic marginal basin its opening has generally been related to a subduction process which was active during the oligocene miocene somewhere east of sardinia corsica1 7 as the margins of the basin are deeply buried below miocene to present sediments direct lithological and stratigraphical data which could explain the events responsible for its formation are rare8 10 or missing altogether to obtain such data detailed field studies have been undertaken in sardinia fig 1 and the first results are presented here this approach is justified by the fact that in that island oligocene and miocene sediments were deposited in a rift fossa tettonica sarda of verdabasso11 which is the easternmost arm of the complex rift system that affected the european plate during oligocene and miocene times one of these arms evolved towards a small oceanic basin the western mediterranean or algero provencal basin while others such as the gulf of valencia and the sardinia rift aborted and remained at the rift stage its exceptional exposures make it possible to examine the sardinia rift to clarify the sequence of events which created it and to establish a sedimentological model which we believe is directly applicable to the western mediterranean basin

benefits of full azimuth and ultralong offset data for subsalt imaging in the deepwater gulf of mexico abstract in deepwater regions of the gulf of mexico the ability to image subsalt structures has improved significantly with wide azimuth data reverse time migration and anisotropic tomography and imaging however subsalt imaging such as imaging steeply dipping salt flanks and subsalt three way closures still remains difficult in areas with complex salt geometry moreover limited subsalt illumination provides insufficient incident angles for residual curvature tomographic analysis full azimuth and long offset acquisition configurations are the latest acquisition technologies designed to address these subsalt challenges an improved subsalt imaging and tomography updating using staggered acquisition provides full azimuth data coverage and ultralong offsets

stratigraphic sequences and their chronostratigraphic correlation abstract the exxon sequence models of posamentier and coworkers incorporate two concepts which i question they suggest that rivers grade to a bayline but evidence from modern major rivers indicates that they do not they also proposed that fluvial sedimentary accomodation space is generated by the seaward shift in equilibrium profiles during sea level fall but this is too simplistic a model based on the use of schematic continental margin configurations which do not incorporate real slope and relief data in most cases a fall in base level leads to deltaic progradation and upstream fluvial incision most coastal plain fluvial wedges result from two processes sea level rise with the drowning and filling of estuaries and active source area tectonism major tectonic events adjacent to foreland basins such as terrane collisions lead to the development of sequences of third order type duration approximately 1 15 m y changes in intraplate stress regimes resulting from changes in regional plate kinematics have a similar episodicity and can be shown to be responsible for some third order cycles on extensional continental margins examination of the chronostratigraphic basis of the mesozoic cenozoic cycle chart of haq and coworkers reveals internal inconsistencies and an unrealistic downplaying of the built in potential for error this chart is not an approved global standard and it should be used with extreme caution

investigation of soils developed on volcanic materials in nisyros island greece abstract soils that are forming on volcanic parent materials have unique physical and chemical properties and in most cases on wet and humid climates are classified as andisols the main purpose of this study is to examine if the soils that are forming on volcanic materials under a dry mediterranean climate in nisyros island greece meet the requirements to be classified as andisols soils from seven sites were sampled and examined for their main physico chemical properties and selective dissolution analysis dithionite citrate bicarbonate dcb extractable al and fe al d fe d acid ammonium oxalate extractable al fe and si al o fe o and si o and sodium pyrophosphate extractable al and fe al p fe p were measured in addition al and si were determined after reaction with hot 0 5 m naoh al naoh and si naoh and with tiron c 6 h 4 na 2 o 8 s 2 al t and si t p retention was also measured the soils are characterised by coarse texture low organic matter content low values of cation exchange capacity cec and high ph values values of si o al o and fe o are less than 0 022 0 09 and 0 35 respectively highlighting the lack of noncrystalline components the ratio fe d fe o 100 fe d is quite high expressing the degree of crystallisation of free iron oxides for all samples tested values of the al o 1 2fe o index are extremely low naoh and si t arising 2 76 and 2 18 respectively indicate the presence of silica in amorphous forms p retention values are very low

a soil chronosequence in the semi arid environment of patagonia argentina abstract soil development with time was investigated on beach ridges with ages ranging from about 1380 to 6240 14c years bp at the eastern coast of central patagonia the main pedogenic processes are accumulation of organic matter and carbonate leaching and accumulation within the upper part of the soils soil formation is strongly influenced by incorporation of eolian sediments into the interstitial spaces between the gravel of which the beach ridges are composed different amounts of eolian material in the soils lead to differentiation into leptosols containing 10 fine earth in the upper 75 cm and regosols containing 10 fine earth soil depth functions and chronofunctions of organic carbon calcium carbonate ph ca zr mg zr k zr na zr fe zr mn zr and si al obtained from x ray fluorescence analysis were evaluated to establish soil chronofunctions mean values of the horizon data of 0 10 cm below the desert pavement were used which were weighted according to the horizon thicknesses the depth function of ph shows a decrease towards the surface indicating leaching of bases from the upper centimeters chronofunctions of ph show that within 6000 radiocarbon years of soil development ph drops from 7 0 to 6 6 in the leptosols and from 8 1 to 7 5 in the regosols the higher ph of the regosols is due to input of additional bases from the eolian sediments chronofunctions of ca zr and k zr indicate progressive leaching of ca and k in the regosols showing close relationships to time r2 0 972 and 0 995 na leaching as indicated by decreasing na zr ratios shows a strong correlation to time only in the leptosols r2 0 999 both leptosols and regosols show close relationships to time for fe zr r2 0 817 and 0 824 mn zr r2 0 940 and 0 803 and si al 0 971 and 0 977 indicating enrichment of fe and mn and leaching of si leaching of mobile elements takes place on a higher level in the regosols than in the leptosols from the beginning of soil formation hence a significant part of the eolian sediments must have been incorporated into the beach ridges very soon after their formation

a review on the driving mechanism of the tyrrhenian apennines system implications for the present seismotectonic setting in the central northern apennines abstract the formation of the tyrrhenian apennines system has been characterized by a complex distribution of major tectonic events such as opening of basins migration and distortion of orogenic belts retreat of trench zones stopping of consuming processes and starting of new subductions the various aspects of each event such as timing location dimension and deformation style impose important constraints on the genetic mechanism in this work we argue that the numerous constraints implied by all events together may be plausibly and coherently explained as effects of the convergence of the confining africa arabia and eurasia plates crucial evidence for discriminating among the various geodynamic hypotheses so far advanced is provided by the structural tectonic information recently provided by crop seismic sections in the study area the proposed evolutionary history is illustrated by several paleogeographic maps which provide a more detailed reconstruction than previous attempts particular attention is paid to describing the tectonic setting developed since the middle pleistocene in the apennines belt and its connection with seismic activity

paleoenvironmental and paleoclimatic interpretations of the late paleocene goler formation southern california u s a based on paleosol geochemistry the paleocene was characterized by high global temperatures and elevated concentrations of atmospheric co2 paleoclimate records of this epoch are of particular interest to understanding the effects of anthropogenic climate forcing as well as linkages between the paleocene climate and major tectonic and evolutionary events however terrestrial paleoclimatic records of the paleocene are limited in their spatial extent and few such records are known from western north america in this study paleosols from two members in the late paleocene goler formation of southern california were used to investigate local paleoclimatic conditions the paleosols were described in detail and analyzed for morphology clay mineralogy and bulk geochemistry carbonate nodules present in paleosols from the upper member member 4a were characterized using petrographic and cathodoluminescence microscopy and were analyzed for carbon and oxygen stable isotope composition enrichment and retention of soluble elements ca mg and na and the mobilization of fe and mn in the paleosol profiles suggest a climate with strongly seasonal precipitation this interpretation is further supported by the presence of pedogenic slickensides and the clay minerals smectite and illite the appearance of pedogenic carbonate nodules in paleosols from the upper member is suggestive of a shift to more arid or more seasonal conditions that is coincident with a prominent change in sediment provenance and an inferred increase in sedimentation rate uplift of the ancestral sierra nevada during the late paleocene was likely an important control on regional paleoclimate due to the effects of elevated topography on mean annual precipitation and seasonal distribution of precipitation the correlation of a shift in pedogenic processes with changes in provenance and sedimentation rate suggests that the evolution of regional tectonic activity was an important control on these processes during the deposition of the goler formation

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

evolution of a classic sand ridge field maryland sector north american inner shelf the ridge and swale topography of the middle atlantic bight is best developed on the delaware maryland inner shelf here sand ridges can be seen in all stages of formation several aspects of the ridge field are pertinent to the problem of ridge genesis the first is ridge morphology there is a systematic morphologic change from shoreface ridges through nearshore ridges to offshore ridges which reflects the changing hydraulic regime as successively more seaward ridges are examined maximum side slope decreases the ratio of maximum seaward slope to maximum landward slope decreases and the cross sectional area increases these changes in ridge morphology with depth and distance from shore appear to be equivalent to the morphologic changes experienced by a single ridge during the course of the holocene transgression a second aspect is the change in bottom sediment characteristics that accompanies these large scale morphologic changes megaripples sand waves and mud lenses appear in the troughs between nearshore and offshore ridges these changes indicate that the storm flows which maintain ridges are less frequently experienced in the deeper sector and that the role of high frequency wave surge becomes less important relative to the role of the mean flow component in shaping the sea floor a third aspect is the systematic relationship of grain size to topography grain size is 90 out of phase with topography so that the coarsest sand lies between the axis of the landward trough and the ridge crest while the finest sand lies between the ridge crest and the axis of the seaward trough this relationship is characteristic of large scale bedforms finally flow was measured and transport calculated on the same ridge during a one month period november 1976 threshold was exceeded only during storm events mean transport was southerly and a little seaward with respect to both the ridge crest and the shoreline these flow measurements are in conformity with the pattern of smaller bedforms a 43 year time series of bathymetric change for this ridge reveals a systematic pattern of landward flank erosion seaward flank deposition and seaward crest migration sand ridges are considered the consequence of constructive feedback between an initial topography and the resulting distribution of bottom shear stress the relationship between grain size and topography supports this model but does not account directly for the oblique angle of the ridge with respect to the coastline this feature may be due to a more rapid alongshore migration rate of the inshore edge of the ridge than the offshore edge and the relationship between this migration rate and the rate of shoreface retreat

a two stage rifting in the basins of the corsica sardinian straits abstract a set of seismic and field data from the corsica sardinian straits allowed us to define three well separated oligocene deep basins the castelsardo and porto torres basins forming the northern end of the sardinian graben and the bonifacio basin on the continental shelf of the bonifacio straits a seismostratigraphic investigation of these three basins revealed two major tectonic events a first oligocene to middle aquitanian rifting phase followed by oceanic spreading in the western mediterranean and then a second rifting event between corsica and sardinia in lower burdigalian time the first rifting is noticed in the three basins but the second one only in the porto torres and castelsardo basins

paleosol and dolocrete associated clay mineral occurrences in siliciclastic red sediments of the late miocene komisini formation of the tuzgolu basin in central turkey abstract the late miocene was characterized by high global temperatures and partly to nearly complete desiccation of the mediterranean sea throughout the latter part of the messinian age the messinian salinity crisis the late miocene marine mediterranean sea area has been widely studied from different perspectives but terrestrial paleoenvironmental and paleoclimatic records from the mediterranean area are highly limited in their spatial range to this end the paleosols dolocrete and fluvial sedimentary rocks of the komisini formation in the northwestern part of the tuzgolu basin are described in detail six lithofacies were identified as a clast supported gravel b massive pebbly sandstone c massive mudstone d disrupted mud e disrupted conglomerate and f disrupted matrix supported conglomerate the siliciclastic facies were interpreted as braidplain and the distal part of braidplain deposits is associated with an ophiolitic area while the disrupted mud and disrupted conglomerate were identified as three types of paleosols inceptisols aridisol and vertisols the calcretes occur in the paleosols in nodular powder and massive forms clay minerals include smectite chlorite palygorskite illite and serpentine gypsum smectite and chlorite are dominant minerals at the base and middle part of the section whereas palygorskite and illite appear as the prevailing clay minerals in the upper sections smectite illite and palygorskite precipitated in a vadose zone from strongly evaporated alkaline water rich in si ca and mg and poor in al at increased temperatures and at an advanced stage of dolocrete and paleosol formation k si mg al fe and ca are required for smectite illite palygorskite and calcification given the increase in ba cr ni and co these cations might have originated from ophiolite carbonate and volcanic units as a consequence the vertical distribution of clay mineral types suggests the variations of paleoclimatic conditions during the deposition and the relationships among the type of host rock paleosol and dolocrete which corresponds to nearly complete desiccation of the mediterranean sea

extensional tectonics on sardinia italy insights into the arc back arc transitional regime although the tectonic features and stress regime typical for accretionary complexes and back arc domains have been widely documented so far few are known on the transitional zone separating these two systems here we report on structural analysis and anisotropy of magnetic susceptibility ams results from eocene pliocene sediments exposed in western sardinia from late oligocene to middle miocene the studied area was located between the alpine apennine wedge to the east which was undergoing shortening and accretion and the liguro provencal basin undergoing extension and spreading we find that prior to the formation of the liguro provencal basin the middle eocene lower oligocene sediments cropping out at the southwesternmost edge of sardinia were subjected to ne sw shortening in present day coordinates in agreement with recently reported geological information conversely the upper oligocene pliocene sedimentary sequences record a different evolutionary stage of extensional processes upper oligocene middle upper burdigalian sediments clearly show a n s oriented magnetic lineation that can be related to extensional direction along the prevalent e w oriented normal faults on the other hand no magnetic lineation has been detected in upper burdigalian serravallian sediments which mark the end of the first rifting process in sardinia which likely coincides with the rift to drift transition at the core of the liguro provencal basin finally a ne sw extension is observed in two tortonian pliocene sites at the northwestern margin of the nnw sse oriented campidano graben our study confirms that ams may represent a valuable strain trajectory proxy and significantly help to unravel the characters of temporally superimposed tectonic events

formation of clay minerals in soils developed from basic volcanic rocks under semiarid climatic conditions in lanzarote spain abstract clay formation in soils was studied in four landscapes of different ages in lanzarote canary islands landscape iv b is about 250 years old iv a subrecent iii early young pleistocene and landscape i late tertiary the soils have developed from basic to ultrabasic pyroclastic fall deposits or basalt clay formation in soils of landscape iv b is in an initial stage having a clay content of 1 2 kg m 2 whereas in landscape iv a 30 40 kg m 2 and in landscape iii 100 200 kg clay m 2 are accumulated in polygenetic soils of landscape i more than 3000 kg clay m 2 can be found in the youngest soils iv b smectite is the most prominent clay mineral whereas iv a soils are dominated by amorphous clay the clay fraction in older soils contains illite smectite as well as kaolinite in smaller quantities the chemical composition of the clay fraction of soils with different ages changes significantly according to the mineral composition

geochemical and mineralogical evidence for sahara and sahel dust additions to quaternary soils on lanzarote eastern canary islands spain africa is the most important source of dust in the world today and dust storms are frequent on the nearby canary islands previous workers have inferred that the sahara is the most important source of dust to canary islands soils with little contribution from the sahel region soils overlying a late quaternary basalt flow on lanzarote canary islands contain in addition to volcanic minerals quartz and mica exotic to the island s bedrock kaolinite in the soils also likely has an exotic origin trace element geochemistry shows that the soils are derived from varying proportions of locally derived basalt and african dust major element geochemistry clay mineralogy and interpretation of satellite imagery suggest that dust additions to the canary islands come not only from the sahara desert but also from the sahel region

shannon sandstone in wyoming a shelf ridge complex reinterpreted as lowstand shoreface deposits abstract the shannon sandstone campanian of wyoming was formerly interpreted as two stacked shelf ridge complexes sand was believed to have been transported from a time equivalent shoreline 110 150 km to the west and reworked or molded into ridges at the depositional site we show that this time equivalent shoreline section at lucerne wyoming consists of not one shoreface sandbody but two superimposed they are both storm dominated and the lower one terminates in beach facies capped by root traces there must have been a rise in relative sea level of at least 14 m to make accommodation space for the second shoreface sandbody in the salt creek area and the adjacent subsurface teapot dome there are two sandier upward facies successions in the lower succession there are abrupt vertical acies contacts between offshore bioturbated sandstones thicker hummocky cross stratified sandstones and coarser cross bedded sandstones there is also evidence that the cross bedded sandstones rest erosively on underlying facies the trace fauna in the sandstones includes macaronichnus segregatis rosselia socialis and ophiomorpha the m segregatis suggests a foreshore or upper shoreface depositional environment and r socialis indicates a lower to middle shoreface neither are characteristic of a shelf ridge complex the abrupt and probably erosive facies contacts along with the trace fauna suggest that the cross bedded sandstones in this succession represent a shoreface deposit that formed during a stage of actively falling relative sea level overlyi g muddy bioturbated sandstones indicate that shoreface deposition was terminated by a transgression the upper sandier upward succession contains facies and trace fauna similar to those of the lower succession and is also interpreted as a prograding shoreface rather than the sand moving 110 150 km from the shoreline and then being molded into shelf ridge complexes at salt creek we suggest that the shoreline moved into the salt creek area as the result of a fall in relative sea level it was transgressed and moved back westward a second fall of relative sea level moved the shoreline back to salt creek and a final transgression terminated shannon deposition

testing a soil development model against southern norway soil chronosequences abstract the first results of modeling soil development in marine sediments in s norway using the model soilgen are compared to measured properties of two soil chronosequences on the western and eastern side of oslofjord respectively the aim of this work is to test how well soil development under well defined environmental conditions can be modeled such testing reveals to what degree soil forming processes are understood allowing formulation of adequate calculations reflecting these processes the model predicts particle size distribution reasonably well although clay depletion in the upper parts of the soils as a result of clay migration is overestimated the model tends to underestimate contents of organic carbon and cec in the a horizons below modeled cec matches well with measured cec base saturation is overestimated in the upper 40 cm and underestimated below apparently leaching of bases proceeds less rapidly in reality than is predicted by the model due to strong soil structure of the b horizons causing preferential flow and base leaching around the aggregates whereas bases inside the aggregates are only slightly affected by leaching difficulties and possibilities for improvements are identified some related to model input data and some to the model itself input data could be improved by determining the amounts of organic carbon in organic surface horizons and by quantifying effects of bioturbation a big challenge is the implementation of soil structure formation in the model quantitative data on the development of soil structure with time that can be included in a model are required amounts distribution and connectivity of macro pores need to be defined for each stage of soil development and zones of low and high base leaching need to be distinguished in the model for each time step the long term aim of this work is to model soil development with different sets of soil forming factors e g different climatic conditions in order to reliably predict soil development under different climate scenarios and related sets of soil forming factors the results of the first model runs and the identified possible improvements suggest that this aim is generally achievable

shannon sandstone depositional model sand ridge dynamics on the campanian western interior shelf the campanian shannon sandstone member of the cody shale forms the reservoir for several significant oil fields in the western powder river basin of wyoming the extensive data set available for this economically important unit makes it one of the best known ancient analogs to the sand ridges of modern shelf seas the shannon sandstone was deposited as linear ridges by intermittent along shelf southerly storm flows in a transgressive middle to outer shelf environment of the cretaceous interior seaway comparison of shannon sandstone bodies with modern sand ridges shows that they were formed in response to the kind of flow field observed over the modern systems the long axes of these bodies are aligned northwest southeast to north northwest south southeast the sandstone bodies are asymmetric in transverse section northeastern flanks are shorter and steeper than the gentle accretion surfaces on the southwestern flanks paleocurrent direction is southerly hence the sandstone bodies are aligned obliquely with respect to the prevailing transport direction as required by hydrodynamic theory the four basic lithofacies types recognized in these sand ridge deposits are cross bedded sandstone thin bedded sandstone bioturbated silty sandstone and lenticular bedded to bioturbated siltstone the cross bedded lithofacies has tabular trough glauconitic trough cross bedded and bioturbated variants this lithofacies grades down section and down current into a thin bedded lithofacies comprising flaser to wavy bedded sandstone and low angle laminated sandstone this thin bedded lithofacies overlies a widespread massively bioturbated sandstone lithofacies which in turn rests disconformably on a siltstone lithofacies the distribution of lithofacies within a shannon sandstone body is most readily explained in terms of the velocity distribution over a sand ridge and textural modification by the distortion of the regional flow field over the growing sand ridge the up current flank underwent erosion and deposition occurred on the crest and down current side so that the sand ridge grew and migrated in a southwestward direction each sand ridge served as a fractionation mill in which successive environments on the transport pathway across the ridge extracted successively finer grades of sand from the transported load

pot and gutter casts from the chapel island formation southeast newfoundland abstract member 2 of the chapel island formation of southeast newfoundland contains a diverse suite of erosional structures known as pot and gutter casts these are particularly abundant in a lithofacies deposited in a nearshore zone characterized by erosion and sediment bypass during storm emplacement of sands the steep to overhanging walls of both pot and gutter casts imply rapid filling during the same storm events that created these depressions erosion is thought to have taken place under strong offshore directed unidirectional flow storm surge or other relaxation flow as with many sandstone tempestites the initial stages of the storm events were dominated by strong and in this case highly erosive unidirectional flow and the latter stages by oscillatory flow as evidenced by wave diagnostic lamination in the sandy infills pot casts have geometries and soles indicating vortex flow similar to that which forms potholes in bedrock in glaciated regions gutter casts that lead into potholes do so at their edge a requirement for generating rotary currents within the depression pot casts are commonly tilted relative to paleohorizontal and their direction of plunge is either upcurrent or downcurrent variation in geometry of the erosional structures from the chapel island formation and from erosional structures in general can be accounted for by the following substrate type diagenetic history of substrate and flow parameters such as pattern of water motion velocity and intermittency of flow

shannon sandstone in hartzog draw heldt draw fields cretaceous wyoming usa reinterpreted as lowstand shoreface deposits abstract the lower campanian shannon sandstone at hartzog draw heldt draw powder river basin wyoming is interpreted in the literature as a shelf ridge complex deposited 160 km from the contemporaneous shoreline this interpretation poses difficult problems and does not discuss the significance of bounding discontinuities preserved in the sandbodies cross sections show that the shannon sandstone is present at several stratigraphic horizons and is bounded by regionally extensive discontinuities the presence of these bounding discontinuities suggests that fluctuations in relative sea level were important in controlling geometry of sandbodies on the shannon shelf in the hartzog draw heldt draw area of wyoming the base of the shannon is a planar surface with respect to a lower bentonite marker and is characterized by the abrupt appearance of bioturbated sandstone on top of black basinal mudstone siderite pebbles 1 cm in diameter are common at this contact in hartzog draw the bioturbated sandstone interval has an average thickness of 10 m and is separated from an overlying unit of cross bedded fine to medium sandstone up to 20 m thick by a ubiquitous 50 cm thick horizon of mud clasts in a cross bedded highly glauconitic medium sandstone these three units are laterally continuous in hartzog draw except where removed by erosion the top of the shannon is marked by an abrupt change from the cross bedded sandstone or bioturbated medium sandstone to laminated black mudstone mud clasts siderite pebbles chert grains and glauconite mark this abrupt contact suggesting erosional transgression this surface can be traced westward where in many areas it is a mud on mud contact marked by a lag of shell debris this transgressive surface which terminates shannon deposition is characterized by at least one regionally extensive onlapping marker in the hartzog draw heldt draw area the presence of depositional discontinuities in the shannon sandstone is suggested by 1 the sharp basal contact 2 the lateral continuity of individual facies 3 the abrupt vertical facies changes and the association of mud clasts siderite pebbles and glauconite accompanying these abrupt juxtapositions of facies 4 the stratigraphic variability and 5 the termination of shannon deposition by erosive transgression marked by onlapping markers these depositional discontinuities are the bounding discontinuities these bounding discontinuities have asymmetrical one sided scour morphologies with steeper landward margins that flatten basinward these geometries and the linearity of the overlying sandstone and the troughs defined by these scoured surfaces suggest incised shoref ce profiles truncated by erosive transgression thus the shannon sandstone in hartzog draw heldt draw is reinterpreted as a lowstand shoreface deposit

evidence of mis 5 sea level highstands in gebel mousa coast strait of gibraltar north of africa abstract the last interglacial is considered the most suitable episode from which to infer patterns of rapid sea level change since its climatic conditions were similar to those of the present interglacial however specifying the true position of its sea level with high accuracy is very troublesome in the absence of sedimentological erosional or even palaeontological markers this study investigates the morphosedimentary evidence beach deposits cliff notch and shore platform of two highstands registered and dated during mis 5 stage by u series dating in the north of morocco strait of gibraltar bioerosive notches and mixed siliciclastic and carbonate deposits high energy beaches with algal bioherms were formed in coastal environments during mis 5a a sea level height of 10 m asl can be inferred for this substage the record of mis 5e substage is less defined in the geomorphological record consisting of backshore foreshore deposits located at 13 to 15 m asl a tectonic uplift rate of 0 1 mm yr has been estimated for the last 130 kyr these data are consistent with models of coastal uplifting calculated for the strait of gibraltar

weathering and soil forming processes under semi arid conditions in two mexican volcanic ash soils abstract weathering and neoformation of allophane imogolite and halloysite in volcanic ash soils have been studied extensively in humid climates but little data are available on these soils in arid and semi arid conditions weathering and soil formation under semi arid conditions on acid pyroclastics have been investigated in two profiles both at the micro site scale and on bulk samples xr microdiffractions and sem edx microanalysis were performed on soil thin sections chemical particle size xrd and mineral identification analysis were performed on conventional soil samples results show the interplay of various sub processes a intense division of the coarse minerals into small fragments 50 200 m in size b diagenesis of noncrystalline products in the zone of contact with the parent minerals c transformation of noncrystalline minerals into halloysite in the compact soil microstructures and preservation of the noncrystalline minerals in the topsoil d desiccation and condensation of the crystalline and noncrystalline minerals into microaggregates in the topsoil the results of these interacting weathering processes are silty loam soils with no cohesion and high susceptibility to wind erosion differences appearing between different analytical methods at different sampling scales need special precautions in explaining the results

siliciclastic carbonate sequences of miocene grabens of northern sardinia western mediterranean sea abstract the small crustal block of sardinia island western mediterranean underwent major rifting events during oligocene early miocene aquitanian early burdigalian and plio pleistocene times sedimentation in the resulting extensional and transtensional basins was affected by both local tectonic and worldwide sea level changes the mixed siliciclastic carbonate sequences which developed are readily comparable with those predicted by sequence stratigraphy this paper focuses on the post volcanic uppermost burdigalian to lower messinian sedimentation at the confluence between a main n s trending basin and a secondary sw ne trending graben in northern sardinia silty marlstones of late burdigalian early langhian age characterize the central part of the main basin whereas variable siliciclastic and carbonate sequences affected by up to three major transgression and regression cycles developed at its margins and at the confluence with the smaller graben differential movements along the main boundary fault led to rotation of blocks which localized narrow elongated offshore algal carbonate platforms low sea level stand led to deep erosion type 2 sequence boundary of these carbonates and to the formation of siliciclastic sandy lowstand wedges high sea level stand led to re establishment of algal platforms at the shelf margin which were bounded farther inland by siliciclastic carbonate mixed parasequences although it is not possible to date directly every stratigraphic unit local sequences are well structured and can be tentatively correlated with reported worldwide transgressive regressive events

sedimentary basins formed and carried piggyback on active thrust sheets small sedimentary basins that formed on the apennine southern margin of the po basin complex northern italy have been studied using borehole and seismic reflection information and their evolution can be dated using the largely marine biostratigraphy of the miocene to quaternary sediments these studies show that the basins formed and were filled while being carried on moving thrust sheets and they are therefore named piggyback basins each of these basins corresponds to the active phase of a different thrust front ramp on the pyrenean northern margin of the ebro basin complex northern spain similar piggyback basins formed between eocene and mid miocene time they have since been uplifted and eroded and may therefore be studied in outcrop in northern spain much of the basin fill sediment was deposited in nonmarine environments

the miocene of pianosa island key to understanding the opening of the northern tyrrhenian back arc basin central mediterranean the only place where neogene quaternary rocks crop out for the entire tuscan archipelago in the northern tyrrhenian sea is the island of pianosa in particular the miocene deposits record the depositional and tectonic evolution of the northern tyrrhenian region during this time period these deposits are subdivided into two successions separated by a low angle unconformity the older middle burdigalian succession represents a calciturbidite shallow marine system whereas the younger late tortonian early messinian succession comprises a continental alluvial system that evolves upwards into a lagoonal marginal marine environment here we present sedimentological palaeontological and petrographical data that support a new stratigraphic and palaeogeographical framework for reconstructing the opening of the northern tyrrhenian back arc basin the early miocene succession records a pre rift marine depositional phase followed by a late burdigalian langhian erosional phase this was followed by a period of synrift continental marginal deposition as recorded by the late miocene succession terminated by an important phase of uplift probably induced by the start of magmatic activity in the tuscan archipelago area

pleistocene and holocene soil carbonates from lanzarote canary islands spain paleoclimatic implications abstract periods of soil carbonate formation have been used to separate the upper pleistocene and holocene paleoclimate of lanzarote island into three stages an early semi arid wet period 26 000 yrs b p a dry arid period until 14 000 yrs b p and a return to semi arid conditions correlated with deglaciation in northern latitudes these three stages correlate with the paleoclimate record in northern africa and the near east where two upper paleosol horizons are found goodfriend magaritiz 1989 that may be correlated with the two stages of carbonization in the study area this extends climatic correlation for this time interval from the eastern mediterranean to the mid latitude atlantic region

the manciano sandstone a shoreface deposit of miocene basins of the northern apennines italy abstract well exposed diamond line cut quarry exposures of the manciano sandstone allow a detailed analysis of sandy fossiliferous nearshore deposits of the shelf of the northern apennines the manciano sandstone is characterized by medium to very coarse washed fairly well sorted lithic sandstone with thin interlayers of sandy conglomerates it displays two principal rhythmically alternating sandy facies a slightly burrowed mostly macaronichnus ophiomorpha skolithos units trough cross bedded locally showing possible tidal bundles with few whole scutella echinoid shells reworked on foresets or occasional large scale approximately 2 m planar cross bedded bar accretion units and b slightly finer darker coloured reddish brown sandstone units heavily bioturbated cruziana skolithos ichnofauna representing slightly more sheltered settings large oysters are present in near living position in a few thin layers and more commonly as reworked comminuted fragments in sandy layers many calcareous pebbles and oyster fragments are bored other fossils consist of echinoids scutella some balanids and reworked foraminifera and bryozoa the manciano sands were deposited primarily in a wave dominated shoreface containing migrating bars ridges and affected by wave induced possibly tidal enhanced currents this tidal influence confirms the opening of the miocene apenninic sea to oceans both the developing atlantic ocean to the west and through a long narrow seaway the asian portion of the tethys sea to the east

weathering sequence of soils from volcanic ash involving allophane and halloysite new zealand abstract the clay minerals in a series of soils from rhyolitic ash having the same stratigraphy but different leaching environments were estimated quantitatively by oxalate dissolution infrared spectroscopy differential thermal analysis electron microscopy and x ray diffraction three soils were studied in detail these were the kereone soil mean annual rainfall 1200 mm the ohaupo soil 1400 mm and the mairoa soil 2600 mm the kereone soil contained halloysite as the predominant clay mineral whereas the mairoa soil was mainly allophanic the ohaupo soil contained considerable amounts of both allophane and halloysite thus the allophane content of the soils increased as rainfall increased reflecting a sequence of increased l leaching the si concentration in soil solution decreased as rainfall increased also reflecting increasing leaching of the soils at mairoa si is rapidly removed and allophane al si 2 1 with monomeric silicate is formed whereas at kereone less leaching occurs si levels are higher and halloysite al si 1 1 with polymeric silicate is formed at intermediate sites either allophane or halloysite may form the often reported situation of younger allophanic beds overlying older 10 000 year halloysitic beds may not be due to allophane weathering to halloysite but may result from lower temperature and drier climate during the last glacial maximum between 10 000 and 26 000 years before present bp a new weathering scheme for volcanic ash in new zealand is presented

stromatolites in the late ordovician eureka quartzite implications for microbial growth and preservation in siliciclastic settings well preserved siliciclastic domal stromatolites up to 2 m wide and 1ae 5m high are found in a 10 to 15 m thick interval within the late ordovician eureka quartzite of southern nevada and eastern california usa these stromatolites appear as either isolated features or patchy clusters that contain more than 70 by volume quartz grains their association with planar trough and herringbone cross bedding suggests that they were formed in an upper shoreface environment with high hydraulic energy in this environment sand bars or dunes may have provided localized shelter for initial microbial mat colonization biostabilization and early lithification of microbial mats effectively prevented erosion during tidal flushing and storm surges and the prevalence of translucent quartz sand grains permitted light penetration into the sediment leading to thick microbial mat accretion and the formation of domal stromatolites decimetre scale to metre scale stromatolite domes may have served as localized shelter and nucleation sites for further microbial mat colonization forming patchy stromatolite clusters enrichment of iron minerals including pyrite and hematite within dark internal laminae of the stromatolites indicates anaerobic mineralization of microbial mats the occurrence of stromatolites in the eureka quartzite provides an example of microbial growth in highly stressed siliciclastic sedimentary environments in which microbial communities may have been able to create microenvironments promoting early cementation lithification essential for the growth and preservation of siliciclastic stromatolites

occurrence of rhodolites in the tropical pacific a consequence of mid miocene paleo oceanographic change abstract rhodolites occurring over wide areas of the tropical pacific solomons loyalties vanuatu and australes are dated in many places by diagnostic larger foraminifera as of middle miocene age they are preceded in early miocene and succeeded in late miocene by hermatypic coral deposits the processes linking this facies change with time to paleo oceanographic events documented in deep sea sediments are identified as sea level rise drowning the reefs a slight drop of winter surface water temperature and an increase of the fertility of surface waters inhibiting compensatory growth of hermatypic corals until sea level fall restored the earlier original conditions of deposition