late pleistocene relic ultisols and alfisols in an alluvial fan complex in coastal tuscany detailed stratigraphic sedimentary facies and palaeosol analyses were performed on an outcrop on late quaternary deposits in the coastal area of tuscany the outcrop was selected as representative of one of the major quaternary alluvial fan complexes of central italy the ancient cecina river fan and as showing contrasting if related palaeosols the oldest relic palaeosol was identified as an ultisol representative of the most developed soil type normally found as relic soil in italy and about whose possible ages only approximate interpretations presently exist osl dating set the whole succession of sediments palaeosols and geomorphic surfaces into a firm chronological setting as a result evolution of the cecina fan complex in late pleistocene could be fully reconstructed assessment of the age of the relic ultisol produced results contrasting with current interpretations showing how such a soil type can have developed in italian conditions in a relatively short time i e since about mis 5d

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

lack of enhanced preservation of organic matter in sediments under the oxygen minimum on the oman margin the impingement of oxygen minima on continental margins is widely thought to promote the accumulation of sedimentary facies enriched in well preserved organic matter it is shown here however that such a relationship does not clearly apply to the productive oman margin in the arabian sea which hosts one of the most severe oxygen minima in the oceans measurements made on the 0 1 cm depth interval from fourteen box cores collected from the outer shelf upper continental slope area off oman show that 1 1 deposited organic matter is overwhelmingly of marine origin 2 2 there is no significant correlation between the abundance of sedimentary organic carbon corg and the bottom water o2 concentration 3 3 there is no relation between the sedimentary corg n ratio and bottom water o2 4 4 there is no correlation between the hydrogen index hi of the organic matter and bottom water oxygen there are however significant correlations between the corg n ratio and the i corg cr al and zr al ratios as well as between the corg n ratio and the hydrogen index these relationships are interpreted as being the result of winnowing and attendant reworking which produce a progressive increase in the corg n ratio and a decrease in the hi and the i corg ratio as organic matter becomes progressively degraded commensurate rises in the cr al and zr al ratios result from the increased proportion of heavy minerals associated with winnowed lag deposits overall these data suggest that the bottom water oxygen concentration has little effect in governing either the distribution or the degree of preservation of organic matter on this margin thus the generally high but spatially variable corg content of the sediments on the oman margin may not reflect the occurrence of an oxygen minimum but instead be the result of a high settling flux of organic matter supported by monsoon driven upwelling and post depositional redistribution of the organic material by hydrodynamic influences

segmentation and configuration of subducted lithosphere in italy an important control on thrust belt and foredeep basin evolution the apennine foredeep basin system located on continental crust consists of four roughly parallel basin segments each containing a flexural outer rise and an inner trough that deepens continuously toward the thrust belt flexural modeling of subsidence data across the basin indicates that this foredeep basin results mainly from deep subsurface loads acting on the subducted slab from within the subduction zone rather than from the topographic load of the apennine mountains the geometry of the four basin segments observed within the apennine foredeep is thus inferred to reflect subduction of segmented lithosphere where each lithospheric segment corresponds to a segment of the foredeep basin beneath the basin and in the foreland the lithosphere is continuous segmentation occurs only at depth beneath the thrust belt this pattern olf segmentation of the subducted lithosphere at depth is reflected in the large scale geometry of the outer part of the apennine thrust belt and appears to control it similarly the pattern of segmentation also appears to control the position of the eastern limit of back arc type extension in western italy these relations strongly suggest a genetic relation between subduction zone processes foredeep basin geometry and thrust belt evolution in which the configuration of the subducted lithosphere largely controls the large scale surface deformation observed in the apennine system

impact of in situ stress and fault reactivation on seal integrity in the east irish sea basin uk abstract despite having been affected by several stages of exhumation during the cretaceous and cenozoic the contemporary stress state of the east irish sea basin eisb is poorly characterised as the basin is mature in terms of exploitation of hydrocarbons future exploration beyond the conventional sherwood sandstone group reservoir triassic necessitates a greater understanding of the in situ stress field while proposed natural gas storage and carbon sequestration schemes also require detailed stress field information using petroleum well data the in situ stress field of the eisb has been characterised to assess the mechanical seal integrity a strike slip stress regime most likely prevails in the basin meaning the maximum horizontal stress shmax is the greatest of the principal stresses interpretation of stress orientation data suggests that shmax is oriented 152 12 consistent with mean stress orientations across the wider region associated with plate boundary forces some degree of structural control appears to influence the orientation of shmax with orientations locally aligned sub parallel to major permo triassic basin bounding faults fault reactivation risk is evaluated through modelling the pore pressure increase required to induce failure on pre existing faults vertical faults striking 30 from shmax are optimally oriented to become reactivated under elevated pore pressure conditions for any project relying on an element of fault seal for the containment of buoyant fluids at the average reservoir depth of 800 m pore pressure increase should be less than 3 3 mpa to avoid reactivating pre existing optimally oriented faults higher pressure increases would be required to initiate reactivation of faults with other orientations vertical faults striking perpendicular to shmax are least likely to become reactivated and in the absence of halite seal integrity would instead be limited by caprock strength and capillary entry pressure major faults affecting the basin have been analysed for their slip tendency ratio of shear to normal stress which provides an indication of their susceptibility to become reactivated although the analysis is limited due to lack of an accurate 3d representation of the fault network the results suggest that many of the fault orientations observed in the eisb exhibit high slip tendencies including n s striking faults to the north and west of the east deemster fault where the shmax orientation is nw se faults striking perpendicular to shmax such as the lagman fault are least likely to become reactivated due to higher normal stresses that inhibit frictional sliding while faults striking parallel or very close to shmax also exhibit low slip tendency as they are not subjected to significant shear stresses

palaeoenvironment of braided fluvial systems in different tectonic realms of the triassic sherwood sandstone group uk abstract fluvial successions comprising the fills of sedimentary basins occur in a variety of tectonic realms related to extensional compressional and strike slip settings as well as on slowly subsiding passive basin margins a major rifting phase affected nw europe during the triassic and resulted in the generation of numerous sedimentary basins in the uk much of the fill of these basins is represented by fluvial and aeolian successions of the sherwood sandstone group additionally regions that experienced slow rates of mesozoic subsidence unrelated to triassic rifting also acted as sites of accumulation of the sherwood sandstone group one well exposed example being the eastern england shelf the fluvial depositional architecture of deposits of the sherwood sandstone group of the eastern england shelf a shelf edge basin is compared with similar fluvial deposits of the st bees sandstone formation eastern irish sea basin a half graben the two studied successions represent the preserved deposits of braided fluvial systems that were influenced by common allogenic factors climate sediment source delivery style differences in preserved sedimentary style principally reflect their different tectonics settings analysis of lithofacies and architectural elements demonstrates that both studied successions are characterized by amalgamated channel fill elements that are recorded predominantly by downstream accreting sandy barforms the different tectonic settings in which the two braided fluvial systems accumulated exerted a dominant control on preserved sedimentary style and long term preservation potential on the eastern england shelf the vertical stacking of pebbly units and the general absence of fine grained units reflect a slow rate of sediment accommodation generation 18 19 4 m myr in this shelf edge basin successive fluvial cycles repeatedly reworked the uppermost parts of earlier fluvial deposits such that only the lowermost channel lags tend to be preserved by contrast in the eastern irish sea basin of west cumbria the rate of sediment accommodation generation was substantially greater 119 m myr such that space was available to preserve complete fluvial cycles including silty drape units that cap the channelized deposits

facies discrimination in a mixed fluvio eolian setting using elemental whole rock geochemistry applications for reservoir characterization abstract fluvio eolian successions are generally characterized by a high degree of complexity and internal heterogeneity quantifying the rapid facies changes in time and space is a major challenge to characterization of hydrocarbon reservoirs we present a method for facies discrimination in fluvio eolian successions the method presented here is developed on the modern fluvio eolian sediments from the skeleton coast dune field namibia the examined sediments comprise eight different facies types eolian dune sands interdune fluvial channel sands intraerg mass flow deposits intraerg hyperconcentrated flow deposits fluvial channel sands fluvial mud lacustrine heterolithic sand and lacustrine heterolithic mud the contrasting provenance of the fluvial and eolian sediments results in a distinct source fingerprint which can be discriminated using elemental whole rock geochemistry a multivariate statistical technique performed on the geochemical data has enabled discrimination of seven of the eight facies types furthermore the facies discrimination method allowed a quantitative estimate of the degree of fluvial reworking of eolian sand the skeleton coast dune field was chosen as a test area for geochemical facies discrimination because of its remarkable difference between the immature fluvial source and the mature quartz rich eolian source we hope that the method presented here can be applied to subsurface data from geological settings with the same difference in fluvial and eolian sources it is furthermore hoped that the method can be used in more complex sedimentological settings

unchanged nitrogen isotopic composition of organic matter in the south china sea during the last climatic cycle global implications the 15n of surface and down core sediments spanning the last 20 200 kyr from the entire south china sea scs ranges only from 3 0 to 6 5 with no correlation with discernible paleoclimatic oceanographic changes detailed profiles of the uppermost sediment column including fluff samples indicate a minor diagenetic overprint of 0 3 1 2 at the sediment water interface the absence of any correlation with reconstructed glacial interglacial changes in primary production terrigenous input and or sea level related basin configuration is attributed to a complete consumption of nitrate during primary production in this marginal basin during at least the last 140 000 years this in turn implies that the 15n of the nitrate used during primary production remained approximately constant during the last climatic cycle the proposed scenario infers an unchanged nitrogen isotopic composition of the western pacific subsurface nitrate between glacial and interglacial stages as well as during terminations and thus constrains proposed changes in the oceanic n inventory

hoanib river flood deposits of namib desert interdunes asanalogues for thin permeability barrier mudstone layers inaeolianite reservoirs abstract the ephemeral braided hoanib river of nw namibia ows for a few days ayear and only high discharges enable the river to pass through interdunaldepressions within the northern namib desert dune eld to the atlantic thedune eld comprises mainly large transverse dunes resulting frompredominant ssw winds river ood deposits between aeolian dunes areanalogous to mudstone layers conformably interbedded with ancientaeolianite dune foresets deep oods pond laterally to considerable depths metres to 10 m in adjacent interdunes depositing mud layers 1 50 cm toconsiderable heights on avalanche and stoss faces of bounding dunes fairlypassive ooding only disturbs aeolian strati cation minimally floodwaterclay in ltrates and settles as an impermeable seal with a ood pond on top perched above regional groundwater flood ponds evaporate slowly for longperiods 3 years early emergence desiccates higher parts of a mud layer subsequent oods can re ll a predecessor pond bene ting from the existingimpervious seal potential preservation of such mud layers is lower on thestoss face but high on the avalanche face after burial by subsequent dunereactivation and migration the leeward right hoanib bank a dune stoss face is river and wind eroded to exhume fossil interdune pond mud layers of anearlier hoanib channel the highly inclined layers are interbedded with duneavalanche foresets and represent the edges of two successive fossil pondsexposed in plan ancient ood pond mudstones occur in the permian triassichydrocarbon reservoir the sherwood sandstone group of the cheshire basin kinnerton formation and irish sea basin and were previously usederroneously to argue against the aeolian origin of cross bed sets hoanibstudies show that primary river interaction with a dune eld might preserveonly localized erosional omission surfaces in ancient aeolianites with littlesandy barform preservation prone to aeolian reworking around the main uvial channel locus however ood pond mudstone layers should form apredictable halo within which uid permeability will decrease keywords aeolian dunes aeolianite reservoir ash ood interdune namibdesert namibia permeability introductionhigh discharge oods of the hoanib river occa sionally break through the skeleton coast dune eld which forms part of the extensive namibdesert that parallels the western margin of thesouthern african subcontinent this arid regionis 140 km wide and over 2000 km long fromsouth western angola to the northern capeprovince south africa the northern namib dune eld termed the skeleton coast dune eld bywilson 1973 lancaster 1982 and ward sedimentology 2002 49 719 736

diagenetic effects on porosity permeability relationships in red beds of the lower triassic bunter sandstone formation in the north german basin abstract carbonate and anhydrite cement clay clasts and inter granular clay are the main components that reduce reservoir quality in the studied bunter sandstone formation the impacts of these parameters on porosity and permeability are determined by combining petrographic mineral quantification with conventional core analysis of samples from the danish part of the north german basin the depositional environments are considered because they largely control the distribution of cements clays and grain sizes the lateral variability of depositional environments is defined by the position in the basin and the proximity to the source areas the stratigraphic distribution of depositional environments is related both to local topography and to climate because high aridity promoted aeolian deposition the bunter sandstone formation has high porosity and permeability in most of the sandstone intervals in the northern north german basin the reservoir quality is good as long as the cements and clays are present as confined bodies that leave the remaining pore spaces available for flow in contrast inter granular clay and pervasive cementation hinder virtually all flow through the sandstone the ephemeral fluvial deposits have an average porosity and permeability of 20 3 and 810 md respectively and the values are 24 6 and 807 md for the aeolian sandstones excluding the unconsolidated aeolian sands which presumably have higher porosity and permeability the aeolian sandstones of the volpriehausen member have very good reservoir quality since they have a thickness of about 25 m are laterally continuous are largely clay free and the cement occurs in small amounts the sandstones of the solling member consist mainly of ephemeral fluvial deposits which generally have good reservoir quality however some intervals have high contents of inter granular clays or pervasive carbonate anhydrite or halite cement and these components reduce the permeability significantly the lateral distribution of the ephemeral fluvial sandstones is variable and therefore difficult to predict when planning a geothermal exploration well thus the volpriehausen member is the preferred target

pin stripe lamination a distinctive feature of modern and ancient eolian sediments abstract pin stripe laminations are a distinctive feature of modern and ancient eolian sediments in sets of eolian ripple or translatent strata they represent deposition of silt and very fine sand in the troughs of the advancing wind ripples in sets of avalanche strata they probably result from the downward settling of fine sand and silt within the moving avalanche to the interface of moving and unmoving sands wind tunnel experiments suggest that pin stripe laminations can also form in grainfall deposits the textural segregation associated with deposition of the fine layers in most cases leads to early cementation along and near the finest sand and silt comprising the pin stripe lamination the pin stripe effect seen in outcrops is usually due to resistance to weathering along such cemented zones the cementation of the pin stripe laminations can occur early in the history of diagenesis and thus may provide clues to the post depositional history of the rock pin stripe laminations in many instances represent the sequestering of the small population of ultrafine sediment present in most eolian depositional systems they may prove useful in the recognition of ancient eolian sediments

late glacial to holocene changes in winds upwelling and seasonal production of the northern california current system abstract a core 120 km off the coast of southern oregon was examined for changes in lithology diatoms and pollen over the past 30 000 yr primary production during the late pleistocene was about half that of the holocene evidence from diatoms and pollen indicates that summer upwelling was much weaker implying an absence of strong northerly winds early pliocene diatoms found throughout the late pleistocene section were probably derived from diatomites east of the cascades and provide evidence for strong easterly winds over a dry continental interior the findings verify predictions of a climate model based on glacial maximum conditions there is no compelling evidence for a climatic reversal corresponding to the european younger dryas chron during the early holocene 9000 7000 yr b p there may have been years when winds were insufficiently strong to support upwelling so that warm stratified waters lay closer to the coast

ultrasonic logging across unconformities outcrop and core logger sonic patterns of the early triassic middle buntsandstein hardegsen unconformity southern germany abstract the recognition of unconformities in thick and monotonous sandstone successions of consistent grain size is often difficult in locally exposed surface outcrop sections and also poorly constrained by changes of petrophysical properties across the boundary surfaces here a mobile ultrasonic device is tested as a time efficient handheld logging tool to investigate relative changes in sandstone cementation and porosity across the early triassic middle buntsandstein hardegsen unconformity in southern and central germany a persistent offset of 18 20 sonic transit time occurs in all tested sections across the unconformity this offset is not restricted to single peaks but clearly separates the different sonic patterns of the hardegsen and solling formations below and above the unconformity integrated thin section analysis porosity permeability measurements and gamma density logging suggest that these changes in sonic transit time are due to major variations in sandstone cementation and the formation of secondary porosity associated with the unconformity field based ultrasonic measurements thus provide a useful addition to established outcrop logging methods and may help in the non destructive in situ identification of porosity cementation heterogeneities in sandstones in the localization of unconformities and in the correlation of borehole measured sequence boundaries to outcrop analogs

biomarker temperature estimates for modern and last glacial surface waters of the california current system between 33 and 42 n sea surface temperature sst estimates were made using data for c37 39 alkenones analyzed in modern and glacial age intervals of sediment cores collected along an east west 42 n from 125 to 132 w and a north south 41 33 n transect of the california current system ccs the prymnesiophyte biomarker results suggest that surface waters warmed significantly throughout this region since the last glacial maximum lgm but the magnitude of warming varied spatially stratigraphic profiles from four sediment cores along the north south transect indicate the warming period was confined to the glacial interglacial transition 15 10 ka with sst reaching a maximum value at 10 ka and maintaining a uniformly high value throughout the holocene comparison of estimates derived from analysis of modern and lgm sediment intervals indicates the magnitude of the sst change was minimal for locations south of about 36 n 1 2 c and increased significantly 3 5 c north of this latitude using a simple heat balance model we calculate from the latitudinal gradient in sst that southward flow in the california current system during the lgm was about 60 of that measured today at 36 n our findings support the conclusion of others based on pollen data that coastal upwelling in the region of the northeast pacific off northern california was significantly reduced or even completely shutdown during the lgm

fault array evolution in extensional basins insights from statistical analysis of gravel deposits in the cecina river tuscany italy two statistical analyses of gravel clasts from the lower pleistocene deposits in the lower cecina valley tuscany italy have been combined to unravel changes in the palaeo drainage system data from 16 outcrops were collected and 6400 clasts described facies analysis micro palaeontology and macro palaeontology and petrographic characteristics of the gravel deposits have highlighted the presence of three allostratigraphic units clast lithology is the main discriminator among these units cluster and principal component analyses of the 6400 clasts have improved understanding of the stratigraphy of the lower pleistocene deposits and constrain the re routing of the lower palaeo cecina river from a supposedly south east to north west direction to the present east to west direction short rivers feeding small fan deltas represented by the oldest allostratigraphic units were abandoned in the lower pleistocene when the re routing of the cecina river caused the capture of these streams this evolution suggests a change in the tectonic regime of the area the fan deltas developed on the hanging wall of normal faults sub parallel to the coast a change to a transtensile tectonic regime caused the deviation of the main river channel toward the present coast and the formation of a pull apart basin which is now exploited by the cecina river this study illustrates the value of lithological analyses of gravel deposits for understanding the tectonic evolution of an area

the statistics of counting clasts in rudites a review with examples from the upper palaeogene of southern california usa the relative proportions of gravel sized particles of different lithology in rudaceous sedimentary rocks are generally determined in the field by clast counting clast counts are usually carried out qualitatively in order to assess sedimentary provenance however a review of the statistical aspects of clast counting suggests that this technique also can be applied quantitatively and to investigate a variety of other objectives during basin analysis geographical and stratigraphical changes in the relative proportions of clasts can be quantified statistically and used to characterize sediment dispersal patterns in space and time respectively statistical comparisons between clast assemblages can be used as a tool to match up rock units this approach may help to constrain tectonic or suspect terrane models or to document sediment recycling both counting and sampling errors contribute to the total probable error of a clast count sampling error results from the uneven distribution of clasts in outcrop perhaps caused by selective sorting counting error arises from a count of some number less than the total number of clasts in the population sampling and counting errors can be minimized by counting in closely spaced subsets and by counting a total of at least 400 clasts respectively thus a useful procedure is to count four closely spaced subsets of 100 each and combine the results for a total of 400 point counting should not be used because differences in particle size produce biased results a better method is to count all clasts above some minimum size within a specified area of outcrop analysis of upper palaeogene non marine conglomerates composing part of the sespe formation in california using confidence intervals hypothesis testing analysis of variance ratio analysis and varietal studies demonstrates that useful statistics can be derived by counting clasts

the east irish sea basin from caterpillar to butterfly a thirty year metamorphosis in the thirty years since the award of the first licenses the east irish sea basin has emerged as a significant hydrocarbon province this paper first lists some of the occasionally almost arbitrary events that led to the first success in the basin the discovery of the morecambe field in 1974 an attempt is made to review progress over those thirty years in certain topics namely 1 stratigraphy 2 structure 3 sedimentology 4 diagenesis the platy illite problem and others 5 uplift and inversion 6 hydrocarbon sources and types 7 east irish sea basin analogues the paper concludes by summarizing the current state of knowledge 1995 represented the thirtieth anniversary of the first award of licences in the east irish sea basin eisb the twenty sixth anniversary of the drilling of the first wells and the twenty first anniversary of the discovery of the south morecambe field it is perhaps appropriate to look back on some of the crucial events of the last thirty years and on some of the earlier concepts and interpretations with a view to seeing how these last have progressed or been found wanting undoubtedly the biggest spur to exploration was the discovery in 1974 by the british gas corporation subsidiary hgb ltd of the south morecambe field how a fledgling organization came to discover this 5 tcf gas accumulation in its first venture is itself noteworthy key events that led to this discovery might be summarized as follows 1 the wish of the government in power in 1969 to foster a national presence in the exploration of british waters by allowing the then gas council to take 100 interests in eisb blocks 2 the readiness of the gas council to exploit this opportunity 3 the unwillingness of the council s main north sea partner to participate in the proposed application with its offer of a firm well 4 the unwillingness of other majors to join the application 5 the informal gift by gulf in 1973 of the logs of wells 110 8 1 and 2 on the basis of a gentleman s agreement that hgb would likewise make data available from any wells it

the termination of the equatorial undercurrent in the eastern pacific abstract the termination of the equatorial undercurrent euc in the eastern tropical pacific has been studied through analysis of the historical hydrographic station data in the region bounded by 5 n 10 s 80 w and 100 w three distinctive hydrographic features associated with the euc are used along with dynamic topography to trace the mean path of the euc and to investigate aspects of its seasonal variation these features are 1 the 13 c thermostad 2 the high salinity core and 3 the high dissolved oxygen concentration tongue the thermostad is thickest just south of the equator to the west of the galapagos islands with a decreasing maximum extending southeast to the coast of south america near 7 s the thermostad is poorly developed in the mean near the equator east of the galapagos islands this pattern appears to be produced by convergence of eastward flow in the euc and in the southern subsurface countercurrent as the euc flows southeastward from the galapagos this interpretation is supported by the geostrophic flow calculated from the mean dynamic topography the isolated high salinity core is found to the south of the equator and is traced all the way to the coast of south america the high oxygen tongue associated with the euc splits at the galapagos with the southward projecting branch disappearing rapidly as an identifiable feature the other branch of the tongue continues around the islands to the north and along the equator to the coast of ecuador some evidence of recirculation of euc water in the south equatorial current is seen to the northwest of the galapagos a strong seasonal pulsation of the euc affects these features in a consistent way with the pulse occurring first west of the galapagos and later along the coast the thermostad first reaches maximum development and then a pronounced downwelling of the thermocline occurs rapidly leading to minimum thermostad extent associated wtih this downwelling is an eastward protruding high salinity tongue near the equator which is later seen as an isolated core along the coast at 4 s and 6 s pressure gradients along the equator and the coast inferred from dynamic topography suggest that this pulse is associated with an increase in the flow of the euc and ultimately the peru chile undercurrent the pressure gradient reversal along the equator occurs prior to the annual wind reversal suggesting that remote forcing plays a role in the seasonal pulse of the euc in the eastern pacific

when did the northern apennine become a mountain chain abstract the purpose of the present paper is to bracket the age of the initial uplift of the northern apennine chain by means of all the available evidence the collected data show that the age of the lacustrine or fluvio lacustrine units which have aggraded in the intramontane basins is late pliocene in the northwestern tip of the northern apennine and mostly early pleistocene elsewhere the age of the oldest terraced fluvial deposits showing the initiation of incision is mostly middle pleistocene the uplift of the summit areas of low relief most likely took place during the middle pleistocene it is concluded that the uplift occurring during middle and upper pleistocene caused an area of rather low relief to become the northern apennine mountain chain an eastward shift of the uplift through time is likely

stratigraphical relationships and a revised lithostratigraphical nomenclature for the carboniferous permian and triassic rocks of the offshore east irish sea basin

tertiary extensional tectonics in tuscany northern apennines italy abstract two extensional events have been recognized in the tertiary evolution of tuscany the first event occurred in the period between the late oligocene and late tortonian and caused a stretching of 120 or greater the second event occurred between the late tortonian and quaternary periods and caused a stretching not greater than 10 the first event is characterized by the exhumation of middle crust rocks and therefore by the development of core complexes the most significant structures of the first event are low angle normal faults which characterize the upper plate of the core complexes and ductile shear zones which characterize the lower plate the low angle normal faults tend to die out in the late triassic evaporite level which constitutes the main detachment of the core complexes the main structures of the second extensional event are high angle normal faults which dissect all the previous tectonic features these faults border tectonic depressions which were the site of clastic sedimentation from late tortonian to quaternary time these normal faults may tend to flatten in a seismic lozenge shaped band explained as an active extensional shear zone which is located at the brittle ductile boundary a similar explanation is given for the detachment located in the late triassic evaporite level during the first extensional event while the first extensional event is in the framework of the northern apennine post collisional evolution the second extensional event because it affects an already stretched crust could be attributed to the southern tyrrhenian opening which began during late tortonian

facies architecture and heterogeneity of the fluvial aeolian reservoirs of the sergi formation upper jurassic reconcavo basin ne brazil abstract the sergi formation upper jurassic represents the main hydrocarbon reservoir of the reconcavo basin brazil the basal vertical facies succession of the sergi formation comprises reservoirs formed by a complex fluvio aeolian lacustrine interaction facies architecture and detailed petrophysical analysis of these reservoirs have enhanced the understanding of heterogeneity at a variety of scales and has allowed the development of predictive models that describes the range of styles of mixed fluvial aeolian reservoirs at megascopic scale the reservoirs are predominantly composed of sand bodies deposited by fluvial channel and aeolian facies associations regional flooding surfaces and sequence boundaries are their main flow barriers the regional flooding surfaces are composed of fine grained sediments deposited by lacustrine facies associations and the sequence boundaries act as flow barriers due to mechanically infiltrated clays based on its geometrical relations reservoirs linked to fluvial aeolian lacustrine interaction formed two types of reservoirs at macroscopic scale i with good lateral continuity of aeolian packages and relatively simple stratigraphic correlation and ii of highly compartmentalized aeolian packages with complex stratigraphic correlation and truncation by fluvial deposits mesoscopic heterogeneity reflects lithofacies sedimentary structures and lamina scale variability within aeolian and fluvial facies associations

recurrent deformations of aeolian desert dunes in the cretaceous of the south china block trigger mechanisms variability and implications for aeolian reservoirs abstract deposits of aeolian dunes accumulated in cretaceous intramontane deserts in the south china block underwent recurrent deformation processes affecting their toesets and foreset sediments the mid cretaceous matoushan formation preserves examples of soft sediment deformation deformations associated with theropod tracks in aeolian dune apron sandstones the late cretaceous tangbian formation in the xinjiang basin shows i seismites associated with dry interdune laminated deposits and sand injection into the interdune laminated facies generating intraclast breccias ii mass flow deposits associated with heavy rains generating interbedding of non deformed and deformed intervals in aeolian dune foresets deformed intervals display a variety of deformation styles including thrust duplexes upturned and deformed stratification recumbent folds and microfolds and liquefied intervals covered by overlying draa mega cross bedded sets animal tracks seismites monsoon rains and earthquakes are proposed as the main trigger mechanisms of the failures that led to deformation hydroseismicity associated with monsoon rains is a probable but difficult to prove trigger mechanism this process could be an important deformation agent in the case of large scale deformation recorded in ancient erg sequences mass wasting deposits in ancient erg extensive sandy deserts characterized by aeolian dunes sequences constitute significant heterogeneities for hydrocarbon migration and its architectural variability could determine the development of effective sedimentary traps in aeolian reservoirs

styles of interaction between aeolian fluvial and shallow marine environments in the pennsylvanian to permian lower cutler beds south east utah usa the pennsylvanian to permian lower cutler beds comprise a 200 m thick mixed continental and shallow marine succession that forms part of the paradox foreland basin fill exposed in and around the canyonlands region of south east utah aeolian facies comprise i sets and compound cosets of trough cross bedded dune sandstone dominated by grain flow and translatent wind ripple strata ii interdune strata characterized by sandstone siltstone and mudstone interbeds with wind ripple wavy and horizontal planar laminated strata resulting from accumulation on a range of dry damp or wet substrate types in the flats and hollows between migrating dunes and iii extensive near flat lying wind rippled sandsheet strata fluvial facies comprise channel fill sandstones lag conglomerates and finer grained overbank sheet flood deposits shallow marine facies comprise carbonate ramp limestones tidal sand ridges and bioturbated marine mudstones during episodes of sand sea construction and accumulation compound transverse dunes migrated primarily to the south and south east whereas south westerly flowing fluvial systems periodically punctuated the dune fields from the north east several vertically stacked aeolian sequences are each truncated at their top by regionally extensive surfaces that are associated with abundant calcified rhizoliths and bleaching of the underlying beds these surfaces record the periodic shutdown and deflation of the dune fields to the level of the palaeo water table during episodes of aeolian quiescence fluvial systems became more widespread forming unconfined braid plains that fed sediment to a coastline that lay to the south west and which ran approximately north west to south east for at least 200 km shallow marine systems repeatedly transgressed across the broad low relief coastal plain on at least 10 separate occasions resulting in the systematic preservation of units of marine limestone and calcarenite between units of non marine aeolian and fluvial strata to form a series of depositional cycles the top of the lower cutler beds is defined by a prominent and laterally extensive marine limestone that represents the last major north eastward directed marine transgression into the basin prior to the onset of exclusively non marine sedimentation of the overlying cedar mesa sandstone styles of interaction between aeolian fluvial and marine facies associations occur on two distinct scales and represent the preserved expression of both small scale autocyclic behaviour of competing coeval depositional systems and larger scale allocyclic changes that record system response to longer term interdependent variations in climatic and eustatic controlling mechanisms the architectural relationships and system interactions observed in the lower cutler beds demonstrate that the succession was generated by several cyclical changes in both climate and relative sea level and that these two external controls probably underwent cyclical change in harmony with each other in the paradox basin during late pennsylvanian and permian times this observation supports the hypothesis that both climate and eustasy were interdependent at this time and were probably responding to a glacio eustatic driving mechanism

bounding surfaces in a mixed aeolian fluvial system rotliegend wessex basin sw uk the dawlish sandstone formation is a late permian succession of mixed aeolian and fluvial deposits in the wessex basin sw england it is used to illustrate two contrasting types of fluvial aeolian bounding surface planar and incised planar bounding surfaces separate tabular bodies of fluvial conglomerate and aeolian dune sandstone they were produced primarily by wind scour to groundwater table with the later emplacement of conglomerates resulting in local fluvial erosion of cemented aeolian dune sandstones incised bounding surfaces were produced by fluvial downcutting the erosive relief was infilled with mixed aeolian fluvial deposits the dawlish sandstone formation may provide the first outcrop example of these incised valley fills which have recently been identified as a major component of the subsurface rotliegend in the southern north sea basin the potential variability of aeolian fluvial sedimentary architecture has important implications for well to well correlation and reservoir modelling

mass and hyperconcentrated flow deposits record dune damming and catastrophic breakthrough of ephemeral rivers skeleton coast erg namibia channel shaped deposits of well sorted sand with only 2 4 fine grained material being either massive and structureless or upward fining with basal lag are found interbedded with aeolian sand in the skeleton coast erg namibia detailed analyses of the channel shaped deposits suggest that they are formed as hyperconcentrated flows within the erg grain size analysis and whole rock geochemical modeling revealed that some of the fluvial sediments contain up to 70 aeolian sand interpreted as a result of dune collapse into the fluvial system in certain cases this instantaneous supply of sand resulted in generation of sandy mass flows with laminar flow behaviour the presence of smectite as dominant clay mineral proved to be of crucial importance in formation of mass flow deposits these mass flows had no erosional capacity and drape the palaeotopography they are comparable to those generated by catastrophic collapse of dunes described in the literature this paper suggests that all these deposits should be termed intra erg mass flows as several of them carry little if any debris based on their origin intra erg mass flows can be divided into two groups

nitrogen isotope and productivity variations along the northeast pacific margin over the last 120 kyr surface and subsurface paleoceanography 1 glacial interglacial changes in sedimentary 15n over the last 120 kyr display a remarkably similar pattern in timing and amplitude in core records extending from the denitrification zone in the eastern tropical north pacific etnp where subsurface denitrification is active to the oregon margin where no denitrification occurs today low 15n values 4 6 generally characterize glacial stages 2 and 4 and higher 15n values 7 10 are representative of the holocene millennial scale periods within stage 3 and stage 5 the inferred synchroneity of 15n variations along the entire margin implies that the nitrate isotopic signal produced in the oxygen poor subsurface waters in the etnp is rapidly advected northward and recorded at sites far beyond the boundaries of the modern denitrification zone similar to 15n primary production indicators percent corg ba al and percent opal show glacial interglacial as well as millennial scale variations along the ne pacific margin with higher primary production during warm periods however the relative phasing between 15n and paleoproduction tracers within individual records changes latitudinally whereas 15n and primary production vary approximately synchronously in the midlatitudes production lags 15n in the etnp by several kiloyears this lag calls for a new understanding of the processes driving denitrification in the etnp we suggest that oxygen input by the equatorial undercurrent as well as local organic matter flux controls denitrification rates in the etnp moreover the differences in relative timing point to a time transgressive development of upwelling favorable winds along the ne pacific margin after the last glaciation with those in the north developing several kiloyears earlier

clast lithological analysis edited by d r bridgland quaternary research association cambridge u k 1986 isbn 0 907780 06 7 8 50 207 pp

climatically linked oscillations in arabian sea denitrification over the past 1 m y implications for the marine n cycle water column and core top 15n data show that arabian sea denitrification produces large nitrogen isotopic enrichments that are regionally recorded with fidelity in the sediments these results facilitate interpretation of a 1 m y 15n record for ocean drilling program site 722b on the owen ridge in terms of climatically linked oscillations in denitrification at the major orbital periods as at present denitrification was greatest during interglacial periods and apparently was not active during most glacial intervals cross spectral analysis of 15n with foraminiferal 18o global climate sea level index and lithogenic grain size monsoon strength index suggests forcings by changes in hydrography and productivity acting through the extent and intensity of the oxygen minimum zone the data suggest that denitrification may be an internal forcing mechanism for climate change during major glacial interglacial transitions through influence on marine n inventory and atmospheric co2 however compensation or amplification may occur from other sinks sediment denitrification or sources nitrogen fixation

palaeoenvironments and palaeotectonics of the arid to hyperarid intracontinental latest permian late triassic solway basin u k abstract the late permian to late triassic sediments of the solway basin consist of an originally flat lying laterally persistent and consistent succession of mature dominantly fine grained red clastics laid down in part of a very large intracontinental basin the complete absence of body or trace fossils or palaeosols indicates a very arid hyperarid depositional environment for most of the sediments at the base of the succession thin regolith breccias and sandstones rest unconformably on basement and early permian rift clastics overlying gypsiferous red silty mudstones very fine sandstones and thick gypsum were deposited in either a playa lake or in a hypersaline estuary and their margins these pass upwards into thick bedded multi storied fine to very fine grained red quartzo felspathic and sublithic arenites in which even medium sand is rare despite channels with clay pebbles up to 30 cm in diameter above thick trough cross bedded and parallel laminated fine grained aeolian sandstones deposited in extensive barchanoid dune complexes pass up into very thick multicoloured mudstones and gypsum deposited in marginal marine or lacustrine sabkha environments the latter pass up into marine lower jurassic shales and limestones thirteen non marine clastic lithofacies are arranged into five main lithofacies associations whose facies architecture is reconstructed where possible by analysis of large exposures the five associations can be compared with the desert pavement arid ephemeral stream sabkha saline lake and aeolian sand dune environments of the arid to hyperarid areas of existing intracontinental basins such as lake eyre and lake chad the accommodation space in such basins is controlled by gradual tectonic subsidence moderated by large fluctuations in shallow lake extent caused by climatic change and local variation and this promotes a large scale layer cake stratigraphy as exemplified in the solway basin here the dominant fine grained mature sandstones above the local basal reg breccias suggest water reworking of wind transported sediment as in the northern part of the lake chad basin growth faulting occurs in places in the solway basin caused by underlying evaporite movement but these faults did not significantly affect pre late triassic sedimentation and did not expose pre permian units above the basal breccias there is no evidence of post early permian rifting anywhere during deposition of the late permian to middle triassic british succession although the succession is often interpreted with a rift basin model the arid to hyperarid palaeoclimate changed little during deposition of the solway basin succession in contrast to lakes eyre and chad and this is attributed to tectonic and palaeolatitude stability unlike the later mesozoic cenozoic only limited plate movements took place during the triassic in western europe palaeolatitude changed little and the solway basin remained in the northern latitudinal desert belt from early to mid triassic times however the influence of the early triassic impoverished biota on environmental interpretations needs further study