lower cambrian paleosols from the cantabrian mountains northern spain a comparison with neogene quaternary estuarine analogues abstract the lower cambrian barrios beds cantabrian mountains consist of a siliciclastic succession deposited in deltaic environments punctuated by intertidal and fluvial systems in the barrios de luna area this succession displays a progradational depositional systems tract that contains linkages between upper offshore tidal sand bars fluvial channels and floodplain environments the uppermost fluvial channels are encased within floodplain or interfluvial deposits some of which develop muddy paleosols the detailed micromorphological scanning electron microscopy sem geochemical and mineralogical studies of their pedogenic profiles indicate the presence of three well differentiated horizons fragmentation and shrinking of the upper horizons originated a network of channel like to vuggy porosity occluded by microlaminated clays cyclically emplaced by tidal floods and seasonal oxidation the middle horizons have concretionary to vermicular textures associated with microbioturbation and bacterial colonization and the lower ones are mottled containing numerous preserved lithorelics the barrios sulfidic ustifluvent paleosols represent short time pedogenic events under semiarid subtropical conditions and support previous studies of cambrian microbial life on subaerially exposed microenvironments

sea level reconstruction for turonian sediments from tanzania based on integration of sedimentology microfacies geochemistry and micropaleontology abstract despite many advances in sea level research the nature of cyclic eustatic sea level fluctuations during warm periods without or with much reduced polar ice remains enigmatic recently published 18 o records from extremely well preserved turonian microfossils from tanzania do not support the contentious idea of glacio eustatic control of global sea level changes during the warmest period of the cretaceous for the same locality site tdp 31 we reconstruct relative sea level changes based on sequence stratigraphy and integration of sedimentology microfacies geochemistry and micropaleontology four local sequence boundaries sbs tutz1 4 are recognized at the base middle and top of the helvetoglobotruncana helvetica zone and in the late turonian the lowstands are characterized by increased grain size enhanced organic carbon flux faunal assemblage changes and bulk 13 c org and foraminiferal 13 c f and 18 o f minima strong benthic and planktic foraminiferal turnovers above the top middle turonian sb tutz3 probably reflect shallowing from upper slope to outer shelf and or eutrophication the tdp 31 age model is refined through inter regional comparison of planktic foraminiferal ranges and 13 c records from three other south tethyan localities odp holes 762c and 763b exmouth plateau and the guru section tibet this age model enables correlation of the regressive events at a global scale and suggests that within stratigraphic uncertainty the tdp 31 depositional sequences are synchronous with the global turonian third order sequences and are likely driven by eustasy these correlations together with recent astrochronological and radiometric dating indicate a considerably younger age 91 17 0 52 ma for the top h helvetica zone than currently assumed resulting in zonal duration of 2 35 0 52 myr foraminiferal stable isotope data from tdp 31 indicate slight surface and bottom water warming during the regressions and possibly a minor surface water salinity decrease which is inconsistent with glacio eustatic forcing of turonian third order sea level cycles and is more in line with the model of aquifer eustasy

paleosols of the upper cretaceous lower tertiary maghra el bahari formation in the northeastern portion of the eastern desert egypt their recognition and geological significance the upper cretaceous lower tertiary maghra el bahari formation at gabal ataqa and gabal shabrawet in the northeastern portion of the eastern desert of egypt is subdivided into two informal lithostratigraphic parts lower and upper the lower part has common features of alluvial floodplain dominated deposits with occasional occurrences of crevasse splay deposits the upper part has sediments typical of marginal lacustrine environments both the floodplain and marginal lacustrine deposits exhibit pedogenic features comprising various types of paleosols among other soil forming processes diversity in the paleosols studied is mainly attributed to paleoclimatic and paleohydrologic changes the paleosol criteria suggest two climatic regimes a subhumid semiarid one succeeded by a semiarid arid one the continental depositional environments recognized floodplain and lacustrine with their associated paleosols helped in the recognition of a marine regression in the area studied in a regional perspective comparison of the data presented in this study with paleosol data spanning the same time period in other localities suggests that the proposed paleoclimatic changes may have been of regional extent d 2005 elsevier b v all rights reserved

age and duration of the emeishan flood volcanism sw china geochemistry and shrimp zircon u pb dating of silicic ignimbrites post volcanic xuanwei formation and clay tuff at the chaotian section abstract the age and duration of the emeishan basalts sw china remain poorly constrained largely due to the severe thermo tectonic overprinting of the ar ar system and failure to obtain zircon separates from erupted basalts in an attempt to solve this problem geochemical analyses and shrimp zircon u pb dating have been carried out on rare felsic ignimbrite in the uppermost of the emeishan lava succession the xuanwei formation which immediately overlies the emeishan basalts and a clay tuff at the middle late permian boundary at the chaotian section clastic rocks of the lowermost xuanwei formation group 1 in eastern emeishan large igneous province lip have a geochemical affinity to the emeishan felsic volcanic rocks whereas the overlying sediments group 2 are compositionally more akin to mafic components of the emeishan traps this is the reverse of volcanic sequence of the central emeishan lip where the felsic extrusives sit above predominant mafic rocks it is likely that the clastic rocks are water transported sediments resulting from erosion of the volcanic rocks in the center of the emeishan lip this interpretation is further supported by the general agreement between the age of the lowermost xuanwei formation 257 4 ma 260 5 ma and that of the silicic ignimbrite 263 4 ma and the clay tuff at the middle late permian boundary at chaotian 260 5 ma these ages interpreted as the termination age of the emeishan volcanism are indistinguishable within error from the middle late permian boundary age 260 4 0 4 ma and the main stage 259 262 3 ma of the emeishan volcanism inferred from dating of mafic and alkaline intrusions in the emeishan lip all these suggest that the emplacement of the emeishan volcanism took place over a very short interval moreover the temporal link and geochemical analyses suggest that the chaotian clay at the middle late permian boundary was genetically related to the emeishan silicic volcanism this together with the fact at that both the emeishan basalts and the chaotian clay rest on the maokou formation leads us to infer that the emeishan basalt was emplaced at the middle late permian boundary in this sense the emeishan volcanism can be regarded as a boundary event and its age is presumed at 260 ma although more precise dating is required both stratigraphic correlation and chronologic data presented in this paper lend supports to the notion that the emeishan volcanism was one of likely causes of the end guadalupian mass extinction

the permian moradi formation of northern niger paleosol morphology petrography and mineralogy abstract three basic paleosol morphologies named type a type b and type c are described from the middle upper permian strata of the moradi formation tim mersoi basin northern niger the moradi formation is a typical alluvial redbed succession dominated by red mudrocks with fine to coarse grained pebbly channel sandstones and matrix breccias type a paleosols are hosted by well sorted fine to medium grained trough cross bedded and massive sandstones and preserve abundant vertical to horizontal micritic and microspar calcite tubules interpreted as rhizoliths lateral variability of rhizoliths in type a paleosols and their close association with fluvial channel fill sediments suggests they are the roots of grove stands of phreatophytic vegetation that grew within unstable anabranching stream systems type b paleosols are hosted by mudrocks and preserve well developed ped structure abundant micritic calcite nodules and vertically stacked micritic calcite nodular bodies as well as rare calcite with satin spar texture interpreted as a pseudomorphic replacement of pedogenic gypsum the morphology of type b paleosols suggests they were formed in well drained floodplain deposits on stable landforms type c paleosols are similar to type b but preserve pedogenic structures indicative of soil volume expansion and contraction as well as more abundant stage ii pedogenic carbonate nodules the morphology of type c paleosols suggests that they developed periodically rather than seasonally in poorly drained deposits that nevertheless occupied a relatively stable part of the landscape such as the plains flanking ephemeral lakes or sabkhas x ray diffraction analysis of the the range of morphologies petrographic textures and mineralogy of the paleosol profiles indicates semi arid to hyper arid climatic setting this paleoclimatic reconstruction is in agreement with middle and late permian conceptual paleoclimate models and quantitative general circulation models nevertheless and in spite of an arid climate moradi paleosols and their host strata also indicate a relatively shallow groundwater table importantly this shallow groundwater resource undoubtedly helped to support the moderately diverse fossil vertebrate assemblage and large stature macrophytes preserved in the moradi formation

control of soil acidification by fluvial sedimentation in an estuarine floodplain eastern australia abstract a shallow stratigraphic sequence with associated pyrite induced soil acidification was investigated along a transect from the levee to the backswamp in an estuarine floodplain of eastern australia three sedimentary layers were identified and interpreted to correspond with three depositional stages firstly a layer of humic pyrite rich silty mud was deposited under a saline mangrove inhabited intertidal environment during the present high sea level episode this pyritic layer is buried by the second sedimentary layer of grey brown mud with limited pyrite content that was deposited in a brackish lagoonal environment this material now represents much of the contemporary backswamp surface the third sedimentary layer is a sandy mud without pyrite that has been deposited by freshwater overbank floods it is concluded that fluvial sedimentation has been increasingly important in the development of the stratigraphic sequence controlling the pyrite content thickness and occurrence depth of the pyritic layer the present drainage conditions have allowed oxidation of pyrite in the soils of the backswamp and the resulting acidification has caused elevated concentrations of toxic aluminium that threaten the local environment however in the levee the pyritic layer is covered by thick non pyritic freshwater sediments and low pyritic lagoonal sediments and the soil profiles are unlikely to contribute to any acidification hazard

do red beds indicate paleoclimatic conditions a permian case study abstract terrestrial red beds have long been interpreted as desert deposits by comparison with modern red deserts more recently red beds have been interpreted as evidence of seasonally dry conditions and a permo triassic pangean monsoon red beds of cala viola sardinia are identified as paleosols and used to reconstruct late permian paleoclimatic conditions reconstruction of paleoenvironmental conditions based on the paleosols of the cala viola indicates warm humid conditions with no evidence of dry conditions as in a desert or of extreme seasonality as in a monsoon instead it is suggested that the red color of the paleosols is a result of former good drainage and that red color in general does not indicate specific paleoclimatic conditions

pinning points a method providing quantitative constraints on relative sea level history abstract quantitative constraints on the history of relative sea level allow for a better understanding of the controls on depositional sequence development the constraints are provided by pinning point curves plots of ancient relative sea level elevations pinning points versus time constructing a pinning point curve requires identification of ancient stratigraphic positions of sea level through interpretation of facies and surfaces formed at sea level then their ancient relative elevations are determined through reconstructing aspects of ancient paleotopography upper miocene strata from las negras southeastern spain preserve paleotopography contain ancient surfaces of subaerial exposure and contain facies deposited near sea level the pinning point curve illustrates a complex relative sea level history with large and small scale relative sea level fluctuations defined by 31 pinning points

quaternary subsurface paleosols in haifa bay israel a new perspective on stratigraphic correlations in coastal settings abstract this study presents the first in depth analysis of properties micromorphology clay mineralogy magnetic susceptibility and general properties of quaternary paleosols from two boreholes in haifa bay subsurface whose chronostratigraphic position was determined previously the current analytical results allowed us to identify the type hydrologic regime polygenesis mode of pedosedimentary evolution and some subsequent alterations of paleosols the analogs of polygenic haplo and rhodo xeralf soils brown mollic and ortho hamra are associated with marine isotope stages mis 3 1 5 4 6 and 8 0 or 7 4 and likely developed in response to a changing climate paleosols prior to mis 12 yet difficult to attribute to specific mis are distinct from hamra soils by striking mottling poor preservation of argillic horizons abundant deformations in microfabric and overprinting processes of gley and calcium carbonate accumulation it is assumed that calcification may have affected the earlier formed clay illuviation and amorphous features and was related with marine coastal groundwater interface the older calcic gleyed paleosols of earlier middle pleistocene likely indicate that coastal paleogeography was characterized by both high discharge of the ancient qishon river and a high water table the thin section micromorphology is particularly valuable for refined paleopedological taxonomy identified pleistocene paleosols including their type hydrology and mode of evolution are proposed to serve additional stratigraphic markers in coastal settings

north and south china collision along the eastern and southern north china margins abstract lithofacies distribution and petrography and intracontinental deformation in the north china block ncb and the south china block scb show an active continental margin flanked by the eastern ncb and a passive continental margin was present along the west side of the scb both margins initially trending n ne the tanlu fault possibly initiated as part of the subduction zone during paleozoic time along the eastern margin on the ncb the ncb and the scb were divided along the eastern southern north china margin by the qinling dabie tanlu sulu imjingang yanji zone from southwest to northeast these two continental blocks made contact first in the northeast during late early permian time finally in the southeast at late triassic time and the clockwise collision probably lasted to middle jurassic time the eastern suture the yanji imjingang sulu tanlu zone was dominated by contractional deformation the southern suture the qinling dabie zone was a transpression belt dominated by right lateral strike slip

facies analysis and sea level change at the guadalupian lopingian global stratotype laibin south china and its bearing on the end guadalupian mass extinction abstract the guadalupian lopingian boundary stratotype at penglaitan and the nearby tieqiao section near laibin south china record a series of major environmental changes within the jiangnan basin during a mid permian biotic crisis the sequence stratigraphic petrographic and palaeontological record of these sections has been studied and the associated strontium isotopic fluctuations have been assayed mass extinction of fusulinid foraminifers is most clearly associated in time with onset of volcanism and a relative sea level fall that led to the establishment of mid ramp conditions laibin limestone in settings that were previously dominated by radiolarian mudstones the regression also coincides with a low point of 87 sr 86 sr ratios the lowstand deposits contain mafic scoriaceous grains that record pyroclastic volcanism probably centred in the emeishan flood basalt province 800 km to the west of laibin thus unusually violent eruptions associated with flood basalts in this province may have contributed to the environmental stresses responsible for the extinction event subsequent environmental changes included transgression spread of dysoxic waters indicated by populations of small pyrite framboids and a major negative c isotope excursion all these phenomena have been previously related to the end guadalupian extinction but they in fact post date the crisis because a post extinction fauna of foraminifers is encountered at this time

salt marsh aggradation in response to late holocene sea level rise at amherst point nova scotia canada a radiocarbon 14c chronology determined for plant macrofossils in exposed salt marsh sediments at amherst point nova scotia canada shows that the edge of the high salt marsh aggraded 7 5 m since 900 bc equivalent to a mean rate of 25 9 cm 100 yr 1 four phases of rapid aggradation 900 600 bc 100 bc ad 200 ad 700 1100 and ad 1600 to present were interspersed with three phases of slower aggradation 600 100 bc ad 200 700 and tentatively ad 1100 1600 the stepped pattern of marsh aggradation probably resulted from eustatic sea level fluctuations superimposed on background signals of crustal subsidence and tidal range expansion because the rate of high salt marsh aggradation lagged or exceeded the rate of higher high water hhw increase at various times the high salt marsh aggradation trend only approximates the trend of hhw increase the eustatic sea level fluctuations are estimated to have a range of at least 0 8 m

morphology and distribution of fossil soils in the permo pennsylvanian wichita and bowie groups north central texas usa implications for western equatorial pangean palaeoclimate during icehouse greenhouse transition analysis of stacked permo pennsylvanian palaeosols from north central texas documents the influence of palaeolandscape position on pedogenesis in aggradational depositional settings palaeosols of the eastern shelf of the midland basin exhibit stratigraphic trends in the distribution of soil horizons structure rooting density clay mineralogy and colour that record long term changes in soil forming conditions driven by both local processes and regional climate palaeosols similar to modern histosols ultisols vertisols inceptisols and entisols all bearing morphological mineralogical and chemical characteristics consistent with a tropical humid climate represent the late pennsylvanian suite of palaeosol orders palaeosols similar to modern alfisols vertisols inceptisols aridisols and entisols preserve characteristics indicative of a drier and seasonal tropical climate throughout the lower permian strata the changes in palaeosol morphology are interpreted as being a result of an overall climatic trend from relatively humid and tropical moist conditions characterized by high rainfall in the late pennsylvanian to progressively drier semi arid to arid tropical climate characterized by seasonal rainfall in early permian time based on known late palaeozoic palaeogeography and current hypotheses for atmospheric circulation over western equatorial pangea the pennsylvanian palaeosols in this study may be recording a climate that is the result of an orographic control over regionalscale atmospheric circulation the trend towards a drier climate interpreted from the permian palaeosols may be recording the breakdown of this preexisting orographic effect and the onset of a monsoonal atmospheric circulation system over this region

microbial carbonates as contributors to upper permian guadalupian lopingian biostromes and reefs in carbonate platform margin setting ziyun county south china permian guadalupian and lopingian reefs in ziyun county southern guizhou southwestern china occur in a carbonate platform margin setting guadalupian reefs maokouan are characterized by sponges calcimicrobes microbialites as microencrusters and syndepositional calcite cement global sea level falling in the latest guadalupian changed the reef biotopes lower lopingian wuchiapingian deposits reflect a rapid transgressive regressive cycle reefs were not developed during that time although coral biostromes are common however microbial carbonates occur commonly in these biostromes including dark coloured homogeneous microbialite free growing microbes shamovella and archaeolithoporella interpreted to be problematic microbial deposits upper lopingian changhsingian reefs were formed by sponges microbialites shamovella archaeolithoporella automicrite and syndepositional calcite cement common primary encrustations consist of thin homogeneous subparallel layers of archaeolithoporella which is an important reef builder particularly throughout the lopingian reef succession secondary encrustations are characterized by dark coloured homogeneous microbialite containing thin thalli that alternate with light coloured microspar pseudospar reef building organisms e g sponges archaeolithoporella calcimicrobes and hydrozoans were bound lithified and preserved by syndepositional calcite cement and microbially precipitated micrite automicrite in changhsingian reefs of the shitouzhai limestone microbial carbonate e g micritic peloidal crusts and automicrite layers encrusted the top sides and undersides of in situ organisms and also grew on their upper surface as thick accumulations radiaxial fibrous calcite cement is present but is not common abundant microbial carbonates in the guadalupian to lopingian reefs in ziyun indicate that microbial precipitation of calcium carbonate played a vital role in the development of permian reefs in this platform margin setting c 2004 elsevier b v all rights reserved

precise age determination of mafic and felsic intrusive rocks from the permian emeishan large igneous province sw china abstract radiogenic isotopic dating using different mainly micro beam analyses techniques of rocks from the emeishan large igneous province elip has yielded a range of ages from the capitanian to the early triassic in contrast estimates based on paleontological and paleomagnetic data suggest the elip was emplaced rapidly 2 ma and that volcanism ended by 257 ma new zircon ca tims u pb ages that have superior precision compared to ages from micro beam analyses were obtained from strategic intrusive rocks of the panxi region inner zone of the elip the huangcao 258 9 0 7 ma daheishan 259 1 0 5 ma woshui 259 6 0 5 ma and cida 258 4 0 6 ma syenitic and granitic plutons and three mafic dykes 259 2 0 4 ma 259 5 0 8 ma 257 6 0 5 ma yielded a narrow range of ages between 257 ma and 260 ma the new results are consistent with the estimates from magneto biostratigraphic data and a rapid emplacement model the new wuchiapinqian ages of the huangcao and daheishan plutons suggests that magmatism may have lasted significantly less than 10 ma as previously suggested and the precise ages of the mafic dykes refute the hypothesis that emeishan high ti basalts represent the waning stages of the elip magmatism the short duration of magmatism also implies that degassing of the host sediments mostly carbonates and thus releasing of greenhouse gasses occurred within a substantially shorter interval than previously thought which significantly changes the loading of atmosphere per time unit the latter corollary potentially has severe environmental effects that may have contributed to causing the end guadalupian mass extinction

a temporal link between the emeishan large igneous province sw china and the end guadalupian mass extinction abstract previous studies have suggested that there were two mass extinction events in the late permian one that occurred at the permo triassic p t boundary 251 ma and a second smaller mass extinction that occurred 5 8 myr earlier at the end of the guadalupian many workers have argued that there is a causal relationship between large scale volcanic activity and mass extinctions the major mass extinction event at the p t boundary coincides with the outpouring of huge quantities of lava that formed the siberian flood basalt province in russia courtillot et al earth planet sci lett 166 1999 177 195 and wignall earth sci rev 53 2001 1 33 suggested that the earlier late permian mass extinction coincided with the eruption of the lavas that formed the emeishan flood basalt efb province in sw china however the age of eruption of the efb lavas is poorly constrained using the sensitive high resolution ion microprobe to analyze zircons we have established the age of the xinjie intrusion believed to be a feeder to the main phase of efb volcanism to be 259 3 ma hence the formation of the efb is coincident with a proposed extinction event at 256 259 ma this result supports a temporal link between the emeishan large igneous province and the end guadalupian mass extinction

illawarra reversal the fingerprint of a superplume that triggered pangean breakup and the end guadalupian permian mass extinction abstract the permian magnetostratigraphic record demonstrates that a remarkable change in geomagnetism occurred in the late guadalupian middle permian ca 265 ma from the long term stable kiaman reverse superchron throughout the late carboniferous and early middle permian to the permian triassic mixed superchron with frequent polarity changes in the late permian and triassic this unique episode called the illawarra reversal probably reflects a significant change in the geodynamo in the outer core of the planet after a 50 million years of stable geomagnetism the illawarra reversal was likely led by the appearance of a thermal instability at the 2900 km deep core mantle boundary in connection with mantle superplume activity the illawarra reversal and the guadalupian lopingian boundary event record the significant transition processes from the paleozoic to mesozoic modern world one of the major global environmental changes in the phanerozoic occurred almost simultaneously in the latest guadalupian as recorded in 1 mass extinction 2 ocean redox change 3 sharp isotopic excursions c and sr 4 sea level drop and 5 plume related volcanism in addition to the claimed possible links between the above listed environmental changes and mantle superplume activity i propose here an extra explanation that a change in the core s geodynamo may have played an important role in determining the course of the earth s surface climate and biotic extinction evolution when a superplume is launched from the core mantle boundary the resultant thermal instability makes the geodynamo s dipole of the outer core unstable and lowers the geomagnetic intensity being modulated by the geo and heliomagnetism the galactic cosmic ray flux into the earth s atmosphere changes with time the more cosmic rays penetrate through the atmosphere the more clouds develop to increase the albedo thus enhancing cooling of the earth s surface the illawarra reversal the kamura cooling event and other unique geologic phenomena in the late guadalupian are all concordantly explained as consequences of the superplume activity that initially triggered the breakup of pangea the secular change in cosmic radiation may explain not only the extinction related global climatic changes in the end guadalupian but also the long term global warming cooling trend in earth s history in terms of cloud coverage over the planet

permian palaeogeographic evolution of the jiangnan basin south china abstract the most striking geographic feature of the permian of south china is the jiangnan basin which intimately reflects the interplay between the yangtze and cathaysia blocks geographic and sedimentological evolution suggests that the jiangnan basin superposed on a precambrian collisonial megasuture and a folded early paleozoic deep basin was an extensional intracratonic basin it opened in the longlinian and became more passive and restricted in the latest maokouan the remarkably similar geographic patterns of the jiangnan basin in the early and late palaeozoic suggest that the yangtze and cathaysia blocks were coherent during the paleozoic

micromorphology of calcitic features in highly calcareous soils of fars province southern iran abstract the micromorphology of calcitic pedofeatures in highly calcareous arid and semiarid soils of the fars province southern iran has been studied in order to determine their genesis and distribution in different climatic regions available soil moisture soil temperature soil texture vegetation and availability of calcium carbonate are amongst the main factors determining the type and morphology of calcitic features size and frequency of microcrystalline calcite nodules and coatings increase from aridic to xeric but decrease again towards the areas with a ustic moisture regime cytomorphic and acicular calcite are observed mainly in areas with an ustic moisture regime and a denser vegetative growth but rarely in xeric areas layered pendents of calcite are common beneath coarser fragments but are considered as relicts of a more humid paleoclimate calcite depletion pedofeatures are observed in xeric mesic areas with higher available soil moisture ultraviolet uv violet vl and blue light bl fluorescence and cathodoluminescence cl studies proved to be useful in differentiating in this region pedogenic from geogenic calcite all types of pedogenic calcite were uv and bl fluorescent but didn t show cl whereas limestone fragments showed cl but no uv bl fluorescence the absence of cl in the studied pedogenic calcite samples is suggested to be related to the oxidative environment hindering mobilisation of mn

geochemistry and partitioning of trace metals in acid sulphate soils in sweden and finland before and after sulphide oxidation abstract acid sulphate soils ass are formed on sulphidic sediments along the baltic coasts of sweden and finland the sulphides in the fine grained sediments were once formed in an anoxic environment some centimetres below an oxic sediment water interface in earlier investigations high concentrations of many trace elements have been observed in streams draining such areas we compared the trace element contents in soils formed in sulphidic and non sulphidic clays the results show that the total contents of cd ni mn co and cu in the sulphidic sediments are not higher than in non sulphidic clays from adjacent areas however the mobilisation of cd and ni is higher from acid sulphate soils than from soils formed on sulphide free clays to understand the processes causing the mobilisation we studied the partitioning of trace metals before and after oxidation of sulphidic sediments cadmium ni mn co zn and to some extent cu were found to be mobilised from acid sulphate soils due to increased weathering caused by the low ph in these soils iron and cr are only mobilised to a limited extent copper mo and fe mobilised from weathering are precipitated in oxides that form in the oxidised bg horizons nickel co mn mo and cu were shown to be partly bound in pyrite and are mobilised from acid sulphate soils during the pyrite oxidation however mobilisation of trace elements from pyrite was not found to be an important quantitative contributor to trace element leaching any elements that are mobilised are likely to be transported down through the characteristic cracks which occur frequently in the oxidised horizons evidence of this was found at the groundwater table where the most easily extractable fraction of mobilisable elements occurred at higher concentrations

mass extinctions and sea level changes abstract review of sea level changes during the big five mass extinctions and several lesser extinction events reveals that the majority coincide with large eustatic inflexions the degree of certainty with which these eustatic oscillations are known varies considerably thus the late ordovician and end cretaceous extinctions are associated with unequivocal major regressions demonstrated from numerous widespread regions in contrast the multiple high frequency sea level changes reported for the frasnian famennian crisis based on the supposed depth preferences of conodont taxa have little support from sequence stratigraphic analyses which reveals the interval to be one of highstand the end permian mass extinction has long been related to a severe first order lowstand of sea level newell n d 1967 revolutions in the history of life geol soc am spec pap 89 63 91 based primarily on the widespread absence of latest permian ammonoid markers but field evidence reveals that the interval coincides with a major transgression newell s hypothesis that marine extinctions are related to shelf habitat loss during severe regression remains tenable for the end guadalupian and end triassic extinction events but not for other crises rapid high amplitude regressive transgressive couplets are the most frequently observed eustatic changes at times of mass extinction with the majority of extinctions occurring during the transgressive pulse when anoxic bottom waters often became extensive the ultimate cause of the sea level changes is generally unclear a glacioeustatic driving mechanism can only be convincingly demonstrated for the end ordovician and end devonian events at other times it is speculated that they may relate to the widespread regional doming and subsequent collapse caused by the impingement of superplumes and ultimate eruption on the base of the lithosphere

development of potential acid sulfate paleosols in paleocene floodplains bighorn basin wyoming usa abstract floodplain paleosols in the paleocene fort union formation in the bighorn basin are distinguished by a dark claystone interval with yellow jarosite mottles relatively high total organic carbon values and woody debris and leaves along bedding planes the paleosols also have various redoximorphic features including low matrix chromas grey root mottles and local concentrations of goethite and hematite especially associated with roots and other organic matter jarosite is usually an oxidation product of pyrite which forms under waterlogged conditions when sulfate and organic matter are available the former presence of pyrite and the redoximorphic features suggest that the fort union paleosols first developed as potential acid sulfate soils brinkman and pons 1973 the dark claystones with jarosite are interpreted as permanently reduced or gr horizons the gr horizon is overlain by mudstone that is lighter colored and lacks jarosite this represents an ancient bg horizon or a bg sequence the jarosite indicates that the paleosols underwent a subsequent episode of oxidation and acidification those processes require that the soils be drained which probably did not occur during paleocene time and may be a recent event rather the soils were probably buried as the fort union formation continued to aggrade and the waterlogged soils were pushed even farther below the groundwater table only with late cenozoic excavation of strata in the basin and exposure of the fort union deposits did jarosite precipitate pedogenic and paleobotanical features suggest that the soils formed in floodplain swamps dominated by coniferous trees the high organic content and clay rich nature of the gr horizons suggest that the floodplain swamps were not close to the active channel the bipartite nature to the profiles bg horizon or a bg sequence above a gr horizon probably resulted from two different kinds of floodplain deposition grain size trends indicate that the gr horizons formed on sediment deposited by overbank flooding the impermeable fine grained sediment and its low topographic position led to waterlogging the overlying a bg or bg horizons formed on coarser sediment that was probably deposited during channel avulsion the greater permeability and higher topographic position of this sediment caused it to be better drained than the gr horizon the paleosols are unusual because they formed in a freshwater setting whereas modern potential acid sulfate or acid sulfate soils form in coastal areas where sulfate is readily available the source of the sulfate may have been cretaceous marine shales exposed along the flanks of mountains rising around the bighorn basin during paleocene time other upper cretaceous and paleocene formations in the rocky mountain area contain similar rocks suggesting that sulfidic soils were relatively common in the mid continent at this time most of these other examples probably reflect deposition associated with the retreating western interior seaway and humid climates

late cretaceous to early paleocene climate and sea level fluctuations the tunisian record abstract climate and sea level fluctuations across the cretaceous tertiary k t transition in tunisia were examined based on bulk rock and clay mineralogies biostratigraphy and lithology in five sections el melah el kef elles ain settara and seldja spanning from open marine to shallow inner neritic environments late campanian to early danian trends examined at el kef and elles indicate an increasingly more humid climate associated with sea level fluctuations and increased detrital influx that culminates at the k t transition this long term trend in increasing humidity and runoff in the tethys region is associated with middle and high latitude cooling results of short term changes across the k t transition indicate a sea level lowstand in the latest maastrichtian about 25 100 ka below the k t boundary with the regression marked by increased detrital influx at el kef and elles and a short hiatus at ain settara a rising sea level at the end of the maastrichtian is expressed at elles and el kef by deposition of a foraminiferal packstone a flooding surface and condensed sedimentation mark the k t boundary clay which is rich in terrestrial organic matter the p0 p1a transition is marked by a sea level lowstand corresponding to a short hiatus at ain settara where most of p0 is missing and a period of non deposition and erosion in the lower part of p1a 64 95 ma at seldja p0 and possibly the topmost part of cf1 are missing these sea level fluctuations are associated with maximum humidity these data suggest that in tunisia long term environmental stresses during the last 500 ka before the k t boundary and continuing into the early danian are primarily related to climate and sea level fluctuations within this long term climatic trend the pronounced warm and humid event within the latest maastrichtian zone cf1 may be linked to greenhouse conditions induced by deccan volcanism the absence of any significant clay mineral variations at or near the k t boundary and ir anomaly suggests that the bolide impact had a relatively incidental short term effect on climate in the tethys region

micromorphology and formation of pedogenic ooids in calcic soils and petrocalcic horizons abstract ooids pisoids nodules concretions and a host of other terms are used to describe concentrically zoned pedogenic carbonate phyllosilicates silica and other minerals in calcic and petrocalcic horizons worldwide the pedogenic and paleoenvironmental significance of such features is not always easy to interpret because variations in size structure composition and soil geomorphic context have been used to infer distinct modes of genesis for features that appear similar using both optical and scanning electron microscopy petrocalcic soil samples from the jornada la mesa geomorphic surface in new mexico and the mormon mesa geomorphic surface in nevada were studied to reconsider the formation of pedogenic ooids in this paper ooids are 2 mm in diameter and have a range of internal morphologies ooids were especially common within features including clast pendant laminae pisoids and laminar horizons or laminar horizon caps we propose a possible new mode of ooid genesis suggesting that crystal growth can move ooids tiny incremental distances over time and that phyllosilicates are an important genetic component ooids are interpreted to form via 1 mineralization during the evaporation of solutions held by surface tension around mineral grains clasts or petrocalcic fragments with or without the presence of organic matter 2 hydration and plastic behavior of pervasive pedogenic fibrous phyllosilicates that co precipitate with pedogenic calcite and 3 tiny successive movements caused by the crystallization pressure of pedogenic carbonate and other minerals during soil solution evaporation spheroidal morphology is initially promoted by chemical precipitation from evaporating solutions around grains next crystallization pressures from the surrounding matrix displace grains non uniformly promoting stochastic contacts or knocking of ooids against one another and against the soil matrix over long time spans this micrometer scale episodic translocation and rotation in tandem with the plastic behavior of fibrous phyllosilicates enhances the spherical shape of ooids the model described here does not preclude possible biological contributions to ooid genesis nor refute the role of other processes in producing similar features in the same soil finally ooid size is limited by physical and hydrological thresholds pisoids as larger features are more complex and are more likely to involve erosion they do not form in the same manner as ooids this study has implications for paleoenvironmental interpretations of calcic and petrocalcic horizons and for the selection of pedogenic features for isotopic analysis

changes in coiling direction of cibicidoides pseudoacutus nakkady across the cretaceous tertiary boundary of tunisia palaeoecological and biostratigraphic implications abstract the analysis of coiling direction preference in the benthic foraminifera cibicidoides pseudoacutus nakkady has been carried out across the cretaceous tertiary boundary k t boundary from four tunisian sections representing a palaeobathymetric transect from a middle outer neritic to lower upper bathyal depositional setting our study reveals that c pseudoacutus developed a preference for sinistral coiling in a short time period during the lowermost danian the comparison of the coiling ratio number of sinistral vs dextral individuals record with isotope data and dinoflagellate cyst assemblage distribution suggests that the development of sinistrally coiled populations of cibicidoides pseudoacutus might be related to a short term cooling of both surface and bottom waters which occurred at the k t boundary and lasted for some 7 kyr the continuous occurrence and the high abundance of cibicidoides pseudoacutus through the k t boundary in neritic to upper bathyal depositional environments around southern tethys make identification of the shift in its coiling ratio relatively easy the development of a sinistrally coiled population in this benthic foraminiferal species is regarded as a potential marker for the base of planktonic foraminiferal zone p0 in tethyan shallow water settings

oxygen and hydrogen isotope compositions of permian pedogenic phyllosilicates development of modern surface domain arrays and implications for paleotemperature reconstructions abstract mineralogic chemical and oxygen and hydrogen isotope compositions of 15 different phyllosilicate samples from permo pennsylvanian age paleosols of the eastern shelf of the midland basin of texas and the southern anadarko basin are presented mixtures of 2 1 phyllosilicates and kaolinite dominate most samples although some samples consist of relatively pure 2 1 phyllosilicates chemical and mineralogic data are used in conjunction with published thermodynamic data to calculate hydrogen and oxygen isotope fractionation factors for each sample in turn application of measured oxygen and hydrogen isotope compositions of the phyllosilicates to temperature dependent fractionation equations are used to calculate paleotemperatures of crystallization the d values of the phyllosilicates range from 69 to 55 the 18 o values range from 19 5 to 22 7 if these samples preserve a record of equilibrium with paleo meteoric waters the isotopic compositions of the phyllosilicates correspond to paleotemperatures of phyllosilicate crystallization ranging from 22 3 c to 35 3 c in particular the stratigraphic trend of calculated temperatures from midland basin samples suggests that early permian surface temperatures may have been up to 10 c warmer than those of the latest pennsylvanian

emeishan basalt ar ar overprint ages define several tectonic events that affected the western yangtze platform in the mesozoic and cenozoic abstract ar ar whole rock dating was carried out as part of a detailed stratigraphical investigation of the emeishan basalt large igneous province lip in the stratotype area sichuan china thirteen from twenty one specimens from three sections yielded reliable reversed isochron and plateau ages maximum 1 errors of 2 1 and 1 6 m y respectively and form two clusters centered on the late jurassic early cretaceous and early late cretaceous with a tail spanning 82 40 ma however all are appreciably younger than the magnetobiostratigraphically constrained late middle permian 255 260 ma age of the basalts reflecting varying degrees of thermal resetting during the mesozoic and cenozoic recently middle jurassic early cretaceous ages reported from elsewhere in the lip have been used to infer a single 40 m y long tectonic episode that affected the western yangtze platform developing this idea the new information have been combined with data we hold for other parts of the terrain and results from three emeishan lip ar ar dating studies published during 2002 to give 32 reliable age dates three 10 12 m y events appear to be recorded in different parts of the province middle jurassic late jurassic early cretaceous and early late cretaceous with a fourth shorter middle eocene episode the 40 m y mesozoic episode appears to be a sampling artifact following a review of the regional deformation tectonic features it is argued that activity related to various phases of deformation in the longmen shan thrust belt is the most likely cause of resetting the final suturing of the north and south china blocks may have also been responsible for the middle jurassic event however the oligocene present indentation of india into asia appears not to have had an impact possibly due to the large scale related strike slip faults that have effectively shielded the lip sichuan basin

a world perspective on acid sulphate soils abstract generalizations about the morphology and genesis of acid sulphate soils at a regional scale are derived from a review of extensive though patchy soil survey data a general sequence of sedimentation accumulation of sulphides and burial of sulphitic material by peat or alluvium of low sulphide content and a parallel sequence of soil profile development are illustrated by examples of unripe sulphitic soils under a natural tidal regime artificially drained raw acid sulphate soils and ripe acid sulphate soils at various stages of development the world pattern has been driven mainly by postglacial sea level change but each regional pattern is determined by its unique sedimentary and geomorphological history distinctive patterns occur in deltas and estuaries and in humid and seasonally dry climates very extensive areas of ripe acid sulphate soils in areas that are not known to have experienced falls in relative sea level are ascribed to human activity forest clearance and soil erosion in catchments causing lower dry season river flows and piecemeal clearance of peat over the floodplains permitting the dry season water table to fall the implications for further agricultural development in other comparable areas include the absolute necessity to know the extent of potential acid sulphate soils and to maintain their water table above the sulphide datum most effective systems of management have been developed by farmers themselves but the sustainability of these systems is often doubtful due to their detrimental effects on the aquatic ecosystem

end guadalupian extinction of the permian gigantic bivalve alatoconchidae end of gigantism in tropical seas by cooling abstract the unique permian bivalve family alatoconchidae has aberrant shell forms and extraordinary size up to 1 m representing the largest bivalve group in the paleozoic their occurrence is reported sporadically from lower middle permian shallow marine carbonates in 9 areas in the world tunisia croatia oman iran afghanistan thailand malaysia the philippines and japan that cover low latitudes of both the tethyan and panthalassan domains alatoconchids almost always occurred in close association with large tested fusulines verbeekinidae and or rugose corals waagenophyllidae of the typical tethyan assemblage suggesting their preferential adaptation to shallow warm water tropical environments this tropical trio alatoconchidae verbeekinidae and waagenophyllidae became extinct either during the late guadalupian or around the guadalupian lopingian boundary g lb their intimate association and occurrence range suggest that these 3 taxonomically distinct clades may have shared not only a common habit but also a common cause of extinction the shell structure of alatoconchids suggests their symbiosis with photosynthetic organisms algae cyanobacteria in order to maintain their large body size that required high energy consuming metabolism in contrast to smaller forms the alatoconchidae attained their largest size in the wordian middle guadalupian probably maximizing the benefits of photosymbiosis the subsequent extinction of the warm water adapted tropical trio both in tethys and panthalassa positively supports the explanation that a critical cooling took place on a global scale including low latitude oceans the end of the gigantism in fusulines and bivalves in the capitanian late guadalupian was likely caused by the collapse of photosymbiotic systems during a temporary temperature drop of seawater kamura cooling event coupled with eutrophication that was detrimental to the tropical fauna adapted particularly to oligotrophic conditions gigantism of bivalves occurred several times in the phanerozoic e g siluro devonian permian triassic early jurassic and jurassic creataceous mostly in warm periods the sea level change in the phanerozoic apparently synchronized with the intermittent rise and decline of bivalve gigantism suggesting that the photosymbiosis related gigantism in low latitudes may serve as a potential monitor of global warming cooling in the past

trace elements stable isotopes and clay mineralogy of the elles ii k t boundary section in tunisia indications for sea level fluctuations and primary productivity abstract trace elements and stable isotopes in bulk rocks and foraminifera bulk rock and clay mineral compositions are used as palaeoproxies to evaluate sea level fluctuations climatic changes and variations in primary productivity across the k t transition at elles ii in tunisia from 1 m 33 kyr below to 1 m 70 kyr above the k t boundary results on clay minerals major and trace elements stable isotopes in bulk rock samples e g ca cu zn rb sr zr ba 13c and 18o and in foraminifera sr ca 13c 18o indicate that the latest maastrichtian last 33 kyr in tunisia was marked by a relatively warm but humid climate and a rising sea level the transgressive surface is marked by deposition of a foraminiferal packstone just below the k t boundary followed by maximum flooding across the k t boundary red layer and black clay layer humid warm conditions accompanied the maximum flooding along with increased total organic carbon values and rapidly decreasing primary productivity at the k t boundary an impact event ir anomaly ni rich spinels spherules exacerbated already stressed environmental conditions leading to the mass extinction of tropical planktic foraminifera increasingly more humid conditions prevailed within the lowermost danian zone p0 50 kyr culminating in a sea level lowstand near the top of p0 a slow recovery of the ecosystem in zone p1a coincided with a rising sea level and gradually less humid climatic conditions

giant gas discovery in the precambrian deeply buried reservoirs in the sichuan basin china implications for gas exploration in old cratonic basins abstract an estimated trillions of cubic meters of natural gas have recently been discovered in the sinian dolomite reservoirs in the sichuan basin china the 20 26 m thick reservoirs were found in deep structural lithologic traps of 5000 5500 m deep the sinian gas is thought to have been derived mainly from the sinian source rocks and partly from the cambrian source rocks the gas is thermally matured with a dryness ratio c1 c1 4 of 0 997 0 9998 c2h6 content

coral reef response to quaternary sea level and environmental changes state of the science there is considerable uncertainty about future sea level projections due to the current poor understanding of the vulnerability and sensitivity of ice sheets to global warming fossil coral reefs represent a unique archive of sea level and associated environmental changes that extend far beyond instrumental records here recent advances in this field are summarized focusing on periods of earth history typified by rapid sea level rise and short term climate excursions sea level and reef response records from the last deglaciation and periods characterized by higher sea level stands and short term and low magnitude sea level oscillations such as the mid to late holocene and the last interglacial are synthesised special emphasis is given to understanding how coral reefs have responded to these changes in terms of reef development architecture and composition finally seven major challenges and future research directions are identified

paleosols trace fossils and precipitation estimates of the uppermost triassic strata in northern new mexico abstract this study provides a detailed pedogenic evaluation of two upper triassic late norian through rhaetian stratigraphic intervals in new mexico in order to assess the climate and ecology of the latest triassic which ended in a mass extinction the two study areas are located in north central and east central new mexico and are separated by 200 km each section contains abundant paleosols of varying maturity with features that reflect an arid to semiarid climate there is little pedogenic variation throughout the strata at each location and a typical paleosol profile is about 1 m thick and has an ab bw bk bc horizon succession bkm bss bssk or bssg horizons are present in some paleosols micromorphological features suggest dominantly well drained sola e g abundant carbonate nodules illuviated clay with minor periods of moist or saturated conditions e g femn concretions femn coatings and hypocoatings sepic plasmic fabrics trace fossils are abundant in these strata and are dominated by taenidium serpentinum and root traces depth to carbonate functions estimate that mean annual precipitation was between 200 and 450 95 mm relative to location 1 eastern new mexico location 2 north central new mexico produced higher paleo precipitation estimates and has stronger and more abundant sepic plasmic fabrics in thin sections the presence of a gleyed paleosol camborygma eumnkenomos and slickensides at location 2 also suggests conditions wetter than at location 1 taxonomically all of the paleosols in this study appear to be entisols or aridisols and can be grouped into seven representative pedotypes of varying maturity by comparing these paleosols to modern soils this study demonstrates that the late triassic western interior during the late norian to rhaetian was arid to semiarid and supported a desert shrub environment that had localized and periodic moist or saturated soil conditions

δ13c depth profiles from paleosols across the permian triassic boundary evidence for methane release stable carbon isotopic analyses of organic carbon 13 c in individual paleosol profiles from permian triassic sequences of antarctica reveal systematic isotopic variations with profile depth these variations are in many cases analogous to those in modern soils which are functions of redox conditions soil development and degree and type of microbial decay in modern soils these isotopic depth functions develop independently from vegetation changes c 3 versus c 4 vegetation and can be diagnostic of soil orders this study shows that soil intrinsic functions can be preserved in the 13 c values of paleosols as old as 260 ma and constitute valuable data for paleoecological interpretations a large carbon isotopic offset of as much as 10 in whole paleosol profiles across the permian triassic boundary indicates significant changes in the soil biogeochemistry and the soil atmosphere system early triassic paleosols are distinctive in their extremely low 13 c values to 42 and often show an anomalous 13 c depth distribution compared to both permian paleosols and modern soils highly depleted 13 c values as the ones in early triassic paleosols are suggested to be associated with microbial methane oxidation methanotrophy this hypothesis implies increased methane concentrations in the early triassic soil atmosphere system increased atmospheric methane was probably partly responsible for the global carbon isotopic shift documented in marine and terrestrial sediments across the permian triassic boundary

a chronology of paleozoic sea level changes sea levels have been determined for most of the paleozoic era 542 to 251 million years ago but an integrated history of sea levels has remained unrealized we reconstructed a history of sea level fluctuations for the entire paleozoic by using stratigraphic sections from pericratonic and cratonic basins evaluation of the timing and amplitude of individual sea level events reveals that the magnitude of change is the most problematic to estimate accurately the long term sea level shows a gradual rise through the cambrian reaching a zenith in the late ordovician then a short lived but prominent withdrawal in response to hirnantian glaciation subsequent but decreasingly substantial eustatic highs occurred in the mid silurian near the middle late devonian boundary and in the latest carboniferous eustatic lows are recorded in the early devonian near the mississippian pennsylvanian boundary and in the late permian one hundred and seventy two eustatic events are documented for the paleozoic varying in magnitude from a few tens of meters to 125 meters

a pedotype approach to latest cretaceous and earliest tertiary paleosols in eastern montana a pedotype approach to the study of paleosols emphasizes individual profiles it is an alternative approach to the study of geosols which are laterally extensive suites of paleosols or pedofacies which are pedogenically distinctive sedimentary facies this is the first pedotype study of paleosols across the cretaceous tertiary boundary in eastern montana pedotypes allow assessment of sedimentation and fossilization the sequence of paleosols across the cretaceous tertiary boundary at bug creek is one of high temporal resolution because most available geological time can be accounted for by differing degree of development inferred for each pedotype paleosols at bug creek include pedotypes that preserve plant fossils well but were unfavorable for preservation of fossil vertebrates pedotypes also allow reassessment of ecosystem change despite indications of catastrophe at the cretaceous tertiary boundary the array of paleocene and cretaceous pedotypes are not strikingly different the upper cretaceous hell creek formation includes pedotypes interpreted as gleyed alfisols inceptisols and entisols probably formed under seasonally water logged forest and mean annual rainfall of the order of 900 1200 mm most paleosols of the lower paleocene tullock formation were histosols but some can be interpreted as gleyed inceptisols and entisols probably formed under bald cypress swamps in a humid climate with 1200 mm mean annual rainfall broadly comparable pedotypes were present before and after the cretaceous tertiary boundary although paleocene flood plain forest lived in paleosols chemically a little more oligotrophic than cretaceous paleosols this modest difference supports the idea that change to coaly facies in the earliest paleocene was a local shift in sedimentary environment such local changes do not begin to account for profound disruption in specific composition of plant and animal communities at the cretaceous tertiary boundary in eastern montana

metal pollution of estuarine sediments caused by leaching of acid sulphate soils abstract this study tracks changes in metal distribution in estuarine sediments as a result of leakage from acid sulphate as soil landscapes in the boreal zone finland the main objective was to identify the impact of these nasty soils on sediment geochemistry in a biologically sensitive and shallow brackish water estuary in order to do this four sediment cores were sampled in a profile extending seawards from the mouth of the vora river which is one of the most heavily as soil impacted rivers in finland and europe two of the cores were rather deep 2 5 m and 4 0 m and the others were shallow 0 4 m and 0 8 m the results showed that an appreciable amount of aluminium al cobalt co cadmium cd copper cu manganese mn nickel ni and zinc zn were elevated in the surface and sub surface of the sampled bottom sediments compared to the deeper sediment background levels these metals are all known to be abundantly leached from the as soils at the site approximately 4 km away from the river mouth the concentrations of cd co mn ni and zn were elevated 5 100 times as compared to the background levels and showed an intriguing cyclic pattern most likely reflecting seasonal leaching dynamics in the as soil landscapes in contrast metals that are not abundantly leached from as soils i e chromium cr iron fe and vanadium v had consistently low concentrations throughout all sediment cores the elevated metal concentrations in the top layers of the sediments in the estuary are alarming the continuous land uplift of the region combined with the episodic rapid declines in ph may result in short and long term extensive release of metals this in turn may have significant effects on the trace metal contents in the gulf of bothnia and the entire baltic sea

a trans atlantic upper ocean temperature section along 11 15 s in march 1983 the temperature structure of the upper 500m was resolved with an average station spacing of 29 km along 11 15 s across the atlantic in march 1983 to the east of 5e an intense thermocline was observed with 18c to 24c isotherms lying within 20 m of 45 m elsewhere the temperature distribution was consistent with a pattern of southward flow above 300 m at the south american coast as well as southward flow in intermediate waters 10 12c to the east of 5e and in the region between 32w and 34w from 34w to brazil northward flow was indicated for intermediate waters mesoscale variability was not observed

review short term sea level changes in a greenhouse world a view from the cretaceous abstract this review provides a synopsis of ongoing research and our understanding of the fundamentals of sea level change today and in the geologic record especially as illustrated by conditions and processes during the cretaceous greenhouse climate episode we give an overview of the state of the art of our understanding on eustatic global versus relative regional sea level as well as long term versus short term fluctuations and their drivers in the context of the focus of unesco iugs igcp project 609 on cretaceous eustatic short term sea level and climate changes we evaluate the possible evidence for glacio eustasy versus alternative or additional mechanisms for continental water storage and release for the cretaceous greenhouse and hothouse phases during which the presence of larger continental ice shields is considered unlikely increasing evidence in the literature suggests a correlation between long period orbital cycles and depositional cycles that reflect sea level fluctuations implying a globally synchronized forcing of eustatic sea level fourth order depositional sequences seem to be related to a 405 ka periodicity which most likely represents long period orbital eccentricity control on sea level and depositional cycles third order cyclicity expressed as time synchronous sea level falls of 20 to 110 m on 0 5 to 3 0 ma timescales in the cretaceous are increasingly recognized as connected to climate cycles triggered by long term astronomical cycles that have periodicity ranging from 1 0 to 2 4 ma future perspectives of research on greenhouse sea level changes comprise a high precision time scale for sequence stratigraphy and eustatic sea level changes and high resolution marine to non marine stratigraphic correlation

mid holocene sea level fluctuation inferred from diatom analysis from sediments on the west coast of korea diatoms from the ks2009 core sediment on the coast of the west sea kunsan si and the kr07 trench sediment collected from the neighboring sabsi island korea were analyzed for holocene sea level fluctuations in ks2009 core sediment results of ams 14c dating identified five stratigraphic horizons ranging from 2200 to 9100 bp the results obtained by measuring the radiocarbon dating from the kr07 were as follows 0 34 m a s l 6108 bp 0 74 m 6488 bp 1 46 m 6838 bp and 1 58 m 7208 bp diatom assemblages from ks2009 indicated facies a barren zone ks2009 23 5 to 20 3 m facies b high tidal flat ks2009 20 3 to 14 6 m holocene marine transgression facies c mid tidal flat ks2009 14 6 to 2 0 m falling sea level rising sea level facies d high tidal flat ks2009 2 to 2 m rising sea level thus after seawater influx started at 8300 bp seawater rose with fluctuations rising and falling the kr 07 trench deposit of sabsi island showed facies a barren zone kr07 1 58 to 1 18 m facies b bog kr07 1 18 to 0 76 m facies c tidal marsh kr07 0 76 to 0 52 m facies d tidal flat kr07 0 52 to 0 28 m facies e tidal marsh kr07 0 28 to 0 08 m facies f tidal flat kr07 0 08 to 0 06 m transgression occurred first about 8 300 bp at the west coast of korea around 6300 6000 bp there was a drop in the sea level and around 6000 4000 bp there was a rapid rise also repetition of falling and rising occurred since 4500 bp

cool climate or warm spike lateritic bauxites at high latitudes abstractlaterites and bauxites and their associated ultisols and oxisols are widespread in warm wet climates today and their spread to high latitudes has been attributed to episodes of past global warming bauxitic paleosols from the early eocene monaro volcanics of southeastern australia have been claimed as exceptions formed in a cool wet climate reexamination and chemical analysis of a sequence of intrabasaltic paleosols in the bega no 7 core of radiometrically dated monaro volcanics now show highly variable paleotemperature and precipitation the core includes 53 successive paleosols mostly nonbauxitic but bauxitic paleosols reveal local spikes in warmth and precipitation coincident with early eocene 55 52 51 and 48 ma global spikes of warmth precipitation and high atmospheric co2 these bauxitic paleosols thus formed in warm wet not cool dry climates and their poleward spread coincided with global greenhouse spikes

reconstructions of annual discharge and equilibrium line altitude of glaciers at qilian shan northwest china from 1978 to 2002 discharge was calculated from a mountainous area including discharge from glaciers in the qilian shan qilian mountains of northwest china the studied yingluoxia basin is 9983 km2 in area with glaciers making up 0 3 of the basin the calculation method was based on the heat balance requiring only daily temperature and precipitation calculated annual discharge from the basin corresponded well with the observed data calculated annual discharge from glaciers was 3 6 of the total discharge from the basin the temporal trend of the calculated equilibrium line altitude ela at the july 1st glacier western side of the yingluoxia basin was similar to that of the observed ela the calculated annual mass balance of glaciers within the yingluoxia basin has a larger negative value than the other glaciers in china as the ratio of accumulation area to the total glacier area in the yingluoxia basin is much lower than in neighbouring basins to the west copyright 2010 john wiley sons ltd

late holocene depositional environments and coastal evolution of the mekong river delta southern vietnam abstract the mekong river delta in southern vietnam is a tide dominated delta and has been formed by the mekong river system the sediments are dominantly fine grained and were deposited in the receiving basin with slight inclination of pre existing deposits in the south china sea and gulf of thailand around 6000 to 5000 yr bp maximum holocene transgression occurred and seawaves surrounded uplands of the late pleistocene terrace basement rock and weathered land in the northern parts of the delta double notches were undercut by seawaves on the limestone hill in hatien at about 4 5 and 2 5 m above present sea level marine deposits prevailed throughout the delta during the highstand and regressions of relative sea level over the last 4550 yr bp delta progradation has produced a great flat plain of 62 520 km 2 this extremely fast progradation could be due to a very high sediment supply depositing in the slight inclination of the receiving basin b neotectonic movements and relative sea level changes c widespread mangrove forests playing an important role to enhance sediment accumulation former mangrove marshy deposits were significantly developed in the plain of reeds and longxuyen quadrangle mangrove marshes have also been developing well in the camau peninsula and present coastlines moreover regressions over the last 4550 yr bp have produced many distinct sets of relict beach ridges which are useful in distinguishing the former coastlines and evolutionary history of the delta

paleokarst on the top of the maokou formation further evidence for domal crustal uplift prior to the emeishan flood volcanism abstract the 260 ma emeishan large igneous province elip in southwest china has previously been demonstrated to provide compelling evidence for pre volcanic crustal doming in support of the mantle plume hypothesis however this has been questioned by ukstins peate and bryan 2008 by showing hydrothermal magmatic activity at the daqiao section to solve this argument a detailed characterization of the contact between the emeishan basalts and the maokou formation was carried out the contact is shown to be an unconformity which is characterized by paleokarst on top of the maokou formation including paleokarst relief sinkholes caves tower karst and its corresponding rocks such as kaolinite bauxite and ferruginous duricrust and collapsed breccias etc this paleokarst unconformity was in turn covered or infilled by the emeishan basalts and tuffs suggesting that uplift and erosion occurred prior to the eruption of the elip the extent of erosion of the maokou formation indicates the elip can be divided into three roughly concentric zones the inner intermediate and outer zones the paleokarst features on the top of maokou formation vary across the elip in the inner zone a likely sinkhole and an incision valley with 450 m relief in height are found in the intermediate zone various paleokarst landforms such as karst relief sinkholes and tower karsts are well developed some sinkholes that developed in the qixia formation below the maokou formation imply that the paleorelief is more than 350 m in height in the outer zone the paleokarstic surface is a paleo weathering layer with minor karstification and development of caves at 10 50 m this spatial variation of the paleokarst reflects variation of uplift height across the elip the extent of minimal uplift is estimated to be at least 450 m in the inner zone 350 m in the intermediate zone whereas uplift is minor tens 50 m in the outer zone the magnitude and shape of the uplift is roughly consistent with that predicted by mantle plume models the paleokarst was formed after the deposition of the maokou formation and the eruption of the emeishan basalts at the end guadalupian and indicates a short duration of uplift thus this study lends further support to domal uplift prior to the emeishan flood volcanism but also to the mantle plume initiation model for the generation of the elip

an acid sulfate perspective on landscape seascape soil mineralogy in the u s mid atlantic region abstract a conceptual framework is presented to portray how fe s and other elements ca si k are geologically and pedologically cycled between minerals that are formed and are stable in land based aerobic environments and those that are formed and are stable in anaerobic sea based environments foremost among the elements discussed are fe and s which cycle between fe sulfides formed by sulfidization in the anaerobic sea based environments of tidal marsh and subaqueous soils and sediments and fe oxides and jarosite formed by sulfuricization in upland soils upon the exposure of the sulfide mineral bearing sediments to oxidizing conditions some results of previously conducted experiments are presented to demonstrate that fe oxides placed in the sea based anaerobic tidal marsh and subaqueous soils are rapidly transformed to fe sulfides apparently by the reduction of fe 3 by sulfide of h 2 s generated from sulfate of sea water with the oxidized form of s serving as the electron acceptor during the oxidation of organic matter documentation of rapid sulfuricization of sulfidic materials to form sulfuric horizons upon exposure to aerobic conditions is also presented ca from sea water biologically precipitated as calcite and aragonite in shells of organisms that thrive in brackish sea influenced environments is sometimes transformed temporarily before dissolution and leaching of the ca and sulfate into gypsum by sulfuricization in uplands when the shells are present in exposed sulfidic materials silica is also released from silicate minerals during sulfuricization which can reprecipitate as opal ct to cause cementation of soil materials into duripan like formations in the geologic past opal in the form of diatoms and glauconite formed in tertiary age geologic sediments under marine conditions to become part of the parent materials for upland active and post active acid sulfate soils of the present time modern formation of glauconite in subaqueous soils and shallow sediments has not been found but the topic needs further investigation

responses of coral reefs to increased amplitude of sea level changes at the mid pleistocene climate transition abstract we show responses of coral reefs to increased amplitude of sea level changes at the mid pleistocene climate transition mpt based on lithostratigraphic sedimentologic and calcareous nannofossil biostratigraphic investigations on pleistocene reef complex deposits ryukyu group on the motobu peninsula okinawa jima central ryukyus our data show that reef growth started in earliest quaternary time 1 45 1 65 ma and that extensive reef formation dates back to 0 8 ma the mode of quaternary sedimentation changed at 0 8 ma in the study area before this time thick siliciclastics and mixed carbonate siliciclastics accumulated which were followed by the deposition of bioclastic sediments detrital limestone no indications have been found of episodic subaerial exposures in these deposits and no calcareous nannofossil biozones are lacking since the detrital limestone includes biogenic components characterizing fore reef to shelf environments the coastal areas of the northern motobu peninsula mostly lay in fore reef to shelf environments for 0 6 million years between 0 8 ma and 1 45 1 65 ma when the sediments had not been subaerially exposed due to sea level changes characterized by relatively small amplitudes coral limestone that formed in the latest early to middle pleistocene between 0 4 ma and 0 8 ma extends over the study area ranging in elevation from 0 to 70 m this coral limestone grades upward into fore reef to shelf carbonates rhodolith cycloclypeus operculina and detrital limestones which is in turn overlain by coral limestone this succession combined with configuration of the lithofacies and paleobathymetry inferred from lithology and biogenic components implies that the reef complex deposits formed responding to sea level changes with amplitude of 60 m consequently we suggest that the change in the mode of sedimentation results from increased amplitude of sea level fluctuations at 0 8 ma this timing corresponds roughly to the timing of the mid pleistocene climate transition mpt

geochemical and palynological sea level proxies in hemipelagic sediments a critical assessment from the upper cretaceous of the czech republic geochemical and palynological records are presented for an expanded turonian coniacian hemipelagic succession in the central bohemian cretaceous basin a high resolution stratigraphic framework is provided by biostratigraphy and organic carbon stable isotope 13corg chemostratigraphy a short term 100 kyr sea level curve has been derived from high resolution transgressive regressive maxima shore proximity data established from basin wide sediment geometries the viability of geochemical and palynological parameters as potential sea level proxies is tested against this independently derived sea level record elemental chemostratigraphy is demonstrated to offer a reliable means of identifying medium to long term 0 4 2 4 myr sea level trends manganese maxima are associated with periods of high sea level and troughs with intervals of low sea level falling mn contents accompany regression and rising values transgression major transgressive events associated with medium term sea level change are marked by sharp increases in ti al ratios but short term 100 kyr sea level cycles are not consistently identified long term 13corg variation and dinoflagellate cyst species richness are positively correlated and show similarities to the sea level curve baseline trends have a cycle duration close to the 2 4 myr long eccentricity cycle dinocyst species richness closely follows short term changes in sea level with marked increases in dinocyst diversity coincident with most short term flooding events periods of rapid sea level rise caused an influx of a more diverse outer shelf assemblage into the study area together with the addition of shallower water species some of which may have been transported into the central basin by hypopycnal flows changes in the proportion and abundance of peridinioid dinoflagellate cysts principally palaeohystrichophora infusorioides were controlled principally by changing nutrient levels proximity proxies derived from geochemical and palynological data are not always consistent with the independent sea level model this exemplifies the need to understand all factors influencing elemental geochemical and palynological proxies before making simplistic sea level interpretations

micromorphological and sem analysis of cretaceous paleogene petrosols from eastern montana and western north dakota abstract microscopy is used to distinguish pedogenic features from those associated with primary sedimentary fabric and non pedogenic diagenesis in a suite of 65 million year old sediments sand to clay sized material was deposited in meandering river systems over a broad coastal alluvial plain and pedogenesis occurred in all lithologies a variety of petrosol lithified soil horizons which exhibit both syndepositional bedding and pedogenic and non pedogenic diagenetic features remains today features attributable to the in situ interaction between root and soil provide the most convincing evidence of pedogenesis in addition features such as illuvial clay and iron oxide accumulations around voids which are commonly but not exclusively associated with soil environments provide accessory evidence of pedogenesis stress related void and ground mass birefringence fabrics are evident in the petrosols and some purely sedimentary deposits and thus cannot be used as diagnostic indicators of pedogenesis in this fluvial setting erosion and transport of soil material occurred which is indicated by the presence of pedorelicts in petrosol horizons and purely sedimentary deposits detailed study both by petrographic and by scanning electron microscope elucidates pedogenic indicators not visible in hand samples such tools are useful in resolving ambiguities between pedogenesis and non pedogenic diagenesis

a remarkable sea level drop and relevant biotic responses across the guadalupian lopingian permian boundary in low latitude mid panthalassa irreversible changes recorded in accreted paleo atoll limestones in akasaka and ishiyama japan abstract the capitanian upper guadalupian to wuchiapingian lower lopingian shallow marine limestones at akasaka and ishiyama in central japan record unique aspects of the extinction related guadalupian lopingian boundary g lb interval the ca 140 m thick akasaka limestone consists of the capitanian black limestone unit b 112 m and the wuchiapingian light gray dolomitic limestone unit w 21 m with a black white striped limestone unit s 9 m between them the g lb horizon is assigned at the base of unit w on the basis of the first occurrence of the wuchiapingian fusulines the capitanian unit b and the wuchiapingian unit w were deposited mostly in the subtidal zone of a lagoon whereas the intervened unit s and the lowermost unit w were in the intertidal zone a hiatus with a remarkable erosional feature was newly identified at the top of unit s these records indicate that the sea level has dropped significantly around the g lb to have exposed the top of the atoll complex above the sea level the ishiyama limestone located ca 10 km to the north of the akasaka limestone retains almost the same depositional records the extinction of large tested fusuline yabeina and large bivalves alatoconchidae occurred in the upper part of unit b and the overlying 20 m thick limestone the uppermost unit b and unit s below the hiatus represents a unique barren interval the upper half of the barren interval is more depleted in fossils than the lower half and this likely represents a duration of the severest environmental stress es for the shallow marine protists animals on the mid oceanic paleo atoll complex small tested fusulines re appeared at the base of unit w above the hiatus these facts prove that the elimination of shallow marine biota occurred during the capitanian shallowing of akasaka paleo atoll before the subaerial exposure erosion across the g lb the overall shallowing and the development of such a clear hiatus at the top of a mid oceanic seamount in accordance with the contemporary sea level curve based on continental shelf records indicates that a remarkable sea level drop has occurred globally during the latest capitanian this further suggests that a cool climate likely has appeared even in the low latitude domains in panthalassa to cause the decline of the middle permian shallow water protists animals that adapted to warmer seawater the wuchiapingian biota first appeared immediately after this erosional episode i e during the onset of warming after the g lb