climate and environment of a pliocene warm world the pliocene epoch 5 33 2 58 million years ago ma was a generally warmer and wetter interval with atmospheric co2 concentrations at or slightly above modern levels this paper provides an overview of pliocene vegetation sea surface temperatures and climate modelling outcomes most prominent changes in pliocene biome distribution compared to today include a northwards shift of temperate and boreal vegetation zones in response to a warmer and wetter climate as well as an expansion of tropical savannas and forests at the expense of deserts faunal analysis techniques and modelling experiments using the hadley centre climate model identified significantly higher pliocene sea surface temperatures at mid and high latitudes of the northern hemisphere with cooling or unchanged sea surface temperatures at low latitudes global mean annual surface temperatures mat are estimated to have been 2 to 3 c higher during the piacenzian 3 6 2 58 ma than today with a reduced equator to pole gradient the marine realm during the pliocene was characterised by a reconfiguration of ocean gateways particularly the narrowing of the indonesian seaway and closure of the central american isthmus which produced essentially a modern pattern of ocean circulation in the southern ocean a warm early pliocene gave way to late piacenzian cooling proxy data indicate a reduced east to west sea surface temperature gradient in the tropical pacific during the pliocene warmth the pliocene is one of the most intensively studied geological intervals of the pre quaternary no other warm period in the geological past yields such a unique combination of near modern atmospheric co2 concentrations palaeogeography and palaeobiology however this paper also identifies data gaps and shortcomings in the reconstruction of pliocene environments using proxy data and climate models on which future research should focus

stratigraphy composition and form of the deccan basalts western ghats india in the western ghats between latitudes 18 20 n and 19 15 n 7000 km2 of deccan basalt have been mapped with the primary objective of establishing a flow stratigraphy as a guide to the volcanic history of the flood basalts using over 70 measured vertical sections major and trace element analyses of nearly 1200 samples and rare earth and87sr 86sr determinations for over 60 samples we divide the basalt into three subgroups and ten formations in this paper we describe the seven principal formations in the area and the most prominent individual flows

the significance of marine boreal molluscs in the early pleistocene faunas of the mediterranean area abstract repeated migration of boreal guests into the mediterranean during the early pleistocene has been considered a weak paleoclimatic oceanographic tool this attitude is partly held because the plio pleistocene boundary as defined in the mediterranean does not seem to coincide with isotopic events more important than those of the piacenzian an analysis of their present biogeographical distributions suggests that the successful migration of the boreal elements into the early pleistocene mediterranean was caused by the establishment of a climatic phase of high seasonality with winter temperatures lower than 9 10 c and summer temperatures not lower than 20 c such a situation would also have been suitable for the taxa of warm affinity that characterize the present mediterranean moroccan bioprovince this hypothesis applies mainly to the first phase of migration santernian substage which is the best known from a malacological point of view the available paleoclimatic and isotopic record seems in agreement with the hypothesis

the history of the major rivers of southern britain during the tertiary the evolution of the drainage system of lowland britain is discussed on the basis of available geological evidence including that from terrestrial sites and that which has more recently become available from offshore exploration of the north sea the english and bristol channels and the irish sea tertiary stratigraphy throws considerable light on landform and river development paleocene destruction of a chalk cover which seems to have been incomplete in western britain was accompanied by basin sedimentation under a tropical climate the major elements the thames solent hampshire proto avon river irish sea river and possibly an early trent river existed almost throughout the cenozoic the influence of atlantic rifting and thermal doming in nw britain appears to have been stronger and more temporally focused than the persistent flexuring that determined and maintained tertiary drainage lines in the se here also the folded mesozoic terrains on the surface contrast with the more dominant block faulted relief of the palaeozoic oldlands the rivers of the se can be shown to have extended or reduced their lengths in response to relative sea level change and gentle warping drainage antecedence the destruction of the solent system and the breaching of the english channel are also evident by contrast the major river systems of the west are now entirely submerged long term stability of the drainage pattern reflects a persistent tectonic regime in the south with a subdued low relief landscape having a weathered regolith and dense vegetation cover meandering river channels and alluvial styles predominated although channel forms varied according to sediment load slope and discharge variability coarse gravel dominated accumulations are rare and localized chemically stable lithologies dominate the clastic component throughout it is apparent that the deeply incised river valleys seen today are related to high predominantly coarse sediment yields encouraged by substantial rapid climate changes in the pleistocene this emphasizes the significance of mechanical compared with chemical weathering for the rate and nature of landscape dissection and the modifications that have arisen as a result of glaciation frost climate weathering rapidly changing climates and sea levels the stratigraphical evidence here reviewed is at variance with older largely geomorphologically based landform evolution models denudational chronology but gives considerable support to the recent proposals emphasizing the significance of paleocene erosion and enduring low relief landscapes and drainage systems evolving alongside fold development during the paleogene given the depobasin evidence now available postulated fluvially active episodes can and must be linked to contemporaneous deposition some at least of the many controversies involving the identity of erosion surfaces the dating of them using only residual deposits and weathering mantles and the selection of particular tertiary episodes as ones of landscape development can now be resolved

low temperature aqueous alteration of basalt mineral assemblages of deccan basalts and implications for mars spectra of basalt samples were dominated by fe 2 crystal field transitions with weak alteration bands near 1 4 and or 1 9 mm reststrahlen bands in mid infrared showed the convolution of plagioclase and pyroxene features typical of basalts saprolite samples were incompletely leached and their spectra were dominated by complex al and fe mg bearing smectite clays and retained no original mafic signatures xrd and mossbauer detected pyroxene and plagioclase not visible by reflectance spectroscopy in some saprolite samples zeolites were present throughout the saprolite the laterite was the most leached horizon and all analyses showed kaolinite and iron oxide assemblages this kaolinite and hematite association would be expected if kaolinite on mars formed through leaching under conditions similar to those on earth and has implications for abundant freshwater on the martian surface

plio pleistocene palaeogeography of the southern north sea basin 3 75 0 60 ma abstract palaeogeographical maps are presented for the southern north sea basin from approximately 1 w to 7 e and 51 55 n for the period from approximately 3 75 0 60 ma reconstructions centre on 3 75 ma coralline cragbrunssumian 2 55 ma red crag brielle ground reuverian 2 40 ma red crag westkapelle ground praetiglian early tiglian 2 00 ma norwich crag smith s knoll and ijmuiden ground middle tiglian 1 75 1 70 ma cromer forest bed paston winterton shoal late tiglian eburonian 1 40 ma kesgrave yarmouth roads waalian 1 15 ma kesgrave yarmouth roads menapian and 0 60 ma cromer forest bed west runton yarmouth roads cromerian complex from 3 75 2 40 ma the basin is mainly a marine area fringed to the east and south by fluviatile deposition and broadly open via the southwest to the atlantic following marked marine regression and cooling at around 2 40 ma the period from 2 00 1 70 ma is mainly one of renewed marine transgression and warmer conditions during which a great european delta built out fed mainly from the east and south into the southern north sea from 1 40 0 60 ma marine waters were almost entirely excluded from the area and temperate intervals alternated with increasingly glacial episodes whilst the great european delta continued to expand northwards into the northern north sea

marine climate and hydrography of the coralline crag early pliocene uk isotopic evidence from 16 benthic invertebrate taxa abstract the taxonomic composition of the biota of the coralline crag formation early pliocene eastern england provides conflicting evidence of seawater temperature during deposition some taxa indicating cool temperate conditions by analogy with modern representatives or relatives others warm temperate to subtropical tropical conditions previous isotopic 18 o evidence of seasonal seafloor temperatures from serial ontogenetic sampling of bivalve mollusk shells indicated cool temperate winter 18 o the shell 18 o data either strongly indicate or are at least consistent with cool temperate seafloor conditions the subtropical tropical conditions suggested by the presence of the bryozoan metrarabdotos did not exist microgrowth increment and 13 c evidence indicate summer water column stratification during deposition of the ramsholt member unlike in the adjacent southern north sea at present well mixed due to shallow depth and strong tidal currents summer maximum surface temperature was probably about 5 c above seafloor temperature and thus often slightly higher than now 17 19 c rather than 16 17 c but only sometimes in the warm temperate range winter minimum surface temperature was below 10 c and possibly the same as at present 6 7 c an expanded surface temperature range compared to now may reflect withdrawal of oceanic heat supply in conjunction with higher global temperature

stratigraphy structure and volcanology of the se deccan continental flood basalt province implications for eruptive extent and volumes the deccan volcanic province is one of the world9s largest continental flood basalt provinces and derives additional importance because its eruptions 64 67 ma straddle the cretaceous tertiary boundary to better assess the environmental impact of deccan volcanism and its possible effect upon cretaceous tertiary boundary biota it is necessary to document the stratigraphy chronology and volume of the eruptions new chemostratigraphical data permit mapping of the se deccan these data strengthen the likelihood that the rajahmundry traps of eastern india were originally fed by long distance flows and are an extension of the main deccan volcanic province an east west cross section reveals a depression or moat around the se periphery of the deccan volcanic province this provided a site in which shallow lakes initially formed and along which later lava eruptions became channelled and confined published palaeomagnetic data indicate that the lavas of the se deccan were erupted during chron 29r coeval with the cretaceous tertiary boundary and the chemostratigraphic data place the associated lake sediments i e lameta group beneath and within lavas of the wai subgroup finally these new map data are combined with previous work to provide a quantitative estimate for the original deccan volcanic province eruptive volume of c 1 3 10 6 km 3

comparative sclerochronology of modern and mid pliocene c 3 5 ma aequipecten opercularis mollusca bivalvia an insight into past and future climate change in the north east atlantic region records of environment contained within the accretionarily deposited tissues of fossil organisms afford a means of detailed reconstruction of past climates and hence of rigorous testing of numerical climate models we identify the environmental factors controlling oxygen and carbon stable isotopic composition and microgrowth increment size in the shell of modern examples of the queen scallop aequipecten opercularis this understanding is then applied in interpretation of data from mid pliocene a opercularis from eastern england on the basis of oxygen isotope evidence we conclude that winter minimum seafloor temperature was similar to present values typically 6 7 c in the adjacent southern north sea and that summer maximum seafloor temperature was a few degrees lower than present values typically 16 17 c this contrasts with evidence from other proxies that winter and summer temperatures were higher than present the pattern of seasonal variation in microgrowth increment size suggests the existence of intense thermal stratification in summer we therefore conclude that summer surface temperatures were much higher maxima well over 20 c than those recorded isotopically on the seafloor and that the annual range of surface temperature probably over 14 c was greater than now at the times in the mid pliocene when the investigated a opercularis were alive taken in conjunction with other proxy evidence of warmer winters as well as summers the data point to substantial fluctuation up to 10 c in winter minimum temperatures during the mid pliocene in the north east atlantic region this fluctuation may be attributable to variation in the strength of the gulf stream north atlantic drift since the pliocene has been widely used as a test bed for numerical models of a greenhouse earth the results have implications for prediction of future climate in the north east atlantic region under the influence of anthropogenic global warming

probabilistic models for estimating lithology abstract the estimation of lithology within a volume of rock from surface mapping and borehole logging has been achieved using probabilistic models the application of two geostatistical techniques indicator kriging and conditional simulation allows the incorporation of observed lithologies taking cognisance of their statistical and spatial distributions the newly developed probabilistic bayes markov method additionally allows for the sequences of lithologies to be modelled by the calculation of transition probabilities and markov chains verification of the estimates produced by these three methods has been enabled using the rocks actually exposed during the driving of an access tunnel into the aspo hard rock laboratory in south east sweden

pliocene dinoflagellate cyst stratigraphy palaeoecology and sequence stratigraphy of the tunnel canal dock belgium dinoflagellate cysts and sequence stratigraphy are used to date accurately the tunnel canal dock section which contains the most complete record of marine pliocene deposits in the antwerp harbour area the zanclean kattendijk formation was deposited between 5 0 and 4 4 ma during warm temperate conditions on a shelf influenced by open marine waters the overlying lillo formation is divided into four members the lowest is the luchtbal sands member estimated to have been deposited between 3 71 and 3 21 ma under cooler conditions but with an open water influence the oorderen sands kruisschans sands and merksem sands members of the lillo formation are considered a single depositional sequence and biostratigraphically dated between 3 71 and c 2 6 ma with the oorderen sands member no younger than 2 72 2 74 ma warm temperate conditions had returned but a cooling event is noted within the oorderen sands member shoaling of the depositional environment is also evidenced with the transgressive oorderen sands member passing upwards into near coastal high stand deposits of the kruisschans sands and merksem sands members as accommodation space decreased applying sequence stratigraphy to our section implies that the kattendijk lillo formation boundary corresponds to the sequence boundary sb za2 4 04 ma the luchtbal oorderen sands boundary to sb pia1 3 21 ma and the top of the merksem sands to sb pia2 2 76 ma finally the belgian deposits are compared with marine pliocene deposits of eastern england

pliocene seasonality across the north atlantic inferred from cheilostome bryozoans abstract previous studies have shown an inverse correlation between zooid size in cheilostome bryozoans and ambient water temperature this relationship underlies the mart technique which uses intracolonial variation in zooid size to predict mean annual range in temperature experienced by bryozoan colonies during their life here we apply the mart technique to study early and mid pliocene bryozoans from central america panama costa rica the usa florida south carolina north carolina virginia and the uk suffolk to reconstruct palaeoseasonality across a range of latitudes for the north atlantic during the pliocene epoch compared to the present day our analyses suggest greater seasonality ca 4 5 c in the southern caribbean at the time of cayo agua formation deposition ca 4 25 ma in keeping with inferred upwelling prior to the closure of the isthmian barrier at 2 7 ma bryozoans also indicate seasonal upwelling on the gulf coast of florida in a similar manner to the present day because upwelling can be highly localised and prone to spatial and temporal variation in the gulf of mexico today it contributes little to a broad understanding of pliocene north atlantic waters however mart estimates for the coastal plain region indicate a general reduction in the annual range in temperature relative to the present suggesting that the colder surface waters that today reach south to cape hatteras had less influence in early to mid pliocene times these results along with evidence from other proxies strongly support reduced seasonality and warmer conditions along the eastern seaboard of the usa in the early to mid pliocene finally the mart estimates amongst coralline crag localities provide evidence for an increased annual range in temperature in the southern north sea than at present our study shows that bryozoan mart estimates provide a powerful independent proxy for palaeoseasonality and is the first to demonstrate that the mart technique can be applied to infer palaeoclimates across a wide range of latitudes focusing on a variety of geological formations and geographical regions

strontium isotopic variations in jurassic and cretaceous seawater a high resolution seawater strontium isotope curve has been generated through the analysis of well dated and well preserved belemnites and oysters from the middle and upper jurassic and the lower cretaceous of great britain analysis of fe and mn concentrations in these fossils has yielded criteria for eliminating samples that are diagenetically altered the strontium isotope curve remains relatively flat through the aalenian and early bajocian rapidly descends through the late bajocian and bathonian and reaches a minimum in the callovian and oxfordian it then begins a rapid increase in the kimmeridgian and portlandian that continues through much of the early cretaceous the curve levels off in the barremian suddenly dips downwards in the aptian and recovers gradually through the albian the strontium isotopic variations are sufficiently large and the data are presented with sufficient stratigraphic detail to allow precise correlation to the classic ammonite zones and lithologic sections of great britain using the techniques of strontium isotope stratigraphy model results indicate that much of the variation in seawater 87sr86sr between 120 and 40 ma can be explained by changing the intensity of mid ocean ridge hydrothermal fluxes proportionally to estimated mid ocean ridge crustal generation rates it is also possible that the variations during the rest of the mesozoic and the permian are primarily reflections of changing hydrothermal inputs the model results have several important implications first they provide an example in which the variations in the strontium isotope curve are not necessarily driven by changes in fluvial inputs second they suggest that from at least the aptian through the eocene variations in continental weathering were minimal this heightens the importance of the rapid rise in seawater 87sr86sr beginning 40 ma as a significant transition to an extended period of increasing fluvial 87sr fluxes continuing to the present finally the results suggest that several documented short term excursions towards lower 87sr86sr in the latest triassic pliensbachian toarcian callovian oxfordian aptian albian and cenomanian turonian are interpretable as pulses of seafloor hydrothermal activity if so the strontium isotope record offers a means of constraining the timing duration and magnitude of known or proposed hydrothermal events in the geological record

central american paleogeography controlled pliocene arctic ocean molluscan migrations the pliocene interchange of north pacific and north atlantic marine faunas via the arctic ocean was long thought to have been a single episode of faunal exchange between the northern oceans that took place as soon as the bering strait first opened new evidence implies that there were two northern migration events instead of one and that the second phase of migration was much later than the first the migration of atlantic arctic mollusks into the bering sea and north pacific when the bering strait first opened at 4 8 5 5 ma constituted the initial phase of this interchange but the abrupt appearance of north pacific mollusks in the north atlantic at 3 6 ma postdated the first opening of the bering strait by 1 2 1 9 m y this second phase of trans arctic migration was also coeval with shoaling of the central american seaway between north and south america this late pliocene trans arctic migration of north pacific mollusks is evidence for the reversal of marine flow to northward through the bering strait which was one consequence of the reorganization of northern hemisphere ocean circulation caused by substantial closure of the central american seaway this inferred causal link between the histories of the beringian and panamanian ocean gateways is in agreement with ocean circulation models

cerium anomalies in lateritic profiles the ree geochemistry and mineralogy have been studied in four lateritic profiles one derived from a syenite akongo sw cameroon the others being developed on a gneissic basement and located along a soil toposequence goyoum e cameroon there is a fractionation between lree and hree in the lateritic samples during weathering the weathered residual products being enriched in lree from la to eu and depleted in hree from gd to lu sampled waters are enriched in hree in relation to the syenite host rock a positive ce anomaly has been found systematically at the top of the saprolite beneath a zone of iron oxide accumulation in the laterite up to 2000 ppm ce may be present in the akongo profile cerianite ceo2 is present as very fine coatings in non ferruginous clayey domains primary ree bearing accessory minerals are weathered at the bottom of the profile specifically allanite and apatite are transformed into florencite and rhabdophane but these phases have no ce anomaly all the data are interpreted as the result of the following processes 1 1 ree leaching in a reducing environment 2 2 oxidation of ce3 to ce4 in an oxidizing environment 3 3 deposition of cerium as cerianite whereas the other ree remain in solution

pliocene climate and seasonality in north atlantic shelf seas this paper reviews north atlantic shelf seas palaeoclimate during the interval 4 3 ma prior to and incorporating the mid pliocene warm period ca 3 29 2 97 ma fossil assemblages and stable isotope data demonstrate northwards extension of subtropical faunas along the coast of the carolinas virginia yorktown and duplin formations relative to the present day suggesting a more vigorous florida current with reduced seasonality and warm water extending north of cape hatteras reconstructed annual range for virginia 12 30 c this interpretation supports conceptual models of increased meridional heat transport for the pliocene sea temperatures for florida lower pinecrest beds were similar to or slightly cooler than summers 25 27 c today and were probably influenced by seasonal upwelling of cold deep water reduced seasonality is also apparent in the coralline crag formation of the southern north sea with ostracods suggesting winter sea temperatures of 10 c modern 4 c however estimates from pliocene bivalves 3 6 16 6 c are similar to or cooler than the present day this mixed signal is problematic given warmer seas in the carolinas virginia and climate model and oceanographic data that show warmer seas in the mid pliocene eastern north atlantic this may be because the coralline crag formation was deposited prior to peak mid pliocene warmth

implications of the infra and inter trappean biota from the deccan india for the role of volcanism in cretaceous tertiary boundary extinctions the fossil record shows a remarkable similarity between the biota that existed before and after the initiation of deccan volcanic activity virtually all the available palaeontological evidence such as the fauna and flora of the freshwater infra and inter trappean beds and the planktonic foraminifera from the subsurface infra and inter trappean beds of the southeastern coast do not favour the initiation of deccan volcanism as the cause of mass extinctions at the cretaceous tertiary k t boundary instead a combination of events such as an extended period of volcanism changes in sea level and related climatic changes and certain local factors may have played a significant role in selectively eliminating various groups of organisms this view is further reinforced by the biotic changes across the k t iridium layer in the um sohryngkew river section of meghalaya northeastern india

the prism pliocene palaeoclimate reconstruction time for a paradigm shift global palaeoclimate reconstructions have been invaluable to our understanding of the causes and effects of climate change but single temperature representations of the oceanic mixed layer for dat

eocene paleosols on king george island maritime antarctica macromorphology micromorphology and mineralogy abstract we investigated the origin of reddish layers between basalt flows in an early eocene volcanic succession in king george island maritime antarctica previous studies in the area classified these layers as regolith surfaces baked zones and paleosols but the properties of these layers and the reasons for their classification are not clarified since the early eocene epoch was one of the warmest phases on earth during the cenozoic a proper investigation of these layers is crucial to obtain additional regional information about the paleoenvironment the focus of this study is on three profiles located in the admiralty bay on king george island they were classified as paleosols based on field micromorphological and mineralogical properties main soil forming processes identified by micromorphological analyses were clay neoformation pedo bioturbation and a weak redoximorphosis the occurrence of plant residues in all profiles was a reliable indicator that these soils formed a land surface during the early eocene abundant weathered volcanic glass and pyroclasts may indicate andosolization although the main diagnostic features for andosols which are the presence of nanocrystalline minerals and organic matter accumulation were not detected or only in small amounts respectively the long term burial of the paleosol could be a reason for lacking of these diagnostic features clay minerals associated with moderately weathered volcanic soils smectite were detected in the x ray diffraction analysis a predominantly reddish colour of most of the soil horizons is given by hematite confirmed by the determination of pedogenic oxides nevertheless rubification was not solely a result of pedogenesis but also of reddening of oxyhydroxides by dehydration during diagenesis other diagenetic processes were burial compaction loss of organic matter and induration in the horizons directly buried by a basalt flow voids were filled by zeolite crystals an effect related to lava cooling another possible diagenetic effect was the geochemical rejuvenation and homogenization of the profiles despite the occurrence of these features the results are in agreement with previous studies indicating a humid temperate paleoclimate for king george island during the early eocene

ree fractionation and ce anomalies in weathered karoo dolerite abstract analyses of samples from a weathering profile on karoo dolerite allow elements to be divided into three groups depending on their behaviour si k na mg ca sr ba and v are mobilized and removed from weathered products fe al ti zr hf zn cu sc co and ni are immobile ree y and to a lesser extent cr are mobile and redistributed within the profile without a net loss of these elements from the profile large positive ce anomalies are developed in oxidized weathered products by preferential leaching of the other ree s negative ce anomalies and ree enrichment is a feature of less altered dolerite

temperate meteoric diagenesis of pliocene skeletal carbonates from eastern england the crags of eastern england include marine skeletal carbonates which were deposited and lithified under temperate conditions the coralline crag pliocene in particular exhibits a variety of carbonate cement types which indicate exposure to meteoric groundwaters during a regressive episode the coralline crag has been divided into an upper division of dominantly well sorted skeletal calcarenites and calcirudites and a lower poorly sorted silty calcarenite division dogtooth spardcement and rudimentary syntaxial cement overgrowths on echinoderm fragments are characteristic of the sediments of the upper division which has undergone extensive aragonite dissolution this division is consequently relatively evenly cemented in the underlying sediments aragonite dissolution has not occurred and the sediments have remained largely uncemented with cement restricted to irregular patches where growth of intra and inter particle equant spar has effectively eliminated porosity in contrast with the upper leached sediments syntaxial echinoderm overgrowths show a greater development but only where interference from surrounding sediment and sparry cement was absent the elongate shape of the coralline crag outcrop may be the result of preferential cementation of the upper coarser well sorted calcarenites originally deposited as an elongate sediment body possibly as an offshore sandbank

surface temperatures of the mid pliocene north atlantic ocean implications for future climate the mid pliocene is the most recent interval in the earth s history to have experienced warming of the magnitude predicted for the second half of the twenty first century and is therefore a possible analogue for future climate conditions with continents basically in their current positions and atmospheric co2 similar to early twenty first century values the cause of mid pliocene warmth remains elusive understanding the behaviour of the north atlantic ocean during the mid pliocene is integral to evaluating future climate scenarios owing to its role in deep water formation and its sensitivity to climate change under the framework of the pliocene research interpretation and synoptic mapping prism sea surface reconstruction we synthesize mid pliocene north atlantic studies by prism members and others describing each region of the north atlantic in terms of palaeoceanography we then relate mid pliocene sea surface conditions to expectations of future warming the results of the data and climate model comparisons suggest that the north atlantic is more sensitive to climate change than is suggested by climate model simulations raising the concern that estimates of future climate change are conservative

volatile fluxes during flood basalt eruptions and potential effects on the global environment a deccan perspective abstract we examine the role that flood basalt eruptions may have played during times of mass extinction through the release of volcanic gases continental flood basalt provinces have formed by numerous eruptions over a short period of geologic time characteristically a few million years within this period a short lived climactic phase that lasts about 1 ma typically emplaces a large proportion of the lava volume this phase consists of a series of huge eruptions each yielding 10 3 10 4 km 3 of magma each eruption lasted on the order of a decade or more and built an immense p hoehoe dominated lava flow field by eruptive activity along fissures tens to hundreds of km long high fire fountains emanating from vents along the fissures at times sustained eruption columns that lofted gas and ash into the upper troposphere and lower stratosphere while the lava flows covered huge areas the combination of large eruption magnitudes maintained high effusion rates during eruptions and the repeated nature of the characteristic large scale eruptive activity occurs in earth history only during periods of flood basalt volcanism based on recent analogs and determination of volatile contents of ancient flood basalt lavas we estimate that individual eruptions were capable of releasing 10 000 tg of so 2 resulting in atmospheric loadings of 1000 tg a 1 during a sustained decade long eruptive event we apply this model of flood basalt volcanism to estimate the potential mass of co 2 and so 2 released during formation of the 65 ma deccan province the deccan lava pile contains the record of hundreds of enormous p hoehoe flow fields erupted within a period of about 1 ma consequently atmospheric perturbations associated with so 2 emissions from just one of these long lasting eruptions were likely to have been severe and constantly augmented over a decade or longer by contrast the amounts of co 2 released would have been small compared with the mass already present in the atmosphere and thus much more limited in effect individual eruptions were followed by hiatuses of hundreds to thousands of years during which the gas contributions to the atmosphere would be recycled it is clear that the nature and potential atmospheric impact of a series of huge volume repeated long term degassing events requires further investigation in conjunction with appropriate climate models

the weathering of basaltic rocks in burundi and vietnam abstract various stages of tropical weathering are described using a number of examples of red soil formation derived from rift basalts in burundi and laterite bauxites from plateau basalts of south vietnam the phenomena of decomposition of primary minerals are comparable in the two regions fine grained montmorillonites kaolinites halloysites and hematite were formed during an initial stage of weathering the two generations of kaolinites goethites and gibbsites are the main products of a more intense stage of weathering the gradients of chemical activities in the micro environment surfaces of grains pores microfissures seem to be the controlling factors of weathering

u pb zircon age constraints on the earliest eruptions of the deccan large igneous province malwa plateau india abstract climate instability driven by emission of volatiles during emplacement of large igneous provinces lips is frequently invoked as a potential cause of mass extinctions however documenting this process in the geologic record requires a holistic understanding of eruption rates the location of eruptive centers and potential sources of climate changing volatiles we present new chemical abrasion isotope dilution thermal ionization mass spectrometry ca id tims u pb zircon geochronology from malwa plateau basalts on the northern margin of the deccan lip india these basalts have been previously interpreted as either an extension of the province s main volcanic stratigraphy or as an independent eruptive center active up to millions of years prior to the main eruptive phase our data instead demonstrate that the lower malwa plateau basalts are temporally correlative with the first pulse of deccan volcanism and provide new constraints on its initiation and duration paleomagnetic data further indicate that upper malwa plateau basalts may be age equivalent to the second third and fourth pulses of deccan volcanism the relative thicknesses of age equivalent packages of basalt are consistent with eruption of the deccan lip from a southward migrating eruptive center the first eruptive pulse is coeval with a 200 kyr late maastrichtian warming event preserved globally in contemporaneous stratigraphic sections we propose that the first pulse of deccan magmatism was more voluminous in the north where it erupted through organic rich sedimentary rocks of the narmada tapti rift basin thermal metamorphism of these sediments could have been a source of sufficient co2 to drive the late maastrichtian warming event which if true would reconcile the apparent dampened warming signals associated with later deccan eruptive pulses

late cretaceous and paroxysmal cretaceous tertiary extinctions the various geological signatures at cretaceous tertiary time including iridium and other associated elements microspherules and shock deformation features are compatible with the suggestion that the transition is marked by a period of intense volcanism the volatile emissions from this volcanism would lead to acid rain reduction in the alkalinity and ph of the surface ocean global atmospheric temperature changes and ozone layer depletion these environmental effects coupled with those related to the major sea level regression of the late cretaceous provide the framework for an explanation of the selective nature of the observed extinction record

the molluscan fauna of the coralline crag pliocene zanclean at raydon hall suffolk uk palaeoecological significance reassessed abstract this study assesses the environmental implications of a quantitative study of the unusually well preserved molluscan fauna of over 200 species about 47 extinct from six samples from both the ramsholt and sudbourne members of the coralline crag formation at a british geological survey borehole at raydon hall near orford suffolk uk it reveals a shallow shelf fauna locally transported from a variety of habitats dominated by infaunal species spisula turritella abra amyclina from relatively fine sediments plus epifauna especially heteranomia possibly in part originating from nearby bryozoan communities as well as dead bivalve shells there was a small but consistent component of deeper water elements such as limopsis and a lack of strictly littoral species overall a water depth of about 50 m is suggested with bottom temperatures at times perhaps warmer than the present southern north sea but not as high as the modern mediterranean and a more oceanic setting this is in contrast to inferences from previous nineteenth century studies of coralline crag molluscs which viewed it as largely mediterranean in character but understated the regular presence of boreal forms such as arctica current interpretations still have to account for the coexistence of some lusitanian or mediterranean molluscan taxa alongside the cooler water elements

a geological map of the southern deccan traps india and its structural implications a geological map of an area of over 125 000 km 2 within the southern deccan traps india is presented which is based upon variations in the basalt geochemistry it represents a synthesis of new data and earlier work the use of large data sets has allowed stratigraphic boundaries to be established with greater accuracy over a much larger area than before the geochemical sections demonstrate that the southward overstepping stratigraphic style encountered along the ghats ridge has an essentially north to south polarity and that there appears to be detectable overstep in an east to west sense however the stratigraphy defines a pronounced coastward dipping monoclinal flexure across the western ghats ridge between 16 n and 18 n the data are consistent with two models of eruption the first considers the deccan eruptive focus to have been fixed throughout the volcanic episode producing an essentially annular flow pattern the second considers the flow pattern to have been generated from a southerly migrating eruptive centre resulting from the northerly drift of india over a fixed hotspot both hypotheses are consistent with recent quantitative models which suggest that rapid and voluminous flood basalt eruptions are the result of continental rifting events associated with plume generated thermal 9highs9 until a causal link between established plume hotspot trails and impact sites can be satisfactorily demonstrated we find it unnecessary to invoke a cataclysmic impact event as an explanation for the deccan eruptions

geochemical differentiation in laterite and bauxite formation abstract the geochemical differences between laterite and bauxite formation are discussed under the aspect that both weathering products are predominantly formed by residual enrichment of iron and aluminium residual enrichment is corroborated by various arguments and clearly proved for laterite formation on ultramafic rocks tropical weathering of the most widespread acidic rocks leads in spite of their high al fe ratio generally to formation of laterites showing a high enrichment of iron whereas aluminium is not or only slightly enriched this chemical variation indicates that high amounts of al are removed additionally to si in soil solutions when saprolites on acidic rocks are transformed into laterites containing goethite hematite and kaolinite as main constituents dissolved free aluminium exist in equilibrium with kaolinite only in minimal contents hence the removal of si and al probably takes place in form of freshly formed colloidal or subcolloidal x ray amorphous particles with kaolinitic or similiar composition the frequently observed occurrence of two generations of secondary kaolinite in laterites corroborates this conclusion there is general agreement that bauxites are formed by stronger leaching compared with laterites increased leaching lowers the concentration of dissolved silica thus enabling gibbsite instead of kaolinite stability the concentration of dissolved free aluminium however is increased in equilibrium with gibbsite free aluminium shows in contrast to iron an effective solubility atph 5 giving rise to downward leaching and re precipitation at higher ph below a laterite crust which covers the bauxite zone in most of the bauxite deposits in spite of the stronger leaching bauxite formation implies a lower mass loss mainly si during weathering than the formation of laterites loss ofsi al related to their highly increased iron content

dinoflagellate cyst stratigraphy and palaeoecology of the pliocene in northern belgium southern north sea basin dinoflagellate cysts and other palynomorphs from the pliocene kattendijk and lillo formations exposed in two temporary outcrops in northern belgium provide new information on the biostratigraphic position and sequence stratigraphic interpretation of these units dinoflagellate cysts from the kattendijk formation indicate an age between about 5 0 ma and 4 7 4 4 ma early early pliocene in our sections confirming a correlation with standard sequence 3 4 and implying a slightly greater age than the ramsholt member of the coralline crag formation of eastern england the unconformity at the base of the kattendijk formation was not seen but presumably correlates with sequence boundary me2 at 5 73 ma the overlying lillo formation is late early pliocene or early late pliocene c 4 2 2 6 ma in age and the unconformity at its base may be correlated with sequence boundary za2 at 4 04 ma or pia1 at 3 21 ma the oorderen sands and superjacent kruisschans sands members lillo formation are both part of the same depositional cycle they were probably deposited before 2 74 ma and certainly before the onset of northern hemisphere cooling at c 2 6 ma evidence from dinoflagellate cysts indicates that both a shelly unit at the base of the lillo formation and the lower part of the overlying oorderen sands were deposited during a conspicuously cool climatic phase with warmer temperatures returning during later deposition of the oorderen sands and kruisschans sands members many dinoflagellate cyst and acritarch species are reported here for the first time from the southern north sea basin selenopemphix conspicua de verteuil norris 1992 stat nov is proposed

chronostratigraphy of late neogene sediments in the southern north sea basin and paleoenvironmental interpretations a chronostratigraphic framework has been established for upper neogene sediments from the northern netherlands offshore sector southern north sea data of dinoflagellate cysts pollen and foraminifers from eight boreholes are integrated and the resulting biostratigraphic events are connected to an additionally retrieved paleomagnetic record the sedimentary succession comprises at the base late to middle miocene sediments and spans the piacenzian to gelasian stages from 3 6 to 1 8 ma including the paleomagnetic gauss matuyama boundary and the olduvai subchron sedimentation rates vary between 30 cm kyr in the lower part of the succession and reach up to 84 cm kyr in the upper part these rates are high enough to record short paleomagnetic events and for the first time the presence of the so called x event has been recorded and dated at around 2 44 ma in a sedimentary setting the name north sea event is proposed here the paleoclimatic and paleoenvironmental information pictures the onset of northern hemisphere glaciation and the subsequent intensification of glacial conditions with its impact on the north sea sea region the paleoenvironmental changes are characterised by a stepwise development and five successive intervals are distinguished during the first interval a warm climate and an open marine setting prevailed the second interval is characterised by dominantly cold climatic conditions with occasional warmer periods during the third interval the environment became restricted marine and a stable freshwater layering occurred which facilitated the development of sea ice in the shallow sea within the fourth interval extreme cold arctic conditions were predominant and shallowing continued the fifth interval shows fluvial to deltaic paralic conditions from then on facies differences from the nearby delta system overruled the basin wide signals at the studied location 2006 elsevier b v all rights reserved

weathering characteristics of interflow volcanic boles from mandla lobe eastern deccan volcanic province abstract the deccan volcanism straddling the cretaceous paleogene boundary resulted into one of the most extensive continental flood basalts in the western and central peninsular india the interflow sedimentary units boles often cited as paleosols are the rare archives of paleoenvironmental conditions existed during successive lava flows a debate on the origin of boles as true paleosols exists therefore in order to trace out regional extent of such conditions pedogenic non pedogenic in the context of their paleoenvironmental significance during the deccan volcanism we studied here mineral magnetic characteristics of 36 color differentiated bole beds from the mandla lobe in the eastern deccan volcanic province edvp classified into four types gray yellow brown and red based on their munsell notations the gray yellow and brown boles show dominantly ferrimagnetic composition chiefly magnetite and titanomagnetite while red boles characterize mixed ferri and antiferromagnetic mainly hematite mineralogy the granulometric domain parameters suggest larger single domain sd and the multidomain md ferrimagnets in the majority of cases whereas superparamagnetic sp particles with frequency dependent susceptibility fd 2 6 to 20 3 10 8 m 3 kg 1 are limited to the few red and brown boles only the significant presence of primary parent magnetic minerals i e coarse sd md titanomagnetite and magnetite in the majority of boles depict incipient to moderate weathering owing to limited time intervals during successive eruptions the combination of hematite and sp particles present only in the few red and brown boles depicts baking effect rather than pedogenesis the comparison of magnetic properties of boles from edvp and western deccan volcanic province wdvp shows significant differences in the concentration of sp ferrimagnetic particles and hematite attributed to variable weathering intensity duration and heating related alterations from the upper flows both edvp and wdvp boles indicate similar first order paleoenvironmental conditions without any major pedogenesis that can be regionally correlated

the transition from sedimentation to flood volcanism in the kangerlussuaq basin east greenland basaltic pyroclastic volcanism during initial palaeogene continental break up primary basaltic pyroclastic deposits compose volumetrically c 35 50 of the lower palaeogene vandfaldsdalen mikis and haengefjeldet formations within the lower volcanic series of the east greenland flood basalt province the eruption and emplacement mechanisms of these deposits can be used to evaluate the volcanotectonic evolution of continental break up and initiation of flood basalt volcanism we present a revised stratigraphy for the pre volcanic sedimentary rocks and synvolcanic pyroclastic and epiclastic deposits and lavas from the kangerlussuaq basin east greenland primary basaltic pyroclastic deposits range from airfall tuffs to bomb beds surge deposits and vent sites with cinder cones early volcanism was apparently restricted to localized basins and formed shield volcano structures 30 40 km in diameter that are characterized by a heterogeneous sequence of intercalated hyaloclastites sediments pyroclastic deposits and lavas the lateral variation of deposit morphology reflects distance from source and indicates a migrating locus of volcanism along the axis of rifting towards the ne paired with continued down dropping of inactive volcanic centres the complex stratigraphic architecture of the initial volcanic deposits reflects local tectonic and sedimentary processes interacting with regional flood basalt volcanism and continental rifting

the geochemistry of indian bole horizons palaeoenvironmental implications of deccan intravolcanic palaeosurfaces deccan intravolcanic bole horizons represent weathering products formed during major hiatuses of a major volcanic episode in these quiescent periods weathering processes pervasively altered the newly formed volcanic landscape and subsequent flows covered and effectively fossilized the resulting weathered palaeosurfaces the current work is a detailed geochemical study which examines patterns of element mobilization during these intravolcanic weathering events the bole horizons normally rest on top of altered basaltic lavas both boles and altered lavas represent a comparatively early stage in weathering because the content of chemically residual elements such as aluminium and iron are closer to fresh basalt than laterite nevertheless these is clear evidence for significant chemical alteration because the more mobile elements such as calcium and sodium have been substantially removed a chemically distinctive nature for some boles can be demonstrated from chondrite normalized ree plots and in these instances strontium and neodymium isotopic compositions demonstrate that the fine grained bole material is derived from a chemically distinct source in addition thin sections reveal that these fine grained portions commonly contains glass shards and occasionally fresh phenocrysts it is therefore suggested that many deccan boles are in fact weathered pyroclastic material and that the pyroclastic content of the basaltic succession may be greater than previously supposed a significant pyroclastic input during the deccan eruptions has important palaeoenvironmental implications for the fate of late cretaceous flora and fauna in peninsular india

tertiary palaeosurfaces of the sw deccan western india implications for passive margin uplift two genetically distinct lateritized palaeosurfaces of different ages are recognized in the southwest deccan traps region of western india using a combination of geochemical topographical and satellite image data the deccan traps were erupted at the cretaceous tertiary boundary c 65 ma and comprise a huge area of originally near horizontal basalt lavas covering much of northwest peninsular india and topographically forming the coast parallel western ghats escarpment and elevated maharashtra plateau to the east remnants of the older palaeosurface currently exist as a series of isolated laterite capped plateaux forming the highest elevations along the western ghats 15 30 18 15 n this surface is of late cretaceous early tertiary age and originally developed upon flows which lay at or near to the top of the lava sequence this lateritization phase was terminated by a period of uplift and extensive erosion in lower to mid tertiary times during which the low lying low relief coastal konkan plain developed through the eastward recession of the ghats scarpline a second phase of lateritisation occurred upon this coastal pediplain during mid to late tertiary times since the earlier uplift had gently deformed the lava pile prior to the development of the pedimented surface the low level konkian laterite lies with marked angular unconformity upon the lava stratigraphy both surfaces have been subject to further large scale distortion resulting from continuing uplift effects development and evolution of these deccan palaeosurfaces is important since together they provide a record of uplift effects in western india moreover they offer a datum against which the uplift erosional history may be further constrained and demonstrate that uplift effects have acted upon the indian margin throughout the tertiary since such longevity of uplift is difficult to reconcile with the commonly cited thermal and dynamic post rift mechanisms known to act upon passive margins the morphological and structural evolution of the rifted deccan margin is better described in terms of denudational isostasy

globally enhanced mercury deposition during the end pliensbachian extinction and toarcian oae a link to the karoo ferrar large igneous province the mesozoic era featured emplacement of a number of large igneous provinces lips formed by the outpouring of millions of cubic kilometres of basaltic magma the radiometric ages of several mesozoic lips coincide with the dates of oceanic anoxic events oaes as a result of these coincidences a causal link has been suggested but never conclusively proven this study explores the use of mercury as a possible direct link between the karoo ferrar lip and the coeval toarcian oae t oae mercury is emitted to the atmosphere as a trace constituent of volcanic gas and may be distributed globally before being deposited in sediments modern marine deposits show a strong linear correlation between mercury and organic matter content results presented here indicate departures from such a simple linear relationship in sediments deposited during the t oae and also during the pliensbachian toarcian transition an event that saw elevated benthic extinctions and carbon cycle perturbations prior to the t oae a number of depositional settings illustrate an increased mercury concentration in sediments that record one or both events suggesting a rise in the depositional flux of this element complications to this relationship may arise from very organic rich sediments potentially overprinting any hg toc signal whereas environments preserving negligible organic matter may leave no record of mercury deposition however the global distribution of coevally elevated hg rich levels suggests enhanced atmospheric mercury availability during the early toarcian potentially aided by the apparent affinity of hg for terrestrial organic matter although the relative importance of aquatic vs terrestrial fixation of hg in governing these enrichments remains uncertain a perturbation in atmospheric hg is most easily explained by enhanced volcanic output it is suggested that extrusive igneous activity caused increased mercury flux to the early toarcian sedimentary realm supporting the potential of this element as a proxy for ancient volcanism this interpretation is consistent with a relationship between lip formation and a perturbed carbon cycle during the pliensbachian toarcian transition and t oae the recording of these two distinct hg excursions may also indicate that the karoo ferrar lip released volatiles in temporally distinct episodes due either to multiple phases of magmatic emplacement or sporadic release of thermogenic gaseous products from intrusion of igneous material into volatile rich lithologies

pliocene palaeotemperature reconstruction for the southern north sea based on ostracoda abstract the development of a large northeastern atlantic shelf ostracod database has confirmed that an intrinsic relationship exists between watermass temperature and the spatial latitudinal distribution of benthonic shelf ostracoda a second pliocene ostracod database using assemblages from four boreholes in the netherlands and a number of localities from the east anglian neogene succession has also been constructed a quantitative method of modern analogues and the squared chord distance dissimilarity coefficient has been employed as a means of calculating the level of similarity between recent and neogene assemblages and therefore to aid in the reconstruction of palaeotemperatures in the southern north sea basin during the pliocene the results in the form of contoured dissimilarity values indicate the presence of at least seven palaeoceanographical climatic phases between ca 5 2 and 1 6 ma bp an early pliocene cooling phase ecozone a in which the fauna is dominated by the cryophilic species palmenella limicola norman elofsonella concinna jones robertsonites tuberculatus sars neomonoceratina tsurugasakensis tabuki and acanthocythereis dunelmensis norman supervenes a period of stable subtropical conditions in the miocene a mid pliocene warming phase ecozone b which has been documented throughout the north atlantic can be recognized in the faunal composition of the sublittoral ostracod assemblages of both the netherlands and east anglia a hiatus between the coralline and waltonian crags is thought to be associated with a deterioration in climatic conditions recent analogues to the netherlands faunas of ecozone c first phase late pliocene cooling ca 2 9 ma bp indicate a decrease of approximately 5 6 c in mean summer surface temperatures a return to elevated temperatures of a mauritanian aspect can be seen in the fauna of the fa2 zone and waltonian crag this amelioration of climate occurred prior to the praetiglian cold phase second phase late pliocene cooling ca 2 4 ma bp which again saw the reintroduction of cryophilic species including baffinicythere howei hazel fimarchinella logani brady crosskey and robertson and hemicythere emarginata sars into the southern north sea during the newbournian and butleyan stages the final phase of the latest pliocene third phase late pliocene cooling is only documented in the ostracod fauna of the norwich crag evidence in the covariance of loxoconchidae and norwegian provincial cryophilic species indicates that the polar front may have been as much as 2000 km further south during the deposition of the chillesford sand member norwich crag fm ca 2 0 1 6 ma bp