eocene climate record of a high southern latitude continental shelf seymour island antarctica a high resolution record of eocene paleotemperature variation is preserved within the high southern latitude marine shelf succession of the la meseta formation on seymour island off the ne side of the antarctic peninsula 87 sr 86 sr ratios of bivalve shell carbonate indicate that the la meseta formation spans virtually the entire eocene and suggest the presence of an early middle eocene unconformity paleoclimatic and paleoceanographic inferences are based on the stable oxygen and carbon isotope values of two genera of bivalves collected with a high degree of stratigraphic resolution within the formation and with multiple replicate samples from each horizon 18 o data indicate roughly 10 c of cooling from the early eocene climatic optimum 15 c through the end of the eocene minimum 5 c much of which took place in two comparatively short intervals at ca 52 and ca 41 ma many features of the isotope curves generated from this eocene shelf section are apparent in 18 o and 13 c data from the southern and global oceans including warm intervals that likely correspond to the early and middle eocene climatic optima eeco and meco a rapid middle eocene shift to much more positive values is the most signifi cant in the section and refl ects a drop to universally cooler temperatures in the late middle and late eocene that might also be associated with a short lived glacial advance however even using a somewhat depleted value for 18 o of seawater in the antarctic peninsular region average seymour island shelf water paleotemperatures did not reach freezing before the end of the eocene 13 c data similarly refl ect the documented middle eocene surface ocean enrichment followed by more negative values but depletion is much more pronounced on seymour island and persists for the remainder of the eocene suggesting a combination of upwelling metabolic effects and or atypical carbon cycling on the shelf in this region isotope data capture information about changes in the paleoenvironment that also had consequences for the biota as published paleontological records document marked change in the nature of terrestrial and marine biota at this time the fact that middle eocene cooling and biotic turnover in the peninsular region correspond well in time to the proposed initial opening of drake passage suggests that the formation of gateways in addition to changes in pco 2 had signifi cant consequences for the earth s climate system during the paleogene

age and structure of the shyok suture in the ladakh region of northwestern india implications for slip on the karakoram fault system a precise age for the collision of the kohistan ladakh block with eurasia along the shyok suture zone ssz is one key to understanding the accretionary history of tibet and the tectonics of eurasia during the india eurasia collision knowing the age of the ssz also allows the suture to be used as a piercing line for calculating total offset along the karakoram fault which effectively represents the se border of the tibetan plateau and has played a major role in plateau evolution we present a combined structural geochemical and geochronologic study of the ssz as it is exposed in the nubra region of india to test two competing hypotheses that the ssz is of late cretaceous or alternatively of eocene age coarse continental strata of the saltoro molasse mapped in this area contain detrital zircon populations suggestive of derivation from eurasia despite the fact that the molasse itself is deposited unconformably onto kohistan ladakh rocks indicating that the molasse is postcollisional the youngest population of detrital zircons in these rocks approximately 92 ma and a u pb zircon date for a dike that cuts basal molasse outcrops approximately 85 ma imply that deposition of the succession began in the late cretaceous this establishes a minimum age for the ssz and rules out the possibility of an eocene collision between kohistan ladakh and eurasia our results support correlation of the ssz with the bangong suture zone in tibet which implies a total offset across the karakoram fault of approximately 130 190 km

intermittent euxinia in the high latitude james ross basin during the latest cretaceous and earliest paleocene abstract seymour island in the james ross basin antarctica contains a continuous succession of latest cretaceous sediments deposited in a shallow marine environment at high latitude making it an ideal place to study environmental changes prior to the k pg mass extinction we measured major and trace elements and conducted petrographic analysis of two sections from the maastrichtian danian lopez de bertodano formation of seymour island several lines of evidence point to intermittently anoxic to euxinic conditions during deposition including the presence of pyrite framboids with a size distribution suggesting syngenetic formation in the water column and enrichments in several trace elements including molybdenum arsenic copper zinc and chromium molybdenum enrichments are clearly associated with enrichments in manganese and authigenic iron suggesting shuttling of redox sensitive trace elements across a chemocline that fluctuated across the sediment water interface comparisons with modern systems suggest relatively high frequency redox variability possibly over approximately annual timescales which may be related to the annual cycle of polar sunlight and associated seasonal changes in primary productivity glauconitic horizons are associated with more reducing conditions including at the k pg boundary though this does not appear to be a uniquely euxinic interval similar degrees of trace element enrichment are seen in other highly glauconitic intervals while euxinia may have contributed to low diversity in the lowermost rotularia units redox conditions do not seem to have been the primary control on the transition to a mollusc dominated fauna in the latest maastrichtian redox conditions show little to no response to the eruption of the deccan traps or maastrichtian climatic changes instead intermittent euxinia appears to have been a characteristic feature of this high latitude environment during the cretaceous paleogene transition

antarctic peninsula and south america patagonia paleogene terrestrial faunas and environments biogeographic relationships abstract the eocene of seymour island contains the only association of cenozoic plants and land vertebrates known from anywhere in antarctica and lies at about latitude 63 south the late early to latest eocene la meseta formation fills an incised valley and comprises sediments representing deltaic estuarine and very shallow marine environments the paleogene sequence in southern south america patagonia and the antarctic peninsula reveals floristically distinct periods late paleocene early and middle eocene and latest eocene based largely on leaf assemblages the late paleocene cross valley flora seymour island contains ferns and other elements suggesting a much warmer climate than at this latitude today the middle eocene fossil hill south shetland islands and the rio turbio santa cruz province southern patagonia floras have a mixture of both neotropical and antarctic elements the la meseta paleoflora is distinctive in having a predominance of antarctic taxa especially nothofagus podocarps and araucarian conifers in the eocene deciduous and evergreen forests this suggests a cooling trend during the eocene of antarctica with mid to late eocene seasonal cool temperate rainy climates and latitudinal and altitudinal gradients the seymour island la meseta fauna cucullaea allomember middle eocene contains at least 10 mammal taxa predominantly tiny marsupials mostly endemic and new taxa the endemism of these marsupials suggests the existence of some form of isolating barrier climatic and or geographic during the eocene faunal similarity between the la meseta fauna and the fauna assigned to the riochican late paleocene south american land mammal age of patagonia strongly suggests that the former derived from the latter the occurrence on seymour island of sudamericids that had become extinct in south america in the paleocene also indicates that isolation may have allowed extended survival of this gondwanan group in the eocene of antarctica and the factors that caused their extinction did not affect this continent global warming and intercontinental dispersal have been major influences on the timing and magnitude of terrestrial biotic change in the late paleocene and early eocene epochs the faunistic evidence indicates that the la meseta mammalian fauna derived from late paleocene early eocene riochican vacan faunas the dispersal and vicariance events may have occurred during the onset of the climatic optimum of the cenozoic late paleocene early eocene when major regressive events are recorded either in the northern antarctic peninsula and southernmost patagonia between 58 5 and 56 5 ma the absence of notoungulates in the la meseta fauna is noteworthy we speculate that the notoungulates could have passed into antarctica during the latest part of the paleocene when the environmental conditions were warmer and then became extinct at the onset of the climatic deterioration during the early eocene

strontium isotope correlation of the basal maastrichtian stage in antarctica to the european and us biostratigraphic schemes new 87 sr 86 sr dating allows the correlation of a marker horizon within the prolific late cretaceous gunnarites antarcticus faunal assemblage of the cape lamb member snow hill island formation vega island antarctica with reference sections in europe and the usa this horizon is between 81 5 and 96 5 m above the base of the g antarcticus assemblage replicate analysis of six macrofossils from within it yielded a mean value for 87 sr 86 sr of 0 707 735 9 0 000 004 3 2 s e n 17 this ratio in turn yields a numerical age of 71 0 0 2 ma when compared to the standard 87 sr s6 sr reference curve for the latest cretaceous for which the campanian maastrichtian boundary is placed at 71 3 0 5 ma the value of 0 707 735 9 0 000 004 3 correlates to a level in the belemnella lanceolata belemnite zone of the chalk of northwestern germany that is 2 5 5 m beneath the base of the overlying b pseudobtusa zone and 7 5 m above the campanian maastrichtian belemnite boundary and to an interval within the ammonite zonation of the us western interior that spans the early maastrichtian baculites baculus and b eliasi zones but with a most likely level within the b eliasi zone an earliest maastrichtian age is thereby determined for the antarctic horizon and indeed for the entire g antarcticus assemblage gunnarites sensu lato is an important ammonite marker for the base of the maastrichtian throughout the southern high latitude regions and the associated large heteromorph ammonite diplomoceras may comprise a macrofossil link back to the maastrichtian type sections

latest cretaceous earliest paleogene vegetation and climate change at the high southern latitudes palynological evidence from seymour island antarctic peninsula abstract fluctuations in late cretaceous climate were already influencing biotic change prior to the environmental upheaval at the cretaceous paleogene k pg boundary but their general nature magnitude and timing remain controversial a high resolution dataset on terrestrially derived palynomorphs is presented from the high southern palaeolatitudes that unlocks details of small scale climate variability throughout this period of significant global change specifically this is a quantitative spore and pollen analysis of an expanded uppermost cretaceous to lowermost paleogene maastrichtian earliest danian shallow marine sedimentary succession from seymour island off the northeastern tip of the antarctic peninsula then as now located at 65 s using nearest living relatives the first detailed vegetation habitat and climate reconstruction is presented for the emergent volcanic arc at this time on the coastal lowlands a cool to warm temperate rainforest is envisaged growing in a riverine landscape with both wet river margin pond and relatively dry interfluve canopy gap habitats diverse podocarps and southern beech trees grew alongside angiosperm herbs and shrubs in mean annual temperatures of 10 15 c higher altitude araucarian forests gave way to open ericaceous heathland beyond the tree line in subalpine to alpine conditions with mean annual temperatures of a cold 5 8 c there is no exact modern botanical equivalent but the closest modern flora is that of the andes of southern chile and argentina maastrichtian climate is shown to have fluctuated from cool humid conditions through a rapid warming 2 million years prior to the k pg transition followed by cooling during the earliest danian a trend supported by previous work on this interval

collision tectonics in the nw himalayas west himalayan tectonics involve the collision of microplates between the indian and asian plates the kohistan complex consists largely of tightly folded basic volcanics and sediments generated as late jurassic to late cretaceous island arcs these were intruded by post folding mid cretaceous eocene plutonics produced from continued subduction of the indian plate after closure of a suture between kohistan and the karakorum the himalayan structures show major thrust sheets and the kohistan arc is essentially a crustal pop up with southward upright and northward verging structures developed above a thick ductile decoupling zone the indus suture which can be traced for 100 km beneath kohistan on large reentrants this pop up formed by a two stage process closure of the northern suture followed by closure of the southern indus suture granitic rocks of the kohis tan ladakh batholith dated at 100 40 ma post date most of the structures related to the northern suture but were deformed and carried southwards on shear structures related to the indus suture postcollisional deformation carried this kohistan complex on deep decoupling zones over the indian plate on a series of imbricated gneiss sheets the thrusts climbing up section in the movement direction so that in the far s some override their own molasse debris folds above these deep decoupling zones deformed their overlying thrust sheets into large antiforms i e the nanga parbat and hazara syntaxes the nanga parbat syntaxis probably formed due to a shear couple near a branch line where one of the main himalayan thrusts joined the indus suture beneath kohistan crustal delamination to produce the imbricated gneiss sheets could not account for all the displacement of india into asia suggested by palaeomagnetic data there must also have been lateral displacement as demonstrated by the large oblique slip shear zone in the hunza valley n of kohistan

the paleocene of antarctica dinoflagellate cyst biostratigraphy chronostratigraphy and implications for the palaeo pacific margin of gondwana abstract the paleocene 66 56 ma was a critical time interval for understanding recovery from mass extinction in high palaeolatitudes when global climate was warmer than today a unique sedimentary succession from seymour island antarctic peninsula provides key reference material from this important phase of the early cenozoic dinoflagellate cyst data from a 376 m thick stratigraphical section including the cretaceous paleogene boundary is correlated with biozones from new zealand the east tasman plateau and southeastern australia a detailed age model is suggested for the lopez de bertodano ldbf and sobral sf formations based on dinoflagellate cyst biostratigraphy and u pb dating of zircons supported by correlated magnetostratigraphy and strontium isotope values from macrofossils the top of the ldbf is confirmed as latest maastrichtian to earliest danian 66 2 65 65 ma in age the overlying sf is mostly danian in age with an inferred hiatus near the top overlain by sediments dated as late thanetian rare apectodinium homomorphum first appear in the uppermost sf the earliest in situ record from antarctica the distribution of marine and terrestrial fossils from uppermost cretaceous to eocene sediments in patagonia antarctica new zealand and australia required both sea and land connections between these fragments of gondwana fossil evidence and reconstructions of antarctic palaeogeography and palaeotopography reveal evidence for persistent embayments in the proto weddell and ross sea regions at this time we conclude that a coastal dispersal route along the palaeo pacific margin of gondwana could explain the fossil distribution without requiring a transantarctic strait or closely spaced archipelago a region in the west to east antarctic boundary zone elevated until the early paleogene perhaps acted as a site for high elevation ice caps this supports fossil geochemical and sedimentological evidence for cold climate intervals and significant sea level falls during the maastrichtian and paleocene

early cretaceous subvolcanic calc alkaline granitoid magmatism in the nubra shyok valley of the shyok suture zone ladakh himalaya india evidence from geochemistry and u pb shrimp zircon geochronology abstract the lithounits constituting the ladakh himalaya are exposed along the indus and shyok sutures zones of northwest himalaya the shyok suture zone ssz in northern ladakh represents a highly tectonized zone of a back arc basin which is mainly composed of volcano sedimentary formations shyok and khardung formations intimately associated with intrusive granitoids in the nubra shyok valley of the ssz calc alkaline granitoids of batholithic dimension are exposed in the tirit region referred herein as the tirit granitoids which are intrusive evidently into the shyok volcanic rhyolite rocks belonging to the shyok formation in this valley the northern margins of granitoids of the ladakh batholith can also be found intrusive into the metasediments shale slate and metavolcanics of the shyok formation the compositions and crystallization pressures 66 to 91 mpa of amphiboles in the intrusive tirit granitoid corroborate a calc alkaline nature and solidification of tirit granitoid melt at subvolcanic level equivalent to a minimum of 2 5 km to a maximum of 3 5 km thick overburden of shyok volcanics u pb shrimp zircons from the tirit granitoids have yielded mean crystallization ages of 109 4 1 1 ma and 105 30 0 80 ma which strengthen the idea of early cretaceous subduction beneath the karakoram terrain inherited older zircon cores 278 393 ma 476 519 713 952 ma and 1933 ma suggest a contribution from heterogeneous palaeozoic and proterozoic sources in the generation of the tirit granitoids similar to those observed elsewhere in the karakoram kohistan region a mean crystallization age 105 30 0 80 of zircons in the tirit granitoid hosting xenoliths of porphyritic volcanics places a minimum eruption age of ca 105 ma for the shyok volcanics the ladakh granitoid tirit granitoids and porphyritic volcanic xenolith belong to a calc alkaline series a mean crystallization age 67 32 0 66 ma for zircon in the ladakh granitoid implies that the shyok metasediments shale slate were deposited and metamorphosed prior to ca 68 ma present and earlier determined ages on tirit granitoids revealed that the subduction related calc alkaline magmatism in the nubra shyok valley of the ssz prevailed between 110 and 68 ma and hence a minimum age of early cretaceous can be suggested for development of the ssz

late cretaceous emplacement of the indus suture zone ophiolitic melanges and an eocene oligocene magmatic arc on the northern edge of the indian plate we report three40ar 39ar dates on stratigraphically located samples of 82 6ma from a syenite cutting the indus suture zone ophiolitic melange and about 39 and about 45 ma from granodiorite intrusions north of the suture zone sedimentological observations indicate eocene to miocene deposition of coarse clastics by very large braided and meandering streams in a continental back arc setting these observations suggest that the ophiolitic melanges of the indus suture zone were emplaced in the late cretaceous shortly after a major change in plate motions in the indian ocean they further suggest that an andean type magmatic arc developed on the northern edge of the indian plate during the eocene and oligocene

beach ridge development in lake michigan shoreline behavior in response to quasi periodic lake level events abstract strandplains of arcuate beach ridges are common in coastal embayments in parts of the great lakes similarities in beach ridge development and geomorphology are recognizable in many of the embayments in the lake michigan basin despite differences in size and shape available sediment type and supply predepositional slope and topography and hydrographic regime between the embayments these similarities are primarily a product of three scales of quasiperiodic lake level variation ranging in time from 30 to 600 years and in water level change from 0 5 to 3 7 m the interaction of these three lake level variations can be represented on a curray 1964 diagram rate of water level change versus rate of sediment supply the position of any shoreline on the diagram and the type of behavior the shoreline is experiencing is a product of the interaction of the three variations two large strandplains of late holocene beach ridges occur at opposite ends of lake michigan toleston beach and thompson embayment the two areas exhibit similar patterns of beach ridge development for the past 2600 calendar years that is both areas form beach ridges about every 30 years groups of 4 to 6 beach ridges reflect a longer term lake level variation of about 150 years only during the largest variation of about 600 years in duration do the two areas differ the rise to the 1700 cal yr b p high caused the erosion of beach ridges back to 2800 cal yrs b p in northern lake michigan in southern lake michigan no erosion occurred during this lake level high differences in shoreline development between the two areas are related to the rate of sediment supply to the shorelines as the sediment sink for the southern half of lake michigan the southern strandplain received a greater sediment flux than the northern strandplain during the latter part of the late holocene and produced a continuous record of beach ridge development

the yarlung zangbo paleo ophiolite southern tibet implications for the dynamic evolution of the yarlung zangbo suture zone the yarlung zangbo suture zone a major geological structure in tibet is well known as the locus of tectonic emplacement of the tethyan ophiolites current models propose that most of the east tethyan oceanic lithosphere was subducted within a single subduction zone active during the middle or late cretaceous which was completed during the paleogene collision between india and asia the early cretaceous sedimentary giabulin formation in southern tibet includes conglomeratic members that contain ultramafic and mafic plutonic pebbles as well as radiolarian chert clasts that record the erosion of oceanic lithosphere involved in a subduction event which occurred earlier than previously believed geochemical analyses mineral chemistry stratigraphic chronology and sedimentary analysis including source provenance suggest that the pebbly conglomerate was formed through erosion of an unknown ophiolitic source that was geochemically distinguishable from the xigaze ophiolites within the yarlung zangbo suture zone southern tibet we infer the existence of an older ophiolitic source termed the yarlung zangbo paleo ophiolite that was dismembered and eroded during an earlier subduction stage not taken into account in current models q 2000 elsevier science ltd all rights reserved

carbon isotope δ13c differences between late cretaceous ammonites and benthic mollusks from antarctica abstract ammonites are one of the most common fossils of the mesozoic but there is little consensus on their mode of life isotopic studies have been used to reconstruct their preferred water temperature from 18 o measurements but 13 c values have more ambiguous interpretations previous studies have recorded population differences in 13 c values between ammonite and benthic organisms without explaining the cause in detail here we examine a molluscan community from seymour island antarctica and find a 4 carbon isotope offset between ammonites and other benthic mollusks the most likely cause of this anomaly is an increased metabolic carbon contribution to ammonite shell material when compared with other mollusks but we cannot rule out the possibility of a methane seep contribution increased respired co 2 production could be generated by a more active lifestyle and increased energy demands which may have increased the susceptibility of ammonites to the end cretaceous mass extinction

late cretaceous cenozoic climatic variations of the northern antarctic peninsula new geochemical evidence and review aptian to pliocene time series of x ray fluorescence data from the antarctic peninsula are used to assess the degree of chemical weathering and maturity of sediments deposited prior and subsequent to the establishment of glaciation in west antarctica a continuous palaeoclimatic signal is inferred from comparing the results with previously published palaeotemperature and palaeobotanical data aptian cenomanian warm cool and santonian early paleocene warm cold cycles were followed by the global late paleocene early eocene climatic optimum subsequent steady decline in temperatures resulted in glacial conditions in the northern antarctic peninsula by early oligocene time under alternating cenozoic frigid cold climates and in sedimentary regimes dominated by physical weathering geochemical signatures were primarily indicative of provenance the development of cretaceous arboreal vegetation in the northern antarctic peninsula can be correlated with the major climatic cycles

middle to late holocene landscape changes and geoarchaeological implications in the marshes of the dives estuary nw france abstract holocene palaeogeographic changes in the lower dives valley a small estuarine system in normandy france have been investigated using a combination of facies interpretation from borehole cores 14c dating and pollen analysis the palaeoenvironmental record is broadly similar to that of other coastal and estuarine systems along the english channel but exhibits specific features in comparison with large estuarine and coastal systems especially as regards the narrow lower valley and its margins the identified environments included uniform tidal 6800 5500 2200 2000 cal bp freshwater fen 5500 3300 cal bp and drained floodplain 300 0 cal bp in contrast landscape variability was high during the periods 3300 2300 and 1900 300 cal bp in relation to gradients in environmental conditions from downstream to the upper reaches of the valley a significant palaeogeographic change between ca 3000 and 2200 cal bp indicates that episodes of strong coastal hydrodynamic forcing notably storm events may have had dramatic consequences with significant implications for human activities the pollen diagrams show evidence of the opening up of woodland in order to develop pastures and agriculture on the edges of the freshwater marsh during the bronze age 4500 2800 cal bp although the settlement patterns remain unknown because of the sparse archaeological discoveries related to this period during the iron age increased land use in the valley bottom had a significant impact on the environment from the iron age to the late roman period 2800 1500 cal bp the dramatic change caused by marine flooding and the large size of the tidal environment favoured the development of salt extraction sites from the coast to the inner estuary from the early middle ages restricted tidal influences and the progressive silting of the valley bottom by overbank deposits enabled a lasting change with the development of pastureland and the miscellaneous exploitation of the various environments finally after the 17th century the systematic reclamation and drainage of the wetland produced marked changes inducing in particular a significant loss of landscape and ecological diversity in this regard the pattern of land use in the middle ages probably represents an example of sustainable landscape exploitation

geological evidence against the shyok palaeo suture ladakh himalaya evolution of the ladakh himalaya is related to the cretaceous tertiary subduction of the indian oceanic plate below the southern margin of the eurasian plate along the indus suture zone1 11 the plate tectonic reconstruction suggests two stages of subduction due to the presence of a pre cretaceous suture along the shyok valley12 13 this hypothesis is based on there being ophiolite belts in the indus and shyok valleys the indus suture zone is well established but there have been insufficient data on the shyok suture to confirm the existence of the palaeo suture i have studied the saltoro hills in the western part of the shyok valley and report here the salient geological features with a few exceptions the igneous and sedimentary rocks indicate that the indus and shyok sutures had the same cretaceous oligocene history however the volcanic eruption during the deposition of post oligocene molasse in the saltoro hills of the shyok valley is the youngest igneous activity in the whole of the ladakh himalaya hence the geological evidence described here does not accord with the theory of palaeo suture

high benthic methane flux in low sulfate oceans evidence from carbon isotopes in late cretaceous antarctic bivalves abstract the shell material of marine benthic bivalves provides a sensitive archive of water chemistry immediately above the sediment water interface which in turn is affected by sedimentary geochemistry and redox reactions sulfate has a major controlling effect on sedimentary carbon cycling particularly the processes of methane production and oxidation with lower concentrations of sulfate likely resulting in an increase in sedimentary methane production whilst it is accepted that ocean sulfate varied markedly across the phanerozoic evidence of changes in methane production in sediments has so far been lacking there is potential for the oxidation products of sedimentary methane to be preserved and detected in marine fossils here we present the results of high resolution carbonate isotope records from two taxa of well preserved shallow infaunal bivalve lahillia and cucullaea collected from the marine shelf succession across the cretaceous paleogene k pg boundary in seymour island antarctica the succession has pre existing subtle indications of more abundant methane and the time period is characterized by much lower marine sulfate concentrations than modern these shell carbonate carbon isotope records vary widely at one extreme shells have typical average values and small ranges compatible with a contemporaneous marine dissolved inorganic carbon dic source and modern style sedimentary carbon cycling at the other the shells have large amplitude annual cycles of carbon isotopic variability of up to 23 8 within a single year of growth and shell carbonate 13 c compositions as negative as 34 shells with these increased ranges and unusually negative values are found at discrete intervals and across both bivalve taxa the contribution of methane required to explain the most negative carbonate carbon isotopic values in the bivalve shells is extremely high between 30 to 85 of bottom water dic based on mass balance calculations records of organic carbon isotopes from the same succession remained between 26 1 and 21 7 throughout suggesting that methane influence was restricted to bottom waters a lack of authigenic carbonate in the section indicates that methane oxidation progressed aerobically and may have provided a significant driver for transient bottom water de oxygenation where methane addition is indicated the seasonal sensitivity precludes control by methane hydrates we argue that these data represent the increased importance and sensitivity of methanogenesis in the sediments enabled by lower ocean sulfate concentrations during the late cretaceous the tendency towards a more dynamic role for marine methane production and oxidation is likely to apply to other times of low marine sulfate in earth s history

tectonic framework of the indus and shyok suture zones in eastern ladakh northwest himalaya abstract three different phases of plutonic volcanic activity viz 1 1 cretaceous volcanics of the dras and luzarmu formations 2 2 early tertiary granitoids of the ladakh plutonic complex 3 3 oligocene acid volcanics and dykes of the khardung formation have been recognised in the ladakh magmatic arc the dras formation of the indus suture zone and the luzarmu formation of the shyok suture zone were one stratigraphic unit into which granitoids of the ladakh plutonic complex intruded the rocks of the shyok suture zone are interpreted to represent the tectonised remainder of a marginal back arc basin the closure of the marginal basin occurred at the eocene oligocene time boundary and crustal shortening was responsible for generation of neogene 2 mica granites of the karakoram plutonic complex and regional metamorphism of the pangong tso group

extinction patterns δ18 o trends and magnetostratigraphy from a southern high latitude cretaceous paleogene section links with deccan volcanism although abundant evidence now exists for a massive bolide impact coincident with the cretaceous paleogene k pg mass extinction event 65 5 ma the relative importance of this impact as an extinction mechanism is still the subject of debate on seymour island antarctic peninsula the lopez de bertodano formation yields one of the most expanded k pg boundary sections known using a new chronology from magnetostratigraphy and isotopic data from carbonate secreting macrofauna we present a high resolution high latitude paleotemperature record spanning this time interval we find two prominent warming events synchronous with the three main phases of deccan traps flood volcanism and the onset of the second is contemporaneous with a local extinction that pre dates the bolide impact what has been termed the k pg extinction is potentially the sum of multiple independent events at least at high latitudes

quaternary geological mapping of the lowlands of the netherlands a 21st century perspective old borehole descriptions modern lithostratigraphical classification and geostatistics have been combined in recent geological mapping in the netherlands recent developments in geostatistics and the increased computing capacity of personal computers enable three dimensional geological mapping based on already available data the data originate from a mapping programme at the scale of 1 50 000 that was started in the 1950s by the national geological survey rijks geologische dienst although started on a lithostratigraphical basis the increased use of radiocarbon dates since the 1950s influenced the map legend the map units were largely defined by age boundaries that were supposed to coincide with transgressions and regressions more recent research revealed that not only sea level but also regional basin topography sediment supply and regional neo tectonics are important factors controlling coastal development the netherlands institute of applied geoscience tno national geological survey the successor of the rijks geologische dienst recently redefined the classification of holocene coastal and alluvial deposits in a purely lithostratigraphical way the old borehole descriptions contain purely lithological descriptions as well as interpretations that were derived from those descriptions the larger part of the originally defined map units represents boundaries that characterise a change in lithology by returning to the original lithological descriptions the borehole data and the geological maps are applicable in the new lithostratigraphical framework they are now used in modern three dimensional geological mapping modelling of the subsurface these models are very useful for applied geological research 2004 elsevier ltd and inqua all rights reserved

a tectonic model reconciling evidence for the collisions between india eurasia and intra oceanic arcs of the central eastern tethys abstract despite several decades of investigations inferences on the timing and nature of collisions along the mesozoic cenozoic eurasian margin remain controversial we assimilate geological and geophysical evidence into a plate tectonic model for the india eurasia collision that includes continuously closing topological plate polygons constructed from a time dependent network of evolving plate boundaries with synthetic plates constructed for now subducted ocean floor including back arc basins that formed on the southern eurasian margin our model is regionally constrained and self consistent incorporating geophysical data from abyssal plains offshore west australia and east antarctica including jurassic age data from offshore northwest australia limiting much of northern greater india to a 1000 km long indenter originally reaching to the wallaby zenith fracture zone southern eurasia and southeast asia are riddled with dismembered oceanic arcs indicating long lived tethyan intra oceanic subduction this intra oceanic subduction system was well established from cretaceous time in the india eurasia convergence zone in the neotethys which was consumed during greater india s northward trajectory towards eurasia from the early cretaceous fragments of obducted oceanic crust within the yarlung tsangpo suture zone between india and eurasia predominantly date to the late jurassic or mid cretaceous barremian aptian the various ophiolites along strike and a hiatus in subduction related magmatism during the tithonian aptian suggest that there was at least one generation of intra oceanic arc formation whose plate boundary configuration remains uncertain paleomagnetic and magmatic studies suggest that the intra oceanic arc was at equatorial latitudes during the early cretaceous before subduction resumed further north beneath the eurasian margin lhasa terrane with another hiatus in subduction related magmatism along southern lhasa during 80 65 ma possibly as the back arc spreading centre approached the active andean style margin in our model greater india collided with the tethyan intra oceanic arc in paleocene eocene time finally closing the tethyan seaway from mid late eocene time which is consistent with the age of the youngest marine deposits found between india and eurasia geological evidence from the collision zone indicates an age of initial arc continent collision by 52 ma followed by the soft initial continent continent collision between india and eurasia by 44 2 ma this timing is supported by marine geophysical data where the spreading centres in the indian ocean record a drastic decline in seafloor spreading rates and changes in spreading directions first at 52 ma followed by another reorganisation at 43 ma the abandonment of spreading in the wharton basin and the onset of extrusion tectonics in asia by 36 ma are likely indicators of hard complete continent collision and highlight the multi stage collisional history of this margin our continuously evolving network of mid ocean ridge and subduction zone geometries and divergence convergence vectors through time provide a basis for future refinements to assimilate new data and or test alternative tectonic scenarios

patterns of biodiversity and faunal rebound following the k t boundary extinction event in austral palaeocene molluscan faunas palaeocene molluscan faunas are characterised by complex evolutionary histories following the cretaceous tertiary k t boundary extinction event and exhibit dramatic distinct signatures of composition and biodiversity levels relating to extinction and post extinction recovery processes this paper is the first to document and survey the entire palaeocene record of the southern hemisphere which comprises at least 515 recorded molluscan taxa from australia new zealand chatham islands antarctica and south america the record is much richer than previously recognised the k t boundary event was a prime mechanism of change for the composition of palaeocene faunas but palaeocene diversity patterns were shaped also by the final break up of gondwana concomitant changes in climate and in oceanic circulation and faunal recovery processes the flip flop in diversity of bivalves and gastropods across the k t boundary stems from a rapid evolutionary burst of speciation in the danian for gastropods especially carnivorous forms with planktotrophic development which infilled ecospace vacated by the extinction in the southern hemisphere fossil record deposit feeders were less affected by the extinction event and seemingly more extinction resistant but other important factors related to stratigraphic range and spectrum of life habits habitats affected survivorship success suspension feeders especially epifaunal forms were hard hit by the extinction but had bounced back within a few million years by late danian time at the latest but at lower diversity than during the late cretaceous the extinction was not as marked in most southern regions as reflected in the antarctic record in the antarctic k t boundary interval diversity drops suddenly ca 50 m before the boundary and while suspension feeders remain at low diversity for at least 300 kyr gastropods still dominate the molluscan assemblages most of the k t boundary molluscan survivors were bivalve species 66 and all of these were members of representative genera that displayed extensive stratigraphic and geographic ranges in the cretaceous or earlier in the mesozoic the majority of earliest danian antarctic molluscs belong to newly evolved species within surviving genera 58 but by late danian time this trend had changed to a dominance of new species in new genera many new groups arose during the palaeocene especially by late danian time and these faunas are highly distinctive at both genus and species level for example the wangaloa formation fauna of late danian age ca 63 61 ma is dominated by new species in new genera ranging in values from 62 5 to 81 a systematic catalogue of all known palaeocene austral species is presented herein in the appendix for the first time with details of formation recorded age and inferred life habits

the indus tsangpo suture zone in ladakh northwest himalaya further palaeomagnetic data and implications abstract a total of 81 samples 244 specimens from upper cretaceous indus molasse and middle to upper cretaceous dras flyschoids of the indus tsangpo suture zone in ladakh northwest himalaya has been studied by thermal demagnetization methods both formations showed a characteristic magnetization component indicative for equatorial to low northern palaeolatitudes of acquisition similar palaeolatitudes have been obtained before from secondary magnetization components of early tertiary age in the ladakh intrusives and in the tibetan sedimentary series of central nepal the present characteristic components are interpreted likewise as secondary magnetizations which stabilized between 50 and 60 m y ago during greater india s collision with asia s southern margin the dras flyschoids show another magnetic component which in case of primary origin indicates acquisition at a low southern palaeolatitude if correct this interpretation supports recent suggestions for late cretaceous obduction of an island arc on greater india s northern margin

the age and nature of mesozoic tertiary magmatism across the indus suture zone in kashmir and ladakh n w india and pakistan we report the following new40ar 39ar ages 130 150 and 90 100 ma from monzodiorite and tremolite actinolite schist of the kohistan complex 44 0 5 39 7 0 2 ma from dikes cutting the ladakh deosai batholith complex 130 145 ma from a diorite in the shyok melange and 7 8 0 1 ma from a late stage monzogranite of the karakorum batholith a 261 13 ma age from gneiss of the karakorum batholith is of uncertain significance

strontium isotope profiles across k t boundary sequences in denmark and antarctica strontium isotope profiles derived from minimally altered samples across marine k t boundary sequences exposed at kjolby gaard and nye klov denmark and on seymour island antarctica show neither the boundary excursions nor the boundary spikes in 87sr 86sr that have been reported for k t boundary sequences from elsewhere nor do our data conform to modelled predictions of the sr isotopic response of the oceans to a positive spike in 87sr 86sr at the terminal cretaceous boundary values for 87sr 86sr with 95 confidence intervals are 0 707828 3 in denmark and 0 707832 7 in antarctica our data suggest that 87sr 86sr stopped increasing and started decreasing at least 90 ka before the k t boundary

the transhimalaya gangdese plutonism in the ladakh region a upb and rbsr study abstract the age and origin of the transhimalaya gangdese plutonic belt in the ladakh area has been studied by high resolution u pb analyses of accessory minerals zircon and monazite allanite and rb sr measurements on whole rock samples the ages determined of 101 2m y for a granodiorite and of 60 7 0 4m y for a granite substantiate that the transhimalaya plutonism was active at least in mid cretaceous albian and earliest tertiary palaeocene times a rb sr isochron of 73 4 2 4m y might be fortuitous because the rb sr systematics shows important heterogeneities on the whole rock scale the inherited radiogenic lead in zircon demonstrates that anatexis of continental crust was involved in magma genesis the thus recycled continental material was heterogeneous with respect to its primary ages and or metamorphic history the approximate minimum ages of the continental sources range from 350 to 590 m y the 101 2m y old transhimalaya granodiorite which intrudes a series of mainly basaltic island arc rocks dras series shows that this island arc was attached to the continental margin at that time this is consistent with the hypothesis that the ladakh tethys closed through two subduction regimes 1 an early cretaceous subduction which formed the dras island arc and 2 a late cretaceous to palaeocene subduction at the continental margin which caused the emplacement of the transhimalaya plutonic belt

terminal cretaceous environmental events the geologic record of terminal cretaceous environmental events indicates that iridium and other associated elements were not deposited instantaneously but during a time interval spanning some 10 000 to 100 000 years the available geologic evidence favors a mantle rather than meteoritic origin for these elements these results are in accord with the scenario of a series of intense eruptive volcanic events occurring during a relatively short geologic time interval and not with the scenario of a single large asteroid impact event

40ar 39ar dating of volcanic rocks of the shyok suture zone in north west trans himalaya implications for the post collision evolution of the shyok suture zone abstract 40 ar 39 ar geochronological studies carried out on the khardung volcanics of ladakh india and our earlier ar ar results from the volcanics of the shyok suture along with the available geological and geochemical data provide good constraints for post collision evolution of the shyok suture zone whole rock samples from the shyok volcanics yielded disturbed age spectra and we have demonstrated earlier that the youngest tectonic event in the shyok suture zone responsible for the thermal disturbance of these samples is karakoram fault activation at 14 ma contrastingly whole rock samples from the khardung volcanics which are in tectonic contact with these shyok volcanics and are exposed in the form of thick rhyolitic and ignimbritic flows yielded undisturbed age spectra and good plateau ages the whole rock plateau ages of two rhyolite samples are 52 8 0 9 and 56 4 0 4 ma we interpret these ages to be the time and duration of emplacement of these volcanics over thickened margin of the continental crust which appears to be coeval with the initiation of the collision between the indian and asian plate the lesser extent of post emplacement isotopic re equilibration in these samples unlike the shyok volcanics indicate that these samples were present in different tectonic settings away from the karakoram fault at the time of deformation in the shyok suture zone we propose that the two volcanic belts of contrasting nature were brought together in juxtaposition by the karakoram strike slip faulting at 14 ma

endemism and heterochroneity in the late cretaceous campanian to paleocene palynofloras of seymour island antarctica implications for origins dispersal and palaeoclimates of southern floras

continental rift to back arc basin jurassic cretaceous stratigraphical and structural evolution of the larsen basin antarctic peninsula the larsen basin developed in jurassic times as a result of continental rifting during the early stages of gondwana break up lower upper jurassic non marine sedimentary and volcanic rocks constitute a syn rift megasequence recording initial largely amagmatic extension and subsequent widespread extension related silicic volcanism a succeeding kimmeridgian early berriasian transgressive megasequence consisting largely of anoxic dysoxic hemipelagic mudstones is thought to have been deposited during a thermal subsidence phase when relative magmatic quiescence and peak jurassic eustatic sea levels served to maximize sediment starvation the fragmentary record for late berriasian barremian times suggests that a regressive megasequence may have developed in the earlier part of this period recording increased sediment yield to the larsen basin from the increasingly emergent antarctic peninsula arc subsequently strata in the southern but not the northern part of the basin underwent relatively intense eastward verging deformation possibly during the formation of a retro arc fold thrust belt where exposed the lower part of the succeeding aptian eocene megasequence consists of a deep marine clastic wedge deposited along the fault bounded western basin margin during a phase of arc uplift and related differential subsidence following partial basin inversion in late cretaceous times regression took place as reduced basinal subsidence rates allowed shallow marine facies to prograde basinward

palynofacies as indicators of paleoenvironmental changes in a cretaceous succession from the larsen basin james ross island antarctica abstract in order to reconstruct the paleoenvironment of one of the most extensive marine cretaceous successions in the southern hemisphere palynofacies analyses were conducted on 83 samples from the whisky bay albian turonian hidden lake coniacian and santa marta santonian campanian formations in the larsen basin james ross island antarctica categories of particulate organic matter were counted and investigated by cluster analysis the trends and parameters of palynofacies constituents were used to reconstruction paleoenvironments based on the existing sedimentological interpretation the stratigraphic distribution of the four identified palynofacies associations a d reflects a continuous terrestrial influx throughout the succession from base to top a conspicuous increase in woody elements especially non opaque particles is observed this increase in continental elements occurs despite the presence of marine elements this finding corroborates the sedimentological interpretation of a deeper water paleoenvironment during deposition of the whisky bay formation and initiation of a shallowing upward trend in the hidden lake formation culminating with shallow marine shelf environment of the santa marta formation

maastrichtian climate productivity and faunal turnovers in planktic foraminifera in south atlantic dsdp sites 525a and 21 abstract stratigraphic faunal and isotopic analyses of the maastrichtian at dsdp sites 525a and 21 in the south atlantic reveal a planktic foraminiferal fauna characterized by two major events an early late maastrichtian diversification and end maastrichtian mass extinction both events are accompanied by major changes in climate and productivity the diversification event which occurred in two steps between 70 5 and 69 1 ma increased species richness by a total of 43 and coincided with the onset of major cooling in surface and bottom waters and increased surface productivity the onset of the terminal decline in maastrichtian species richness began at 67 5 ma and the first significant decline in surface productivity occurred at 66 2 ma coincident maximum cooling to 13 c in surface waters and the reduction of the surface to deep temperature gradient to less than 5 c major climatic and moderate productivity changes mark the mass extinction and the last 500 kyr of the maastrichtian between 200 and 400 kyr before the k t boundary surface and deep waters warmed rapidly by 3 4 c and cooled again during the last 100 kyr of the maastrichtian surface productivity decreased only moderately across the k t boundary species richness began to decline during the late maastrichtian cooling and by k t boundary time the mass extinction had claimed 66 of the species viewed within the context of maastrichtian climate and productivity changes the k t mass extinction could have resulted from extreme environmental stress even without the addition of an extraterrestrial impact

does large igneous province volcanism always perturb the mercury cycle comparing the records of oceanic anoxic event 2 and the end cretaceous to other mesozoic events mercury hg is increasingly being used as a sedimentary tracer of large igneous province lip volcanism and supports hypotheses of a coincidence between the formation of several lips and episodes of mass extinction and major environmental perturbation however numerous important questions remain to be answered before hg can be claimed as an unequivocal fingerprint of lip volcanism as well as an understanding of why some sedimentary records document clear hg enrichment signals whilst others do not of particular importance is evaluating the impact of different volcanic styles on the global mercury cycle as well as the role played by depositional processes in recording global hg cycle perturbations here new mercury records of cretaceous oceanic anoxic event 2 oae 2 94 ma and the latest cretaceous 67 66 0 ma are presented oae 2 is associated with the emplacement of multiple predominantly submarine lips the latest cretaceous with subaerial volcanism of the deccan traps both of these connections are strongly supported by previously published trends towards unradiogenic osmium os isotope values in globally distributed sedimentary records hg data from both events show considerable variation between different locations attributed to the effectiveness of different sediment types in registering the hg signal with lithologically homogeneous records documenting more clear hg enrichments than sections with major changes in lithology such as limestones to claystones or organic rich shales crucially there is no geographically consistent signal of sedimentary hg enrichment in stratigraphic records of either oae 2 or the latest cretaceous that matches os isotope evidence for lip emplacement indicating that volcanism did not cause a global hg perturbation throughout the entire eruptive history of the lips formed at those times it is suggested that the discrepancy between os isotope and hg trends in records of oae 2 is caused by the limited dispersal range of hg emitted from submarine volcanoes compared to the global scale distribution of os a similar lack of correlation between these two proxies in uppermost cretaceous strata indicates that although subaerial volcanism can perturb the global hg cycle not all subaerial eruptions will do so these results highlight the variable impact of different volcanogenic processes on the efficiency of hg dispersal across the globe factors that could influence the impact of lip eruptions on the global mercury cycle include submarine versus subaerial volcanism volcanic intensity or explosivity and the potential contribution of thermogenic mercury from reactions between ascending magma and surrounding organic rich sediments

late cretaceous antarctic fish diversity new material from the santa marta formation late coniacian early maastrichtian of james ross island contributes significantly to the current knowledge of late cretaceous antarctic fish diversity the taxon list for the santa marta formation is extended and new records of neoselachians and teleosts are reported the stratigraphic ranges of some previously known taxa are enlarged and the palaeobiogeography and palaeoecology of late cretaceous antarctic fishes are discussed top predators that occupied the higher levels in the food chain along with marine tetrapods dominate the marine faunas from the santa marta and lopez de bertodano formations the only fish adapted to crushing hard shelled invertebrates were the chimeroids rays an important component of marine fish associations as well as fish from lower trophic levels remain unknown from the late cretaceous of antarctica

provenance environmental and paleogeographic controls on sandstone composition in an incised valley system the eocene la meseta formation seymour island antarctica abstract the eocene la meseta formation is the youngest exposed unit of the back arc james ross basin antarctic peninsula cropping out in seymour marambio island the formation comprises 720 m of clastic sedimentary rocks of deltaic estuarine and shallow marine origin it was subdivided into six unconformity based units valle de las focas acantilados campamento cucullaea i cucullaea ii and submeseta allomembers grouped into three main facies associations facies association i represents valley confined deposition in a progradational aggradational tide dominated and wave influenced delta front delta plain environment facies association ii includes tidal channels mixed tidal flats tidal inlets and deltas washover and beach environments facies association iii represents nonconfined tide and storm influenced nearshore environments la meseta formation sandstones are quartzofeldspathic with some hybrid arenites glauconite and carbonate bioclasts rich sandstone detrital modes are subdivided into two distinctive petrofacies the low quartz petrofacies petrofacies i q 12 interpreted to retain the original provenance signal and the high quartz petrofacies petrofacies ii q 55 and l 1 4 is clearly dominated by volcanic derived clasts it developed at times of high sea level and or during later stages of the valley fill when an energy fence at the shoreline prevented delivery of sediment from the antarctic peninsula thus enhancing the relative participation of local volcanic sources

a high resolution record of environmental changes from a cretaceous paleogene section of seymour island antarctica a high resolution sedimentological and palynological study was performed in combination with biomarker based organic geochemical temperature proxies tex86 and mbt cbt on a 7 4 m thick continuous section straddling the cretaceous paleogene k pg boundary at seymour island at the northern tip of the antarctic peninsula the k pg interval of the seymour island section was deposited in a deltaic estuarine system with considerable sedimentary input from the erosion of a distant volcanic arc at the antarctic peninsula combined with ash fallouts from explosive volcanic eruptions the maastrichtian interval represents the prodelta of a delta prograding in a marginal marine setting whereas the paleocene interval was deposited in more open shallow marine conditions following sea level rise and shoal submergence above the k pg boundary dinocyst biostratigraphy indicates that in the studied section the k pg boundary is represented by a gentle erosive surface 30 cm below a partially indurated marker sandstone bed the dinoflagellate assemblages show quantitative changes across the boundary representatives of manumiella group together with abundant palambages dominate the assemblages in the lower part of the section i e below the k pg boundary there is an evident peak of fibrocysta ifecysta cordosphaeridium just above the boundary in the upper part of the section senegalinium reaches relatively high abundance together with impletosphaeridium clavus while relatively high concentrations of soil derived organic matter inhibit the use of the tex86 paleothermometer to reconstruct sea surface temperatures the mbt cbt paleothermometer indicates warm mean annual air temperatures for the latest cretaceous 16 0 16 5 c these high temperatures coinciding with the lowest abundance of the high latitude pollen taxon nothofagidites may reflect the terminal cretaceous deccan traps warming pulse fluctuating temperatures followed in the early paleocene characterized by 2 degrees drop in air temperatures coincident with the maximum percentage of the high latitude angiosperm nothofagidites spp and the cold water dinocyst taxon impletosphaeridium clavus the recognition of ecological signals of disturbances and their relationship with short term climatic and environmental changes provides new insights related to the effect of the impact at the high latitude k pg boundary of antarctica

additions to the diversity of elasmosaurid plesiosaurs from the upper cretaceous of antarctica abstract three specimens of elasmosaurid plesiosaurs sauropterygia plesiosauria from upper cretaceous beds of antarctica are described here these include postcranial remains of a single adult individual recovered from late maastrichtian beds of marambio seymour island possessing a distinctive combination of features cervical vertebrae having centra with a triangular outline in transverse section a vertical groove on the rostral and caudal edge of the neural spines and a deep articulation over the neural arch for the following postzygapophysis while the scapula shows an unusually large and anteriorly recurved dorsal process this combination of features is unknown in any adult postcranial elasmosaurid genus recovered to date in the upper cretaceous of the weddellian biogeographic province and could represent a new form additional specimens from james ross island comprise the first record of an aristonectinae plesiosauria elasmosauridae in late campanian beds being the oldest known record of this sub family finally a third specimen from the same age and locality reveals the presence of very long necked elasmosaurids with affinities to typical representatives from the upper cretaceous of the northern hemisphere these findings add to the known diversity of upper cretaceous elasmosaurids in high latitudes of the southern hemisphere

evolution and extinction of maastrichtian late cretaceous cephalopods from the lopez de bertodano formation seymour island antarctica one of the most expanded records to contain the final fortunes of ammonoid cephalopods is within the lopez de bertodano formation of seymour island james ross basin antarctica located at 65 south now and during the cretaceous this sequence is the highest southern latitude onshore outcrop containing the cretaceous paleogene k pg transition we present comprehensive new biostratigraphic range data for 14 ammonite and one nautiloid species based on the collection of 700 macrofossils from high resolution sampling of parallel sedimentary sections dated maastrichtian to earliest danian in age across southern seymour island we find evidence for only a single abrupt pulse of cephalopod extinction at the end of the cretaceous when the final seven ammonite species disappeared consistent with most evidence globally in the lead up to the k pg extinction in the james ross basin starting during the campanian ammonite diversity decreased overall but the number of endemic taxa belonging to the family kossmaticeratidae actually increased this pattern continued into the maastrichtian and may be facies controlled linked to changes in sea level and seawater temperature during the early maastrichtian ammonite diversity dropped significantly with only two species recorded from the basal lopez de bertodano formation on seymour island the subsequent diversification of endemic taxa and reappearance of long ranging widespread species into the basin resulted in an increase in ammonite diversity and abundance during the mid maastrichtian this was coincident with an apparent period of warming temperatures and sea level rise interpreted from palynology and sedimentology perhaps reflecting a high latitude expression of the mid maastrichtian event late maastrichtian diversity levels remained stable despite reported climatic and environmental variation ammonite diversity patterns during the maastrichtian parallel those of microfossil species such as nannofossil and planktonic foraminifera suggesting that dynamic climatic and environmental changes affected many planktonic and nektonic organisms during the latest cretaceous however we suggest that these perturbations had a minimal effect on overall diversity prior to the catastrophic extinction event at the k pg boundary

business as usual drilling predation across the k pg mass extinction event in antarctica abstract a survey of 759 predatory drill holes in late cretaceous and paleogene molluscan and serpulid worm prey from seymour island antarctica has allowed exploration of the effects of the k pg mass extinction on predator prey dynamics at this high latitude site circular holes 0 62 6 41 mm in diameter suggesting a large gastropod predator most probably vanikoropsis arktowskiana occur throughout the study interval analysis suggests that the driller was a catholic predator capable of attacking a range of prey types showing some degree of size and stereotypic handling behaviour although there were changes in prey choice across the extinction event these reflect changes in available prey and in particular limited options immediately post extinction there were no significant changes in failure rate prey effectiveness over the mass extinction our findings suggest that at this site for this particular predator aside from menu choice predation dynamics post extinction was business as usual

paleobiogeography of the cretaceous western interior seaway of north america the vertebrate evidence abstract distribution patterns of marine vertebrates of the cretaceous western interior seaway of north america are analysed in a biogeographical context the analysis is based on fossil vertebrate assemblages from the following lower campanian localities 1 anderson river fauna n w t 2 pembina fauna southern manitoba 3 sharon springs fauna south dakota wyoming 4 niobrara fauna kansas 5 mooreville fauna alabama due to the cosmopolitan nature of many marine vertebrates relative abundance is used in preference to presence absence data in identifying faunal distribution patterns the analysis demonstrates the presence of two faunal subprovinces in the seaway the northern interior subprovince is characterized by a low diversity in all groups and is dominated by plesiosaurs hesperornithiforms and the mosasaur platecarpus the southern interior subprovince is characterized by a high diversity in all groups and is dominated by sharks turtles and the mosasaur clidastes these biogeographical subdivisions support the hypothesis of warm temperature and cool temperate zones in the seaway that have been proposed on the basis of invertebrate faunas

a new gis approach for reconstructing and mapping dynamic late holocene coastal plain palaeogeography the geomorphological development of holocene coastal plains around the world has been studied since the beginning of the twentieth century from various disciplines resulting in large amounts of data however the overwhelming quantities and heterogeneous nature of this data have caused the divided knowledge to remain inconsistent and fragmented to keep improving the understanding of coastal plain geomorphology and geology cataloguing of data and integration of knowledge are essential in this paper we present a gis that incorporates the accumulated data of the netherlands coastal plain and functions as a storage and integration tool for coastal plain mapped data the gis stores redigitised architectural elements beach barriers tidal channels intertidal flats supratidal flats and coastal fresh water peat from earlier mappings in separate map layers a coupled catalogue style database stores the dating information of these elements besides references to source studies and annotations regarding changed insights using scripts the system automatically establishes palaeogeographical maps for any chosen moment combining the above mapping and dating information in our approach we strip the information to architectural element level and we separate mapping from dating information serving the automatic generation of time slice maps it enables a workflow in which the maker can iteratively regenerate maps which speeds up fine tuning and thus the quality of palaeogeographical reconstruction the gis currently covers the late holocene coastal plain development of the netherlands this period witnessed widespread renewed flooding along the southern north sea coast coinciding with large scale reclamation and human occupation our gis method is generic and can be expanded and adapted to allow faster integrated processing of growing amounts of data for many coastal areas and other large urbanising lowlands around the world it allows maintaining actual data overview and facilitates new ways of analysis at national regional and local scales 2016 elsevier b v

crustal growth and two stage india eurasia collision in ladakh abstract the post palaeozoic history of crustal growth between india and the karakoram lhasa accreted southern margin of asia begins with the creation of the oceanic crust during the northward drift of the karakoram lhasa block away from the northern margin of india after permo triassic rifting data suggest initiation of northward subduction and the development of the island arc close to the southern margin of asia sometime in upper jurassic 160 m y the northward retreat of the overriding eurasian plate due to movements along transform faults which subsequently changed into transcurrent faults resulted in the opening of the shyok back arc basin in the kohistan ladakh region during pre upper cretaceous time the mature and thickened tholeiitic island arc lying between the subducting indian plate and the spreading shyok back arc basin suffered compression deformation emplacement of ophiolitic melanges and metamorphism during the upper cretaceous 80 m y the intrusion of the calc alkaline magma into the deformed rocks of the island arc and the back arc basin during the paleocene eocene 60 40 m y was followed by explosive calc alkaline volcanism 40 25 m y resulting in further crustal growth in this part of the trans himalaya the collision of the dras island arc with the approaching margins of the indian and eurasian plates took place in two stages in the first stage it collided with the northern margin of india during the paleocene along the indus suture the final collision of the island arc accreted northern margin of india with the eurasian plate took place along the shyok suture during the early oligocene 30 m y

karakoram fault zone rocks cool in two phases the karakoram fault zone of ladakh india is a major strike slip boundary along which the tectonic evolution of tibet has been accommodated in this paper 40 ar 39 ar isotopic age data are integrated with structural and metamorphic data to infer an exhumation history for granites and low to intermediate grade metamorphic rocks exposed adjacent to two strands of the fault zone near tangtse leucogranites which crystallized c 17 ma ago are cut by the karakoram fault zone indicating that fault movement was initiated subsequent to 17 ma the 40 ar 39 ar data give temperature time histories which indicate that the two phases of rapid cooling of karakoram fault zone rocks are evident one at c 17 ma to c 13 ma and another following an intervening period of relatively slow cooling starting at c 8 ma and continuing until at least 7 ma uplift since c 17 ma via dextral oblique thrusting has resulted in exhumation from amphibolite facies metamorphic conditions possibly with a larger thrust component from 17 to 13 ma followed by a change to dominant strike slip motion at about 13 ma rapid cooling starting at c 8 ma at greenschist facies temperatures is probably the result of renewed oblique thrusting it is notable that the two episodes of rapid cooling recorded in karakoram fault zone rocks coincide with episodes of exhumation in the pakistani karakoram and also in southern tibet

the palaeoclimatic significance of cenozoic marine macrofossil assemblages from cape roberts project drillholes mcmurdo sound victoria land basin east antarctica abstract the cape roberts project crp drilled three sedimentary cores at 77 00 s and 163 7 e about 12 14 km east of cape roberts mcmurdo sound in the ross sea east antarctica the total crp recovery consists of about 1500 m of cenozoic strata and 100 m of paleozoic age beacon supergroup rocks as many as 594 horizons produced macrofossils that prove to be significant to understand past ross sea depositional environments and contribute new information about antarctic climate in particular the cape roberts project opened important windows on the paleoclimatic history of east antarctica during the early pleistocene early miocene and oligocene the early pleistocene carbonate unit in crp 1 holds a truly polar macrofauna but also documents a peculiar interglacial climatic event with strongly reduced seasonal sea ice formation in the ross sea the early miocene crp 1 and crp 2 2a and late oligocene macrofossil assemblages crp 2 2a and crp 3 are consistent with cold water environments and may be interpreted to indicate sub polar conditions the early oligocene assemblages contain modiolid mussels that are definitely not truly polar and suggest significantly warmer than present seawater conditions although definitely colder than during the middle upper eocene known in james ross basin and mcmurdo erratics finally the suggestion that crp reached upper eocene strata is considered possible on the base of an undescribed modiolid mussel found at the bottom of pre beacon sediments in the crp 3 drill core

collision tectonics in the himalaya as evidenced by the indus and shyok rock assemblages abstract the himalayan orogeny is closely associated with the tectonic developments which occurred along the indus suture zone during the last decade many new data on sediment stratigraphy and volcanic plutonic suites have been obtained these data have been interpreted in terms of plate tectonics the meso tethys was generated following the permo triassic rifting and spreading during the jurassic the tethys ocean is postulated in accordance with geophysical data to have been consumed during northward subduction along the indus suture resulting in the himalayan orogeny through collision between india and eurasia however the nature of tectonic processes and their chronology appear to be different in the western and eastern himalayan segments in the western himalaya subduction in an island arc setting and eocene collision are evident mainly by the occurrence of the island arc dras volcanics the sangeluma group srikantia and rajdhan 1980 trench deposits ophiolitic blocks older 60 m y calc alkaline plutons and blueschist facies rocks the indus group srikantia and rajdhan 1980 continental deposits and the younger

mid cretaceous stratigraphy of the james ross basin antarctica the extensive cretaceous sedimentary sequence exposed within the james ross basin antarctica is critical for regional stratigraphic correlations in the southern hemisphere and also for our understanding of the radiation and extinction of a range of taxonomic groups however the nature and definition of cenomanian turonian strata on the nw margins of james ross island has previously been difficult due both to marked lateral facies changes and to stratigraphical discontinuities within the extensive whisky bay formation facies variation and local unconformities were the result of fault controlled deep marine sedimentation along the basin margin in this study the albian cenomanian boundary is defined for the first time in the upper levels of the lewis hill member of the whisky bay formation however there is a cenomanian late turonian unconformity between the lewis hill and brandy bay members of the whisky bay formation equivalent lithostratigraphical units exposed further to the sw on james ross island appear to be more complete with the early cenomanian late turonian interval represented by the upper parts of the tumbledown cliffs and the lower part of the rum cove members of the whisky bay formation the turonian coniacian boundary is provisionally placed at the junction between the whisky bay and hidden lake formations the revised stratigraphic ages for this section show that the late cretaceous radiations of a number of major plant and animal groups can be traced back to at least the turonian stage this raises the possibility that their dissemination might be linked to the global cretaceous thermal maximum

metamorphism and tectonics of the himalaya metamorphism connected with the main growth and deformation stages of the himalaya ranges from mid cretaceous to the quaternary northward subduction gave rise in the early to mid cretaceous to an island are complex with greenschists amphibolites granulites and blueschists in the w kohistan ladakh and an andean type margin with greenschist amphibolite grade metamorphism in the e india and tibet ophiolitic nappes were thrust southwards over the indian continental margin in the palaeogene during the final stages of closure of the southern arm of tethys the indus zangbo suture bifurcates westwards and between the two sutures lies the kohistan ladakh island arc which was converted to an andean type arc in the palaeocene eocene the karakorum range underwent northward subduction at least during the late cretaceous to give rise to a complex and prominent calc alkaline batholith post collisional southward thrusting of crustal slabs over the indian continental margin took place in the early miocene with production of high grade metamorphism inverted isograds and crustal melt granites later southward thrusting in the pliocene to quaternary gave rise to localized low grade recrystallization against the thrusts

evolutionary patterns in macrurous decapod crustaceans from cretaceous to early cenozoic rocks of the james ross island region antarctica

phanerozoic plate boundaries in mainland se asia the himalayas and tibet recently available geological data on tibet yunnan and burma facilitate recognition of phanerozoic subduction systems and two continental fragments of gondwanaland which extend through mainland se asia a cambrian subduction system and 5 mesozoic early caenozoic collision belts are identified in the region indochina eastern thailand and central tibet accreted to china in the early triassic western se asia and s tibet separated from gondwanaland in the permian or early triassic and collided with asia in the late triassic and the western burma island arc system collided with asia in the jurassic upper triassic flysch and schist in the eastern indoburman ranges were accreted to western burma in the jurassic early cretaceous during eastward subduction and formation of a back arc thrust belt following collision of greater india with arc complexes to the n in the cretaceous and with tibet in the early eocene western burma moved northwards about 450 km along the sagaing namyin ridge thrust transform fault formation of the 3 major belts of tin granites and the porphyry copper deposits in the region took place in specific tectonic settings within the subduction systems and collision belts

comet showers as a cause of mass extinctions if at least some mass extinctions are caused by impacts why do they extend over intervals of one to three million years and have a partly stepwise character the solution may be provided by multiple cometary impacts astronomical geological and palaeontological evidence is consistent with a causal connection between comet showers clusters of impact events and stepwise mass extinctions but it is too early to tell how pervasive this relationship may be

stratigraphy and structure of the indus suture in the lower swat pakistan nw himalaya abstract we present a geological map detailed structural description and new subdivisions of the indus suture zone lithologies in northeast pakistan lower swat region the indus suture zone is a dominantly fore arc related assemblage obducted onto the indian plate initial southward thrusting was followed by the reactivation of the indus suture as a ductile brittle normal fault significant strike slip faulting may have taken place at this stage later brittle reverse faults demonstrate that shortening outlasted normal faulting the comparison of the structural evolution of the indus suture zone and the indian plate shows that both terrains were sharing the deformational history possibly since the earliest stage of collision the lower swat area records a full orogenic cycle from early rifting through continent arc collision to orogenic collapse we present a geodynamic model that integrates all these elements

restoration and evolution of the intermontane indus molasse basin ladakh himalaya india abstract collision of the indian plate with the karakorum plate lhasa block during the eocene ca 55 50 ma created predominantly a s or sw verging thrust culmination across the himalaya during the late tertiary two molasse basins existed the siwalik bain formed in the late miocene to present on the indian foreland south of the himalaya and the mid eocene to late miocene indus basin along the indus suture zone north of the high himalaya the indus basin is approximately 2000 km long extending eastwards from ladakh across south tibet a balanced cross section along the zanskar river shows a minimum 36 km shortening in the eocene late miocene molasse and suggests that the minimum basin width was approximately 60 km in ladakh more than 2000 m of post eocene alluvial fan fluvial and fluvio lacustrine sediments accumulated in the ladakh sector with petrographies suggesting derivation mainly from the deeply dissected and uplifted northern granodioritic ladakh batholith aptian eocene with only minor amounts of debris derived from the deformed southern tethyan passive margin palaeocurrents show predominant e w axis parallel sediment transport with subordinate lateral input paths being preserved the indus molasse basin is deformed by numerous post eocene n directed backthrusts many of which cut the entire stratigraphy and therefore were active at least into late tertiary times

iridium and dinocysts at the cretaceous tertiary boundary on seymour island antarctica implications for the k t event a single iridium anomaly 40 times background concentration correlated with the cretaceous tertiary k t boundary is present within an interval of unconsolidated glauconitic silty sands in a marine clastic sequence on seymour island antarctic peninsula dinocysts provide the basis for biostratigraphic identification of a 20 30 cm k t transitional interval calcareous microfossils have not been preserved in the glauconitic beds dinocysts also record an earliest danian transgressive event 10 cm above the transition interval the ir spike is near the base of the dinocyst transition interval and 30 cm below the flooding horizon the seymour island site located at a high latitude 63 s at the end of the cretaceous provides no compelling evidence for mass extinction at the k t boundary

tectonic events reflected by palaeocurrents zircon geochronology and palaeobotany in the sierra baguales of chilean patagonia abstract the sierra baguales situated north of the torres del paine national park in the magallanes region of southern chile shows a well exposed stratigraphic sequence ranging from the late cretaceous to late pliocene which presents a unique opportunity to study the evolution of sedimentological styles and trends palaeoclimate changes and tectonic events during this period the depositional environment changed from a continental slope and shelf during the cenomanian campanian tres pasos formation to deltaic between the campanian maastrichtian dorotea formation and estuarine in the lutetian bartonian man aike formation during the rupelian a continental environment with meandering rivers and overbank marshes was established rio leona formation this area was flooded in the early burdigalian estancia 25 de mayo formation during the patagonian transgression but emerged again during the late burdigalian santa cruz formation measured palaeocurrent directions in this mesozoic cenozoic succession indicate source areas situated between the northeast and east southeast during the late cretaceous east southeast during the middle eocene and southwest during the early oligocene to early miocene this is confirmed by detrital zircon age populations in the different units which can be linked to probable sources of similar ages in these areas the east southeastern provenance is here identified as the antarctic peninsula or its northeastern extension which is postulated to have been attached to fuegian patagonia during the eocene the southwestern and western sources were exhumed during gradual uplift of the southern patagonian andes coinciding with a change from marine to continental conditions in the magallanes austral basin as well as a decrease in mean annual temperature and precipitation indicated by fossil leaves in the rio leona formation the rain shadow to the east of the andes thus started to develop here during the late eocene early oligocene 34 ma long before the quechua phase of andean tectonics 19 18 ma that is generally invoked for its evolution at lower latitudes

archaeology a major tool in the reconstruction of the coastal evolution of westergo northern netherlands abstract westergo is the name of the coastal area in the northern netherlands between the former tidal systems of marne and middelzee the area silted up and changed into a salt marsh area during the subatlantic 1000 bc 500 ad the history of seaward migration of the salt marshes in the area has been reconstructed with the help of the archaeologically dated settlements on dwelling mounds terps terps were constructed on the salt marshes when the process of silting had reached the stage of the middle marsh this zone is flooded less frequently than ca 50 days per year the construction of terps during the middle stage of marsh development is indicated by the thickness of the salt marsh deposits on which terps were built and by the diatoms found in these marsh deposits the oldest phase of terp settlement on the marshes of westergo is dated between the late bronze age and early iron age ca 600 bc and is found in the southern part of westergo the old land during the next period 500 bc 500 ad the funnel shaped tidal basin in the northern part silted up to the supratidal level the middle marsh zone in the funnel shaped basin expanded during this period 1000 years by ca 5 km at the western and eastern sides of the basin and by ca 10 km in the central part this implies a mean marsh extension in this former tidal basin of ca 5 10 m per year in this paper a reappraisal of the nature and genesis of the salt marsh ridges of the northern netherlands is presented

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

campanian maastrichtian cretaceous stratigraphy of the james ross island area antarctica one of the most important outcrops of uppermost cretaceous campanian maastrichtian sedimentary rocks in the southern high latitudes occurs within the james ross island group northeastern antarctic peninsula these rocks comprise a 1500 2000 m thick sequence of predominantly shallow marine clastic sediments that were deposited within a retro arc basin they are virtually undeformed and have yielded prolific invertebrate and vertebrate faunas and a wide range of plant taxa campanian maastrichtian strata are contained within two component formations of the upper cretaceous lower tertiary marambio group the lower santa marta formation is approximately 1100m thick and has three constituent members ammonites within the santa marta formation indicate an early to late campanian age assignment dinoflagellates suggest that the lower levels of the formation may range into the santonian stage in the northern james ross island to vega island region there is a conformable transition into the overlying lopez de bertodano formation here the basal cape lamb member is unconformably overlain by the sandwich bluff member although there are some lithological and fauna1 discrepancies which are attributed to marked lateral facies changes across the basin it is believed that the cape lamb member can be correlated with the lower to middle regions of the 1200 m thick sequence of undifferentiated lopez de bertodano formation lithologies exposed on seymour island molluscan data indicate a late campanian palaeocene age range for this upper formation dinoflagellates again suggest that the lowest beds may be slightly older the correlation presented provides the basis for a formal subdivision of the campanian and maastrichtian stages in the southern high latitudes it has also revealed two major basin shallowing events in the late campanian early maastrichtian and latest maastrichtian respectively and the existence of a major fault fault zone across southeastern james ross island the improved temporal framework will aid late cretaceous palaeoclimatic and palaeobiological studies in antarctica

subannual stable isotope records reveal climate warming and seasonal anoxia associated with two extinction intervals across the cretaceous paleogene boundary on seymour island antarctica

a new hesperornithiform aves specimen from the late cretaceous canadian high arctic with comments on high latitude hesperornithiform diet here we describe a new hesperornithiform specimen from the upper cretaceous kanguk formation of devon island nunavut canada this specimen nuvf 286 is referred to cf hesperornis sp based on size and shape of femora and teeth preserved with other skeletal elements previous osteohistologic analyses indicate a subadult ontogenetic stage at the time of death this new cf hesperornis specimen includes the first teeth associated with a high latitude hesperornithiform allowing for comments on the trophic behavior of these birds paleoecological reconstructions based on current knowledge of polar assemblages and comparisons to modern birds suggest that high latitude hesperornithiform birds may have had more varied diets than previously assumed

middle cretaceous back arc formation and arc evolution along the asian margin the shyok suture zone in northern ladakh nw himalaya abstract the shyok suture zone of the ladakh palaeovolcanic arc is made of cretaceous volcanosedimentary formations intruded by granodioritic plutons field observations show a tectonic stacking of litho units from different volcanic arc and back arc environments in the western part skardu area the shyok suture zone can be subdivided into two groups 1 the northern group which consists of olistolith basaltic blocks and tuffs the basalts are lree depleted with a lile enrichment and a slight nb depletion suggesting a back arc basin origin 2 the southern group which consists predominantly of andesites that show lree enrichment a flat hree pattern strong nb ta depletion and lile enrichment the volcanic rocks of the southern group appear to have island arc tholeiite iat to calc alkaline affinities in the eastern part of the suture zone nubra shyok area albian to cenomanian age silicoclastic sediments predominate these sediments correspond to a large detrital platform built on the northern part of the ladakh arc at the top these sediments interlayer with basaltic to andesitic lavas these lavas appear to be more differentiated and calc alkaline in nature than the skardu southern group lavas but show similar volcanic arc affinities no evidence of a back arc basin was found in this area our data from these two areas shows a northwest southeast evolution from back arc to arc formations in northern ladakh opening of this back arc basin occurred on the northwestern side of the ladakh arc this back arc was progressively closing eastward the arc itself was more mature in the east resembling the southern tibetan continental arc and was characterised by more continental sedimentation subsequent himalayan tectonometamorphic evolution closure of the back arc basin and deformation along the shyok suture reflects an early asymmetrical geometry along the asian margin and kohistan ladakh arc

stratigraphy and vertebrate paleoecology of upper cretaceous lowest paleogene strata on vega island antarctica the upper cretaceous maastrichtian sandwich bluff member of the lopez de bertodano formation is well exposed on vega island in the james ross basin off the northeastern coast of the antarctic peninsula although this unit is one of the richest sources of end cretaceous vertebrate fossils in antarctica it is also one of the least sedimentologically and stratigraphically characterized units in the basin new facies and stratigraphic analyses of the sandwich bluff member and the underlying cape lamb member of the snow hill island formation were performed in tandem with intensive prospecting for fossil vertebrates and stratigraphic assessment of historic paleontological localities on vega island this effort has led to a revised stratigraphy for the sandwich bluff member and the precise stratigraphic placement of important terrestrial and marine vertebrate fossil localities facies analysis reveals a fining and shallowing upward trend through the section that culminates in a newly recognized sequence boundary near the top of the sandwich bluff member followed by the deposition of a previously unrecognized 6 m thick matrix supported pebble cobble conglomerate of probable alluvial origin immediately overlying this unit well developed thalassinoides burrow networks in fine grained transgressive sandstones and siltstones indicate a rapid return to marine conditions a similar stratigraphic pattern is well documented at the top of the lopez de bertodano formation and the base of the overlying paleocene sobral formation on seymour island in the southern part of the basin although no fossils were recovered to constrain the age of the upper 10 15 m of the succession on vega island that preserves the newly recognized upper sequence boundary strata below this level can be confidently placed within the manumiella bertodano interval zone which extends to a short distance below the k pg boundary on seymour island hence based on sequence stratigraphic and lithostratigraphic evidence the uppermost 10 15 m of the succession on vega island may encompass the cretaceous paleogene boundary together with a few meters of the paleocene sobral formation