uncertainties in the relative positions of the australia antarctica lord howe and pacific plates since the late cretaceous we determined parameters that describe finite rotations and their uncertainty regions for relative plate motion at the spreading centers between the pacific and antarctica plates between australia and antarctica and between the lord howe rise and australia we combined these to yield a range of possible finite rotations describing the relative positions of the pacific australia antarctica and lord howe plates since the late cretaceous if the pacific australia plate boundary has had its present trend since anomaly 18 time reconstructions show 330 110 km of motion of the pacific plate relative to the lord howe rise since anomaly 5 time 9 8 m y 420 110 km since anomaly 6 time 19 5 m y 770 330 km since anomaly 13 time 35 6 m y and 820 260 km since anomaly 18 time 43 0 m y we examined two cases for times prior to anomaly 18 assuming a late cretaceous age of australia antarctica separation if a plate boundary existed between the lord howe rise and pacific plates since the late cretaceous with no plate boundary in antarctica reconstructions with the lord howe rise fixed predict 610 200 km of westward motion of the pacific plate between the times of anomalies 31 and 22 followed by 260 100 km of northward motion between the times of anomalies 22 and 18 if the lord howe rise was fixed to the pacific plate until the eocene but a plate boundary existed between east and west antarctica reconstructions show very little motion across this boundary between the times of anomalies 31 and 22 followed by convergence between the times of anomalies 22 and 18 this second case also brings 70 80 m y paleomagnetic poles from the pacific and east antarctica plates into better agreement than the first case but large uncertainties in the reconstructions do not allow the first case to be conclusively eliminated

late cretaceous cenozoic tectonic development of the southwest pacific region abstract a new model of the plate tectonic development of the southwest pacific integrates the continental geology of new zealand with the age structure of the surrounding oceanic crust revealed previously from magnetic anomaly lineations the model differs from previous ones in that the onland geology of new zealand is used to constrain the tectonic development in two important ways 1 the modern australia pacific plate boundary did not transect the new zealand sector until 23 million years ago 2 there has been a total of only c 500 km of dextral displacement on the plate boundary through new zealand the model is described with reference to a series of paleotectonic maps drawn to represent the setting at the times of anomalies 32 24 7 and 5 novel interpretations based on these reconstructions include the following during the late cretaceous the campbell fault was a continental transform fault between the tasman sea spreading centre and the bounty rift its 330 km of dextral displacement accompanying 25 of counterclockwise rotation of a campbell plateau block when the eastward propagating southeast indian ridge broke into the south tasman sea 57 million years ago it continued to propagate directly into southern south island and generated late eocene oligocene continental rifting through western new zealand at the same time back arc spreading in the norfolk basin caused continental rifting along a similar trend in western north island the australia pacific plate boundary originated as a transform fault between the southeast indian ridge and the pre existing kermadec trench it developed in response to the sudden cessation of spreading on the segment of the southeast indian ridge east of a fracture zone here named fracture zone z two implications arise from this model regarding the integrity of antarctica 1 1 during the cretaceous marie byrd land was probably no more than 200 km northwest of its present position 2 2 the proposition made in some earlier plate tectonic reconstructions that if the alpine fault did not form until after the late eocene there must be a late cretaceous early tertiary plate boundary within antarctica is most probably valid

late mesozoic bipolar bivalve faunas bipolar bivalve genera probably existed through the greater part of late mesozoic i e late jurassic late cretaceous time of the various theories put forward to account for their presence those based on some form of global climatic zonation seem most appropriate although equatorial polar temperature gradients were substantially less in late mesozoic time than at the present day high latitude regions were subjected to temperate or even cool temperate climatic regimes macro benthonic marine faunas may have been more susceptible to differentiation in response to these climatic patterns than nektonic ones this is particularly so in the late mesozoic strata of the southern hemisphere

the mineralogical diversity of alkaline igneous rocks critical factors for the transition from miaskitic to agpaitic phase assemblages geochemically the large family of alkaline plutonic rocks both qtz undersaturated and oversaturated compositions can be subdivided into metaluminous na 2 o k 2 o al 2 o 3 types in this paper we discuss two important aspects of the mineralogical evolution of such rocks with respect to their fe mg phases a major mineralogical transition observed is the precipitation of arfvedsonite or aegirine instead of fayalite or magnetite ilmenite the relative stability of these phases is controlled by oxygen fugacity and na activity in the crystallizing melts if na activity in the melt is high enough arfvedsonite aegirine form a common assemblage in peralkaline rocks under both reduced and oxidized conditions major mineralogical differences within this rock group exist with respect to their high field strength element hfse rich minerals most syenitic rocks known as miaskites contain zircon titanite or ilmenite as hfse rich minerals whereas in agpaites complex na k ca ti zr silicates incorporate the hfse similarly only a small group of peralkaline granites are found to lack zircon titanite or ilmenite but instead contain na k ca ti zr silicates here we present a detailed phase petrological analysis of the chemical parameters na 2 o cao k 2 o that influence the transition from miaskitic to agpaitic rocks based on the occurrence of ti and zr minerals several transitional mineral assemblages are identified and two major evolution trends for agpaites are distinguished a high ca trend which is exemplified by the alkaline rocks of the kola province russia and a ca depletion trend which is displayed by the alkaline rocks of the gardar province south greenland both trends show significant na enrichment during magmatic evolution high ca agpaites evolve from nephelinitic parental melts that did not crystallize large amounts of plagioclase in contrast agpaites showing ca depletion originate by extensive fractionation of plagioclase from basaltic parental melts in some peralkaline granites evolutionary trends are observed that culminate in agpaite like hfse mineral associations in the most evolved rocks

lower jurassic lower cretaceous belemnite biogeography and the development of the mesozoic boreal realm abstract the distribution of lower jurassic lower cretaceous belemnites is reviewed in the light of recent taxonomic and biogeographic studies and it is seen that belemnite provinciality developed in the late lower jurassic when distinct arctic taxa are first recognised in the middle jurassic boreal and tethyan belemnite realms are apparent the boreal realm being divisable into informal boreal atlantic and arctic provinces which can be recognised up into the lower cretaceous in the upper jurassic and lower cretaceous distinct arctic belemnites are found in association with tethyan ammonites in california and it is this factor in association with an observed increase in belemnite diversity northwards from the boreal atlantic to the arctic provinces that suggests that latitudinal temperature gradients were not the overall control influencing the development of boreal and tethyan belemnite realms instead the hostile environment of the boreal atlantic area the european archipelago is seen as an effective barrier to the migration of tethyan belemnites to the arctic and vice versa however high sea level stands may have helped blur these distinctions as in the late valanginian hauterivian when arctic taxa invaded europe and tethyan taxa the periphery of the arctic basin

coupled 1d quasi 2d flood inundation model with unstructured grids a simplified numerical model for simulation of floodplain inundation resulting from naturally occurring floods in rivers is presented flow through the river is computed by solving the de saint venant equations with a one dimensional 1d finite volume approach spread of excess flood water spilling overbank from the river onto the floodplains is computed using a storage cell model discretized into an unstructured triangular grid flow exchange between the one dimensional river cells and the adjacent floodplain cells or that between adjoining floodplain cells is represented by diffusive wave approximated equation a common problem related to the stability of such coupled models is discussed and a solution by way of linearization offered the accuracy of the computed flow depths by the proposed model is estimated with respect to those predicted by a two dimensional 2d finite volume model on hypothetical river floodplain domains finally the predicted extent of inundation for a flood event on a stretch of river severn united kingdom by the model is compared to those of two proven two dimensional flow simulation models and with observed imagery of the flood extents

polar glaciation and the genesis of ice ages one of the outstanding unresolved climatic questions concerns the cause s of ice ages over geological time1 2 a recurring theme in many hypotheses2 4 has been that land at high latitude is a necessary condition as snow accumulation on such land would accentuate local cooling via its albedo effect although the validity of these hypotheses has been queried5 they have been applied to the three most recent glacial periods namely the quaternary present the permo carboniferous 300 106 years ago and the ordovician 450 106 years ago the involvement of high latitude land has now been investigated with a general circulation model of the atmosphere and the results presented here indicate that sea ice is readily produced in the model at high latitudes regardless of the existence of land while land or at least very shallow seas may be necessary to promote glaciation it appears that polar glaciation is the norm rather than the exception for the earth thus no particular perturbation to the climatic system may be necessary to explain ice ages rather the problem may be one of accounting for the intervening periods of warmth the most promising solution to the latter problem is very large increases in the atmospheric co2 content

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

cretaceous paleogeography of antarctica abstract during the early cretaceous antarctica formed the center piece of a large landmass extending from south america across the southern latitudes to australasia the eastern sector of this austral landmass was dominated by broad craton consisting of east antarctica and australasia the western sector which was composed of the antarctic peninsula and southern south america consisted of a magmatic arc along a zone of subduction extending along the southeastern pacific west antarctica from the base of the antarctic peninsula to east antarctica consisted of several crustal blocks that are believed to have formed a land bridge between the magmatic arc and the craton marie byrd land and new zealand which were probably connected across the campbell plateau underwent a period of intense orogenic activity during the early cretaceous which was followed by an extended period of quiescence and erosion the late cretaceous heralded the final breakup of the southern continents and isolation of antarctica although rifting between australia and antarctica began in the jurassic and continued throughout the cretaceous the final separation of australia probably did not occur until the late eocene paleontologic and geophysical evidence indicate that new zealand became isolated from antarctica prior to the end of the cretaceous controversy exists as to the relationship of the antarctic peninsula with southern south america during the late cretaceous paleontologic data clearly shows that the plates were adjacent with active migration of terrestrial faunas taking place although faunal interchange between south america and the antarctic peninsula ceased during the early tertiary with the development of a shallow seaway complete separation of the two plates did not occur until development of deep sea conditions developed in the middle tertiary

dinosaurs on the north slope alaska high latitude latest cretaceous environments abundant skeletal remains demonstrate that lambeosaurine hadrosaurid tyrannosaurid and troodontid dinosaurs lived on the alaskan north slope during late campanian early maestrichtian time about 66 to 76 million years ago in a deltaic environment dominated by herbaceous vegetation the high ground terrestrial plant community was a mild to cold temperate forest composed of coniferous and broad leaf trees the high paleolatitude about 70 to 85 north implies extreme seasonal variation in solar insolation temperature and herbivore food supply great distances of migration to contemporaneous evergreen floras and the presence of both juvenile and adult hadrosaurs suggest that they remained at high latitudes year round this challenges the hypothesis that short term periods of darkness and temperature decrease resulting from a bolide impact caused dinosaurian extinction

an initial study of the sensitivity of modeled cretaceous climate to cyclical insolation forcing some cretaceous rhythmic sedimentation such as the colorado greenhorn formation deposited in the western interior seaway u s may have been produced by cyclic precipitation intensity change responding to orbitally produced insolation forcing to test this hypothesis a general circulation model was forced with the seasonal maximum and minimum insolation calculated from assumed cretaceous orbital parameters geographic comparisons for july and january of surface temperature surface pressure and precipitation were prepared for january maximum land sea contrast produced an increase of more than 6 mm day precipitation over the interior seaway however the july maximum simulation did not produce precipitation increase despite an anticipated monsoonlike circulation over the region north america appears to be very arid during cretaceous northern hemisphere summer

the mid cenozoic challenger rift system of western new zealand and its implications for the age of alpine fault inception analysis of the structure and sedimentary geology of western new zealand has identified a middle eocene to early miocene continental rift system 1 200 km long and 100 200 km wide named here the challenger rift system four phases of rift development occurred 1 infra rift subsidence 2 active axial trough subsidence 3 expanded rift subsidence involving collapse of the rift shoulders and 4 incipient sea floor spreading the spatial and temporal distribution of these phases identifies a north island and a south island rift segment and shows that rifting propagated toward the center of the rift from both ends the northern segment shows a simple pattern of rifting that is comparable with vink9s model of rift propagation the southern segment with locked zones and rift nucleation segments is comparable to courtillot9s model of rift propagation the sea floor spreading history of the southwest pacific shows that the northern rift segment probably linked with a sea floor spreading center in the norfolk basin and the southern segment linked with the southeast indian ridge this is corroborated by the good correlation between the ages of sea floor magnetic anomaly lineations that are aligned with the rift and the biostratigraphic ages of rifting the probable continuity of the rift system in its early development precludes pre miocene transcurrent displacement on the alpine fault an early miocene 23 m y b p age of alpine fault inception is indicated by the age and pattern of rift disruption attributed to compression that originated at the australia pacific plate boundary the modern australia and pacific plates were not discrete entities therefore until the early miocene

late cretaceous terrestrial vegetation a near polar temperature curve quantitative estimates of terrestrial paleotemperatures near the north pole were derived from the physiognomy of the vegetation including leaf margin analysis from rocks of latest albian and late cretaceous age of the north slope of alaska during the latest albian and cenomanian mean annual temperature was approximately 10 3 c during the coniacian mean annual temperature may have been 2 3 c warmer than during the albian cenomanian but no higher than 13 c during the campanian and maastrichtian mean annual temperature would have been about 2 8 c although the ranges for the individual estimates overlap differences among the floras indicate that the relative changes in mean annual temperature did occur

the effect of titanite and other hfse rich mineral ti bearing andradite zircon eudialyte fractionation on the geochemical evolution of silicate melts abstract we present trace element data for hfse rich minerals titanite eudialyte ti bearing andradite zircon from plutonic rocks of the eocene tamazeght complex high atlas mountains morocco in most lithologies significant amounts of titanite are present and as such titanite fractionation played a major role in the evolution of the hfse budget of the whole complex by combining our data with published titanite melt partition coefficients we explore the effects of titanite fractionation on the evolution of geochemical parameters zr hf nb ta la lu and th u ratios during differentiation of silicate melts in detail based upon this we further discuss the genetic relationships between the various rock types present in the tamazeght complex and show that the above mentioned element ratios can potentially be useful for distinguishing geochemically distinct melt reservoirs within a given plutonic rock suite zircon eudialyte and ti bearing andradite are generally rare or are restricted to localized rock units despite their scarcity each of them can have a significant effect upon the hfse budget in their evolving magmas here we derive first estimations of eudialyte melt partition coefficients for ree application of these data to eudialyte bearing rocks of the ilimaussaq complex south greenland and comparing the results to published estimations for the parental melts of these rocks yields consistent results and demonstrates the reliability of our estimations

two dimensional flood routing on steep slopes program routweir represents a two dimensional flood routing model designed to analyze two dimensional flow caused by rainfall and runoff flooding events input to the program consists of known geometry topography initial conditions and boundary conditions the geometry and bathymetry of the flood plain are represented by a grid of interconnecting triangular elements initial water levels are prescribed to correspond to the normal water elevations in the river channel boundary conditions are prescribed by a discharge hydrograph at the upstream boundary of the river basin and by the water surface elevations at the ocean boundary the interior water elevations and discharges are computed allowing flooding and drying to take place in the triangular elements of the grid based on a conservation of water volume equation and a surface slope dependent dynamic equation output consists of time histories of watersurface elevations and peak elevations in both tabular and graphical form routweir has been successfully calibrated against recorded flood levels in the rio culebrinas basin in puerto rico and has been used in that basin in a federal flood insurance study a versatile computer program routweir can be applied to many flood routing problems it is particularly suited for wide river basins with large bottom slopes and for normally dry areas subject to extensive flooding

alteration hfse mineralisation and hydrocarbon formation in peralkaline igneous systems insights from the strange lake pluton canada abstract two characteristics of peralkaline igneous rocks that are poorly understood are the extreme enrichment in hfse notably zr nb y and ree and the occurrence of fluid inclusions dominated by methane and higher hydrocarbons although much of the hfse enrichment can be explained by magmatic processes the common intense alteration of the parts of the peralkaline intrusions most enriched in these elements suggests that hydrothermal processes also play an important role in hfse enrichment likewise although the origin of the higher order hydrocarbons that occur as inclusions in these rocks is still debated there is strong evidence that at least in some cases their formation involved hydrothermal processes the issues of hfse enrichment and hydrocarbon formation in peralkaline intrusions are examined using data from the strange lake pluton a small middle proterozoic intrusion of peralkaline granite in northeast canada this pluton contains some of the highest concentrations of zr ree and y ever reported in an igneous body and is characterised by abundant hydrocarbon dominated fluid inclusions in rocks that have been hydrothermally altered including those that form a potential hfse ore zone we show that hfse at strange lake were partly concentrated to near exploitable levels as a result of their transport in a high salinity magmatic aqueous liquid and that this fluid coexisted immiscibly with a carbonic phase which reacted with hydrogen and iron oxides generated during the associated hydrothermal alteration to produce hydrocarbons via a fischer tropsch synthesis as a result hydrocarbons and hfse mineralization are intimately associated we then go on to show that hydrothermal alteration hfse mineralisation and hydrocarbons are also spatially associated in other peralkaline complexes and present a model to explain this association which we believe may be applicable to any peralkaline intrusion where hfse enrichment was accompanied by calcium metasomatism hematisation and hydrothermal fluorite we also suggest that even where these criteria are not satisfied hydrothermally enriched hfse and hydrocarbons will be intimately associated simply because they are products of the same initial magmatic fluid finally we speculate that the association of hfse and hydrocarbons may in some cases actually be genetic if as seems possible unmixing or effervescence of a reduced carbonic fluid from the original magmatic fluid caused changes in temperature ph f o 2 or the activity of volatile ligands sufficient to induce the deposition of hfse minerals

wadeite k2zrsi3o9 an alkali zirconosilicate from the saima agpaitic rocks in northeastern china its origin and response to multi stage activities of alkaline fluids abstract the triassic saima alkaline complex in the liaodong peninsula of northeastern china covers an area of about 20 km 2 and is dominated by nepheline syenite with phonolite at its center and a concealed body of eudialyte bearing nepheline syenite in the northwest of the complex the phonolite has similar features to miaskite while the nepheline syenites are classified in the agpaitic group according to their mineral assemblage and the alkalinity and aluminum saturation indexes zircon is the dominant zr bearing mineral in the phonolite whereas wadeite occurs as the only primary zr bearing mineral in the nepheline syenites the transitional crystallization from zircon to wadeite reveals an increase in alkalis and a high k na ratio as the magmas evolved from the volcanic to the intrusive stage the primary wadeite grains underwent varying degrees of hydrothermal alteration overall the areas of weak medium and strong alteration are characterized by the following respective associations 1 wadeite secondary catapleiite gaidonnayite 2 wadeite secondary catapleiite gaidonnayite zircon and 3 pseudomorphs after wadeite the pseudomorphs are widespread and mainly consist of residual wadeite secondary zircon catapleiite gaidonnayite k feldspar calcite and some zr bearing titanite and vesuvianite all of the secondary zircon grains in the three associations are typically enriched in ca and al compared with the primary ca free zircons of the phonolite the progressive alteration of wadeite suggests that the saima complex underwent multiple episodes of fluid activity during a hydrothermal stage including an initial na metasomatism via alkaline fluids then stages most likely involving progressively co 2 rich fluids and an intensive episode involving a mixture of these fluids with externally derived ca rich fluids

on the controls of oxygen fugacity in the generation and crystallization of peralkaline melts the formation of peralkaline melts is generally recognized to be related to enrichment of the mantle in sodium or potassium during a metasomatic event that predated magma generation the wide range in mineral assemblages mineral compositions and fluid compositions in peralkaline melts are to a large extent a function of the sodium potassium content of these mantle metasomatizing fluids which also governs redox conditions we propose that sodic fluids will reduce the mantle assemblage by depleting ferric iron from garnet to form the aegirine component in pyroxene in contrast potassic fluids would oxidize the mantle assemblage by extracting al2o3 from the garnet to make phlogopite we suggest that during differentiation of peralkaline melts once fe ti oxides have been depleted from the assemblage simple crystallization reactions of common solid phases such as aegirine or arfvedsonite control the oxygen fugacity by equilibria such as

zirconosilicate phase relations in the strange lake lac brisson pluton quebec labrador canada petrographic observations of subsolvus granites at strange lake indicate that the sodium zirconosilicate elpidite crystallized under magmatic conditions but that the calcium zirconosilicates armstrongite and gittinsite are secondary this interpretation is consistent with the extensive solid solution displayed by elpidite and the restricted compositions of armstrongite and gittinsite both calcium zirconosilicate minerals show textural evidence of having replaced elpidite and in the case of gittinsite with major volume loss in the near surface environment gittinsite plus quartz fill the volume formerly occupied by elpidite at greater depth gittinsite and armstrongite partially replaced elpidite but are not accompanied by quartz and abundant pore space is observed where gittinsite is the principal secondary phase below 70 m elpidite is generallyunaltered replacement of elpidite by armstrongite is interpreted to have been a result of the cation exchange reaction nazzrsi601s 3hzo ca2 cazrsi601s 3hzo 2na elpidite armstrongite

early jurassic south american pectinaceans and circum pacific palaeobiogeography abstract in the light of new data from south america high latitude southern bivalve faunas are now recognized for the early jurassic it is proposed that an austral realm was in continuous existence throughout jurassic times some bivalve genera palmoxytoma kolymonectes radulonectites agerchlamys n gen and groups of species of plicatula harpax show a bipolar distribution suggesting climatic control in the early jurassic a distinctive group of high latitude bivalves included monotidae kalenteridae oxytomidae and some pectinidae and plicatulidae based on the pectinacean s l bivalves the east west faunal differentiation was weaker than the latitudinal one in the early jurassic pacific the southern andes were situated in a transitional area between the tethyan and austral realms as shown by the mixed influence of the local bivalve faunas

a guide to phanerozoic cold polar climates from high latitude ice rafting in the cretaceous the high latitude extent of warm climate indicators at certain times in earth history has been considered as evidence that the globe was ice free for long intervals despite theoretical considerations and results from numerical modelling experiments1 2 indicating that this was unlikely one of the warmest periods the cretaceous displays faunal and floral evidence for cool temperate to sub tropical conditions very near to the poles however our studies of lower cretaceous mudstones of central australia that contain outsized exotic blocks have led to the conclusion that the blocks were emplaced by ice rafting implying that high latitude ice was present at sea level strata of a similar origin of mid jurassic to mid cretaceous age occur on other continents that were positioned between 65 and 78 palaeolatitude indeed there is a record of high latitude ice rafting throughout the phanerozoic suggesting that ice was present on earth for much of its history and that ice free conditions could have been at most only episodic over the past 600 myr

zr and ree mineralization in sodic lujavrite from the saima alkaline complex northeastern china a mineralogical study and comparison with potassic rocks abstract the triassic saima alkaline complex on the liaodong peninsula northeastern china consists mainly of potassic phonolite nepheline syenite and sodic lujavrite the lujavrite shows significant zr ree mineralization which is present in the form of early magmatic zr ree enriched clinopyroxene 30 40 titanite 5 and loparite ce and late magmatic to hydrothermal wadeite widespread eudialyte group minerals 5 10 and catapleiite ultimately the fractionation of the alkaline magma leads to the crystallization of mosandrite and hezuolinite textural relations and compositional variation among the characteristic zr ree bearing minerals record that both zr and rees were strongly incompatible in the sodic melt but that zr mineralization preceded ree mineralization the main zr ree mineralization in the saima lujavrite resulted from the high peralkalinity na k ratio and hfse content low oxygen fugacity and the intensive activity of water and volatiles of its evolving magma the discontinuous and abrupt changes in melt composition and mineral assemblage from the potassic nepheline syenite of the complex to the sodic lujavrite suggest that their magma was derived from different episodes of magmatic activity with different physico chemical characteristics rather than from the continuous evolution of a single magmatic event

mesozoic evolution of west antarctica and the weddell sea basin new paleomagnetic constraints paleomagnetic data from the antarctic peninsula and our recent results from the ellsworth whitmore mountains block suggest that since the middle jurassic these two west antarctic blocks have undergone little relative movement and together have rotated relative to the east antarctic craton new data from lower cretaceous rocks from the thurston island region of west antarctica suggest that on the basis of paleomagnetic constraints the antarctic peninsula ellsworth whitmore mountains and thurston island blocks define a single entity which we call weddellia some motion between these blocks is possible within the limits of the paleomagnetic data between the middle jurassic and early cretaceous weddellia remained attached to west gondwanaland while east antarctica moved southward dextrally relative to weddellia from the early cretaceous to mid cretaceous weddellia rotated clockwise 30 and moved sinistrally approximately 2500 km relative to east antarctica to its present day position we suggest the early to mid cretaceous to be the time of the main if not initial opening of the weddell sea

a revised identification of the oldest sea floor spreading anomalies between australia and antarctica we propose that magnetic anomalies south of australia and along the conjugate margin of antarctica that were originally identified as anomalies 19 to 22 may be anomalies 20 to 34 the original anomaly identification has two troublesome aspects 1 it does not account for an extra anomaly between anomalies 20 and 21 and 2 it provides no explanation for the rough topography comprising the diamantina zone with our revised identification there is no extra anomaly and the diamantina zone is attributed to a period of very slow spreading 4 5mm yr half rate between 90 and 43 m y the ages bounding the interval of slow spreading 90 and 43 m y correspond to times of global plate reorganizations our revised identification opens up the possibility that part of the magnetic quiet zone south of australia formed during the cretaceous long normal polarity interval breakup of australia and antarctica probably occurred sometime between 110 and 90 m y b p the breakup unconformity identified by falvey in the otway basin may correspond to a eustastic sea level change

agpaitic nepheline syenites a potential source of rare elements abstract the agpaitic nepheline syenites may with regard to their elevated contents of a number of rare elements be compared with the complex granite pegmatites both rock types form highly evolved magmas under closed system conditions which prevent volatiles from escaping agpaitic rocks are peralkaline nepheline syenites characterized by the presence of complex rare element minerals such as eudialyte and mosandrite instead of the simple minerals such as zircon and ilmenite uranium deposits have been found in agpaitic rocks in brazil pocos de caldas china saima and greenland ilimaussaq nb and apetite deposits in russia lovozero and khibina the type locality of agpaitic rocks the ilimaussaq complex in south greenland is characterized by elevated contents of elements such as zr ree y be li nb u th and f not only in pegmatites late veins and contact fenites but also in some of the rocks especially lujavrite and kakortokite the most important rare element containing minerals are eudialyte zr ree y nb steenstrupine u th ree rinkite nb ree y u pyrochlore and perovskite nb ta li mica li chkalovite be and villiaumite f occurrences of eudialyte rich kakortokite and lujavrite are presently being explored in the ilimaussaq complex as sources of zr ree y and nb

tectonic and palaeobiogeographic significance of the chatham islands south pacific late cretaceous fauna abstract the cretaceous fauna of the chatham islands south pacific is essentially a tectonically controlled facies fauna with origins relating to divergent plate motions and concomitant deposition of volcaniclastic transgressive sediments in half grabens in the chatham rise region during the late cretaceous at least 60 macroinvertebrate predominantly mollusca taxa and one vertebrate have been recorded from the kahuitara tuff campanian lower maastrichtian of pitt island the separation of the new zealand subcontinent including the chatham rise and tasman sea region from the marie byrd land sector of the gondwana margin along with changing oceanic circulation lowering sea surface temperatures and believed increasing temperature gradients enhanced the distinctiveness of the fauna as reflected in the strong species level endemicity of the fossil record shoaling from volcanic activity in the chatham islands region created substrates suitable for colonization of a characteristic hardground community dominated by epifaunal suspension feeders ca 41 followed by lower percentages of infaunal suspension feeders ca 30 epifaunal browsers ca 14 deposit feeders ca 8 and carnivores ca 5 the kahuitara tuff faunule is divided into four biogeographic groupings at genus and subgenus level indo pacific tethyan ca 37 cosmopolitan ca 34 palaeoaustral ca 28 5 and endemic ca 8 5 palaeoaustral taxa are inclusive of endemic groups in accordance with c a fleming s original ideas these percentages suggest an overall relatively warm water semi global biogeographic flavour at this taxonomic level some 43 of taxa from the kahuitara tuff are found in mainland new zealand coeval faunas and about 41 are endemic to the chatham islands differences being attributable largely to facies and to a much lesser degree to geographic isolation at species level endemic taxa of cosmopolitan or wide ranging indo pacific tethyan and palaeoaustral genera subgenera 83 dominate with negligible representation of widespread or cosmopolitan species and endemic species of endemic genera subgenera it is suggested that the kahuitara tuff faunule represents evolutionary divergence reflecting range retractions of a former cosmopolitan early to late mesozoic world nearly all kahuitara tuff taxa are endemic to either the chatham islands or mainland new zealand similarities of the fauna with other coeval faunas around the rim of the southern circum pacific are moderate to weak at genus and subgenus level indicating a degree of provincialism and isolation especially at species level the chatham islands fauna probably belonged to the short lived campanian to masstrichtian weddellian biotic province of w j zinsmeister the kahuitara tuff fauna evolved from a mixture of austral and boreal elements during the late cretaceous with evidence of approximately 40 taxa having ancestors in the chatham islands new zealand region of the gondwana supercontinent changes in composition across the k t boundary in the chatham islands were dramatic with very few genus and subgenus level taxa in the kahuitara tuff present in the upper palaeocene to lower eocene red bluff tuff

a warm equable cretaceous the nature of the problem abstract the nature of the problem of warm equable paleoclimates is defined by investigating the mid cretaceous period the problem consists of three components 1 defining precisely the climatic state during any specified interval of geologic time 2 specifying the external climatic forcing factors which may have been important and 3 understanding the climatic response to any specific modifying influence these components are characterized by limitations of critical importance in understanding paleoclimates the nature of the problem of a warm cretaceous is defined both qualitatively and quantitatively within these limits

enrichment of ion exchangeable rare earth elements by felsic volcanic rock weathering in south china genetic mechanism and formation preference abstract felsic volcanic rocks are an important source for generating ion adsorption type rare earth element ree resources to better understand the supergene enrichment of rees related to felsic volcanic rock weathering this study conducted an investigation of indosinian felsic volcanic rocks from guangxi southwest china which have been subjected to deep weathering the weathering has formed large areas of thick regolith with the potential to host ion adsorption type ree mineralization the felsic volcanic rocks belong to the dacite rhyolite series and are peraluminous high k calc alkaline and ree rich 325 376 ppm abundant ree bearing accessory minerals are present in the felsic volcanic rocks including titanite average ree 15 1 wt allanite average ree 14 9 wt and apatite average ree 1510 ppm and these three minerals contain an estimated 88 7 of the whole rock rees content significant ree enrichment is present in the felsic volcanic rock derived regolith a typical rhyolite derived regolith profile has ree contents that increase from 376 ppm in the rhyolite to 1737 ppm in the regolith representing an almost five fold enrichment due to weathering the rees in the regolith are present in an ion exchangeable form irees which accounts for 52 87 of the total rees present trees the occurrence of irees is closely linked to clay minerals showing an affinity in the order halloysite kaolinite illite continuous operations of rees by an eluviation illuviation process from the source minerals titanite allanite apatite to sink minerals kaolinite halloysite illite results in an iree enriched zone in the middle and lower parts of the rhyolitic regolith notably besides the studied indosinian felsic volcanic rocks there are multi epochs of such lithology outcropped in south china their related irees mineralizations however are preferentially developed in the weathered terrains of early yanshanian and indosinian felsic volcanic rocks and not in those of the yanshanian and late yanshanian felsic volcanic rocks a comparison of the mineralized and barren units indicates that the irees mineralization hosted in felsic volcanic rocks regolith is controlled by some key endogenic and exogenic ore forming factors high initial ree concentrations in the unaltered felsic volcanic rocks a suitable climate and a relatively quiescent tectonic setting are favorable for the formation and preservation of irees mineralization

finite volume two dimensional unsteady flow model for river basins the paper presents a two dimensional unsteady flow model rbfvm 2d based on the finite volume method with a combination of unstructured triangular and quadrilateral grids in a river basin system the attractive feature of this model is that it calculate of the mass and momentum flux across each side of elements as a riemann problem which is solved using the osher scheme this feature enables this model to deal with the wetting and drying processes for flood plain and wetland studies dam breaking phenomena involving discontinuous flows subcritical and supercritical flows and other cases the computations of tributary inflows and regulated flows through gates weirs and culverts or bridges are also included sample applications of this model to two dam break problems showed fairly satisfactory results also this model was applied to a portion of the kissimmee river basin in florida for flow simulations and the results agreed well with the field and laboratory data in a physical model study of this ri

evidence of displaced terranes from permian to jurassic faunas around the pacific margins for the permian to jurassic time interval tethyan marine invertebrate faunas which are generally accepted as having lived at low latitude can be distinguished from less diverse higher latitude faunas displacement of these low latitude faunas to positions of high latitude around the pacific margins therefore provides key evidence for the movement of so called suspect or displaced terranes the fullest story so far has been worked out for the western margin of n america as far north as southern alaska but there is also convincing evidence for the substantial northward movement of continental segments along the ne asian margin as regards the southern hemisphere the torlesse terrane of new zealand appears to have moved a considerable distance southwards but there is no fauna1 evidence of comparable far travelled suspect terranes along the andean margin of south america not only tethyan and boreal but e and w pacific elements are detectable in the faunas and the distribution of these argues for a panthalassia studded with islands of various sizes fringing the adjacent continents rather than for the disintegration of a single continent pacifica

the effect of fluorine on clinopyroxene melt trace element partitioning the impact of fluorine on phase relations and clinopyroxene melt element partitioning has been explored experimentally to better understand the effect of this halogen on the residual enrichment of the ree and hfse during crystallisation of alkaline and peralkaline magmas clinopyroxene was grown from three hbox h 2 hbox o saturated synthetic glasses of tephriphonolite to phonolite composition in a rapid quench internally heated pressure vessel at 650 800 circ c and 200 mpa with delta log f hbox o 2 fixed to ca fmq 1 the fluorine content in the charges was varied and produced quenched melts from fluorine free to 1 6 wt f the experiments yield an assemblage of melt fluid sodic clinopyroxene biotite magnetite k feldspar titanite fluorite and hiortdahlite a na ca ti f sorosilicate addition of fluorine markedly increases the mode of biotite without significantly affecting the mode of clinopyroxene relative to fluorine free compositions experiments with 1 6 wt fluorine in the melt show a strong decrease in clinopyroxene melt partition coefficients for the trivalent ree la dy and y with a lesser decrease for the d mathrm hree and d mathrm hfse 4 the diminished uptake of these metals by clinopyroxene may reflect changes to their speciation in the melt phase consistent with the formation of ree f complexes and with modifications to the medium range structural environment around hbox hfse 4 ions in the melt an increase in the fluorine content of the melt will thus make the ree and hbox hfse 4 progressively less compatible and therefore available for residual enrichment

prefolding and premegakinking magnetizations from the devonian comerong volcanics new south wales australia and their bearing on the gondwana pole path palaeomagnetic results from the late middle to early late devonian comerong volcanics in the budawang synclinorium lachlan fold belt lfb new south wales australia satisfy a fold test and support the hypothesis that foliated parts of the lfb have been folded by megakinks during the terminal mid carboniferous orogenic phase the preferred pole position is at 76 9 s 330 7 e a95 7 2 allowing calibration of the australian pole path at around 370 ma ago an alterative pole position at 71 3 s 283 1 e same a95 takes into account a possible rotation of the megakinked terrane by 15 clockwise with respect to the australian craton although there are still problems unravelling previously published results from silurian rocks in the lfb both because of unreliability and uncertainty as to where the lfb crustal units lay in relation to the australian craton there is no geological reason to suspect any large relative movement between the lfb and the craton since the middle devonian and thus the comerong volcanics pole position is representative of the late devonian for australia the new pole requires reassessment of many other poles that have previously been accepted as representing the siluro devonian for australia and gondwanaland we present reasons for believing that the magnetization or remagnetization of many rock units e g mereenie sandstone and mulga downs group australia and the gneigura supergroup africa was later than sedimentation probably during widespread early carboniferous deformation another rock unit msissi norite africa could be of early carboniferous rather than late devonian age

fluid rock interaction in autoliths of agpaitic nepheline syenites in the ilimaussaq intrusion south greenland abstract within the 1 16 ga old ilimaussaq intrusion up to 700 m large autoliths occur in one stratigraphic unit of the layered floor series of agpaitic nepheline syenites kakortokites these autoliths consist of two different rock types augite syenite and naujaite agpaitic nepheline syenite all three rock types show a number of alteration features related to the entrapment of the autoliths in the kakortokite magma caused by the interaction with a fluid phase in the kakortokites the oxidation of primary arfvedsonite to aegirine and fluorite is restricted to the close proximity to the autoliths close to the surrounding kakortokite the primary mafic phases of the augite syenites augite fayalite fe ti oxides are completely replaced by arfvedsonite aenigmatite biotite aegirine and fluorite the decomposition of primary hastingsite to spectacular aegirine augite nepheline aenigmatite symplectites can be observed up to several meters inside the autoliths additionally fluorite formed at grain boundaries of primary nepheline in the naujaite autoliths primary arfvedsonite is replaced by aegirine biotite intergrowths and abundant aenigmatite is occasionally replaced by ti rich aegirine and fe ti oxides the mineral reactions in the autoliths are used to decipher details of the late to post magmatic processes in a peralkaline syenitic intrusion mineral equilibria record an evolution governed by falling temperature 620 to ca 500 c and increasing relative oxygen fugacity from fmq 1 to above fmq 4 quantification of the observed mineral reactions reveals the infiltration of the autoliths with an oxidizing fluid phase rich in na and f and minor addition of k volatiles h and f and in some cases also fe ti and ca mg released from primary autolith phases were mainly just relocated within the autoliths

petrogenesis and mineralization of ree rich granites in qingxi and guanxi nanling region south china abstract mesozoic granites in the nanling region south china are important primary rocks for ion adsorption rare earth element ree deposits moreover metallic deposits of w sn nb and ta also develop in these granites most of which formed in the late jurassic the qingxi and guanxi granites in the nanling region contain abundant ree minerals and have zircon u pb ages of 223 0 0 7 ma and 198 8 1 4 ma respectively they are of metaluminous to slightly peraluminous in character having a high k calc alkaline composition and have high k2o na2o and feot mgo contents and a ga al ratio similar to a type granites these granites plot into the post collision field similar to the a2 type granites the qingxi and guanxi granites indicate a crust dominant origin by having high levels of rb and th relative to nb and ta normalized to ocean ridge granites they are characterized by lree enrichment and the majority of ree accumulating in the primary ree minerals include ree phosphates and fluorocarbonates the guanxi rocks have a stronger negative eu anomaly but lower ree composition than the qingxi granites implying that the basement may have played an important role in the ree mineralization rather than fractional crystallization this further implies that the basement in south china may have been subjected to different evolutionary geodynamics resulting in different multi metallic mineralization of w sn nb ta ree hosted by large scale mesozoic granites

ore forming potential of alkaline magmas abstract geochemical models of the genesis of the largest rare metal deposits connected with agpaitic nepheline syenites are discussed in this paper thermodynamic calculations demonstrate that high alkalinity prevents the separation of volatile components into the gas phase the rare earth deposits have been formed at the magmatic stage during the process of crystal differentiation jointly with convection in the magmatic system the saturation of alkaline magma in respect of ore minerals at early stages of crystallization is considered to be the necessary condition for the formation of cumulative magmatic deposits these considerations are proved by data on micro inclusions

apatite in igneous systems apatite is a minor but ubiquitous mineral in most igneous rocks although the modal proportion of apatite in common rocks is generally low it can reach high concentrations in enclaves cumulates and other rocks of low abundance i e rocks that constitute a small volume of the crust and mantle e g nelsonites the presence of apatite in most rocks is due not only to its low solubility in naturally occurring melts and aqueous solutions but also to the limited ability of common rock forming minerals to accept the amount of phosphorus that occurs in most rocks into their structure in this paper we will discuss some aspects of the occurrence texture composition physical chemistry and petrogenetic significance of apatite in felsic rocks i e andesite to rhyolite and their plutonic analogs in mafic i e basalts and related rocks and plutonic analogs and ultramafic rocks of the earth s crust and mantle fluorapatite is by far the most common member of apatite family found in igneous rocks however most natural fluorapatite contains some chlorine and hydroxyl as well and these constituents can attain high concentrations in some cases the other halogens bromine and iodine also occur in apatite but their concentrations are much lower than chlorine and fluorine many cations commonly substitute for calcium and phosphorus in apatite however they rarely reach concentrations that warrant the definition of a separate mineral species apatite can be described by the general formula a5 xo4 3z following sommerauer and katz lehnert 1985 the a site accommodates large cations e g ca2 sr2 pb2 ba2 mg2 mn2 fe2 ree3 eu2 cd2 na pan and fleet ch 2 in this volume and comprises two sites that exhibit vii fold

a review of mesozoic climates there is overwhelming evidence based on the distribution of distinctive sediments and fossils and oxygen isotope data that the climate of the mesozoic world was appreciably more equable than that of today with no polar ice caps but precise quantitative data are not available except for an episode of late cretaceous cooling there is no good documentation of any significant change in global temperature distributions through the era the distribution of coals and evaporites together with other criteria indicates a pattern of humid arid and zones appreciably different in important respects from that of today during the triassic and jurassic western pangaea in low to middle latitudes was largely arid but in the early cretaceous the lands on the margin of the newly opening central atlantic and western tethys experienced a humid climate by late cretaceous times arid zones had become very restricted in extent because of insufficient suitable data attempts at climatic modelling have had only modest success and only to a limited extent can the major long term changes in climate between the permian and the present be explained in terms of changing geography the most probable explanation of mesozoic equability is an increased atmospheric co 2 content a number of enigmas remain such as the existence of flourishing forests in polar palaeolatitudes whereas for the late cenozoic short term climatic changes can be related successfully to variations in the geometry and mechanics of the earth sun system there is a long way to go before comparable success can be claimed for the mesozoic

transient two dimensional simulation of real flood events in a mediterranean floodplain the application of a two dimensional 2d finite volume numerical model to real flood events in the ebro river is presented the hydraulic model used is based on the 2d transient shallow water equations on the irregular bed that are able to compute flow advance over a dry bed this study involves the reliable simulation of not only the flood wave advance but also the drying process in a series of events of different magnitude the importance of the correct characterization of the roughness coefficient and the topography is emphasized in the study the former is estimated from a previous classification of structurally homogeneous habitats and the latter is defined by merging the digital terrain model data with a hydraulic river bed elevation reconstruction algorithm the calibration of the full model resulting from the roughness bed river and flow simulation models is based on field measurements of the flooded area for two steady discharges the validation is performed by comparing the numerical results with the water levels measured during five flood events at certain times with the flooded area and time series of continuous point measurements of water depth during different situations throughout the year because the model provides correct predictions of the surface processes both for low and high flow discharges the simulation results are used to analyze the present floodplain hydrodynamics in the same way different topographic scenarios on the basis of changes in the hydraulic river floodplain connectivity are generated to analyze their potentially beneficial effect in the floodplain geomorphic dynamics doi 10 1061 asce hy 1943 7900 0000565 2012 american society of civil engineers ce database subject headings unsteady flow overland flow hydration dewatering flood plains shallow water mediterranean sea simulation author keywords unsteady surface flow wetting drying finite volume shallow water hydrodynamic floodplain hydraulic bed reconstruction

distinguishing magmatic and metamorphic processes in peralkaline rocks of the norra karr complex southern sweden using textural and compositional variations of clinopyroxene and eudialyte group minerals