sills associated with the bushveld complex south africa an estimate of the parental magma composition abstract four distinct ages of sills intrude the floor rocks under the bushveld complex the first is a metadolerite and pre dates the bushveld complex the middle two are generally related to the complex itself one has quench textured olivine and orthopyroxene crystals and chemically equates to the parental magma of the bushveld complex the second suite is a hypersthene microgabbro representative of the second major injection of magma into the complex the last is doleritic and does not obviously correlate with any portion of the layered sequence the sills genetically related to the complex display several features 1 lack of chilled margins coarse grain size ability to melt country rock xenoliths extreme heterogeneity 2 atypical of normal sills but explicable in their present context

from greenhouse to icehouse organic walled dinoflagellate cysts as paleoenvironmental indicators in the paleogene abstract dinoflagellates are an important component of the extant eukaryotic plankton their organic walled hypnozygotic cysts dinocysts provide a rich albeit incomplete history of the group in ancient sediments building on pioneering studies of the late 1970s and 1980s recent drilling in the southern ocean has provided a wealth of new dinocyst data spanning the entire paleogene such multidisciplinary studies have been instrumental in refining existing and furnishing new concepts of paleogene paleoenvironmental and paleoclimatic reconstructions by means of dinocysts because dinocysts notably exhibit high abundances in neritic settings dinocyst based environmental and paleoclimatic information is important and complementary to the data derived from typically more offshore groups as planktonic foraminifera coccolithophorids diatoms and radiolaria by presenting case studies from around the globe this contribution provides a concise review of our present understanding of the paleoenvironmental significance of dinocysts in the paleogene 65 25 ma representing earth s greenhouse icehouse transition this episode holds the key to the understanding of extreme transient climatic change we discuss the potential of dinocysts for the reconstruction of paleogene sea surface productivity temperature salinity stratification and paleo oxygenation along with their application in sequence stratigraphy oceanic circulation and general watermass reconstructions

spinels and mg ilmenites from the noril sk 1 and talnakh intrusions and other mafic rocks of the siberian flood basalt province spinels from the mineralized noril sk 1 and talnakh intrusions show a broad and distinctive compositional spectrum from normal chromite to ti enriched aluminous magnetite in the talnakh intrusion in particular the range of spinel compositions extends across a compositional space where spinels are rare in other layered intrusions spinel compositions vary widely on a scale of individual thin sections and are influenced by the nature of the enclosing silicate phase spinels enclosed in olivines are less ti enriched than those outside olivine grains compositional variance in the spinels is attributed to variable but generally advanced reaction between cumulus chromite grains and solidifying trapped intercumulus liquid the advanced nature of the process is attributed to the open nature of the intrusions continuous prolonged flow through of hot magma enabled cumulates within the intrusions to remain above their solidus temperature for longer than would be normal for sills of comparable thickness the barren chibacheka river intrusion shows some of the same features but differs from talnakh in that spinel olivine pairs record equilibration temperatures higher than those at talnakh temperatures recorded by spinel olivine pairs at talnakh are anomalously low for such a small intrusion again indicating prolonged slow cooling consistent with a flow through model for the sill spinel compositions support a hypothesized comagmatic relationship between the chibacheka river intrusion and the ti cr rich gudchichinsky picritic basalts spinels in the noril sk and talnakh intrusions imply a parent magma with a lower cr al ratio than the gudchichinsky picritic basalts spinels from the siberian intrusions show a similar range in compositions to the feeder intrusions of the karoo flood basalt province jinchuan spinels share the features of high ti contents and anomalously low equilibration temperatures with the noril sk talnakh spinels mg ilmenites are a feature of the siberian and jinchuan intrusions they are attributed to crystallization of ilmenite from evolved trapped intercumulus liquid buffered by surrounding mg rich cumulus phases their existence implies moderately but not unusually ti rich parent magmas consistent with compositions of the siberian traps lavas

atlantic paleogene biserial heterohelicid foraminifera and oxygen minima through most of the paleogene the planktonic foraminifera called biserial heterohelicids record the most depleted carbon isotope ratios among planktonic foraminiferal species they are interpreted to occupy an oxygen minimum habitat stronger interplanktonic carbon isotope contrasts and more enriched near surface carbon isotope values correspond to higher abundances of biserial heterohelicids this group appears to have preferred latitudes and times when the oxygen minimum was well developed biserial heterohelicid generic and specific diversity are directly related to the interplanktonic carbon isotope contrast minimal specific diversity characterizes the oligocene when interplanktonic and surface to bottom carbon isotope contrasts were consistently low diversity and abundance decreases were coeval with increased oceanic ventilation

late palaeocene early eocene dinoflagellate cysts from the turgay strait kazakhstan correlations across ancient seaways abstract the results of a quantitative palynological analysis emphasizing organic walled dinoflagellate cysts dinocysts of palaeocene eocene deposits exposed in the sokolovsky quarry turgay trough northern kazakhstan are presented here located in the ancient turgay strait a former seaway presumed to have connected the tethyan and boreal oceans and seas in the early palaeogene the sokolovsky quarry outcrop occupies a key position for the analysis of connections between these realms in general the dinocyst succession of sokolovsky closely resembles coeval arctic ocean north sea basin counterparts only in one interval endemic and or possibly tethyan species co occur the successive dinocyst assemblages allow recognition of the late palaeocene early eocene p5a p5b p6a p6b and e2 zones established in the north sea basin the succession is interpreted to represent parts of several third order sea level cycles correlative with those recognised in the north sea basin detailed comparison with similar studies from southeastern england allows the recognition of parts of third order cycles thanetian 1 tht 1 2 4 5 and ypresian ypr 3 in addition two important stratigraphic gaps within the palaeocene eocene succession are recognised possibly reflecting times of sea level lowering these gaps are inferred from 1 the absence of a complete p5b p6a transition 2 the absence of zone e1 and 3 bio sequence stratigraphy combined results indicate that the turgay strait flooded from the north between 57 8 and 57 1 ma cycles tht 1 and 2 in part with a minor missing section during the second phase of turgay flooding 56 4 55 3 ma evidence may be taken to indicate increased influence from the tethyan ocean and or warmer conditions deposits reflecting the late palaeocene thermal maximum associated with this interval are present at sokolovsky quarry this interval is marked by abundant apectodinium spp including a augustum and organic rich layers a third flooding is correlative to the london clay transgression from 54 5 ma from our study no decisive evidence has become available that confirms that a connection between the arctic and tethyan oceans via the turgay strait in the early palaeogene existed nevertheless during intervals of major sea level fall the turgay strait depression may be regarded to have been an important feature for migrating terrestrial biota four new wetzeliellioid taxa apectodinium sp a apectodinium sp b wilsonidium sp a and wilsonidium sp b are described from the palaeocene part of the section

global cooling accelerated by early late eocene impacts at ocean drilling program site 689 maud rise southern ocean 18o records of fine fraction bulk carbonate and benthic foraminifers indicate that accelerated climate cooling took place following at least two closely spaced early late eocene extraterrestrial impact events a simultaneous surface water productivity increase as interpreted from 13c data is explained by enhanced water column mixing due to increased latitudinal temperature gradients these isotope data appear to be in concert with organic walled dinoflagellate cyst records across the same microkrystite bearing impact ejecta layer in the mid latitude massignano section central italy in particular the strong abundance increase of thalassiphora pelagica is interpreted to indicate cooling or increased productivity at massignano because impact induced cooling processes are active on time scales of a few years at most the estimated 100 k y duration of the cooling event appears to be too long to be explained by impact scenarios alone this implies that a feedback mechanism such as a global albedo increase due to extended snow and ice cover may have sustained impact induced cooling for a longer time after the impacts

early oligocene dinoflagellate cysts from the upper rhine graben sw germany paleoenvironmental and paleoclimatic implications using principal component analysis and cyst diversity and equity trends we can recognize four distinct dinoflagellate cyst dinocyst assemblages from four rupelian early oligocene cores in the mainz embayment of the northern rhine graben sw germany these assemblages are the spiniferites ramosus pc1 thalassiphora pelagica pc2 homotryblium tenuispinosum pc3 and vozzhennikovia spinula pc4 assemblages the four cores provide an onshore offshore transect in the mainz embayment the h tenuispinosum assemblage shows high factor loadings in proximal to intermediate cores which is interpreted to reflect temporary high salinity conditions mean dinocyst diversity and equity increase with distance from the mid rupelian shoreline indicating increasingly stable paleoenvironmental conditions towards the center of the mainz embayment within individual cores changes in dinocyst assemblages through time are related to paleoenvironmental and paleoclimatological changes the three proximal to intermediate cores show dominance of the h tenuispinosum assemblage repeatedly alternating with high factor loadings of the t pelagica assemblage in both cases dinocyst diversity and equity tend to be reduced highest factor loadings of the s ramosus assemblage occur in intervals where neither of the above assemblages is dominant and tend to coincide with dinocyst diversity and equity maxima we interpret this distribution pattern to denote different paleoceanographic conditions reflecting drier and more humid phases in the early oligocene of central europe during relatively dry periods increased salinity conditions prevailed in proximal to intermediate settings of the mainz embayment as reflected by the dominance of the h tenuispinosum assemblage during more humid periods increased runoff led to higher nutrient availability and the formation of a pycnocline separating slightly less saline surface waters from higher saline deeper waters thus impeding vertical circulation these environmental conditions are documented in high loadings of the t pelagica assemblage which is indicative of increased eutrophication and or oxygen depleted bottom waters transitions between drier and more humid periods i e episodes of normal marine conditions are characterized by high loadings predominantly of the s ramosus assemblage as well as increased dinocyst diversity and equity values we propose that the alternations between drier and more humid phases may be related to variations in the ocean atmosphere moisture flux from the north atlantic into central europe bearing a high latitude climate signal 2002 elsevier science b v all rights reserved

late eocene to early oligocene dinoflagellate cysts from the priabonian type area northeast italy biostratigraphy and paleoenvironmental interpretation abstract marginal marine late eocene through early oligocene dinoflagellate cyst successions have been studied from the type area of the priabonian stage northeast italy the results allow the recognition of dinoflagellate zones previously defined in bio and magnetostratigraphically well calibrated pelagic sequences from central italy thus providing a first order correlation of the priabonian stage to the standard chronostratigraphic scale with unprecedented precision within this detailed biostratigraphic framework successive shifts in the composition of the dinoflagellate cyst assemblages are interpreted in terms of sea level and sea surface temperature sst fluctuations the evaluation of ecologically and sedimentary controlled changes in the composition of dinoflagellate cyst assemblages in combination with sequence stratigraphic analysis allows the reconstruction of third and fourth order sea level fluctuations the third order sea level fluctuations appear to correspond to exxon cycles ta4 1 4 5 the stratigraphically and palaeoenvironmentally important late eocene dinoflagellate cyst species glaphyrocysta priabonensis sp nov is formally described

late quaternary protoperidinium cysts as indicators of paleoproductivity in the northern arabian sea the reliability of organic walled cysts of the heterotrophic dinoflagellate protoperidinium as paleoproductivity indicators and the influence of bottom water oxygenation on cyst preservation is assessed by using arabian sea records of the past 125 kyr as a natural laboratory multidisciplinary geochemical micropaleontological and palynological datasets are integrated to analyze the relationship between protoperidinium cyst concentrations and other paleoproductivity proxies differential preservation potential is quantified in order to establish threshold oxidative degradation values for a possible application of quantitative protoperidinium cyst records in paleoenvironmental reconstructions results indicate that variations in protoperidinium cyst concentration closely correspond to other marine productivity and or upwelling proxies although oxygenation will lead to significant cyst degradation and thus decreased concentrations down core patterns in protoperidinium cyst concentration still primarily reflect changes in sea surface productivity in view of differential preservation among dinoflagellate cysts down core variations in relative abundance of protoperidinium should be treated with caution

morphological and abundance variations in homotryblium cyst assemblages related to depositional environments uppermost oligocene lower miocene jylland denmark abstract abundant occurrences of homotryblium dinoflagellate cysts have been interpreted as reflecting deposition in near shore marginal marine areas either in hypersaline or low salinity environments it has also been suggested that the process length of homotryblium cysts is related to proximity to the coast the present study provides new insights in the ecology of homotryblium and adds important information about the use of the morphological variations of homotryblium cysts for environmental reconstructions it presents an example where homotryblium cysts show high relative abundances in a low salinity partly restricted marine depositional environment four different species of homotryblium were recorded homotryblium additense is proposed as a new species the regional palaeogeographic distribution of the four species h additense homotryblium vallum homotryblium plectilum and homotryblium tenuispinosum shows a distinct depositional proximal distal distribution pattern h additense occurs only in a narrow stratigraphic interval in the most proximal part of the study area h vallum only occurs sporadically mainly in the proximal parts of the study area h plectilum dominates the proximal areas while h tenuispinosum dominates the more distal areas variations in abundance and cyst type also seem to respond to systems tracts sequence boundaries and flooding surfaces the observed distributional patterns of homotryblium species strongly indicate a response to the salinity of the depositional environment it is further suggested that at least some of the recorded species of homotryblium originated from the same motile dinoflagellate species producing cysts of different morphology in response to variations in salinity a phenomenon known from extant dinoflagellates

experimental data at 3 kbars pressure on parental magma to the bushveld complex experimental studies mainly under 3 kbars pressure have been undertaken on representative samples to determine if any of these compositions could be parental magma to the bushveld complex one such composition with 12 5 mgo mg mg fe of 0 72 and quartz normative crystallizes olivine fo88 as liquidus mineral at about 1 300 c followed at only slightly lower temperature by orthopyroxene at 3 kbars pressure there is a temperature drop of over 100 c before the appearance of plagioclase and finally clinopyroxene this crystallization sequence is in excellent agreement with the observed sequence in the lower part of the bushveld complex

similarities between planktonic and larger foraminiferal evolutionary trends through paleogene paleoceanographic changes abstract the paleogene evolutionary records of planktonic foraminifera and larger benthic foraminifera show parallel patterns in development that may in part reflect changes in nutrient flux to surface waters following the terminal cretaceous extinctions faunas were dominated by a few cosmopolitan opportunistic species more specialized k strategists in both groups diversified during the paleocene dominating into the early eocene consistent with he globally mild climatic regime and probable limited rates of nutrient flux to surface waters high latitude cooling intensified in the middle eocene promoting diversification of less specialized taxa characteristic of cooler and deeper waters higher latitudes meridional upwelling zones and boundary currents geographic ranges of warm water taxa diminished and fragmented yet many species survived thus global diversities during the middle eocene were the highest in the cenozoic as cooling and increased rates of nutrient flux further intensified in the late eocene extinction rates of warm water planktonic and larger benthic species exceeded origination rates of cooler water and less specialized forms so diversity dropped to intermediate levels where it remained through the late eocene and oligocene previous observations that planktonic foraminiferal faunas dominated by warm water taxa are often replaced by cool water faunas even though oxygen isotopes only recorded relatively minor cooling can be reconciled by the explanation that the biotic communities responded to changes in trophic resources and euphotic habitats that accompany the temperature reduction as well as to temperature change itself

geology of the cenozoic namakwa sands heavy mineral deposit west coast of south africa a world class resource of titanium and zircon exploration for heavy minerals along the coastal strip of southwest africa led to the discovery and subsequent delineation of the namakwa sands deposit near brand se baai in 1987 currently tronox limited controls the namakwa sands operation which has developed into a significant global producer of titanium slag pig iron ceramics quality zircon and rutile concentrates the namakwa sands deposit is classified as a megaresource with 1 17 billion tons bt of in situ ore containing an estimated 92 6 million metric tons mt of total heavy minerals and the equivalent of 23 9 mt tio2 units and 9 4 mt zircon the siliciclastic arenaceous deposit is divided into two adjacent orebodies referred to as graauwduinen west and graauwduinen east the graauwduinen west orebody consists of three strandline dune couplets set in a transitional shallow marine aeolian environment whereas the graauwduinen east orebody comprises a largely unrelated dune deposit superimposed onto the ore bearing sequence is a pseudostratigraphy of duricrust that effectively cemented the bulk of the mineralized sands to various degrees of hardness the two orebodies are profoundly different in many aspects spatially the planar mineralization bears northeasterly in the graauwduinen west orebody strikingly perpendicular to the southeasterly trend observed in the graauwduinen east orebody contrasts in their bulk chemistry and mineralogy are statistically significant the graauwduinen west orebody features noticeably better total heavy mineral grades accompanied by conspicuously high proportions of the gangue minerals garnet and pyroxene the valuable mineral fraction is predominated by ilmenite fetio3 followed in abundance by zircon zrsio4 leucoxene an alteration product of ilmenite and rutile tio2 their geochemistry mineralogy and petrography are extremely variable but the bulk of the current valuable mineral fraction is recoverable to premium grade products the proximal mesoproterozoic namaqualand metamorphic province is considered the main contributor to the current heavy mineral population the graauwduinen west orebody received source sediment via established fluvial marine courses whereas the source of the graauwduinen east orebody is considered to originate from a distinct fluvial aeolian corridor the genesis of the namakwa sands deposit is strongly entrenched in the geomorphic evolution of the west coast of southern africa since the cenozoic which was driven by regional tectonism fluctuating sea levels and alternating climatic patterns

towards quantitative environmental reconstructions from ancient non analogue microfossil assemblages ecological preferences of paleocene eocene dinoflagellates abstract we explore a novel approach towards quantification of paleo ecological signals from non analogue microfossil assemblages by quantifying relations between assemblages and high quality geochemical and sedimentological data from sedimentary archives we test this approach using one group of microfossils the organic cysts of dinoflagellates dinocysts which are widely used in shelf and open marine settings for biostratigraphy and reconstructions of past environments and environmental change similar to other microfossil groups dinocysts can be used to reconstruct environments with relatively high confidence for recent time periods as species affinities can be derived from observational and instrumental data in the absence of such data the ecology of extinct species is much less certain and as a result reconstructions in deep time are often limited to qualitative interpretations to explore if quantitative empirical relations between extinct dinocysts and high quality geochemical data can be established we study a major event of climate change the paleocene eocene thermal maximum petm 56 ma ago the petm is a particularly suitable period for this exercise as there is a multitude of large environmental perturbations associated with the transient global warming such as deoxygenation sea level rise and an accelerated hydrological cycle the synthesized published dataset exhibits better spatial and temporal coverage compared to any other period in deep time we extract empirical relations for the abundance of previously proposed paleoecological groups as a function of independent environmental proxies for example sea surface temperature and terrestrial organic matter input the results unequivocally illustrate that many dinocysts show relations to several of the reconstructed environmental variables notably we show that one genus apectodinium and an ecogroup epicystal goniodomidae required sea surface temperatures in excess of 20 c and 25 c respectively while one species florentinia reichartii was only abundant between 30 and 35 c other groups apparently favored either a limited spiniferites or high senegalinium terrestrial input to the study site relating to salinity nutrient levels or suspended sediment load i e murkiness crucially our work shows that the validation and quantification of ecological signals by independent environmental proxy data provides the opportunity to extract more quantitative information from a wide range of non analogue microfossil assemblages while this approach is not limited to any specific group of microfossils or macrofossils we stress that proper calibration datasets high quality sedimentological and geochemical proxy records are needed and should ideally have decent geographical coverage and include one or more environmental perturbations using this approach such empirical relations can be established for a wide range of microfossil groups that have highly complementary geological records which increases the value of existing data and ensures future application of microfossil based paleoecology

major calcareous nannofossil and foraminiferal events between the middle eocene and early miocene abstract the more significant biostratigraphic events during the time interval from beginning middle eocene to beginning miocene with special emphasis on the eocene oligocene boundary are discussed the microfossils considered are calcareous nannofossils planktic foraminifera and smaller and larger benthic foraminifera areas taken into account include particularly the caribbean trinidad barbados dsdp south atlantic sections cape basin site 360 walvis ridge sites 362a 363 angola basin site 364 the equatorial north atlantic dsdp site 354 and the southern alps possagno in the larger foraminifera the treatment is somewhat different with selected families and genera being considered for their distribution in the eastern and western hemisphere

biochronology and paleoclimatic implications of middle eocene to oligocene planktic foraminiferal faunas abstract planktic foraminiferal assemblages have been analyzed quantitatively in six dsdp sites in the atlantic site 363 pacific sites 292 77b 277 and indian ocean sites 219 253 in order to determine the nature of the faunal turnover during middle eocene to oligocene time biostratigraphic ranges of taxa and abundance distributions of dominant species are presented and illustrate striking similarities in faunal assemblages of low latitude regions in the atlantic pacific and indian oceans a high resolution biochronology based on dominant faunal characteristics and 55 datum events permits correlation between all three oceans with a high degree of precision population studies provide a view of the global impact of the paleoclimatic and paleoceanographic changes occurring during middle eocene to oligocene time planktic foraminiferal assemblage changes indicate a general cooling trend between middle eocene to oligocene time consistent with previously published oxygen isotope data major faunal changes indicating cooling episodes occur however at discrete intervals in the middle eocene 44 43 ma p13 the middle late eocene boundary 41 40 ma p14 p15 the late eocene 39 38 ma p15 p16 the eocene oligocene boundary 37 36 ma p18 and the late oligocene 31 29 ma p20 p21 with the exception of the e 0 boundary faunal changes occur abruptly during short stratigraphic intervals and are characterized by major species extinctions and first appearances the eocene oligocene boundary cooling is marked primarily by increasing abundances of cool water species this suggests that the e 0 boundary cooling which marks a major event in the oxygen isotope record affected planktic faunas less than during other cooling episodes planktic foraminiferal faunas indicate that the e 0 boundary event is part of a continued cooling trend which began during the middle eocene two hiatus intervals are recognized in low and high latitude sections at the middle late eocene boundary and in the late eocene p15 p16 these hiatuses suggest that vigorous bottom water circulation began developing in the middle eocene consistent with the onset of the faunal cooling trend and well before the development of the psychrosphere at the e 0 boundary

atlantic eocene planktonic foraminiferal historical biogeography and paleohydrographic indices abstract analysis of a quantitative and synoptic data base of eocene atlantic planktonic foraminifera has illuminated many facets of foraminiferal faunal structure and composition reflective of bioprovince and useful for empirical establishment of ecologic and paleohydrographic indices tropical indigenes such as the morozovellids turborotaliids subquadrate acarininids and some globigerinathekids dissolve most rapidly along with juveniles of most species tropical faunas are high in diversity and dominance include oxygen minimum indices such as the biserial heterohelicids only in high productivity times such as the middle eocene are dominated by genera with high numbers of species and species consistently typical of warm water regions until the late eocene when faunas include a higher number of middle than lower latitude types truly tropical genera are replaced by subtropical eutrophic indicators such as the globigerinathekids and contract to the florida current region prior to their extinctions at the end of the middle eocene atlantic late paleogene tropical forms first appear in the gulf of mexico at the end of the middle eocene middle latitude faunas include high numbers of chiloguembelinids pseudohastigerinids small and biconvex morozovellids round and globigerinid form acarininids low spired subbotinids in the late middle eocene high spired subbotinids large and typical globigerinids in the late eocene these forms have intermediate dissolution susceptibilities middle latitude faunas are often high in diversity in midddle latitude frontal regions dominance is low even in warm intervals when tropical indigenes increase in number in middle latitude faunas especially in boundary currents low latitude species penetrate temperate areas also during cool eutrophic periods of vigorous circulation such as the late middle eocene typical of temperate slope faunas are high abundances of high spired subbotinids and small sized catapsydracids high latitude faunas are usually low in diversity except in the middle to late eocene when frontal regions were located in the southern labrador sea and over rockall bank typical forms are the low spired subbotinids until the late middle eocene globorotaloids catapsydracids tenuitellids and in the late eocene the biserial heterohelicids indigenous species are the most solution resistant and many are mesopelagic during warmings rare low latitude indices penetrate high latitudes subpolar faunas have greatest affinities with middle latitude faunas at these times

eustatic variations during the paleocene eocene greenhouse world we reconstruct eustatic variations during the latest paleocene and earliest eocene 58 52 ma dinoflagellate cysts grain size fractions and organic biomarkers in marine sections at four sites from three continents indicate an increased distance to the coast during the paleocene eocene thermal maximum petm the same trend is recognized in published records from other sites around the world together the data indicate a eustatic rise during the petm beginning 20 to 200 ka before the globally recorded negative carbon isotope excursion cie at 55 5 ma although correlations are tentative we recognize other global transgressions during chrons c25n and c24n the latter may be associated with eocene thermal maximum 2 53 5 ma or the x event 52 ma these results suggest a link between global sea level and hyperthermal intervals potentially because of the melting of small alpine ice sheets on antarctica thermal expansion of seawater or both however the early onset of sea level rise relative to the cie of the petm suggests contributions from other mechanisms perhaps decreasing ocean basin volume on sea level rise copyright 2008 by the american geophysical union

the origin of high frequency platform carbonate cycles and third order sequences lower ordovician el paso gp west texas constraints from outcrop data and stratigraphic modeling abstract the passive margin succession of the diablo platform lower ordovician west texas is represented by the second order sauk c supersequence set consisting of a basal transgressive clastic unit the bliss sandstone above the breakup unconformity marking the second order basal lowstand transgressive phase overlain by 750 m of drift related shallow marine platform carbonates the el paso group recording the second order highstand due to late paleozoic structuring of the gondwanan passive margin present exposures in texas are in an updip shelf position and lack internal stratal geometries across depositional strike so sequences and systems tracts are identified solely by the vertical stacking patterns of depositional subfacies and higher frequency fifth order cycles accommodation plots fischer plots of high frequency cycles gauge systematic shifts in third order accommodation of two complete third order sequences each about 2 m y long and 60 140 m thick within the el paso group this is expressed in the vertical succession of cycle types systematic changes in cycle thickness and variations in subfacies as revealed by histograms of subfacies types tied to fischer plots a complete el paso shelf sequence contains a thin lowstand systems tract of quartz arenite a thick transgressive systems tract dominated by upward thickening thrombolitic subtidal cycles and a highstand systems tract marked by dolomitic thinning upward peritidal cycles containing quartz sand the el paso third order depositional sequences have been correlated by biostrat graphy and cycle stacking pattern from the franklin mountains southeast to the diablo arch northeast into the ardmore basin and thence to the appalachian basin hence the third order sequences appear to be eustatic based on biostratigraphic correlation of accommodation plots around the periphery of gondwana time series analyses suggest that a strict allocyclic milankovitch driven glacio eustatic mechanism alone is insufficient to account for the higher frequency fifth order and lower frequency third order accommodation cycles we used a two dimensional forward computer simulation to compare allocyclic and autocyclic models for high frequency cycles the allocyclic simulation superimposes a deterministic milankovitch glacio eustatic driver on a lower frequency third order accommodation cycle and generates a two dimensional synthetic cross section composed of high frequency peritidal and subtidal cycles stacked into third order sequences the autocyclic simulation is generated by a ginsburg autocyclic mechanism for high frequency cyclicity triggered by third order accommodation changes the autocyclic simulation quantitatively replicates an autocyclic mechanism for fifth order cycle development linked to onshore sediment transport and seaward progradation of tidal flats the two dimensional internal facies architecture of a third order sequence and the high frequency cycle stacking patterns are simulated in both scenarios important differences in patterns of cycles and subfacies stacking in the simulations shed light on the interpretation of the diablo platform cycles and sequences as an alternative or a supplement to autocyclicity or milankovitch forced glacio eustasy we have studied stochastic models for driving high frequency changes in relative sea level these intriguing results maintain essentially all the features observed in the rock record our smoothed sto hastic simulations suggest that the cycle problem is much more complex than presently realized

habitats of larger foraminifera on the upper reef slope of sesoko island okinawa japan larger foraminifera living in the upper 50 m in front of the fringing coral reef northwest off sesoko island japan show strong habitat differences this study closely examines the distributions of larger foraminifers and relates these to a number of key environmental factors using rigorous statistical methods since all larger foraminifera house symbiotic algae light attenuation by the water column is the most important limiting factor that must be dealt with wall structures water energy is also countered by test structure the local topography is responsible for different intensities of hydrodynamic forces which are expressed in various substrates mostly coral rubble and coarse grained sand the genus peneroplis very common on the reef flat clearly prefers hardgrounds of the shallowest slope parts down to 30 m while dendritina is restricted to sandy bottoms and avoids the uppermost meters of the slope it can be found down to 50 m at least alveolinella shows a similar depth distribution to dendritina but is common on hard bottom the distribution of parasorites which is restricted to sandy substrates starts at 20 m and extends to 80 m sorites on the other hand was found only on firm substrates between the reef edge and 50 m the same depth distribution was recorded for amphisorus but this genus is not correlated with specific substrates most of the amphistegina species prefer hardgrounds while amphistegina radiata is also common on sand the calcarinids capable of withstanding high water energy are abundant on firm substrates close to the reef edge only baculogypsinoides inhabits deeper parts of the slope on sandy bottom and avoids the shallowest parts sections with hard substrates are settled by heterostegina even down to 80 m although this genus was occasionally found on sandy bottoms nummulites in contrast is restricted to sands between 20 and 70 m operculina starting at 20 m also prefers sandy substrates but rare individuals were detected on coral rubble and macroids

paleoceanography of the cretaceous tertiary boundary event inferences from stable isotopic and other data we report the results of new stable oxygen and carbon isotope analyses on carbonate fine fraction whole rock and benthic foraminifers caco3 and coarse fraction percentage determinations and trace element sr analyses on carbonate constituents across the cretaceous tertiary k t boundary in deep sea drilling project dsdp sites 47 2 356 384 and 577 and compare them with published results from k t boundary sections in other dsdp sites we used the trace element data and scanning electron microscope examination to evaluate possible diagenetic alteration and relative preservation of the samples analyzed in this study the 18o data when interpreted as isotopic paleotemperatures indicate relative stable surface water and deepwater temperatures in the late maestrichtian followed by somewhat fluctuating temperatures in the early paleocene however there is no indication of either a significant warming or cooling at or following the k t boundary several sites do exhibit somewhat heavier 18o values by about 0 5 across the boundary which might suggest a 2 3 c cooling at most however we interpret these somewhat heavier 18o values as reflecting slightly better preservation of 18o of carbonate constitutents in relatively clay rich intervals e g lower diagentic potential characteristic of the k t boundary the 13c values of carbonate fine fraction and planktonic foraminifers indicate a major negative excursion in surface water total dissolved carbon across the boundary the surface water and deepwater 13c values from benthic foraminifers combined with calculated decreases in carbonate accumulation rates at all sites in the earliest paleocene are consistent with a major decrease in productivity across the k t boundary the decrease in caco3 accumulation rates is due not to increased rates of dissolution but to decreased production in surface waters the low productivity episode lasted at least 1 m y beyond the k t boundary crisis suggesting that hypothesized catastrophic events alone such as impact of an apollo object are not the only explanation for the observed long term decrease in productivity there is also an indication in the 13c curves from several sites that the surface water 13c decrease began in the latest maestrichtian suggesting that the decrease in productivity may have been independent of a hypothesized impact event

the eocene oligocene boundary event in the deep sea analysis of middle eocene to early oligocene calcareous and siliceous microfossils shows gradual biotic changes with no massive extinction event across the eocene oligocene boundary biotic changes in the late paleogene appear to reflect changing paleoclimatic and paleoceanographic conditions and do not support suggestions of a catastrophic biotic event caused by a bolide impact at the eocenel oligocene boundary

platforms of the nicaraguan rise examples of the sensitivity of carbonate sedimentation to excess trophic resources the nicaraguan rise is an active tectonic structure in the western caribbean carbonate accumulation on its platforms has not kept pace with relative holocene sea level rise despite a tropical location remote from terrigenous sedimentation trophic resources apparently exceed levels favoring coral reef development because sponge algal communities dominate the drowning western platforms in contrast to mixed coral algal benthos on pedro bank and well developed coral reefs along the north coast of jamaica concentrations of biotic pigments in sea surface waters show a corresponding west east gradient oceanic waters flowing over the western banks carry nearly twice as much biotic pigment as oceanic waters north of jamaica sources enriching the western caribbean are terrestrial runoff upwelling off northern south america and topographic upwelling over the nicaraguan rise that relatively modest levels of trophic resources can suppress coral reef development holds important implications for understanding carbonate platform drownings in the geologic record

pigment distribution in the caribbean sea observations from space abstract the caribbean is a semi enclosed tropical sea which is generally considered oligotrophic but that is influenced by nearly 20 of the annual discharge of the world s rivers amazon and orinoco rivers and by seasonal upwelling along the southern margin to investigate the role of these nutrient sources on the productivity of the region we mapped the distribution of pigments in the eastern caribbean east of 80 w using a series of coastal zone color scanner czcs images collected between november 1978 and december 1982 five additional images were examined for the period 1983 1986 the images revealed a seasonal cycle in the spatial structure of near surface pigment during january may there were high pigment concentrations 0 5 mg m 3 along the continental margin south of 14 n where upwelling occurred very little pigment 3 105 km2 this plume reached puerto rico around september october and drifted westward slowly losing its color signature we estimate that the discharge of the orinoco contributes 2 12 of the daily nitrogen requirements of the phytoplankton growing in the river plume and leads to the fixation of 7 29 105 tons of carbon per year the rest of the nitrogen demand appears to be met by nitrogen cycling the large scale 100 km pigment distribution patterns in the caribbean sea seem to be controlled by wind stress flux of water through the basin and river discharge westward advection of atlantic water probably dominates the flow during the first half of the year restricting the dispersal of blooms to the southern half of the caribbean while flushing the central and northern portions as the influx of atlantic water decreases in the second half of the year local ekman transport driven by the trade winds becomes dominant and surface waters drift northwestward throughout the basin the seasonal sequence of changes in pigment distribution patterns was consistent from year to year except in 1980 and 1984 when wind conditions in the caribbean were anomalous close scrutiny of the 4 years of czcs images did not reveal any evidence of large scale 300 km eastward flowing currents in the central caribbean this supports the view that previous observations of countercurrents were based on partial sampling of eddies of 100 250 km diameter

experimental study on the effects of h 2 o upon crystallization in the lower and critical zones of the bushveld complex with an emphasis on chromitite formation mafic ultramafic layered rocks of the lower and critical zones of the bushveld complex are believed to have formed from a parental magma usually labelled b1 with sio2 content at 55 wt mgo at about 12 wt and cr2o3 concentration at 0 15 wt previous experimental study at 300 mpa and nominally dry conditions showed that this composition had orthopyroxene on liquidus between 1250 and 1300 c and the mineral was joined by plagioclase and clinopyroxene at and below 1166 c the objective of this study was to investigate the effects of variable additions of h2o 2 4 and 6 wt in starting compositions on liquidus and sub liquidus phase equilibria main attention was given to the solubility of cr spinel and cr distribution between melt and crystalline phases six experiments were carried out in the internally heated pressure vessel ihpv at 300 mpa and in the temperature interval 1100 1300 c redox conditions were not controlled and thermal dissociation of the h2o component followed by hydrogen diffusion through container walls resulted in a noticeable oxidation of run products the effective values of fo2 in experiments were calculated using spinmelt 2 0 software bases on the regression of experimental data on the spinel melt equilibrium according to the calculations h2o additions in isothermal series of experiments increased fo2 by 0 8 1 6 log units from the level in a nominally dry run overall the experiments showed that h2o additions suppressed crystallization of silicates shifted olivine orthopyroxene peritectic equilibrium towards higher olivine stability olivine first appears in h2o bearing compositions at 1175 c and increased the proportion of magnetite component in spinel solid solution the addition of 4 wt h2o to the starting composition at 1200 c resulted in complete melting of orthopyroxene which left cr spinel as the only liquidus phase equal amount of h2o at 1125 c leads to complete melting of plagioclase orthopyroxene and clinopyroxene which leaves only olivine and spinel stable and increases the liquid mass fraction from 0 62 in the nominally dry compositions to 0 9 the results of this study appear to support the idea that chromitite layers in the critical zone of the bushveld complex were formed by episodes of hydration melting of silicate cumulates

fluctuations in the trophic resource continuum a factor in global diversity cycles the trophic resource continuum trc in euphotic zones of the world s oceans is the spectrum of conditions from the richest runoff and upwelling areas to the most nutrient deficient subtropical seas that spectral range has likely varied through geologic history as more efficient phytoplankton taxa evolved as oceanic circulation rates changed and in response to oceanic mixing events reduced rates of oceanic turnover should produce regionally intensified eutrophy and oligotrophy that is trc expansion because oceanic waters as a whole are relatively nutrient rich increased rates of oceanic turnover should prevent extremely eutrophic and extremely oligotrophic conditions from developing causing trc contraction global biotic diversities in the oceans are strongly influenced by communities in oligotrophic environments nutrient deficient waters are more stable and more transparent than richer waters permitting higher degrees of specialization sparse nutrient supplies necessitate smaller phytoplankton and longer more complex food chains preservation potential of oligotrophic biotas is also greater because calcareous taxa are more prevalent and because calcium carbonate is less apt to be bioeroded or dissolved fluctuations in the trc should profoundly affect diversity of habitats within the euphotic zone of the oceans the evolutionary response to a trc expansion diversification would occur in a geologic time frame of millions of years while evolutionary responses to a trc contraction including extinction could occur in a biological time frame of generations a simple model indicates that a reduction in the trophic resource continuum from expansion during a major marine transgression down to modern levels could result in loss of 40 of the euphotic habitats how fluctuations in the trc control diversity of euphotic habitats in the oceans provides an hypothesis by which to interpret global taxonomic diversity cycles as well as taxonomically selective extinctions changes in species dominance and some morphologic trends

paleo oxygenation in tertiary epeiric seas evidence from dinoflagellate cysts the dinoflagellate cyst record from an epeiric setting in the oligocene of southwest germany exhibits major changes associated with variations in paleo oxygenation inferred from benthic foraminifera dinoflagellate cyst diversity and equitability strongly decline in the case of extreme oxygen depletion the relative abundance of the dinoflagellate cyst thalassiphora pelagica inversely correlates with the availability of benthic oxygen the t pelagica spectrum consists of different morphotypes which are considered to represent different stages within the cystal part of the t pelagica life cycle following the concept of benedek and gocht the distribution of these morphotypes is also linked to oxygen availability horizons with highest t pelagica abundances are characterized by the occurrence of t pelagica specimens representing an early stage in cyst formation a model is proposed that uses t pelagica as a proxy to assess oxygenation both at the sediment surface and in the water column the occurrence of t pelagica specimens representing an early stage in cyst formation is interpreted to reflect the extension of oxygen depletion upwards into the water column because t pelagica is an easily recognized globally distributed element of paleogene and early neogene dinoflagellate cyst assemblages the application of this model may be of importance in the reconstruction of paleo oxygenation in epeiric settings from these times its sensitivity to changes in benthic oxygenation can be as high as if not higher than that of the approach based on foraminifera moreover it is applicable to decalcified sediments

the distribution of platinum group elements in the insizwa lobe mount ayliff complex south africa implications for ni cu pge sulfide exploration in the karoo igneous province the mount ayliff complex of the eastern cape province of south africa is a layered intrusion of some 800 km2 surface area and up to 1 200 m thickness on the basis of compositional similarities and spatial association it is generally interpreted to form part of the karoo igneous province similarities between the mount ayliff complex and the staging chambers and feeder conduits to flood basalts that host magmatic sulfide ores elsewhere in the world suggest that the mount ayliff complex may have an enhanced potential for noril sk talnakh type massive ni cu sulfide ores an idea that is supported by the well known sulfide occurrence at waterfall gorge here we present major trace and noble element data for 30 samples of cumulate rocks from a continuous 1 200 m drill core through the insizwa lobe of the complex as well as six samples of a footwall sill the taylor s koppie dike that was considered a possible feeder zone to the lobe and through a massive sulfide lens in the footwall of the lobe at ndzongiseni we show that most of the insizwa cumulate rocks contain small amounts of cumulus sulfides the sulfides including those at waterfall gorge can be explained by a model in which the sulfides were segregated from magma having chilled margin composition on the basis of the composition of the chilled margins the insizwa magma contained no entrained sulfides and was depleted in platinum group elements pge although not in cu and ni before emplacement these compositional characteristics are also observed in lavas of the central karoo igneous province and suggest only limited sulfide segregation from these magmas at depth our findings thus indicate relatively little potential for economic magmatic ni cu pge sulfide deposits in the insizwa lobe

hardened subtidal stromatolites bahamas hardened high relief stromatolites have been discovered along the margins of some bahamian platforms they occur in high energy tidal oolitic sand environments in waters ranging in depth from about 1 to 5 meters physical stress produced by actively migrating bed forms of oolitic sand appears to exclude grazing gastropods and subsequent community successions permitting stromatolite growth

ilmenite composition in the tellnes fe ti deposit sw norway fractional crystallization postcumulus evolution and ilmenite zircon relation major and trace element xrf and in situ la icp ms analyses of ilmenite in the tellnes ilmenite deposit rogaland anorthosite province sw norway constrains a two stage fractional crystallization model of a ferrodioritic fe ti p rich melt stage 1 is characterized by ilmenite plagioclase cumulates partly stored in the lower part of the ore body lower central zone lcz and stage 2 by ilmenite plagioclase orthopyroxene olivine cumulates upper central zone ucz the concentration of v and cr in ilmenite corrected for the trapped liquid effect 1 defines the cotectic proportion of ilmenite to be 17 5 wt during stage 1 and 2 implies an increase of dvilm during stage 2 most likely related to a shift in fo2 the proportion of 17 5 wt is lower than the modal proportion of ilmenite ca 50 wt in the ore body implying accumulation of ilmenite and flotation of plagioclase the fraction of residual liquid left after crystallization of tellnes cumulates is estimated at 0 6 and the flotation of plagioclase at 26 wt of the initial melt mass the increasing content of intercumulus magnetite with stratigraphic height from 0 to ca 3 wt results from differentiation of the trapped liquid towards magnetite saturation the mgo content of ilmenite 1 4 4 4 wt is much lower than the expected cumulus composition it shows extensive postcumulus re equilibration with trapped liquid and ferromagnesian silicates correlated with distance to the host anorthosite the zr content of ilmenite provided by in situ analyses is low 114 ppm and uncorrelated with stratigraphy or cr content the data demonstrate that zircon coronas observed around ilmenite formed by subsolidus exsolution of zro2 from ilmenite the u pb zircon age of 920 3 ma probably records this exsolution process

blackriveran carbonates from the subsurface of the lake simcoe area southern ontario stratigraphy and sedimentology of a low energy carbonate ramp the lowest upper ordovician blackriveran strata in the lake simcoe area represent the base of a major transgressive sequence of peritidal carbonates and siliciclastics from detailed petrographic

the apectodinium acme and terrestrial discharge during the paleocene eocene thermal maximum new palynological geochemical and calcareous nannoplankton observations at tawanui new zealand manifestations of profound perturbations in biogeochemical systems during the paleocene eocene thermal maximum petm include a prominent global negative 13c and a pronounced increase in the relative abundance of dinoflagellate cysts dinocysts assigned to the genus apectodinium while motile representatives of apectodinium were most likely thermophilic and heterotrophic the underlying causes of this dinoflagellate response are not well understood here we provide new insight by examining the palynology chemistry and calcareous nannoplankton across the petm in a continental slope section at tawanui new zealand across the petm marked changes in the relative abundance of apectodinium vary antithetically with significant changes in the 13c of carbonate and organic matter in general the high relative abundance of apectodinium relates to enhanced concentrations of dinocysts signifying a bloom of apectodinium in surface waters during the petm changes in apectodinium and 13c records correspond to variations in many other parameters including a smaller negative shift in bulk carbonate 13c than expected increased terrestrial palynomorphs elevated toc and c n ratios lower carbonate contents higher sio2 and al2o3 contents and lower si al ratios all of these variations can be explained by an increase in delivery of terrigenous material to the continental margin a peak in the relative abundance of glaphyrocysta dinocysts at the onset of the petm may indicate greater down slope transport of neritic material changes in calcareous nannoplankton abundances suggest increased nutrient availability in surface waters during the petm the combined results show that apectodinium dominated assemblages global perturbations in carbon isotopes and enhanced terrigenous delivery closely correspond in time at tawanui a sudden and massive carbon injection to the ocean atmosphere system may have enhanced weathering and increased terrigenous inputs to continental margins during the petm we further suggest that these inputs caused the apectodinium acme by elevating primary productivity in marginal seas

integrated paleoenvironmental analysis of the niobrara formation cretaceous western interior seaway northern colorado abstract this study presents a regional chronostratigraphic framework and paleoenvironmental reconstruction of the niobrara formation in northern colorado based upon multidisciplinary biostratigraphic and lithostratigraphic data a local biostratigraphic zonation is described for the coniacian to earliest campanian of this region of the western interior seaway based primarily upon the distribution of calcareous nannofossils three key paleoenvironmental packages are also identified and linked to the evolution of regional sedimentary facies during the early to late coniacian tethyan water masses interacted with boreal surface currents to produce regional upwelling along tectonically controlled bathymetric highs a well mixed relatively well oxygenated water column with warm surface water temperatures and high fertility sustained a rich microflora fauna and promoted higher carbonate production enhanced fluvial input and a weakening of tethyan influence during the early santonian mark the onset of a regional environmental shift this period of transition extends through the middle santonian and is characterized by pulses of transported material and relatively frequent turnover of faunal associations increased terrigenous runoff likely produced eutrophic surface waters and intensified water column stratification leading to a general deterioration of the bottom water environment in a progressively dysoxic setting continued strengthening of fluvial input during the late santonian to early campanian resulted in surface water freshening and sustained primary productivity this surface water environment in conjunction with stifled vertical mixing promoted the development of a stagnant and intensely stratified water column the basin was therefore severely dysoxic possibly anoxic and corrosive with chemically reducing bottom waters and an expanded oxygen minimum zone thereby limiting biotic development and causing the deposition of finely laminated mud rich carbonate poor seciments

flat pebble conglomerate its multiple origins and relationship to metre scale depositional cycles carbonate flat pebble conglomerate is an important component of precambrian to lower palaeozoic strata but its origins remain enigmatic the upper cambrian to lower ordovician strata of the snowy range formation in northern wyoming and southern montana contain abundant flat pebble conglomerate beds in shallow water cyclic and non cyclic strata several origins of flat pebble conglomerate are inferred for these strata in one case all stages of development of flat pebble conglomerate are captured within stormdominated shoreface deposits of hummocky cross stratified hcs fine carbonate grainstone a variety of synsedimentary deformation structures records the transition from mildly deformed in situ stratification to buckled beds of partially disarticulated bedding to fully developed flat pebble conglomerate these features resulted from failure of a shoreface and subsequent brittle and ductile deformation of compacted to early cemented deposits failure was induced by either storm or seismic waves and many beds failed along discrete slide scar surfaces centimetre scale laminae within thick amalgamated hcs beds were planes of weakness that led to the development of platy clasts within partly disarticulated and rotated bedding of the buckled beds in some cases buckled masses accelerated downslope until they exceeded their internal friction completely disarticulated into clasts and transformed into a mass flow of individual cm to dm scale clasts this transition was accompanied by the addition of sand sized echinoderm rich debris from local sources which slightly lowered friction by reducing clast clast interactions the resulting dominantly horizontal clast orientations suggest transport by dense viscous flow dominated by laminar shear these flows generally came to rest on the lower shoreface although in some cases they continued a limited distance beyond fairweather wave base and were interbedded with shale and grainstone beds the clasts in these beds show no evidence of extensive reworking i e not well rounded or condensation i e no rinds or coatings a second type of flat pebble conglomerate bed occurs at the top of upward coarsening metre scale cycles the flat pebble conglomerate beds cap these shoaling cycles and represent either lowstand deposits or in some cases may represent transgressive lags the clasts are well rounded display borings and have iron rich coatings the matrix to these beds locally includes glauconite these beds were considerably reworked and represent condensed deposits thrombolites occur above the flat pebble beds and record microbial growth before initial transgression at the cycle boundaries a third

the eocene oligocene boundary and the psychrospheric event in the tethys as recorded by deep sea ostracods from the massignano global boundary stratotype section and point central italy abstract latest eocene earliest oligocene deep water ostracods from the massignano global boundary stratotype section and point gssp central italy were studied from a palaeoecological perspective to investigate the psychrospheric event in the tethys although quantitative analyses were hampered by the low incidence of fauna the high resolution sampling used in this study 148 samples distributed over a 23 m thick succession spanning 3 m y allowed the following inferences 1 overall features e g abundance diversity composition of the assemblages suggest a middle lower bathyal environment with no significant palaeobathymetrical changes 2 today a similar fauna notably characterised by the common occurrence of the genus agrenocythere would likely be encountered in upper psychrospheric conditions water masses beneath the permanent thermocline with a temperature range of 4 10 c 3 although no noticeable faunal turnover has been recognised throughout the succession minor faunal changes seem to occur in the first part of the section probable appearance of legitimocythere presequenta and to a lesser extent also across the eocene oligocene boundary the presumed appearance of l presequenta latest eocene correlates quite well in timing and possible significance with the faunal changes observed in other microfossil groups foraminifers and dinocysts this event is possibly linked to a cooling pulse which might have been caused by the arrival or increasing advection of cold bottom waters in the study area faunal evolution across the eocene oligocene boundary is thought to be consistent with an intensification of the cooling trend and an increase of primary productivity which fits fairly well with the 13c record relationships between the subtle ostracod faunal changes observed in the massignano gssp and the main late eocene early oligocene psychrospheric event can be only speculative nevertheless we found no evidence that precludes the possibility of interpreting the massignano ostracod pattern as a subdued local expression of this major event although speculative this is a reasonable hypothesis because the investigated area is situated in western tethys far from the main circulation of deep ocean waters

direct response of small non glaciated headwater catchments to late quaternary climate change the valle de la fueva southern pyrenees abstract topographic depressions in mountain regions function as sediment traps and their morpho sedimentary archives provide important insight into erosion and sediment dynamics in mountain ranges in order to establish the direct drivers and timing of erosion phases in the southern central pyrenees small non glaciated headwater catchments in the highly erodible valle de la fueva drainage basin were investigated as to their morphogenetic development geomorphic mapping revealed three morphogenetic complexes associated with the valle de la fueva drainage basin development i high lying talus plateaus and lateral slopes ii extensive glacis and pedimentation surfaces and iii deeply incised ravines with late stage fluvial cut terraces the talus slopes are the oldest preserved geomorphic units of the valle de la fueva and potentially denote the initial drainage basin topography talus bedrock and boulder exposure ages cluster yet between 21 and 40 10be ka indicating that the carbonate dominated talus surfaces were rejuvenated during the last glacial cycle mis 4 mis 2 the younger morphogenetic complexes ii iii point to successive basin erosion stages from diffusive surface pedimentation under cold climate conditions ii to rapid linear fluvial dissection and late stage terrace formation iii denoting the abandonment of pediments as actively eroding surfaces 10be depth profiles of glacis cover sediments yielded consistent late mis 2 exposure ages the abandoning of pediments marks the onset of rapid fluvial downcutting of deep ravines iii around the holocene climate transition which involved substantial sediment routing and basin scale erosion lower fluvial cut terraces denote the termination of intense catchment erosion at around 14 8 10be ka and minor fluvial incision during middle late holocene this research shows that small non glaciated mountain catchments feature valuable high resolution morpho sedimentary archives that are useful for assessing the direct impact of major climate transitions on surface processes and landscape transformation in mountain regions improvements in quantifying the timing and rates of paleo surface processes are vital for enhancing regional glaciofluvial chronologies and large scale basin erosion models that are possibly afflicted with time averaging biases

relation of eustasy to stacking patterns of meter scale carbonate cycles late cambrian u s a abstract an interbasinal study of late cambrian cyclic carbonate successions in the appalachian and cordilleran passive margins suggests that superimposed orders of eustasy controlled the development of large scale depositional sequences and the component peritidal to subtidal meter scale cycles that comprise them the focus of this paper is on the small scale cyclicity its probable control by milankovitch forced sea level oscillations and how stacking patterns of meter scale cycles can be used to define internal components of larger scale sequences and estimate variations in relative sea level fining upward peritidal cycles showing evidence of episodic emergence grade seaward into coarsening upward subtidal cycles which lack evidence of emergence and form a continuum across the cambrian carbonate platforms eustasy appears to exert the dominant control on the simultaneous development of peritidal and subtidal cycles on late cambrian carbonate platforms evidence for milankovitch forcing of glacio eustatic sea level oscillations is provided by a 4 1 bundling of fifth order meter scale cycles 96 ky within fourth order cycles spanning tens of meters 440 ky within the big horse member of the orr formation in the house range of utah the 4 1 bundling may manifest the short e centricity to long eccentricity ratio of the milankovitch astronomical rhythms systematic changes in the stacking patterns of meter scale cycles can be used in conjunction with fischer plots to define long term sea level cycles on fischer plots of peritidal cyclic successions long term relative sea level rises are characterized by thick subtidal dominated cycles with thin laminite caps long term relative sea level falls are defined by stacks of thin laminite dominated cycles that show brecciated cycle caps and quartz sands toward the relative sea level lowstand on fischer plots of dominantly subtidal cyclic successions long term sea level rise is characterized by storm dominated open marine carbonate cycles or thick deep ramp shale based cycles falling segments of the fischer plot are characterized by thin shallow subtidal cycles compos d of restricted lithofacies cycle stacking patterns parasequence sets provide the crucial link between the meter scale cycles parasequences and the larger scale sequences and their component systems tracts one and two dimensional models of peritidal and subtidal cycle development indicate that whereas peritidal cycle thickness is primarily controlled by accommodation space deeper subtidal cycle thickness is primarily controlled by sedimentation rate lithofacies within peritidal cycles reflect the sedimentologic response to fluctuations in sea level lithofacies within subtidal cycles may be related to fluctuations in the zones of fairweather and storm wave reworking that oscillated in harmony with sea level fluctuations and may have acted as a subtidal limit to upward aggradation the 2 d modelling illustrates how stacked peritidal to deep subtidal carbonate cycles with thicknesses compositions and stacking patterns similar to the late cambrian of north america can be generated by ilankovitch driven composite eustasy

hyperstratification following glacial overturning events in the northern arabian sea 1 correlations between arabian sea organic carbon and gisp2 18o records indicate a pronounced oxygen minimum zone omz during interstadials whereas well oxygenated conditions prevailed during stadials local deep winter mixing ventilated intermediate water during the coldest stadials corresponding to north atlantic heinrich events here we show that in the arabian sea periods of climatic warming following heinrich events h6 h4 and the younger dryas yd are characterized by dominant polysphaeridium zoharyi dinoflagellate cysts the finding of assemblages dominated by p zoharyi in the open ocean is unusual because today similar assemblages are restricted to lagoonal settings it is postulated that the highly saline mixed layer and the strong density gradient which characterized arabian sea hydrography after h6 h4 and the yd simulated a shallow seafloor thereby enabling germination of cysts prior to sinking the strong density gradient following cold stadials should have facilitated the rapid reestablishment of a pronounced omz during interstadials

field and modelling studies of cambrian carbonate cycles virginia appalachians reply abstract field studies coupled with computer modelling of carbonate cycles in the elbrook conococheague formations middle to upper cambrian in the appalachians have helped define the mechanisms of formation the sequence is up to 1 6 km thick and composed of cyclic peritidal carbonates these formed on an aggraded rimmed shelf on a mature passive continental margin the cycles 1 7 m thick have lower parts of subtidal intertidal carbonate and caps of dolomitic laminite containing minor quartz arenite shale and breccia sedimentation rates for these peritidal carbonate environments exceeded long term subsidence of the platform 0 01 to 0 1 m 1 000 yr thus the shelf stayed near to sea level i e was aggraded milankovitch 20 000 to 100 000 yr low amplitude sea level fluctuations few meters superimposed on 3rd order sea level fluctuation of 1 to 3 m y duration and less than 20 m amplitude caused periodic submergence of the gently sloping platform less than 0 02 m km slopes resulting in deposition of over 400 peritidal cycles in about 26 m y cycles that formed during 3rd order sea level rise are thick and limestone rich whereas those formed during 3rd order fall are thin quartzose and highly dolomitized the modelling suggests that fewer and thinner cycles formed during the long term falls compared to the rises reflecting decreased accommodation cycle frequency decreases into areas of lower subsidence rate open marine cycles typical of the outer shelf and cycles formed during 3rd order sea level rise contain digitate bioherms grainstone and ribbon carbonates in lower parts they reflect high subsidence rate and an open marine setting inner shelf cycles and cycles that formed during 3rd order sea level fall commonly are thrombolitic or have thin subtidal parts grainstone conglomerate or stromatolite and reflec the low subsidence rates interior areas of quaternary carbonate shelves are characterized by incipiently drowned facies and pinnacle reefs and are punctuated by soil caliche horizons and karst surface that reflect 100 m glacio eustatic sea level fluctuations in contrast many ancient shelves like the cambro ordovician shelf of the appalachians were flat topped and dominated by cyclic peritidal sequences lacking evidence of high amplitude sea level fluctuations such aggraded shelves may represent the typical state of mature carbonate shelves that formed in response to low amplitude milankovitch sea level fluctuations as opposed to the large scale fluctuations that typified the quaternary

atlantic eocene planktonic foraminiferal paleohydrographic indicators and stable isotope paleoceanography reconstruction of atlantic ocean vertical and meridional water characteristics is based on combined synoptic fossil census data stable isotope records and measurements of individual planktonic foraminiferal species correlations between planktonic foraminiferal indices and specific water types and or chemical conditions are used to trace seven stages in the history of atlantic circulation during eocene climatic changes 1 warm equable probably saline productive ocean of the early eocene characterized by lowest meridional and vertical thermal gradients and the maximal extent of tropical surface water 2 early middle eocene expansion of subtropical waters and faunas accompanying the first climatic cooling and eutrophication of equatorial surface waters 3 maximal partitioning of water types faunas and bioprovinces in middle eocene zone p11 accompanying maximum planktonic foraminiferal diversity accelerated near surface and deepwater cooling and intensified upwelling 4 latest middle eocene zone p14 maximal planktonic foraminiferal evolutionary overturn during accelerated cooling deep and surface water ventilation and transformation of tropical surface water habitat with the expansion of temperate water types and faunas this accompanied the reduction of meridional heat transport in boundary currents 5 late eocene bottom water and middle latitude cooling broadening of meridional temperature gradients and expanded oxygen minimum but faunal homogenization following the decreased import of mediterranean water ourflow 6 weakening and or shoaling of the nutricline an oxygen minimum and the thermocline preceding a diminution of primary productivity at the eocene oligocene boundary and 7 earliest oligocene low productivty ocean marked by diminished vertical thermal contrasts and homogeneous foraminiferal faunas dominated by small sized individuals the increased areal extent of upwelling with the outcropping of cooler waters over large geographic regions provides an important climatic forcing mechanism in the latest middle and late eocene

dinoflagellate cyst stratigraphy of the eocene oligocene transition in central italy abstract eight dinoflagellate cyst zones based on the massignano and monte cagnero sections in central italy provide high resolution control for the eocene oligocene e o transition most of these zones have been recognized in the time equivalent contessa highway section and are calibrated against previously established magneto and biostratigraphies the invasion of the mediterranean area by several higher latitude dinoflagellate taxa marks the e o boundary as characterized by the last occurrence of the hantkeninids planktic foraminifers calibrated against a horizon just above the youngest normal polarity event within chron c1 3r quantitative and qualitative dinoflagellate events across the e o boundary allow the recognition of warmer and cooler successive intervals of sea surface temperature in addition to apparent sea level fluctuations our data indicate that latest eocene warm conditions and a sea level highstand were rapidly replaced by short term cooler conditions and a lowstand across the e o boundary horizon following a shortterm warmer interval and a highstand during the earliest oligocene a second cool and lowstand episode occurred this cool interval was of greater magnitude and duration than the one at the e o boundary horizon and may correspond to the globally recognized cooling event reported from the basal part of chron c1 3n

bartonian to priabonian dinoflagellate cyst biostratigraphy and paleoenvironments of the m karcha section in the southern tethys margin rif chain northern morocco abstract palynological analyses were performed on the eocene sediments of the m karcha section which is located in the taza region structural tsoul unit eastern external rif northeastern morocco the palynological content of this section is composed essentially of well preserved and diverse dinoflagellate cyst assemblages allowing detailed taxonomic determinations age assignments biostratigraphic correlations and paleoenvironmental interpretations other palynomorphs such as spores pollen grains and foraminiferal linings are rare and therefore not taxonomically determined up to the genus level 131 dinoflagellate cyst species were identified age assignments are based on dinocyst bioevents considered previously as potential biostratigraphic markers of the bartonian and priabonian including the lowest occurrences los of glaphyrocysta semitecta impagidinium dispertitum rhombodinium perforatum cooksonidium capricornum stoveracysta ornata stoveracysta sp 2 of brinkhuis and biffi 1993 and lo and highest occurrence ho of schematophora speciosa the quantitative palynological analyses based mainly on dinoflagellate cysts through the m karcha section revealed an inner neritic generally lagoon environment with a low productivity alternated with short episodes of the open marine influence

the role of nutrient availability in bioerosion consequences to carbonate buildups abstract zooxanthellate organisms which are among the major carbonate producers on coral reefs are highly adapted to nutrient deficient conditions and tend to be outcompeted by filamentous or fleshy algae if nutrients are abundant reef dwelling bioeroding organisms on the other hand seem to increase in abundance with increasing availability of nutrient and food resources maximum rates of calcium carbonate production in a reef system are comparable in magnitude to maximum rates of bioerosion the dynamic interplay between accretion destruction of coral reefs is therefore likely to be strongly influenced by nutrient availability nutrient availability may also influence development of carbonate facies in reef systems that develop in oligotrophic waters skeletal sands and framework should dominate carbonate buildups in systems that develop in mesotrophic waters enhanced bioerosion should reduce much of the skeletal material to carbonate muds increasing the prevalence of mud rich facies eutrophic conditions should result in bioeroded hardgrounds and carbonate depositional hiatuses when carbonate accumulation rates fail to equal or exceed rates of local relative sea level rise reefs drown bored and lithified pavements with crusts of ferromanganese oxides phosphates or glauconite often separate shallow reef from overlying deeper water deposits nondeposition bioerosion and evidence for low redox potentials at the sediment water interface all implicate excess nutrient availability as a factor in reef drowning some carbonate depositional hiatuses and bioerosional surfaces are local phenomena evidence of responses to local increases in nutrient availability resulting from submergence of soils runoff or topographic upwelling others appear to reflect regional or worldwide events because many carbonate producing organisms have life history strategies specialized to nutrient deficient conditions they are unable to compete when nutrients become plentiful events that triggered ocean turnover or sharp increases in the rate of deep ocean circulation would have increased sea surface nutrient availability worldwide such eutrophication could have caused widespread extinctions in reef communities because eutrophication promotes bioerosion details of the fossil records of those events are probably lost in bioerosional hiatuses

a high resolution north sea eocene dinocyst zonation abundant dinoflagellate cysts dinocysts from eocene strata of the north sea exhibit a consistent succession of events based on the analysis of 120 wells from quadrant 3 in the north to quadrants 21 and 22 in the south these events have a constant relationship with stratigraphic sequences and subsequences throughout the area eight eocene dinocyst zones and 23 subzones and the uppermost palaeocene apectodinium augustum biozone are defined by last occurrence or abundance events the north sea dinocyst succession is similar to that in denmark northwest germany belgium the netherlands and southern england permitting correlation with calcareous nannoplankton zones for sections in these areas and hence allowing correlation of north sea stratigraphy with northwest european and worldwide events

eocene to oligocene dinoflagellate cysts from the tattofte section western external rif northwestern morocco biostratigraphy paleoenvironments and paleoclimate abstract the palynological analysis of the eocene oligocene succession from the tattofte section in the western external rif northwestern morocco reveals the presence of well preserved and diverse assemblage rich in dinoflagellate cysts dinocysts qualitative analyses especially of the dinocysts differentiate the individual stages of the deposits while quantitative analyses permit paleoenvironmental and paleoclimatic interpretations we assign the lower part of the tattofte section to the middle eocene lutetian and bartonian and its upper part to the upper oligocene chattian and define a hiatus spanning the late eocene priabonian and early oligocene rupelian the dinocyst marker events used for the biostratigraphic interpretations include the first and last occurrences of marker species such as batiacasphaera compta castellodinium compactum cerebrocysta bartonensis distatodinium biffii distatodinium paradoxum distatodinium ellipticum enneadocysta arcuata homotryblium floripes hystrichokolpoma bullatum impagidinium velorum lentinia serrata pentadinium imaginatum rhombodinium spinula saturnodinium perforatum and ynezidinium brevisulcatum as well as the chiropteridium spp acmes and we equate the chattian with the dinocyst distatodinium biffii zone of brinkhuis et al 1992 changes in the relative abundances of selected dinocyst groups spores and pollen lead to the distinction from oldest to youngest of four marine environments 1 marginal marine to coastal inner neritic under relatively warm water during the middle eocene 2 outer neritic to oceanic during a transgressive regime in the early chattian 3 fluctuating restricted to open marine in the middle chattian and 4 shallow coastal to open marine due to sea level fall at the top of the section in the latest chattian suggested by the chiropteridium spp acmes the acmes of selected thermophilic dinocyst taxa such as polysphaeridium spp and homotryblium spp suggest warm water marine conditions which may be related to the middle eocene climatic optimum meco and late oligocene warming

dinoflagellate species and organic facies evidence of marine transgression and regression in the atlantic coastal plain abstract palynological evidence is used to date and interpret depositional environments of sediments of campanian maestrichtian and early danian ages cored in three wells from south carolina and georgia the evidence is usefil for distinguishing environments which lithofacies evidence indicates a range from nonmarine to coastal to inner neritic shallow shelf numerous dinoflagellate species and an organic facies defined abundant amoprphous debris amorphous debris facies distinguish shallow shelf sediments deposited during marine transgression the nearshore amorphous debris facies of late campanian age consists of heterogenous assemblages dominated by palaeohystrichophora infusorioides deflandre or hystrichosphaerina varians may the farther offshore amorphous debris facies of late early maestrichtian to late maestrichtian age consists of heterogenous assemblages dominated by glaphyrocysta retiintexta cookson and or areoligera medusettiformis wetzel the larger number of dinoflagellate species in the offshore facies represents the maximum transgression detected in the investigated interval a multiple occurrence datum defined by the combination of first appearance klast appearances and sole occurrence of dinoflagellate species at the base of each interval distinguished by the amorphous debris facies provides the first evidence of marine transgression relatively small organic residues consisting of intertinite and few or no palynomorphs define the inertinite facies in nonmarine deltaic and in coastal lagoonal tidal flat interdistributary bary sediments dinocyt s are absent in the nonmarine sediments and are represented by few species and few specimens in the coastal inertinite faceis a third organic facies vascular tissue facies is defined by the abundance of land plant tissue sporomorph species including those of the normapolles pollen group and of pteridophyte spores comprise a large proportion of the total palynomorph flora in the inertinite and vascular tissue facies the vascular tissue facies occurs in the proximal prodelta and nearshore shallow shelf lithofacies of early maestrichtian age baed in the sequence of organuic facies dinoflagellate species abundance and lithofacies in the investigated wells the nonmarine and coastal inertinite facies was first deposited and was followed during the late campanian by a marine trangression when the nearshore amorphous debris facies was deposited this was followed in the early maestrichtian by the influx of terrigenous organic matter vascular tissue facies in response to deltaic progradation on the shallow shelf a marine regression occured towards the close of the early maestrichtian emplacing the coastal inertinite facies the major marine transgression occured near the end of the early maestrichtian developing a farther offshore amorphous debris facies on an expanded continental shelf which persisted through the late maestrichtian the inertinite facies returned during marine regression in the approximate position of the maestrichtian danian boudnary

paleogene calcareous nannoplankton biostratigraphy of northwestern europe abstract the classic paleogene stages thanetian cuisian lutetian bartonian ludian and stampian defined in the epicontinental deposits of the anglo paris basin s are placed within a standard biostratigraphic framework based on an analysis of their calcareous nannoplankton floras relatively precise biostratigraphic correlations can be made with some chronostratigraphic units e g lutetian while biostratigraphic resolution of others e g ludian is limited important hiatuses are recognized between certain chronostratigraphic units only the base of the lutetian late np14 and bartonian mid np16 stages can be precisely determined in terms of calcareous nannoplankton zones with the recent study of the magnetic polarity history of the paleogene of southern england and recent advances in magnetobiostratigraphic correlations in deep sea cores it is possible to interpret the paleogene history of the anglo paris basin s in a synoptic global framework in which paleomagnetic stratigraphy provides the chronologic and eustatic variations the graphic units of northwestern europe within rather than at the boundaries of i e at dynamic element redefinition of the boundaries of the standard paleogene chronostratigraphic unconformities eustatically controlled depositional cycles would result in more precise correlations in terms of standard calcareous nannoplankton biostratigraphy

a valid margules formulation for an asymmetric ternary solution revision of the olivine ilmenite thermometer with applications abstract the olivine ilmenite thermometer of andersen and lindsley 1979 was based on an incorrect formulation for the excess free energy of an asymmetric ternary solution a valid formulation is derived and used to revise the parameters of the olivine ilmenite thermometer for olivine and ilmenite that have equilibrated above 700 c temperature can be calculated from t c 273 12549 p 0 03x fa 0 01099 x gk x il 0 062 10496 x fa 5767 x gk x il x hem 38602 141550x il 47183x gk 5 67 r ln k d 6 52x fa 3 09 x gk x il x hem 16 49 109 46 x il 36 49x gk with k d x il x fo x gk x fa the revised model gives wil gkg 5767 3 09t 0 011p and gexch 7301 8 9t 0 047p t in k p in bars applications include apollo 17 breccias and kimberlites

facies anatomy of an upper cambrian grand cycle bison creek and mistaya formations southern alberta the bison creek and mistaya formations form the youngest cambrian sedimentary grand cycle exposed in banff and jasper national parks the shaly half cycle of the bison creek formation records the displacement of a carbonate bank during a major rise in sea level that can be identified in other parts of north america lithofacies of the bison creek formation fall into three recurrent associations that represent sedimentation in shallow subtidal storm dominated shelf settings the mistaya formation records the reestablishment of carbonate bank deposition probably due to a decrease in the rate of sea level rise and includes two facies associations that represent a mosaic of shallow subtidal to supratidal environments the grand cycle was terminated by a sea level rise possibly eustatic in nature that drowned the carbonate platform the overlying shales mudstones packstones grainstones and rudstones of the survey peak formation mark a return to subtidal storm dominated shelf conditions

provenance of the northern part of the kahramanmaras peripheral foreland basin miocene s turkey abstract the miocene kahramanmaras peripheral foreland basin kpfb resemble to classic foreland basin model with small differences in the classic model both the accretionary wedge and foredeep extend lengthways parallel to the plate margin in addition accretionary wedge includes wedge top basin or piggy back basin that extends parallel to foredeep however the accretionary wedge of the kpfb contains small half graben type basins that obliquely intersect the plate margin between the arabian plate and the anatolide taurides platform due to the irregular shape of the plate boundary tectonic lineaments controlled the shape and orientation of these basins and larger main depocentre of the kfpb which were predominantly filled with deep sea sediments this paper focuses on the provenance of features of the kfpb predominantly was fed from the northern basin margin while also aiming to resolve the complex basin evolution that occurred during the miocene clasts of palaeozoic and mesozoic limestone and ophiolites are common components of the confined deep water clastic systems which evolved as elongated trenches in the north western sector of the kpfb during the early middle miocene during the middle miocene continuous thrusting of the northern basin margin to south caused depocentre migration to south east through the basin interior at that time the north east and central depocentres of the kpfb were filled primarily by clasts of ophiolite and metamorphic units the tectonic control on basin fill architecture can be observed anywhere in the kfpb the principal tectonic features controlled the geometry and orientation of the canyon the channel geometry of the deep water slope on the northern basin margin the frequency and distribution of slump slide debris flows and the overall pattern of sedimentation cycles in the stratigraphy of the slope and the central basin floor some basin sectors have continuously reactivated and as a result different sediment entry points with substantial local accumulation of sediment and deformation have evolved on the slope and basin floor three scales of provenance were used to investigate the source rock a field based observation and analysis of conglomerate clasts b modal analysis of sandstone facies and c geochemical analysis all of which were in agreement

isotopic and distributional evidence of a planktonic habit for the foraminiferal genusstreptochilus bro nnimann and resig 1971 abstract oxygen and carbon isotope analyses show that the biserial foraminiferal genusstreptochilus which was originally described from pelagic sediments on the eauripik rise and ontong java plateau lived deep in the upper water column within the oxygen minimum layer the species ofstreptochilus average from 4 to 19 of the foraminiferal assemblages in which benthic forms compose less than 1 or 2 specimens ofstreptochilus are selectively dissolved when in contact with the bottom water mass their rapid evolutionary turnover of less than a few million years and their wide areal distribution in the equatorial indo pacific are indicative of planktonic foraminifera aside from usefulness of the species ofstreptochilus as stratigraphic indices these neogene biserial planktonic foraminifera are potential indices of paleoceanographic stratification

dinoflagellate cysts as environmental indicators in surface sediments from the congo deep sea fan and adjacent regions abstract forty nine surface sediment samples from the congo deep sea fan and adjacent hydrographic environments were prepared palynologically and analyzed for fossilizable dinoflagellate cysts the main objective was to investigate the extent to which cysts reflect present day hydrography and therefore may be used downcore as paleoceanographic indicators the region sampled covers a range of marine environments including the congo river plume the area of pronounced upwelling off west central africa and a nearshore offshore gradient from coastal to oceanic waters this is the first study of the effect of a major tropical river plume on associated cyst assemblages cyst counts were low particularly near the river mouth and furthest offshore a combination of statistical treatments was used to analyze the surface cyst assemblages including cluster analysis correspondence analysis and canonical correspondence analysis this helped to identify five distinctive sample groupings representing the main ecological signals in the cyst assemblage data group a dominated by spherical brown protoperidinioid cysts is an upwelling signal group b dominated by the cosmopolitan species o centrocarpum is the main signal for the river plume effect interpreted as reflecting the environmental instability this creates group c dominated by s delicatus with accessory o centrocarpum characterizes the outer plume somehow reflecting the mixing of progressively diluted river plume water and the surrounding oceanic waters group d with high proportions of impagidinium and nematosphaeropsis together with o centrocarpum and s delicatus characterizes the location of the angola benguela front group e with mainly impagidinium species is an oceanic signal the identification of nutrients and water stability as main determining factors influencing cyst signals has implications for cyst based paleoenvironmental interpretations using transfer functions which are developed almost exclusively from comparisons with more easily available data for sea surface temperature salinity and sea ice

sequence stratigraphic interpretations from palynofacies dinocyst and lithological data of upper eocene lower oligocene strata in southern mississippi and alabama u s gulf coast abstract this paper presents new information on the sequence stratigraphy of the upper eocene lower oligocene strata in southern mississippi and alabama based on palynological and lithological data from five sections by integrating lithological characteristics with palynofacies assemblages several dinocyst paleoecological groups the deflandrea group and the abundance of reworked dinocysts in samples paleobathymetric curves were reconstructed and used to revise the sequence stratigraphy of the area we identified a maximum flooding surface in the middle of the shubuta clay formation in southern mississippi and dated it as latest eocene in southern alabama the eocene oligocene boundary was placed within a condensed section representing about 0 19 ma and it coincided with the shubuta clay vicksburg group contact this condensed section is equivalent to the accumulation of the upper shubuta and red bluff formations in southern mississippi the forest hill mint spring contact which has been interpreted as a sequence boundary that merged with a transgressive surface does not correlate with the tejas a ta 4 3 4 4 sequence boundary of haq et al 1988 the pachuta marl and lower shubuta clay formations are constituents of a late eocene transgressive systems tract in southern mississippi but this systems tract extended to the shubuta clay vicksburg group contact in southern alabama the overlying early oligocene highstand systems tract consisted of the upper shubuta in mississippi and the red bluff bumpnose forest hill formations a thin sandstone in the mint spring was interpreted as a deposit of a possible lowstand systems tract above the sequence boundary in one southern mississippi section in general the mint spring marl and marianna limestone constituted a transgressive systems tract

palynofacies and sea level changes in the middle coniacian late campanian late cretaceous of the east coast basin new zealand abstract a palynofacies analysis of four sections through the paton and herring formations of the east coast basin in southern marlborough indicates that the two formations were deposited on the inner to mid shelf in a marine environment with conspicuous input of plant material from adjacent land area the paton formation was deposited on the inner to mid shelf under oxic conditions and in proximity to a river delta possibly in a deltafront setting its lower part is clearly less marine than its upper part pointing to an overall deepening trend with time the deposition of the herring formation took place farther offshore on the mid shelf in a mud dominated environment under poorly oxygenated conditions at the sediment water interface following a landward shift of shoreline a stratigraphic analysis of changes in palynofacies and lithology through the four sections allows a breakdown of the succession into seven depositional sequences separated by unconformities or their correlative conformities a regional sea level curve for the middle coniacian upper campanian in the east coast basin is proposed on the basis of the inferred sequences and chronostratigraphic control from dinoflagellate biostratigraphy the sea level cycles thus inferred for the east coast basin show a poor correlation with the re scaled haq cycle chart suggesting that regional tectonics rather than eustasi controlled the east coast basin sequences

crystallization of titaniferous chromite magnesian ilmenite and armalcolite in tholeiitic suites in the karoo igneous province titaniferous chromite up to 8 wt tio2 and magnesian ilmenite up to 10 wt mgo coexist at the base of the differentiated tholeiitic mount ayliff intrusion in the karoo province of southern africa suggesting that the original magma was tio2 rich picritic lavas with 3 tio2 from the lebombo monocline of the karoo province also contain microphenocrysts of magnesian ilmenite up to 6 wt mgo and armalcolite up to 7 wt mgo these oxide mineral associations and compositions are atypical of tholeiitic magmas in which chromite usually has less than 1 wt tio2 ilmenite less than 3 wt mgo and armalcolite is rarely a primary mineral experiments have been conducted at one atmosphere pressure on a range of compositions to determine the effect of tio2 on the crystallization and composition of chromite ilmenite and armalcolite the results indicate that increasing the tio2 content of picritic magmas increases the tio2 content of the spinel mainly at the expense of al2o3 whereas cr2o3 is not affected spinel compositions in the mount ayliff intrusion with over 45 wt cr2o3 less than 10 wt al2o3 and 8 wt tio2 were duplicated in experiments on a picrite at temperatures of about 1 200 c at the ni nio buffer increasing fo2 from fayalite magnetite quartz to ni nio buffer is shown to increase the crystallization temperature of armalcolite and to decrease that of ilmenite the total feo content of the liquid has little influence on the crystallization temperature of these phases the tio2 content of the liquid when either ilmenite or armalcolite crystallizes varies inversely with sio2 content the mgo content of the liquid at which ilmenite or armalcolite crystallizes depends upon the tio2 content of the starting composition with naturally occurring and experimetally determined saturation being demonstrated for liquids with 5 wt mgo and 5 5 wt tio2 the partition coefficent for mgo between armalcolite or ilmenite and liquid is about 1 5 observed magnesian armalcolite and ilmenite compositions in picrite lavas both minerals and in the mount ayliff intrusion ilmenite only are consistent with crystallization from a tio2 rich magma with approximately 5 wt mgo the fe23 tio5 component of armalcolite in the picrite lavas matches those formed experimentally at temperatures of 1 150 1 110 c and fo2 of the ni nio to ni nio 1 log unit similarities also exist between the compositions of chromite ilmenite and armalcolite and liquid fraction ation trends of some hawaiian high tio2 lavas and the experimental studies presented here

low productivity and slow deep water circulation in mid cretaceous oceans paleofertility estimates are derived from organic carbon accumulation rates determined in nonbioturbated mid cretaceous deep sea deposits using organic carbon preservation factors observed in laminated sediments from anoxic holocene environments the estimated mid cretaceous primary production rates are as much as an order of magnitude lower than those measured in today s oceans an evaluation of dissolved oxygen budgets using a simple oceanic circulation model indicates very low deep water renewal rates in mid cretaceous oceans 28 references 2 tables 4 figures

a model for the palaeoenvironmental distribution of larger foraminifera based on late middle eocene deposits on the margin of the south pyrenean basin ne spain abstract on the margin of the south pyrenean basin the late middle eocene sediments represent a well preserved regressive system permitting determination of the distribution of larger foraminifera along the depth gradient eocene deposits are compared with distribution patterns of recent larger foraminifera based on taxa occupying comparable positions along similar ecological gradients eocene taxa reveal by their test morphology a similar response to specific ecological conditions to that recorded for recent foraminifera four assemblages characterise an open marine shelf they range from the lower limit of the photic zone to the lower part of the upper photic zone two assemblages characterise the upper part of the upper photic zone and indicate respectively two different substrates firm or soft below the photic zone no larger foraminifera exist and the foraminiferal assemblages are dominated by smaller benthic foraminifera

mid to late eocene organic walled dinoflagellate cysts from odp leg 171b offshore florida mid to late eocene organic walled dinoflagellate cysts from odp leg 171b offshore florida

chrome spinels from the jinchuan ni cu sulfide deposit gansu province people s republic of china chrome spinels occur in olivine rich cumulates in the jinchuan intrusion host to one of the largest known accumulations of magmatic ni cu in the world the chemistry and mode of occurrence of these spinels is compared with those in two other similar but unmineralized mafic ultramafic intrusions in the same belt the jinchuan intrusion contains mg poor chromites with widely varying tio 2 contents showing many features that are typical of chromites in normal tholeiitic layered intrusions wide compositional variance occurs on the scale of single thin sections and is attributed to reaction between cumulus chromite and trapped intercumulus liquid this process operated extensively even on grains that were armored by cumulus olivine crystals different reaction paths correlate with the abundance of sulfides in the rock the unmineralized intrusions show similar reaction trends but are offset from the jinchuan trends yejili spinels are generally higher in al and ga while zangbutai chromites are systematically higher in fe super 3 jinchuan spinel olivine pairs record equilibration temperatures well below the solidus and are slightly but significantly lower than blocking temperatures recorded at yejili the jinchuan ore zone contains low cr high fe super 3 chromites that are unusual and distinctive a plausible model for these unusual compositions is that these grains originated as normal aluminous spinels crystallizing from the parent silicate melt and subsequently became enlarged and modified during crystallization of the sulfide melt ti enriched chromites enclosed within sulfides record a prehistory of extensive reaction with trapped liquid sulfide associated chromites from jinchuan are strongly nickel depleted relative to expected ni values for their fe super 3 content when compared with the barren intrusions this feature combined with the distinctive chemistry of the sulfide related spinels may have applications in the use of heavy resistate minerals during exploration distinctively high ti chromites are also a feature of intrusions associated with the karoo flood basalts suggesting that jinchuan may have a similar affinity however tio 2 enrichment in chromite can be a product of interaction with differentiated trapped liquid as indicated by similar trends in lava lakes layered intrusions and at sudbury and therefore cannot be taken to prove unusually ti rich parent magmas

deep sea benthonic foraminiferal faunal turnover near the eocene oligocene boundary abstract eocene oligocene deep sea benthonic foraminifera in d s d p site 277 in the southwest pacific have been analyzed to determine the benthonic foraminiferal response to the development of the psychrosphere near the eocene oligocene boundary biostratigraphic ranges of 41 taxa show that 23 taxa are found throughout the late eocene to early oligocene sequence while 18 taxa exhibit first or last occurrences comparison of the faunal changes in site 277 with a benthonic foraminiferal oxygen isotope record shows that the development of the psychrosphere did not have a profound effect upon the benthonic foraminifera and the overall faunal change preceding and subsequent to the bottom water circulation event occurred gradually the inferred water mass event affected the relative abundance of one species epistominella umbonifera the lack of major faunal changes at the eocene oligocene boundary in site 277 probably reflects either wide environmental tolerances of the benthonic foraminifera or a bottom water temperature change less than 3 c examination of previously published benthonic foraminiferal biostratigraphic data from d s d p sites 167 171 357 360 363 and 400a and deep sea ostracode data from d s d p leg 3 show faunal changes occurred during discrete intervals in the middle eocene early oligocene the faunal patterns from these data and from site 277 show that the eocene oligocene cooling event did not cause rapid catastrophic changes of the benthonic faunas of the open ocean although significant faunal changes are associated with the water mass event in sites 167 171 and 400a the benthonic faunal changes in middle eocene early oligocene time are consistent with the gradual decrease of inferred bottom water temperatures based on previously published oxygen isotopic data the 18 o eocene oligocene enrichment of 0 76 is a major event in the southern ocean oxygen isotopic record but is considerably less in magnitude than the 1 75 2 00 change that occurred gradually from mid early eocene to the eocene oligocene boundary the benthonic foraminiferal and isotopic data indicate that bottom water circulation may have developed during the middle eocene to early oligocene interval with the 3 c bottom water cooling near the eocene oligocene boundary representing part of this development

lower ordovician trilobites from the baumann fiord formation ellesmere island arctic canada sections through member b of the baumann fiord formation on the bache peninsula ellesmere island arctic canada contain a range of lithofacies indicating deposition in shallow subtidal settings above storm wave base macrofossils are generally rare but low diversity trilobite dominated faunas occur in a section near sanddola creek the only other fossils common in the collections are poorly preserved gastropods all of the trilobite species are apparently new and four are formally named licnocephala sanddoelaensis peltabellia baumannensis bolbocephalus ellesmerensis and ceratopeltis bachensis the species ceratopeltis forteyi is introduced for material previously described from north greenland rare additional species of licnocephala and jeffersonia are reported in open nomenclature the trilobites occur in three stratigraphically and lithologically distinct associations with species diversity ranging from two to four closest comparisons of the trilobite species all indicate that member b shou

irregular plate boundary controls on foreland basin sedimentation miocene kahramanmaras foreland basin se turkey abstract the northern movement of the arabian plate led to the development of a compressional regime in the south eastern part of turkey after the late cretaceous the collision of the arabian plate with the anatolide taurides platform and subsequent development of the kahramanmaras foreland basin at the beginning of the miocene evolved as a result of this movement an irregular plate geometry or promontory of the arabian plate caused partitioning of the plate margin precollision collision postcollision this irregular plate boundary was delimited by western and northern boundary faults and an interior basin fault the nw oriented small wedge top basins on the overlying anatolide taurides platform obliquely cut through the foredeep basin the region across the wedge top basin on the irregular promontory of the underlying arabian plate contains different sedimentation depocentres small fining upward submarine fan deposits including pebbly channel deposits and coarsening upward lobe sequences are located at the centre of the irregular part of the plate in the tanir region and overlie planktic foraminifera bearing claystones these submarine fan sediments pass outboard into distal interbedded turbidite claystones and siltstones in a downdip direction s se the boundary fault intersection of the promontory led to the development of a submarine slope environment with irregular sea floor topography in the firniz area 4 5 km south east of the tanir region the slump deposits sandy debrites and fine grained thin bedded turbidites filled this region structural alignments and seismicity associated with the plate margin were the main controlling factors on the geometry of the depocentre sediment quantity sediment input sedimentary facies local sea level changes and post sedimentary deformation in the kahramanmaras foreland basin

neritic southern extratropical foraminifera and the terminal eocene event abstract if the terminal eocene event tee records a major bolide impact or other extraterrestrial happening then there ought to be disruption of benthonic foraminiferal communities especially in rather shallow neritic environments we record the arrivals and departures of 180 species in a composite succession through the later middle eocene late eocene and earliest oligocene in southern australia the rate of new arrivals increases at each of several transgressions each of which also marks a climatic amelioration the sharpest increase in rate of departure is found at a regional regression within the latest eocene there is no evidence of major disruption of the fauna at the end of the eocene the tee on this data was not extraterrestrial in origin and was hardly cataclysmic the study suggests instead that the origins of late eocene biotic change should be sought through earthly configurations of climate and sea level

emplacement and crystallization time for the bushveld complex the bushveld complex formed by the crystallization of successive basaltic magmatism may be of the order of several million years for example the columbia river basalts hooper injections of magma which were sufficiently closely spaced in time that each previous magma had not cooled and differentiated 1988 were erupted in the period 17 12 ma with minor eruptions for a further 5 my although most outpouring significantly before the addition of the next one to constrain the emplacement and crystallization times a thermal model is presented occurred within the first 2 my it is now recognized that large intrusions were not emplaced in a single pulse but which permits the investigation of the rate of cooling of magma in an intrusion repeatedly subjected to magma addition and subresult from multiple magma injection the question is how rapidly were magma chambers such as the bc traction such modelling indicates that magmas injected into the bushveld complex were emplaced within 75 000 years at that filled and how much magma was involved answers are relevant to the dynamics of melt production storage and time injection into the complex ceased the volume of rock in the eastern and western limbs is 370 000 600 000 km however transport in the mantle and crust this paper describes a thermal modelling technique not previously applied a quantitative evaluation of the cr budget in the formation of chromitite layers indicates that large volumes of magma cannot be to magma chambers which can be used to analyse this process and to obtain an estimate of the emplacement accounted for in the preserved rock sequence similarly an evaluation of the incompatible trace element abundances such as those for zr time to present this model it is necessary to discuss the stratigraphy size and connectivity of the different limbs and k suggests that the chamber was open and that large volumes of differentiated magma escaped the volume of magma therefore of the bushveld complex and to consider the extent of tapping of the magma chamber as well as its filling greatly exceeded the preserved volume of cumulate rocks giving an estimated magma volume of over 1 10 km an average the term bushveld complex has been given several meanings in the literature and according to the south emplacement rate of 13 km year is indicated by these calculations african commission on stratigraphy 1980 includes not only the ultramafic mafic layered rocks but also the sills beneath the intrusion volcanic rocks which pre date the

nannoplankton productivity and diagenesis in the rhythmically bedded toarcian aalenian fiuminata section umbria marche apennine central italy abstract pelagic rhythmic lithotypes crop out in the fiuminata section central italy middle toarcian aalenian in age and provide a good example of cyclic sedimentation within the calcari e marne a posidonia unit the whole succession is made up of a nutty yellowish rhythmic sequence of marlstone and marly limestone beds with similar thicknesses calcareous nannofossil quantitative analyses give a good biostratigraphic resolution of the studied interval and also reveal a different assemblage composition of the carbonate rich lithotypes with respect to the carbonate poor ones schizosphaerella spp which is the dominant taxon in the assemblage shows higher abundances in the limestones conversely coccoliths are more abundant and diverse in the marls such data emphasize a relationship between palaeoenvironmental conditions in the water column nannoplankton productivity and the depositional pattern of the sedimentary basin diagenetic overprint can also account for the different assemblage composition in marlstones and limestones the effects of diagenesis on the original thanatocoenosis have been detected through a detailed analysis of nannofossil preservation this study points out that diagenesis has enhanced without obliterating a primary palaeoenvironmental signal nannoplankton productivity varied in response to differing conditions in the water column schizosphaerella spp seems to be more productive concomitant with the deposition of carbonate rich sediments with bioturbation and abundant radiolarians probably while these sediments were deposited a more vigorous vertical mixing of the water column occurred and trophic resources were good a stable and diversified community of coccolithophorids was established in times of clay deposition when the surface waters were stratified due to their density and nutrients were available both at the sea bottom and in the water column due to the runoff the differing nannoplankton assemblage is tentatively interpreted in terms of a response to milankovitch orbital climatic cycles

sequence biostratigraphy and paleoenvironmental reconstruction in the early eocene figols group of the tremp graus basin south central pyrenees spain the dinoflagellate cyst palynofacies and foraminiferal records from the early eocene figols group of the spanish pyrenees exhibit major changes associated with relative sea level fluctuations and variations in efficiency of the fluvial systems the mixed siliciclastic carbonate marine succession exposed in the merli esdolomada area was deposited on the shelf in a tectonically active basin under oxic conditions in shallow to moderately deep marine waters close to the lower boundary of the photic zone influenced by river discharge from adjacent emerged lands sedimentary cycles are mainly recorded by fine grained deposits the paleoenvironmental interpretation of palynological and calcareous microfaunal records allows the definition of depositional sequences and enables to trace basinward surfaces identified in more proximal settings by means of sedimentological facies analysis at the same time the solid regional stratigraphic framework already available for the figols group allows new insights on the paleoecology of extinct taxa the merli esdolomada section me spans two 3rd order sequences the upper sequence reflects more marginal marine conditions than the lower one thus pointing to an overall shallowing trend with time in the lower sequence the maximum flooding interval is characterised by a rich and diverse microfauna highest relative abundances of marine phytoplankton and typically neritic dinoflagellate cyst dinocyst assemblages dominated by spiniferites and cordosphaeridium the final phase of the highstand systems tract in proximity of the main sequence boundary is characterised by a decrease in abundance and diversity of dinocysts with the dominance of the lagoonal genus polysphaeridium and by decreased microfaunal diversity discorbids miliolids larger foraminifers palynological records permit the reconstruction of activation and deactivation phases of the fluvial systems variations in runoff from the hinterland nutrient delivery to the sea and productivity in surface waters of the tremp graus basin the overall abundance of spiniferites and the scarcity of peridinioid cysts lingulodinium pediastrum and botryococcus algae are interpreted to indicate oligotrophic conditions during the deposition of the investigated succession recurrent intervals where the temporary disappearance of spiniferites corresponds to highest relative abundances of operculodinium and herbaceous debris are the main evidence for river plumes and denote periods of enhanced fluvial discharge reflecting a milankovitch type cyclicity the rotalia group which shows abundance peaks of cuvillierina spp in the shallower intervals is often associated with these episodes thus suggesting for this taxon more tolerance to turbidity than larger foraminifera within the maximum flooding zone a thalassiphora patula acme corresponding to the local disappearance of homotryblium is deemed to record the distal expression of a fluvial activation which triggered water salinity stratification despite broad morphological similarities homotryblium exhibits more cosmopolitan preferences than polysphaeridium which is instead confirmed as a lagoonal euryhaline taxon the increase of spinizonocolpites pollen toward the top of the figols group records the northwestward migration of nypa mangrove palms from southern europe during the mid early eocene

paleoclimatic analyses of middle eocene through oligocene planktic foraminiferal faunas quantitative faunal analyses and oxygen isotope ranking of individual planktic foraminiferal species from deep sea sequences of three oceans are used to make paleoceanographic and paleoclimatic inferences species grouped into surface intermediate and deep water categories based on 18o values provide evidence of major changes in water mass stratification and individual species abundances indicate low frequency cool warm oscillations these data suggest that relatively stable climatic phases with minor cool warm oscillations of 0 5 m y frequency are separated by rapid cooling events during middle eocene to early oligocene time five major climatic phases are evident in the water mass stratification between middle eocene through oligocene time phase changes occur at p14 p15 p15 p16 p20 p21 and p21 p22 zone boundaries and are marked by major faunal turnovers rapid cooling in the isotope record hiatuses and changes in the eustatic sea level a general cooling trend between middle eocene to early late oligocene is indicated by the successive replacement of warm middle eocene surface water species by cooler late eocene intermediate water species and still cooler oligocene intermediate and deep water species increased water mass stratification in the latest eocene p17 indicated by the coexistence of surface intermediate and deep dwelling species groups suggest that increased thermal gradients developed between the equator and poles nearly coincident with the development of the psychrosphere this pattern may be related to significant ice accumulation between late eocene and early late oligocene time

contrasting parental magma compositions for the hongge and panzhihua magmatic fe ti v oxide deposits emeishan large igneous province sw china many 260 ma mafic ultramafic layered intrusions including hongge and panzhihua in the emeishan large igneous province southwestern china host world class fe ti v oxide ore deposits these two most important ore bearing intrusions show differences in lithology and mineral chemistry the most important orebodies in the hongge intrusion occur as concordant layers in the middle part of the intrusion closely associated with clinopyroxenites titanomagnetite and mg rich ilmenite are the major ore minerals of the hongge deposit coexisting clinopyroxene contains 1 7 wt tio2 these data indicate high ti parental magma for the hongge ore bearing clinopyroxenites in the panzhihua intrusion the most important orebodies also occur as concordant layers but in its lower part instead of middle part in contrast with the hongge deposit the most important host rocks of the panzhihua deposit are gabbros not clinopyroxenites in addition ilmenite is rare and titanomagnetite is predominant in the panzhihua deposit coexisting clinopyroxene in the panzhihua deposit contains 1 6 wt tio2 the contrasting lithologic and mineral compositions indicate that the parental magma for the hongge deposit has higher tio2 than that for the panzhihua deposit the compositions of clinopyroxene from the panzhihua and hongge deposits indicate that their parental magmas are also different in mgo feo and trace element ratios as well calculations using average experimental mg fe exchange coefficient and trace element partition coefficients between clinopyroxene and magma show that the hongge parental magma has higher mgo feo ratios and more fractionated mantle normalized trace element patterns than the panzhihua parental magma the estimated compositions of the parental magmas for the hongge and panzhihua ore bearing lithologies resemble the average compositions of the longzhoushan type high ti basalts and ertan type intermediate ti basalts in the emeishan large igneous province respectively the new trace element data from this study together with available sr nd isotope data for the ore bearing intrusions from literature support a new petrogenetic model involving selective assimilation of newly subducted stagnant oceanic gabbroic slab above the deep seated emeishan mantle plume this process and subsequent contamination with the upper crust played an important role in the variation of parental magma compositions between the hongge and panzhihua magmatic oxide ore deposits abundant fe ti oxide ore deposits associated with less evolved basaltic magma in the emeishan large igneous province than elsewhere in the world are attributed to selective assimilation of newly subducted stagnant oceanic lithospheric slab by the ascending mantle plume derived picritic magma that was originally undersaturated with fe ti oxides

the petrology of some picrites from mauna loa and kilauea volcanoes hawaii the mineralogy and chemistry of picrites from mauna loa and kilauea have been investigated to evaluate for hawaiian tholeiitic picrites the contrasting genetic models which have been proposed for these mg rich volcanics namely products of direct crystallization of high mg melts 20 25 mgo or the result of accumulation of olivine phenocrysts into less mg rich melts genetic interpretations rely heavily on mg fe partitioning relations between olivines and their picrite hosts although the 100 mg mg fe2 ratios m of picrites are wide ranging m 73 6 82 9 for fe2o3 feo 0 15 with mgo as high as 27 8 the average 100 mg mg fe ratios mg of the cores of olivine phenocrysts megacrysts show only restricted compositional variation mg 87 2 89 0 successive olivine generations are progressively more fe rich olivine liquid mg fe partitioning data and the mn and ni abundances in olivine phenocrysts collectively indicate that they were precipitated by mg rich basaltic melts with 12 14 mgo spinel compositions range from liquidus magnesiochromites occurring mainly as inclusions in olivine phenocrysts to groundmass titanomagnetites which crystallized at nearsolidus temperatures the cr2o3 contents and m values of liquidus magnesiochromites suggest that their parent melts were neither mg rich picritic mgo 20 nor relatively mg poor basaltic types