carbonate factories a conundrum in sedimentary geology abstract describing characterizing and interpreting the nearly infinite variety of carbonate rocks are conundrums intricate and difficult problems having only conjectural answers that have occupied geologists for more than two centuries depositional features including components rock textures lithofacies platform types and architecture all vary in space and time as do the results of diagenetic processes on those primary features approaches to the study of carbonate rocks have become progressively more analytical one focus has evolved from efforts to build reference models for specific phanerozoic windows to scrutinize the effect of climate and long term oscillations of the ocean atmosphere system in influencing the mineralogy of carbonate components this paper adds to the ongoing lively debates by attempting to understand changes in the predominant types of carbonate producing organisms during the mesozoic cenozoic while striving to minimize the uniformitarian bias our approach integrates estimates of changes in ca2 concentration in seawater and atmospheric co2 with biological evolution and ecological requirements of characteristic carbonate producing marine communities the underlying rationale for our approach is the fact that co2 is basic to both carbonates and organic matter and that photosynthesis is a fundamental biological process responsible for both primary production of organic matter and providing chemical environments that promote calcification gross photosynthesis and hypercalcification are dependent largely upon sunlight while net primary production and e g subsequent burial of organic matter typically requires sources of new nutrients n p and trace elements our approach plausibly explains the changing character of carbonate production as an evolving response to changing environmental conditions driven by the geotectonic cycle while identifying uncertainties that deserve further research with metazoan consumer diversity reduced by the end permian extinctions excess photosynthesis by phytoplankton and microbial assemblages in surface waters induced by moderately high co2 and temperature during the early mesozoic supported proliferation of non tissular metazoans e g sponges and heterotrophic bacteria at the sea floor metabolic activity by those microbes especially sulfate reduction resulted in abundant biologically induced geochemical carbonate precipitation on and within the sea floor for example with the opening of tethyan seaways during the triassic massive sponge microbe boundstones the benthic automicrite factory formed steep massive and thick progradational slopes and locally mud mounds as tectonic processes created shallow epicontinental seas photosynthesis drove lime mud precipitation in the illuminated zone of the water column the resulting neritic lime mud component of the shallow water carbonate factory became predominant during the jurassic paralleling the increase in atmospheric pco2 while the decreasing importance of the benthic automicrite factory parallels the diversification of calcifying metazoans phytoplankton and zooplankton with atmospheric pco2 declining through the cretaceous the potential habitats for neritic lime mud precipitation declined at the same time peak oceanic ca2 concentrations promoted biotically controlled calcification by the skeletal factory with changes produced by extinctions and turnovers at the cretaceous tertiary boundary adaptations to decreasing ca2 and pco2 coupled with increasing global temperature gradients i e high latitude and deep water cooling and strategies that efficiently linked photosynthesis and calcification promoted successive changes of the dominant skeletal factory through the cenozoic larger benthic foraminifers protist protist symbiosis during the paleogene red algae during the miocene and modern coral reefs metazoan protist symbiosis since late miocene

tropical sea surface temperature reconstruction for the early paleogene using mg ca ratios of planktonic foraminifera 1 to understand the climate dynamics of hypothesized past greenhouse intervals it is essential to constrain tropical sea surface temperatures sst yet existing proxy records give conflicting results here we present the first mg ca based study of pre quaternary sst and investigate early paleogene late paleocene through late middle eocene 58 6 39 8 ma tropical temperatures using planktonic foraminifera belonging to the genus morozovella from ocean drilling program site 865 on allison guyot western central equatorial pacific ocean calcification temperatures similar to or warmer than modern tropical sst are calculated using a range of assumptions regarding diagenesis temperature calibration and seawater mg ca long term warming is observed into the early eocene 54 8 49 0 ma with peak sst between 51 and 48 ma and rapid cooling of 4 c beginning at 48 ma these findings are inconsistent with the 18o based sst previously estimated for this site

intra and extrabasinal controls on fluvial deposition in the miocene indo gangetic foreland basin northern pakistan the miocene siwalik group upsection the chinji nagri and dhok pathan formations in northern pakistan records evolving fluvial systems within the himalayan foreland basin sedimentological variations are evaluated with respect to local regional and global controls on fluvial deposition and basin filling thick 5 m to tens of metres sandstones are composed of channel bar and fill deposits of low sinuosity meandering and braided rivers which formed large low gradient sediment fans or megafans river flow was dominantly toward the south east the proportion of thick sandstones varies in all siwalik sections on three scales and reflects similar variations in palaeochannel size and grain size 1 small scale variations are generally tens of metres thick and reflect the alternation of thick sandstones channel belt deposits and mudstone dominated strata overbank deposits through the section 2 medium scale variations are roughly one hundred to a few hundreds of metres thick and primarily correspond to changes in channel deposit thickness but also to the degree of superposition of channel deposits and or to changes in the number of channel belt deposits per unit of section and 3 large scale variations formation scale are greater than one km thick and primarily correspond to changes in channel deposit thickness time scales of small medium and large scale variations appear to be on the order of 104 105 and 106 years respectively the chinji nagri transition is characterized by increases in channel deposit proportion sandstone thickness palaeochannel size and discharge mean grain size of sandstones and sediment accumulation rates and a decrease in avulsion period the nagri dhok pathan transition is characterized by decreases in channel deposit proportion sandstone thickness palaeochannel size and discharge mean grain size of sandstones and avulsion period and a further increase in sediment accumulation rates formation boundaries across the potwar plateau decrease in age toward the west the chinji nagri transition ranges in age from 10 9 12 7 ma and the nagri dhok pathan transition ranges in age from 9 3 10 1 ma small scale variations are attributable to repeated river avulsions triggered by autocyclic processes and or mountain front tectonism e g faulting earthquakes medium scale variations are attributable to local changes in the position of large sediment fans also triggered by autocyclic processes and or mountain front tectonism the chinji nagri transition records the diversion or establishment possibly due to river piracy of a larger river system in the area river diversion or piracy probably took place within the mountain belt and is attributable to increasing and spatially variable mountain belt uplift rates and possibly the development of associated mountain front deformational structures the nagri dhok pathan transition records the diversion of the larger river system out of the area and the establishment of a smaller river system this diversion is attributable to progressively increasing rates of mountain belt uplift and basin subsidence the regional palaeoclimate throughout the time interval studied was apparently constant and eustatic sea level changes apparently had no effect on deposition in the area

the apparent paradox of abundant foramol facies in low latitudes their environmental significance and effect on platform development recent studies of low latitude carbonates from se asia and australia have revealed deposits and platform types that do not fit easily into the perceived view of warm water tropical carbonates the sediments are classified as a foramol or foralgal facies and are dominated by non framework building light dependent biota such as perforate larger benthic foraminifera coralline algae and sometimes halimeda although ancient foramol deposits are often interpreted as an indication of non tropical conditions foramol facies have long been known from the tropics yet the environmental conditions in which they form are poorly known the aims of this paper are to evaluate how these deposits are best classified and more importantly whether there are any overriding controls that influence their common development in low latitude areas and if resultant platform development is affected the deposits are all best grouped within the photozoan association james n p 1997 the cool water depositional realm in james n p clarke j a d eds cool water carbonates sepm special publication 56 1 20 an assignment synonymous with warm water conditions the facies were also found to develop in conditions of limited light or oligophoty all the platforms described are characterised by having extensive areas of oligophotic facies generally in water depths extending down from 20 m but sometimes in shallower waters platforms types vary from land attached rimmed shelves homoclinal and distally steepened ramps to isolated banks and platforms but all have extensive moderate to deep photic zone development of oligophotic facies some workers might assign these platforms to the incipiently drowned platform type read j f 1985 carbonate platform facies models american association of petroleum geologists bulletin 69 1 21 however a morphological assignment is preferred here to signify that many of the deposits did not or may not form through drowning limited light in moderate to deeper depths of the photic zone often in regions with a reduced depth euphotic high light zone is seen as key to the extensive development of these deposits and the resultant platforms these conditions are often developed in humid low latitude areas of high terrestrial runoff and therefore regions of reduced water salinity or in areas of nutrient upwelling reduced water clarity due to nutrients plankton blooms suspended particulate matter upwelling and strong currents all promote the development of oligophotic conditions and facies on a regional scale time periods of relative rises in sealevel can also promote oligophotic facies development the findings of this study have broader implications for the development of low latitude platforms beyond australasia and during time periods when non framework building oligophotic biota are dominant sediment contributors the reconstruction of past climatic conditions based on study of foramol grain assemblages requires careful study to distinguish warm water deposits from those formed in cool waters

eocene bipolar glaciation associated with global carbon cycle changes the transition from the extreme global warmth of the early eocene greenhouse climate 55 million years ago to the present glaciated state is one of the most prominent changes in earth s climatic evolution it is widely accepted that large ice sheets first appeared on antarctica 34 million years ago coincident with decreasing atmospheric carbon dioxide concentrations and a deepening of the calcite compensation depth in the world s oceans and that glaciation in the northern hemisphere began much later between 10 and 6 million years ago here we present records of sediment and foraminiferal geochemistry covering the greenhouse icehouse climate transition we report evidence for synchronous deepening and subsequent oscillations in the calcite compensation depth in the tropical pacific and south atlantic oceans from 42 million years ago with a permanent deepening 34 million years ago the most prominent variations in the calcite compensation depth coincide with changes in seawater oxygen isotope ratios of up to 1 5 per mil suggesting a lowering of global sea level through significant storage of ice in both hemispheres by at least 100 to 125 metres variations in benthic carbon isotope ratios of up to 1 4 per mil occurred at the same time indicating large changes in carbon cycling we suggest that the greenhouse icehouse transition was closely coupled to the evolution of atmospheric carbon dioxide and that negative carbon cycle feedbacks may have prevented the permanent establishment of large ice sheets earlier than 34 million years ago between 55 and 34 million years ago earth switched from a warm greenhouse ocean climate system to the icehouse that we now enjoy frustratingly the few oceanographic datasets that exist for this key period are of low resolution tripati et al now present measurements of sediment and foraminiferal geochemistry that provide the first continuous high resolution records for this period the data suggest that northern hemisphere glaciation started 34 million years ago rather than between 10 and 8 million years ago as previously thought

a comparison of long coastal trapped wave theory with remote storm generated wave events in the gulf of california abstract moored pressure temperature and current observations of low frequency coastal trapped wave ctw events in the gulf of california are examined in the context of long wave ctw theory mode 1 ctws that are generated by summer tropical storms are consistent with the occurrences and propagation speeds of the observed wave events in the gulf the mode 1 ctw generation however occurs farther north than observed presumably due to insufficient wind data the mode 1 and observed across shelf wave structure in the gulf are similar in that alongshelf currents are nearly depth independent in 100 m water depth the pressure response is strongest at the coast with decay offshore and with depth and downwelling occurs over the shelf with the amplitude of the mode 1 density response within a factor of two of the observed response the main discrepancies between the mode 1 and observed wave structure are that the speed of the mode 1 alongshelf current increases toward the coast while the weakest observed sp

a field based study on variation in mg ca and sr ca in larger benthic foraminifera 1 the mg ca and sr ca ratios of foraminifera are used as proxies of paleotemperature although the mg ca is found to be related with temperature in planktonic foraminifera the reliability of this proxy in benthic foraminifera has yet to be established it is essential therefore to understand the minor elements composition and their relation to ambient water parameters in different benthic foraminiferal species in this study a systematic field based study was carried out on larger benthic foraminifera lbf of okinawa japan to assess if mg ca and sr ca in their tests could be used as proxies of seawater temperature five seasonal samples were collected from the reef flat to pick live specimens of amphistegina lessonii neorotalia calcar calcarina hispida calcarina gaudichaudii baculogypsina sphaerulata and marginopora kudakajimaensis the mg ca in a lessonii was 60 mmol mol while in the remaining five species the values were 200 mmol mol substantially higher than that recorded in planktonic and smaller benthic foraminifera interspecies and intraspecies mg ca variations were fairly large even in samples of the same season the sr ca were quite uniform 2 mmol mol across the species and seasons the correlations between test mg ca and sr ca and ambient water temperature and salinity were found to be poor the possible reasons are 1 the influence of biological activities particularly the photosynthesis respiration cycle of algal symbionts and 2 masking of the true relationship due to an averaging effect in whole test analysis of species having longer a life span in view of this it is suggested that the whole shell mg ca and sr ca of lbf is not an apt proxy of paleotemperature

a three dimensional model of the mean and seasonal circulation of the gulf of california 1 the mean and seasonal circulation of the gulf of california is simulated with a three dimensional numerical model forced by the pacific ocean through specifying the sea level the temperature and the salinity fields at its entrance at the sea surface the wind and the heat and freshwater fluxes are specified the model reproduces the observed mean and seasonal variability of sea level of heat and salt balances and the sea surface temperature sst climatology it also reproduces the general surface circulation of the northern gulf which consists of a seasonally reversing basin wide gyre it is found that tides and heat fluxes are both indispensable to reproduce the spatial structure and temporal evolution of the sst tides provide the mixing to upwell the cooler subsurface waters in the large islands area and the heating from the surface raises the sst the general circulation of the southern part of the gulf is due to the wind and the pacific forcing in the ekman layer two periods of anticyclonic circulation and one cyclonic per year occur below this layer two cyclonic periods develop in the northern part the tides play an important role in producing mean residual currents and both tides and winds compete against the pacific forcing to produce a cyclonic and anticyclonic circulation once a year contrary to conclusions of previous studies the thermohaline circulation is found to be unimportant in the gulf

paleogene stable isotope events the oxygen isotope record in paleogene benthic foraminifera shows that at the base of the paleogene the ocean deep waters had a temperature of about 10 c rising to about 12 c at the base of the eocene and cooling between 51 ma and 49 ma to about 9 c the most dramatic event occurred just after the eocene oligocene boundary at about 35 8 ma when ocean deep waters cooled by several degrees within 104 105 yr probably in association with temporary glaciation in the antarctic region another more intense glacial event in antarctica may have occurred later in the oligocene at about 31 ma and a third near the top of the oligocene at 24 ma in the marine carbon isotope record a very rapid negative excursion occurred precisely at the cretaceous tertiary boundary a recovery to unusually positive values in the late paleocene was followed by a second negative excursion close to the paleocene eocene boundary that was even more extreme in magnitude although it was not as rapid these major carbon isotope events permit very accurate stratigraphic correlation there are many other smaller features in the carbon isotope record that will also prove useful for this purpose

eocene to oligocene benthic foraminiferal isotopic record in the bay of biscay we present here oxygen and carbon isotopic records of eocene to oligocene benthic f oraminif era from two bay of biscay deep sea drilling project dsdp sites 119 and 401 18o of benthic foraminifera increases 1 9 from a middle eocene minimum zones p10 p11 to an earliest oligocene maximum zone np21 approximately 1 4 of the increase in benthic foraminiferal 18o occurs during the late eocene to earliest oligocene zones p15 16 np21 previous results from other north atlantic dsdp sites 400a and 398 have significantly lower 18o values of benthic foraminifera some by as much as 2 refs 1 3 we believe that these differences result from diagenetic alteration of the sediments in the deeper buried sites 400a and 398

conflicting isotopic and biotic evidence for tropical sea surface temperatures during the tertiary abstract the biotic evidence from a varied group of shallow water organisms including mangroves zooxanthellate corals mainly reefal and larger foraminifera suggests that sea surface temperatures at low latitudes during the tertiary from at least the early eocene to the middle miocene were subtropical to tropical in nature and similar to temperatures prevailing at low latitudes at the present day 20 28 c in a recent paper shackleton 1984 the suggestion is made on the basis of oxygen isotope studies of foraminiferal shells that low latitude sea surface temperatures during the palaeogene and much of the neogene were invariably lower than those in similar regions today with a stable temperature of around 18 c this paper discusses the conflicting evidence for sea surface temperatures obtained from palaeontological and isotopic sources and suggests that palaeotemperatures derived from some isotopic studies are too low to account for the distribution and diversity of many tertiary tropical and subtropical biotas

global change and modern coral reefs new opportunities to understand shallow water carbonate depositional processes human activities are impacting coral reefs physically biologically and chemically nutrification sedimentation chemical pollution and overfishing are significant local threats that are occurring worldwide ozone depletion and global warming are triggering mass coral bleaching events corals under temperature stress lose the ability to synthesize protective sunscreens and become more sensitive to sunlight photo oxidative stress also reduces fitness rendering reef building organisms more susceptible to emerging diseases increasing concentration of atmospheric co2 has already reduced caco3 saturation in surface waters by more than 10 doubling of atmospheric co2 concentration over pre industrial concentration in the 21st century may reduce carbonate production in tropical shallow marine environments by as much as 80 as shallow water reefs decline worldwide opportunities abound for researchers to expand understanding of carbonate depositional systems coordinated studies of carbonate geochemistry with photozoan physiology and calcification particularly in cool subtropical transition zones between photozoan reef and heterotrophic carbonate ramp communities will contribute to understanding of carbonate sedimentation under environmental change both in the future and in the geologic record cyanobacteria are becoming increasingly prominent on declining reefs as these microbes can tolerate strong solar radiation higher temperatures and abundant nutrients the responses of reef dwelling cyanobacteria to environmental parameters associated with global change are prime topics for further research with both ecological and geological implications

climatic responses to tropical sea surface temperature changes on a greenhouse earth the uncertainty associated with tropical sea surface temperatures ssts during past greenhouse climates may have important and unaccounted for effects we explore early paleogene climatic sensitivity to changes in tropical subtropical ssts with a general circulation model we demonstrate that tropical sst changes have local and far field climatic effects underscoring their importance in understanding greenhouse climates the responses of winds upwelling and surface water balance to tropical sst changes are substantial our results indicate that current tropical sst reconstructions may have a significant cool bias despite corrections and that the existence of hot 30 c tropical ssts may be realistic for greenhouse climate intervals including the eocene

stable warm tropical climate through the eocene epoch earth s climate cooled from a period of extreme warmth in the early eocene epoch ca 50 ma to the early oligocene ca 33 ma when a large ice cap first appeared on antarctica evidence from the planktonic foraminifer oxygen isotope record in deep sea cores has suggested that tropical sea surface temperatures declined by 5 10 degrees over this interval eventually becoming much cooler than modern temperatures here we present paleotemperature estimates from foraminifer isotopes and the membrane lipids of marine crenarcheota from new drill cores in tanzania that indicate a warm and generally stable tropical climate over this period we reinterpret the previously published isotope records in the light of comparative textural analysis of the deep sea foraminifer shells which shows that in contrast to the tanzanian material they have been diagenetically recrystallized we suggest that increasingly severe alteration of the deep sea plankton shells through the eocene produced a diagenetic overprint on their oxygen isotope ratios that imparts the false appearance of a tropical sea surface cooling trend this implies that the long term eocene climatic cooling trend occurred mainly at the poles and had little effect at lower latitudes

late paleocene early eocene tethyan carbonate platform evolution a response to long and short term paleoclimatic change abstract the early paleogene experienced the most pronounced long term warming trend of the cenozoic superimposed by transient warming events such as the paleocene eocene thermal maximum petm the consequences of climatic perturbations and associated changes on the evolution of carbonate platforms are relatively unexplored today modern carbonate platforms especially coral reefs are highly sensitive to environmental and climatic change which raises the question how sub tropical reef systems of the early paleogene reacted to gradual and sudden global warming eutrophication of shelf areas enhanced co 2 levels in an ocean with low mg ca ratios the answer to this question may help to investigate the fate of modern coral reef systems in times of global warming and rising co 2 levels here we present a synthesis of tethyan carbonate platform evolution in the early paleogene 59 55 ma concentrating on coral reefs and larger foraminifera two important organism groups during this time interval we discuss and evaluate the importance of the intrinsic and extrinsic factors leading to the dissimilar evolution of both groups during the early paleogene detailed analyses of two carbonate platform areas at low egypt and middle spain paleolatitudes and comparison with faunal patterns of coeval platforms retrieved from the literature led to the distinction of three evolutionary stages in the late paleocene to early eocene tethys stage i late paleocene coralgal dominated platforms at low to middle paleolatitudes stage ii a transitional latest paleocene platform stage with coralgal reefs dominating at middle paleolatitudes and larger foraminifera dominated miscellanea ranikothalia assilina platforms at low paleolatitudes and stage iii early eocene larger foraminifera dominated alveolina orbitolites nummulites platforms at low to middle paleolatitudes the onset of the latter prominent larger foraminifera dominated platform correlates with the paleocene eocene thermal maximum the causes for the change from coral dominated platforms to larger foraminifera dominated platforms are multilayered the decline of coralgal reefs in low latitudes during platform stage ii is related to overall warming leading to sea surface temperatures in the tropics beyond the maximum temperature range of corals the overall low occurrence of coral reefs in the paleogene might be related to the presence of a calcite sea at the same time larger foraminifera started to flourish after their near extinction at the cretaceous paleogene boundary the demise of coralgal reefs at all studied paleolatitudes in platform stage iii can be founded on the effects of the petm resulting in short term warming eutrophic conditions on the shelves and acidification of the oceans hampering the growth of aragonitic corals while calcitic larger foraminifera flourished in the absence of other successful carbonate producing organisms larger foraminifera were able to take over the role as the dominant carbonate platform inhabitant leading to a stepwise tethyan platform stage evolution around the paleocene eocene boundary this szenario might be also effective for threatened coral reef sites

heterozoan carbonates in oligotrophic tropical waters the attard member of the lower coralline limestone formation upper oligocene malta abstract photozoan and heterozoan skeletal assemblages are controlled by their trophic requirements i e light based photosynthesis versus other sources and temperature photozoan associations tend to dominate tropical and subtropical waters whereas heterozoan carbonate systems tend to occur in cooler waters and in localised areas that are affected by nutrient rich upwelling or terrestrial runoff because of the wide climatic spectrum in which heterozoan carbonates are found their interpretation is often problematic we present a high resolution analysis of the attard member of the lower coralline limestone formation upper oligocene malta the biotic associations and palaeolatitudinal reconstructions suggest that carbonate sedimentation took place in tropical waters under oligotrophic conditions an important factor controlling the spread of heterozoan assemblages in the late oligocene of malta seems to be related to the palaeoecology and evolution of zooxanthellate the limited capacity of corals to thrive in high light conditions and to form a wave resistant reef promoted the diffusion of heterozoan assemblages

a numerical investigation of the annual variability in the gulf of california the observations of sea level at the annual frequency in the gulf of california are reproduced both in amplitude and phase with a horizontal two dimensional linear two layer model the main forcing agents through which variability is explained are wind stress and the action of the pacific ocean which excites an internal wave in the mouth of the gulf the surface heating is shown to play a secondary role the response of the basin is qualitatively similar to that observed that is an energetic circulation in the upper layer cyclonic in summer and anticyclonic in winter compared to a weaker and opposite circulation in the bottom layer as well as a transversely averaged horizontal heat flux equal both in amplitude and phase to that calculated with historical hydrographic data the results of the simulation show that variability across the gulf is as important as the longitudinal variability

oligocene plant ecological strategies in low latitude asia unraveled by leaf economics abstract the oligocene represents an important epoch in the history of the stepwise global climate evolution from a warm climate to a cooler climate the change probably introduced selective pressures influencing ecological strategies and caused the past ecosystems restructured however little is known about the paleoenvironment and adaptive plant ecological strategies in the terrestrial realm of the low latitudes here based on the plant fossils from the baigang formation of the baise basin low latitude china the paleoclimate paleovegetational type and paleoecological strategy are reconstructed using leaf physiognomic analyses integrated plant record and leaf economics spectrum respectively the results show that under a warm and wet sub tropical climate with low seasonality the oligocene baise flora was dominated by slow return maximized resource retention species but mixed with a considerable proportion of fast return rapid resource acquisition species these ecological strategies might promote the community to maximize the use of limited living resources and at the same time to better tolerate potential extreme situations these results allow us to examine which ecological strategies that fossil plants selected under a given paleoclimate condition and might potentially provide a clue to predict the direction of ecological strategy changes in a future climate change scenario

past co2 changes and tropical sea surface temperatures the relationship between past co2 variations and tropical climate change on time scales of millions of years is reviewed explanations for cretaceous and early cenozoic climate change often involve higher atmospheric co2 levels climate models predict that such increases should have been associated with warmer tropical sea surface temperatures ssts however sparse mid cretaceous 18o based sst estimates from low latitude calcareous plankton are 1 0 1 5 heavier than predicted initial evaluations indicate that changes in salinity may not alleviate model data discrepancies for calcareous 18o and that interpretation of altered latitudinal 18o gradients in terms of increased poleward heat transport due to warm saline bottom water wsbw formation would require very large levels of wsbw production at least 60 sv calcareous 18o records may not always record true sst patterns as 18o analyses from phosphatic groups which are less sensitive to diagenesis indicate ssts 5 c higher this latter conclusion is supported by a number of other fossil groups which indicate temperatures warmer than those estimated from calcareous 18o in order to more rigorously test the paleo co2 hypothesis and indeed the models used to forecast future climates it is desirable to intensify investigations of past climate change in low latitudes in order to determine whether these preliminary conclusions stand the test of further scrutiny

late eocene tropical sea surface temperatures a perspective from panama 1 we have reconstructed mean annual coastal temperatures and seasonality during the eocene priabonian 36 6 40 ma using oxygen isotope profiles of shallow marine aragonitic gastropod shells gatuncillo formation panama these data provide a unique opportunity to document low latitude coastal climates during a preglacial greenhouse period assuming shell oxygen isotope profiles primarily reflect changes in water temperature our results indicate water temperatures in a middle to outer shelf setting 20 50 m depth varied by 6 8 c and mean annual temperatures mat were 26 c these temperatures are in agreement with pollen based surface temperature reconstructions for the late eocene and are consistent with other eocene mollusk based tropical coastal temperature estimates but are at odds with the few eocene foraminiferal based estimates of mean annual tropical sea surface temperatures 17 22 c

an oligocene multi species foraminiferal oxygen and carbon isotope record from odp hole 758a indian ocean paleoceanographic and paleo ecologic implications abstract an oligocene basal miocene zones p19 p22 n4 oxygen and carbon isotope stratigraphy is presented based on mixed benthic foraminiferal faunas and different species of planktic foraminifers from eastern indian ocean odp hole 758a lack of covariance in planktic and benthic 18 o ratios indicates that many oligocene sea level fluctuations including the major fall at 30 ma are not of glacio eustatic origin 18 o values suggest that test morphology is a poor indicator of preferred depth habitat of oligocene planktic foraminifers also some groups show considerable shifts in preferred depth habitat reconstructed surface water temperature was nearly constant during the investigated period but even assuming a large antarctic icecap values are unrealistically low 18 20 c most likely water masses with markedly different oxygen isotopic composition existed this poses great problems for quantitative temperature reconstructions planktic foraminiferal species show similar 13 c ratios indicating well mixed surface waters this contrasts with the strong oxygen isotopic gradient which suggests well stratified surface waters during the oligocene the difference in 13 c ratio between the average ratio of planktic foraminiferal species and the benthic foraminifers 13 c p b shows an inverse relation with the known circulation intensity record and thus with productivity this 13 c pattern is interpreted as being caused by the presence of younger bottom waters at this site during periods with lower temperatures and or larger antarctic ice sheets

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

role of climate in partial drowning of the queensland plateau carbonate platform northeastern australia abstract ocean drilling program leg 133 core data samples and geophysical data logs and seismics were analyzed to document late miocene early pliocene partial drowning of the queensland plateau carbonate platform off northeast australia the modern plateau consists of a mosaic of pinnacle reefs and larger 10 50 km reefs representing relicts of early to middle miocene buildups late miocene early pliocene floatstones packstones and mudstones rich in the larger benthic foraminifers lepidocyclina and cycloclypeus drilled in a transect of sites across the drowned margin of a middle miocene buildup show that the late pliocene partial drowning of the platform was preceded by 4 myr of neritic carbonate deposition without any reefs the carbonate factory was unable to aggrade to sea level during this period as indicated by the lack of any shallowing trend in the succession monitoring of the miocene to recent neritic shedding pattern on the windward and leeward side of a pinnacle reef on the queensland plateau supports this interpretation shedding on the leeward side of the reef which records periods of active reef growth played a minor role during the late miocene increased during the pliocene and reached very high values during the late pliocene and pleistocene shedding on the windward side of the reef which was active during lowstands of relative sea level occurred during the late middle early late miocene and during the pliocene quaternary the data presented here when combined with paleoceanographic data points to low surface water temperatures 17 19 c as a major factor which suppressed reef growth during the late miocene early pliocene period

an upper bound for the tidally rectified current at one location on the southern flank of georges bank abstract long term current observations at 45 and 75 m at one location on the southern flank of georges bank in water 85 m deep were examined for evidence of tidal rectification loder has shown analytically that rectification of the strong semidiurnal tidal current can cause a mean along bank flow and thus may partially drive the observed clockwise circulation around georges bank the amplitude of the tidally rectified along bank flow is proportional to the squared amplitude of the cross bank tidal current a simply extension of loder s model to include the weaker n2 and s2 tidal components suggests that fortnightly 354 h and monthly 661 h variations of the square of the cross bank tidal current should cause a modulation of the subtidal along bank flow the predicted ratio r of the fortnightly and monthly modulation of the along bank flow to the mean along bank flow on the southern flank was a function of position and ranged from 0 1 0 5 the amplitude of modulation of the along bank flow at 360

turnover of larger foraminifera during the paleocene eocene thermal maximum and paleoclimatic control on the evolution of platform ecosystems the larger foraminifera turnover lft during the paleocene eocene transition constitutes an important step in paleogene larger foraminifera evolution involving a rapid increase in species diversity shell size and adult dimorphism a platform to basin transect in egypt provides new data on timing and causal mechanisms through correlation with planktic biozonations and through integration with regional paleoenvironmental data the lft coincides with the boundary between shallow benthic biozones sbz4 and sbz5 and closely correlates with the paleocene eocene thermal maximum petm enhanced oligotrophy from the late paleocene onward favored the diversification of k strategist larger foraminifera we suggest that a short term eutrophication during the petm led to a temporary decline of extreme k strategist larger foraminifera species providing opportunities for new taxa with different ecological strategies to develop during post petm oligotrophic conditions these new taxa were able to evolve rapidly and soon dominated early eocene larger foraminifera assemblages whereas many paleocene taxa gradually disappeared the success of larger foraminifera during the early paleogene appears climatically controlled because of the vulnerability of corals to high surface water temperatures the late paleocene to early eocene global warming may have favored larger foraminifera at the expense of corals as the main carbonate producing component on carbonate platforms at lower latitudes

assessing offsets between the δ13c of sedimentary components and the global exogenic carbon pool across early paleogene carbon cycle perturbations 1 negative stable carbon isotope excursions cies across the paleocene eocene thermal maximum petm 56 ma range between 2 and 7 even after discounting sections with truncated records individual carbon isotope records differ in shape and magnitude from variations in the global exogenic carbon cycle through changes in 1 the relative abundance of mixed components with different 13c within a measured substrate 2 isotope fractionation through physiological change and 3 the isotope composition of the carbon source all three factors likely influence many early paleogene 13c records especially across the petm and other hyperthermal events we apply these concepts to late paleocene early eocene 58 52 ma records from lomonosov ridge arctic ocean linear regression analyses show correlations between the 13c of total organic carbon toc and two proxies for the relative contribution of terrestrial organic components to sediment toc the branched and isoprenoid tetraether index and palynomorphs we use these correlations to subtract the terrestrial component from 13ctoc and calculate marine organic matter 13c the results show that the magnitude of the cie in 13ctoc across the petm is exaggerated relative to the magnitude of the cie in 13cmom by 3 due to increased contributions of terrestrial organic carbon during the event collectively all carbon isotope records across the petm and other major climate carbon cycle perturbations in earth s history are potentially biased through one or more of the above factors indeed it is highly unlikely that any 13c record shows the true shape and magnitude of the cie for the global exogenic carbon cycle for the petm we conclude that cie in the exogenic carbon cycle is likely 4 but it will take additional analyses and modeling to obtain an accurate value for this cie

bryozoan beds in northern italy as a shallow water expression of environmental changes during the oligocene isotope event 1 abstract shifts in carbonate producing biotic communities in the geological record provide evidence of past environmental changes in the neritic realm the shallow marine calcare di nago formation exposed in the san valentino section northern italy covers the late eocene and earliest oligocene the succession is characterized by the occurrence of light dependent biota such as coralline algae and larger benthic foraminifera in the uppermost part of the section however the fossil association is dominated by bryozoans which are filter feeder organisms this ca 12 m thick interval locally contains up to 86 bryozoans while coralline algae as well as larger benthic foraminifera are absent coralline algae and nummulitid foraminifera recover in the upper part of the bryozoan beds whereas orthophragminids do not recover the gradual disappearance of larger foraminifera and coralline algae within the bryozoan dominated deposits is coeval with a pronounced positive shift in 13c based on its biostratigraphic position this positive shift is interpreted to be linked to the positive shift in 13c recognized in deep sea records shortly above the eocene oligocene boundary which in turn is associated to the positive shift in 18o leading to the oi 1 oligocene isotope event 1 cooling phase total phosphorus content increases in the bryozoan beds suggesting enhanced nutrient supply to the neritic ecosystem this phosphorous peak is coeval with the globally recognized increment in ocean productivity around the oi 1 and 13c positive shift thus disappearance of light dependent biota and the dominance of bryozoans in the platform carbonates studied are interpreted to result not necessarily from a deepening of the depositional environment but from the combination of lower sea surface temperatures and the deterioration of underwater light conditions on account of elevated turbidity in surface waters resulting from enhanced primary productivity as bryozoan beds occur in several italian localities around the eocene oligocene boundary they are interpreted to represent the regional expression of neritic carbonate depositional systems to global environmental changes occurring at the dawn of an ice house earth

a note on alongshore sediment transport on weakly curvilinear coasts and its implications abstract this paper presents a simple approximation for assessment of the alongshore sediment transport rate on dissipative weakly curvilinear coasts the approximation considers spatial variations in the wave angle and energy sediment size beach slope and type of wave breaking inside the surf zone similar approaches were employed in the past for coasts forced by high oblique waves where shoreline undulations frequently develop with our approach we can analyze more realistic situations i e alongshore relations between the sediment size and the beach slope the general expression for alongshore sediment transport is made explicit using a simple model for wave propagation the solution is used to examine the implications of the behavior of alongshore sediment transport on shoreline evolution after the analysis of the effects of variations in the wave conditions the alongshore beach slope distribution and the shoreline geometry three different shoreline tendencies were obtained for undulating shorelines migration for changes in deep water wave angle amplitude growth for increases in wave height or period and changes in shoreline geometry and wavelength changes and asymmetries for coasts with alongshore changes in beach slope our results also indicate that wave setup may enhance the formation of undulating shoreline features

tropical atlantic seasonal dynamics in the early middle eocene from stable oxygen and carbon isotope profiles of mollusk shells there are disagreements whether the tropical sea surface temperature during the warm early to early middle eocene was equal to the present temperature or significantly lower in order to determine the sea surface temperature of the eastern tropical atlantic in the early middle eocene we have established 18o and 13c profiles along the transect of growth of excellently preserved shells of turritella gastropods and a macoma bivalve from tropical west africa this method makes possible a distinction between the winter and the summer temperature the 18o and 13c data indicate sea surface temperatures of 29 31 c which declined to 23 25 c during seasonal upwelling these conditions are similar to those of today and suggest that significant seasonal dynamics prevailed in the early middle eocene tropics the new data further contradict that the tropics cooled during the generally warm early to early middle eocene as inferred in studies on foraminifera 18o

nutrient influence on fossil carbonate factories evidence from sedex extractions on burdigalian limestones miocene nw italy and s france abstract different miocene shallow water carbonate successions have been examined to test the potential of phosphorus sequential extraction sedex in studying palaeo nutrient levels and to investigate nutrient influence on carbonate factories during this epoch the coralline algal dominated sequence of the pietra da cantoni group nw italy and the bryozoan dominated sequence of the sommieres basin s france have been targeted for this study actually albeit they both developed during the burdigalian in the very same latitudinal zone they present remarkably different carbonate factories palaeontological analyses have investigated the distribution of the major groups of carbonate producing organisms throughout the successions these results have been compared with those of geochemical analyses on phosphorus and organic matter abundance testifying a clear relationship between the skeletal assemblage and the availability of nutrients as expected on the basis of modern oceanography and benthic ecology bioavailable phosphorus concentration was higher in the bryozoan dominated basin than in the coralline algal dominated basin this result strongly supports sedex sequential extraction as a viable instrument to investigate the nutrient supply in the geological record this also proves that the early miocene mediterranean carbonate factories were deeply controlled by nutrient influence with patterns similar to those observed in present day oceans moderate nutrient concentrations resulted in coralline algal dominance while high nutrient concentrations produced carbonate factories dominated by heterotrophs suspension feeders like bryozoans the euphotic zone producers which dominate in classical tropical associations were probably restricted to areas with low nutrient concentrations

inviscid quasi geostrophic flow over topography testing statistical mechanical theory numerical simulations are employed in a detailed test of the statistical mechanical description of topographic turbulence predictions of steady flows correlated with topography are given particular attention agreement between numerical and statistical mechanical results is demonstrated for a large range of parameter values and over an ensemble of random choices of topography and initial conditions

global and regional influences on equatorial shallow marine carbonates during the cenozoic abstract the se asian carbonate record allows insight into the poorly known response of equatorial marine systems to regional and global change during the cenozoic there is a marked change from larger benthic foraminifera to corals as dominant shallow marine carbonate producers in se asia around the oligo miocene boundary the early miocene acme of coral development in se asia lags oligocene coral development in the caribbean and mediterranean despite local tectonics providing apparently suitable habitable areas regional and global controls including changing co2 oceanography nutrient input and precipitation patterns are inferred to be the main cause of this lag in equatorial reefs it is inferred that moderate although falling level of co2 ca2 and ca mg when combined with the reduced salinities in humid equatorial waters all contributed to reduced aragonite saturation hindering reefal development compared with warm more arid regions during the oligocene by the early miocene atmospheric co2 levels had fallen to pre industrial levels although this was a relative arid phase globally in se asia palynological evidence indicates that the early miocene experienced everwet but more stable and less seasonal conditions than periods before or after tectonic convergence truncated deep throughflow of cool nutrient rich currents from the pacific to indian ocean around the beginning of the miocene thereby directly and perhaps indirectly though less seasonal conditions reducing nutrients it is inferred that aragonitic reefs were promoted where previously the waters had been more acidic more mesotrophic more turbid and less aragonite saturated extensive reefal development resulted in an order of magnitude expansion of shallow carbonate areas through buildup and pinnacle reef formation in the early miocene tectonics via increased habitat partitioning and reducing distances to other coral rich regions may also have contributed to enhanced reefal development declining reefal importance at the end of the early miocene resulted from uplift of land areas enhanced oceanic ventilation through thermohaline circulation and narrowing of oceanic gateways as well as increased seasonal runoff at least in se asia through initiation intensification of the monsoons implications of this study are that with current anthropogenically induced environmental changes it will be the diverse reefs of se asia that are likely to be amongst the first and hardest hit as oceanic aragonite saturation decreases and terrestrial nutrient runoff increases

late paleocene to eocene paleoceanography of the equatorial pacific ocean stable isotopes recorded at ocean drilling program site 865 allison guyot an expanded and largely complete upper paleocene to upper eocene section was recovered from the pelagic cap overlying allison guyot mid pacific mountains at ocean drilling program odp site 865 18o26 n 179o33 w paleodepth 1300 1500 m reconstructions show that the site was within a few degrees of the equator during the paleogene because no other paleogene sections have been recovered in the pacific ocean at such a low latitude site 865 provides a unique record of equatorial pacific paleoceanography detailed stable isotopic investigations were conducted on three planktonic foraminiferal taxa species of acarinina morozovella and subbotina we studied benthic foraminiferal isotopes at much lower resolution on species of cibicidoides and lenticulina nuttallides truernpyi and gavelinella beccariiformis because of their exceptional rarity the 5180 and 513c stratigraphies from site 865 are generally similar to those derived from other paleocene and eocene sections the planktonic foraminiferal records at site 865 however include significantly less short term single sample variability than those from higher latitude sites indicating that this tropical oligotrophic location had a comparatively stable water column structure with a deep mixed layer and less seasonal variability low amplitude 0 1 0 8 o oscillations on timescales of 250 000 to 300 000 years correlate between the 513c records of all planktonic taxa and may represent fluctuations in the mixing intensity of surface waters peak sea surface temperatures of 24o 25oc occurred in the earliest eocene followed by a rapid cooling of 3 6oc in the late early eocene temperatures remained cool and stable through the middle eocene in the late eocene surface water temperatures decreased further vertical temperature gradients decreased dramatically in the late paleocene and were relatively constant through much of the eocene but increased markedly in the late eocene intermediate waters warmed through the late paleocene reaching a maximum temperature of 10oc in the early eocene cooling in the middle and late eocene paralleled that of surface waters with latest eocene temperatures below 5oc extinction patterns of benthic foraminifera in the latest paleocene were similar to those observed at other pacific sites and were coeval with a short term very rapid negative excursion in 513c values in planktonic and benthic taxa as at other sites during this excursion benthic foraminiferal 5180 values decreased markedly indicating warming of 4 to 6oc for tropical intermediate waters while planktonic taxa show slight warming 1 oc followed by 2oc of cooling convergence of 5180 values of planktonic and benthic foraminifera suggests that thermal gradients in the water column in this tropical location collapsed during the excursion these data are consistent with the hypothesis that equatorial pacific surface waters were a potential source of warm higher salinity waters which filled portions of the deep ocean in the latest paleocene oxygen isotopic data indicate that equator to high southern latitude sea surface thermal gradients decreased to as little as 4oc at the peak of the excursion suggesting some fundamental change in global heat transport

an interpretation of cretaceous and tertiary biota in polar regions abstract rich fossil floras and vertebrate faunas lived within the arctic and atarctic circles during the cretaceous and paleogene these occurrences seem explicable by the nature of the thermal environments in polar regions and by the physiological responses of plants and animals allied to those that lived there there seems no need to invoke a lower tilt to the earth s axis to provide greater warmth and light in polar regions to account for these fossil records

estimating mediterranean oligocene miocene sea surface temperatures an approach based on coral taxonomic richness abstract during the oligocene and miocene shallow water carbonates of the mediterranean region were rich in scleractinian corals thriving within various depositional settings including different reef types their diversity patterns although related to a complex interplay between a suite of environmental factors and palaeobiogeography are considered to be strongly controlled by climate variability and changes in sea surface water temperature by using the quantitative relationship between present day coral taxonomic richness and prevailing sea water temperature underlined by the so called energy hypothesis we test zooxanthellate coral generic richness values from a selection of 102 oligocene miocene localities of the mediterranean region as a proxy for relative palaeotemperatures for each oligocene miocene stage generic richness values per z coral site are firstly examined together with variations of the mediterranean z coral generic pool for better testing the method and assessing its potential application patterns of generic richness and inferred palaeotemperatures are then compared with global palaeoclimatic curves based on marine oxygen stable isotopes data or other climate proxies such as palaeoclimatic records from european continental floras and from fossil coral linear extension rate results clearly show that fluctuations of coral richness derived palaeotemperatures correspond relatively well with global changes of sea water temperature especially for the entire oligocene the chattian aquitanian boundary and the late miocene the well known mid miocene climatic optimum however is not recorded suggesting that regional factors acting together with important palaeogeographical changes exerted a strong control on the generic richness of mediterranean z coral communities a remarkable decline of taxonomic richness is recorded after the burdigalian together with a gradual decrease of palaeotemperatures in the region from the middle miocene onwards to the messinian however an increase in the temperature range of z coral localities is clearly visible indicating that z coral communities were able to thrive and adapt to a wider temperature range as the mediterranean was gradually migrating northwards outside the tropical belt the energy hypothesis if used at global or regional scale can be considered a promising and reliable method for estimating cenozoic palaeotemperatures from coral or other suitable fossil assemblages of shallow water carbonates

arctic late paleocene early eocene paleoenvironments with special emphasis on the paleocene eocene thermal maximum lomonosov ridge integrated ocean drilling program expedition 302 we reconstruct the latest paleocene and early eocene 57 50 ma environmental trends in the arctic ocean and focus on the paleocene eocene thermal maximum petm 55 ma using strata recovered from the lomonosov ridge by the integrated ocean drilling program expedition 302 the lomonosov ridge was still partially subaerial during the latest paleocene and earliest eocene and gradually subsided during the early eocene organic dinoflagellate cyst dinocyst assemblages point to brackish and productive surface waters throughout the latest paleocene and early eocene dinocyst assemblages are cosmopolitan during this time interval suggesting warm conditions which is corroborated by tex86 reconstructed temperatures of 15 18 c inorganic geochemistry generally reflects reducing conditions within the sediment and euxinic conditions during the upper lower eocene spectral analysis reveals that the cyclicity recorded in x ray fluorescence scanning fe data from close to eocene thermal maximum 2 53 ma presence confirmed by dinocyst stratigraphy is related to precession within the lower part of the petm proxy records indicate enhanced weathering runoff anoxia and productivity along with sea level rise on the basis of total organic carbon content and variations in sediment accumulation rates excess organic carbon burial in the arctic ocean appears to have contributed significantly to the sequestration of injected carbon during the petm

climate changes in the early to middle miocene of the central paratethys and the origin of its echinoderm fauna abstract this study uses echinoderm diversity to assess climatic changes in the early to middle miocene of the central paratethys it is based mainly on a taxonomically standardised dataset of central paratethys echinoids supplemented by data on asteroid ophiuroid crinoid and holothuroid distributions potential constraints of the raw diversity data are explored and possible biases are identified these include a heterogeneous rock record in terms of outcrop area and facies of the preserved sedimentary rocks stage duration and sampling bias the latter was overcome by utilising rarefaction analysis to investigate species richness these analyses show that the patterns observed in the raw data are robust and not severely biased by sampling intensity the potential influence of a heterogeneous rock record was assessed by comparing surface outcrop areas of the various stages to standing diversity a second bias involving a heterogeneous rock record the non preservation of distinct habitats was overcome by carrying out within habitat comparison of standing diversity and faunal composition the observed patterns were therefore established as true signals rather than artefacts produced by various biases consequently echinoderm diversity is used to evaluate climate changes during the neogene of the central paratethys as well as to interpret minimum winter and summer sea surface temperatures in the badenian middle miocene climatic conditions during the deposition of the badenian leitha limestone were addressed along with the presence of n s gradients within the central paratethys the presently available data suggest warm temperate conditions for the late eggenburgian early burdigalian followed by a brief temperature drop in the ottnangian early late burdigalian temperatures increased again in the karpatian and a climatic optimum was reached in the early badenian a slight cooling during the middle badenian was reflected by the southwards shift of predominantly temperate genera from the northern fringes of the central paratethys in the early badenian to the central parts in the late badenian the faunal gradients observed in the early badenian of the central paratethys suggest that the boundary between the warm temperate and tropical zone lay somewhere within the paratethys at that time considering the more southerly position of the study area about 34 palaeolatitude in the early middle miocene this implies that the tropical climate zone was much wider during the early middle miocene than today biogeographic investigations of the central paratethyan echinoid faunas show that the overwhelming part of the central paratethys echinoid species are immigrants from the mediterranean area immigration occurred in three distinct waves during the late eggenburgian the karpatian and early badenian while no common echinoid species were identified between the boreal region and the central paratethys two species of asteroids from the northern most fringes of the central paratethys also occur in the north sea basin endemism is low in most of the stages except for the ottnangian when geodynamic processes and global cooling resulted in a large scale re organisation of central paratethyan faunas

biogeographic impact of the leeuwin current in southern australia since the late middle eocene abstract the leeuwin current can be tracked from the western margin of the australian continent to the southern margin by the record of fossilized organisms typical of warm water marine environments this transport smudges the normal latitudinal asymmetry in the biotas of opposing oceanic and continental margins in which the eastern margins of oceans are cooler than the western margins and warmer biotas are restricted to lower latitudes in the east the most comprehensive record is in the large benthic foraminifera although fossils of benthic invertebrates nektonic nautiloids and planktonic protists are also informative in addition organic biomarker hydrocarbons in stranded bitumens and resins demonstrate that they have travelled the same route from their ultimate sources in cenozoic sedimentary basins and modern tropical rainforests of the indonesian archipelago the earliest spoor of the current is in the later middle eocene at which time the part deflection of counter gyral circulation in the indian ocean to the southeast was stimulated by the accelerated opening of the oceanic gap between australia and antarctica thus the origin of the leeuwin current is twice the age of the previously suggested origin in the miocene the current turns on and turns off in the great australian bight during the late quaternary in concert with the interglacials and the glacials at scales of 10 5 yr the switch can be seen in the faunal succession of planktonic foraminifera which are consistent with the neritic benthic faunas of the central gulfs both communities show that at the warm peak of the last interglacial the current transported biota across the bight more strongly than it has during the holocene the cenozoic record of the past 40 ma is in the same mode at 10 6 yr scales the relevant fossils are found concurrently at major marine transgressions and warming reversals of the overall fall in global temperature however the fossil pattern is due to transport on the activated leeuwin current not merely to general warming and the spread of friendly environments to higher latitudes

the eocene expansion of nautilids to high latitudes abstract a short term return of environmental conditions similar to those of the end cretaceous is marked by the reappearance of nautiloid cephalopods in the lower middle eocene la meseta formation of seymour island antarctic peninsula previous findings have been supplemented by a collections of 33 specimens the nautiloids come from several horizons the oldest sample apparently being located close to the base of the formation telm1 the most numerous coming from the cucullaea bed of telm2 and 3 a few specimens were collected from telm4 6 the la meseta formation nautiloid assemblages developed apparently in response to one of the eocene warmings and resulting transgression of a warm sea the incursion of nautiloids into southern high latitudes was roughly coeval with their expansion to the northern european seas and the succession of faunas was parallel in both regions based on the analogy with the lower eocene london clay nautiloid assemblages an estimate of bathymetric evolution of the environment can be made by the presence of a relatively shallow water form similar to cimomia imperialis close to the base of the lower middle eocene la meseta formation telm1 marks the beginning of the marine transgression the dominant la meseta species euciphoceras argentinae was apparently an analogue of the english e regale the occurrence of which in the london clay corresponds to the highest sea level stand the presence of aturia in the higher part telm4 and 5 of the la meseta formation suggests that cold oceanic waters possibly entered the area accompanied by a sea level drop the last nautiloid telm6 is an euciphoceras sp interpreted to be indicative of shallower habitat depth limits both incursion of the nautiloids to and their disappearance from the eocene high latitudes were connected with a fundamental rearrangement of the geographic distribution of particular lineages

early paleogene temperature history of the southwest pacific ocean reconciling proxies and models we present a new multiproxy tex86 18o and mg ca marine temperature history for canterbury basin eastern new zealand that extends from middle paleocene to middle eocene including the paleocene eocene thermal maximum petm and early eocene climatic optimum eeco in light of concerns that proxy based sea surface temperature sst estimates are untenably warm for the southwest pacific during the eocene we review the assumptions that underlie the proxies and develop a preliminary paleo calibration for tex86 that is based on four multiproxy eocene records that represent an sst range of 15 34 c for the southwest pacific paleogene we show that tex86l exhibits the best fit with the eocene paleo calibration ssts derived from related proxies tex86h 1 tex86 exhibit a systematic warm bias that increases as tex86 values decrease a warm bias of 4 7 c where tex86 0 7 the tex86l proxy indicates that southwest pacific sst increased by 10 c from middle paleocene to early eocene with sst maxima of 26 28 c tropical during the petm and eeco and an sst minimum of 13 16 c cool warm temperate at the middle late paleocene transition 58 7 ma the base of the eeco is poorly defined in these records but the top is well defined in canterbury basin by a 2 5 c decrease in sst and bottom water temperature bwt in the latest early eocene 49 3 ma bwt falls from a maximum of 18 20 c in the eeco to 12 14 c in the middle eocene overall cooler temperatures are recorded in the mid waipara section which may reflect a deeper 500 m water depth and less neritic depositional setting compared with hampden and odp 1172 200 m water depth the high ssts and bwts inferred for the petm and eeco can be reconciled with eocene coupled climate model results if the proxies are biased towards seasonal maxima and the likely effect of a proto east australian current is taken into account

carbon and oxygen isotopic disequilibria of recent deep sea benthic foraminifera abstract the carbon and oxygen isotopic compositions of 149 samples of benthic foraminifera from deep sea core tops indicate that none of the nine species studied secrete calcium carbonate in isotopic equilibrium with ambient bottom water uvigerina pyrgo murrhina and oridorsalis tener are the closest to 18o equilibrium with average deviations about 0 4 while planulina wuellerstorfi and p murrhina are the closest to 13c equilibrium with average deviations about 1 p wuellerstorfi shows the most systematic relationship between 13c and bottom water apparent oxygen utilization the intraspecific variabilities in 18o and 13c suggest that estimates of bottom water paleotemperatures can be made to a precision of 0 7 c while estimates of past apparent oxygen utilization aou can be made to 35 mol kg based on intraspecific comparisons of the recent samples with fossils no temporal changes in the degree of either 18o or 13c disequilibrium have been detected for planulina wuellerstorfi uvigerina oridorsalis tener and globocassidulina subglobosa

cenozoic palaeogeography and the rise of modern biodiversity patterns the steepest latitudinal and longitudinal gradients in taxonomic diversity at the present day are those associated with tropical high diversity foci although there has been a tendency in the past to regard these features as either evolutionary cradles or museums of considerable antiquity this may not be the case within the marine realm a uniform pan tropical fauna was progressively disrupted by a series of plate tectonic events the most important of which were the early miocene c 20 ma collisions of africa arabia with europe and australia new guinea with indonesia and the middle miocene latest pliocene rise of the central american isthmus this had the net effect of establishing two main tropical high diversity foci the indo west pacific and the atlantic caribbean east pacific similar foci were also established at the same time in the terrestrial realm together with the physical isolation of antarctica these same tectonic events contributed significantly to global cooling throughout the cenozoic era this in turn led to the imposition of a series of thermally defined provinces and thus a considerable degree of biotic differentiation on a regional scale however something else seems to have been involved in the creation of very steep tropical diversity peaks this could in part be a coincidental radiation of a series of unrelated taxa or some sort of evolutionary feedback mechanism between interacting clades alternatively late cenozoic rates of origination may have been enhanced by an external forcing mechanism such as changes in orbital range dynamics

late cretaceous oceans and the cool tropic paradox oxygen isotopic proxies of paleo sea surface temperatures ssts suggest that maastrichtian about 66 million years ago tropical ssts were lower than those of today they also demonstrate that maastrichtian latitudinal sst gradients were much lower than those of the present the low maastrichtian sst gradients indicate that meridional heat transport was much greater or latitudinal differences in the balance of radiation to and from the sea surface were much less extreme during the latest cretaceous than they are today or that both conditions were true these findings challenge traditional interpretations of greenhouse late cretaceous climates

foraminiferal biofacies in a silica rich neritic sediment late eocene south australia abstract the highly siliceous blanche point formation accumulated during the late eocene zones p15 p16 in the st vincent basin when the climate was warm it differs from shelly neritic carbonates above it and below it by higher but fluctuating numbers of benthonic foraminifera of the family uvigerinidae and by high dominance in different horizons of infaunal crustacean traces and of infaunal gastropods within the blanche point formation changes from a banded siliceous opal ct sediment to a homogeneous spongolite are paralleled by biofacies changes high numbers of uvigerinidae and in part of the formation high numbers of robertinacea bolivinidae sphaeroidina cassidulina are more consistent with generally lowered levels of oxygen at the sediment surface than with other forms of environmental stress the study is consistent with a recent conclusion based on mineralogy that the abundant silica came from volcanic ash it suggests too that restricted circulation permitted biogenic and other mechanisms of fix the silica in the st vincent basin whilst silica was being flushed away from more open environments facing the nascent southern ocean

phytogeography and paleoclimatic interpretation of the maestrichtian abstract insight into the true nature of cretaceous climate can best be grained through a worldwide study of the preserved climatic indicators this study focuses on reconstructing the climate of the maestrichtian latest cretaceous based on the abundant published information from the geologic record specifically the approach taken was to reconstruct the general patterns of the terrestrial ecological biomes based on the fossil megaflora and pollen record once the biomes were delineated the climatic constraints on the present counterparts of these biomes were used to determine the prevailing climate of each region biome boundaries were recognized by discontinuities in the phytogeographic distributions of a variety of fossil plant groups detailed comparisons of fossil plant assemblages with present day climatic preferences of nearest living relatives allowed each region to be assigned to a modern biome further comparisons with fossil leaf physiognomic studies and tree ring studies integrated with an extensive database of climatically important sediments helped to refine the biomal and climatic assignments altogether 12 climatic zones corresponding to 7 major biome types have been recognized for the late cretaceous period

ichnofossils and rhizoliths of the nearshore fluvial jebel qatrani formation oligocene fayum province egypt abstract the ichnofossils and rhizoliths of the oligocene jebel qatrani formation of egypt are among the best preserved most diverse in form and most abundant of such structures yet recognized in fluvial rocks twenty one forms are described the ichnofauna contains traces domichnia fodinichnia cubichnia of probable annelid insect crustacean and vertebrate origin these include the first described fossil nest structures and gallery systems of subterranean termites isoptera the first examples of ophiomorpha from wholly fluvial rocks and the first fossil vertebrate burrows from the african tertiary rhizoliths associated with the ichnofauna and those occurring elsewhere document a variety of small wetland plants coastal mangroves and much larger trees the environment suggested by these traces is consistent with the coastal tropical to subtropical monsoonal rain forest with adjacent more open areas that is indicated by independent evidence of sedimentology paleontology and paleopedology

tropical sea temperatures in the high latitude south pacific during the eocene sea surface temperature sst estimates of 30 c from planktic foraminifera and archaeal membrane lipids in bathyal sediments in the canterbury basin new zealand support paleontological evidence for a warm subtropical to tropical climate in the early eocene high latitude 55 s southwest pacific such warm ssts call into question previous estimates based on oxygen isotopes and present a major challenge to climate modelers even under hypergreenhouse conditions 2240 ppm co2 modeled summer ssts for the new zealand region do not exceed 20 c

facies analysis and sequence stratigraphy of a miocene warm temperate carbonate ramp montagna della maiella italy abstract the uppermost oligocene lower miocene to upper miocene ramp carbonates from montagna della maiella italy form a supersequence bounded by deeply incised truncation surfaces this supersequence is subdivided into four sequences each sequence is composed of skeletal limestones in its lower part and marly limestones in its upper part the lower parts of the sequences are foramol limestones which suggest deposition in the warm temperate climate zone changes in climate oceanography and relative sea level combined to control sedimentation in the four sequences in the lower parts of the two older sequences the skeletal sands built dunes suggesting high energy conditions the dominant skeletal grains in the oldest sequence are larger foraminifers and in the next sequence they are bryozoans this change reflects cooling around the time of the aquitanian burdigalian boundary in the lower parts of the two younger sequences of middle and late miocene age sediment sheets with red algal bryozoan oncoids suggest deposition under calmer conditions transgressive and highstand systems tracts are recognized in all sequences a shelf margin systems tract may be exposed in the second oldest sequence in contrast to the situation that exists when warm water carbonates are deposited sedimentation of the foramol limestones on this isolated ramp was unable to balance accommodation during sea level rise this led to hemipelagic sedimentation during sea level highstands conglomerates resulted from reworking along flooding surfaces

tertiary ice sheet dynamics the snow gun hypothesis we observe strong negative correlation between tertiary low to mid latitude planktonic foraminiferal 18o and the difference between these data and coeval benthic foraminiferal 18o late quaternary data do not show this correlation coupling statistical model 18o comparisons and evidence for antarctic ice and ocean temperature variation we infer that tertiary ice volume recorded by tropical planktonic 18o increased as the deep ocean warmed because the isotopic signatures of deepwater temperature variation and ice volume change were of opposite sign the sum of these signals in tertiary benthic 18o became lost in the noise this renders low correlation between tertiary planktonic and benthic 18o time series compared to late quaternary data we contend that tertiary ice sheet growth was commonly driven by warming of deep water from low to mid latitude marginal seas snow gun hypothesis in contrast late quaternary ice sheets grew as deep water formed at high latitude cooled because tectonic forcing and orbital forcing at low latitude primarily controlled production and temperature variations of this warm saline deep water these influences largely dictated tertiary ice volume fluctuations through the tertiary we infer ice volume fluctuations to be an important component of sea level history on timescales between 103 and 107 years

representing topographic stress for large scale ocean models abstract interaction of eddies with seafloor topography can exert enormous systematic forces on the ocean circulation this interaction has been considered previously under idealized circumstances theoretical results are here simplified and extended toward practical application in large scale ocean circulation models among the suggestions is that coarse resolution models can correct a depth independent part of the velocity field toward a velocity given by z flh where z is the vertical unit vector f is coriolis form l is a length scale o 10 km and h is the total depth absence of this tendency may be implicated in a number of systematic defects that appear in present ocean models

evidence for the early oligocene formation of a proto subtropical convergence from oxygen isotope records of new zealand paleogene brachiopods abstract using the oxygen isotope record in fossil brachiopods we reconstruct late eocene through early miocene paleotemperatures of an eastern new zealand shelf environment our results show a decline in temperature to a low of 6 c in the early oligocene of a magnitude similar to that of open ocean isotopic studies from similar latitudes however the brachiopod derived paleotemperatures are 10 c lower than those inferred from occurrences of warm water fauna and flora e g large foraminifera mangrove and coconut palms which suggest a subtropical 20 23 c climate throughout most of the new zealand oligocene we propose that a proto subtropical convergence pstc with cool subantarctic water flowing along the eastern coast of the south island first developed in the early oligocene the subtropical fauna and flora distribution patterns are consistent with this hypothesis warm water biota e g larger foraminifera and mangrove trees occur primarily on the west and north coasts of new zealand in warm subtropical water characteristic of water north of the pstc similar to the modern subtopical convergence we explain the occurrence of occasional subtropical taxa in early oligocene strata of the east coast of the south island as a result of the north south migration of the pstc or the colonization of relict surtseyan type seamounts in local waters warmed by volcanic eruptions

petrology and palaeoenvironmental significance of glaucony in the eocene succession at whitecliff bay hampshire basin uk following the investigations of odin and others into the distribution of green granules glaucony has been widely assumed to be a reliable indicator of a fully marine open shelf environment with a low sedimentation rate we have investigated the value of glaucony as a palaeoenvironmental indicator through an investigation of the pellets and their distribution and reworking in the predominantly brackish to shallow marine tertiary sediments of the hampshire basin together with a re evaluation of the sedimentology glaucony has apparently formed in situ in all lithofacies from shallow marine to estuarine of the three highest glaucony concentrations all dominated by in situ glaucony two occur within highstand system tracts the third is at a sequence boundary several important surfaces do not have more than a few percent glaucony with very variable proportions of mature and in situ pellets the correlation between glaucony concentration and sequence stratigraphy is most obvious in the london clay and wittering formations where least reworking of pellets has occurred in the barton group there are no major concentrations of glaucony at any of the important stratal surfaces we believe this more random glaucony distribution is due to limited glaucony formation and reworking of older glaucony in these sediments ideal conditions for glaucony formation are interpreted to have been fully marine 10 30 m water depth a warm temperature plus low sedimentation rate with periodic winnowing to concentrate the pellets although most of these conditions for glaucony formation occurred in the selsey formation and barton group a factor or factors mitigated against glauconitization we suggest that this was lowering of the water temperature the london clay and wittering formations were deposited relatively rapidly 50 60 m ma 1 and include intervals of estuarine sedimentation both factors that we believe inhibited glaucony formation glaucony maturity reflects the minimum length of time spent in surface sediments close to the oxic sub oxic interface point count data and chemical data for glaucony indicate widespread reworking and an overall increase in reworking with time possibly due to uplift on the isle of wight monocline the apparently wide range of conditions in which glaucony will form and the frequency with which it is reworked suggest that it is a less useful indicator palaeo environmental indicator than is commonly supposed

residual circulation and tidal stress in the gulf of california 1 results of a three dimensional nonlinear barotropic shelf model are used to study the effect of the m2 tidal stress on the residual current in the gulf of california the tidal stress summarizes the nonlinear interactions and forces the residual circulation it is calculated following the method developed by nihoul and ronday 1975 the vertical structure of the tidal stress reveals clearly the zones where the interaction between tidal currents and the basin geometry is strong the highest values of tidal stress were found over the salsipuedes sill and in the ballenas channel in the central archipelago and in the colorado river delta relatively high values of tidal stress were also found in deeper layers in the southern part the high tidal stress values coincide well with the anomalous cold water patches observed in the archipelago area attributed to tidal mixing the calculated residual currents show a maximum of about 15 cm s 1 in the upper layers in the archipelago area at subsurface layers an anticyclonic circulation is observed divergence patterns in the upper layers suggest that m2 tide residuals contribute to significant upward movements of water on the west side of tiburon island this barotropic process may contribute to the generation of the observed cold patches

environmental factors influencing skeletal grain sediment associations a critical review of miocene examples from the western mediterranean the presence of foramol rhodalgal and bryomol skeletal grain associations in ancient shallow marine limestones is commonly interpreted as evidence for non tropical palaeoclimate despite temperature being only one of several factors influencing skeletal grain associations such interpretations neglect the multitude of factors other than temperature that influence carbonate producing biota these include nutrients water energy water transparency depth of the sea floor salinity oxygen ca2 and co2 concentrations mg ca ratio alkalinity substrate requirements competitive displacement as well as biological and evolutionary trends this uniformitarian approach also disregards the probability that conditions of present day biological systems may not be representative of past conditions of analogous systems here the importance of considering these other factors is illustrated through two examples of carbonate platforms in the western mediterranean these platforms are dominated by foramol rhodalgal and bryomol associations of miocene age in spite of having formed in tropical conditions the platforms discussed are 1 the lower tortonian ramp on menorca balearic islands and 2 the lower middle miocene ramps of the central apennines italy evidence for tropical conditions in the mediterranean during the period of growth of these platforms is provided by species of red algae and larger foraminifera by data from coeval continental basins and by global oxygen isotope data

what is an equable climate abstract the ideal theoretical equable climate has a mean annual temperature of 14 c and a mean annual range of 0 c since 14 c is and has been the average mean temperature of the earth s surface any departure from 14 c and 0 c results in a climate of lower temperateness or equability therefore reference to an equable paleoclimate is meaningless unless quantified by a centrum from which equability is measured climates of low seasonality are not necessarily equable because such conditions occur from the inner wet tropics into glacial border environments freezing often occurs in climates of moderate to high equability equable climates may support taxa from different vegetation zones a relation also evident in the paleobotanical record

paleo oceanographic and tectonic settings of early miocene reefs and associated carbonates of offshore southeast asia the late oligocene to early middle miocene was a period of widespread reef and associated carbonate deposition over a wide latitudinal range in the offshore region of southeast asia a generally rising eustatic sea level during this period allowed the accumulation of thick reefal units an expansion of the coral algal regional facies belt north to japan and south to new zealand occurred during the early miocene as the result of a reduced oceanic latitudinal temperature gradient an episode of enhanced organic carbon burial is reflected in a positive dgr13c excursion from 17 5 to 13 5 ma increasing paleo oceanographic equability may have resulted in reduced ocean circulation with the resultant development of an expanded oxygen minimum zone marine oil prone or anic carbon was deposited in silled anoxic basins both bounded by and within island arc systems a combination of tectonic and paleo oceanographic factors therefore created conditions that favored contemporaneous deposition of organic carbon rich source beds and reef reservoirs during the latest early to early middle miocene paleogeographic and facies reconstructions for an 18 m y interval indicate that deposition occurred in three tectonic settings 1 passive continental margins 2 convergent plate boundaries and 3 obliquely convergent plate boundaries in all these settings the vertical motion histories of fault bounded blocks and of larger tectonic elements within which they are contained directly controlled the geographical distribution of carbonate buildups their scal and morphology duration diagenesis and relationship to siliciclastics

tectonic and climatic significance of a late eocene low relief high level geomorphic surface colorado new paleobotanical data suggest that in the late eocene the erosion surface which capped the front range colorado was 2 2 3 3 km in elevation which is similar to the 2 5 km present elevation of surface remnants this estimated elevation casts doubt on the conventional belief that the low relief geomorphic surface was formed by lateral planation of streams to a base level not much higher than sea level and that the present deeply incised canyons must represent neogene uplift of colorado description of the surface calculations of sediment volume and isostatic balance and fluvial landsculpting models demonstrate that while the high elevation of the erosion surface was due to tectonic forces its smoothness was mostly a result of climatic factors a sediment balance calculated for the front range suggests that from 2 to 4 km of material were eroded by the late eocene consistent with fission track ages this amount of erosion would remove a significant portion of the 7 km of laramide upper crustal thickening isostatic modeling implies that the 2 2 3 3 km elevation was most likely created by lower crustal thickening during the laramide a numerical model of fluvial erosion and deposition suggests a way that a late eocene surface could have formed at this high elevation without incision a humid climate with a preponderance of small storm events will diffusively smooth topography and is a possible mechanism for formation of low relief high level surfaces paleoclimate models suggest a lack of large storm events in the late eocene because of cool sea surface temperatures in the equatorial region return to a drier but stormier climate post eocene could have caused the incision of the surface by young canyons by this interpretation regional erosion surfaces may represent regional climatic rather than tectonic conditions

carbonate cement stratigraphy and timing of diagenesis in a miocene mixed carbonate clastic sequence offshore sabah malaysia constraints from cathodoluminescence geochemistry and isotope studies a mixed carbonate clastic sequence is one of several miocene hydrocarbon bearing reservoirs in the northwestern sabah basin this sequence consists of bioclast rich sandstones interpreted as prograding storm shoal deposits the sequence contains a complex variety of carbonate nodules the sequence has undergone nine stages of cementation that completely occluded pores each stage represents a distinctive cement texture precipitating at specific temperatures and burial conditions the diagenetic evolution began with a syndepositional iron free marine calcite ca1 followed by an early methane derived dolomite do1 bladed calcite ca2 blocky vein filling fe calcites ca3ca4 clay mineral associated dolomite do2 fe dolomite and ankerite do3do4 and late iron rich calcite ca5 each stage of cement has distinctive sr2 mn2 mg2 fe2 ca2 and na contents reflecting changes in the palaeo porefluid systems with time the cements are correlatable over the whole study area precipitation occurred from very early to late stages of diagenesis at near surface to 2 0 km depths with progressive burial and temperature increase oxygen isotope values become strongly negative stage ca4 13c 0 5 pdb 18o 5 7 pdb the cements were precipitated at 20 75 c the source of carbon varies from marine dissolved carbonates to fermentation of organic matter methane meteoric waters and possibly hydrothermal fluids strontium isotope dating of do1 with 13c 32 5 pdb 18o 2 60 pdb and do2 13c 3 0 pdb 18o 2 5 pdb dolomites indicates that these dolomitization events took place at 10 5 ma and 8 9 ma respectively assuming precipitation within a completely open seawater system the do1 dolomite was precipitated from a methane derived brine at the boundary between the serravallian and tortonian stages after major uplift and induced faulting at a sea level lowstand the do2 dolomite was precipitated during intermediate to deep burial diagenesis during smectite illite transformation before hydrocarbon emplacement

bivalve molluscs and cenozoic paleoclimatic events in the northwestern pacific ocean abstract a new method for the calculation of cenozoic paleotemperatures is proposed which is based on the statistical relation between the august ta and annual ty temperature of surface water and the coefficient of thermotropy ct the coefficient presents the percentage ratio of the number of species of bivalve molluscs from temperate and warm water genera to the total number of species in a definite region for the northwestern pacific at 1 1 ct 92 1 the most adequate temperature estimations gave the equations t y 3 836 1 014 ct and t a 10 998 1 009 ct paleotemperatures in the vicinity of western tochilinsky key section and eastern korfa gulf key section kamchatka south sakhalin makarovsky key section and a number of areas of hokkaido and honshu japan have been reconstructed using the proposed procedure an early middle miocene around 16 ma temperature maximum which is of high climatic stratigraphic value has been found to be present in all areas studied and to correspond to the level of the kakertian horizon of western kamchatka the takinoue lower togeshita horizon of hokkaido and the nishikurosawa formation of north honshu the average annual surface water temperatures at that time were 7 1 c up to 9 6 c and 11 5 c respectively in close similarity to the northern areas of the atlantic haq 1982 a four fold advancement of temperate faunistic complexes toward higher latitudes has been observed near western kamchatka specified as the kuluvenian kakertian ilynian early and late etolonian temperature maxima the paleoceanological situation near western kamchatka during these maxima is assumed to be sufficiently close to that presently existing in peter the great bay and in more southerly areas of the sea of japan the basic paleotemperature trends which turn out to be similar for all regions studied and for the main neogene north pacific paleoclimatic events tsuchi 1989 1990 1992 suggest the validity and suitability of the proposed method for the determination of paleotemperatures using the coefficient of thermotropy this is also evidenced by the agreement between the paleotemperature estimates obtained here and the oxygen isotope values

ecology of extant nummulitids and other larger benthic foraminifera applications in palaeoenvironmental analysis abstract larger benthic foraminifera lbf are important contributors to modern and ancient tropical shallow marine sediments over the past 30 years a substantial body of literature has built up on the ecology of modern lbf especially in terms of their environmentally sensitive depth distribution reproductive strategy and morphology and the symbiotic relationship between many larger foraminifera and photosynthetic algae over the same period the extinct genus nummulites which is abundant in eocene sediments of southern europe north africa and the arabian peninsula has increasingly been studied principally because significant volumes of hydrocarbons have been discovered reservoired within nummulitic limestones offshore tunisia and libya the modern ecological studies of lbf provide a powerful tool with which to develop palaeoecological models for fossil nummulites and other symbiont bearing larger foraminifera in the rock record

the palaeogeographic and palaeoenvironmental evolution of a palaeogene mixed carbonate siliciclastic cool water succession in the otway basin southeast australia abstract the otway basin in southeast australia contains a thick sequence of cenozoic shelfal carbonates and siliciclastics that preserve signals relating to the progressive opening of the southern ocean since the paleogene this multidisciplinary study integrates outcrop and subsurface well data from over 100 wells and bores throughout the otway basin with micropalaeontological analyses to constrain the age and palaeoenvironments of the nirranda group late eocene to middle oligocene and the heytesbury group late oligocene to mid miocene these data were used to deduce the late eocene to late oligocene palaeogeographical evolution of the area during the late eocene paralic high energy siliciclastic shoreline to shelf facies dominated the region deepening southwards where mid to outer shelf conditions preserved high energy sandy carbonate facies above the eocene oligocene boundary low energy inner to mid shelfal silt and muddy sand persisted to the north deepening southward to carbonate dominated low energy outer shelf to bathyal marls the change from siliciclastics to carbonates at the eocene oligocene boundary in the otway basin may relate to regional tectonics in the early oligocene high energy inner to outer shelf sand bodies formed in front of marine to inner shelf mudstone facies the sand units are likely to have been influenced by strong local longshore drift and ocean swells that increased as the southern ocean widened to create a larger fetch in the eastern half of the basin later in the early oligocene mixed paralic to inner shelf siliciclastic and carbonate facies were deposited passing to inner to mid shelf marl and mudstone and outer shelf to bathyal marls basinward during this time low to high energy shelfal calcarenite chalk and marl dominated the westerly edge of the basin the contrast in facies from west and east in the basin is inferred to be due to contrasting terrigenous input environmental energy and ramp shelf geometry by late oligocene times the clifton formation the otway basin was dominated by high energy carbonate facies deposited in mid to outer shelf palaeoenvironments the base of the clifton formation preserves a shift in facies and foraminiferal faunas that correlates to the major sea level fall at the early late oligocene boundary this sea level fall is related to a major ice advance in antarctica that corresponds to mid oligocene unconformities globally the switch from low to high energy facies across the early late oligocene boundary in the otway basin suggests that the southern ocean swells experienced by the modern otway coast were well established by middle oligocene time evidence of the strengthening proto antarctic swell regime by early miocene times with final deepening of the drake passage the antarctic circum polar current formed and predominantly inner to outer shelf marls and limestones were deposited in the otway basin

orbitally forced climate change in late mid eocene time at blake nose leg 171b evidence from stable isotopes in foraminifera previous stable oxygen isotopic data from surface dwelling foraminifera indicate that eocene tropical sea surface temperatures ssts were significantly lower than at present here we show that stable isotopic analyses 180 13c of the late mid eocene mixed layer dweller morozovella spinulosa are consistent with in mid eocene mid latitudes ssts close to or slightly lower than modern temperatures at blake nose western north atlantic in contrast isotopic analyses of the benthic foraminiter nuttalides truempyi reveal a gradual fall in mean bottom water temperatures from 8 to 7 c over c 500 ka years these deep intermediate water temperatures are significantly higher than modern ones and are similar to intermediate and bottom water temperatures recorded from earlier in palaeogene and late cretaceous time large shifts arc seen in the 18o and 13c values of the planktonic foraminifers of up to 1 and 2 6 respectively that probably reflect temperature and nutrient fluctuations controlled by regional changes in upwelling intensity and runoff the surface to benthos 18o gradient decreases from 3 pdb to a minimum of c 0 5 pdb over 400 ka which could relate to the intensity of upwelling spectral analysis reveals precessional forcing in the foraminiferal 18o records which shows the direct influence of low latitude insolation on surface water stratification monsoonal wind systems may have forced the upwelling cycles and or freshwater input the benthic foraminifer 18o record also contains the obliquity cycle in addition to the precessional cycles indicating the inheritance of mid and high latitude forcing to subtropical deep waters

evolution of early cenozoic marine temperatures the equator to high southern latitude sea surface and vertical temperature gradients are reconstructed from oxygen isotope values of planktonic and benthic foraminifers for the following five time intervals late paleocene early eocene early middle eocene late eocene and early oligocene paleotemperatures are calculated using standard oxygen isotope temperature equations with adjustments to account for 1 variations in sea water 18o related to changes in global ice volume over time and 2 latitudinal gradients in surface water 18o these reconstructions indicate that sea surface temperatures sst of the southern oceans in the early eocene were as high as 15 c whereas temperatures during the late paleocene and early middle eocene reached maximum levels of 10 12 c by the late eocene and early oligocene high latitude sst had declined to 6 and 4 c respectively for most of the early paleogene low latitude sub tropical temperatures remained constant and well within the range of holocene temperatures 24 ndash 25 c but by the late eocene and early oligocene declined to values in the range of 18 to 22 c the late paleogene apparent decline in tropical temperatures however might be artificial because of dissolution of near surface foraminifera tests which biased sediment assemblages toward deeper dwelling foraminifera moreover according to recent plate reconstructions it appears that the majority of sites upon which the late eocene and early oligocene tropical temperatures were previously established were located either in or near regions likely to have been influenced by upwelling global deepwater temperature on average paralleled southern ocean sst for most of the paleogene we speculate based on the overall timing and character of marine sea surface temperature variation during the paleogene that some combination of both higher levels of greenhouse gases and increased heat transport was responsible for the exceptional high latitude warmth of the early eocene

effect of topographic stress on circulation in the western mediterranean the interaction of eddies with seafloor topography can exert large systematic forces on ocean circulation using a statistical mechanics approach it is possible to obtain a parametrization of this effect the neptune effect for application in large scale ocean circulation models circulation of the western mediterranean has been observed to follow a definite cyclonic path numerical models usually show good qualitative agreement for the large scale circulation but show systematic deficiencies at a subbasin scale we have tested the importance of the neptune effect on the circulation of the western mediterranean sea to perform this test different numerical experiments on western mediterranean circulation were done with and without eddy topography interaction as a first step we analyze the influence of the neptune effect in an ideal western mediterranean with closed straits after these experiments the more realistic case of open straits is studied all the experiments show that the neptune effect may be a significant factor in the basin and subbasin scale circulation in the western mediterranean sea

sensitivity of a large scale ocean model to a parameterization of topographic stress abstract a conventional ocean model was revised to include a tendency for velocities to relax toward a maximum entropy solution that depends on the shape of topography the tendency called topographic stress generates poleward eastern boundary undercurrents strengthens equatorward deep western boundary currents sustains a deep alaska stream and contributes to deep water exchange although the influence of topographic stress is most clearly seen at depth surface expressions include reducing the overshoot of western boundary current separation thereby limiting implied air sea heat and freshwater fluxes near these separations

environmental change in the subtropics during the late middle eocene greenhouse and global implications 1 oxygen isotope records from odp site 1052 blake nose subtropical north atlantic ocean indicate significant short term high amplitude variability up to 1 4 in about 2500 to 4000 years during the late middle eocene 37 9 37 5 ma these variations reflect a combination of changes in sea surface temperature and the oxygen isotope composition of the regional seawater in order to independently evaluate the magnitude of sst changes at blake nose and better understand the nature of environmental change during the late middle eocene we present planktonic foraminiferal mg ca data combined with 18o data from the same samples the calculated mg ca paleotemperatures indicate a decrease in ssts over the study interval from 33 to 28 c at the same time that previously published foraminiferal 18ocalcite values from the same samples also decrease thus the 18ocalcite values must reflect a significant component of seawater 18o change in order to reconcile the opposite paleotemperature trends reflected by both proxies calculated 18oseawater values decreased from 3 at 37 83 ma to 2 at 37 6 ma the combined trends of the sst and 18oseawater cannot be explained by an increase of continental ice over this time interval instead the data favor an overall weakening of the hydrological cycle as global climate transitioned from the greenhouse to icehouse

scleractinian assemblages under sediment input their characteristics and relation to the nutrient input concept abstract in the geological record scleractinian dominated turbid water bioconstructions that accumulated under substantial terrigenous input along with shallow neritic marls rich in well preserved corals are common these occurrences indicate that beyond some threshold the ecologic and taphonomic effects of sedimentation prevail over the effects of nutrification field data and experiments on recent corals show that some taxa cope well with terrigenous turbidity and sedimentation and acclimate to increased heterotrophy colonial corals resilient to sediment input commonly are massive to platy forms of high skeletal plasticity and with large polypars to effectively reject sediment or are branched species providing a very small sedimentation area cleaned by feeble currents or small polyped massive taxa that tolerate intermittent veneering by sediment these corals may comprise siltation assemblages of recent turbid water reefs and level bottoms in siliciclastic environments conversely excess input of even low amounts of dissolved inorganic nutrients into clear waters adversely affects many coral species fossil turbid water bioconstructions twb were situated in inner shelf to shore zone settings or near storm wave base on shelves or ramps did not stack into reef complexes mostly show a cluster to segment fabric are scarce in or devoid of frame pores with marine cement and lacked a high carbonate slope relative to fossil clear water buildups preserved in pure limestone successions fossil twb contain moderately diverse coral assemblages with an increased proportion of sediment resistant forms aside from coral behaviour that is elusive in fossils the sediment resistance of corals was mainly determined by colony shape and polypar size but small polyped sediment tolerant corals became common since the early cretaceous late jurassic to cretaceous turbid water coral assemblages are dominated by plocoid or thamnasterioid forms corresponding cainozoic assemblages consist mainly of cerioid and plocoid taxa in fossil twb bioerosion and encrustation are similar or higher than in contemporaneous clear water buildups under higher sediment input accumulation of discrete twb was quenched and level bottoms of both corals and soft substrate biota formed in the resulting coral marls depending on turbidity sedimentation and substrate stability the coral fauna consists largely of both solitary corals and mainly sediment resistant pseudocolonial colonial forms or is dominated by solitary corals many corals show growth anomalies resulting from partial mortality due to episodic rapid sedimentation and unstable substrate in coral marl environments because of terrigenous input nutrient levels probably were elevated yet macroboring and encrustation are very scarce beyond some threshold of terrigenous sediment input and accumulation the ecologic and taphonomic effects of sedimentation and unstable substrate prevail over the effects of nutrient enrichment during the meso cainozoic evolution of scleractinians increasing photoautotrophy and progressive invasion of oligotrophic environments is in contrast to a late cretaceous to cainozoic increase in the relative number of reefs in marginal marine siliciclastic settings this trend may be explained by second order sea level fall and shrinking of epicontinental carbonate seas and isolated platforms driving corals to more narrow attached shelves and by a wider total trophic range in which distinct coral assemblages can thrive as a result of coral evolution and diversification

evidence for seasonality in early eocene high latitude sea surface temperatures abstract specific challenges still exist in our understanding of past greenhouse climate states whilst climate model simulations using atmospheric co2 concentrations consistent with proxy estimates broadly align with lower latitude proxy temperature estimates they struggle to reproduce the warming implied by proxies at higher latitudes especially in the marine realm this inconsistency has often led to the conclusion that climate models are insufficiently sensitive here we analyse the distribution of photozoan and heterozoan carbonates which provide important constraints for latitudinal sea surface temperature sst gradients to assess data model mismatches for the early eocene climatic optimum the carbonate facies distribution is compared against quantitative geochemical proxy temperature estimates 18 o mg ca clumped isotopes and tex86 and a new hadcm3l climate simulation good correspondence exists between the simulated cold month ssts and photozoan carbonates indicating hadcm3l is effectively reconstructing meridional temperature gradients into mid latitudes whilst there is good agreement between simulated mean annual ssts and geochemical proxy estimates in low latitudes the 18 o mg ca and tex86 estimates instead align with warm month ssts at higher latitudes in light of the carbonate facies evidence and consistency between our simulation and available terrestrial proxy temperature estimates this study supports previous claims that a warm season bias exists in many middle and high latitude sst estimates this helps resolve the discrepancy between climate simulations and marine proxies and shows that climate models and data might be more closely aligned than is appreciated further we demonstrate that simple and widely available proxies can play a fundamental role in contextualising wider paleoclimate uncertainties

thermal evolution of cretaceous tethyan marine waters inferred from oxygen isotope composition of fish tooth enamels 1 the evolution of subtropical 30 35 n upper ocean temperatures through the cretaceous is inferred from the oxygen isotope compositions of 64 fish teeth enamel coming from the western tethyan platform mean 18o values of 22 at the berriasian valanginian boundary decrease with oscillations to 18 5 around the cenomanian turonian boundary and progressively increase to 21 5 by the end of the cretaceous the similarity of this oxygen isotope curve for bioapatites from platform environments with those for foraminifera and bulk carbonates that were deposited in deeper waters and at other paleolatitudes indicates that they record global climatic signals major cooling events at the million year scale can be distinguished 1 at the berriasian valanginian boundary and 2 during the earliest late valanginian a third cooling event is detected during the earliest aptian these events already proposed as icehouse interludes during the lower cretaceous are also recorded at subtropical latitudes a progressive warming is identified from the aptian to the cenomanian turonian interval that corresponds to a thermal optimum and then upper ocean temperatures decreased to the maastrichtian minimum isotopic temperatures range from 15 c to 28 c assuming a 18oseawater of 1 for an ice free world taking more realistic 18oseawater values of 0 for tropical waters during glacial periods within the berriasian valanginian interval and earliest aptian or with above average salinities possibly the maastrichtian temperatures are increased by 4 5 c temperature differences between climatic extremes of the valanginian and cenomanian turonian are estimated to have been 10 c latitudinal thermal gradients for the albian cenomanian turonian and maastrichtian were 0 2 0 3 c latitude and thus weaker than modern oceanic values at about 0 4 c latitude

a comparison of eocene climate model results to quantified paleoclimatic interpretations abstract the integration of climate model results and geologic information offers considerable potential for deriving greater insight into the geologic record in this study climate model results and quantified climatic interpretations derived from proxy data are compared to assess model capabilities and to examine proxy data interpretations atmospheric general circulation model experiments were used to produce a range of possible representative eocene climate states based on current knowledge of the eocene record the climate model experiments incorporate two idealized endmembers of eocene ocean surface temperature distributions characterized by very different latitudinal gradients model results are compared to quantified interpretations of the climate of early eocene north america in an attempt to identify one of the sea surface temperature distributions as more likely to have existed during the eocene the comparisons do not produce a conclusive match between inferred paleoclimatic information and any single case of model results but some interesting insights become apparent model predictions of mean annual temperature and mean annual precipitation compare favorably to interpretations from geologic evidence but there are large differences between model results and interpreted paleoclimatic parameters of minimum surface temperature and mean annual temperature range several possible causes for these differences are discussed

environmental forcings of paleogene southern ocean dinoflagellate biogeography 1 despite warm polar climates and low meridional temperature gradients a number of different high latitude plankton assemblages were to varying extents dominated by endemic species during most of the paleogene to better understand the evolution of paleogene plankton endemism in the high southern latitudes we investigate the spatiotemporal distribution of the fossil remains of dinoflagellates i e organic walled cysts dinocysts and their response to changes in regional sea surface temperature sst we show that paleocene and early eocene 65 50 ma southern ocean dinocyst assemblages were largely cosmopolitan in nature but that a distinct switch from cosmopolitan dominated to endemic dominated assemblages the so called transantarctic flora occurred around the early middle eocene boundary 50 ma the spatial distribution and relative abundance patterns of this transantarctic flora correspond well with surface water circulation patterns as reconstructed through general circulation model experiments throughout the eocene we quantitatively compare dinocyst assemblages with previously published tex86 based sst reconstructions through the early and middle eocene from a key locality in the southwest pacific ocean odp leg 189 site 1172 on the east tasman plateau we conclude that the middle eocene onset of the proliferation of the transantarctic flora is not linearly correlated with regional sst records and that only after the transantarctic flora became fully established later in the middle eocene possibly triggered by large scale changes in surface ocean nutrient availability were abundances of endemic dinocysts modulated by regional sst variations

effect of the topographic stress on the tide and wind induced residual currents in the gulf of california because eddy topography interactions topographic stress are difficult to resolve by numerical models a parameterization has been proposed by holloway 1992 based on the statistical mechanical equilibria tendencies neptune effect a vertically integrated numerical model is used to study the influence of neptune effect upon the tide and wind induced residual circulation of the gulf of california the model is forced at the mouth of the gulf by the tides and at the sea surface by the wind it is found that the parameterization induces mean currents in areas where the residuals produced by tides and winds are small tide and wind induced residuals are large along the mainland coast and from the archipelago to the north where the neptune effect parameterization is less important observations give some support to this parameterization

reevaluation of conflicting eocene tropical temperature estimates molluskan oxygen isotope evidence for warm low latitudes oxygen isotope data from planktonic foraminifera for the warm eocene epoch suggest that tropical sea surface temperatures ssts may have been cooler than at present such data have stimulated various explanations involving e g major changes in ocean heat transport however the planktonic data disagree with terrestrial climate proxies which suggest significantly warmer low latitude temperatures we examined this discrepancy by analyzing seasonal oxygen isotope variations in shallow marine mollusks from the mississippi embayment results indicate that mean annual ssts decreased from 26 27 c in the early eocene to 22 23 c in the oligocene agreeing well with temperatures inferred from terrestrial climate proxies these cooling trends with more significant winter cooling 5 c than summer cooling 3 c are consistent with the predicted consequences of decreasing atmospheric co 2 concentration through the paleogene suggesting that atmospheric co 2 change was a major controlling factor for paleogene climate change that winter sst estimates from the mollusks agree well with the foraminiferal sst estimates suggests that planktonic foraminiferal growth in low latitudes occurred mainly during the cooler winter months throughout the eocene we hypothesize that the unusual hydrography of eocene oceans shifted foraminiferal productivity primarily to winter biasing foraminiferal sst estimates of mean annual ssts