tectono magmatic evolution of the west coast of india abstract the west and east coasts of india wci eci have distinct histories of their own the wci originated subsequent to eci which has the imprint of two hotspots marion and reunion evolved through several stages of rifting magmatism and isostatic movements important among them are felsic magmatism associated with doming 93 ma mafic magmatism related to rifting 88 ma origin of the western ghats of india and the east facing scarp of madagascar all the three related to separation of madagascar from india mafic deccan volcanism in the north western parts of india 67 ma rifting of seychelles micro continent and lava cover from the north western parts of india along the carlsberg ridge 62 ma a 27 isostatic subsidence relating to loading of deccan basalts subsidence of bombay offshore region due to reactivation of sonata rift separation of laccadive chagos ridge from the southern part of mascarene plateau because of shifting of the central indian ridge 40 ma buckling of south india and tilting of the peninsula northward due to collision and subduction these events make the wci unique and endowed with a great deal of dynamism

internal waves across the pacific 1 the long range propagation of the semidiurnal internal tide northward from the hawaiian ridge and its susceptibility to parametric subharmonic instability psi at the critical latitude c 28 8 n were examined in spring 2006 with intensive shipboard and moored observations spanning 25 37 n along a tidal beam velocity and shear at c were dominated by intense vertically standing inertially rotating bands of several hundred meters vertical wavelength these occurred in bursts following spring tide contrasting sharply with the downward propagating wind generated features seen at other latitudes these marginally stable layers which have inverse 16 meter richardson number ri16 1 0 7 are interpreted as the inertial waves resulting from psi of the internal tide elevated near inertial energy and parameterized diapycnal diffusivity and reduced asymmetry in upgoing downgoing energy were also observed at and equatorward of c yet simultaneous moored measurements of semidiurnal energy flux and 1 km deep velocity sections measured from the ship indicate that the internal tide propagates at least to 37 n with no detectable energy loss or phase discontinuity at c our observations indicate that psi occurs in the ocean with sufficient intensity to substantially alter the inertial shear field at and equatorward of c but that it does not appreciably disrupt the propagation of the tide at our location

isotopic composition of a large photosymbiotic foraminifer evidence for hypersaline environments across the great australian bight during the late pleistocene abstract analysis of carbon and oxygen isotopic compositions of large benthic foraminifera tests marginopora vertebralis that lived in the great australian bight during the late pleistocene reveal that the tests are enriched by 1 to 3 in both 18o and 13c relative to modern specimens from the same region the intolerance of m vertebralis for cool waters negates lower ocean water temperature as an explanation for such high 18o values the oxygen isotopic compositions are thus interpreted to reflect tests secreted in hypersaline waters of up to 56 ppt salinity concentrated from seawater by evaporation m vertebralis thrives today in waters of similar salinity at shark bay western australia the pleistocene sedimentary assemblage supports an interpretation that environments broadly similar to those in outer modern day shark bay were wide spread across the great australian bight during portions of marine isotope stages 2 3 and 4 the high 13c values of the pleistocene m vertebralis are interpreted to reflect enhanced photosynthetic activity that depletes dissolved carbonate in 12c in such shallow saline settings these hypersaline environments formed during periods of lower sea level when shallow waters

the influence of microhabitats on the carbon isotopic composition of deep sea benthic foraminifera we report 13c and 18o values for rose bengal stained benthic foraminifera from a set of box cores from continental margin environments in the atlantic and pacific oceans these isotopic results are compared with foraminiferal distribution data and pore water 13c profiles to evaluate the importance of environmental microhabitat effects on the carbon isotopic composition of benthic foraminifera the 13c values of infaunal taxa are consistently lower than those of epifaunal taxa suggesting that microhabitat effects on test composition do exist the 13c differences between foraminiferal carbonate and bottom water dissolved inorganic carbon are not correlated with the 18o differences between benthic foraminifera tests and equilibrium calcite but they do correlate with variations in the chemistry of sediment pore waters however interspecific 18o differences as well as 13c differences between species with similar vertical distributions in the sediments indicate that taxon specific vital effects also influence test composition

palaeoenvironmental reconstruction of the sarmatian middle miocene central paratethys based on palaeontological and geochemical analyses of foraminifera ostracods gastropods and rodents paleoenvironmental changes in the upper middle miocene central parathetys were reconstructed by using qualitative and quantitative palaeontological analyses of foraminifera and ostracods coupled with trace elemental mg ca and stable isotope delta 18 o and delta 13 c analyses of their carbonate skeletons and of gastropod sheets mean annual air temperatures were estimated using the oxygen isotope composition of contemporaneous rodent teeth the studied aquatic fossils come from two boreholes in the zsambek basin northern central hungary while the terrestrial ones are from localities in ne hungary and e romania in the studied sarmatian successions three zones could be distinguished based on palaeontological and geochemical results at the badenian sarmatian boundary faunal diversity decreased markedly in the lower zone a transgressive event culminated in a seawater incursion into the semi open basin system of the central paratheys stable bottom water temperature similar to 15 degrees c and variable salinites 20 22 are estimated for the early sarmatian sea the faunal changes notably a strong reduction in biodiversity occuring at the boundary between the lower and the middle zone can be explained by a sea leval highstand with dysoxic conditions a relative sea level fall is documented at the end of this middle zone after a short regressive event a marine connection between the paratethys and mediterranean was established at the beginning of the upper zone this is indicated by an increased microfaunal diversity and the re appearance of marine bademan ostracods and foraminifera which are completely absent from the older samatian series during the upper zone the temperatures and salmities are estimated to have fluctuated from 15 degrees c to 21 degrees c and from 15 parts per thousand to 43 parts per thousand respectively

oxygen and carbon isotopic composition of recent larger and smaller foraminifera from the madang lagoon papua new guinea abstract tests of recent benthic foraminifera from the madang lagoon papua new guinea were analyzed for their oxygen and carbon isotopic composition analyses were performed on scuba collected species from backreef and low oxygenated harbor environments covering a depth range of 0 to 45 m both rotaliid and miliolid symbiont bearing species were found to exhibit increasing 18o with depth while only the rotaliids reveal a comparable trend in their 13c composition the general trend of depletion in the heavier isotopes 13c and 18o appears to be depth and light dependant neither the symbiont type nor the nature of the microhabitat appear to affect the magnitude of 18 o 16 o fractionation in larger foraminifers from this environment the carbon isotope patterns of symbiont bearing species revealed distinct differences between rotaliids and miliolids consistently lower 13c values in rotaliid foraminifers may be related to a higher rate of photosynthetic activity the photosynthetic effect of carbon isotope fractionation may be overprinted by the presence absence of an internal carbon pool and or specific modes of biomineralization which may act as isotopic filters foraminifera collected from low oxygenated organic rich sediments in harbor inlets at madang were found to exhibit particularly low 13c values depletion 13c is suggested to be due to oxidative processes in the surrounding organic rich sediment coupled with preferential incorporation of isotopically lighter 12c

stable isotopes in recent larger foraminifera abstract oxygen and carbon isotope analyses have been made on large benthic foraminifera from bermuda the persian gulf and the philippines the foraminifera belong to the two suborders rotallina and miliolina life spans range between one season to more than two years shells contain information about seasonal temperature ranges and life history stages recorded as fluctuations of oxygen and carbon isotopic values within the shell material almost all specimens studied showed the expected variations in 18o with respect to ambient conditions water isotopic composition and seasonal temperature fluctuations the specimens from bermuda seemed enriched in 18o whereas all specimens from the philippines independent of their taxonomic position seemed to the depleted in 18o with respect to calcita equilibrium specimens from the same species showed about the same level and range of 18o values the miliolid species marginopora vertebralis cyclorbiculina compressa archaias angulatus peneroplis proteus and praesorites orbitolitoides cf monensis commonly show carbon isotope values up to 2 5 lighter than expected equilibrium values independent of sample locality the rotaliid species heterostegina depressa operculina sp and calcarina spengleri show carbon isotope values more than 2 lighter than expected equilibrium values also independent of sample locality all analyzed miliolid species show a tendency with age towards lighter than equilibrium 13c values the analyzed rotaliid species showed the reverse that is shells tend toward increased 13 values with age

geographical distribution of diurnal and semidiurnal parametric subharmonic instability in a global ocean circulation model abstractthe evidence for baroclinic energetics of and geographic distribution of parametric subharmonic instability psi arising from both diurnal and semidiurnal tides in a global ocean general

oxygen and carbon isotopic variation in co existing larger foraminifera from a reef flat at akajima okinawa japan the larger foraminiferal assemblage on the reef flat at akajima ryukyu island arc is comprised of marginopora kudakajimaensis amphisorus hemprichii sorites orbiculus peneroplis planatus heterostegina depressa neorotalia calcar calcarina gaudichaudii baculogypsina sphaerulata and amphistegina lessonii the oxygen and carbon isotopic variations in several specimens of each species living under similar conditions were examined symbiosis had little to no effect on oxygen isotopic composition of the bulk carbonate of the analysed species the isotopic analysis along the ontogenetic stages indicates near equilibrium precipitation of oxygen isotopes in the early life stages and therefore the initial chambers should be microsampled in isotopic analyses for a better estimate of palaeotemperature the order of depletion of 13c parallels the order of accretion of calcium carbonate by the foraminiferal species a poor correlation between 18o and 13c and a large variation in 18o and 13c with size of the shell are the characteristic features of the symbiont bearing benthic foraminifera inhabiting reef flat environments in a deeper water species oxygen isotopic values vary little with size of the shell

the paleocene eocene thermal maximum petm in shallow marine successions of the adriatic carbonate platform sw slovenia the paleocene eocene thermal maximum represents one of the most rapid and extreme warming events in the cenozoic shallow water stratigraphic sections from the adriatic carbonate platform offer a rare opportunity to learn about the nature of paleocene eocene thermal maximum and the effects on shallow water ecosystems we use carbon and oxygen isotope stratigraphy in conjunction with detailed larger benthic foraminiferal biostratigraphy to establish a high resolution paleoclimatic record for the paleocene eocene thermal maximum a prominent negative excursion in 13 c curves of bulk rock 1 3 matrix 4 and foraminifera 6 is interpreted as the carbon isotope excursion during the paleocene eocene thermal maximum the strongly 13 c depleted 13 c record of our shallow marine carbonates compared to open marine records could result from organic matter oxidation suggesting intensified weathering runoff and organic matter flux the ilerdian larger benthic foraminiferal turnover is documented in detail based on high resolution correlation with the carbon isotopic excursion the turnover is described as a two step process with the first step early ilerdian marked by a rapid diversification of small alveolinids and nummulitids with weak adult dimorphism possibly as adaptations to fluctuating paleocene eocene thermal maximum nutrient levels and a second step middle ilerdian characterized by a further specific diversification increase of shell size and well developed adult dimorphism within an evolutionary scheme controlled by long term biological processes we argue that high seawater temperatures could have stimulated the early ilerdian rapid specific diversification together these data help elucidate the effects of global warming and associated feedbacks in shallow water ecosystems and by inference could serve as an assessment analog for future changes

isotope paleontology growth and composition of extant calcareous species abstract isotope paleontology uses the isotopic composition of fossil remains of organisms to make inferences about the physical surroundings of growth of the organisms especially temperature and to obtain clues about life history and modes of growth in calcareous fossils oxygen isotopes are mainly used in the former and carbon isotopes in the latter however since physical surroundings and organism response are intimately associated both types of information are contained in each of the isotopic signals to explore the potential of isotope paleontology and to provide a basis for reconstruction a broad range of extant organisms has been studied taking the pioneering work of epstein and associates as a starting point results are summarized for a representative sampling of these studies with emphasis on work at the laboratories of the authors from the mid seventies to the present the organisms considered are nannoplankton benthic algae planktonic and benthic deep sea foraminifera larger foraminifera sponges corals bryozoans polychaetes arthropods bivalves gastropods cephalopods and vertebrates fish otoliths the survey broadly suggests that regarding oxygen isotopes materials tend to be precipitated close to equilibrium with the surrounding seawater as postulated by urey and that for carbon isotopes disequilibrium is the rule life spans growth rates differential seasonal growth and age of reproductive activity can be extracted under favorable circumstances from individual shells and skeletal parts in detail the interpretation of isotope records of individual shells is quite complicated and simple models will fail to give satisfactory results in many or most cases

on the generation and evolution of nonlinear internal waves in the south china sea the nonhydrostatic regional ocean modeling system is applied to the nonlinear internal waves or solitons that are generated at the luzon ridge in the south china sea the luzon ridge near the batan islands is represented by an idealized ridge with a height of 2 6 km on a flat bottom model runs are performed for various ridge shapes and a symmetric tidal forcings the model is in the mixed tidal lee wave regime the barotropic tide over the ridge generates first mode waves through the internal tide release mechanism westward traveling solitons emerge from these first mode waves through nonlinear steepening in the internal tide release mechanism asymmetric tides with strong eastward currents can generate strong westward solitons the eastward current creates an elevation wave with a higher energy density west of the ridge and as soon as the current slackens the wave is released westward on its backslope strong solitons develop the energy density is further enhanced by nonlinearities such as differences in phase speeds and energy fluxes related to lee waves a modal and harmonic decomposition shows the generation of vertical modes and higher temporal harmonics and indicates significant wave wave interaction e g triads in the mixed tidal lee wave regime more energy is contained in the first mode compared to the higher modes hence linear internal tide beams are less well defined and strong solitons develop

tectonic stress field in the indian subcontinent a map of maximum horizontal compressive stress orientation in the indian subcontinent has been prepared using orientations derived from three different stress indicators borehole elongation breakouts in situ hydraulic fracturing measurements and earthquake focal mechanisms most part of the subcontinent appears to be characterized by a compressional stress regime thrust and strikeslip faulting imposed by plate boundary forces although shmax orientations do not in general show clear correlation with the direction of motion of the indian plate four provinces are recognized on the basis of regionally consistent orientations these are the midcontinent stress province the southern shield the bengal basin and the assam wedge their boundaries have been determined taking into consideration regional tectonics and seismicity central and northern india including the shillong plateau stretching up to the great himalaya pakistan and nepal are included in a broad midcontinent stress province characterized by nne ene oriented shmax the mean orientation of shmax in this province is n23 e subparallel to the direction of compression expected to arise from the net resistive forces at the himalayan collision zone suggesting that it is largely determined by the tectonic collision processes much of southern india mysore plateau and the high grade metamorphic terrain south of the plateau appears to be part of a second stress province characterized by nw oriented shmax these appear close to those of the intraplate stress field prevailing in the central indian ocean a third stress province was recognized in the bengal basin including parts of west bengal tripura manipur and mizoram in northeastern india and most of bangladesh this province extends eastward from the marginal fault in the western margin of the bengal basin to the indo burma subduction zone and is bounded on the north by the e w striking dauki fault shmax within the sedimentary pile of the bengal basin is oriented in e w direction while p axes of earthquakes within the basement and the crust beneath the basin and within the subducted slab of the indian plate beneath the indo burman ranges generally trend north n30 e shmax orientations within the sedimentary pile of the basin are parallel to the local approximately e w direction of the convergence of indian and burmese plates suggesting a casual relation to the resistive forces at the subduction zone in the indo burma region interestingly the stress field in the basement and the crust beneath the bengal basin and in the subducted slab is similar to the one prevailing in the midcontinent stress province assam wedge stress region occupies the northeastern corner of the indian plate including upper assam arunachal pradesh and much of nagaland this region subducts beneath a sharply bent continental collision boundary consisting of the northeastern limb of the himalayan and northern limb of the indo burman fold belts as a result the stress field in this province is depth differentiated and most likely responsible for the absence of consistent shmax directions

a mechanism for local dissipation of internal tides generated at rough topography abstract fine and micro structure observations indicate that turbulent mixing is enhanced within o 1 km above rough topography enhanced mixing is associated with internal wave breaking and in many regions of the ocean has been linked to the breaking and dissipation of internal tides the generation and dissipation of internal tides are explored in this study using a high resolution two dimensional nonhydrostatic numerical model which explicitly resolves the instabilities leading to wave breaking configured in an idealized domain with a realistic multiscale topography and flow characteristics the control simulation chosen to represent the brazil basin region produces a vertical profile of energy dissipation and temporal characteristics of finescale motions that are consistent with observations results suggest that a significant fraction of mixing in the bottom o 1 km of the ocean is sustained by the transfer of energy from the large scale internal tides to smaller scale internal waves by nonlin

on the loss of wind induced near inertial energy to turbulent mixing in the upper ocean wind induced near inertial energy has been believed to be an important source for generating the ocean mixing required to maintain the global meridional overturning circulation in the present study the near inertial energy budget in a realistic 1 12 degrees model of the north atlantic ocean driven by synoptically varying wind forcing is examined the authors find that nearly 70 of the wind induced near inertial energy at the sea surface is lost to turbulent mixing within the top 200 m and hence is not available to generate diapycnal mixing at greater depth assuming this result can be extended to the global ocean it is estimated that the wind induced near inertial energy available for ocean mixing at depth is at most 0 1 tw this confirms a recent suggestion that the role of wind induced near inertial energy in sustaining the global overturning circulation might have been overemphasized

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

frequency shift of near inertial waves in the south china sea abstractdespite sufficient wind forcing internal waves in the south china sea do not exhibit the strong near inertial wave niw peak that is typical in most of the world oceans using data from 1

core top evaluation of benthic foraminiferal isotopic ratios for paleo oceanographic interpretations abstract the benthic foraminifera cibicides wuellerstrofi oridforsalis tener and pyrgo rotalaria from twelve core tops in the norwegian greenland sea and c wuellerstorfi o tener and o umbonatus from four core tops on the rio grande rise were analysed for oxygen and carbon isotopes the norwegian greenland sea data yield statistically discrete means for both 18o and 13c for each species the interregional comparison of our data to published data from the east pacific rise shows that c wuellerstorfi 18o and 13c variations reflect oceanographic differences between sites whereas the data on oridorsalis and pyrgo do not we conclude that c wuellerstorfi is a reliable sensor of bottom water conditions whereas other taxa are of unproven utility supportive biological studies and the lack of positive covariance of 18o to 13c among deep sea benthic taxa lead us to reject models calling for incorporation of metabolic co2 to explain the isotopic variation among deep sea benthic foraminifera we propose a within sediment microhabitat hypothesis to explain the 13c variations among taxa

contemporary and fossil foraminifera from isolation basins in northwest scotland isolation basins are widely used in sea level reconstructions but contemporary analogues have been poorly studied comparatively recent research has identified isolation basins with extended transitional isolation contacts that pose problems in sea level interpretations this paper presents foraminiferal results from 24 contemporary isolation basins combined with data from two isolation basins with extended isolation contacts foraminiferal associations identified from the contemporary basins show a clear relationship with water salinity and sill altitude that supports interpretation of the extended fossil sequences an association dominated by miliammina fusca mf signifies a basin close to final isolation from marine influence increasing marine inundation of basins is signified by a series of associations dominated by the following foraminifera ja jadammina macrescens and m fusca me m fusca and elphidium williamsoni ew e williamsoni he haynesina germanica and e williamsoni nd nonion depressulus these associations can be used to interpret the sedimentary isolation sequences from loch nan corr and rumach vi a pilot study of the stable isotope signature from the two species h germanica and e williamsoni is reported from rumach vi and loch nan corr the results show the potential of stable isotope analysis for environmental reconstruction from isolation basins in particular using 18o for salinity reconstruction

global climatology of near inertial current characteristics from lagrangian observations 1 satellite tracked surface drifter data from 1999 2006 are used to compute global climatology of inertial current characteristics at seasonal scales the global mean near inertial current amplitude at 15m depth is 10 cm s 1 corresponding to mixed layer inertial energies of 300 j m 2 the southern ocean and the western north pacific and atlantic oceans are the most energetic in the near inertial frequency band whereas weaker inertial activity is observed in the subtropical and eastern boundary regions in every ocean basin inertial activity is higher during fall and winter associated with maximum storms activity and deeper mixed layers this study also shows that the mixed layer model developed by r t pollard and r c millard 1970 and forced by the qscat ncep blended wind product is too energetic in the tropics and not enough at high latitudes these discrepancies could question the previous estimates of the wind work to inertial motions based on those simulations

stable oxygen and carbon isotope systematics of exquisitely preserved turonian foraminifera from tanzania understanding isotopic signatures in fossils the interpretation of 18o and 13c analyses of extinct foraminifera is hampered by insufficient knowledge on the contribution of environmental versus biological factors on the measured values we present single species stable isotope data for 18 benthic and 11 planktic foraminiferal species and one calcareous dinoflagellate cyst species from a turonian equatorial record measured on samples collected in se tanzania all microfossils analyzed were excellently preserved and results are compared to isotopic measurements from bulk sediment of the same material remarkably low intra specific variability standard deviations 0 2 across the studied interval and consistently large benthic planktic offsets in 18o 2 8 and 13c 1 5 indicate absence of major long term environmental fluctuations and presence of a well stratified water column stratigraphic isotopic trends show small shifts that are parallel in all studied benthic species with the exception of the 13c record of lenticulina species but within sample inter specific offsets reflect a combination of habitat differences and species specific isotopic disequilibrium fractionation among planktic taxa closely related taxa tend to have similar isotopic values biserial taxa have the lowest 18o values 4 7 but also have relatively low 13c values 1 6 indicating that for the assumption of a surface water habitat additional metabolic effects need to be involved which supports the concept of their opportunistic lifestyle among trochospiral planktics the keeled taxa with compressed chambers have slightly higher 18o 4 2 and lower 13c 2 3 values than taxa with globular chambers 4 4 and 2 4 respectively suggesting differences in habitat or in peak seasonal abundance benthic taxa are subdivided into three isotopically distinct groups with differences reflecting mineralogy life strategy and habitat group i aragonitic taxa epistomina colomia africana group ii calcitic trochospiral taxa with isotopic values seemingly close to equilibrium berthelina berthelini oridorsalis umbonatus lingulogavelinella globosa lingulogavelinella convexa and group iii calcitic taxa with low 18o values and large scatter in 13c values lenticulina four other benthic species show values between groups ii and iii the wealth and consistency of data especially for benthic taxa permit refined conclusions the five studied species of epistomina have a similar isotopic signature and are inferred to form their aragonitic shells with close to equilibrium values small isotopic offsets are seen among species that differ in orientation of the septal foramen but no offsets are seen that seem to co vary with test shape or ornamentation the conical species c africana has 18o values 0 2 lower and 13c values 0 7 lower than species of epistomina the latter offset probably reflects an infaunal habitat for c africana epistomina and group ii species are recommended for paleoenviromental studies mono specific lenticulina 18o values may be used if increased by correction factors of 0 4 to 0 9 but this taxon s low and variable 13c values are interpreted to reflect incorporation of respiratory co2 possibly combined with fast growth rates related to opportunism rather than equilibrium with benthic dissolved inorganic carbon the observed stability of inter specific isotopic offsets suggests disequilibrium isotopic effects are relatively consistent for many taxa in this section and correction factors are proposed that may help to generate more robust upper cretaceous foraminiferal isotopic records however 18o 13c covariance in some benthic inter specific comparisons suggests offsets might vary with changes in temperature food supply or other factors so the appropriateness of the correction factors should be confirmed before being applied at different sites similarities between the observed single species isotopic patterns from this and other studies are used to present a summarizing scheme of influences on the stable isotopic composition in foraminiferal tests by applying the new insights from our study to data from other cretaceous studies we demonstrate that the selection of species for isotopic analysis and understanding these signals are critical to the outcome of paleoceanographic interpretations