stable organic carbon isotope stratigraphy across oceanic anoxic event 2 of demerara rise western tropical atlantic ocean drilling program odp leg 207 recovered expanded sections of organic carbon rich laminated shales on demerara rise western tropical atlantic high resolution organic carbon isotope and total organic carbon toc records are presented which span the cenomanian turonian boundary interval ctbi including the oceanic anoxic event oae 2 from four sites oriented along a nw striking depth transect these records represent the first high resolution carbon isotope records across oae 2 from the south american margin of the tropical atlantic due to the scarcity of age significant fossils the main purpose of this study was to develop a detailed carbon isotope stratigraphy in order to correlate the ctbi across the depth transect and to tie this to biostratigraphically well defined sections in the western interior basin pueblo usa boreal shelf seas eastbourne england and western tethys oued mellegue tunisia all four sections studied document a 6 increase of 13corg values at the base of the ctbi which is followed by an interval of elevated 13corg values and a subsequent decrease our results supply an important stratigraphic base for subsequent paleoceanographic studies on late cenomanian to early turonian sediments from demerara rise and elsewhere

sea level reconstruction for turonian sediments from tanzania based on integration of sedimentology microfacies geochemistry and micropaleontology abstract despite many advances in sea level research the nature of cyclic eustatic sea level fluctuations during warm periods without or with much reduced polar ice remains enigmatic recently published 18 o records from extremely well preserved turonian microfossils from tanzania do not support the contentious idea of glacio eustatic control of global sea level changes during the warmest period of the cretaceous for the same locality site tdp 31 we reconstruct relative sea level changes based on sequence stratigraphy and integration of sedimentology microfacies geochemistry and micropaleontology four local sequence boundaries sbs tutz1 4 are recognized at the base middle and top of the helvetoglobotruncana helvetica zone and in the late turonian the lowstands are characterized by increased grain size enhanced organic carbon flux faunal assemblage changes and bulk 13 c org and foraminiferal 13 c f and 18 o f minima strong benthic and planktic foraminiferal turnovers above the top middle turonian sb tutz3 probably reflect shallowing from upper slope to outer shelf and or eutrophication the tdp 31 age model is refined through inter regional comparison of planktic foraminiferal ranges and 13 c records from three other south tethyan localities odp holes 762c and 763b exmouth plateau and the guru section tibet this age model enables correlation of the regressive events at a global scale and suggests that within stratigraphic uncertainty the tdp 31 depositional sequences are synchronous with the global turonian third order sequences and are likely driven by eustasy these correlations together with recent astrochronological and radiometric dating indicate a considerably younger age 91 17 0 52 ma for the top h helvetica zone than currently assumed resulting in zonal duration of 2 35 0 52 myr foraminiferal stable isotope data from tdp 31 indicate slight surface and bottom water warming during the regressions and possibly a minor surface water salinity decrease which is inconsistent with glacio eustatic forcing of turonian third order sea level cycles and is more in line with the model of aquifer eustasy

macroevolutionary history of the planktic foraminifera planktic foraminifera are an abundant component of deep sea sediment and are critical to geohistorical research primarily because as a biological and geochemical system they are sensitive to coupled bio hydro lithosphere interactions they are also well sampled and studied throughout their evolutionary history here we combine a synoptic global compilation of planktic foraminifera with a stochastic null model of taxonomic turnover to identify statistically significant increases in macroevolutionary rates there are three taxonomic diversifications and two distinct extinctions in the history of the group the well known cretaceous paleogene extinction is of unprecedented magnitude and abruptness and is linked to rapid environmental perturbations associated with bolide impact the eocene oligocene boundary extinction occurs due to a combination of factors related to a major reorganization of the global climate system changes in ocean stratification seawater chemistry and global climate recur as primary

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

symbiont bleaching in planktic foraminifera during the middle eocene climatic optimum many genera of modern planktic foraminifera are adapted to nutrient poor oligotrophic surface waters by hosting photosynthetic symbionts but it is unknown how they will respond to future changes in ocean temperature and acidity here we show that ca 40 ma some fossil photosymbiont bearing planktic foraminifera were temporarily bleached of their symbionts coincident with transient global warming during the middle eocene climatic optimum meco at ocean drilling program odp sites 748 and 1051 southern ocean and mid latitude north atlantic respectively the typically positive relationship between the size of photosymbiont bearing planktic foraminifer tests and their carbon isotope ratios 13c was temporarily reduced for 100 k y during the peak of the meco at the same time the typically photosymbiont bearing planktic foraminifera acarinina suffered transient reductions in test size and relative abundance indicating ecological stress the coincidence of minimum 18o values and reduction in test size 13c gradients suggests a link between increased sea surface temperatures and bleaching during the meco although changes in ph and nutrient availability may also have played a role our findings show that host photosymbiont interactions are not constant through geological time with implications for both the evolution of trophic strategies in marine plankton and the reliability of geochemical proxy records generated from symbiont bearing planktic foraminifera

oxygen isotopic composition of multiple species of planktonic foraminifera recorders of the modern photic zone temperature gradient abundances of 12 species of planktonic foraminifera collected in two plankton tows from the east tropical atlantic are compared to the chlorophyll content and the temperature of the sea water from which they were collected as expected from previous work in the tropics all dominant tropical species occur in greatest abundance within the photic zone many species occur in greatest abundances in the seasonal thermocline in association with the maximum chlorophyll concentration while a few algal symbiont bearing species occur in greatest abundance in the mixed layer the 18o measurements of planktonic foraminifera shells from core top sediment samples confirm the vertical stratification within the photic zone that is suggested by the relationship between hydrography and abundances found in the plankton tows and found in the statistical study by ravelo et al 1990 comparison between the measured 18o values of planktonic foraminifera with the predicted 18o profiles of the overlying water column at three core locations indicate that species abundances in the sediment record the seasonally integrated conditions of the photic zone and suggests that the abundance of a species in the sediment depends on whether the preferred ecological conditions of that species may be found within the photic zone of the overlying water column sometime during the year species which calcify below the photic zone have only trace relative abundances finally it appears that the total range of 18o values of the dominant species approximates the predicted annual 18o of calcite range in the upper 80 m of the water column

active thrusting and folding along the northern tien shan and late cenozoic rotation of the tarim relative to dzungaria and kazakhstan we have studied geometries and rates of late cenozoic thrust faulting and folding along the northern piedmont of the tien shan mountain belt west of urumqi where the m 8 3 manas earthquake occurred on december 23 1906 the northern range of the tien shan rising above 5000 m overthrusts a flexural foredeep filled with up to 11 000 m of sediment of the dzungarian basement our fieldwork reveals that the active thrust reaches the surface 30 km north of the range front within a 200 km long zone of neogene quaternary anticlines fault scarps are clearest across inset terraces within narrow valleys incised through the anticlines by large rivers flowing down from the range in all the valleys the scarps offset vertically the highest terrace surface by the same amount 10 2 0 7 m inferring an early holocene age 10 2 kyr for this terrace which is continuous with the largest recent fans of the piedmont yields a rate of vertical throw of 1 0 0 3mm yr on the main active thrust at the surface a quantitative morphological analysis of the degradation of terrace edges that are offset by the thrust corroborates such a rate and yields a mass diffusivity of 5 5 2 5 m 2 kyr a rather fresh surface scarp 0 8 0 15 m high that is unlikely to result from shallow earthquakes with 6 m 7 in the last 230 years is visible at the extremities of the main fold zone we associate this scarp with the 1906 manas earthquake and infer that a structure comprising a deep basement ramp under the range gently dipping flats in the foreland and shallow ramps responsible for the formation of the active fault propagation anticlines could have been activated by that earthquake if so the return period of a 1906 type event would be 850 380 years the small size of the scarp for an earthquake of this magnitude suggests that a large fraction of the slip at depth 2 3 is taken up by incremental folding near the surface comparable earthquakes might activate flat detachments and ramp anticlines at a distance from the front of other rising quaternary ranges such as the san gabriel mountains in california or the mont blanc aar massifs in the alps we estimate the finite cenozoic shortening of the folded dzungarian sediments to be of the order of 30 km and the cenozoic shortening rate to have been 3 1 5 mm yr assuming comparable shortening along the tarim piedmont and minor additional active thrusting within the mountain belt we infer the rate of shortening across the tien shan to be at least 6 3 mm yr at the longitude of manas 85 5 e a total shortening of 125 30 km is estimated from crustal thickening assuming local airy isostatic equilibrium under the same assumption serial n s sections imply that cenozoic shortening across the belt increases westwards to 203 50 km at the longitude of kashgar 76 e as reflected by the westward increase of the width of the belt this strain gradient implies a clockwise rotation of tarim relative to dzungaria and kazakhstan of 7 2 5 around a pole located near the eastern extremity of the tien shan west of hami 96 e 43 5 n comparable to that revealed by paleomagnetism between tarim and dzungaria 8 6 8 7 a 6 mm yr rate of shortening at the longitude of manas would imply a rate of rotation of 0 45 m y and would be consistent with a shortening rate of 12 mm yr north of kashgar taking such values to be representative of late cenozoic rates would place the onset of reactivation of the tien shan by the india asia collision in the early to middle miocene 16 22 9 m y in accord with the existence of particularly thick late neogene and quaternary deposits such reactivation would thus have started much later than the collision roughly at the time of the great mid miocene changes in tectonic regimes denudation and sedimentation rates observed in southeast asia the himalayas and the bay of bengal and of the correlative rapid change in seawater sr isotopic ratio 20 to 15 ma like these other changes the rise of the tien shan might be a distant consequence of the end of indochina s escape

subaqueous rhyolite block lavas in the miocene ushikiri formation shimane peninsula sw japan abstract a rhyolite mass of the miocene ushikiri formation in the western part of the shimane peninsula sw japan is a small subaqueous edifice about 600 m high and 4 km wide formed at water depths between 200 and 1000 m it consists mainly of three relatively flat lava flow units 50 300 m in maximum thickness each of which includes lobes and their polyhedral fragments the lava lobes are poorly to well vesiculated glassy to microcrystalline and flow banded and folded compared with mafic pillows they are large having thick quenched and brecciated glassy crusts because of their high viscosity surface tension and thermal conductivity their surfaces disintegrate into polyhedral fragments and grade into massive volcanic breccia the massive volcanic breccia composed of the lobe fragments is poorly sorted and covered with stratified volcanic breccia of the same rock type the rhyolite lavas commonly bifurcate in a manner similar to mafic pillow lavas however they are highly silicic with 1 5 vol phenocrysts and have elongated vesicles and flow folds implying that they were visco plastic during flowage their surface features are similar to those of subaerial block lava with respect to rheological and morphological features they are subaqueous equivalents of block lava

magnitude of late quaternary left lateral displacements along the north edge of tibet images taken by the earth observation satellite spot of the quaternary morphology at 18 sites on the 2000 kilometer long altyn tagh fault at the north edge of tibet demonstrate that it is outstandingly active long term left lateral strike slip offsets of stream channels alluvial terrace edges and glacial moraines along the fault cluster between 100 and 400 meters the high elevation of the sites mostly above 4000 meters in the periglacial zone suggests that most offsets resulted from slip on the fault since the beginning of the holocene these data imply that slip rates are 2 to 3 centimeters per year along much of the fault length and support the hypothesis that the continuing penetration of india into asia forces tibet rapidly toward the east

large scale rhyolite peperites jurassic southern chile development of a jurassic volcano tectonic rift basin in the southern andes created a setting in which thick rhyolitic volcaniclastic sequences accumulated in submarine environments and were penetrated by hypabyssal intrusions during or shortly after deposition in the ultima esperanza district of southern chile extensive masses of peperite were produced when rhyolite magma underwent quenching disruption and commingling with wet unconsolidated sediments during intrusion at shallow levels beneath the sea floor the peperite forms discordant intrusive masses with volumes of up to several cubic kilometers in which large widely spaced coherent rhyolite feeder pods are surrounded by and grade into closely packed and dispersed peperite closely packed peperite consists of tightly fitting clasts separated by sediment filled fractures in dispersed peperite the sediment forms a matrix surrounding large masses of fractured rhyolite and smaller more widely separated rhyolite clasts evidence of in situ quench fragmentation is well preserved on both outcrop and thin section scales thin sections show that clast margins and in some cases entire small clasts underwent cooling contraction granulation releasing shards of quenched rhyolite and fragments of phenocrysts into the adjacent sediment interaction between magma and wet sediment was non explosive and involved fluidization of the host sediments creating space for the intruding magma and causing pervasive injection of highly mobile sediment along thermal contraction cracks in quench fragmented rhyolite the ability of the magma to undergo complex intermixing with large volumes of sediment with widespread preservation of in situ fragmentation textures is interpreted to reflect a relatively low magma viscosity presumably caused by retention of volatiles in the magma at the ambient pressures involved beds of redeposited peperite within the rift basin fill indicate that some of the intrusive peperite masses reached the sea floor undergoing slumping and mass flow the peperites were thus an important local source of coarse grained debris during the evolution of the basin

a 13 000 year climate record from western tibet although the tibetan plateau is important in influencing the atmospheric circulation of the northern hemisphere1 3 there are only a few continuous palaeoclimate records available and these are limited to the plateau s northeastern margin4 6 here we present a 13 000 yr record from sumxi co western tibet constructed from both lake core and shoreline studies which shows that conditions in the early middle holocene were warmer and wetter than at present these results confirm model predictions of an intensified monsoon over the region at 9 000 yr bp owing to an orbitally induced increase in summer insolation7 8 we also find evidence for warm humid pulses at 12 500 and 10 000 yr bp in phase with the steps of the last deglaciation and for a return to cold dry conditions at 11 10 000 yr bp none of which can be explained by orbital variations the existence of the cold episode confirms that the cooling associated with the younger dry as event occurred in continental china6 9 and provides further evidence of the global nature of this event10

fitting degradation of shoreline scarps by a nonlinear diffusion model the diffusion model of degradation of topographic features is a promising means by which vertical offsets on holocene faults might be dated in order to calibrate the method we have examined present day profiles of wave cut shoreline scarps of late pleistocene lakes bonneville and lahontan it may be assumed that these scarps were initially at least as steep as the angle of repose offsets range from 1 to 12 m and present slope angles range from 9 to 29 a parameter called apparent diffusion age defined as half the mean square horizontal extent of the slope function of each profile is plotted as a function of scarp offset the points show a clear trend of apparent age increasing nearly linearly with offset if linear diffusion held and scarps were initially vertical apparent diffusion age would be the same for all the shoreline profiles the increasing trend can only partly be explained by nonvertical initial scarp slope and therefore the rate of transport of material downslope must increase significantly faster than a linear law in the range of slopes spanned by the data the transport law must become linear at small slope to reduce scatter between profiles with varying ambient slopes the transport law adopted for the purpose of dating is k0 1 5s2 where s is local slope the transport coefficient k0 is correlated inversely with fan slope suggesting that there is a dependence on the particle size distribution a table is included that allows easy application of the model to scarps with simple initial shape

oxygen isotopic composition of globorotalia truncatulinoides as a proxy for intermediate depth density 1 we investigate whether the oxygen isotope ratio in the test of globorotalia truncatulinoides can serve as a proxy for intermediate depth 200 500 m density since intermediate depth horizontal density gradients are associated with the vertical shear of upper ocean flows this proxy could provide a tool for reconstructing past ocean circulation the spatial pattern of core top gr truncatulinoides 18o in the atlantic ocean mimics the upper ocean density gradients associated with the major ocean currents to better constrain the controls on the calcification depth s of gr truncatulinoides we attempt to simulate the surface sediment data set using water column temperature and salinity conditions above the core sites we predicted foraminiferal 18o for each core site assuming 1 the calcification occurs at a single depth and 2 the initial calcification is at the surface and the subsequent calcification is at 800 m water depth the predicted 18o best resembles measured 18o of gr truncatulinoides when using 1 a single depth calcification at 350 m or 2 a two depth approximation with 30 surface and 70 800 m calcification this result gives us confidence in the ability of 18o in gr truncatulinoides to proxy lateral density gradients at the intermediate depths associated with upper ocean flow

oxygen and carbon isotope records of upper cretaceous foraminifera from poland vital and microhabitat effects abstract oxygen and carbon isotope data of 11 lower campanian and 11 upper maastrichtian co existing rotaliid foraminiferal taxa from eastern poland are presented pristine preservation of the studied material is documented by studies of cathodoluminescence elemental contents and micro nano structures of foraminiferal tests the variability in 18o and 13c values of the foraminifera is taxon specific and relatively constant within the investigated intervals it results from the combination of vital and microhabitat effects a comparison of the measured isotope signatures with the published data of similar cretaceous or modern taxa have allowed us to find benthic foraminifera which precipitated oxygen and carbon isotopes in near equilibrium with bottom water these are praebulimina sp gyroidinoides globosus pullenia jarvisi and bolivina incrassata for oxygen and cibicidoides voltzianus and cibicides beaumontianus for carbon isotopes the observed differences between 13c values of infaunal and epifaunal foraminiferal taxa are related to the presence of 13cdic dic dissolved inorganic carbon gradient in the sediment column which was much higher in the chelm section although planktic foraminifera studied are characterized by different lifestyles this feature is not mirrored in their oxygen and carbon isotope compositions this is probably due to effects of vital isotope fractionation and minor thermal and carbon isotope gradients in a part of the water column inhabited by these organisms the thermal gradient between near surface and bottom waters is calculated to be ca 4 0 c and ca 7 5 c for the early campanian and the late maastrichtian seas of east european platform respectively based on the comparison of 18o values of selected planktic and benthic foraminifera

genesis of crystal rich volcaniclastic facies in the permian red beds of the central pyrenees ne spain abstract the permo carboniferous volcanism of the central pyrenees developed in subaerial conditions and is mainly represented by the products of explosive eruptions of calc alkaline silicic magmas occasionally associated with calderaforming events the sedimentological record of the permo carboniferous basins of the central pyrenees is characterized by the abundance of crystal rich volcaniclastic deposits reflecting a high crystal content in the erupting magmas 18 40 vol sedimentation during the early permian was dominated by massflows stream floods and braided channels organised in poorly developed alluvial fans at basin margins a wide spectrum of crystal rich deposits can be identified in the permian terrigenous red beds the grouping of these deposits into facies and facies associations allows the recognition of several volcaniclastic marker horizons extending through the central pyrenees these can be used to establish stratigraphical correlations between the different permo carboniferous basins the study of these crystal rich volcaniclastic deposits has revealed that the lower permian crystal rich voleaniclastic deposits of the central pyrenees originated from pyroclastic and reworking processes that sometimes acted simultaneously pyroclastic deposits derived from high intensity explosive magmatic eruptions of rhyodacitic and rhyolitic crystal rich magmas these eruptions generated high eruption columns that occasionally collapsed giving rise to the formation of widespread pyroclastic flows and associated pyroclastic surges the entrance of the eruption columns into the atmosphere had a significant effect on the local weather provoking sporadic storms that led to reworking of pyroclasts by rainfall run off during eruption different crystal concentration processes acted in the eruption columns and in the subsequent pyroclastic flows and overriding ash clouds producing the accumulation of a high volume of crystals in the resulting deposits reworking and redeposition of pyroclastic deposits by fluvial processes further enhanced crystal concentration

warm ocean processes and carbon cycling in the eocene sea surface and subsurface temperatures over large parts of the ocean during the eocene epoch 55 5 33 7 ma exceeded modern values by several degrees which must have affected a number of oceanic processes here we focus on the effect of elevated water column temperatures on the efficiency of the biological pump particularly in relation to carbon and nutrient cycling we use stable isotope values from exceptionally well preserved planktonic foraminiferal calcite from tanzania and mexico to reconstruct vertical carbon isotope gradients in the upper water column exploiting the fact that individual species lived and calcified at different depths the oxygen isotope ratios of different species tests are used to estimate the temperature of calcification which we converted to absolute depths using eocene temperature profiles generated by general circulation models this approach along with potential pitfalls is illustrated using data from modern core top assemblages from the same area our results indicate that during the early and middle eocene carbon isotope gradients were steeper and larger through the upper thermocline than in the modern ocean this is consistent with a shallower average depth of organic matter remineralization and supports previously proposed hypotheses that invoke high metabolic rates in a warm eocene ocean leading to more efficient recycling of organic matter and reduced burial rates of organic carbon

modification of wave cut and faulting controlled landforms from a casual observation that the form of degraded fault scarps resembles the error function this investigation proceeds through an elementary diffusion equation representation of landform evolution to the application of the resulting equations to the modern topography of scarplike landforms the morphologic observations can be analyzed either in the form of one or more cross strike elevation profiles or in the form of the slope offset plot a point plot of maximum scarp slope versus scarp offset working with either or both of these data representations for nine geologic structures which range in age from 3 to 400 ka b p and in offset from 1 to 50 m we apply analytical solutions for the vertical initial value scarp the vertical continuous offset scarp and the finite slope initial value scarp the model calculations are intrinsically ambiguous yielding as the final answer only the product t in the case of the initial value problem or the product a 1 in the case of the repeated faulting problem here t is the age of a single scarp forming event 2a is the vertical slip rate and is the mass diffusivity a single profile across three sea cliffs along the santa cruz california coast is analyzed as three separate initial value problems a reasonably constrained age for the sea cliff standing above the highway 1 platform returns 11 gkg 1 gkg 1 m2 ka with this we can date the two older sea cliffs in fact we do the converse age estimates for these two older sea cliffs based on a uniform rate of uplift both yield the same as for the lower sea cliff we treat a single profile of the raymond fault in pasadena san marino in terms of the repeated faulting problem for it the uplift rate of r crook and others yields 16 gkg the very substantial preexisting offset across the raymond fault must have been buried leveled some 230 ka b p when the modern topography began to form our analysis of the lake bonneville shoreline scarps reveals a dependence of t on 2a suggestive of nonlinear modification processes this appearance is treated with the finite slope initial value scarp model to determine 1 1 gkg for the lake bonneville shoreline scarps the suggestion of m n machette that approximately 100 000 year old meter high scarps are unobservable in weakly consolidated alluvial terranes of the basin and range and rio grande rift valley provinces can be formulated as 1 gkg the coincidence between this inequality and the lake bonneville shoreline is striking and it suggests that the value of 1 gkg may be generally applicable as a good first approximation to the modification of alluvial terranes within the semiarid regions of the western united states the lake bonneville shoreline is the basis for dating four sets of fault scarps in west central utah the drum mountains fault scarps can be modeled in several different circumstances but the most likely interpretation is that these fault scarps formed as the result of a single episode of normal faulting 3 6 to 5 7 ka b p the younger age is associated with quite low initial slope angles 25 the other three sets of fault scarps show no evidence for finite initial value slopes fault scarps along the eastern base of the fish springs range are very young 3 ka b p we estimate the age of fault scarps along the western flank of the oquirrh mountains to be 32 ka b p which meets the weak geologic constraint that they be older than the lake bonneville shoreline fault scarps along the northeastern margin of the sheeprock mountains are even older 53 ka b p an intriguing consequence of our single event analysis of these scarps is that an 11 5 m offset occurred in a single earthquake

a new proxy for cretaceous paleoceanographic and paleoclimatic reconstructions coiling direction changes in the planktonic foraminifera muricohedbergella delrioensis among some modern and recent fossil species of planktonic foraminifera the proportion of left to right coiled shells in a population appears to be temperature dependent the relative abundance of each morphotype reflecting ecological preferences a similar relationship is identified among muricohedbergella delrioensis carsey 1926 at the cenomanian turonian stage boundary in mid latitude sites of the western interior seaway including the pueblo type section the increase of sinistral m delrioensis in the assemblage is related to higher 18 o carb values and decrease in inner porosity which suggests that changes in the coiling direction in this morphospecies could represent a new proxy for constraining sea surface temperature sst variations as surface dwellers muricohedbergellids were not accepted manuscript 2 affected by oceanic anoxic event oae2 and provide a continuous paleoclimatic signal throughout the cenomanian turonian boundary interval furthermore genetic evidence obtained from extant foraminifera indicates that shifts of coiling ratios in planktonic foraminifera species can express the signature of distinct genetic types which are revealed through their opposite coiling directions coiling direction could be a genetic trait implying that cryptic species may occur in the mesozoic

a multiple proxy and model study of cretaceous upper ocean temperatures and atmospheric co2 concentrations foraminiferal d 18 o and mg ca suggests that the ratio of magnesium to calcium in the turonian coniacian ocean may have been lower than in the albian cenomanian ocean perhaps coincident with an ocean 87 sr 86 sr minimum the carbon isotopic compositions of distinct marine algal biomarkers were measured in the same sediment samples the d 13 c values of phytane combined with foraminiferal d 13 c and inferred temperatures were used to estimate atmospheric carbon dioxide concentrations through this interval estimates of atmospheric co2 concentrations range between 600 and 2400 ppmv within the uncertainty in the various proxies there is only a weak overall correspondence between higher lower tropical temperatures and more less atmospheric co2 the genesis climate model underpredicts tropical atlantic temperatures inferred from odp leg 207 foraminiferal d 18 o and mg ca when we specify approximate co2 concentrations estimated from the biomarker isotopes in the same samples possible errors in the temperature and co2 estimates and possible deficiencies in the model are discussed the potential for and effects of substantially higher atmospheric methane during cretaceous anoxic events perhaps derived from high fluxes from the oxygen minimum zone are considered in light of recent work that shows a quadratic relation between increased methane flux and atmospheric ch4 concentrations with 50 ppm ch4 genesis sea surface temperatures approximate the minimum upper ocean temperatures inferred from proxy data when co2 concentrations specified to the model are near those inferred using the phytane d 13 c proxy however atmospheric co2 concentrations of 3500 ppm or more are still required in the model in order to reproduce inferred maximum temperatures

geochemical assessment of the palaeoecology ontogeny morphotypic variability and palaeoceanographic utility of dentoglobigerina venezuelana to better understand the links between the carbon cycle and changes in past climate over tectonic timescales we need new geochemical proxy records of secular change in silicate weathering rates a number of proxies are under development but some of the most promising e g palaeoseawater records of li and nd isotope change can only be employed on such large samples of mono specific foraminifera that application to the deep sea sediment core archive becomes highly problematic dentoglobigerina venezuelana presents a potentially attractive target for circumventing this problem because it is a typically large 355 m diameter abundant and cosmopolitan planktic foraminifer that ranges from the early oligocene to early pliocene yet considerable taxonomic and ecological uncertainties associated with this taxon must first be addressed here we assess the taxonomy palaeoecology and ontogeny of d venezuelana using stable isotope oxygen and carbon and mg ca data measured in tests of late oligocene to early miocene age from ocean drilling program odp site 925 on ceara rise in the western equatorial atlantic to help constrain the depth habitat of d venezuelana relative to other species we report the stable isotope composition of selected planktic foraminifera species within globigerina globigerinoides paragloborotalia and catapsydrax we define three morphotypes of d venezuelana based on the morphology of the final chamber and aperture architecture we determine the trace element and stable isotope composition of each morphotype for different size fractions to test the validity of pooling these morphotypes for the purposes of generating geochemical proxy datasets and to assess any ontogenetic variations in depth habitat our data indicate that d venezuelana maintains a lower thermocline depth habitat at ceara rise between 24 and 21 ma comparing our results to published datasets we conclude that this lower thermocline depth ecology for the oligo miocene is part of an eocene to pliocene evolution of depth habitat from surface to sub thermocline for d venezuelana our size fraction data advocate the absence of photosymbionts in d venezuelana and suggest that juveniles calcify higher in the water column descending into slightly deeper water during the later stages of its life cycle our morphotype data show that 18o and 13c variation between morphotypes is no greater than within morphotype variability this finding will permit future pooling of morphotypes in the generation of the sample hungry palaeoceanographic records

the coniacian santonian sedimentary record in southern tanzania ruvuma basin east africa planktonic foraminiferal evolutionary geochemical and palaeoceanographic patterns a 101 m thick stratigraphically complete late coniacian early santonian ca 89 to 83 ma sedimentary sequence drilled in tanzania tanzania drilling project site 39 allows for the first time examination of the planktonic foraminiferal biostratigraphy and evolution the depositional history and geochemical patterns of the subtropical tropical indian ocean region the sedimentary succession corresponds to an outer shelf to upper slope setting and is dominated by calcareous clayey siltstones and mudstones the occurrences of tethyan marker species enable application of the tropical biozonation including identification of the dicarinella concavata and d asymetrica zones in addition tanzania drilling project site 39 is proposed as reference section for the coniacian santonian boundary in the indian ocean with the boundary placed at the lowest occurrence of globotruncana linneiana in agreement with the gssp stratotype spain the record at tanzania drilling project 39 provides a unique opportunity to document the planktonic foraminiferal evolution in a subtropical marginal sea environment during a key period in their evolutionary history characterized by a major radiation among the deep dwelling taxa combined documentation of lithological and geochemical changes caco3 corg 13ccarb and 18ocarb reveal a setting influenced by continental derived nutrients in the d concavata zone lindi formation with a change to higher carbonate production and reduced surface water primary productivity in the overlying d asymetrica zone nangurukuru formation planktonic foraminiferal assemblage changes mirror the depositional and geochemical trends and indicate a progressive shift from a more eutrophic to a more oligotrophic regime through time at the local scale this palaeoceanographic scenario is consistent with the deepening of coastal tanzania in response to the late cretaceous marine transgression registered in south east tanzania because the tectonic evolution and sea level rise along the east africa continental margin is superimposed on the coniacian campanian global long term sea level high this study hypothesizes that the epicontinental invasion of blue waters may have favoured radiation among deep dwelling taxa this article is protected by copyright all rights reserved

testing the cretaceous greenhouse hypothesis using glassy foraminiferal calcite from the core of the turonian tropics on demerara rise glassy turonian foraminifera preserved in clay rich sediments from the western tropical atlantic yield the warmest equivalent 18o sea surface temperatures ssts yet reported for the entire cretaceous cenozoic we estimate turonian ssts that were at least as warm as conservative mean 30 c to significantly warmer warm mean 33 c than those in the region today however if independent evidence for high middle cretaceous pco2 is reliable and resulted in greater isotopic fractionation between seawater and calcite because of lower sea surface ph our conservative and warm sst estimates would be even higher 32 and 36 c respectively our new tropical ssts help reconcile geologic data with the predictions of general circulation models that incorporate high cretaceous pco2 and lend support to the hypothesis of a cretaceous greenhouse our data also strengthen the case for a turonian age for the cretaceous thermal maximum and highlight a 20 40 m y mismatch between peak cretaceous cenozoic global warmth and peak inferred tectonic co2 production we infer that this mismatch is either an artifact of a hidden turonian pulse in global ocean crust cycling or real evidence of the influence of some other factor on atmospheric co2 and or ssts a hidden pulse in crust cycling would explain the timing of peak cretaceous cenozoic sea level also turonian but other factors are needed to explain high frequency 10 100 k y instability in middle cretaceous ssts reported elsewhere

variation in peperite textures associated with differing host sediment properties peperites formed by mixing of magma and wet sediment are well exposed along punta china baja california mexico where two sills intrude a section of lava flows limestones and volcaniclastic rocks irregular lobes and dikes extend from the sills several meters into host sediments including highly comminuted flow top breccias lithic lapilli tuff breccias and shelly micrites whereas intrusive contacts with lava flows are sharp and planar where one sill intruded both coarse grained volcaniclastic rock and fine grained limestone textural differences between the hosts produced strikingly different styles of peperite blocky masses of the basaltic intrusions up to 1 m in size were dispersed for distances up to 3 m into host lithic lapilli tuff breccias the blocks consequently underwent in situ fragmentation as they were rapidly quenched the high degree of dispersion resulted from steam explosions as the magma enveloped pockets of water in the coarse grained permeable host elutriation of fine grained material from vertical pipes in tuff breccia above the lower sill provides evidence for meter scale fluidization of the host the contact zone between the basaltic magma and the shelly micrite host resembles a mixture of two viscous immiscible fluids fluidal peperite intrusion occurred behind a stable vapor film which entrained lime mud particles and carried them off grain by grain as magma advanced into the host thin section scale elutriation pipes formed microglobular peperite represents a frozen example of a fuel coolant interaction fci between basaltic magma and fluidized micrite host the intimate intermixing of magma and host at the submillimeter level is attributed to fluid instabilities developed along the magma vapor host interface such intimate intermixing of magma and water bearing fragmental debris is commonly a precursory step toward explosive hydrovolcanism

cyclic changes in turonian to coniacian planktic foraminiferal assemblages from the tropical atlantic ocean abstract abundance patterns of planktic and benthic foraminifera from a tropical atlantic drill site ocean drilling program site 1259 demerara rise suriname margin display a pronounced 400 kyr cyclicity uninterrupted throughout our 87 8 92 ma record between two clearly distinguishable assemblages 1 a pelagic foraminifer fauna which represents a deep oxygen minimum zone and 2 another assemblage representing a shallow oxygen minimum zone where the foraminifer fauna is dominated by a higher diversity population of mostly small clavate and biserial species common in epicontinental seas the cyclic changes in the long eccentricity band 400 kyr between these two assemblages are proposed to reflect changes in the mean latitudinal position of the intertropical convergence zone itcz associated fluctuations in precipitation and trade wind strength may have influenced the upwelling regime at demerara rise leading to the observed cyclicity of planktic foraminiferal assemblages the severe turonian to coniacian paleoclimatic and paleoceanographic changes in the atlantic ocean e g gateway opening cooling and glaciation however seem to have no influence on the composition of tropical planktic foraminiferal faunas there is no apparent relationship between foraminifer abundances and a major deflection in the stable isotope record interpreted elsewhere as a sign of the growth and decay of a large polar ice sheet

cretaceous sea surface temperature evolution constraints from tex86 and planktonic foraminiferal oxygen isotopes it is well established that greenhouse conditions prevailed during the cretaceous period 145 66 ma determining the exact nature of the greenhouse gas forcing climatic warming and climate sensitivity remains however an active topic of research quantitative and qualitative geochemical and palaeontological proxies provide valuable observational constraints on cretaceous climate in particular reconstructions of cretaceous sea surface temperatures ssts have been revolutionised firstly by the recognition that clay rich sequences can host exceptionally preserved planktonic foraminifera allowing for reliable oxygen isotope analyses and secondly by the development of the organic palaeothermometer tex86 based on the distribution of marine archaeal membrane lipids here we provide a new compilation and synthesis of available planktonic foraminiferal 18o 18opl and tex86 sst proxy data for almost the entire cretaceous period the compilation uses ssts recalculated from published raw data allowing examination of the sensitivity of each proxy to the calculation method e g choice of calibration and places all data on a common timescale overall the compilation shows many similarities with trends present in individual records of cretaceous climate change for example both sst proxies and benthic foraminiferal 18o records indicate maximum warmth in the cenomanian turonian interval our reconstruction of the evolution of latitudinal temperature gradients low 48 palaeolatitudes reveals temporal changes in the valanginian aptian the low to higher mid latitudinal temperature gradient was weak decreasing from 10 17 c in the valanginian to 3 5 c in the aptian based on tex86 ssts in the cenomanian santonian reconstructed latitudinal temperature contrasts are also small relative to modern 14 c based on low latitude tex86 and 18opl ssts minus higher latitude 18opl ssts compared with 20 c for the modern in the mid campanian to end maastrichtian latitudinal temperature gradients strengthened 19 21 c based on low latitude tex86 and 18opl ssts minus higher latitude 18opl ssts with cooling occurring at low middle and higher palaeolatitude sites implying global surface ocean cooling and or changes in ocean heat transport in the late cretaceous these reconstructed long term trends are resilient regardless of the choice of proxy tex86 or 18opl or calibration this new cretaceous sst synthesis provides an up to date target for modelling studies investigating the mechanics of extreme climates

oxygen isotope ecology of recent planktic foraminifera at the central walvis ridge se atlantic 1 above the walvis ridge in the se atlantic ocean we collected living plantkic foraminifera from the upper water column using depth stratified plantkon tows the oxygen isotope composition 18oc in shells of foraminifera and shell concentration profiles show seasonal and depth habitats of individual species the tow results are compared with the average annual deposition 18oc from sediment traps and the interannual average 18oc of fossil specimens in top sediments at the same site the species globigerinita glutinata best reflects the austral winter spring sea surface temperature sst its 18oc signal in top sediments remains pristine in contrast tow results also show that globigerinoides ruber continues to calcify below the surface mixed layer sml i e down to the deep chlorophyll maximum dcm hence its 18oc signature of exported specimens reflects the sst only when sml incorporates the dcm deep tow and sediment trap results show that both globorotalia truncatulinoides and globorotalia inflata record the temperature between 150 and 350 m depending on the season and the shell size however for all fossil taxa in sediments apart from globigerinita glutinata we observe a positive 18oc shift with respect to the sediment trap and plankton tow values likely related to the interannual flux changes and deep encrustation

subaqueous rhyolitic dome top tuff cones a model based on the devonian bunga beds southeastern australia and a modern analogue the relics of two late devonian subaqueous rhyolitic dome top tuff and pumice cone successions are preserved in the bunga beds outlier of the boyd volcanic complex southeastern australia these cone successions and other rhyolitic volcanics of the bunga beds are associated with turbidite and other deep water massflow sedimentary rocks the two cone successions have a generally similar stratigraphy at the base flow banded variably autobrecciated and quench fragmented rhyolite representing an intrusive to extrusive dome is overlain by rhyolitesediment breccia representing extrusion of the dome through the deep water sediment pile and resedimentation down its flanks in the northern cone succession an overlying succession of bedded pumiceous crystal rich to crystal poor tuffs represents the onset of pyroclastic activity and growth of a tuff cone an overyling debris flow deposit represents degradation of part of the cone the topmost unit a stratified pumice succession is thought to represent another cone building eruptive phase and is separated from the underlying strata by a major slide surface the southern cone succession contains less tuff and abundant pumice and is also terminated by a debris flow deposit indicating cone degradation a modern analogue for the inferred eruptive style and sequence is the 1953 1957 rhyolite eruption that formed the tuluman island lava tuff cone complex in the bismarck sea the eruptions were often cyclical consisting of an initial inferred submarine lava forming stage passing into a pumicecone forming stage in some cases a subaeriallava forming stage and a final stage following the cessation of volcanism during which the cones collapsed gravitationally or were destroyed by wave erosion using observations from both the tuluman island eruptions and the preserved stratigraphies of the devonian tuff cones a dynamic model is proposed for the formation of subaqueous rhyolitic dome top tuff and pumice cones

did photosymbiont bleaching lead to the demise of planktic foraminifer morozovella at the early eocene climatic optimum the symbiont bearing mixed layer planktic foraminiferal genera morozovella and acarinina were among the most important calcifiers of early paleogene tropical subtropical oceans a marked and permanent switch in the abundance of these genera is known to have occurred at low latitude sites at the beginning of the early eocene climatic optimum eeco such that the relative abundance of morozovella permanently and significantly decreased along with a progressive reduction in the number of species concomitantly the genus acarinina almost doubled its abundance and diversified here we examine planktic foraminiferal assemblages and stable isotope compositions of their tests at ocean drilling program site 1051 northwest atlantic to detail the timing of this biotic event to document its details at the species level and to test a potential cause the loss of photosymbionts bleaching we also provide stable isotope measurements of bulk carbonate to refine the stratigraphy at site 1051 and to determine when changes in morozovella species composition and their test size occurred we demonstrate that the switch in morozovella and acarinina abundance occurred rapidly and in coincidence with a negative carbon isotope excursion known as the j event 53 ma which marks the start of the eeco we provide evidence of photosymbiont loss after the j event from a size restricted 13c analysis however such inferred bleaching was transitory and also occurred in the acarininids the geologically rapid switch in planktic foraminiferal genera during the early eocene was a major evolutionary change within marine biota but loss of photosymbionts was not the primary causal mechanism

isotopic evidence for glaciation during the cretaceous supergreenhouse the turonian 93 5 to 89 3 million years ago was one of the warmest periods of the phanerozoic eon with tropical sea surface temperatures over 35 c high amplitude sea level changes and positive 18 o excursions in marine limestones suggest that glaciation events may have punctuated this episode of extreme warmth new 18 o data from the tropical atlantic show synchronous shifts 91 2 million years ago for both the surface and deep ocean that are consistent with an approximately 200 000 year period of glaciation with ice sheets of about half the size of the modern antarctic ice cap even the prevailing supergreenhouse climate was not a barrier to the formation of large ice sheets calling into question the common assumption that the poles were always ice free during past periods of intense global warming

morphological and sedimentological characteristics of the neogene submarine coherent lavas and hyaloclastites in southwest hokkaido japan abstract the neogene formations in southwest hokkaido japan are mostly composed of submarine volcanic products such as submarine coherent lavas and hyaloclastites associated with feeder dikes this paper presents criteria for recognition of submarine effusion products through description of the morphological and sedimentological characteristics of coherent lavas such as pillow lobes sheet flow lava lobes and pseudo pillow lavas and hyaloclastites and feeder dikes and a small amount of associate pyroclastic rocks

evidence for reduced export productivity following the cretaceous paleogene mass extinction the cretaceous paleogene k pg mass extinction was associated with a collapse in the carbon isotopic 13c gradient between planktonic and benthic foraminifera and a decrease in bulk carbonate 13c values these perturbations have been explained by several hypotheses global collapse of primary productivity strangelove ocean greatly reduced export but not primary productivity living ocean little or no reduction in export productivity resilient ocean and geographic heterogeneity in the change of export productivity heterogeneous ocean we tested primary versus export productivity changes in the paleoshelf of new jersey where 13c values and organic carbon accumulation rates can distinguish among different ocean responses on the shelf the k pg boundary is associated with a 2 5 13c decrease in bulk carbonate a 0 8 13c decrease in organic carbon a collapse of the surface to bottom 13c gradient and a drop in organic carbon accumulation rates we interpret an early danian 1 0 planktonic foraminiferal 13c gradient a 0 75 cross shelf benthic foraminiferal 13c gradient and a drop in carbon accumulation rates to reflect the presence of active primary but limited export productivity consistent with the living ocean hypothesis we evaluated interbasinal deep sea benthic foraminiferal 13c gradients between the pacific site 1210 and atlantic site 1262 oceans as a proxy for changes in export productivity the interbasinal 13c gradient was reduced after the mass extinction suggesting a reduction in global export productivity although our data support the living ocean hypothesis evidence from paleoupwelling zones shows significant export productivity indicating spatial heterogeneity in the wake of the k pg mass extinction heterogeneous ocean

tectonic history of a jurassic backarc basin sequence the gran canon formation cedros island mexico based on compositional modes of tuffaceous deposits the jurassic gran canon formation cedros island baja california mexico constitutes an unusually well preserved and exposed example of ancient backarc basin fill petrofacies analysis conducted on tuff aceous sandstone and tuff samples from this formation complement and reinforce prior lithofacies interpretations but with some modification when temporal and spatial trends in petrographic data detrital modes are analyzed and compared to mod els based on data collected from deep sea drilling project and ocean drilling pro gram cores the trends indicate a second heretofore unrecognized phase of backarc rifting basalt lavas interstratified with da citic pyroclastic rocks of the primary vol canic lithofacies previously interpreted to record the eruption of differentiated mag mas at the climax of growth of the gran canon island arc are now as a result of this study considered to be the product of arc extension and rifting our method of modal analysis uniquely combines the quantification of textural at tributes of pyroclastic and epiclastic debris that reflect eruption style and magma com position as well as the effects of reworking and mixing in marine settings this study demonstrates that detailed petrographic analysis is useful in the interpretation of ancient volcaniclastic deposits suspected of having formed in backarc basin settings

warm tropical ocean surface and global anoxia during the mid cretaceous period the middle of the cretaceous period about 120 to 80 myr ago was a time of unusually warm polar temperatures1 repeated reef drowning in the tropics2 and a series of oceanic anoxic events oaes that promoted both the widespread deposition of organic carbon rich marine sediments and high biological turnover3 4 5 6 7 8 the cause of the warm temperatures is unproven but widely attributed to high levels of atmospheric greenhouse gases such as carbon dioxide7 8 9 10 11 12 in contrast there is no consensus on the climatic causes and effects of the oaes with both high biological productivity and ocean stagnation being invoked as the cause of ocean anoxia3 4 5 6 7 8 here we show using stable isotope records from multiple species of well preserved foraminifera that the thermal structure of surface waters in the western tropical atlantic ocean underwent pronounced variability about 100 myr ago with maximum sea surface temperatures 3 5 c warmer than today this variability culminated in a collapse of upper ocean stratification during oae 1d the breistroffer event a globally significant period of organic carbon burial that we show to have fundamental stratigraphically valuable geochemical similarities to the main oaes of the mesozoic era our records are consistent with greenhouse forcing being responsible for the warm temperatures but are inconsistent both with explanations for oaes based on ocean stagnation and with the traditional view reviewed in ref 12 that past warm periods were more stable than today s climate

dating quaternary fault scarps formed in alluvium using morphologic parameters abstract ages of fault scarps as well as those other types of transport limited slopes can be estimated by comparing their morphology with the morphology of scarps of known age age estimates are derived by fitting the scarp profiles to synthetic profiles generated using a diffusion equation or alternatively by classification using a linear discriminant function the usefulness of morphology derived age estimates depends on the relative importance of non age related morphologic variation data from more than 200 scarp profiles demonstrate that morphologic variation not related to scarp age can introduce significant uncertainties into morphology derived age estimates

size related stable isotope changes in late cretaceous planktic foraminifera implications for paleoecology and photosymbiosis abstract the paleoecology of cretaceous planktic foraminifera during the late cenomanian to coniacian period 95 86 ma remains controversial since much of the tropical marine record is preserved as chalk and limestone with uncertain geochemical overprints here we present 13c and 18o data from sieve size fractions of monospecific samples of exceptionally well preserved planktic foraminifera recovered during ocean drilling program leg 207 demerara rise western tropical atlantic our results suggest that all species studied hedbergella delrioensis heterohelix globulosa marginotruncana sinuosa whiteinella baltica grew primarily in surface waters and did not change their depth habitat substantially during their life cycle comparison of size related ontogenetic trends in 13c in cretaceous and modern foraminifera further suggests that detection of dinoflagellate photosymbiosis using 13c is confounded by physiological effects during the early stages of foraminifer growth raising doubts about previous interpretations of photosymbiosis in small foraminifera species we propose that obligate photosymbiosis involving dinoflagellates may not have evolved until the campanian or maastrichtian since our survey of cenomanian coniacian species does not find the 18o and 13c size related trends observed in modern foraminifer dinoflagellate symbioses

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

hyaloclastites peperites and soft sediment deformation textures of a shallow subaqueous miocene rhyolitic dome cryptodome complex palhaza hungary abstract the ne tokaj mountains at palhaza in ne hungary are made up of a complex association of miocene rhyolitic shallow intrusions cryptodomes and endogenous lava domes emplaced into and onto soft wet pelitic sediment in a shallow submarine environment the intrusive extrusive complex shows a range of interaction textures with the host muddy sediment ranging from blocky peperites formed on a 0 1 m scale through to irregular contacts closely resembling globular mega peperites on a 10 m scale the over 200 m thick igneous succession is interpreted to result from the pulsatory growth of shallow cryptodomes through muddy saturated host sediment the intrusions eventually breached the sedimentary cover to build up thick in situ hyaloclastite piles in the shallow subaqueous environment the coherent rhyolitic cryptodome facies is surrounded by intrusive hyaloclastite in the contact zone to the pelitic host sediment in the upper level of the complex rhyolitic dome rock is capped and surrounded by hyaloclastite formed due to quench fragmentation upon contact of the lava surface with sea water

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

active tectonics in southern xinjiang china analysis of terrace riser and normal fault scarp degradation along the hotan qira fault system the northern piedmont of the western kunlun mountains xinjiang china is marked at its easternmost extremity south of the hotan qira oases by a set of normal faults trending n50e for nearly 70 km conspicuous on landsat and spot images these faults follow the southeastern border of a deep flexural basin and may be related to the subsidence of the tarim platform loaded by the western kunlun northward overthrust the hotan qira normal fault system vertically offsets the piedmont slope by 70 m highest fault scarps reach 20 m and often display evidence for recent reactivations about 2 m high successive stream entrenchments in uplifted footwalls have formed inset terraces we have leveled topographic profiles across fault scarps and transverse abandoned terrace risers the state of degradation of each terrace edge has been characterized by a degradation coefficient derived by comparison with analytical erosion models edges of highest abandoned terraces yield a degradation coefficient of 33 4 m 2 profiles of cumulative fault scarps have been analyzed in a similar way using synthetic profiles generated with a simple incremental fault scarp model the analysis shows that 1 rate of fault slip remained essentially constant since the aggradation of the piedmont surface and 2 the occurrence of inset terraces was synchronous at all studied sites suggesting a climate driven terrace formation observation of glacial and periglacial geomorphic features along the northern front of the western kunlun range indicates that the qira glaciofluvial fan emplaced after the last glacial maximum during the retreat of the kunlun glaciers 12 22 ka the age of the most developed inset terrace in uplifted valleys is inferred to be 10 3 ka coeval with humid climate pulses of the last deglaciation the mass diffusivity constant k t being time b p in the hotan region is determined to be 3 3 1 4 m 2 10 3 years consistent with other estimates in similar climatic and geologic environments of western china these results imply a minimum rate for the tarim subsidence of 3 5 2 mm yr if western kunlun overthrusts the tarim platform on a crustal ramp dipping 40 45 to the south it would absorb at least 4 5 3 mm yr of convergence between western tibet and tarim

isotopic evidence for palaeotemperatures and depth stratification of middle cretaceous planktonic foraminifera from the pacific ocean

diverse patterns of ocean export productivity change across the cretaceous paleogene boundary new insights from biogenic barium 1 one of the best studied aspects of the k pg mass extinction is the decline and subsequent recovery of open ocean export productivity e g the flux of organic matter from the surface to deep ocean some export proxies including surface to deep water 13c gradients and carbonate sedimentation rates indicate a global decline in export productivity triggered by the extinction in contrast benthic foraminiferal and other geochemical productivity proxies suggest spatially and temporally heterogeneous k pg boundary effects here we address these conflicting export productivity patterns using new and compiled measurements of biogenic barium unlike a previous synthesis we find that the boundary effect on export productivity and the timing of recovery varied considerably between different oceanic sites the northeast and southwest atlantic southern ocean and indian ocean records saw export production plummet and remain depressed for 350 thousand to 2 million years biogenic barium and other proxies in the central pacific and some upwelling or neritic atlantic sites indicate the opposite with proxies recording either no change or increased export production in the early paleocene our results suggest that widespread declines in surface to deep ocean 13c do not record a global decrease in export productivity rather independent proxies including barium and other geochemical proxies and benthic community structure indicate that some regions were characterized by maintained or rapidly recovered organic flux from the surface ocean to the deep seafloor while other regions had profound reductions in export productivity that persisted long into the paleocene

a shallow marine volcaniclastic facies model an example from sedimentary rocks bounding the subaqueously welded ordovician garth tuff north wales u k abstract volcaniclastic sedimentary rocks bounding the ordovician garth tuff in north wales were deposited in a shallow marine setting adjacent to a magmatic arc the volcaniclastic sedimentary rocks are primarily of angular to euhedral quartz angular euhedral feldspar and volcanic rock fragments these grains are of a pyroclastic origin but have been reworked to various degrees sedimentary rock fragments rounded quartz muscovite biotite iron rich chlorite and various clay minerals occur in lesser amounts the sedimentary rocks can be divided into a proximal offshore to foreshore facies association poffa and an offshore to lower shoreface facies association olsfa the sand dominated poffa exposed near capel curig is characterized by large wave ripples hummocky cross stratification co sets of trough cross beds reactivation surfaces plane beds and graded turbidite layers in suspension deposited mudstone water depths calculated from bedding plane exposure of large wave ripples and determined by the presence of hummocky cross stratification and by facies association vary from a few meters to around 30 m 45 50 m theoretical maximum in a 45 m thick stratigraphic section beneath the tuff eight kilometers to the southeast the garth tuff is bounded by a thick sequence of suspension deposited laminated mudstone with thin graded beds of siltstone and fine grained sandstone this facies association olsfa represents the introduction of material by distal turbidites and by pelagic sedimentation the olsfa was deposited in water depths well below storm wave base possibly in excess of 200 m no evidence of storm waves or surface generated currents occur until over 40 m above the tuff this study documents marine sedimentary rocks deposited in water depths ranging from foreshore to offshore as the bounding facies of the garth tuff it is thus reasonable to conclude that the garth tuff was emplaced and welded in water depths greater than the thickness of the tuff in the area of this study

submarine volcaniclastic rocks in this chapter we are concerned with underwater volcaniclastic eruptions and products as well as pyroclastic flows and debris generated on land and transported by mass flowage into the sea submarine fallout deposits derived from land based eruptions are treated in chapter 7 clastic materials redistributed as mass flows or turbidity currents originating from the rapid build up of tephra and epiclastic volcanic debris along coastal parts of volcanoes are also discussed in various places throughout the text e g chap 13

opening the carbon isotope vital effect black box 2 quantitative model for interpreting foraminiferal carbon isotope data interpretation of carbon isotope records from late quaternary planktonic foraminifers are confounded due to the presence of a significant physiological component in the carbon isotopic signal a quantitative carbon isotope qc model is presented which relates the carbon isotopic composition of a foraminiferal shell to the physiological processes of respiration and symbiont photosynthesis and to the 13c value of seawater co2 the qc model is calibrated with physiological and stable isotopic data from laboratory experiments with living planktonic foraminifers model simulations of chamber and shell 13c values with the symbiont bearing foraminifers orbulina universa and globigerinoides sacculifer suggest 1 variations in symbiont density and photosynthetic rate light level or habitat depth are the primary physiological parameters controlling intraspecific carbon isotopic variability in these species 2 respiration has little effect on the 13c of o universa and 3 each chamber in a multichambered foraminiferal test will have a distinct 13c value depending on its position in the test whorl size 13c value relationships reported for g sacculifer from fossil assemblages can be explained as a function of increasing symbiont density during ontogenetic development

equatorial pacific productivity changes near the eocene oligocene boundary there is general agreement that productivity in high latitudes increased in the late eocene and remained high in the early oligocene evidence for both increased and decreased productivity across the eocene oligocene transition eot in the tropics has been presented usually based on only one paleoproductivity proxy and often in sites with incomplete recovery of the eot itself a complete record of the eocene oligocene transition was obtained at three drill sites in the eastern equatorial pacific ocean odp site 1218 and iodp sites u1333 and u1334 four paleoproductivity proxies that have been examined at these sites together with carbon and oxygen isotope measurements on early oligocene planktonic foraminifera give evidence of ecologic and oceanographic change across this climatically important boundary export productivity dropped sharply in the basal oligocene 33 7 ma and only recovered several hundred thousand years later however overall paleoproductivity in the early oligocene never reached the average levels found in the late eocene and in more modern times changes in the isotopic gradients between deep and shallow living planktonic foraminifera suggest a gradual shoaling of the thermocline through the early oligocene that on average affected accumulation rates of barite benthic foraminifera and opal as well as diatom abundance near 33 5 ma an interval with abundant large diatoms beginning at 33 3 ma suggests an intermediate thermocline depth which was followed by further shoaling a dominance of smaller diatoms and an increase in average primary productivity as estimated from accumulation rates of benthic foraminifera

permian rhyolitic volcanism changing from subaqueous to subaerial in post variscan intra continental sirinia basin sw romania eastern europe abstract the sirinia basin is a well exposed upper carboniferous lower permian intra continental extensional basin containing 1 2 km of permian interbedded terrigeneous sediments and primary volcanic and volcaniclastic rocks of rhyolitic composition these are mostly the products of subaqueous volcanism passing into a subaerial volcanism the intra continental basin lies on the danubian metamorphic units in the south westernmost part of the carpathians sw romania and is n s oriented 18 8 km as result of alpine tectonic evolution and deformation the sirinia basin setting formed a dynamic closed intra continental sedimentary system that experienced a successive subsidence it started with lacustrine sediments and then with large volumes of rhyolitic volcanic and volcaniclastic material dominantly sited in the central part of the basin volcanism included 1 subaqueous extrusion of domes surrounded by hyaloclastite deposits closely associated with secondary sedimentation 2 extrusive and explosive surtseyan type and subaerial eruptions from shallow water to emergent volcanoes on dome cap and associated reworked deposits towards the southern side of the basin and 3 subaerial extrusive domes fluvial erosion and deposition completed the evolution of the emerged marginal part of the basin most of the erupted material of the first and second phase filling the central part of the basin along extensional normal faults was rapidly transported on sides of the basin by turbidite sedimentation debris flows slumping and sliding while turbidites prevail toward the central part of the basin the debris flow sedimentation predominated at the margin of the basin infrequently interrupted by deposition of fallout ash from hydromagmatic explosive eruptions related to the dome cap tuff and pumice cones

distribution and significance of crystalline perlitic and vesicular textures in the ordovician garth tuff wales diverse spherulitic and granular crystalline fabrics perlitic textures and fabrics related to the growth and migration of vesicles occur in the garth tuff a largely welded ordovician ignimbrite defining the distribution of such textures helps to constrain the ignimbrite s cooling and degassing history suites of spherulitic and perlitic textures closely reflect variation in cooling rates seven facies are defined based on the style and intensity of crystallisation 1 a medium to coarsely crystalline equigranular facies 2 an intensely spherulitic facies 3 a sparsely spherulitic facies 4 a pectinate facies 5 a microcrystalline to cryptocrystalline equigranular facies 6 a lithophysal facies and 7 a transitional perlite pectinate facies textural changes from facies 1 to 5 reflect progressively higher cooling rates facies 1 occurs in proximal settings in the ignimbrite s core facies 2 to 5 successively envelop facies 1 with facies 2 becoming the dominant fabric in the ignimbrite s core in medial settings facies 5 is typically developed in the originally glassy perlitic zones at the ignimbrite s welded margins crystallisation under hydrous conditions is reflected by second boiling textures in the sporadically developed lithophysal facies the seventh facies reflects a subtle interplay between cooling hydration and crystallisation which locally prevented perlitic fracturing the distribution of amygdales reflects patterns of volatile migration and entrapment in the lower levels of the ignimbrite amygdales occur in irregular concentrations or rare subvertical pipe like structures pipe like structures attest to fumarolic activity while the ignimbrite was in a rheomorphic state amygdales are widespread and evenly distributed in the upper levels of the ignimbrite however the top of the welding profile is characterised by a thin poorly vesiculated originally vitrophyric horizon that abruptly caps an intense concentration of amygdales ductile and brittle fabrics developed during the upward migration of gas microscopic drag folds occur around some amygdales jigsaw fit to clast rotated breccias originated through both late stage pneumatic fracturing and autobrecciation vaporisation of water at the flow base provided a significant source of volatiles in addition to gas released during cooling and crystallisation secondary alteration has enhanced or modified some fabrics perlitic zones were susceptible to patchy chlorite sericite carbonate diagenetic alteration diagenesis and metamorphism have contributed to the infilling of vesicles

calibration of the c 14 timescale over the past 30 000 years using mass spectrometric u th ages from barbados corals uranium thorium ages obtained by mass spectrometry from corals raised off the island of barbados confirm the high precision of this technique over at least the past 30 000 years comparison of the u th ages with 14c ages obtained on the holocene samples shows that the u th ages are accurate because they accord with the dendrochronological calibration before 9 000 yr bp the 14c ages are systematically younger than the u th ages with a maximum difference of 3 500 yr at 20 000 yrbp the u th technique thus provides a way of calibrating the radiocarbon timescale beyond the range of dendrochronological calibration

late cenozoic right lateral strike slip faulting in southern tibet field observations collected during the sino french himalaya tibet cooperation project 1980 1982 show that right lateral faulting between southern and northern tibet roughly along the chord joining the eastern and western syntaxes of the himalayan arc is a major component of the active tectonics north of the himalayas just north of the well developed rifts of southern tibet we studied three right lateral 100 200 km long strike slip faults forming an en echelon array along that chord evidence for earthquake surface breaks was found on each of these faults for the m 8 beng co or damxung strike slip earthquake of november 18 1951 rupture parameters could be constrained to be 8 2 m and l 90 km offset glacial and postglacial morphological markers 105 years and 104 years b p imply displacement rates of the order of 1 2 cm yr on the three faults the en echelon fault zone appears to extend westward 2000 km across the plateau to the karakorum fault and is thus referred to as the karakorum jiali fault zone kjfz fast rates of slip on it and on faults along the northern rim of tibet appear to contrast with the slower rates of deformations in the interior of the plateau our estimates of slip rates on the strike slip and normal faults of southeastern tibet suggest that eastward extrusion of north tibet between the right lateral kjfz and the left lateral altyn tagh and kun lun faults absorbs at least 30 of the present convergence between india and asia we propose an instantaneous velocity model of the active tectonics of asia compatible with such faulting rates and geometries evidence for tertiary right lateral strike slip movements in southern tibet and around the eastern syntaxis of the himalayas is also found in the structural record offsets of various large scale geological features imply that these movements have been large

fluidization of wet sediments during the emplacement and cooling of various igneous bodies during the emplacement and cooling of igneous bodies fluidization of wet sediment by water vapour may occur by heating or by pressure relief during the opening of fractures momentary fluidization causes sediment reconstitution and local transport continuous fluidization can result in substantial sediment displacement theoretical considerations show that fluidization due to heating is not likely to occur at depths where pressure is much greater than 312 bars studies of the emplacement of sills of andesite ayrshire fluid rhyolite ramsey island and viscous rhyolite moelwyn hills recognize a wide range of phenomena attributable to wet sediment fluidization and in places modify existing interpretations the transgressive bases of the subaqueously welded ash flow tuffs of the capel curig volcanic formation are consistent with emplacement attended by fluidization of the subjacent sediment evidently fluidization is a means by which large volumes of wet sediment can be replaced by igneous material with minimal disturbance of the remaining host also fluidization can result in exceptionally complex contact relationships between sedimentary host and intrusive rocks and can cause fractures formed during cooling to be thoroughly pervaded by sediment fluidization is commonly associated with the formation of peperites

submarine silicic volcanism and associated sedimentary and tectonic processes ramsey island sw wales lower ordovician marine strata formed in an ensialic marginal basin environment record early episodes of distant explosive silicic volcanism and a later volcanotectonic episode which was a precursor to the development of a wide variety of near to source submarine silicic volcanic phenomena the early episodes are represented by well bedded turbiditic tuffs these and older strata at least 770 m thick in normal stratigraphical succession are allochthonous and large scale wet sediment sliding with reworking of strata in cohesive debris flows reflects major disturbance of the sea floor during the emplacement of silicic magmas volcanotectonic uplift along a n s fault exceeded 1 km and led to the emergence and erosion of a rhyolitic volcanic island this was followed closely by submergence and in water depths perhaps of about 500 m there accumulated welded and non welded rhyolitic ash flow tuffs rhyolitic turbiditic tuffs rhyolite lavas and a wide variety of debris flow deposits shallow intrusions of 9low9 viscosity rhyolite were emplaced contemporaneously the more or less simultaneous emplacement of rhyolitic tuff with both 9low9 viscosity and high viscosity rhyolites is attributed to variable water content related perhaps to volatile fluxing in a magma body the location of the near to source extrusive rocks and consanguineous intrusions along the contemporary n s fault is considered to reflect channelling of magma initially along a deep crustal fracture

low latitude sea surface temperatures for the mid cretaceous and the evolution of planktic foraminifera isotopic data from exceptionally well preserved foraminifera show that the subtropical north atlantic had sea surface temperatures ssts between 30 and 31 c during the late albian and early cenomanian these temperatures were warmer than average modern temperatures in the tropical western atlantic and support previous inferences based on diagenetically suspect material of albian tropical ssts of 30 c this finding is consistent with basic theories of oceanic thermal response in the tropics to the high atmospheric carbon dioxide levels during the middle cretaceous greenhouse however our data do not support the concept of a super tethyan region of hypersaline waters in the western north atlantic during late albian and early cenomanian time because seawater salinities substantially higher than modern ones would require significantly higher ssts than those reported here isotopic analysis of mid cretaceous planktic foraminifera shows that planomalina ticinella and biticinella grew in surface waters and provide isotopic proxies for sst whereas deeper growing species include hedbergella rotalipora and praeglobotruncana none of these taxa display isotopic indications of photosymbiosis suggesting that this ecology did not evolve in planktic foraminifera before the late cretaceous contrary to previous hypotheses none of these species increased their depth habitat during their life cycles unlike many extant planktic foraminifera the rotaliporids may have been preferentially susceptible to extinction during oceanic anoxic events because they lived within or below the thermocline for most of their life cycles

faulting associated with large earthquakes and the average rate of deformation in central and eastern asia we determine approximate average rates of deformation in portions of eastern and central asia for the last 80 years these rates are based on estimates of source dimensions average displacements seismic moments and orientations of faults of all large earthquakes m 7 5 and as many other major earthquakes m 7 0 as possible in asia since 1900 a major part of this study is the compilation of these data for separate parts of asia we combine seismic moment tensors to estimate the average rotational strain or deformation tensors for these regions for the last 80 years we estimate that shortening across the tien shan has occurred at 11 mm yr between 5 and 19 mm yr left lateral shear on easterly trending planes in mongolia in northwestern tibet gansu and ningxia and on the xianshuihe fault in western sichuan has been very rapid more than 10 mm yr in each region and apparently as rapid as 40 mm yr in northwestern tibet gansu and ningxia slower rates of a few to 10 mm yr appear to characterize east west extension and conjugate north south shortening of tibet the earthquake history of the himalaya is consistent with rates of underthrusting of more than 10 mm yr but is probably less than the convergence rate of india with eurasia of about 50 mm yr the overall strain field is consistent with a large part of india s penetration into eurasia being absorbed by the extrusion of material out of india s way as a result southeast china moved at about 21 mm yr east southeast with respect to eurasia in the last 80 years with an uncertainty of about a factor of 2 in this estimated rate

paleoenvironmental and paleoceanographic changes across the cenomanian turonian boundary event oceanic anoxic event 2 as indicated by foraminiferal assemblages from the eastern margin of the cretaceous western interior sea abstract two sites near the eastern margin of the cretaceous western interior sea wis were investigated the section at cuba kansas ck is 630 km east of the gssp for the cenomanian turonian boundary at rock canyon colorado rc and the section near sioux city iowa sci is 315 km northeast of the cuba site surprisingly planktic foraminifera dominate all the studied samples despite the relative proximity of the sites to the paleo shoreline and presumed neritic water depths such dominance suggests inhospitable benthic environments and benthic foraminiferal assemblages indicate that seafloor oxygen in the wis decreased eastward therefore the hypothesis of an influx of freshwater into the wis from the western margin forming a fresh water cap that diminished eastward is not supported benthic foraminifera are scarce in most studied samples and species diversity is low in the ck section diversity and abundance increase abruptly in the uppermost cenomanian benthonic zone at the initiation of the 13corg positive excursion marking the onset of oceanic anoxic event oae 2 in the sci section however the benthonic zone is recognized only by presence of nodosaria bighornensis that has a stratigraphic range restricted to this interval other benthic taxa are very rare or absent the favorable conditions of the benthonic zone were short lived while relatively diverse planktic foraminiferal assemblages including keeled species characterize the initial 13c excursion at the ck site dwarfed specimens of heterohelix and hedbergella dominate the assemblages at the more proximal sioux city site furthermore most of the biostratigraphic events recognized in the basin center rc section can be traced into the ck section but not into the sci section including the rotalipora spp and globigerinelloides bentonensis extinctions the heterohelix shift event and the brief benthic recovery event correlation between eastern wis sites shows that the sci section is thicker suggesting a major sediment source to the east this may explain the inhospitable benthic conditions and development of a dead zone seasonal hypoxia analogous to the modern shelf of the northern gulf of mexico proximal to active discharge of the mississippi river development of estuarine circulation in the wis provided the eastern part of the basin with input of calcareous plankton from the south including planktic foraminifera foraminiferal assemblages total organic carbon toc and 13c data of the studied sections suggest a two fold history of greenhorn transgression and oae 2 development the initial phase is a global signal characterized by a positive 13c excursion low toc values and high foraminiferal species diversity the second phase is characterized by overprinting by local conditions in the wis including high fluvial input relatively high toc values and low foraminiferal species diversity these findings suggest that the eastern margin records unique depositional and biotic environments further revealing the dynamic and complex nature of the wis and its sedimentary cycles

maastrichtian north atlantic warming increasing stratification and foraminiferal paleobiology at three timescales 1 analysis of 944 single specimens of three species of late maastrichtian planktonic foraminifera racemiguembelina fructicosa contusotruncana contusa and rugoglobigerina rugosa from 38 samples spanning the last 3 myr of the cretaceous shows consistent isotopic trends through time consistent isotopic differences among taxa and high within sample isotopic variability throughout within sample variability does not change systematically through time for any taxon but average 18o values decrease by 1 5 and average 13c values diverge up section comparing taxa average 18o values are similar within most samples but average 13c values generally decrease from r fructicosa to r rugosa to c contusa in addition the within sample variability of individual 13c measurements is larger for r fructicosa than for either c contusa or r rugosa an observation which is consistent with a photosymbiotic habitat for r fructicosa in terms of maastrichtian paleoceanography the negative 18o trend of 1 5 corresponds to a temperature increase of 6 c and the divergence of 13c values up section suggests an increasingly stratified water column in the western atlantic through the late maastrichtian we suggest that these trends are best explained by increasing import of south atlantic waters into the north atlantic and an intensification of the northern hemisphere polar front

growth of pillow lobes evidence from pillow lavas of hokkaido japan and north island new zealand pillow lavas of cretaceous and neogene age well exposed in hokkaido japan and those of neogene age in north island new zealand provide evidence of their mode of growth some pillow lobes diverge by formation of longitudinal surface spreading cracks the others grow by formation of transverse spreading cracks leaving one or more crusts ending toward the front of the lobes and constrictions therefore it is possible to determine the direction of growth of pillow lobes by tracing the crusts and or constrictions

quenching and hydroclastic disruption of andesitic to rhyolitic intrusions in a submarine island arc sequence northern sierra nevada california devonian submarine island arc deposits of the sierra buttes formation in the northern sierra nevada are penetrated by numerous penecontemporaneous hypabyssal intrusions but related extrusive lavas are absent significant parts of the arc succession are occupied by andesitic to rhyolitic intrusive complexes that record the quenching and disruption of large volumes of magma injected into wet sediments at shallow levels beneath the sea floor extensive masses of intrusive hydroclastic breccia are characterized by in situ fragmentation textures and developed by progressive brittle disintegration of quenched magma pillows dispersed within the breccia formed as a series of interconnected tubes that supplied magma to the growing intrusive masses beds of redeposited hydroclastic breccia indicate that the intrusions locally reached the sea floor to undergo slumping and debris flow large scale steam explosions did not occur during magma wet sediment interaction probably due at least in part to the lithostatic and hydrostatic pressure acting on the intrusions low viscosity rhyolitic magma developed intrusive pillows and in situ hydroclastic breccia in the same fashion as quenched andesitic magma this fluid behavior was favored by retention of volatiles in the rhyolitic magma under relatively deep marine conditions quenched and disrupted hypabyssal complexes of the type described herein may be common elements of the submarine parts of island arcs and other volcanic environments where uprise of magma through thick sequences of wet sediment is impeded due to buoyancy constraints and rapid chilling

upwelling history of the mediterranean sea revealed by stunted growth in the planktic foraminifera orbulina universa early messinian crete greece microfossil and stable isotope data 13c 18o from deep water sediments of late miocene age in the mediterranean region have revealed a stepwise restriction of the mediterranean prior to the messinian salinity crisis which was modulated by a cyclicity responding to orbital precession very little is known with regard to the effects of these changes on shallow water environments of carbonate platforms and ramps this work is based on a geological section on crete greece exposing sediments of early messinian age which documents the coeval response of pelagic and neritic systems to oceanographic changes we discuss a dataset of planktic and benthic foraminifera assemblages in conjunction with size measurements n 6 777 and isotope analyses 18o 13c of the planktic foraminifera orbulina universa with regard to reef growth patterns the planktic foraminifera fauna displays pronounced cyclical abundance changes of warm oligotrophic o universa and cold meso to eu trophic taxa globigerinids neogloboquadrinids this cyclicity corresponds to lithological changes from laminated to homogeneous marls on the precessional frequency band in beds rich in mesotrophic foraminifera o universa is rare and the test is 50 smaller than average growth and size of o universa is affected by various environmental factors including temperature trophic resources illumination and o2 content of ambient water explaining size variability by water temperature implies a change of 11 c over one precessional cycle this estimate is in disagreement with growth patterns and stable isotope data of displaced reef corals porites tarbellastraea documenting almost constant sea surface temperatures but substantial evaporation therefore moderate temperature changes in a context of intense evaporation high salinity and water column destabilization associated with upward mixing of colder water masses with higher nutrient concentrations and low o2 content better fits size variation of o universa from the presence of halimeda bioherms intercalated with the sapropel cycles we infer cyclic photic zone anoxia and at least some sections with sapropel couplets to have formed in the neritic zone we also suggest further testing of stunted growth of o universa as a proxy for enhanced nutrient availability in future palaeoceanographic studies

santonian campanian planktonic foraminifera from tanzania shatsky rise and exmouth plateau species depth ecology and paleoceanographic inferences abstract the santonian campanian interval is of particular interest as it encompasses a cooling trend after the late cretaceous greenhouse maximum warmth of the turonian as well as a possibly related major faunal turnover among planktonic foraminifera the recovery of pristinely preserved planktonic foraminifera from santonian campanian sequences in southeastern tanzania allows examination of faunal changes and documentation of species specific stable isotope 13 c and 18 o signatures these isotopic data are ideal for inferring species paleoecological preferences and for tracing major paleoceanographic changes this study reports the first 18 o and 13 c data generated on glassy specimens of marginotruncana coronata m undulata m marginata and m pseudolinneiana and sigalia carpatica additional results from shatsky rise ocean drilling program leg 198 hole 1210b and exmouth plateau odp leg 122 hole 762c provide geographic control on species habitat preferences and paleoceanographic context isotopic analyses suggest that double keeled species including globotruncana bulloides contusotruncana fornicata c plummerae and probably marginotruncanids inhabited the surface mixed layer whereas the biserial gublerina rajagopalani was a permanent thermocline dweller thus our study confirms recent suggestions that the depth distribution models based on shell morphology and analogies with modern taxa are not applicable at all the examined localities changes in planktonic foraminiferal assemblages are used to define several ecological intervals each one characterized by a distinctive taxonomic composition and or increasing decreasing species diversity combined geochemical and paleontological observations suggest that by the middle late campanian a stratified upper water column developed in tanzania while less stratified and or mesotrophic conditions prevailed at shatsky rise and exmouth plateau

genesis of crystal rich epiclastic rocks from subaqueous silicic lava domes role of thermal shock on quartz phenocrysts abstract deposits in the palaeozoic marine basin of the sarrabus region se sardinia western mediterranean italy show the presence of rhyolitic micropillow lithofacies in the uppermost sector of extrusive subaqueous acid domes these particular volcanic rocks contain quartz phenocrysts affected by curved fractures attributed to thermal shock produced in the magma water interface the flanks of subaqueous domes contain proximal epiclastic sandstones and greywackes characterized by the presence of non mature angular quartz clasts very similar to the occurrences detected in the rhyolitic micropillows therefore a syngenetic referred to acid domes and proximal unreworked character is inferred for these epiclastic deposits a genetic model is proposed to explain the association of lithofacies volcanic and epiclastic in direct relationship with the subaqueous growth and erosion of the domes this process of genesis of texturally unmature epiclastic rocks not related to explosive acid volcanism seems rather new and the conclusions of the paper may be in sharp contrast with some of the criteria previously described for distinguishing between pyroclastic and epiclastic crystal rich rocks

planktonic foraminifera stable isotopes and water column structure disentangling ecological signals differential carbon and oxygen stable isotope 13c and 18o fractionation between planktonic foraminifera test calcite and sea water related to ecology and life stage confound the potential for reconstructing palaeo water column temperature and carbon gradients multi species analysis and strict selection of test sizes are useful methods for identifying these fractionation processes also known as vital effects in fossil taxa however there are a limited number of species with adequate size controlled data sets needed for ground truthing the approach in the modern here we report 13c and 18o measurements made on twelve species of modern planktonic foraminifera across a range of fourteen tightly constrained size windows from a tropical indian ocean core top sample this data set includes more test size windows per species especially from the smallest identifiable test size classes and a wider range of species than previously attempted we use the size controlled 18o calcite trajectories to infer depth habitats and calculate species specific calcification temperatures the temperatures are then used to constrain species specific calcification depths along the modern vertical temperature profile in the western tropical indian ocean by overlaying the per species 13c calcite trajectories on local water column 13cdic profiles we estimate if and when i e at which test sizes the planktonic foraminifera species investigated approach ambient 13cdic values the profiling shows significant size controlled 13c deviation from seawater values in all species at some life growth stage which we attribute to i metabolic fractionation in tests 300 m of mixed layer photosymbiotic taxa for most species there is a size window where these effects appear to be at a minimum and or in balance exceptions are globigerinita glutinata a small 200 m surface living species globigerina bulloides which is highly opportunistic and deep living globorotalia tumida and globorotaloides hexagonus the latter two species being affected by various unexplained 13c vital effects use of our refined guidelines for test size selection should improve the potential for making realistic reconstructions of water column 13cdic in a modern tropical stratified setting and potentially in the distant geological past when there are no living analogues present