abyssal circulation and benthic foraminiferal changes near the paleocene eocene boundary a major change in cenozoic deep sea benthic foraminifera occurred in the atlantic indian and pacific oceans near the paleocene eocene boundary benthic foraminiferal abundance changes began at about 61 5 ma at pacific deep sea drilling project dsdp site 577 a major extinction event followed at 58 57 ma between zones p6a and p6b and a series of first appearances continued until circa 55 5 ma zone p6c these faunal changes occurred during a 6 c warming of pacific bottom water and may indicate that the primary cause was changing temperature other potential causes of the faunal turnover include global changes in surface ocean productivity and changing bottom water source regions comparison of benthic and planktonic 13c records requires no change in the ratio of oceanic phosphorous to carbon during the late paleocene to early eocene which weakens the case for but does not disprove a change in surface ocean productivity at this time interbasinal comparisons of benthic foraminiferal 13c records document that water with high 13c values filled the cape basin during the late paleocene and possibly the early eocene circa 61 57 ma but apparently did not extend into the western basins of the atlantic this pattern suggests a supply of antarctic source water for the cape basin and possible tectonic isolation of the western atlantic basins during at least part of the late paleocene carbon isotope comparisons show that bottom water supply to the cape basin was reduced in the early eocene eolian grain size data suggest that a decrease in zonal wind intensity occurred at the end of the paleocene these late paleocene climatic changes bottom water warming and decreased wind intensity correspond with evidence for an important global tectonic reorganization and extensive subaerial volcanism which may have contributed to climatic warming through increased supply of co2

global iridium anomaly mass extinction and redox change at the devonian carboniferous boundary iridium abundance anomalies have been found on a global scale in the devonian carboniferous d c boundary interval which records one of the largest phanerozoic mass extinction events an event that devastated many groups of living organisms such as plants ammonoids trilobites conodonts fish foraminiferans brachiopods and ostracodes at or very close to the d c boundary there exists a geographically widespread black shale interval and ir abundances reach anomalous maxima of 0 148 ppb montagne noire france 0 138 ppb alberta canada 0 140 ppb carnic alps austria 0 156 ppb guangxi china 0 258 ppb guizhou china and 0 250 ppb oklahoma the discovery of global d c ir anomalies argues for an impact extinction model however nonchondritic ratios of ir to other important elements and a lack of physical evidence shocked quartz microtektites do not support such a scenario the fact that all ir abundance maxima are at sharp redox boundaries in these sections leads us to conclude that the ir anomalies likely resulted from a sudden change in paleo redox conditions during deposition and or early diagenesis 36 refs 2 figs 1 tab

the cretaceous tertiary boundary stratotype section at el kef tunisia how catastrophic was the mass extinction abstract the cretaceous tertiary k t boundary stratotype section at el kef tunisia represents the most complete and expanded sedimentary record across this important mass extinction horizon presently known high resolution analysis of planktic foraminifera in two outcrops el kef i stratotype and el kef ii along with comparisons between planktic and benthic foraminifera calcareous nannofossils ostracods pollen and spores and dinoflagellates indicate that major changes across the k t boundary are registered only in benthic and planktic foraminifera and calcareous nannofossils biotic changes in benthic foraminifera are unique to el kef and similarly shallow continental shelf sections and appear to be the result of a sea level regression in the latest maastrichtian followed by a sea level rise across the k t boundary that was accompanied by expansion of the local oxygen minimum zone omz biotic changes in planktic foraminifera appear partly related to these conditions also but in general reflect more global oceanographic changes for instance species extinctions are gradual and selective as observed in k t sections worldwide rather than random and abrupt although there is a 69 decline in species richness between 25 cm below and 10 cm above the k t boundary only rare species disappeared their combined relative abundance constitute less than 20 of the total population about 52 of these extinct taxa 8 of the population are large ornate morphologically complex tropical subtropical forms that lived at or below the thermocline no planktic foraminifera from this depth range survived the k t boundary event all survivor taxa were surface dwellers living within the photic zone their relative abundance 80 dominates both cretaceous and early tertiary populations these data indicate that the k t biotic record in the shallow continental shelf section at el kef was significantly influenced by local conditions which combined with the latest maastrichtian sea level regression and subsequent sea level rise resulted in shallowing of the local omz relative to the sea surface shallowing of the local omz lead to the selective disappearance of benthic faunas and may have adversely affected the surviving photic zone dwellers the selective nature of species extinctions however appear to be related partly to long term global oceanographic changes which were accelerated at the k t boundary possibly by a bolide impact

pt group metal anomalies in the lower mississippian of southern oklahoma four iridium pt group elements abundance anomalies have been found within a stratigraphic span of 3 m in the lower mississippian of oklahoma in ascending order the first anomalies occur at the top of the woodford shale ir 0 25 ppb pt 48 ppb os 7 5 ppb and au 18 ppb the anomalies occur just below a redox boundary and we suspect that the enriched elements were precipitated from sea water that contacted the organic and sulfide rick black shale two more anomalies occur in the welden limestone the lower one weak and the upper one strong ir 0 42 ppb pt 50 ppb os 0 075 ppb and au 0 14 ppb the excess ir and pt also co as and ni might have been enriched from sea water by bacteria at these two horizons a 70 cm thick interval of excess heavy siderophiles occurs in the overlying caney shale the interval contains the following peak concentrations ir 0 56 ppb pt 150 ppb os 0 51 ppb co 725 ppm and ni 1450 ppm these elements vary in proportion to the al clay content and we suspect that they were carried in with detrital material from erosion of ultramafic source rocks we found no evidence of microspherules or shocked mineral grains in any of these anomaly zones

a tree ring based precipitation reconstruction for the mohe region in the northern greater higgnan mountains china since ad 1724 abstract august july precipitation has been reconstructed back to ad 1724 for the mohe region in the northern greater higgnan mountains china using pinus sylvestris var mongolica tree ring width the reconstruction explains 39 of the variance in the precipitation observed from ad 1960 2008 some droughts noted in historical documents are precisely captured in our reconstruction wet periods occurred during the periods of ad 1734 1785 ad 1805 1830 ad 1863 1880 ad 1922 1961 and ad 1983 1998 while the periods of ad 1786 1804 ad 1831 1862 ad 1881 1921 and ad 1962 1982 were relatively dry power spectral and wavelet analyses demonstrated the existence of significant 24 yr 12 yr and 2 yr cycles of variability the results of the spatial correlations suggest that our reconstruction contains climatic signals for the southern stanovoy range and the northern greater higgnan mountains the positive correlations between the new reconstructed precipitation series and two precipitation reconstructions indicate that our precipitation reconstruction captures broad scale regional climatic variations a comparison between the weakening tendency of summer monsoon and the dry period of our reconstruction reveals that the annual precipitation in the mohe region is partly influenced by the east asian summer monsoon

paleoceanography a review for the gsa centennial the central problem of paleoceanography is the history of the circulation of the ocean although speculation about ancient oceanic circulation goes back to the past century the field of paleoceanography was founded in the 1950s as oxygen isotope studies suggested that oceanic deep waters were warmer in the past than they are today extensive coring of deep sea sediments by numerous expeditions after world war ii was followed by the ocean drilling programs providing a rich data base paleoceanographic interpretations have tried to explain the most obvious changes in sea floor sediments and their contained fossils changing paleotemperatures indicated by oxygen isotopes fluctuations in the calcium carbonate compensation depth accumulations of organic carbon rich sediments and the unexpected abundance of hiatuses in a setting which had been thought to be the ultimate sedimentary sink the result has been the intriguing discovery that although the positions and circulation of the major surface gyres is generally stable the deep circulation of the ocean may reverse on a variety of time scales it has been suggested that formation of north atlantic deep water which causes the uneven distribution of nutrients alkalinity and oxygen in the deep sea today may have been replaced by formation of north pacific deep water during the last deglaciation reversing the concentration gradients of nutrients alkalinity and oxygen on a longer time scale the present general circulation which is dominated by production of oxygen rich cold deep water in the subpolar regions today may have replaced a pre oligocene general circulation in which warm saline oxygen poor deep waters were formed in warm seas in the arid zones paleoceanography is still in its infancy many new clues to the history of the ocean are being discovered and many new ideas about conditions in the past are being developed the beginning of the next century should see continuing rapid growth and maturation in this exciting new field

metal accumulation rates in northwest atlantic pelagic sediments measurements of 230th 87sr86sr and twenty four metals were made on cores from the nares abyssal plain the sediment is characterized by slowly accumulating 0 3 0 7 g cm2 103 yr pelagic red clays and rapidly deposited grey clays transported by turbidity currents despite their colour differences and the enrichment of mn fe cu co ni zn v and to a lesser degree the rare earths in the red clays sr isotope evidence demonstrates that the clays have the same terrigenous origin the excesses of metals in the red clays have been attributed to metal removal from the water column and a comparison with the grey clays has enabled the authigenic fluxes of metals to be estimated the fluxes obtained are in the ranges 20 50 mol cm2 103 yr for mn and fe 0 1 0 4 mol cm2 103 yr for cu co ni zn v sr and ce 10 20 nmol cm2 103 yr for la and nd and 0 5 3 nmol cm2 103 yr for sm eu gd dy er and yb authigenic fluxes of y nb cr zr rb u and th were not resolvable fluxes appear to be near constant on the plain but comparison with other areas shows that they are quite variable both between and within ocean basins the chief factor controlling authigenic fluxes is the geochemical abundances of the elements but fractionation within both the transition element and rare earth series can be recognized from inter element comparisons and from differences in fluxes between atlantic and pacific red clays corresponding to the oceanic reactivities of the elements

demise of a devonian carboniferous carbonate ramp by eutrophication the occurrence of organic rich mudrocks overlying carbonate deposits in the rock record has typically been ascribed to changes in relative sea level we propose alternatively that progressive eutrophication of the euphotic zone caused the ecological demise of a late devonian marine carbonate ramp system in alberta and its subsequent burial in organic rich mudrocks similar lithologic transitions elsewhere in the stratigraphic record may also reflect eutrophication rather than major shifts in sea level the transition from upper devonian carbonates to devonian carboniferous black mudrocks in alberta is characterized by a gradual decrease in net carbonate accumulation as indicated by 1 an upward increase in mud phosphate and glauconite 2 the existence of firmground surfaces and 3 a change from a dominantly phototrophic to heterotrophic benthic assemblage an upward trend to lower bulk 13 c organic and 15 n values reflects the eutrophication of surface waters by upwelling of nutrient laden deeper waters resultant primary production propelled higher organic matter flux to the sea floor caused the demise of carbonate producing benthic organisms and promoted burial of carbonate deposits by organic rich mudrocks

oceanic anoxia at the precambrian cambrian boundary the precambrian cambrian pc c boundary separates fossils representing two discrete evolutionary phases the neoproterozoic soft bodied ediacarian biotas and cambrian small shelly faunas the biological discontinuity is suspected to have been a result of mass extinction however recent discoveries of the ediacarian biotas in cambrian sediments have led to an understanding that the faunal change was gradual through the pc c transition th u ratios which are high in oxidizing conditions and low in reducing conditions show a considerable positive correlation with 13c values at all studied sites of the pc c boundary this correlation indicates that reported 13c variation across the pc c boundary from numerous localities corresponds to redox variation in the depositional environment the negative 13c anomaly that occurs worldwide at the pc c boundary therefore corresponds to the widespread development of an oxygen deficient shallow marine environment this finding suggests that widespread oceanic oxygen deficiency which has been interpreted to reflect phanerozoic mass extinction events also occurred immediately before the cambrian explosion

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

late palaeozoic environmental changes an introduction the idea of this volume arose from our proposal to the palaeoclimatic session held at the european geosciences union general assembly 2011 conference in vienna austria although the original scope was broader the included contributions focus on palaeoenvironmental changes during the late palaeozoic late palaeozoic history is especially important in that it records an increase of tectonics diastrophism frequent sea level fluctuations and climatic changes all finally leading to the most geocratic time of earth s history with the formation of the supercontinent pangaea this volume includes a number of articles that discuss the fossil record around the late palaeozoic ice age and its decline during the carboniferous with its unusual plant proliferation soon after when the hottest and driest period in earth s history in the permian caused the development of huge sand seas on the land finally a biotic event the largest mass extinction in earth history at the permian triassic transition ends the palaeozoic world this volume addresses two key issues the palaeoclimate and depositional cycles both of which have a strong impact on the record of palaeoenvironmental changes and the understanding of environmental perturbations the vigorous current debate on the future climate of the globe inevitably increases our interest in past climates from a geological perspective climatic perturbations occurred many times before humans were on the planet climate varies on several timescales depends on many high order factors including tectonic uplift and the orbital wandering of the earth and as a result it changes through time consequently palaeoclimatic reconstructions are growing in their importance as they enable us to use the past as a key to the future the earth s system experiences various cycles of very different origin scale frequency amplitude phase and basic level from a geological perspective the cyclicity appears unidirectional like brownian motion however in the past the complex interaction of these cycles has led to catastrophic changes in earth s systems such as those during the late palaeozoic when palaeoclimatic and geotectonic cycles coincided these cycles are also influencing our lives and will do so in our future so their impact needs to be understood the geological archives record both the climatic and cyclic phenomena on local to regional scales including in the late palaeozoic as documented in this volume understanding these records will improve our predictions about climate phenomena in the future they also show that the present climatic perturbations are insignificant from a geological point of view changes in the late palaeozoic earth system are illustrated in this volume by case studies of fossil records from north and south america east and south asia south africa and australia and as regional reviews section one the methods include palaeoenvironmental analysis including palaeobiological sedimentological stratigraphic sequence stratigraphy palaeomagnetic and geochemical methods they describe various environmental settings from palaeodeserts through marine associated giant salt pans to shallow to deep marine records the articles report new data from less known study areas provide up to date data ordering and expand our knowledge of the evolution of marine and terrestrial environments climatic changes and biotic events in late palaeozoic time this special publication is divided into five chapters the first comprising articles focused on the broad descriptive character of late carboniferous to early triassic palaeoclimatic changes and stratigraphy with the latest part of this period in europe i e zechstein subsequent articles include more detailed studies of the geological periods grouped into the latest devonian to early carboniferous section two late carboniferous to early permian section three middle to late permian section four and finally the permian triassic transition section five a brief synopsis of individual papers is given below wopfner 2012 reviews westphalian early triassic palaeoclimatic conditions between samfrau comprising the southern margins of south america and south africa extending via antarctica

abrupt deep sea warming palaeoceanographic changes and benthic extinctions at the end of the palaeocene a remarkable oxygen and carbon isotope excursion occurred in antarctic waters near the end of the palaeocene 57 33 myr ago indicating rapid global warming and oceanographic changes that caused one of the largest deep sea benthic extinctions of the past 90 million years in contrast the oceanic plankton were largely unaffected implying a decoupling of the deep and shallow ecosystems the data suggest that for a few thousand years ocean circulation underwent fundamental changes producing a transient state that although brief had long term effects on environmental and biotic evolution

devonian carboniferous boundary glacioeustatic fluctuations in a platform to basin direction a geochemical approach of sequence stratigraphy in pelagic settings abstract we investigated high resolution stratigraphic distribution of selected major and trace elements and gamma ray spectra of fourteen devonian carboniferous d c boundary sections of europe located in the late palaeozoic laurussia and gondwana the aim was to trace the geochemical signature of a marked forced and normal regressive interval which was associated with rapid progradation of siliciclastics into the marine carbonate systems rhenish massif and a prominent hiatus in shallow water ramp settings namur dinant basin this interval represents the late devonian hangenberg event hbe sensu lato middle praesulcata conodont zone as defined by previous authors this regressive interval fsst to lst correlates with thin shale layers hbe shale sandwiched between monotonous nodular calcilutite calcisiltite successions at five pelagic sections of moravia carnic alps montagne noire and pyrenees in all sections with continuous d c sedimentation i e except those of the namur dinant basin the hbe s l interval is accompanied by elevated percentages of detrital proxies al k rb zr and changes in their ratios zr rb k al rb k which are normally interpreted as indicators of increased siliciclastic input provenance and grain size zr rb and other proxies are traceable even without apparent lithological evidence and can therefore facilitate stratigraphic correlation paleoredox and productivity proxies u th and ni rb enrichment factors only rarely show elevated values in the hangenberg black shale interval indicating that the associated water dysoxia anoxia was a local rather than global phenomenon global correlations based on the hbe black shales should therefore be dropped in favor of the hbe s l interval moreover analysis of sedimentation rates in the upper expansa to kockeli zone interval using the published radiometric ages suggests that the hbe s l was a time of significant increase in the rate of siliciclastic supply into the ocean even in the most distal pelagic sections consequently the previous interpretation of the hbe black shale as a condensed succession deposited during rapid sea level rise seems unlikely we interpret the hbe s l i e including the hbe black shale as a marine record of glacioeustatic sea level drop and increased aeolian transport in connection with late devonian climatic cooling and glaciation the set of geochemical markers related to the late devonian sea level fluctuation can be used for super regional to global correlations from platform to basin settings moreover they can facilitate current efforts to determine a new d c boundary definition

geoacoustic and source tracking using particle filtering experimental results a particle filtering pf approach is presented for performing sequential geoacoustic inversion of a complex ocean acoustic environment using a moving acoustic source this approach treats both the environmental parameters e g water column sound speed profile ssp water depth sediment and bottom parameters at the source location and the source parameters e g source depth range and speed as unknown random variables that evolve as the source moves this allows real time updating of the environment and accurate tracking of the moving source as a sequential monte carlo technique that operates on nonlinear systems with non gaussian probability densities the pf is an ideal algorithm to perform tracking of environmental and source parameters and their uncertainties via the evolving posterior probability densities the approach is demonstrated on both simulated data in a shallow water environment with a sloping bottom and experimental data collected during the swellex 96 experiment

interpreting carbon isotope excursions strangelove oceans large negative excursions in marine carbonate delta sup 13 c are commonly associated with period boundaries and mass extinctions explanations for these events must be consistent with limitations imposed by carbon isotope mass balance at steady state i e for excursions lasting more than 10 sup 5 yr the surface ocean delta sup 13 c is set by the organic fraction of the total carbon burial rate and the magnitude of the photosynthetic isotope effect the delta sup 13 c of the deep ocean and the surface to deep isotope gradient are set by both the organic fraction of the ocean s remineralized particulate flux and the magnitude of the isotope effect thus it is the carbon isotope composition of the deep ocean that is most reflective of internal oceanic processes the surface ocean records changes in the longer term throughput of carbon in the system the cessation of organic export from the surface ocean such as is presumed to have caused the strangelove ocean condition of the cretaceous tertiary k t boundary leads to an isotopically homogeneous ocean in decades to centuries if this condition persists the ocean s isotopic composition approaches that of the riverine weathering input in 10 sup 5 yr failure to approach this value during the k t event suggests continued production andmore burial of organic carbon dominantly in either terrestrial or shallow marine environments less

water column anoxia enhanced productivity and concomitant changes in δ13c and δ34s across the frasnian famennian boundary kowala holy cross mountains poland the investigation of the trace element and organic geochemistry of the frasnian famennian boundary section at kowala holy cross mountains poland shows that the lower water column was oxygen deficient during late frasnian and early famennian times the abundance and carbon isotopic composition of diaryl isoprenoids biomarkers indicative for green sulfur bacteria prove that euxinic waters reached into the photic zone at least episodically total organic carbon toc contents show two maxima that are time equivalent to the kellwasser horizons deposited in shallower water settings enhanced toc concentrations are explained by a higher primary productivity presumably as a consequence of an enhanced nutrient supply from the continent the increase in the abundance of hopanes and bituminite suggests that the bacterial contribution to toc increased at the frasnian famennian transition the sulfur isotopic composition of pyritic and organically bound sulfur shows a 27 excursion across the boundary the observation that the 34s values of organic bound sulfur closely resemble that of pyrite sulfur indicates a common sulfur source likely early diagenetic sulfide a change in the 13c of total dissolved inorganic carbon as a consequence of an enhanced burial of 12c enriched organic carbon is indicated by a 3 excursion measured for toc as well as for individual n alkanes and isoprenoids the burial of large amounts of organic carbon is expected to result in a decrease in pco2 and should affect the photosynthetic carbon isotope fractionation ep the fact that we observe no change in ep can be explained by the circumstance that ep was most probably at maximum values as a consequence of high atmospheric and oceanic dissolved co2 concentrations during the devonian

stable isotope toc and caco3 record across the cretaceous tertiary boundary at el kef tunisia we report the results of stable oxygen and carbon isotope analysis of carbonate fine fraction and benthic and planktic foraminifers caco3 and toc determinations of sediments across the cretaceous tertiary k t boundary at el kef tunisia we used grain size analysis of the fine fraction carbonate to determine possible compositional effects and smearslide and scanning electron microscope examinations to evaluate possible diagenetic alteration and microfossil preservation the data suggests the following sequence of events upper maastrichtian oxygen and carbon isotope signals indicate relatively warm temperatures a decreasing thermal gradient possibly related to a shallowing sea and relatively high surface water productivity a sharp cooling appears to begin just below the k t boundary the k t boundary is characterized by a sudden 2 negative shift in fine fraction 13c a slight 0 6 enrichment in benthic 13c and a reduction of about 40 in caco3 sedimentation these data imply strongly reduced surface water productivity as also observed in numerous deep sea sequences worldwide the lower danian planktic foraminiferal zones p0 p1a is marked by generally low productivity and unstable environmental conditions as indicated by generally low but fluctuating fine fraction 13c values and low 5 15 carbonate deposition at the base of subzone p1b caco3 benthic and fine fraction 13c values increase gradually and reach near pre k t boundary levels in subzone p1c indicating initial recovery after the k t boundary event about 300 000 400 000 years after the k t boundary the prolonged low productivity episode after the k t crisis and the pre k t boundary cooling associated with a major reduction in planktic foraminiferal diversity are difficult to explain by a single k t boundary bolide impact

results of a deep tow multichannel survey on the bermuda rise high resolution multichannel seismic data taken with a deep towed source and receiving array are used to obtain estimates of the in situ compressional velocity depth functions within the upper 300 m of deep ocean sediments these data taken on the bermuda rise in an area with a nominal water depth of 5 km resolve structure consistent with dsdp data from the region the velocity depth functions derived from these data indicate little p velocity gradient in the upper 100 170 m of sediments and resolve p velocity inversions within the depth range sampled

drought reconstruction in eastern hulun buir steppe china and its linkages to the sea surface temperatures in the pacific ocean abstract a tree ring width chronology covering the period 1780 2013 ad was developed from pinus sylvestris var mongolica for the eastern hulun buir steppe a region located on the edge of the eastern mongolian plateau china climate growth response analysis revealed drought stress to be the primary limiting factor for tree growth therefore the mean february july standardized precipitation evapotranspiration index spei was reconstructed over the period 1819 2013 where the reconstruction could account for 32 8 of the variance in the instrumental record over the calibration period 1953 2011 comparison with other tree ring based moisture sequences from nearby areas confirmed a high degree of confidence in our reconstruction severe drought intervals since the late 1970s in our study area consisted with the weakening east asian summer monsoon which modulating regional moisture conditions in semi arid zone over northern china drought variations in the study area significantly correlated with sea surface temperatures ssts in north pacific ocean suggesting a possible connection of regional hydroclimatic variations to the pacific decadal oscillation pdo the potential influence associated with el nino southern oscillation enso was primarily analyzed

palaeoenvironmental and palaeoceanographic controls on black laminated mudrock deposition example from devonian carboniferous strata alberta canada abstract sedimentological palaeontological and ichnological analyses indicate that heightened episodes of equatorial upwelling in tandem with an expanded and intensified oxygen minimum zone promoted deposition of upper famennian to lower tournaisian laminated organic rich mud rocks of the exshaw formation on the alberta cratonic platform exshaw mud rocks represent the culmination of an upper devonian transgression that commenced with deposition of open marine carbonates of the big valley formation the transgression was abruptly halted at the devonian carboniferous boundary by a rapid eustatic sea level fall and the consequent deposition of near shore marine to shelfal bioturbated siltstones and sandstones of the exshaw formation the siltstones grade into laminated organic lean mud rocks to the north in more distal offshore shelf settings these mudrocks reflect a period of low primary production but continued anoxia of bottom waters continuation of anoxic conditions resulted from development of restricted circulation in the epicontinental sea due to the establishment of a westward located physical barrier following this event was a relative sea level rise that led to deposition of black laminated mudrocks of the banff formation

april september mean maximum temperature inferred from hailar pine pinus sylvestris var mongolica tree rings in the hulunbuir region inner mongolia back to 1868 ad two robust tree ring width chronologies were developed for the hulunbuir region inner mongolia northeast china both chronologies were significantly correlated with each other and were arithmetically averaged to build a regional chronology nbstd nbstd showed significant and negative correlations with the growing season maximum temperature from april to september based on this relationship the mean maximum temperature of april to september was reconstructed for the period from 1868 to 2008 the percentage of variance in the data explained by the reconstruction was 40 3 during the calibration period of 1953 2008 five severe warm events of two years or more were found in 1905 1909 1996 1997 2000 2001 2003 2005 and 2007 2008 five cold events occurred during the periods 1880 1881 1897 1900 1948 1949 1955 1960 and 1962 1964 on a decadal scale several warm intervals above the 1868 2008 mean were 1904 1913 1920 1933 1968 1975 and 1990 2003 cold intervals below the mean were 1893 1901 1950 1963 and 1976 1989 warmer events and intervals corresponded to dry periods colder events and intervals coincided with wet or moist conditions in and near the study region spatial correlation patterns revealed that our reconstruction represents a regional temperature and drought signal for the central and eastern mongolian plateau comparison with other tree ring based temperature reconstructions from surrounding areas provides a high degree of confidence in our reconstruction power spectrum and wavelet analyses suggest that the reconstructed mean maximum temperature variation may be related to large scale atmospheric oceanic variability such as the pacific decadal oscillation pdo el nino southern oscillation enso and sunspot activity c 2011 elsevier b v all rights reserved less

compressional and shear wave properties of marine sediments comparisons between theory and data according to a recently developed theory of wave propagation in marine sediments the dispersion relationships for the phase speed and attenuation of the compressional and the shear wave depend on only three macroscopic physical variables porosity grain size and depth in the sediment the dispersion relations also involve three real parameters assigned fixed values representing microscopic processes occurring at grain contacts the dispersion relationships are compared with extensive data sets taken from the literature covering the four wave properties as functions of all three physical variables with no adjustable parameters available the theory matches accurately the trends of all the data sets this agreement extends to the compressional and shear attenuations in that the theory accurately traces out the lower bound to the widely distributed measured attenuations the theory predicts the intrinsic attenuation arising from the irreversible conversion of wave energy into heat whereas the measurements return the effective attenuation which includes the intrinsic attenuation plus additional sources of loss such as scattering from shell fragments and other inhomogeneities in the medium provided one wave or physical property is known say the compressional speed or the porosity all the remaining sediment properties may be reliably estimated from the theory

in situ seismic measurements in borehole lb 08a in the bosumtwi impact structure ghana preliminary interpretation in order to assist in the interpretation of previous seismic refraction and reflection surveys a vertical seismic profile was acquired in the lake bosumtwi ghana hard rock core hole lb 08a no seismic reflections are seen in the up going wave field obtained and this observation is consistent with the lack of reflectivity observed in the corresponding 2 d surface seismic profile obtained in earlier studies direct down going p waves were found both in the cased sediment column from a depth of 73 m to 239 m below the lake surface and in the open hole hard rock section from a depth of 239 m to 451 m of lb 08a analysis of the observed travel times indicates a nearly constant p wave velocity of 1520 m s through the soft lacustrine sediments in the hard rock however the p wave velocity rapidly increases by nearly 30 from 2600 m s to 3340 m s these values are in good agreement with the gross velocity structure obtained in the earlier joint inversion of seismic reflection and refraction data these values are low relative to those expected for the metasedimentary protoliths an observation that has been made at other young impact structures of similar size the low velocities together with the fact that they increase so rapidly is suggestive of a decreasing density of fractures and microcracks with depth consequently the seismic velocity trend may provide a proxy measure of damage and hence the decay of the shock pressure from the impact point validation of this requires additional detailed studies of the porosity structure in the core

distributions and vertical variation patterns of sound speed of surface sediments in south china sea the distributions of sound speed show different characteristics in continental shelf continental slope and nansha trough the differences have closely related to the distributions of sediment physical properties in the southern south china sea according to the analysis of sound speeds and physical properties variation characteristics with buried depth the vertical variations of sound speed are closely related to sediment texture sedimentary environment transport erosion compaction consolidation etc the comparison results indicate 3 vertical variation patterns of sound speed increasing model invariant model and complicate variation model the above 3 variation models represent the vertical distribution characteristics of sound speed in different depositional environments different variation patterns have different key factors which generally contain porosity or grain size the calculated sound speeds with buckingham s theory of compressional waves in fluid like marine sediments follows the trend of measured speeds accurately c 2014 elsevier ltd all rights reserved

biochronological aspects of the devonian carboniferous crisis in the regions of the former ussr abstract the devonia carboniferous d c event recorded in the vast region of the former ussr has been analyzed using a systematic biochronological approach this approach is based on the procedure of distinguishing in each fossil group taxa with long ranging tempoendemic time specific tempotonic intermediate and ephemeride abnormal archetypes the primary components of a zonal assemblage system among different fossil groups are not specific taxa but the combined features of all taxa characterized by archetypes the d c event is recorded by drastic changes in the compositions of ammonoid and partially conodont faunas in west european paleobasins belonging to the atlantic realm in the former ussr the d c crisis is most profoundly expressed in the east european region in the kazakhstan altayan and east siberian regions of the pacific realm several discrete events can be discriminated in both realms major changes among most fossil groups took place at or near the strunian hangenbergian boundary at the d c boundary compositional and structural changes in fossil groups were gradual except for ammonoids there were no mass extinctions of devonian taxa followed by the sudden radiations of carboniferous taxa the most important consequence of the d c event was the appearance of taxa with essentially new archetypes which became dominant components of the carboniferous paleobiota

late cenozoic sediment drift complex northeast rockall trough north atlantic seismic reflection profiles and two shallow cores have revealed a sediment drift complex in the northeastern rockall trough the drift complex consists of an elongate drift with associated sediment waves a broad sheeted drift with a larger field of sediment waves and smaller moat related isolated drifts the internal reflection configuration of these features indicates consistent upslope migration throughout the late cenozoic the larger field of sediment waves has been described previously with a southerly migration a reevalution of these waves suggests a migration direction to the east conforming with the other drift complex features the most vigorous current activity probably occurred during the miocene with a more reduced current flow prevailing during the pliocene to holocene interval core evidence from the elongate drift and the moat has revealed upper pleistocene and lower holocene glaciomarine sediments reworked to produce muddy silty and sandy contourites sedimentation rates for the early holocene pre 7 5 ka are up to 4 times greater on the drift compared to the moat it is suggested that the sediment drift complex has formed through the interaction of a northward flowing slope current of north atlantic deep water origin with an area of complex bathymetry at the northeastern end of the rockall trough where the wyville thomson ridge intersects the hebridean margin

fine scale la icp ms study of redox oscillations and reey cycling during the latest devonian hangenberg crisis moravian karst czech republic abstract trace elementsand reey distribution of thinly laminated limestone laminite and underlying pre event calciturbidite siphonodella praesulcata conodont zone deposited in association with the hangenberg black shale event were analyzed using laser ablation inductively coupled plasma mass spectrometry these deposits were also analyzed by carbonate petrography and scanning electron microscopy our study documents the origin of authigenic microbial limestones during the latest devonian hangenberg extinction event when unusual oceanic conditions appear to have enhanced precipitation of calcite within microbial carbonates detrital contamination of the calciturbidite and laminated limestone is very low as demonstrated by low contents of al zr ti and th these deposits display only limited degree of early diagenetic overprint of limestones and some of them fall within or very close to the seawater field elevated u and mo enrichments and covariation patterns reflect the episodic establishment of oxic to euxinic bottom condition during deposition of the laminite the oxic conditions that existed during accumulation of the underlying calciturbidite were likely the result of turbidity current introduction of oxygen into the bottom environment ree contents of both the laminite and calciturbidite are nearly ten times higher than those of most modern carbonates and similar to devonian microbialites from the canning basin calciturbidite display a prominent mreen bulge shale normalized ree patterns of the overlying laminite are similar to those of modern seawater and devonian microbialites from the canning basin lree depletion and progressive enrichments in heavier ree reflecting the dominance of authigenic carbonate phases minor contamination is bound to apatites siliciclastic minerals pyrites and organic matter the element content of authigenic phases benefited from fe and mn oxyhydroxide redox cycling negative ce and positive eu anomalies low y ho ratios and very low al al fe mn ratios suggest an influence of diluted high temperature hydrothermal fluids perhaps related to latest devonian rift magmatism in the eastern part of the rhenohercynian zone the proliferation of anachronistic facies following the devonian carboniferous d c extinction event recognized in moravia and traced worldwide seems to share some features in common with anachronistic carbonate sequences documented in the aftermath of the end permian mass extinction

post glacial depositional environments in a mid high latitude glacially overdeepened sea loch inner loch etive western scotland abstract a high resolution seismic and gravity coring survey has been conducted on inner and part of outer loch etive a 30 km long 150 m deep sea loch on the west coast of scotland the seismic reflection profiles reveal a 30 60 m thick sediment pile that has accumulated on the floor of the loch since the last younger dryas stadial glacial re advance 11 10 ka bp four seismic facies have been identified grouped into two seismic sequences a and b which are separated by a distinct reflector termed e1 a highly reflective facies is interpreted as direct river input an acoustically well laminated draped facies interpreted as fine grained river sediments and a well laminated to transparent facies interpreted as glaciomarine and glaciolacustrine throughout the loch methane gas rich sediments occur producing a chaotic seismic facies the transition from glacially influenced to river dominated deposition is displayed by the seismic reflector e1 core analysis identified eight lithofacies the oldest sediments are grey muddy sands and olive sandy silts overlain by younger laminated greeny grey muddy sand and greeny grey and greeny black homogeneous watery sandy mud abundant shell material is present throughout notably the bivalve arctica islandica from which a 14 c age of 9490 90 yr bp was obtained from the laminated greeny grey muddy sands the sediments are interpreted as being of glaciomarine and glaciolacustrine younger dryas to early mid holocene and more modern riverine derived origin mid latest holocene

carbon and sulfur isotope anomalies across the frasnian famennian extinction boundary alberta canada stable isotopes of carbonate and organic carbon from two upper devonian sections in alberta canada indicate a heavy carbon event across the frasnian famennian f f boundary and a negative 13 c shift at the boundary at cinquefoil mountain 13 c values in carbonate are anomalously high 3 5 to 4 5 pdb peedee belemnite within an interval 10 m below to 23 m above the f f boundary representing about 1 m y two standard conodont zones compared to background values of 1 above and below this interval superimposed on this positive excursion is a marked 13 c decrease of about 1 at precisely the f f boundary at medicine lake a similar 13 c excursion in organic carbon from a background of 29 to a high of 26 5 is recorded across the f f boundary the 34 s data for iron sulfide in these sections show unusually high values as much as 15 to 20 cdt canon diablo troilite in the f f boundary interval these data together with those from other areas indicate a period of major global changes e g greenhouse and marine anoxia that took place well before and after the sudden biomass killing event at the f f boundary existing evidence suggests that the f f mass extinction was probably caused by a large extraterrestrial impact on earth at a time when the global ecosystem was already severely stressed

submarine landslide deposits of the historical lateral collapse of ritter island papua new guinea abstract the march 13th 1888 collapse of ritter island in papua new guinea is the largest known sector collapse of an island volcano in historical times one single event removed most of the island and its western submarine flank and produced a landslide deposit that extends at least 70 km from the headwall of the collapse scar we have mapped and described the deposits of the debris avalanche left by the collapse using full coverage multibeam bathymetry side scan sonar backscatter intensity mapping chirp seismic reflection profiles towcam photographs of the seafloor and samples from a single dredge applying concepts originally developed on the 1980 mount st helens collapse landslide deposits we find that the ritter landslide deposits show three distinct morphological facies large block debris avalanche matrix rich debris avalanche and distal debris flow facies restoring the island s land and submarine topography we obtained a volume of 4 2 km3 for the initial collapse about 75 of which is now forming the large block facies at distances less than 12 km from the collapse scar the matrix rich facies volume is unknown but large scale erosion of the marine sediment substrate yielded a minimum total volume of 6 4 km3 in the distal debris flow and or turbidite deposits highlighting the efficiency of substrate erosion during the later history of the landslide movement although studying submarine landslide deposits we can never have the same confidence that subaerial observations provide our analysis shows that well exposed submarine landslide deposits can be interpreted in a similar way to subaerial volcano collapse deposits and that they can in turn be used to interpret older incompletely exposed submarine landslide deposits studying the deposits from a facies perspective provides the basis for reconstructing the kinematics of a collapse event landslide understanding the mechanisms involved in its movement and deposition and so providing key inputs to tsunami models

high resolution stable isotope stratigraphy of upper ordovician sequences constraints on the timing of bioevents and environmental changes associated with mass extinction and glaciation the two phases of the late ordovician mass extinction are approximately coeval with the periods of rapid climate change associated with the onset and demise of the gondwanan glaciation in this paper we argue that the distinctive late ordovician carbon isotope profile provides a chronostratigraphic ruler against which a sequence of environmental and biotic events may be located the ruler also allows regional and global high resolution correlation of successions representing very different environments cores from the upper ordovician succession of estonia and latvia record a large 1 3 c c a r b o n a t e excursion up to 6 with a similar profile shape the consistent relationship between the chemostratigraphy and biostratigraphy in the baltic region suggests that the isotope profile has a regional chronostratigraphic value the presence of similar profiles in nevada united states suggests that the excursion is a global chronostratigraphic signal this interpretation enables a detailed correlation to be made between upper ordovician shallow marine and basinal sequences that have wholly different faunas successions in the baltic area and in canada that do not display the model profile are interpreted as incomplete reinter pretation of these important successions significantly modifies the global database used to assess the pattern of diversity change during the mass extinction key levels of environmental change have been located against the carbon isotope profile new oxygen isotope data from brachiopod and ostracode calcite set tight limits on the start of the glacial events cooling and sea level fall started at the same stratigraphic level as the start of the carbon isotope excursion the later rise in sea level and fall in oxygen isotope values record the end of the glaciation these restrict the duration of the main glaciation to only 1 5 graptolite zones we propose that models of the carbon cycle should be adapted to be consistent with the temporal relationships between carbon cycling sea level fall and temperature change documented here the chronostratigraphic ruler provided by the carbon isotope profiles is used as a scale to determine the sequence of biotic changes and to allow high resolution correlation of biotic events at different locations this approach identifies regional similarities and differences in the patterns of extinction the main phase of graptolite extinction in the monitor range nevada for example is synchronous with the chitinozoan extinction in the baltic region but chitinozoan taxa survive to higher levels in nevada the benthic faunas in the baltic region demonstrate that the main extinction event corresponded with the beginning of the isotope excursion at the start of the hirnantian the level at which the marine environment started to change rapidly but that there were further extinctions of species within the early hirnantian the cold adapted hirnantia fauna did not appear immediately after the extinction in this area the relationship between the second phase of extinction and the carbon isotope excursion is less clear but the available data suggest that the extinction coincides with a time of rapid environmental change but not at the inception of environmental change as happened in the first phase

the whole rock cerium anomaly a potential indicator of eustatic sea level changes in shales of the anoxic facies abstract the whole rock cerium anomaly tested for outer shelf upper slope stratigraphic sections from the middle ordovician through the lower silurian of scotland is proposed as an empirical technique to develop a eustatic 3rd order or finer scale sea level curve this interval was chosen as it straddles the well documented late ordovician glaciation and can be defined by graptolite zones the anomaly is calculated from neutron activation analysis of low carbonate phosphate free fossil free field identified shales of the graptolite facies by comparison of the normalized cerium content with the linearized trend of the normalized composition of other rare earth elements in order of atomic number for sections originally deposited in the main pycnocline below the surface mixed layer values of the anomaly for a given sample would indicate its position on the redox curves developed for the early paleozoic by wilde 1987 changes in the anomaly that are positive with time would indicate a lowering of sea level as the apparent depth on the redox curve would reflect more oxic conditions relative changes negative with time would indicate a rise in sea level as the apparent depth reflects more anoxic conditions depending on the vertical sample spacing and the time interval sampled resolution of the order of 1 m y might be achieved thus the vail et al 1977 curves of the 3rd order 1 to 10 m y or of finer scale could be obtained by this technique with the proper choice of section accordingly for the early through middle paleozoic when the main pycnocline was anoxic this geochemical technique could be used to develop eustatic sea level curves and additionally offer an independent calibration for seismic stratigraphy as well as an indicator of glacial interglacial climatic sequences or eustatic changes due to fluctuations in global ridge crest volumes

geochemical record of late devonian to early carboniferous events palaeozoic of graz eastern alps austria the late famennian mass extinction has been associated with a worldwide anoxic event evidenced at many sites by the accumulation of organic rich shales starting prior to the devonian carboniferous d c boundary environmental reconstructions are hampered by the fact that only a few d c boundary sections exist in carbonate facies one of these is the palaeozoic steinberg section eastern alps austria based on detailed geochemical investigations and correlation with previously investigated sections we propose a succession of events from the late famennian to the tournaisian both the low total rare earth element ree contents and the normalized ree distribution patterns indicate low terrigenous input from the praesulcata zone to the typicus zone the dc do ds and total organic content toc show a shift towards higher values which correlates well with the late famennian isotopic trends that are related to a period of active ocean circulation cooling and increased productivity two isotopic shifts are present in the section the older isotopic shift of the dc values is situated at the level of the lower to middle praesulcata zone while the younger one is found at the level of the upper praesulcata zone in the sulcata zone a sharp decrease in do values and a shift in the ce anomaly follow concomitantly a drop in the dc and ds values highly variable toc values and the main and secondary element concentrations are interpreted to be related to a drop in primary productivity with the recovery continuing in the crenulata zone in this context the variations towards lower cao sr rb and ba values probably correlate with biomass variations and a transition from cooler towards warmer conditions the mass extinction that occurred prior to the devonian carboniferous d c boundary was the sixth largest extinction of the phanerozoic sepkoski 1996 it mainly affected pelagic and hemipelagic organisms e g conodonts ammonoids echinoderms trilobites ancient agnathan and placodermian fishes continental plant communities and to a lesser extent shallow marine ostracods foraminifera and corals paproth streel 1984 flajs et al 1988 becker paproth 1993 simakov 1993 becker 1994 sepkoski 1996 streel et al 2000 a short time after the extinction there was a phase of radiation and biotic innovations caplan bustin 1999 streel et al 2000 this phase was characterized by the diversification of certain groups of organisms such as tetrapods walliser 1996 subsequent palaeontological advances have shown that changes in different groups of marine organisms and terrestrial plants are not synchronous streel et al 2000 the late famennian is characterized by the occurrence of a grey shale level and sometimes black shales known as hangenberg shale after a locality in the rheinisches schiefergebirge germany schmidt 1924 the hangenberg shale shows variable lithology with the black shale not always occurring at the base bless et al 1988 worldwide the d c sections display similar lithoand biostratigraphy consisting of a lower cephalopod limestone shale and an upper cephalopod limestone walliser 1984 although there is little agreement on the estimation of the absolute age of the d c boundary gradstein et al 2004 and references therein the shales appear even when the famennian strata occur in carbonate ramp settings or are situated at lower latitudes walliser 1984 caplan et al 1996 the position of the d c global boundary stratotype has been defined at the first appearance of the conodont siphonodella sulcata within the evolutionary lineage from from g siewicz a slowakiewicz m eds palaeozoic climate cycles their evolutionary and sedimentological impact geological society london special publications 376 http dx doi org 10 1144 sp376 15 the geological society of london 2013 publishing disclaimer www geolsoc org uk pub ethics by guest on september 20 2013 http sp lyellcollection org downloaded from

tree ring based summer temperature regime reconstruction in xiaoxing anling mountains northeastern china since 1772 ce abstract long term paleoclimatic variability based on high resolution proxy records such as tree ring data are scarce for the xiaoxing anling mountains of china we developed a new tree ring width chronology from korean pine pinus koraiensis spanning the period 1667 2015 climate growth correlation analysis revealed that early growing season temperature was the main climatic factor controlling tree ring growth june mean temperatures from 1772 to 2015 were reconstructed using the standard chronology these results provide the first dendroclimatological reconstruction based on growing season temperature in the xiaoxing anling mountains reconstruction results explained 39 3 of climatic variance over the calibration period 1959 2015 and they indicated that the central xiaoxing anling mountains have experienced six major warm periods five major cold periods and several cold years that coincided with a sequence of major tropical volcanic eruptions temperature reconstructions have successfully captured the most recent climatic warming events and are consistent with other reconstructions from nearby regions on decadal timescales spatial climate correlation analyses with a gridded temperature dataset revealed that our temperature reconstructions contain strong regional temperature signals for the eastern eurasian continent power spectrum revealed the existence of significant frequency cycles of variability at 2 0 2 3 2 5 2 7 2 9 3 0 3 4 4 5 5 6 7 2 7 5 8 0 8 2 8 9 9 9 10 5 11 5 and 70 5 years which may be linked to large scale atmospheric oceanic variability such as the el nino southern oscillation solar activity and the pacific decadal oscillation this reconstruction improves our understanding of long term temperature variation for the xiaoxing anling mountains of china but it can also be used to predict tree growth dynamics within the study area

seismic stratigraphy of the shatsky rise sediment cap northwest pacific and implications for pelagic sedimentation atop submarine plateaus abstract pelagic sediments accumulated atop shatsky rise since early cretaceous time provide a valuable record of pacific paleoceanography the accepted sedimentation model invokes relatively continuous pelagic sediment accumulation punctuated by four regional hiatuses caused by changes in oceanic chemistry that framework was proposed more than two decades in the past and based on low quality single channel seismic profiles it was developed at the center of tamu massif the main topographic high of shatsky rise and extended to other highs with uncertainty owing to sparse data the availability of high quality seismic data and additional coring by the ocean drilling program and integrated ocean drilling program allows a re examination seismic and core data indicate that sedimentation atop shatsky rise has been complex with regional and local variability four major hiatuses were previously defined and tentatively correlated to nearby topographic highs these breaks occurred approximately during the aptian barremian and cenomanian coniacian ages of the cretaceous and during the paleocene and oligocene epochs of the cenozoic they are of variable length and tend to be of shorter duration at the summit of tamu massif but of longer durations elsewhere all produced erosional unconformities that may be related to mass wasting of the sediment cap edges each hiatus is approximately correlated with global falls of sea level suggesting a connection perhaps to intensified bottom currents at those times local variability is observed in the form of discontinuous layering non uniform sedimentation thinning of the sediment caps at their edges and local erosion near topographic highs these variations are likely the result of shifting bottom currents possibly resulting from interactions of internal tides with topography shatsky rise sedimentation is inherently punctuated and non uniform and the sedimentary record includes significant lateral variability other large oceanic plateaus are likely to exhibit similar sedimentary cap complexities

a new model for atmospheric oxygen over phanerozoic time a mathematical model has been constructed that enables calculation of the level of atmospheric o2 over the past 570 my from rates of burial and weathering of organic carbon c and pyrite sulfur s burial rates as a function of time are calculated from an assumed constant worldwide clastic sedimentation rate and the relative abundance and c and s contents of the three rock types marine sandstones and shales coal basin sediments and other non marine clastics red beds arkoses by our model values of o2 versus time using a constant total sedimentation rate agree with those for variable sedimentation derived from present day rock abundances and estimates of erosional losses since deposition this agreement is the result of our reliance on the idea that any increase in total worldwide sediment burial with consequently faster burial of c and s and greater o2 production must be accompanied by a corresponding increase in erosion and increased exposure of c and s on the continents to o2 consumption via weathering it is the redistribution of sediment between the three different rock types and not total sedimentation rate that is important in o2 control to add stability to the system negative feedback against excessive o2 fluctuation was provided in the modeling by the geologically reasonable assignment of higher weathering rates to younger rocks resulting in rapid recycling of c and s we did not use direct o2 negative feedback on either weathering of c and s or burial of c because weathering rates are assumed to be limited by uplift and erosion and the burial rate of c limited by the rate of sediment deposition the latter assumption is the result of modern sediment studies which show that marine organic matter burial occurs mainly in oxygenated shallow water and is limited by the rate of supply of nutrients to the oceans by rivers results of the modeling indicate that atmospheric o2 probably has varied appreciably over phanerozoic time during the late carboniferous and permian periods o2 was higher than previously because of the rise of vascular land plants and the widespread burial of organic matter in vast coal swamps a large decrease in o2 during the late permian was due probably to the drying up of the coal swamps and deposition of a large proportion of total sediment in c and s free continental red beds sensitivity study shows that major parameters affecting results are the mean c concentration in coal basins and the relative sizes of the reservoirs of young rapidly recycled versus old rocks less sensitivity was found for changes over time in total land area undergoing weathering and the use of direct o2 negative feedback on marine carbon burial good agreement for rates of c burial calculated via our model and via independent models which are based on the use of stable carbon isotopes indicates that the dominant factor that has brought about changes in atmospheric o2 level and the isotopic composition of dissolved inorganic carbon in seawater over phanerozoic time is sedimentation and not weathering or higher temperature phenomena such as basalt seawater reaction

global change at the paleocene eocene boundary climatic and evolutionary consequences of tectonic events rea d k zachos j c owen r m and gingerich p d 1990 global change at the paleocene eocene boundary climatic and evolutionary consequences of tectonic events palaeogeogr palaeoclimatol palaeoecol 79 117 128 events of the paleocene eocene boundary provide the clearest example to date of how a tectonic event may have global climatic consequences recent advances permit well constrained stratigraphic determination of several events that occurred at that boundary in chron c24r a many fold increase in sea floor hydrothermal activity a global warming a reduction in the intensity of atmospheric circulation a conversion to salinity driven deep ocean circulation a marked lightening of oceanic 313c values extinction and evolution of both benthic foraminifera and land mammals and important plate boundary reorganizations including the outpouring of the east greenland volcanics and the initiation of the oceanic rift between norway and greenland we hypothesize that enhanced sea floor hydrothermal activity occasioned by global tectonism resulted in a flooding of the atmosphere with coz causing a reduced pole to equator temperature gradient and increased evaporation at low latitudes increased formation of warm salty probably low nutrient waters coupled with the warm temperatures at high latitudes occasioned a salinity driven rather than temperature driven deep water circulation this newly evolved ocean circulation pattern changed the apportionment of global heat transport from the atmosphere to the ocean with concomitant changes in the circulation intensity of both reduced intensity of atmospheric circulation resulted in lower oceanic biological productivity and enhanced seasonality of climate on the continents a major extinction event among benthic foraminifera was probably a response to the new low nutrient and chemically changed bottom waters and endemism following rapid evolution and dispersal of mammalian orders may have been in response to the new continental climate regime

ocean nutrient distribution and oxygenation limits on the formation of warm saline bottom water over the past 91 m y it has been proposed that deep water formation in the oceans would be quite different during geologic intervals with reduced equator to pole temperature gradients salinity rather than temperature differences might drive the deep ocean circulation saline water would tend to form at subtropical latitudes where evaporation exceeds precipitation we point out a likely consequence of warm saline bottom water formation on ocean chemistry the tendency to drive the ocean toward anoxia this effect is not due to the previously noted lower oxygen solubility with increasing ocean temperature but rather to the increased efficiency with which plankton will extract nutrients from convecting waters at low latitudes the present ocean nutrient content is sufficient to induce deep water anoxia if circulation were to change yet anoxia is rare in the paleoceanographic record a simple ocean chemical model makes explicit the tradeoffs between mean ocean nutrient content and circulation parameters that will satisfy the geologic observations of an oxygenated ocean since the mid cretaceous barring decreases of ocean phosphate on the order of 30 50 deep water formation at high latitudes was a major source of ocean ventilation in the warmer past

a multiproxy index of the el nino southern oscillation a d 1525 1982 1 an understanding of past variability in the el nino southern oscillation enso on interannual interdecadal and longer time scales would be useful in assessing recent observed changes to enso and in determining the realism of climate model simulations using tree ring coral and ice core data we reconstruct a proxy based enso index between a d 1525 and 1982 unlike most previous studies which have drawn climate proxies from limited geographic regions our network is pacific basin wide using enso sensitive proxies from the western equatorial pacific new zealand the central pacific and subtropical north america by considering multiple teleconnection regions this network provides a more robust proxy enso signal the common signal recorded in the multiproxy network has a high correlation with the southern oscillation index soi nino 3 4 sea surface temperature nino3 4 sst and a combined ocean atmosphere enso index cei the proportion of instrumental variance explained is 47 for the soi 48 for nino3 4 sst and 52 for the cei the proxy enso index also displays skill in reproducing warm and cold extremes of the soi the proxy enso index over the last 450 years shows considerable amplitude and frequency modulation in the 3 10 year band on multidecadal time scales there is a relative reduction in the amplitude of high frequency variability during the sixteenth early seventeenth and mid eighteenth centuries in contrast high frequency enso variability has increased over the last 200 years variability during the first half of the twentieth century is similar to that evident in the nineteenth century

brachiopods as indicators of original isotopic compositions in some paleozoic limestones the original stable isotopic composition of paleozoic marine carbonate rocks is important to establish a baseline for evaluating diagenetic alteration and providing a reliable data base for modeling exogenic geochemical cycles of the elements we have compared the 18 o and 13 c values in the nonluminescent portions of brachiopods with similar published data of whole brachiopods other whole fossils and estimates of original isotopic composition of marine cements the oxygen and carbon isotopic records for each of these paleozoic components show generally good internal consistency significant discrepancies however were noted between results on the different components isotopic and trace element data presented in this study suggest that permo carboniferous whole brachiopods are little altered chemically nonetheless a more reliable but not fool proof approach for obtaining pristine isotopic values is microsampling of least altered regions based on cathodoluminescence in conjunction with staining techniques and elemental analyses the carbon and oxygen isotopic compositions of all components decrease in 18 o and 13 c in geologically older material neither temporal trend is monotonic however oxygen isotopic results suggest an important positive shift in 18 o of about 2 during the early carboniferous whereas the carbon isotope trend shows a major positive shift 2 3 during the mid carboniferous

sediment drifts and contourites on the continental margin off northwest britain abstract seismic reflection profiles and short cores from the continental margin off northwest britain have revealed a variety of sediment drift styles and contourite deposits preserved in the northeast rockall trough and faeroe shetland channel the sediment drifts include 1 distinctly mounded elongate drifts both single and multi crested 2 broad sheeted drift forms varying from gently domed to flat lying and 3 isolated patch drifts including moat related drifts fields of sediment waves are locally developed in association with the elongate and gently domed broad sheeted drifts the contrasting styles of the sediment drifts most probably reflect the interaction between a variable bottom current regime and the complex bathymetry of the continental margin the bulk of the mounded gently domed drifts occur in the northeast rockall trough whereas the flat lying sheet form deposits occur in the faeroe shetland channel a much narrower basin which appears to have been an area more of sediment export than drift accumulation patch drifts are present in both basins in the northeast rockall trough the along strike variation from single to multi crested elongate drifts may be a response to bottom current changes influenced by developing drift topography muddy silty muddy and sandy contourites have been recovered in sediment cores from the uppermost parts of the drift sequences on the basis of their glaciomarine origin these mid to high latitude contourites can be referred to collectively as glacigenic contourites both partial and complete contourite sequences are preserved the former consist largely of sandy mid only and top only contourites sandy contourites by their coarse grained nature and their formation under strongest bottom current flows are the most likely to be preserved in the rock record however the very large scale of sediment drifts should be borne in mind with regard to the recognition of fossil contourites in ancient successions

a weathering hypothesis for glaciation at high atmospheric pco2 during the late ordovician new paired carbonate and organic carbon isotope analyses from nevada usa together with a consideration of the effects of mountain building and ice sheet coverage of the continents on atmospheric pco2 lead to a new hypothesis for the cause of the late ordovician glaciation we suggest that the taconic orogeny which commenced in the late middle ordovician caused a long term decline in atmospheric pco2 through increased weatherability of silicate rocks ice sheet growth was triggered when pco2 decreased to a threshold of 10 present atmospheric level and proceeded by positive ice albedo feedback in the midst of glaciation atmospheric pco2 began to rise as continental silicate weathering rates declined in response to coverage of weathering terrains by ice sheets at first this enhanced greenhouse effect was overcompensated for by ice albedo effects ultimately however atmospheric pco2 reached a level which overwhelmed the cooling effects of ice albedo and the glaciation ended the isotope results can be interpreted to indicate that atmospheric pco2 rose during the glaciation consistent with other proxy information although alternative interpretations are possible the large positive carbonate isotope excursion observed in late ordovician rocks around the world is explained as the expected response to increased carbonate platform weathering during glacioeustatic sea level lowstand rather than as a response to increased organic carbon burial

geochemistry of brachiopods oxygen and carbon isotopic records of paleozoic oceans abstract combined trace element and isotope studies of 319 brachiopods covering the ordovician to permian time span show that 13c and 18o in well preserved specimens varied during the paleozoic the overall 13c secular trend is in accord with the previously published observations but its details are obscured by vital isotopic fractionation effects at generic level nonetheless the results suggest that the negative correlation between marine 13ccarbonate and 34ssulphate deteriorates at time scales of 106 years due to the long residence time and thus slow response of so42 in the ocean for oxygen isotopes all devonian and older specimens have 18o of 4 while the well preserved permian samples have near present day 18o of about 1 pdb this isotopic dichotomy is probably not due to post depositional phenomena salinity or biogenic fractionation effects this leaves open the perennial arguments for a change in 18 o 16 o of sea water versus warmer ancient oceans the present data are difficult to explain solely by the temperature alternative the coincidence of the proposed shift in 18o with the large late paleozoic changes in marine 87 sr 86 sr 13 c 12 c 34 s 32 s and sea level stands argues for a tectonic cause and for a change in 18 o 16 o of sea water although such explanation is difficult to reconcile with global balance considerations and with isotopic patterns observed in alteration products of ancient basalts and ophiolites whatever the precise cause or combination of causes the implications for tectonism and or paleoclimatology are of first order significance

paraglacial slope instability in scottish fjords examples from little loch broom nw scotland lateglacial holocene fjord sediments in little loch broom preserve evidence of extensive slope instability the major area of reworking is in the outer loch and mid loch sill region where ice contact ice proximal deposits of the lateglacial assynt glacigenic formation have been disrupted by sliding and mass flow processes linked to the little loch broom slide complex and the adjacent badcaul slide mass failure was instigated about14 13 ka bp and is probably the response of the landscape to deglaciation immediately following the removal of ice support during glacial retreat an initial phase of translational sliding was followed by rotational sliding as revealed by the superimposition of scalloped shaped slumps on a larger scale rectilinear pattern of failure paraglacial landscape readjustment may have also been enhanced by episodic seismic activity linked to glacio isostatic unloading in the inner fjord evidence of holocene mass failure includes the ardessie debris lobe and a discrete intact slide block preserved within the postglacial basinal deposits the former is a localised accumulation linked to a fluvial catchment on the adjacent an teallach massif these mass transport deposits may represent an ongoing response to paraglacial processes albeit much reduced relative to the major slides in terms of sediment supply to the fjord

deep marine seabed erosion and gravel lags in the northwestern rockall trough north atlantic ocean a zone of active seabed erosion has been identified in the northwestern rockall trough using seismic reflection profiles and cores the region from george bligh bank to rockall bank has been subject to vigorous bottom current activity for at least the last 35 ma bottom currents originate from southward flowing north atlantic deep water in water depths of 500 2000 m acoustic character mapping reveals a zone of erosion extending over 8500 km 2 along the northwestern margins of the trough the erosion surface is characterized by an acoustically reflective seabed with occasional parallel to transparent reflectors these are the result of strong bottom currents exposing the underlying volcanic basement drift sequences and fan sediments the erosion surface is covered by a

warm saline bottom water in the ancient ocean considerable isotopic evidence indicates that oceanic bottom water was much warmer in the geological past a simple convection model driven by multiple turbulent buoyant plumes and observations of present deep water formation have led to the development of a theory for the formation of warm saline bottom water it is suggested that changes in the size and configuration of marginal seas in net evaporation zones due to lithospheric plate motions and eustatic sea level change caused these seas to become sources of warm saline bottom water evidence from the palaeotemperature record and palaeogeography during the late cretaceous is used to reinforce the hypothesis climatic and chemical consequences of the formation of warm saline bottom water are discussed

tree ring density based warm season temperature reconstruction since a d 1610 in the eastern tibetan plateau tree ring samples from purple cone spruce picea purpurea were collected at four sites on the eastern tibetan plateau maximum latewood density mxd was measured by x ray densitometry and a regional standard chronology was established from the four mxd chronologies using the regional curve standardization rcs method based on significant correlation between the regional rcs chronology and mean april september temperature warm season april september temperature variability was reconstructed back to 1610 for the eastern tibetan plateau the reconstruction explained 58 5 of the variance in the instrumental period 1961 to 2009 in the past 400 years there were five cold periods with lower than average and four warm periods with higher than average the temperature reconstruction captured the unprecedented warming in the 20th century where the last ten years were the warmest decade in the last 400 years the ensemble empirical mode decomposition eemd was used to extract the multi scale fluctuation of the temperature reconstruction four quasi oscillations with periodicities of 2 2 2 7 years 5 1 7 9 years 11 9 15 4 years and 21 8 26 2 years indicated major fluctuations of original temperature agreement with other temperature proxies implied a high degree of confidence for our reconstruction and its large scale spatial representation the temperature reconstruction showed a warming trend on a longer time scale in the eastern tibetan plateau c 2015 elsevier b v all rights reserved

isotope signatures associated with early meteoric diagenesis the environments in which carbonate diagenesis proceeds have been documented in previous studies of holocene and late pleistocene sediments and limestones on barbados west indies variations in the carbon and oxygen isotopic composition of limestones produced during early freshwater diagenesis have been observed in this study to occur in specific patterns six potentially useful patterns emerge when one views stable isotope data within a stratigraphic framework 1 the subaerial exposure surface is characterized by strongly 12c enriched limestones 13c compositions of underlying limestones grow progressively heavier with increasing depth 2 the subaerial exposure surface may also be marked by slight 18o enrichment 3 an abrupt shift in 18o values may differentiate sediments above the exposure surface from those below 4 sediments altered in the marine meteoric mixing zone may be characterized by positive covariance between their 18o and 13c compositions 5 the vadose phreatic boundary may be marked by a sharp increase in 13c values in the seaward portions of a fresh groundwater system and 6 samples contemporaneously altered in a single fresh groundwater system within an areally restricted region should display a narrow range of 18o and a wide range of 13c compositions analysis of samples from five palaeozoic and mesozoic formations which contained petrographic evidence of early freshwater diagenesis showed that isotope patterns similar to those observed in barbados limestones have been preserved in rocks as old as mississippian these isotope patterns could prove to be useful for identifying diagenetically induced porosity trends in carbonate rocks they might be used to identify limestones diagenetically altered in meteoric environments to identify mixing zone cements and dolomites and to trace the regional and vertical distributions of early meteoric groundwater systems in ancient carbonate formations

seabed morphology and the bottom current pathways around rosemary bank seamount northern rockall trough north atlantic rosemary bank is a broadly domed and elongate seamount with a diameter of 70 km occurring in water depths of between 300 and 2300 m 120 km west of the uk mainland in the northern rockall trough recent multibeam bathymetry and sub bottom profiles together with pre existing current meter and ctd data seismic reflection profiles and seabed core samples were examined in order to evaluate past and present bottom current pathways and processes the multibeam data image volcanic parasitic cones concave slide scars and the terraced slopes of the bank bottom current sedimentation is interpreted as producing a drift moat complex surrounding the entire seamount and including two sediment wave fields developed to the west and east of the bank in water depths of 1500 2000 m the western drift covers an area of over 1000 km2 sediment waves to the west of the bank are up to 150 m high with wave lengths of 1 5 2 km four 100 m deep 3 km wide linear depressions bisect the waves and are interpreted as 25 30 km long extensions of the moat seismic reflection profiles show the main phase of drift construction was during the mid miocene to pliocene with the pliocene to holocene being an interval of drift maintenance cores from sediments draping over and adjacent to the seamount contain sandy and gravelly contourites interbedded with hemipelagites of late pleistocene to holocene age current meter and ctd data from the western moat indicate labrador sea water flowing northwest in contrast to the previously assumed anticlockwise circulation pattern around the seamount

sound velocity as a function of depth in marine sediments additional data from sonobuoys and the deep sea drilling project dsdp justify separating sound velocity depth functions and velocity gradients in the first layer of soft marine sediments into some geographic areas and sediment types based on sonobuoy and core measurements where v is sound velocity in km s and h is depth in sediments in km the following data are obtained continental shelf basins off sumatra and java v 1 484 0 710h 0 085h2 u s atlantic continental rise v 1 513 0 828h 0 138h2 deep sea terrigenous sediments v 1 519 1 227h 0 473h2 and siliceous sediments of the bering sea v 1 509 0 869h 0 267h2 selected dsdp data through leg 74 in similar areas yield continental terrace silt clays v 1 505 0 712h deep sea terrigenous sediments v 1 510 1 019h and deep sea siliceous sediments v 1 533 0 761h computed velocity gradients from sonobuoy measurements are generally supported by the dsdp gradients only dsdp data give the following hemipelagic sediments v 1 501 1 151h deep sea ca

august temperature variability in the southeastern tibetan plateau since ad 1385 inferred from tree rings long term high resolution climate proxies are essential for understanding climate variability on the tibetan plateau tp where few long term climate records are available in this paper we describe a summer august temperature reconstruction over the period 1385 2002 based on a tree ring width chronology of balfour spruce picea likiangensis var balfouriana on the southeastern tp created using the regional curve standardization method the reconstruction explains 44 7 of the variance in the instrumental temperature records during the calibration period 1962 2002 and captures temperature variability over a broad region of the tp warmer than average augusts were found during the periods 1446 1494 1509 1522 1553 1567 1797 1812 1845 1905 and 1918 2002 cooler than average augusts occurred from 1385 1416 1426 1445 1495 1508 1523 1552 1568 1686 1695 1718 1725 1796 1813 1844 and 1906 1917 a warming trend in the 20th century was unprecedented during the past six centuries the reconstruction closely matched other tree ring summer temperature reconstructions from neighboring regions as well as patterns from ice core delta 18 o data and fluctuated in synchrony with northern hemisphere temperature reconstructions c 2011 elsevier b v all rights reserved

constraints in using cerium anomaly of bulk sediments as an indicator of paleo bottom water redox environment a case study from the central indian ocean basin abstract the total rare earth elements ree abundance along with major and a range of trace element chemistry of twenty eight sub sections in a 5 m long sediment core aas 05 gc 02 from the central indian ocean basin shows a distinct ree fractionation sediments from the top 1 m of the core have comparatively low ree abundance close to average shale with a sample shale ree ratio very close to 1 strongly suggesting a dominantly terrigenous source the down core ree abundance shows a nearly two fold increase ree 167 341 ppm with depth and the ree strongly co varies with mn ti p and smectite inter element correlations and the shale normalized ree patterns suggest that light middle and heavy ree are selectively carried by terrigenous mn oxide and authigenic phosphate phases respectively suggesting a distinct ree fractionation these fractionation effects become more pronounced with increasing depth in the core the cerium ce anomaly in marine sediments is used as one of the promising tools to trace paleo bottom water redox conditions and this varies in the sediments from 0 10 to 0 08 the ce anomaly in general is positive in the top 4 m but the top 1 m have higher ce anomaly mn ti and ce ti suggest sediment deposition relatively under more oxic bottom water condition the negative ce anomaly between 4 and 5 m depth which could be interpreted to indicate a suboxic anoxic environment the redox environment inferred by the ce anomaly is compared to a number of other redox sensitive parameters to test its reliability these include mn content total organic carbon u th authigenic uranium cu zn and v cr ratio that all suggestive of deposition of sediments under oxygenated bottom water condition thus the negative ce anomaly observed between 4 and 5 m core depth does not represent a suboxic anoxic environment but is more likely due to the retention of a negative ce anomaly caused by authigenic phosphate and authigenic fe rich smectite which is formed by the reaction between iron oxyhydroxide and biogenic opal suggests an early diagenetic process and is in equilibrium with seawater ree early diagenetic process is responsible for the part of negative ce anomaly observed here therefore we suggest that the ce anomaly of bulk sediments as an indicator of paleo ocean bottom water redox conditions needs to be used with a caution

enso signal in continental temperature and precipitation records warm events in the tropical pacific ocean associated with one extreme of the southern oscillation generally known as el nino southern oscillation or enso events are now known to be of global significance in perturbing the general circulation of the atmosphere1 8 it is also apparent that episodes of enhanced cold water upwelling cold events have an impact on large scale atmospheric circulation patterns9 11 here we examine the effect of warm and cold events on short term fluctuations of continental surface air temperature and precipitation throughout the northern hemisphere using a newly compiled set of high quality temperature and precipitation data12 13 the data were in the form of gridded anomalies from a 1951 70 reference mean for temperature and a 1921 60 reference mean for precipitation13 14

tracing paleoredox conditions across the devonian carboniferous boundary event a case study from carbonate dominated settings of belgium the czech republic and northern france the devonian carboniferous boundary was coeval with the hangenberg crisis which is regarded as a first order mass extinction event related with large sea level changes and widespread anoxia this study aims to trace the geochemical paleoproductivity and paleoredox proxies across the devonian carboniferous carbonate dominated successions of the namur dinant basin belgium northern france and the moravo silesian basin czech republic located in the variscan rhenohercynian zone the research was focused on the distribution of oxides sio2 al2o3 fe2o3 cao na2o k2o tio2 mno and trace elements th u v zr mo zn pb ni cu measured by icp oes and icp ms respectively the enrichment factors of mo and u and their ratios were used as the main paleoredox proxies whereas the enrichment factors of zn cu pb and ni were employed to trace the paleoproductivity changes high values of zr al2o3 0 001 tio2 al2o3 0 06 and fe ti 20 and low values of al al fe mn 035 coinciding with an increase of paleoredox proxies suggest a possible volcanic and hydrothermal source of nutrients related to late devonian and early carboniferous extensional magmatism in the rhenohercynian domain although a relationship between higher paleoproductivity and enhanced continental runoff of volcanic material cannot be excluded the studied devonian carboniferous boundary sections from the namur dinant basin gendron celles ardennes quarry reveal three levels with similar vectors of mo and u enrichments the pre crisis famennian pattern is typical for weakly restricted basins with fe mn redox cycling accompanying vertical fluctuations of the oxic anoxic chemocline close to the sediment water interface with the influence of particulate shuttle the mo ef and u ef patterns corresponding to the unrestricted or weakly restricted basin with alternating suboxic to anoxic conditions are considered to represent the transgressive hangenberg black shale event the lower tournaisian mo ef and u ef patterns fall along a vector in the direction of the strongly restricted marine conditions with prevailing suboxic conditions in the moravo silesian basin lesni lom section the pre crisis famennian mo ef and u ef vector indicates an unrestricted marine trend which converges with that of restricted systems redox conditions range from suboxic to euxinic in the tournaisian mo ef and u ef oscillate between oxic and anoxic conditions and fall along a vector of strongly restricted marine conditions increased isolation of both studied basins in the early tournaisian is regarded as a reflection of a significant eustatic fall during the hangenberg crisis linked to a severe episode of the gondwana glaciation these paleohydrographic patterns have correlative potential that should be considered for a revised devonian carboniferous boundary definition

land sea correlations and evolution of the cambridge fiord marine basin during the last deglaciation of northern baffin island abstract cambridge fiord functions as a major outlet trough whenever laurentide ice approaches the eastern coast of baffin island during the last glacial maximum late foxe glaciation an outlet glacier occupied most of the fiord possibly terminating as far seaward as buchan gulf glacier retreat began prior to 8800 yr b p and was punctuated by the formation of two onshore moraines with upper age limits of 7900 and 7200 yr b p correlative offshore moraines recognized on seismic reflection profiles formed prominent submarine sills which partitioned the fiord into three basins these formed effective sediment traps that restricted the seaward migration of debris flows and turbidites thus facilitating the accumulation of thick 100 m stratified glacialmarine sediments in the inner fiord correlations of onshore and offshore moraines allow time lines to be placed within an offshore seismic stratigraphic section that is inaccessible to piston coring resultant estimates of sediment accumulation rates give a mean value of 2 34 10 6 m 3 yer for deposits trapped in the inner fiord basins these thick sequences of sediments do not represent extended foxe wisconsin time periods but rather were rapidly deposited in the inner fiord during the last deglaciation

lateglacial ice cap dynamics in nw scotland evidence from the fjords of the summer isles region abstract the seaboard of western scotland is a classic fjord landscape formed by glaciation over at least the last 0 5 ma we examine the glacial geology preserved in the fjords or sea lochs of the summer isles region of nw scotland using high resolution seismic data multibeam swath bathymetry seabed sediment cores digital terrain models aerial photographs and field investigations detailed analyses include seismic facies and lithofacies interpretations sedimentological and palaeoenvironmental analyses and radiocarbon dating of selected microfauna our results indicate that the pleistocene sediments of the summer isles region on and offshore can be subdivided into several lithostratigraphic formations on the basis of seismic character geomorphology and sedimentology these are subglacial tills ice distal and glacimarine facies ice proximal and ice contact facies moraine assemblages and holocene basin fill the submarine landscape is also notable for its large scale mass movement events the result of glaciodynamic paraglacial or seismotectonic processes radiocarbon dating of marine shells indicate that deglaciation of this part of nw scotland was ongoing between 14 and 13 ka bp during the lateglacial interstadial greenland interstadial 1 consistent with cosmogenic surface exposure ages from previous studies a sequence of numerous seafloor moraine ridges charts oscillatory retreat of the last ice sheet from a buoyant calving margin in the minch to a firmly grounded margin amongst the summer isles in the early part of lateglacial interstadial gi 1 pre 14 ka bp subsequent punctuated frontal retreat of the ice mass occurred in the following 1000 years during which time ice cap outlet glaciers became topographically confined and restricted to the fjords a late stage readvance of glaciers into the inner fjords occurred soon after 13 ka bp which calls into question the accepted limits of ice extent during the younger dryas stadial greenland stadial 1 we examine the wider implications of our chronostratigraphic model discussing the implications for british ice sheet deglaciation lateglacial climate change and the style and rates of fjord sedimentation

geochemical events documented in inorganic carbon isotopes abstract screening of sampling and analytical data is crucial for the detection of real global shifts in marine 13c against the noise of diagenesis the real global shifts of 13c are of two types 1 long term secular shifts caused by changes in the fractional burial of organic carbon and 2 transient shifts caused by abrupt changes of biological productivity in the surface photic zone both are applicable to stratigraphic correlation but differ in their application to modelling of changes in oceanographic or atmospheric composition a recent compilation found 34 carbon isotope events in the phanerozoic and neoproterozoic equally distributed among positive and negative shifts this in itself attests to a variety of proximate causes of the shifts