coarse grained sediment gravity flow facies in a large supraglacial lake near williams lake in the central interior of british columbia the fraser river exposes long sections of late pleistocene glaciolacustrine sediments selectively preserved within a bedrock trough the dominant facies types are thick normally graded gravels and sands that occupy steeply dipping multistorey channels up to 300 m wide and several tens of metres deep channels appear to have been simultaneously cut and filled by high density turbidity currents in a glacial lake floored by stagnant ice fining upward sediment gravity flow sequences up to 50 m thick may be the product of quasi continuous surging turbidity flows triggered by catastrophic meltwater discharges into the trough or retrogressive failure of ice cored sediments large scale post depositional deformation structures such as synclinal folds normal faults sedimentary dyke swarms and dewatering structures record gravitational foundering of sediment and pore water expulsion caused by the melt of underlying glacier ice melting of buried ice masses along the floor of the trough appears to have controlled the flow paths of turbidity currents by producing sub basins within the overlying sediment pile an idealized model of supraglacial lacustrine sedimentation is developed that may be applicable to other glaciated areas with similar bedrock topography

glacial lake camelsfoot a late wisconsinan advance stage proglacial lake in the fraser river valley gang ranch area british columbia in the gang ranch area british columbia interaction between the regional physiography and ice flow during the late wisconsinan fraser glaciation resulted in the formation of a proglacial lake confined to valleys of the fraser river and its tributaries lithostratigraphic and geomorphic evidence suggests that ponding was initiated in the big bar creek area where the fraser river is confined to a deep canyon in the camelsfoot range during ice advance a proglacial lake system developed that progressively deepened and reached a minimum upper elevation of approximately 710 m asl prior to being overridden by ice we propose that this system be formally named glacial lake camelsfoot a composite stratotype comprising lithostratigraphic units associated with glacial lake camelsfoot is described from eight reference sections along fraser river churn and lone cabin creeks in the gang ranch area additional geomorphic evidence indicates that at the fraser glaciation maximum the cordilleran ice sheet in th

patterns in the distribution of aptian rudists and corals within a sequence stratigraphic framework maestrat basin e spain abstract the ecological zonation of and environmental controls on rudist and coral assemblages on carbonate platforms of the old world have received more attention for late cretaceous examples than for their early cretaceous counterparts this study accordingly investigates the vertical and lateral distribution of aptian rudist bivalves and scleractinian corals on a carbonate platform succession from the western maestrat basin e iberian peninsula here colonial corals grew profusely on an isolated platform top environment during an earliest highstand stage of a long term trend of relative sea level as well as on marly slope settings during higher frequency transgressive pulses during the later highstand stage within a longer term relative sea level cycle a facies belt dominated by autochthonous rudist bivalves overlaid the coral meadow that had developed on the isolated platform top the internal part of this carbonate platform with rudists is dominated by slender elevator caprinids such as caprina parvula whereas requieniids and polyconitids predominate in the external zone the abundance of caprinids in the internal platform is remarkable given that caprinid lithosomes of late early aptian age are usually rare in the northern margin of the tethys the proliferation of caprinids in this case was probably favoured by the apparently more isolated nature of the carbonate platform on the slopes the coral communities that flourished during higher frequency transgressive pulses are overlain by carbonates with rudists mainly requieniids shed from the platform top during normal and forced regressive higher frequency changes of relative sea level accordingly the vertical change from coral dominated to rudist dominated facies in both platform top and slope settings records progradation to decipher the long term relative sea level changes that controlled the deposition of this carbonate succession a sequence stratigraphic analysis was performed two depositional sequences including a late early aptian intra dufrenoyia furcata zone forced regressive stage of relative sea level which subaerially exposed and incised the early aptian succession to a depth of 21 m were recognised the incisions were back filled with peritidal deposits during the subsequent marine onlap the rudist and coral bearing carbonates were deposited along platform top to slope profiles lacking a barrier margin and hence lagoon environments

glacial lake invermere upper columbia river valley british columbia a paleogeographic reconstruction terraces of thick lacustrine silt and deltaic gravel flank parts of the valley floor of the rocky mountain trench between skookumchuck and donald british columbia these indicate the presence of f

phosphogenesis and weathering of shelf sediments from the southeastern united states implications for miocene δ13c excursions and global cooling the enormous phosphorite deposits of the southeastern united states indicate intense upwelling but contain small amounts of organic carbon the authors propose that deposition of organic rich sediment on continental shelves in the southeastern united states and elsewhere during marine transgressions in the late oligocene and early to middle miocene resulted in global positive delta sup 13 c shifts and the formation of early diagenetic phosphorite multiple reworking and supergene weathering from subaerial exposure during miocene marine regressions oxidized most of the organic carbon and resulted in the return of delta sup 13 c to its preexcursion value the estimated phosphorite content of the southeastern united states requires sufficient organic carbon burial 10 sup 15 kg carbon to support a 1 per thousand delta sup 13 c excursions sea level fluctuations organic carbon burial phosphogenic episodes and possibly global cooling during the cenozoic

genesis of the stratiform zhenzigou pb zn deposit in the north china craton rb sr and c o s pb isotope constraints abstract isotopes rb sr c o s and pb were investigated from the zhenzigou pb zn deposit in the qingchengzi mineral field qmf of the north china craton as an aid to determine the genesis of stratiform pb zn deposits in the liao ji rift a step dissolution rb sr age of 1798 8 ma with 206pb 204pb ratios of 17 7477 17 8527 were obtained from sphalerite sulfur isotopic ratios for pyrite 5 14 4 sphalerite 2 4 8 6 and galena 0 3 8 6 from zhenzigou have a narrower range than those from the host paleoproterozoic dashiqiao formation and granite in the area calcite and limestone from ore and wallrocks at the deposit have similar c and o isotope compositions with 13cpdb ranging from 6 0 to 2 3 and 18osmow from 9 8 to 13 7 which are similar to those of carbonatite and the mantle comprehensive analysis of the pb isotopic composition of the sulfide from the zhenzigou deposit and pb zn deposits in adjacent area show that the pb originated from the upper crust and mixed with pb from the mantle sulfur isotopes from zhenzigou deposit indicate that the mineralization has a volcanic eruption source the 13cpdb and 18osmow values indicate that the co2 originated from a mixed mantle marine carbonate and organic source combined with the study of regional metallogenic background this paper proposes that deposition of stratiform pb zn mineralization in the qmf began ca 2052 ma during development of the liaoji rift the mineralization extended to ca 1798 ma prior to deformation associated with the lvliang movement which dismembered the stratiform pb zn mineralization the veined mineralization in the region cross cuts the stratiform deposits and represents remobilized and redeposited deposits associated with the emplacement of triassic plutons such as the xinling and shuangdinggou granites

longitudinal transport of turbidity currents a model study of horgen events experiments were carried out in a 10 6 m basin to simulate turbidity currents generated by the horgen slumping events of 1875 the conditions for kinematic similarity were satisfied and the experiments gave further insight into the mechanics of transport triggered by the horgen slumps the experimental turbidity currents laid down thick deposits on a subaqueous fan and thin sheets of turbidite on the floor of the elongate basin through longitudinal transport comparable with the simulated deposits in lake zurich it is concluded that longitudinal transport is a general phenomenon of turbidity currents

salt dome controlled sulfide precipitation of paleoproterozoic fe cu sulfide deposits eastern liaoning northeastern china the lower portion of the paleoproterozoic northern liaohe group liaoning northeast china comprises metavolcanics tuff dominated and metasediments mostly arkoses and dolostones that host stratiform strata bound fe cu sulfides and ca ba sulfates the ore bearing sequence consists of in ascending order pyroclastic rocks terrigenous clastics and carbonates all of which have been metamorphosed to greenschist amphibolite grade extensive albite rich breccias are present at the base of the succession and as pipes crosscutting a variety of lithologic units in the lieryu formation the geometry geochemistry and associated structures of these albite rich rocks suggest that they are metamorphosed salt domes the sulfide sulfate fe cu ores occur in a transitional zone between tuffs and dolomitic carbonates with those in the upper cycle being economically more important the sulfides were precipitated at two sites around venting centers as breccias lenses and veins and as stratiform pyrite chalcopyrite associated with anhydrite that is distal to the salt domes within each mining district the proximal ores are associated with brecciated albite and tourmaline rich rocks the sulfides in the proximal ores have delta 34 s values of 8 9 to 12 7 per mil whereas the distal ores have delta 34 s values of 2 6 to 8 8 per mil for the sulfides and 7 9 to 19 0 per mil for the anhydrite suggesting a sulfate dominated sulfur source with the pyrite delta 34 s variations arising mainly from decreasing temperatures away from the centers of the deposits the origin of the deposits is best described by a model in which sulfate carbonate rocks were deposited in peripheral sinks during salt diapirism the salt domes then acted as focuses for subsequent hydrothermal venting and were the centers of sulfide mineralization the sulfides precipitated during interaction of the reduced metal bearing hydrothermal fluids with the in situ sulfates that were the major source of the sulfur

trace metal evidence for changes in the redox environment associated with the transition from terrigenous clay to diatomaceous sediment saanich inlet bc abstract we measured the concentrations of redox sensitive trace metals mn v mo u cd and re in sediments from odp leg 169s hole 1033b in saanich inlet british columbia to determine changes in redox conditions associated with the onset of laminated sediments at 12 5 kyr the most striking result is a large peak in authigenic re along with detrital levels of mo at the glacial terrigenous clay diatomaceous sediment transition in contrast the underlying glacial terrigenous clay which extends throughout the bottom section of the core is chemically similar to detrital concentrations either cowichan river particulates or average shale values these data suggest a period of oxic bottom waters but reducing pore waters this could be due to the dramatic transformation of saanich inlet during the late deglaciation from an open bay to an inlet which restricted circulation and slowed bottom water oxygen renewal a peak and gradual increase in authigenic mn in younger sediments subsequent to the re peak suggests that increasingly oxic conditions followed the authigenic enrichment in re these conditions could be connected to the younger dryas cooling period which was coincident with an increase in well oxygenated upwelled waters on the west coast of north america that form the bottom waters of saanich inlet metal concentrations in a gray clay bed 11 kyr are similar to their concentrations in the glacial terrigenous clay implying that they have a common source authigenic enrichments of re with little authigenic mo and cd suggest that before the deposition of this bed bottom waters were oxic and pore water oxygen was consumed in the top centimeter or less laminations above the clay layer suggest anoxic conditions which are also indicated by higher authigenic mo and cd and slightly lower re mo ratios in these sediments the basin remained mostly anoxic after the gray clay was emplaced as seen by continuous authigenic enrichment of the redox sensitive trace metals these results are consistent with increased stratification of the water column brought about by an influx of fresh water to the basin by a large flood

the thickness of neogene and quaternary cover across the central interior plateau british columbia analysis of water well drill records and implications for mineral exploration potential abstract analysis of over 10 000 water well records has been used to produce new depth to bedrock maps for areas around five cities on the central interior plateau of central british columbia 100 mile house prince george quesnel vanderhoof and williams lake hitherto exploration for mineral and hydrocarbon resources has been hampered by a lack of basic knowledge of the thickness of neogene and quaternary lithologies interpretation of these new maps provides first order constraints on the localization of thick drift in pre late wisconsinan bedrock paleovalleys some of which are now buried basalt lavas of the chilcotin group are restricted to erosional remnants of previously extensive sheets emplaced onto an older peneplain our results confirm that the neogene and quaternary cover is primarily controlled by paleotopography and is generally thin and patchy across much of the region increased understanding of the three dimensional distribution of cover produces a corresponding increase in the utility of geological geochemical and geophysical exploration techniques and a reduction in the risk for future mineral exploration activities especially when combined with more sophisticated data sets

evolution of the subglacial hydrologic system beneath the rapidly decaying cordilleran ice sheet caused by ice dammed lake drainage implications for meltwater induced ice acceleration abstract a positive correlation between ice dammed lake drainage and ice acceleration at antarctic ice sheets ais and land terminating sections of the greenland ice sheet gris has been implicated in enhanced ice sheet decay however the paucity of direct measurements at the ice sheet bed restricts our understanding of subglacial drainage system evolution in response to transient water inputs we present evidence that two meltwater corridors on the former bed of the thin 600 m at last glacial maximum over the interior plateaus of british columbia and rapidly decaying cordilleran ice sheet cis were generated subglacially in response to the drainage of an ice dammed lake and operated as canals tunnel channels geomorphological ground penetrating radar gpr and electrical resistivity tomography ert data reveal a simple event sequence that includes initial propagation of a broad at least 2 5 km wide floodwave inefficient drainage from an ice dammed lake over relatively short 3 24 km zones at the corridor heads that collapsed into efficient canals large up to 0 25 2 5 km wide channels incised down into the sediment bed and up into the ice downglacier canal formation on the southern fraser plateau involved synchronous along the full canal length system development including elements of headward erosion and plunge pool formation our data suggest that ice dammed lake drainage beneath a rapidly decaying thin ice mass that has an efficient antecedent drainage network is not conducive to large scale ice acceleration these data may aid better assessment of the role of ice dammed lake drainage on the dynamics of former as well as contemporary ice sheets

a depositional model for rogen moraine with examples from the avalon peninsula newfoundland rogen moraine is explained by subglacial meltwater processes through a form analogy between moraine ridges and ripples produced on the underside of river ice this mechanism for rogen moraine formation is compatible with the meltwater hypothesis for drumlins a unified explanation for rogen moraines and drumlins is attractive and necessary because they are part of a continuum the meltwater hypothesis is tested on rogen moraine of the avalon peninsula newfoundland mapping shows that ice and meltwater flowed northeastwards from st mary s bay and fanned out across the peninsula the sedimentology of four moraine ridges and one moraine hummock favours deposition in subglacial cavities sediment in the ridges travelled only short distances and there is abundant evidence of water sorting and deposition from debris flows bedding within ridges conforms with surface slopes and clast fabrics relate to local morphology rather than to the regional ice flow direction additional sedimentary observations from qu

late pleistocene stratigraphy and implications for deglaciation and subglacial processes of the flathead lobe of the cordilleran ice sheet flathead valley montana usa abstract the flathead lobe of the cordilleran ice sheet advanced and retreated across the flathead valley a 90 km long by 15 25 km wide basin the glacier terminated at the southern end of the flathead valley during its last glacial maximum i used geologic mapping sedimentologic study and mapping from 3300 descriptive water well logs to define the stratigraphy of glacial and post glacial deposits in the flathead valley and to infer subglacial processes and retreat rates units in the 30 200 m thick stratigraphic sequence include deep sand and gravel proglacial alluvium diamicton till locally gravelly silt and clay coarse grained subaqueous deposits at recessional moraines and glaciolacustrine deposits and surficial sand and gravel outwash and holocene stream deposits a nearly continuous till overlies alluvium and is in turn directly overlain by glaciolacustrine deposits glaciolacustrine shoreline indicators at altitudes of 940 958 m show that the flathead lobe receded as a proglacial lake expanded in that range of altitudes this lake the ancestral flathead lake was impounded behind bedrock that was downcut 60 78 m since the late pleistocene glaciolacustrine deposits are as much as 180 m thick in discontinuous troughs that locally cut through till to alluvium and bedrock the troughs are mostly 1 5 km in width 6 25 km in length sinuous in plan view and undulatory in longitudinal profile the troughs extend below the elevation of flathead lake and have been below local base level since glaciation these characteristics point to incision by meltwater hydrostatically pressurized beneath the flathead lobe in subglacial tunnel channels sand and gravel at the trough bases and part of the glaciolacustrine fill in the troughs are subglacial deposits tunnel channels that terminate at recessional moraines suggest excavation occurred sporadically during deglaciation the distribution of glaciolacustrine silts indicates that the flathead lobe retreated and the ancestral flathead lake expanded by 87 km before the lake outlet stream could downcut its dam by 500 m year 1

phosphogenesis carbon isotope stratigraphy and carbonate platform evolution along the lower cretaceous northern tethyan margin we distinguish three different stages in the evolution of the tithonian late jurassic to aptian early cretaceous northern tethyan carbonate platform 1 carbonate production in the coral oolite mode late tithonian to early valanginian early barremian to early aptian 2 carbonate production in the crinoid bryozoan mode early valanginian haute rivian late aptian and 3 platform retrogradation and destruction condensation and phosphogenesis that is platform drowning early valanginian to early hauterivian middle hauterivian late hauterivian to early barremian early to early late aptian and latest aptian to earliest albian transitions from the coral oolite mode to the crinoid bryozoan mode and consequently to platform drowning may have been driven by increases in nutrient levels on the shelf phases of relative sea level rise in times of carbonate production in the coral oolite mode are named constructive because of the observed platform regeneration following phases of widespread emersion during late sea level highstands in contrast phases of relative sea level rise in times of platform drowning are termed destructive the 13 c stratigraphies obtained from valanginian hauterivian and aptian albian hemipelagic successions beyond the platform correlate well with the early cretaceous pelagic 13 c record positive excursions in the pelagic 13 c record correspond in time to episodes of platform drowning this suggests the existence of a coupling mechanism between changes in the global carbon cycle and platform drowning in our view the early cretaceous crises in carbonate platform growth were the consequence of reinforced greenhouse conditions which may have been triggered by episodes of extensive flood basalt volcanism strong greenhouse conditions may have induced the following chain of feedback mechanisms enabling the biosphere to return to normal conditions climate warming sea level rise accelerated water cycle intensified weathering nutrient mobilization platform destruction increased productivity increased phosphogenesis and carbon burial weakened greenhouse conditions

lateglacial ice dynamics of the cordilleran ice sheet in northern british columbia and southern yukon territory retreat pattern of the liard lobe reconstructed from the glacial landform record the liard lobe formed a part of the northeastern sector of the cordilleran ice sheet and drained ice from accumulation areas in the selwyn pelly cassiar and skeena mountains this study reconstru

quaternary stratigraphy and history williams lake british columbia thick valley fill sediments in the vicinity of williams lake british columbia provide a detailed record of the late quaternary history of an area near the centre of the former cordilleran ice sheet stratigraphic units assigned to the late wisconsinan fraser glaciation the preceding penultimate glaciation and the present interglaciation are described especially noteworthy are 1 thick units of sand and gravel deposited by braided streams perhaps during periods of ice sheet growth and 2 complex glaciolacustrine sediments that accumulated in ice dammed lakes during periods of deglaciation glaciers from the coast and cariboo mountains coalesced and flowed north over central british columbia during late wisconsinan time fraser glaciation advance sediments and older pleistocene deposits were partially removed by this ice sheet and the eroded remnants were mantled with till at the end of the fraser glaciation the cordilleran ice sheet downwasted and retreated southward along an irregular front a

record of large late pleistocene outburst floods preserved in saanich inlet sediments vancouver island canada abstract two anomalous gray silty clay beds are present in odp cores collected from saanich inlet vancouver island british columbia canada the beds which date to about 10 500 14c yr bp 11 000 calendar years bp contain tertiary pollen derived from sedimentary rocks found only in the fraser lowland on the mainland of british columbia and washington just east of the strait of georgia abundant illite muscovite in the sediments supports a fraser lowland provenance the clay beds are probably distal deposits of huge floods that swept through the fraser lowland at the end of the pleistocene muddy overflow plumes from these floods crossed the strait of georgia and entered saanich inlet where the sediment settled from suspension and blanketed diatom rich mud on the fiord floor the likely source of the floods is late pleistocene ice dammed lakes in the fraser and thompson valleys which are known to have drained at about the time the floods occurred

multiple flow and support mechanisms and the development of inverse grading in a subaquatic glacigenic debris flow subaquatic glacigenic debris flows of late wisconsinan age occur as lobes within an ice marginal glaciomarine lithofacies at victoria british columbia flow was initiated by release of supraglacial debris during an interval of glacial ablation prior to advance and deposition of lodgement till many of the lobes developed a common morphology during deposition consisting of an outer layer surrounding an inner core of rafted material in the largest lobe reworking of the sediment during flow produced improved sorting a coarsening of mean grain size and a shift in skewness toward the negative this occurred simultaneously within the core and outer layer as a result of different transformations in mechanisms of flow and support normal grading produced in the outer layer was conveyed around the nose and buried in an inverse position along the base of the flow these data enable us to present a model that may be applicable to similar flows elsewhere the flow studied demonstrates that transformations between flow types and sediment support mechanisms can occur simultaneously and serially in subaquatic debris flows

paleoproterozoic positive δ13ccarb excursion in the northeastern sino korean craton evidence of the lomagundi event abstract the 2 33 2 06 ga positive 13 c carb excursion associated with environmental change and the breakup of the kenorland or superia supercontinent is called the lomagundi or jatulian event or great oxidation event and has been reported in many early precambrian cratons but not yet in the sino korean craton the guanmenshan formation of the liaohe group occurs in the northeastern part of the sino korean craton 13 c carb and 18 o values in 42 samples from this formation range from 3 5 5 9 v pdb and 15 4 24 8 v smow respectively showing a clear positive 13 c carb excursion that characterizes the lomagundi event thirty five of the 42 samples with less hydrothermal alteration have higher 13 c carb and 18 o carb values than the other 7 samples obviously affected by fluid flow confirming that it was fluid flow that reduced the 13 c carb and 18 o carb values this positive 13 c carb excursion places deposition of the guanmenshan formation within the age range of 2 33 2 06 ga

thermoluminescence dating applied to glaciolacustrine sediments from central british columbia glaciolacustrine and lacustrine sediments are important indicators of deglacial interglacial and nonglacial intervals within the quaternary of canada yet there are no techniques for measuring their absolute deposition ages beyond the last 50 000 years in an attempt to develop an absolute dating tool for such sediments we applied the partial bleach thermoluminescence tl dating technique to glaciolacustrine sediments of known age from central british columbia samples were selected to represent both ice proximal and ice distal deposition and different modes of sedimentation the results show clearly that both tl procedures and sedimentation processes as reflected in the particle size and sedimentary structures of the samples critically affected the accuracy of tl apparent ages specifically care was required to isolate the effects of laboratory overbleaching apparent glow curve shifts and inappropriate regression analysis clay dominant layers lacking silt or sand interlayers produced expected

cyclostratigraphy and high frequency carbon isotope fluctuations in upper cretaceous shallow water carbonates southern italy a detailed carbon isotope study has been carried out on a santonian upper cretaceous carbonate platform succession that crops out at monte sant erasmo southern italy previous centimetre scale studies on this succession have shown that high frequency eustatic changes resulting from the earth s orbital fluctuations controlled the hierarchical organization of the depositional and early diagenetic features in elementary cycles bundles groups of three to five elementary cycles and superbundles groups of three or four bundles the elementary cycles which correspond to single beds suggest a control caused by earth s precession the bundles and superbundles record the short 100 kyr and long 400 kyr eccentricity periodicity respectively the 1 3 c signal of the monte sant erasmo succession is cyclic in nature and may be considered to be a reliable proxy for the sedimentary evolution and related sea level history of the analysed sequence the carbon isotope cyclicity is recorded at bundle and superbundle level but it is not evident at the scale of the elementary cycles at least with the sampling interval used in this study spectral analysis of the 1 3 c record shows two main peaks corresponding to the short and long eccentricity periodicity whereas the precession signal is not evident in the power spectrum in addition lithofacies analysis shows that in each bundle and superbundle higher c isotope values occur in sediments characterized by marine cements whereas lower values are normally found in more restricted deposits overprinted by early meteoric diagenesis early diagenesis driven by periodic sea level fluctuations developed in either shallow subtidal marine diagenesis or subaerial exposed meteoric overprint sedimentary environments and directly influenced the carbon isotope signature as a consequence the 1 3 c record at monte sant erasmo reflects high frequency climatic oscillations controlling both environmental and early diagenetic changes the long term isotopic record is similar to that of contemporaneous pelagic sections in england and elsewhere in italy it is concluded that the 1 3 c signature of shallow water carbonates such as those of monte sant erasmo offers great potential for correlation with coeval sections including those of the pelagic realm

the phosphorus cycle phosphogenesis and marine phosphate rich deposits abstract phosphorus in the form of phosphate is an essential nutrient and energy carrier on many different levels of life and a key element in mediating between living and lifeless parts of the biosphere one of the most important aspects of the phosphorus cycle is its vital role in governing productivity thereby interacting with the exogenic part of the carbon cycle which in turn is important in regulating earth s climate phosphorus is a prime element to be traced in earth s history because it allows for the reconstruction of long term feedback mechanisms between climate environment and ecology and of global change as such marine sedimentary phosphate deposits are particularly suited to study aspects of the phosphorus cycle because in the case of ubiquity their origin may result from a general acceleration of the global phosphorus cycle sources of sedimentary phosphate are microbial breakdown of buried organic matter and redox driven phosphate desorption from iron and manganese oxyhydroxides dissolved sea water phosphate represents an additional source which may become important in the formation of phosphatic hardgrounds the main locus of phosphogenesis is near the sediment water interface but phosphogenesis also occurs at greater sediment depths current induced winnowing and transport processes along the sea floor concentrate phosphate precipitates into deposits which exhibit internal stratification patterns typical for the prevailing hydraulic energy regime in a sequence stratigraphic context phosphate deposits preferentially occur along marine or maximum flooding surfaces consequent sedimentary reworking may result in the transfer of phosphates to highstand or lowstand deposits bio chemical weathering on continents represents the most significant source of bioavailable phosphorus this implies that long term changes in marine phosphorus levels and with these changes in marine ecology productivity rates and ratios of exported carbonate carbon and organic carbon are a response to changes in continental weathering rates a compilation of marine sedimentary phosphorus burial rates for the last 160 myr suggests that natural variations have occurred that span one order of magnitude for the late jurassic cretaceous and most of the paleogene the phosphorus cycle appears to have been accelerated in times of climate warming which was most likely due to the spreading of zones of humid climate and more intense continental weathering in the neogene the phosphorus cycle appears to have responded to changes in glacially induced weathering this suggests that uniform interpretations with respect to the emplacement of major phosphorite deposits should be treated with caution integrated analyses of the sedimentary and biogeochemical context of phosphorite occurrences may help to identify paleoenvironmental conditions as well as to improve our understanding of periods of enhanced phosphate accumulation periods which were usually characterized by steep gradients in the development of climate and environment with regard to the complexity of feedback mechanisms between the phosphorus cycle and the biosphere the present day input rates of phosphate into the world s oceans should be of great concern they are more than doubled by anthropogenic means and affect ecological systems on a rapidly increasing scale

status of glacial lake columbia during the last floods from glacial lake missoula abstract the last floods from glacial lake missoula montana probably ran into glacial lake columbia in northeastern washington in or near lake columbia s sanpoil arm lake missoula floods dating from late in the fraser glaciation produced normally graded silt beds that become thinner upsection and which alternate with intervals of progressively fewer varves the highest three interflood intervals each contain only one or two varves and about 200 400 successive varves conformably overlie the highest flood bed this sequence suggests that jokulhlaup frequency progressively increased until lake missoula ended and that lake columbia outlasted lake missoula the upper grand coulee lake columbia s late fraser age outlet contains a section of 13 graded beds most of them sandy and separated by varves that may correlate with the highest missoula flood beds of the sanpoil river valley the upper grand coulee also contains probable correlatives of many of the approximately 200 400 succeeding varves as do nearby parts of the columbia river valley this collective evidence casts doubt on a prevailing hypothesis according to which one or more late fraser age floods from lake missoula descended the columbia river valley with little or no interference from lake columbia s okanogan lobe dam

the late wisconsinan deglacial history of the east central taseko lakes area british columbia late wisconsinan fraser glaciation retreat phase deposits and landforms in the east central taseko lakes area british columbia are used to demonstrate a four phase model of deglaciation during phase i at the onset of ice retreat the cordilleran ice sheet occupied much of the study area blocking southward drainage of fraser river phase ii was marked by the deglaciation of uplands and plateaux meltwater drainage patterns were controlled by stagnating glaciers confined to valleys phase iii commenced as remnant ice in the fraser valley downwasted to between 850 and 760 m elevation at this time interlobate glacial lakes formed in hanging valleys east of fraser river drainage of glacial lakes occurred subglacially and was accompanied by disintegration of remnant ice and an increase in mass movements in valleys these events were followed by decreased sedimentation rates reflecting lower meltwater volumes and exhaustion of unstable glacial debris during phase iv postglaciation valley fill was subj

pleistocene glacimarine sedimentation on the continental slope off vancouver island british columbia abstract cordilleran ice sheet activity has had a significant influence on glacimarine sediment transport and deposition on the western canadian continental slope resulting in distinct sediment facies here we present lithogenic sediment grain size distributions grains 250 m g 1 63 m 10 to 60 m and 2 to 4 m and mass accumulation rates mar from a marine core md02 2496 collected 50 km offshore of vancouver island british columbia the lithogenic fraction of sediment deposited on the slope increased as grain size decreased and sediment sorting increased at 30 ka when the cordilleran ice sheet grew into southern british columbia during the fraser glaciation as the ice sheet advanced onto the continental shelf near core md02 2496 between 19 and 17 ka the proximal ice margin dramatically increased lithogenic sediment mars glacimarine sedimentation at this time was associated with cyclic deposition of generally coarse poorly sorted sediment an 80 year cyclicity suggests the influence of 1 outburst floods 2 lunar or 3 solar cycles on tidewater outlet glacier discharge rapid ice sheet retreat at 17 ka is indicated by ice rafted debris ird deposition followed by the deposition of fine well sorted silt suggestive of iceberg discharge followed by rock flour in a meltwater plume lithogenic sediment mars decreased dramatically at the bolling with a brief return to coarse poorly sorted sediments during the younger dryas glacimarine sedimentation decreased by 10 ka as the cordilleran ice sheet extent diminished to the areal extent of modern ice fields

anoxia vs productivity what controls the formation of organic carbon rich sediments and sedimentary rocks discussion the prevailing explanation for the origin of organic rich sediments and rocks invokes deposition under conditions of anoxia however recent research suggests that high primary production and not water column anoxia provides the first order control on the accumulation of organic rich facies in the modern oceans oxygen minima do not appear to have any direct effect on carbon accumulation in continental margin or marginal sea environments sediments accumulating in the modern black sea the type euxinic basin are not particularly enriched in organic matter despite the presence of an anoxic water column although a sapropel containing extremely high carbon concentrations was deposited during the holocene at a time when the basin was oxic results of a recently published co pled ocean atmosphere model indicate that during the cretaceous thermohaline and surface circulation in the oceans was similar to or more intense than modern conditions despite the overall equable climate such conditions confound the idea that circulation in the cretaceous atlantic for example was punctuated by oceanic anoxic events brought about by more sluggish circulation sporadic temporal and spatial increases in primary production reflecting changes in the behavior and or state of the ocean atmosphere system constitute a more tenable explanation for the occurrence of modern and quaternary carbon rich sediments and cretaceous black shales consequently the fundamental control on the accumulation of carbon rich facies in the oceans and marginal seas is not the presence or absence of anoxia

early aptian algal bloom in a neritic proto north atlantic setting harbinger of global change related to oae 1a pervasive growth of microencrusters lithocodium bacinella characterizes short lived stratigraphic intervals in lower aptian shallow water carbonate platform settings of the central and southern tethys although a causal relationship between this peculiar shallow water facies and the early aptian oceanic anoxic event oae 1a seems likely the temporal and spatial distributions of lithocodium and bacinella mass occurrences in the rock record point to a rather complex pattern possible controls include various global and regional drivers expressed in environmental perturbation of neritic ecosystems microencruster blooms have hitherto been reported to occur at the onset and in the aftermath of oceanic anoxic event oae 1a slightly pre or postdating the deposition of dark organic rich black shales in pelagic basins this study presents evidence for a punctuated and well expressed early aptian bloom of the ulvophycean green algae lithocodium aggregatum observed at the proto north atlantic margin lusitanian basin portugal similar to southern and central tethyan sections a lithocodium dominated interval temporally replaces the rudist dominated platform ecosystem this lithocodium rich horizon is composed of oncoidal floatstones and boundstones including a well exposed biohermal level and reaches a thickness of up to 6 m high resolution carbon isotope stratigraphy shown here clearly argues for lithocodium to represent a biotic harbinger of environmental change in the run up of oae 1a chemostratigraphy provides evidence that the subsequent carbonate platform breakdown in the proto north atlantic was coeval with an early aptian carbonate platform drowning episode observed in the northern tethys prior to oae 1a a regionally enhanced nutrient level and a relative sea level rise are suggested to have triggered the transient mass occurrence of lithocodium microencrusters which also may have been influenced by elevated atmospheric co2 concentrations related to the emplacement of the ontong java large igneous province upwelling water masses and enhanced terrigenous runoff due to increased weathering may have served as possible sources of the required nutrients which tentatively diminished and finally interrupted the metazoan carbonate platform factory

the gang ranch big bar area south central british columbia stratigraphy geochronology and palynology of the tertiary beds and their relationship to the fraser fault tertiary rocks in the gang ranch big bar area south central british columbia consist of 1 early or middle eocene 50 ma lavas breccias and tuffs capped by a mappable unit of conglomerate a

advance and retreat glacigenic deformation at williams lake british columbia glacigenic deformation structures at williams lake british columbia occur within stratified quaternary sediments that both overlie and underlie lodgement till of the last fraser late wisconsinan glaciation the main structures in sediments below the lodgement till are faults joints and clastic dikes produced by glacier overriding during late wisconsinan time the orientation of these structures is closely related to the direction of glacier flow at williams lake their character and stratigraphic position suggest that the substrate in this area was partly frozen and partly unfrozen when covered by ice during the fraser glaciation a different suite of glacigenic deformation structures is found in sediments above the lodgement till these include complex folds load casts and high angle faults formed during deglaciation as a result of loss of ice support and collapse these structures yield information on the local pattern of ice decay but bear no relationship to the regional direction of late wis

late glacial lakes in the thompson basin british columbia paleogeography and evolution during the decay of the cordilleran ice sheet 10 000 13 000 bp glacial lakes developed within valleys that dissect the interior plateau of british columbia in this paper we 1 illustrate a procedure for assessing paleo water planes that has general application 2 document lake paleogeography and evolution in the thompson valley 3 provide new data on the glacio isostatic response of the central cordillera and 4 present new evidence of its late glacial environment we employ geomorphology and sedimentology digital elevation models and new technologies differential global positioning systems ground penetrating radar and geographic information systems to refine paleogeographic reconstructions of glacial lakes glacial lake thompson and glacial lake deadman were ribbon shaped width to length ratio 3 100 deep 140 to 50 m lakes that contained significant water volumes 84 24 km3 they lengthened to the west and their water level lowered as ice decayed final ice dam failure resulte

paleoceanographic changes during the early cretaceous valanginian hauterivian evidence from oxygen and carbon stable isotopes we investigated valanginian hauterivian bulk rock and belemnite samples from vocontian basin sections in southeastern france for their stable carbon and oxygen isotope signature firstly because these sections permit calibration with high resolution biostratigraphy based on ammonites and secondly because detailed isotope studies for the hauterivian are lacking the results show that 13c values for bulk rock decrease during the late valanginian early hauterivian with 1 and increase again during the late hauterivian with 1 the 18o signal for bulk rock samples is mostly disturbed by diagenesis the belemnites show carbon and oxygen isotope values that are lower and higher than bulk rock samples respectively we explain this as the result of the belemnites recording a deeper water signal with lighter 13c values and heavier 18o values implicating colder water at greater depth the overall preservation of the belemnites is very good and permits the construction of a paleo temperature trend this trend shows warm deeper water temperatures during the late early valanginian 15 c and progressively cooler temperatures during the late valanginian and early hauterivian 11 c during the late hauterivian temperatures increase again 13 c we relate this cooling trend for deeper water to a second order sea level rise which allowed for the exchange of cold boreal and warm tethyan water masses the influx of cold nutrient rich water had a profound effect on carbonate producing biota along the northern margin of the tethys during the hauterivian leading to prolonged phases of condensation and platform destruction during the early hauterivian the carbonate system along the northern tethyan margin shifted into a green water mode of carbonate production high rates of carbonate production under mesotrophic conditions also observed in other parts of the world meant that the global carbon cycle became buffered shown by the stable trends in carbon isotopes

upper cretaceous campanian phosphorites in jordan implications for the formation of a south tethyan phosphorite giant a record of sedimentary authigenic and biological processes are preserved within the upper cretaceous campanian alhisa phosphorite formation ap in central and northern jordan the ap formed near the eastern extremity of the south tethyan phosphorite province stpp a carbonate dominated upper cretaceous to eocene phosphorite giant that extends from colombia north africa to the middle east multidisciplinary research of the ap and associated cherts chalks and oyster buildups indicate that phosphatic strata formed on a highly productive storm dominated east west trending epeiric platform along the south tethyan margin the onset of phosphogenesis and the accumulation of economic phosphorite coincided with a rise in relative sea level that onlapped peritidal carbonates of the ajlun group pristine phosphates are associated with well developed micrite concretionary horizons and contain abundant non keeled spiral planktic foraminifera and a low diversity benthic assemblage of buliminacean foraminifera suggesting that pristine phosphates are a condensed facies and phosphogenesis was stimulated by the effects of a highly productive surface ocean and the suboxic diagenesis of sedimentary organic matter the bulk sediment composition and absence of fe bearing authigenic phases such as glauconite pyrite including pyrite molds siderite and goethite within pristine phosphates suggests that deposition and authigenesis occurred under conditions of detrital starvation and that iron pumping played a minimal role in phosphogenesis authigenic precipitation of phosphate occurred in a broad array of sedimentary environments herein termed a phosphorite nursery that spanned the entire platform this is a non uniformitarian phenomenon reflecting precipitation of sedimentary apatite across a wide depositional spectrum in a variety of depositional settings wherever the conditions were suitable for phosphogenesis sedimentologic data indicate that pristine phosphates were concentrated into phosphatic grainstones through storm wave winnowing and storm generated shelf parallel geostrophic currents economic phosphorites formed through the amalgamation of storm induced event beds stratigraphic packaging of phosphatic strata indicates that temporal variations in storm frequency were a prerequisite for the formation of economic phosphorite syndepositional phosphogenesis reworking and amalgamation to form phosphorites contrasts sharply with the principles of baturin cycling a transgressive systems tract coupled with high surface productivity created detritally starved settings favourable for phosphogenesis storm reworking of pristine

sedimentology and origin of deposits from a small ice dammed lake leirbreen norway this paper describes recent proglacial lacustrine sediments exposed by the drainage of a small probably never more than 0 03 km2 ice dammed lake basin at leirbreen central jotunheimen norway the dominant facies include ripple laminated massive and horizontally stratified sands massive and horizontally laminated silts and irregularly laminated fine sands and silts the major control on lake circulation and the nature and distribution of these facies was an underflow driven by a subglacial meltwater stream which formed the major lake input although much of the sedimentary sequence indicates a pulsatory input the proximal character of this small lake prevented the development of classic varved silts compressional deformation of shoreline sediments was due to winter lake ice push other deformational processes included the grounding of icebergs water escape and syn sedimentary downslope collapse observations from an adjacent small ice marginal lake at leirbreen provide support for several of the inferences drawn from the sediments of the former ice dammed lake

the quaternary stratigraphic record of british columbia evidence for episodic sedimentation and erosion controlled by glaciation the terrestrial quaternary stratigraphic record of british columbia is largely a product of brief depositional events separated by long periods of nondeposition and erosion thick stratified quaternary sediments are present mainly in valleys and coastal lowlands and accumulated during periods of growth and decay of the cordilleran ice sheet at glacial maxima till was deposited over large areas of low and moderate relief however at the same time much of the landscape was eroded by glaciers sedimentation has been more restricted and has occurred at lower rates during nonglacial periods than during glaciations on land the only important sediment accumulation sites during nonglacials have been lakes floodplains and fans however large amounts of sediment have accumulated offshore especially in fjords and basins such as the strait of georgia because of the restricted aspect of sedimentation during nonglacials the stratigraphic record of these periods is meagre in most places true nonglacial uni