geochemistry and provenance of the middle ordovician austin glen member normanskill formation and the taconian orogeny in new england the austin glen member of the upper middle ordovician normanskill formation is a sandstone shale ysch succession deposited in the foreland of the taconian orogen petrographic major and trace element and nd pb isotopic data provide substantial constraints on its provenance lack of k feldspar and paucity of plagioclase in addition to the dominance of sedimentary rock fragments indicate that the source was dominated by recycled sedimentary components major and trace element data support this conclusion and indicate that the provenance of both shales and sandstones was the same no evidence of an ophiolitic or volcanic component was observed interpretation of nd isotopic characteristics are complicated by a partial resetting of the nd isotope system at about the time of sedimentation but indicate that the provenance of the austin glen member had a long term history of light rare earth element lree enrichment average tdm 1a8 ga furthermore nd isotopic compositions are extremely homogeneous end 8a1 0a6 1 s d n 23 at 450 ma the approximate depositional age indicating either a single source or very well mixed sources 207pb 204pb ratios are variable but within the range of pb isotopic compositions typically described as grenvillian the range of 207pb 204pb is greater than expected for the range of 206pb 204pb and suggests an additional component of pb possibly introduced during diagenesis the immediate source of the austin glen member may have been the accretionary prism that developed as older sediments of the laurentian margin were scraped off the basin oor incorporated within the accretionary prism and shed into the basin no evidence indicating the arrival of an undifferentiated island arc or continental fragment during the taconian orogeny has been found the data acquired during this study can be explained almost exclusively by grenville province source components but with possible additional contributions from older laurentian terranes and late proterozoic rift volcanics that are not readily quanti ed but likely to have been minor accordingly we conclude that the taconian orogeny in new england involved either 1 a continental arc that involved exclusively laurentia 2 collision of a continental block with identical geochemical characteristics as laurentia or 3 essentially no detritus from any exotic colliding block island arc or continental fragment reached the foreland basin at the time of austin glen deposition

xrf based chemostratigraphy between and across two disconformities in the ordovician trenton group and utica shale of central new york u s a abstract thick mudstone successions contain a wealth of elemental proxy information than can be readily accessed by hand held x ray fluorescence xrf spectroscopy mudstones of the upper ordovician trenton group and utica shale record drowning of a carbonate shelf in a peripheral foreland basin during the taconic orogeny two discrete episodes of shelf erosion the thruway and honey hill disconformities followed by deepening occurred during this period xrf based bulk rock elemental data coupled with detailed lithologic descriptions and xrd analysis highlight previously unidentified changes in the composition of siliciclastic detritus across these disconformities this likely relates to variation in the relative contribution of sediment derived from the cratonic interior eroded carbonate shelf and rising orogenic wedge as well as possible exhumation of the adirondack massif the data also indicate that mudstones of the lower indian castle shale the interval of the utica shale deposited between the thruway and honey hill disconformities are more carbonate rich than the underlying mudstones of the trenton group this is surprising given the large volume of limestone in the trenton group and attests to the considerable amount of intrabasinal carbonate winnowed from the shelf during formation of the thruway disconformity drowning following erosion along the honey hill disconformity diminished this sediment source and led to a significant reduction in the amount of carbonate mudstone present in the upper indian castle shale the concentrations of redox sensitive trace elements normalized to al increase sharply across the thruway disconformity suggesting increased bottom water anoxia and organic matter preservation in a deepening basin increases in the s and fe concentrations above the honey hill disconformity suggest a shift to even more strongly reducing conditions results of this study are consistent with previous interpretations indicating that higher resolution xrf based elemental concentration data may reveal more cryptic changes in sediment provenance and bottom water redox conditions in the taconic foreland basin and in other thick mudstone successions

absolute calibration of the greenland time scale implications for antarctic time scales and for δ14c abstract we propose a new age scale for the two ice cores grip and gisp2 that were drilled at greenland summit based on accelerator mass spectrometry 14c dating of foraminifera in core md95 2042 paleoceanography 15 2000 565 calibrated by means of recently obtained paired 14c and 230th measurements on pristine corals marine radiocarbon calibration curve spanning 10 500 to 50 000 years bp thousand years before present based on paired 230th 234u 238u and 14c dates on pristine corals geological society of america bulletin 2003 submitted for publication the record of core md95 2042 can be correlated very precisely to the greenland ice cores between 30 and 40 ka bp our scale is 1 4 ka older than the grip ss09sea time scale journal of quaternary science 16 2001 299 at the older end of marine isotope stage 3 we use published 230th dates from speleothems to calibrate the record using this scale we show a 14c record that is broadly consistent with the modelled record earth planet sci lett 200 2002 177 and with the data of hughen et al science 303 2004 202 but not consistent with the high values obtained by beck et al science 292 2001 2453 or by voelker et al radiocarbon 40 1998 517 we show how a set of age scales for the antarctic ice cores can be derived that are both fully consistent with the greenland scale and glaciologically reasonable

patterns of deglacial warming in the pacific ocean a review with emphasis on the time interval of heinrich event 1 abstract based on a compilation of currently available records of past sea surface temperature sst variability estimated from a variety of different proxies the regional scale deglacial sst development in the pacific ocean is tentatively classified into four endmember types the subtropical and tropical pacific is characterized by a continuous deglacial warming without marked interruption during the time interval of heinrich event 1 h1 whereas the subarctic north pacific exhibits centennial scale warm cold oscillations during this time interval sst records from marginal seas of the pacific show a deglacial warming interrupted by a cooling event coeval with h1 followed by a marked bolling sst increase a single sst record from the southwestern subantarctic pacific displays a continuous deglacial warming across h1 followed by an antarctic cold reversal type cooling during the allerod thus in contrast to the deglacial sst development in the atlantic which has been inferred to be overwhelmingly driven by the redistribution of heat through changes in the meridional overturning circulation moc none of the open oceanic pacific sst records reviewed here displays any obvious and or dominant response to the reduction of the moc and or the reorganization of atmospheric circulation during h1 within the limits of absolute chronologies all tropical and subtropical pacific sst records show an onset of deglacial warming at 19 1 ka coeval with the onset of the deglacial rise in sea level

freshwater impacts recorded in tetraunsaturated alkenones and alkenone sea surface temperatures from the okhotsk sea across millennial scale cycles 1 we present records of phytoplankton produced alkenones down a long piston core which reveal changes of sea surface temperature sst and sea surface salinity sss in the southwestern okhotsk sea over the past 120 ka between 20 and 60 ka b p alkenone derived temperatures typically increased by 6 c 8 c from periods corresponding within a few hundred years to stadials to those corresponding to interstadials recorded in greenland ice cores the abundance of c37 4 alkenone relative to total c37 alkenones percent c37 4 a possible proxy for salinity indicated that during most low sss was associated with high sst the warm freshwater events might be related to 1 a decline in the supply of saline water entering the okhotsk sea through the soya strait 2 strengthening of the freshwater supply from the amur river and precipitation over the okhotsk sea associated mainly with increased asian summer monsoon activity and 3 the effect of melting sea ice these findings increase our understanding of the close linkage between high and low latitudes in relation to climate change and the synchronicity of climate changes within a few centuries between the pacific and the atlantic sides of the northern hemisphere

oceanographic aspects of the emperor seamounts region effects of the emperor seamount chain on the thermohaline structure and baroclinic flow are investigated on the basis of historical hydrographi data the amplitudes of dynamic height perturbations are 3 to 5 times larger west than east of the chain the intensity of the thermal fronts is stronger west than east of the seamounts near the crest of the southern seamounts strong east west thermohaline fronts and a strong northward baroclinic flow are observed the kuroshio extension west of the seamount chain is a well defined meandering current the axis of which generally lies between 33 and 36 n the available data indicate that the kuroshio extension turns northward and then flows eastward through the gaps of the seamount chain east of the seamounts the kuroshio extension widens threefold and appears to be poorly defined

ophiolite obduction pulses as a proxy indicator of superplume events abstract a major new synthesis of ophiolite geochronology and map of global phanerozoic distribution indicates that previously noted pulses of ophiolite obduction can be linked to superplume related tectonism a marked cyclicity is evident in obduction ages obtained from minerals in ophiolite metamorphic soles and obduction related minor intrusions this episodicity is in phase with periods of predominantly uniform polarity of the geomagnetic field formation of massive carbon rich deposits sea level highstands and formation of large flood basalt provinces all generally considered to be superplume proxy indicators a key to interpreting ophiolite obduction as a further proxy is the mid cretaceous superplume associated ocean margin compressional deformation during this event thermal rejuvenation and increased buoyancy of ocean lithosphere caused arc terrane collision marginal basin shoaling back arc basin closure and ophiolite obduction convergent margins were placed in compression with increased coupling between subducting and overriding plates resulting in major ocean margin deformation being directly datable and tectonically and petrologically distinctive makes ophiolite assemblages of considerable use for identifying superplume events

beyond beecher s trilobite bed widespread pyritization of soft tissues in the late ordovician taconic foreland basin pyritization of soft tissues is extremely rare pyritized fossils have been discovered at six new localities spanning 54 km of outcrop of the ordovician lorraine group of new york state suggesting that soft tissue pyritization is widespread in the taconic basin notable new taxa with soft tissue preservation include ostracods and other arthropods such fossils are rare and occur within 4 9 cm thick mudstones representing single rapid depositional events high ratios of reactive iron to total iron and high values of 34 s together with a near absence of disarticulated and fragmented skeletal material suggest that organisms in these pyritic horizons were buried rapidly and underwent bacterial sulfate reduction in porewaters rich in highly reactive iron and low in organic carbon these conditions facilitated iron sulfi de precipitation within and on decaying carcasses such conditions occur repeatedly in some fi ne grained distal turbiditic facies of the taconic foreland basin pyritized soft bodied fossils await discovery elsewhere in the lorraine group

snake hill reconstructing eastern taconic foreland basin litho and biofacies from a giant melange block in eastern new york usa abstract exotic lithofacies and faunas have long been known from snake hill eastern new york usa the faunally diverse sandstone dominated upper ordovician succession at snake hill sharply contrasts with surrounding tectonized sparsely fossiliferous distal shale re examination of the snake hill section shows that it is a storm and wave dominated near shore facies with a benthic fauna analogous to that of the younger lorraine group ashgillian of central new york and to that of the upper martinsburg group upper caradocian of eastern pennsylvania orthograptus ruedemanni chron graptolites indicate that the snake hill succession is older than the surrounding tectonized deep water shale climacograptus spiniferous chron snake hill is best interpreted as a parautochthonous block in melange originally deposited close to the shoreline of the emergent taconic accretionary prism because the snake hill succession is sandstone dominated it is inappropriate to refer mudstone dominated facies that underlie the western margin of the taconic allochthon in the hudson river valley region to the snake hill shale as has been done in the past the thick ca 150 m lithologically distinct succession at snake hill is therefore referred to as the snake hill formation the snake hill formation is the only known example of proximal near shore facies deposited on the western side of the outer taconic arc and represents easternmost deposition in the taconic foreland basin the snake hill formation is a unique occurrence and thus is restricted to its type locality at snake hill new york

northward and southward migrations of frontal zones during the past 40 kyr in the kuroshio oyashio transition area 1 the variation of sea surface temperature sst in the kuroshio oyashio transition area and the okhotsk sea during the last 40 kyr was estimated using long chain unsaturated alkyl ketones alkenones the temperature difference between the present and the last glacial period was about 5 6 c in the kuroshio oyashio transition area slightly larger than the 4 c previously reported moreover alkenones were not detected before 18 kyr b p in or near the okhotsk sea perhaps because of nearly year round sea ice expansion which would have prevented the growth of alkenone producers or because alkenones were less well preserved in surface sediments during the glacial period the northward and southward migrations of frontal zones were evaluated using differences in alkenone temperatures between stations located in the vicinity of the subarctic front saf subarctic boundary sab and kuroshio bifurcation front kbf all three frontal zones migrated southward during the glacial period compared with their present positions and their relative positions were different between the holocene and glacial periods in particular the distance between the saf and the sab was reduced during the glacial period compared with at present the northward and southward migration of the frontal zones may relate to both mid to low atmospheric circulation and polar atmospheric circulation

a novel proxy for terrestrial organic matter in sediments based on branched and isoprenoid tetraether lipids we propose a novel tracer for terrestrial organic carbon in sediments based on the analysis of tetraether lipids using high performance liquid chromatography mass spectrometry hplc ms analysis of terrestrial soil and peats shows that branched tetraether lipids are predominant in terrestrial environments in contrast to crenarchaeol the characteristic membrane lipid of non thermophilic crenarchaeota which is especially abundant in the marine and lacustrine environment based on these findings an index was developed the so called branched and isoprenoid tetraether bit index based on the relative abundance of terrestrially derived tetraether lipids versus crenarchaeol this bit index was applied to surface sediments from the angola basin where it was shown to trace the outflow of the congo river furthermore analyses of particulate organic matter from the north sea showed relatively higher bit indices in water column particulate organic matter near large river inputs a survey of globally distributed marine and lacustrine surface sediments shows that the bit index in these environments correlates with the relative fluvial input of terrestrial organic material making this index generally applicable the new proxy allows the rapid assessment of the fluvial input of terrestrial organic material in immature sediments up to 100 ma old

mid depth circulation in the northwest pacific during the last deglaciation evidence from foraminiferal radiocarbon ages 1 sediment cores mr01 k03 pc4 pc5 1366 m water depth collected from off northern japan were studied using coexisting planktonic and benthic foraminiferal radiocarbon measurements to reconstruct the history of mid depth circulation in the northwest pacific reconstructed ventilation ages indicate that consistent with data from a previous radiocarbon study at a shallower site there was significant variation in mid depth circulation during the last deglaciation especially in the bolling allerod 13 15 ka and younger dryas 11 5 13 ka intervals our record indicates that the ventilation changes in the north pacific were antiphase to those of the north atlantic suggesting that atmospheric moisture transport associated with the asian monsoon might have played a great role in millennium scale ventilation changes in the north pacific during the last deglaciation

high resolution uk 37 temperature reconstructions in the south china sea over the past 220 kyr past sea surface temperatures sst in the northern and southern areas of the south china sea have been reconstructed for the past 220 kyr using the uk37 alkenone index the sst profiles follow the glacial interglacial pattern exhibiting differences between last glacial maximum and holocene that are 1 3 c larger than those observed at the same latitudes in the atlantic and pacific oceans in termination i both planktonic foraminiferal 18o and sst exhibit well defined bolling allerod and younger dryas events with temperature differences between both periods of 0 8 and 0 4 c in north and south respectively ssts record a constant north south difference of 1 c in the interglacials and nearly 2 5 c in the glacial stages these differences define two distinct climatic and water circulation patterns that correspond with glacial interglacial sea level oscillations which opened and closed water exchange with the tropical indo pacific ocean through the present sunda shelf

the late ordovician dawson point formation timiskaming outlier ontario key to a new regional synthesis of richmondian hirnantian carbonate and siliciclastic magnafacies across the central canadian craton current paleogeographic reconstructions extend late ordovician taconic derived siliciclastics across the cen tral canadian craton prior to the terminal ordovician glacioeustatic lowstand revision of the late ordovician dawson point formation of the timiskaming outlier greatly reduces the distribution of these siliciclastics and documents a greater spread of shallow water carbonate of richmondian age as revised the dawson point formation contains two informal members a deep water graptolitic shale that grades upward into shallow water siliciclastic redbeds and an up per member of shallow water muddy crinoidal limestone with interbedded shale likely representing low energy shoals on a muddy shelf deep water shale accumulation began in the upper manitoulinensis graptolite zone following foun dering of the regional foreland carbonate platform basin development documents a northward younging 1 million years from southern ontario foreland basins in keeping with regional tectonic driven transgression along eastern north america the shale to carbonate succession of the dawson point formation correlates with the georgian bay forma tion on manitoulin island wherein the upper carbonate dominated divisions of both formations are equivalent to the siliciclastic queenston formation of southern ontario in absence of additional biostratigraphic information the upper member of the dawson point formation is likely richmondian or late ashgillian in age the revised late ordovician history of the timiskaming outlier may identify a once significant volume of shallow water carbonate across the central canadian craton with related sequestration of carbon dioxide possibly aiding global cooling erosion of the carbonate driven by developing glacioeustatic lowstand conditions was likely contemporaneous with early hirnantian peritidal de position of the uppermost queenston formation in southern ontario

episodicity of mesozoic terrane accretion along the pacific margin of gondwana implications for superplume plate interactions a review of evidence for deformation and terrane accretion on the late triassic early jurassic margins of pangea and the mid cretaceous margins of the palaeo pacific ocean shows that deformation was global and synchronous with probable superplume events late triassic early jurassic deformation appears to be concentrated in the period 202 197 ma and was coeval with eruption of the central atlantic magmatic province onset of pangaea break up a period of extended normal magnetic polarity and a major mass extinction event all possible expressions of a superplume event mid cretaceous deformation occurred in two brief periods the first from approximately 116 to 110 ma in the west palaeo pacific and the second from roughly 105 to 99 ma in the east palaeo pacific with both events possibly represented in northeast siberia this deformation was coeval with eruption of major oceanic plateaus core complex formation and rifting of new zealand from gondwana the cretaceous normal polarity epoch and a major radiation of flowering plants and several animal groups all linked with the mid cretaceous superplume event a simple unifying mechanism is presented suggesting that large continental or oceanic plates when impacted by a superplume tend to break up reorganize associated with gravitational spreading away from a broad thermally generated topographic high and with a resulting short lived pulse of plate marginal deformation and terrane accretion

a salinity related occurrence of a novel alkenone and alkenoate in late pleistocene sediments from the japan sea abstract the novel alkenoate ethyl tetratriacontadienoate c34 2ee has been found in late quaternary sediments of the japan sea by using gas chromatography mass spectrometry gc ms it accompanied hexatriacontadien 3 one c36 2ek previously found in black sea sediments a linear relationship between c36 2ek and c34 2ee concentrations points to both compounds being derived from the same source most likely a specific haptophyte the relative abundance of c34 2ee in total alkenones and alkenoates was significantly higher during the last glacial maximum when the 18o in planktonic foraminifera was anomalously light strongly suggesting that c34 2ee is associated with low salinity environments as samples with abundant c34 2ee also possessed anomalously high u 37 k values low salinity may have an ecological or physiological influence on both the unsaturation and carbon chain length of alkenones and alkenoates

the thermal history of the new york basement determined from 40ar 39ar k feldspar studies constraints on the thermochronologic evolution of the new york crystalline basement are mainly restricted to the high temperature early cooling history following 1 1 ga grenville metamorphism u pb methods and the late cooling history fission track methods the thermal history for the one billion years between these intervals is herein assessed using 40ar 39ar hornblende muscovite biotite and k feldspar thermochronology hornblende preferred ages suggest cooling below 450 500 c between ca 900 and 950 ma total gas ages of biotites range from 746 1060 ma and their age spectra complexity is probably related to younger thermal events and or excess argon a single muscovite analysis yields a preferred age of 854 ma argon isotope analyses of k feldspar provide a quantitative evaluation of the thermal history between 175 and 350 c multi diffusion domain thermochronology on highly variable k feldspar results yield internally consistent thermal histories and along with geologic constraints suggest thermal maxima of 275 350 c at ca 700 470 450 and 300 ma combining all of the k feldspar analyses provides an internally consistent thermal history for the region and allows for the following inferences reheating at 700 ma associated with late precambrian rifting during the formation of the iapetus ocean apparently affected the entire adirondack region with the highest temperatures occurring in the eastern part of new york local reheating in the ordovician is inferred to have affected the eastern adirondack mountains and probably resulted from the combined effects of burial during the early paleozoic emplacement of taconic thrust sheets and migration of hot fluids along normal faults during the taconic orogeny high paleotemperatures for the devonian section of eastern new york are related to maximum burial of the basement during the carboniferous at ca 300 ma

numerical experiments on the movement of a warm core ring with the bottom slope of a western boundary numerical experiments are performed to investigate the effects of the bottom slope of a western boundary on realistic warm core rings using a primitive equation sigma coordinate model warm core rings which initially have baroclinic velocity near a steep bottom slope gradually move northward but those with barotropic velocity do not barotropic velocity on the slope immediately disperses as a topographic rossby wave while baroclinic velocity is retained since the northward movement is caused by an effect very much like the image effect which is originally the effect of a free slip wall the authors term this effect the equivalent image effect the equivalent image effect increases as a slope becomes steeper and bottom friction becomes weaker and vice versa it seems that a steep slope acts like a wall and the bottom friction of a steep slope corresponds to the lateral viscous effect of a wall however the effect of a slope on a warm core ring is different from that of a wall in that ring slope interactions take place at the lower part of the ring because the velocity of a warm core ring is weak in deep layers ring slope interactions are moderate and the leakage of the interior fluid of a ring seen in ring wall interactions is not apparent while the viscous effect is weaker than that of a no slip wall as well these results are applied to the northward movement of kuroshio warm core rings and to warm eddies in the gulf of mexico

deepwater formation in the north pacific during the last glacial termination between approximately 17 500 and 15 000 years ago the atlantic meridional overturning circulation weakened substantially in response to meltwater discharges from disintegrating northern hemispheric glacial ice sheets the global effects of this reorganization of poleward heat flow in the north atlantic extended to antarctica and the north pacific here we present evidence from north pacific paleo surface proxy data a compilation of marine radiocarbon age ventilation records and global climate model simulations to suggest that during the early stages of the last glacial termination deep water extending to a depth of approximately 2500 to 3000 meters was formed in the north pacific a switch of deepwater formation between the north atlantic and the north pacific played a key role in regulating poleward oceanic heat transport during the last glacial termination

late ordovician chatfieldian catastrophic volcanism and abrupt carbonate platform interior subsidence a tectonic link across a taconian foreland basin quebec embayment due to inherited crustal weakness the late ordovician trenton group of new york state and equivalent strata in south central canada peripheral to the quebec embayment form a regional carbonate platform succession within the taconian foreland basin the upper and lower group boundaries record geodynamically controlled changes in regional subsidence whereas a higher order allocyclic stratigraphy traced south along the foreland interior of the eastern united states may identify shorter term eustatic controls a tectonomagmatic event extending across the foreland basin is recorded a few million years prior to the regional collapse of the foreland platform in the quebec embayment within the lower c spiniferus graptolite zone platform margin retreat 50 km in southern quebec is contemporaneous with a shale rich limestone succession that thins 30 10 m westward over 300 km into the ottawa embayment eastern ontario west of the appalachian structural front this stratigraphic record coincides with catastrophic volcanism within the once distant volcanic arc terranes as recorded by a bentonite traced geophysically from the platform margin to the michigan basin core from the ottawa embayment demonstrates western directed transport of lithic bearing ash the lithic material representing reworked deep water sedimentary and or volcaniclastic sediment was entrained by eruption of calc alkaline felsic to basaltic andesitic and trachyandesitic magmatic sources the above geological history documents a short period of diminishing influence of subsidence moving into the platform interior an event that enhanced briefly cross platform oceanographic circulation as recorded by elevated shale abundance and change in macrofaunal assemblages short lived differential subsidence of the continental crust in this region in response to distal tectonism may have been predicated by inherited weakness of a shallowly buried intracratonic 400km precambrian fault system manifest today by the ottawa bonnechere graben the resulting thin 10 to 30 m stratigraphic record of the tectonomagmatic event is of similar thickness to high order allostratigraphic patterns within the taconic foreland interior of the eastern united states because there is a heterogeneous distribution of precambrian fault systems underlying the taconian foreland interior of eastern laurentia differential structural response of the foreland interior can be anticipated the apparent regional allostratigraphy may contain subtle facies differences along the strike of the foreland basin that reflect this tectonic component

paleoredox and pyritization of soft bodied fossils in the ordovician frankfort shale of new york multiple beds in the frankfort shale upper ordovician new york state including the original beecher s trilobite bed yield fossils with pyritized soft tissues a bed by bed geochemical and sedimentological analysis was carried out to test previous models of soft tissue pyritization by investigating environmental depositional and diagenetic conditions in beds with and without soft tissue preservation highly reactive iron fehr total iron fet 34s organic carbon and redox sensitive trace elements were measured in particular the partitioning of highly reactive iron between iron carbonates fe carb iron oxides fe ox magnetite fe mag and pyrite fep was examined overall the multi proxy sedimentary geochemical data suggest that the succession containing pyritized trilobite beds was deposited under a dysoxic water column in agreement with the paleontological data the data do not exclude brief episodes of water column anoxia characterized by a ferruginous rather than an euxinic state however the highest fehr fet values and redox sensitive trace element enrichments occur in siltstone portions of turbidite beds and in concretions suggesting that subsequent diagenesis had a significant effect on the distribution of redox sensitive elements in this succession moderately high fehr fet and fep fehr low organic carbon enriched 34s and the frequent presence of iron rich carbonate concretions in beds with soft tissue preservation confirm that pyritization was favored where porewaters were iron dominated in sediments relatively poor in organic carbon less

variability of the path of the kuroshio ocean current over the past 25 000 years the kuroshio current is the strong northwestern component of the subtropical north pacific ocean gyre and advects a large amount of heat from the tropics to northern mid latitudes the kuroshio has bimodal stationary flow patterns with small and large meander paths east of central japan1 2 which switch on annual and decadal timescales3 4 these switches seem to be caused by changes in current velocity and volume transport of the north equatorial current that are associated with variations in the trade wind intensity in the eastern equatorial north pacific ocean5 6 here we present alkenone derived sea surface temperature records at multicentennial resolution from sediment cores from the nishishichitou ridge off central japan these 25 000 year records show that the kuroshio path has also fluctuated on millennial timescales this variability resembles that of the subtropical high pressure of the north pacific reconstructed from terrestrial pollen distributions water levels in north american lakes and marine micropalaeontological records7 together these data indicate that climate variability off central japan over the past 25 000 years may be part of a circum pacific phenomenon reflecting the rate of subtropical surface circulation in the north pacific ocean

characteristics of alkenones synthesized by a bloom of emiliania huxleyi in the bering sea abstract we investigated the characteristics of the alkenones produced by a bloom of emiliania huxleyi in the eastern bering sea in 2000 alkenones were detected in surface waters between 57 n and 63 n where phosphate concentrations were low and the ammonium nitrate ratio was high the total alkenone content c37 2 c37 3 and c37 4 ranged from 22 0 to 349 g g 1 in suspended particles and from 0 109 to 1 42 g g 1 in surface sediments this suggests that a large proportion of the particulate alkenones synthesized in the surface water rapidly degraded within the water column and or at the water sediment interface of the bering shelf the change in the stable carbon isotopic composition 13c of c37 3 alkenone could not be explained only by variation in co2 aq in the surface water but also depended on the growth rate of e huxleyi the alkenone unsaturation index uk 37 was converted into an alkenone temperature with three equations prahl et al 1988 sikes et al 1997 muller et al 1998 sikes et al s 1997 equation gave the best correlation with the observed sea surface temperature sst in the eastern bering sea however some temperatures estimated by sikes et al s 1997 equation from the uk 37 varied from the observed sst possibly because of the rapidly changing rate of alkenone synthesis in the logarithmic growth stage or the low rate of alkenone synthesis when nutrients were limiting temperatures estimated from uk 37 in the surface sediments 6 8 8 2 c matched the observed sst in september 7 8 c but differed from the annual average sst of 4 to 5 c suggesting that most of the alkenone in the eastern bering sea was synthesized during limited periods for instance in september the relative amounts of c37 4 alkenone as proportions of the total alkenones referred to as c37 4 were high ranging from 18 3 to 41 4 low salinity water

variations of current path velocity and volume transport of the kuroshio in relation with the large meander abstract the variations of the kuroshio current path and their relations with current velocity volume transport and upstream position of the kuroshio are examined using sea level data after the long time non large meander nlm path during 1963 75 the kuroshio takes a large meander lm path during most of 1975 91 1975 80 1981 84 1986 88 and 1989 91 the study of these meanders confirms the description of the path of the kuroshio based on the three typical paths and the transitions between them with an exception being the 1981 84 lm path the formation and decay of the large meander are associated with velocity and position of the kuroshio in the tokara strait south of kyushu a small meander precursor of the large meander seems to be formed southeast of kyushu in relation with a temporary increase of kuroshio velocity and a northward shift of the kuroshio in the tokara strait an eastward propagation of the small meander leading to the lm formation is associated with remaining in the northe

intermediate water ventilation change in the subarctic northwest pacific during the last deglaciation 1 the laminated sediments suggest significant depletion in dissolved oxygen of intermediate water in the north pacific during the last deglaciation however the cause of depleted oxygen during deglaciation is still a matter of debate here we present foraminiferal mg ca based intermediate and surface temperatures and 18o of seawater 18ow a proxy of salinity in the oyashio region in order to investigate intermediate water circulation through the last deglaciation results indicate that the intermediate water temperature and 18ow increased in association with ventilation age at the bolling allerod period suggesting that the poor ventilation at that time the surface record shows that the decrease of salinity preceded the slowdown of intermediate ventilation the coupled variation of intermediate and surface water suggests that the supply of cold fresh intermediate water diminished because of poor ventilation at the high latitude due to surface freshening

testing symbiotic morphology in trilobites under dysoxic and oxic conditions from cambrian to early ordovician lagerstatten dysoxic conditions were prevalent in cambrian and early ordovician oceans adaptations of trilobites to these conditions yield insight into the selective forces driving their evolution and the potential for modern arthropods to adapt to anthropogenically driven dysoxia in the early paleozoic olenid trilobites may have adapted to dysoxia through olenimorphy special morphologic adaptations facilitating symbiosis with sulfur oxidizing bacteria olenimorphy s link to symbiosis has never been tested and might instead be related to phylogeny here we tested whether olenimorphy occurs predominately in dysoxic environments as expected or whether it occurs within certain trilobite groups regardless of environment trilobites were selected from nine fossil lagerstatten representing the early to middle cambrian prior to olenid evolution and the middle cambrian early ordovician alum shale with olenids putative exemplars of symbiosis trilobite morphology was scored as ranked characters and reduced via non metric multidimensional scaling nmds to a single metric describing suitability for symbiosis results indicated that olenimorphy was significantly related to phylogeny and not environment in the early to middle cambrian dysoxic corynexochids and oxic redlichiids were equally unsuitable for symbiosis while ptychopariids from both oxic and dysoxic conditions were equally well suited for symbiosis in the alum shale asaphids and ptychopariids from both oxic and dysoxic conditions were equally well suited for symbiosis and redlichiids from oxic conditions were poorly suited olenids were not the best suited trilobites within their data set nor even within their order secular trends in thoracic segmentation did not bias our results trilobite hard parts do not appear to provide evidence for symbiosis which is consistent with modern arthropods that have few morphological adaptations for dysoxic conditions in fact arthropods are rare in persistently dysoxic conditions raising concerns about the spread of anthropogenically triggered benthic dysoxia in the future particularly given the extinction of trilobites under similar conditions at the end of the permian

reconstructing late ordovician carbon cycle variations abstract the role of carbon dioxide in regulating climate during the early paleozoic when severe glaciations occurred during a putative greenhouse world remains unclear here we present the first molecular carbon isotope proxy based estimates for late ordovician early katian pco2 levels and explore the limitations of applying this approach to the reconstruction of paleozoic pco2 carbon isotope profiles from three sites in laurentia iowa ontario and pennsylvania and one site in baltica estonia exhibit overall low isotope fractionation between organic and inorganic carbon during photosynthesis ep and these values declined during the early katian carbonate carbon isotope excursion or guttenberg carbon isotope excursion gice algal ep values are sensitive to changes in co2 concentrations algae cell morphologies and cell growth rates to constrain these factors we present molecular evidence that a decrease in the relative abundance of cyanobacteria and a change in the eukaryotic algae community co occurred with the gice regardless of local biotic or oceanographic influences a decline in ep values indicates photosynthesis was sensitive to carbon concentrations and via analogy with modern taxa constrains pco2 to below 8 pre industrial levels pil or about half of previous estimates in addition the global positive carbon isotope excursions expressed in a wide variety of sedimentary materials carbonate bulk organic matter n alkanes acyclic and cyclic isoprenoid hydrocarbons provide compelling evidence for perturbation of the global carbon cycle and this was likely associated with a decrease in pco2 approximately 10 million years prior to the hirnantian glaciations isotopic records from deeper water settings suggest a complex interplay of carbon sources and sinks with pco2 increasing prior to and during the early stages of the gice and then decreasing when organic carbon burial outpaced increased volcanic inputs

decadal variability of the north pacific polar front subsurface warming versus surface cooling 1 over 200 hydrographic sections are used to trace the polar front defined as the southern boundary of the pure subarctic stratification with a pronounced extremely cold subsurface temperature minimum underlain by a temperature maximum the front extends from 40 n off japan to 57 n in the gulf of alaska where it retroflects and continues wsw with the alaskan stream the front s decadal variability from 1977 1999 is examined along 150 e 170 e 175 5 e and 180 e at these longitudes the front is relatively stable except for 170 e where it shifts north south by 400 km every 6 years most time series reveal a subsurface warming of 1 c per decade and a surface cooling of the front since the subsurface temperature minimum is a remnant of winter convection the subsurface warming signals an amelioration of the winter climate whereas the summer climate becomes colder

comparative sequence stratigraphy of two classic upper ordovician successions trenton shelf new york ontario and lexington platform kentucky ohio implications for eustasy and local tectonism in eastern laurentia abstract comparison of the classic upper ordovician mohawkian to lower cincinnatian caradoc to lower ashgill black river and trenton groups in new york state southern ontario with the tyrone lexington formations exposed in the jessamine dome southern cincinnati arch in north central kentucky and southern ohio reveals striking similarities previous emphasis on complex local facies mosaic has obscured widespread regional patterns biostratigraphy and k bentonites provide broad constraints on inter regional correlations however an allostratigraphic approach permits higher resolution correlations and a partial test of eustatic vs strictly local tectonic models to explain stratigraphic patterns upper mohawkian to lower cincinnatian 455 449 ma depositional sequences previously recognized for the jessamine dome and nashville dome areas are correlated between the two main study areas and further refined chatfieldian rocklandian to shermanian or cobourgian of traditional terminology sequences m5 and m6 of previous workers are interpreted to be composite sequences and are each subdivided into three smaller scale sequences which also have counterparts in the new york ontario strata in turn these correlations indicate at least partial allocyclic control on sedimentary cycles complex lateral variations within depositional sequences especially in the late shermanian to edenian indicate that tectonically controlled patterns of basinal subsidence and uplift of crustal blocks perhaps reflecting forebulge migration exerted a strong influence on the local facies and motif of depositional sequences these tectonic features however did not obliterate the underlying allocyclic pattern indeed high resolution sequence stratigraphy enables detailed resolution of shifting patterns of minor uplift and subsidence

distribution and modification of north pacific intermediate water in the kuroshio oyashio interfrontal zone abstract a multiship ctd survey was conducted in the kuroshio oyash interfrontal zone in the area of 30 41 n 140 e 180 from may to june 1992 to examine the distribution modification process and formation site of north pacific intermediate water npiw low salinity oyashio water and high salinity kuroshio water merge along the kuroshio extension just off the east coast of japan and together flow eastward eastward geostrophic transport and salinity across the kuroshio strong current indicate that the mixture of the kuroshio and oyashia waters along the kuroshio extension can produce new npiw transport estimate suggests that the new npiw bifurcates into the interfrontal zone and into the recirculation of the subtropical gyre a salinity minimum structure can he also created due to the isopycnal mixing along the kuroshio extension between the oyashio and kuroshio waters which have different salinity and vertical velocity structures the low salinity oyashio water seen along the oyashio branches and t

north pacific climate response to freshwater forcing in the subarctic north atlantic oceanic and atmospheric pathways abstract sudden changes of the atlantic meridional overturning circulation amoc are believed to have caused large abrupt climate changes over many parts of the globe during the last glacial and deglacial period this study investigates the mechanisms by which a large freshwater input to the subarctic north atlantic and an attendant rapid weakening of the amoc influence north pacific climate by analyzing four different ocean atmosphere coupled general circulation models gcms under present day or preindustrial boundary conditions when the coupled gcms are forced with a 1 sv sv 106 m3 s 1 freshwater flux anomaly in the subarctic north atlantic the amoc nearly shuts down and the north atlantic cools significantly the south atlantic warms slightly shifting the atlantic intertropical convergence zone southward in addition to this atlantic ocean atmosphere response all of the models exhibit cooling of the north pacific especially along the oceanic frontal zone consistent with paleoclimate recons

paleozoic oil source rock correlations in the tarim basin nw china we studied a suite of 40 oils and extracts of purported source rocks from the tarim basin in nw china the main group of oils comes from tazhong and tabei wells which sample the largest known petroleum accumulations in the basin these oils can be statistically correlated with extracts of ordovician rocks based upon high relative concentrations of 24 isopropylcholestanes and low relative concentrations of dinosteranes triaromatic dinosteroids and 24 norcholestanes in contrast extracts from cambrian rocks have low relative concentrations of 24 isopropylcholestanes with high relative concentrations of dinosteranes triaromatic dinosteroids and 24 norcholestanes although some tarim basin cambrian rocks yield high total organic carbon contents we see little evidence in the analyzed oil samples to suggest that they came from cambrian source rocks

late ordovician platform foundering its paleoceanography and burial as preserved in separate eastern michigan basin ottawa embayment basins southern ontario comparison of litho bio and chemostratigraphy in two cores from the northeastern margin of the michigan basin manitoulin island and from within the ottawa embayment eastern ontario identifies interbasinal differences of late ordovician platform foundering linked to taconic orogenesis graptolite biostratigraphy defines an east to west younging late edenian to early maysvillian of platform burial a regional unconformity likely caps the platform succession in both basins an increased supply of mafic material appears during the final stages of platform collapse with the accumulation of organic rich 8 petroliferous shales collingwood member michigan basin eastview member ottawa embayment both units preserve evidence for deposition coincident with increased dysoxic to possible anoxic bottom water conditions but the collingwood member accumulated under a relatively stable paleoceanographic environment rhythmic interbedding with platform limestone in eastern ontario combined with ev

removing the north pacific halocline effects on global climate ocean circulation and the carbon cycle abstract a well pronounced halocline is a key feature of today s subarctic north pacific there is indirect paleo evidences from the last glacial termination as well as from the early and middle pliocene that this halocline has not always been there to study the effects of north pacific salinity on global climate ocean circulation and the marine carbon cycle we perform idealized experiments using an earth system model of intermediate complexity loveclim imposing a negative freshwater flux in the northern north pacific the halocline vanishes and a deep pacific meridional overturning circulation pmoc establishes the associated increase of meridional heat transport in the pacific leads to a bipolar seesaw response in temperature with warming in the north pacific and over north america and cooling in the southern ocean as a result of the formation of north pacific deep water npdw the surface branch of the global conveyor belt circulation weakens transport through the indonesian seas decreases by 50 as the warm and saline waters of the equatorial pacific are diverted into the north pacific in our idealized experiments the enhanced global deep water formation is balanced by an increase in diapycnal mixing as a result nutrient concentrations in the euphotic zone increase by about 25 globally leading to a 20 increase in global export production the effect of greater export production on atmospheric pco 2 is however compensated by the enhanced transport of dissolved inorganic carbon dic to the surface as a result the atmospheric co 2 concentration increases by only 5 ppmv our results further suggest that the absence of the subarctic halocline for instance during heinrich event 1 and the pliocene may have exerted a strong influence on global climate and the carbon cycle

large changes in seasonal sea ice distribution and productivity in the sea of okhotsk during the deglaciations changes in the surface environment of the central sea of okhotsk were reconstructed using tex86 paleothermometry facilitated by the bit index in order to investigate paleoenvironmental changes during the glacial interglacial cycles the core top tex86 derived temperature is the same as the present day summer sea surface temperature sst suggesting that tex86 records seasonal rather than annually averaged ssts in this region the tex86 record reveals 3 c lower summer sst during glacial maxima than during interglacial periods and significant warming during the deglaciations 15 10 ka and 136 130 ka this is consistent with previous inferences of more expanded and persistent seasonal sea ice during the glacial periods than the present day and its substantial retreat during the deglaciation timing of the deglacial warming also coincided with a distinct increase in coccolithophorid productivity suggesting a causal relationship between sea surface warming and coccolithophorid blooms during the deglaciations the relationship could reflect an increase in the supply of fresh and warm water from the amur river during deglaciation which significantly impacted hydrology by facilitating sea surface stratification which in turn promoted production of coccolithophids

environmental change in the sea of okhotsk during the last 1 1 million years on the basis of two sedimentary records from the central sea of okhotsk we reconstruct the closely coupled glacial interglacial changes in terrigenous flux marine productivity and sea ice coverage over the past 1 1 myr the correspondance of our sedimentary records to the china loess grain size record china loess particle timescale chiloparts suggests that environmental changes in both the sea of okhotsk area and in se asia were closely related via the siberian atmospheric high pressure cell during full glacial times our records point to a strong siberian high causing northerly wind directions the extension of the sea ice cover and a reduced amur river discharge deglacial maxima of terrigenous flux were succeeded by or synchronous to high productivity events marine productivity was strengthened during glacial terminations because of an effective nutrient utilization at times of enhanced water column stratification and high nutrient supply from fluvial runoff and sea ice thawing during interglacials se monsoonal winds prevailed analogous to today s summer situation of a pronounced mongolian heat low and a strong hawaiian high strong freshwater discharge induced by high precipitation rates in the amur drainage area and a seasonally reduced and mobile sea ice cover favored marine productivity although being considerably lower than during the terminations and a lowered flux of ice rafted detritus

eustatic and tectonic control on the distribution of marine seismites examples from the upper ordovician of kentucky usa abstract widespread zones of soft sediment deformation are not ubiquitous throughout the rock record rather they are associated with orogenic sediments and are concentrated in specific portions of depositional sequences characterized by deformation prone facies upper ordovician soft sediment deformation features exposed in kentucky are here interpreted as the result of seismically induced thixotropic fluidization of muds resulting in foundering of denser silts and carbonate sands and corresponding diapiric injection of muds severity of soft sediment deformation is associated with sediment density gradients bed thicknesses and varying magnitudes of triggering events the widespread nature 5000 km 2 of multiple deformation horizons argues for a seismic trigger resulting from reactivation of multiple basement faults eight large scale 3rd order depositional sequences were examined for the presence of specific deformation features and stratigraphic position of those intervals the regular distribution of deformation prone facies throughout the upper ordovician seems to have been regulated by eustatic fluctuations seismicity generated by far field tectonics provided the triggering mechanism to disrupt deformation prone strata the record of seismites and their co occurrence with k bentonites provides a meter of intensity and timing of tectophases of the taconic orogeny

origin of silica paleoenvironment and organic matter enrichment in the lower paleozoic niutitang and longmaxi formations of the northwestern upper yangtze plate significance for hydrocarbon exploration abstract lower paleozoic shale is an important source rock and reservoir for gas in the northwestern upper yangtze plate the paleoenvironment and its impact on organic matter enrichment of the shale plays a vital role in the exploration and development of the resource based on the analysis of the results of total organic carbon toc maceral examination bitumen reflectance rb major elements trace elements rare earth elements rees and x ray diffraction xrd of shale samples from the niutitang and longmaxi formations the origin of silica the paleoenvironment and the mode of organic matter enrichment of the shale were examined the shales of the niutitang and longmaxi formations have high toc abundance with type i organic matter and high maturity quartz and clay minerals dominate the mineral constituents leading to characterization as siliceous shale the average sio2 content of the shale in the niutitang and longmaxi formations is above 70 wt al2o3 and tfe2o3 total iron are the next most abundant major elements with average values of 12 80 wt and 1 95 wt in the niutitang formation and average values of 11 44 wt and 4 09 wt in the longmaxi formation compared with the upper continental crust ucc v mo and u are the most enriched elements the average lree hree of the shale samples is very low and the chondrite normalized ree distribution pattern shows sloping lree trends and flat hree trends towards the right the total rare earth elements of the shale vary within the range of 147 85 219 60 ppm and 159 90 222 02 ppm in both the niutitang and longmaxi formations suggesting that the shale has not been subject to obvious hydrothermal fluid activities the correlation diagrams of sio2 al2o3 sio2 toc and siexcess toc the diagrams of hydrothermal origins and the elemental parameters indicate that the silica of the shales from the niutitang and longmaxi formations are mainly of biogenic origins with a lesser contribution from terrigenous detrital sources the ratios of mno2 tio2 and al2o3 al2o3 tfe2o3 of the shale samples all show limited variability illustrating that the shales are mainly deposited on the continental margin the average chemical alteration index cia values of the niutitang and longmaxi formations are 71 25 and 72 77 with little variation and the average sr cu ratios are 4 38 and 2 22 reflecting a warm and humid paleoclimate for both formations the average ni co th u and u readings of the shale samples of the formations are 10 91 0 97 and 1 51 and 12 69 0 43 and 1 75 indicating that the redox conditions during the sedimentation of the formations were anoxic the positive correlations between toc and paleoenvironmental proxies reveal a warm and humid climate and that anoxia had a positive effect on organic matter enrichment these conditions have laid a geological foundation for the enrichment of shale gas and that the upper yangtze plate is favorable for future shale gas exploration

using black shales to constrain possible tectonic and structural influence on foreland basin evolution and cratonic yoking late taconian orogeny late ordovician appalachian basin eastern usa

sea surface temperature changes in the okhotsk sea and adjacent north pacific during the last glacial maximum and deglaciation abstract we estimated sea surface temperatures ssts in the western okhotsk sea during the last glacial maximum lgm and the last glacial termination from measurements of the alkenone unsaturation index u k 37 the t etra e ther inde x of tetraethers consisting of 86 carbon atoms tex 86 and tex 86 l in piston core sediments which reveal the climate response of this region to different types of forcings tex 86 l is a modification of tex 86 proposed for high latitude ocean regions the tex 86 l derived temperatures were not different from the alkenone derived temperatures from the same and nearby sediment samples during the lgm alkenone derived temperatures in the okhotsk sea were relatively warm these and similarly warm alkenone derived temperatures found at many other sites in the western north pacific may reflect a shift in the season of biomarker production from early summer and autumn to mid summer during the lgm as a result of the expansion of the season of sea ice cover empirical orthogonal function eof analysis of alkenone derived temperatures at 14 sites from the north pacific suggested substantial cooling between 20 and 14 cal kyr bp during the deglaciation at 11 of the sites including 4 sites in the okhotsk sea this dominant eof mode suggests either an overall seasonal bias in alkenone derived temperatures or potential shifts in the haptophyseae production season the second eof mode of variability indicated a deglacial warming trend punctuated by millennial scale cold events associated with reorganizations of the atlantic meridional overturning circulation the sst pattern corresponding to this eof mode is indicative of millennial scale meridional shifts of the axis of the westerly jet which may have affected heat transport across the kuroshio reconstructed temperature changes in particular in the okhotsk sea provide insight into the conditions that modulated the ventilation history of intermediate waters in the north pacific

application of organic petrography in north american shale petroleum systems a review abstract organic petrography via incident light microscopy has broad application to shale petroleum systems including delineation of thermal maturity windows and determination of organo facies incident light microscopy allows practitioners the ability to identify various types of organic components and demonstrates that solid bitumen is the dominant organic matter occurring in shale plays of peak oil and gas window thermal maturity whereas oil prone type i ii kerogens have converted to hydrocarbons and are not present high magnification sem observation of an interconnected organic porosity occurring in the solid bitumen of thermally mature shale reservoirs has enabled major advances in our understanding of hydrocarbon migration and storage in shale but suffers from inability to confirm the type of organic matter present herein we review organic petrography applications in the north american shale plays through discussion of incident light photographic examples in the first part of the manuscript we provide basic practical information on the measurement of organic reflectance and outline fluorescence microscopy and other petrographic approaches to the determination of thermal maturity in the second half of the paper we discuss applications of organic petrography and sem in all of the major shale petroleum systems in north america including tight oil plays such as the bakken eagle ford and niobrara and shale gas and condensate plays including the barnett duvernay haynesville bossier marcellus utica and woodford among others our review suggests systematic research employing correlative high resolution imaging techniques and in situ geochemical probing is needed to better document hydrocarbon storage migration and wettability properties of solid bitumen at the pressure and temperature conditions of shale reservoirs

a study of the tex86 paleothermometer in the water column and sediments of the santa barbara basin california 1 particulate organic matter collected during a 2 year period as part of an ongoing sediment trap study and a high resolution sediment record from 1850 to 1987 a d from the santa barbara basin were analyzed for tex86 a temperature proxy based on marine crenarchaeotal membrane lipids highest fluxes of crenarchaeotal lipids in the water column were found in may june 1996 and from october 1996 to january 1997 and in general showed a good correlation with mass fluxes tex86 reconstructed temperatures from the sediment trap series ranged from 8 to 11 c and were usually substantially lower than sea surface temperatures sst indicating that unlike in previous studies the tex86 corresponds to subsurface temperatures likely between 100 and 150 m tex86 temperature variations observed in trap samples were not coupled to changes in sst or deep water temperatures and only to some degree with crenarchaeotal lipid fluxes this suggests that a complex combination of different depth origins and seasonal growth periods of crenarchaeota contributed to the variations in tex86 signal during the annual cycle tex86 temperatures in the two sediment cores studied 8 13 c were also substantially lower than those of instrumental sst records 14 17 5 c confirming that tex86 records a subsurface temperature signal in the santa barbara basin this result highlights the importance of performing calibration studies using sediment traps and core tops before applying the tex86 temperature proxy in a given study area

taconian melanges in the parautochthonous zone of the quebec appalachians revisited implications for foreland basin and thrust belt evolution in the quebec appalachians disruption imbrication and thrusting of the taconian foreland basin sequence are responsible for the development of chaotic units within the turbiditic sequence of the caradocian sainte rosalie group the main lithologic assemblage of the parautochthonous zone these chaotic units have been termed olistostromes or tectonosomes on the basis of field criteria and following pini s 1999 classification olistostromal units containing blocks of the middle mudstone utica shale and upper turbidite units ste rosalie group of the foreland basin and spanning the caradocian n gracilis c americanus o ruedemanni and c spiniferus graptolite zones were deposited and incorporated into the sainte rosalie group disruption of more competent beds of the flyschic sequence and fault stacking and slicing of older rock units occurred along major thrust faults and now form structurally aligned corridors or tectonosomes graptolites and new chitinozoan data from both olistostromes and tec

orbital and millennial scale variations in asian dust transport path to the japan sea abstract orbital and millennial scale variations in the asian monsoon and its probable association with the dansgaard oeschger d o cycles have been demonstrated by previous studies however the origin and nature of such variations are poorly understood the japan sea is located down wind of the arid areas of the eurasian continent and thus receives significant amounts of aeolian dust consequently the hemipelagic sediments of the japan sea are expected to record a continuous aeolian dust accumulation which may provide information about the past variations in asian monsoon grain size flux and provenance of aeolian dust in the sediments were examined using two sediment cores obtained from the northern and southern parts of the japan sea in order to understand the spatial variability of asian monsoon since the silt fraction of the detrital materials in hemipelagic sediments of the japan sea is composed predominantly of aeolian dust the grain size flux and provenance of the silt fraction were examined the taklimakan desert loess plateau and siberia northeast china areas were identified as possible source areas of aeolian dust in the sediments of the japan sea based on the electron spin resonance esr signal intensity and crystallinity of quartz moreover the relative contribution of aeolian dust from each source area was estimated based on the esr signal intensity and crystallinity of quartz aeolian dust fluxes from the two source areas at the southern site were then estimated grain size and flux of eolian dust at the northern site and fluxes of aeolian dust from two source areas at the southern site show orbital scale variations in harmony with the insolation change at 30 n in june these results indicate orbital scale changes in the extent of the arid area and or frequency of dust storms in the taklimakan desert loess plateau and siberia northeast china areas and suggest that southward northward shifts of the westerly jet axis occurred together with either intensified weakened winter monsoon decreased increased winter precipitation in the siberia northeast china area or southeastward northwestward shifts of summer monsoon limit during periods of smaller larger insolation at 30 n in june in addition to these orbital scale variations millennial scale variations possibly associated with the d o cycles are observed in the grain size record of aeolian dust at the two sites based on analogy with orbital scale variations these millennial scale variations are considered to reflect millennial scale changes in the position of the westerly jet axis together with the changes either in winter monsoon intensity winter precipitation or position of summer monsoon limit our results suggest n s oscillations in the westerly jet and summer monsoon limit and changes in the intensity of the winter monsoon on orbital and millennial timescales

what level of resolution is attainable in a deep sea core results of a spectrophotometer study a minolta cm 2022 spectrophotometer has been used to characterize downcore fluctuations in sediment lightness and color in core neap15k a 7 m core collected from the northeast atlantic ocean high resolution data series measured using a 4 mm diameter measurement spot and a 1 cm sampling interval were generated along two independent tracks down the core to investigate the statistical significance of fluctuations across the 2 20 cm depth range this small scale variability is characterized by abrupt changes in the lightness and color of the sediment that are several orders of magnitude greater than the instrumental precision our results establish that significant information is preserved at the 1 cm scale in spite of bioturbation effects these findings demonstrate that high resolution studies using conventional paleoclimatic proxies have the potential to recover meaningful century scale climate records in regions of the ocean where sedimentation rates exceed 10 cm per thousand years the coherency of these downcore records also implies that the spectrophotometer is a powerful instrument for establishing precise centimeter scale stratigraphic correlations between cores

the dansgaard oeschger cycles discovered in the up stream source region of the north pacific intermediate water formation 1 millennial scale oceanographic oscillations were identified in the southern okhotsk sea based on high resolution measurements of total organic carbon toc c n ratios and biogenic opal employing core md01 2412 53 m with the bottom age of 115 ka the oscillations are linked with the dansgaard oeschger d o climatic cycles inadequate data existed in the source regions of the north pacific intermediate water npiw formation thus far we report the first decisive documentation of the d o cycles in the up stream source region of the npiw illustrating that the d o cycles observed in the down stream regions e g santa barbara basin due to expansion of the npiw were in part governed by the climatic variations occurred in the okhotsk sea increases in toc and c n ratios reflect abrupt sea level rises associated with 14 interstadial events over the past 115 kyrs attributing to the downward transport of eroded continental shelf sediments

annual and interannual variability in the kuroshio current system abstract individual seasonal 300 m temperature maps were constructed over the kuroshio current system from 130 e to 170 w for a 4 year period from summer 1976 through spring 1980 using transpac xbt data and jodc temperature depth data quasi stationary meanders in the kuroshic current system occurred at 137 c i e kuroshio meander at 144 e and 150 e i e lee wave meanders and near 160 e i e meander over the shatsky rise a composite of the paths of the kuroshio i e the 12 c isotherm from the individual seasonal maps and the total variance map finds nodes i e minima and anti nodes i e maxima of variability to have existed along the mean kuroshio path the anti nodes coincided with the location of the quasi stationary meanders the nodes in between zonal propagation of temperature anomalies accounted for 20 30 of the total interannual variance these temperature anomalies propagated eastward at 0 5 1 5 cm s 1 in the region 140 155 e and westward at 1 to 2 cm s 1 in the re

a high resolution absolute dated late pleistocene monsoon record from hulu cave china oxygen isotope records of five stalagmites from hulu cave near nanjing bear a remarkable resemblance to oxygen isotope records from greenland ice cores suggesting that east asian monsoon intensity changed in concert with greenland temperature between 11 000 and 75 000 years before the present yr b p between 11 000 and 30 000 yr b p the timing of changes in the monsoon as established with 230th dates generally agrees with the timing of temperature changes from the greenland ice sheet project two gisp2 core which supports gisp2 s chronology in this interval our record links north atlantic climate with the meridional transport of heat and moisture from the warmest part of the ocean where the summer east asian monsoon originates

importance of methanogenesis for organic carbon mineralisation in groundwater contaminated by liquid effluent south australia abstract groundwater in the vicinity of a former abattoir and cheese factory in south east south australia has very high concentrations of dissolved inorganic carbon dic total alkalinity alk and organic and inorganic n due to the disposal of organic rich effluent down drainage boreholes directly into a limestone aquifer one of the possible means of reducing potential nitrate contamination of the aquifer is by adding organic carbon as a substrate for inducing bacterial denitrification a mass balance model of alkalinity dissolved inorganic carbon co 3 2 hco 3 co 2 and 13 c was used to evaluate this approach and to determine the fate of organic carbon derived from the waste isotope and chemical data could be used to distinguish the plume of contaminated groundwater and identify regions which are dominated by methanogenesis or those regions where oxidation reactions dominate the model shows that methanogenesis is responsible for degradation of the largest fraction up to 80 of the organic carbon present organic carbon oxidation rather than methanogenesis is a more important mechanism for c org degradation in the less contaminated boreholes farthest from the factory calcite dissolution appears to be unimportant at least on the time scale since disposal of effluent 70 a

features of the water mass front in the northwestern north pacific analysis of the hydrographic data taken in the northern north pacific has revealed a water mass front defined as the abrupt change of mixing rates between the two typical water masses typical water masses are situated above the main thermocline in the subtropical and subpolar gyres this front termed water mass front in the present study can be regarded as the boundary between the subtropical gyre and the subpolar gyre the index for detecting the frontal position from the temperature field is given as the 5 c isotherm at the 300 m level comparisons with data from previous studies are also made and this front appears to correspond to the subarctic front in almost every instance

tree rings and ice cores reveal c 14 calibration uncertainties during the younger dryas the younger dryas interval during the last glacial termination was an abrupt return to glacial like conditions punctuating the transition to a warmer interglacial climate despite recent advances in the layer counting of ice core records of the termination the timing and length of the younger dryas remain controversial also a steep rise in the concentration of atmospheric radiocarbon at the onset of the interval recorded primarily in the cariaco basin has been difficult to reconcile with simulations of the younger dryas carbon cycle here we discuss a radiocarbon chronology from a tree ring record covering the late glacial period that has not been absolutely dated we correlate the chronology to ice core timescales using the common cosmic production signal in tree ring 14c and ice core 10be concentrations the results of this correlation suggest that the cariaco record may be biased by changes in the concentration of radiocarbon in the upper ocean during the early phase of the younger dryas climate reversal in the cariaco basin this bias in the marine record may also affect the accuracy of a widely used radiocarbon calibration curve over this interval our tree ring based radiocarbon record is easily reconciled with simulated production rates and carbon cycle changes associated with reduced ocean ventilation during the younger dryas attaching a floating tree ring chronology to ice core records that cover the abrupt younger dryas cold interval during the last glacial termination provides a better estimate of the onset and duration of the radiocarbon anomaly the chronology suggests that marine records may be biased by changes in the concentration of radiocarbon in the ocean which may affect the accuracy of a popular radiocarbon calibration program during this interval

influence of pre existing plate margin structures on foredeep filling insights from the taconian blountian clastic wedge southeastern usa break up of continents gives rise to conjugate margins with irregular shapes and with thermal histories and sedimentary records that differ along strike these elements need to be considered in the integrated study of a foreland basin orogenic belt pair that formed during subsequent contractional events this paper relates the promontory and embayment configuration of southeastern laurentia north american craton to 1 along strike variations in width of the initial depositional profile of the middle to upper ordovician taconian blountian foredeep 2 northeastward toward the embayment along strike thickening and migration of siliciclastic depocenters in the foredeep that favored the resumption of carbonate ramp deposition on the promontory during the late ordovician and 3 variation in intensity of deformation of intrabasinal structures as recorded by reactivation of across strike structures located on the transition zone between the promontory and embayment geometry and composition of the blountian foreland strata indicate that the foredeep slope was narrower and steeper on the alabama promontory than on the southwestern flank of the tennessee embayment differential slope geometries were accommodated by reactivation of transverse basement faults which controlled local conglomerate deposition in deep water settings on the transition zone between the promontory and embayment in contrast conglomerate beds at the top of coarsening upward successions on the southwestern flank of the tennessee embayment record the cratonward progradation of deltaic depositional systems the results presented here may have relevance to other peripheral foreland basins formed over rifted continental margins or retro arc foreland basins formed adjacent to inverted intracratonic rifts

calciclastic submarine fans an integrated overview abstract calciclastic submarine fans are rare in the stratigraphic record and no bona fide present day analogue has been described to date possibly because of that and although calciclastic submarine fans have long intrigued deep water carbonate sedimentologists they have largely been overlooked by the academic and industrial communities to fill this gap we have compiled and critically reviewed the existing sedimentological literature on calciclastic submarine fans thus offering an updated view of this type of carbonate slope sedimentary system calciclastic submarine fans range in length from just a few to more than 100 km three different types can be distinguished 1 coarse grained small sized most calciclastic submarine fans were formed on low angle slopes and were sourced from distally steepened carbonate ramps subjected to high energy currents under these conditions shallow water loose grainy sediments were transferred to the ramp slope and eventually funnelled into the submarine fan by sediment gravity flows these conditions seem to have been more easily met on leeward margins in which the formation of reefs was hampered by cool waters nutrient enrichment or oligophoty another circumstance that contributes to the transfer of shallow water sediments to the distal ramp slope is a low sea level forcing the carbonate factory closer to the slope break and destabilizing sediments by increased pore water pressure however the most important factor controlling the development of calciclastic submarine fans was the existence of an efficient funnelling mechanism forcing sediment gravity flows to merge downslope and build up a point sourced sedimentary accumulation in most cases this occurred through a major slope depression associated with tectonic structures an inherited topography or large scale mass failures

ice rafted debris ird based sea ice expansion events during the past 100 kyrs in the okhotsk sea abstract ice rafted debris ird from sediment traps surficial sediments and sediment cores were investigated in order to reconstruct the extent history of sea ice cover during the last 100 kyrs in the okhotsk sea the seasonal ird buried into the sediments during and just after sea ice melting in spring consists of silt and sand size terrigenous particles the spatial distribution of ird within surficial sediments clearly corresponds to the extent of sea ice coverage sea ice expanded to a maximum extent during the glacial periods although sea ice cover was not perennial the okhotsk sea sea ice expansion osie events which are recognized by millennial scale abrupt peaks of ird content have occurred 13 times during the past 100 kyrs these events were amplified during the glacial periods a significant modification of the polar atmospheric circulation in the northern hemisphere is a key process in explaining these osie events

synchronous tropical south china sea sst change and greenland warming during deglaciation the tropical ocean plays a major role in global climate it is therefore crucial to establish the precise phase between tropical and high latitude climate variability during past abrupt climate events in order to gain insight into the mechanisms of global climate change here we present alkenone sea surface temperature sst records from the tropical south china sea that show an abrupt temperature increase of at least 1 c at the end of the last glacial period within the recognized dating uncertainties this sst increase is synchronous with the bolling warming observed at 14 6 thousand years ago in the greenland ice sheet project 2 ice core

paleoenvironmental changes in the northern area of the east china sea during the past 42 000 years a 33 65 m long images md982195 core with very high sedimentation rate ca 80 cm kyr retrieved from the northern part of the east china sea was analyzed at 10 cm intervals about 125 years for oxygen carbon isotope of globigerinoides ruber sensu stricto sea surface temperature sst from alkenones u37 k and principal component analysis of planktonic foraminiferal assemblage the general pattern of the 18o curve resembling the alkenone sst curve is similar to the standard open ocean oxygen isotope curve it reveals many light 18o peaks apparently corresponding to dansgaard oeschger d o cycles as observed in greenland ice cores for the last 42 ka the alkenone sst at the core top is 24 c which is close to the modern annual mean sst around the core site on the other hand sst during the last glacial maximum lgm was about 5 c lower than that in the present day alkenone derived sst does not correlate with the light negative 18o peaks corresponding to the d o cycles the oxygen isotope ratios for the surface waters based on oxygen isotopes of g ruber and alkenone ssts indicate approximately 1 0 increase on average during the lgm and many light peaks at the warm d o events this suggests that fresh water was supplied to the core site during these events the meandering of the westerlies during the cold and warm d o cycles would have caused an atmospheric tele connection between east asia and greenland the core was divided into four periods based on q mode factor analysis of the planktonic foraminiferal assemblage i e 1 a strong upwelling period from 42 to 24 ka indicated by abundant occurrence of globigerina bulloides 2 a cold and low salinity water mass period from 24 to 14 ka suggested by increase of neogloboquadrina pachyderma neogloboquadrina incompta and globigerina quinqueloba 3 a transitional period from cold to warm water masses from 14 to 8 ka as indicated by the increase of warm water species such as pulleniatina obliquiloculata and globigerinoides ruber and 4 the present day warm kuroshio current condition after 8 ka the kuroshio current flowed into the ecs since the last 42 ka and weakened during the last glacial maximum lgm due to the expansion of the coastal water in the northern part of the ecs

distal sedimentation in a peripheral foreland basin ordovician black shales and associated flysch of the western taconic foreland new york state and ontario black shale is characteristic of early siliciclastic fill along the distal western flank of the middle to late ordovician taconic peripheral foreland basin this facies referred to as the utica black shale magnafacies includes at least five intervals bounded by unconformities and or condensed beds each unit records a pulse of subsidence and subsequent siliciclastic sedimentation in the foreland basin progressive episodic shifts from carbonate to organic rich mud deposition may be due to steepening and subsidence of the western carbonate ramp followed by onlap of axially dispersed sediment in general silt poor organic rich mud was deposited on a subsided carbonate ramp that sloped eastward toward the nearest siliciclastic sediment source this mud may have accumulated from the pelitic tails of axial fan turbidites derived from source areas to the east and possibly the south the resultant black shale does not necessarily represent the deepest part of the basin the deepest part of the basin the basin axis contained coarser grained axial submarine fan deposits throughout the later part of the middle ordovician and the first half of the late ordovician the basin axis migrated westward over 100 km yet the orientation of the axis and the basin margins were persistent this basin orientation generally parallel to the orogenic belt along with the large scale basin shape resulted from a combination of deformational loading of the continental margin and progressive flexure in the foreland smaller scale structural elements normal fault bounded basement blocks were superposed on large scale taconic foreland basin geometry abrupt shifts from carbonate ramp sedimentation to deeper water organic rich mud deposition may reflect movement along these faults during the orogeny

distribution and formation of okhotsk sea intermediate water an analysis of isopycnal climatological data 1 in order to clarify the distribution and formation of okhotsk sea intermediate water osiw an isopycnal climatological data set based on all of the available historical observations is developed and examined the isopycnal maps clearly show that there are two direct ventilation sources for osiw dense shelf water dsw with cold and fresh properties influenced by sea ice formation in the northwest shelf region and forerunner of soya warm current water fscw which has warm and saline properties originating in the japan sea the cold and fresh water extends southward from the northwest shelf to the shelf slope off sakhalin island it suggests that dsw is transported southward by the east sakhalin current the dsw enters the kuril basin and mixes with fscw and western subarctic water wsaw originating from the north pacific to form osiw the annual mean production rate of dsw estimated from the total volume of dsw over the shelf in spring and summer is 0 67 sv 1 sv 106 m3 s the annual mean volume transport of fscw is estimated to be 0 08 sv on the basis of its cross section area and the current speed assumption of isopycnal mixing yields a mixing ratio of 1 1 0 1 among dsw wsaw and fscw to form osiw we estimate the annual production rate of osiw to be 1 4 sv the corresponding osiw s renewal time is 7 years continued assumption of isopycnal mixing yields a mixing ratio of 0 6 0 4 between wsaw and osiw to form oyashio intermediate water oyiw

millennial scale sea surface temperature changes in the eastern mediterranean nile river delta region over the last 27 000 years 1 in this study we utilize two organic geochemical proxies the u37k index and tex86 to examine past sea surface temperatures sst from a site located near the nile river delta in the eastern mediterranean em sea the u37k and tex86 records generally are in agreement and indicate sst ranges of 14 c 26 c and 14 c 28 c respectively during the last 27 cal ka during the holocene tex86 based sst estimates are usually higher than u37k based sst estimates which is likely due to seasonal differences between the timing of the haptophyte and crenarchaeota blooms in the em and is related to the onset of the modern flow regime of the nile river both records show that sst varied on centennial to millennial timescales in response to global climate events i e cooling during the last glacial maximum lgm heinrich event 1 h1 and the younger dryas yd and warming during the bolling allerod and in the early holocene during deposition of sapropel s1 the h1 cooling was particularly severe and is marked by a drop in sst of 4 5 c in comparison to pre h1 sst with temperatures 1 c cooler than during the lgm in contrast to high latitude and western mediterranean records which indicate both an abrupt onset and termination of the yd event the transition from the yd to the holocene was much more gradual in the em

characteristics of alkenone distributions in suspended and sinking particles in the northwestern north pacific abstract we investigated alkenones recorded in suspended particles and a settling particle time series collected at three stations 40n 40 n 165 e knot 44 n 155 e and 50n 50 n 165 e in the northwestern north pacific from december 1997 to may 1999 emiliania huxleyi the most abundant alkenone producer in this area is present in surface to subsurface to 50 m depth waters the alkenone concentrations recorded in the suspended particles indicated that the seasonal alkenone particle distribution differed significantly interannually alkenone export fluxes at the three sediment trap stations ranged from 0 16 to 49 3 g m 2 day 1 and the maximum export flux which occurred in summer to fall july november was associated with a high organic carbon export flux the amount of alkenone produced during the maximum export season accounted for 60 80 of the total annual amount of alkenone and the alkenones accumulated in the sediment below the traps had characteristics corresponding to subsurface waters during the summer autumn season alkenone derived temperatures recorded in suspended particles corresponded to the in situ temperature within 2 c although alkenone derived temperatures corresponded approximately to the temperatures observed in the stratified subsurface waters at the three trap stations during the high export season large differences were observed during the low export winter spring period for example the alkenone derived temperatures observed at stations knot and 50n were much higher than the in situ subsurface temperatures reported in the world ocean atlas 2001 relatively large differences between alkenone derived temperatures and in situ temperatures in the subarctic might be due to 1 a low light limitation or 2 contributions of allochthonous alkenones in particulate material transported from subtropical areas within a warm core ring