melting of newly formed mafic crust for the formation of neoproterozoic i type granite in the hannan region south china abstract neoproterozoic magmatism in the hannan region at the northwestern margin of the yangtze block is characterized by numerous felsic plutons associated with minor mafic ultramafic intrusions the felsic plutons are either adakitic or normal arc granitic in composition the adakitic plutons are 735 ma in age and are interpreted as having formed by partial melting of a thickened lower mafic crust among the normal arc related felsic plutons the tianpinghe pluton is the largest and has a shrimp zircon u pb age of 762 4 ma older than the adakitic plutons in the region rocks from the tianpinghe pluton have relatively high sio2 67 1 70 1 wt and k2o na2o 7 8 8 6 wt and relatively low mgo 0 7 1 3 wt and al2o3 contents 14 5 15 6 wt with al2o3 cao k2o na2o a cnk values ranging from 0 95 to 1 08 they have arc affinity trace element compositions that are characterized by enrichment of large ion lithophile elements and depletion of high field strength elements nb ta with strong

stable carbon isotopes of coal derived gases sourced from the mesozoic coal measures in china coal derived large scale gas fields derived from the mesozoic coal measures in china are mainly distributed in the middle lower jurassic coal measures in the tarim junggar and turpan hami basins in northwest china and the upper triassic xujiahe formation coal measure in sichuan basin central china in 2011 the annual production was 21 6 109 m3 and the proved geological reserves were 2485 109 m3 accounting for 21 and 30 of the total in china respectively based on analyses of gas composition and stable carbon isotopes ratios of 203 samples and stable carbon isotopes of 102 co2 samples the following conclusions were made a based on diagnostic plots using the stable carbon isotopic and molecular composition of gas samples alkane gas from the mesozoic coal measures in china is shown to be coal derived b according to the 13c2 vs c2h6 plot of a great number of oil derived and coal derived gases in china it is concluded that gases with 13c2 28 5 are coal derived and those with 13c2 28 5 are oil derived in most cases c among the natural gases from the mesozoic coal measures in china primary coal derived gases with normal carbon isotopic distribution pattern among the c1 c4 alkanes i e 13c1 13c2 13c3 13c4 are dominant d carbon isotopic pattern reversal mainly results from the mixing of coal derived gases having different maturities but the same source and secondly from microbial oxidation of propane e g mu 3 and mu 4 wells in the gumudi gas field junggar basin e co2 in the coal derived gases from the mesozoic coal measures in china has both biogenic and abiogenic origins the biogenic origin is dominant and the abiogenic co2 is mainly found in the kuqa depression in the tarim basin and western sichuan basin f isotopic differences between heavy hydrocarbon gases and methane become less with increasing maturity

measuring and adjusting the weathering and hydraulic sorting effects for rigorous provenance analysis of sedimentary rocks a case study from the jurassic ashikita group south west japan the present study examines the provenance of the jurassic ashikita group distributed in south west japan which is composed of the idenohana kyodomari and sakamoto formations two geochemical diagrams for provenance analysis were utilized which incorporate full consideration of compositional modifications resulting from weathering mfw diagram and hydraulic sorting processes sio2 al2o3 na2o k2o diagram the mfw diagram delineates weathering trends of sedimentary rocks and allows estimation of the original source rock composition by tracing the weathering trends backwards to an unweathered domain weathering trends of the idenohana and kyodomari formations extend backward to the domain of intermediate and felsic igneous rocks in contrast sediments of the sakamoto formation do not fit into a linear weathering trend indicating that the source rock cannot be approximated to igneous rocks on the sio2 al2o3 na2o k2o diagram sediments are organized into compositional trends in which the range reflects compositional variations induced by the hydraulic sorting effect on this diagram sediments derived from the igneous and recycled sedimentary provenances can be distinguished by reading the inclination of the trend by utilizing this principle source rocks of the idenohana and kyodomari formations are interpreted as igneous rocks and those of the sakamoto formation are interpreted as recycled sedimentary rocks therefore these diagrams concurrently estimate the source rock composition through quantifying and adjusting the weathering and sorting effects and reveal a systematic transition in the provenance of the ashikita group the idenohana and kyodomari formations were supplied chiefly from an igneous provenance which shifted from intermediate to felsic compositions in stratigraphic order whereas sediments of the sakamoto formation were sourced primarily from a recycled sedimentary provenance

rio de la plata estuary response to wind variability in synoptic to intraseasonal scales 2 currents vertical structure and its implications for the salt wedge structure 1 the first acoustic doppler current profiler current data collected at two locations of the rio de la plata salt wedge during a period of around 6 months and salinity profiles gathered at and around those locations are used to study the vertical structure of currents response to wind variability in synoptic to intraseasonal timescales and its implications for stratification results indicate that the estuary rapidly responds to prevailing southwesterlies northeasterlies with currents that decay toward the bottom with only little rotation in depth for the less frequent southeasterlies northwesterlies the estuary develops a strong vertical structure with a defined inversion in current direction between surface and bottom layers these patterns derive from the estuary s geometry and bathymetry results have important implications for the salinity vertical structure that are verified on the analyzed profiles first the combination of the bathymetry and coastline with the prevailing wind variability is highly favorable to the maintenance of a salt wedge structure in this estuary second weakening and eventually breakdown of stratification can only occur for intense and or persistent southeasterly winds which even can be very strong are not frequent this can explain why the rio de la plata displays the unusual feature of being an area of spawning and a nursery for a number of coastal species that use the wedge as an essential element for their reproduction results show that stratification is highly affected by short term wind variability which is its major characteristic in the area changing the classical concept of summer winter seasonality as the main feature of estuarine variability

petrogenesis and tectonic significance of the baoxing granitic and mafic intrusions southwestern china evidence from zircon u pb dating and lu hf isotopes and whole rock geochemistry abstract voluminous neoproterozoic gabbros gabbro diorites and granites are exposed in the baoxing area along the western margin of the yangtze block we present here zircon u pb and lu hf isotope data as well as whole rock geochemical data for these rocks which help constrain the tectonic characteristics and evolution of the western margin of the yangtze block zircons from these rocks have high th and u contents and th u ratios 0 2 and show striped absorption patterns growth striations or zoning indicating a typical magmatic origin zircon u pb dating and lu hf isotope results show that the gabbros formed at ca 850 ma with e hf 5 44 to 11 94 and a single stage model age t hf of 1 04 ga suggesting a depleted mantle derived source the gabbro diorites formed at ca 800 ma with major e hf 3 99 to 14 62 and t hf 0 97 ga and minor e hf 0 68 to 5 66 and t hf 1 27 ga again suggesting a depleted mantle derived source the granites were emplaced at ca 770 ma with e hf 2 53 to 10 58 and t hf 1 07 ga indicating that they were derived from the partial melting of juvenile crust the geochemical data show that the gabbros and gabbro diorites are characterized by low sio 2 contents high mg values and cr co and ni contents significant enrichment in light rare earth elements and large ion lithophile elements depletion in high field strength elements e g nb ta zr and hf and relatively high nb u ta u and ce pb ratios these data suggest that the rocks were derived from the partial melting of depleted lithospheric mantle that had been metasomatized by subduction derived fluids or melts and which underwent very minimal crustal contamination during magma evolution and ascent the granites have high sio 2 and k 2 o and low mgo contents exhibit enrichment in rb ba th and pb and depletion in nb ta and ti and have low sr y and la yb n ratios and high y and yb contents which together with their hf isotopic compositions imply a juvenile crust source taking into account regional pre 750 ma arc related magmatism and the subsequent extensional setting it is proposed that a long lived active continental margin setting may have evolved along the western margin of the yangtze block during the neoproterozoic and that the coeval granitic and mafic rocks in the baoxing area were formed by the subduction of the western yangtze block

observed low frequency variability of the brazil current front 1 the brazil current is a weak western boundary current the southwest component of the south atlantic subtropical gyre which is the main conduit of upper ocean waters in the region the objective of this work is to report on observed low frequency variability of the brazil current front using satellite derived sea height anomaly and sea surface temperature observations during the 1993 2008 period the variability of the front is studied in terms of the separation of the brazil current front from the continental shelf break during the study period estimates of this parameter vary 6 degrees in latitude and the mean monthly estimates exhibit a shift to the south of approximately 1 5 degrees statistically significant changes are not observed in the geostrophic transport of the brazil and malvinas currents suggesting that the low frequency changes of the brazil current front are governed by different mechanisms than the seasonal variability of these surface currents surface drifter trajectories and simulations using synthetic drifters are consistent with the observed shift to the south of the brazil current front trends of eddy kinetic energy sea height anomaly sea surface temperature and wind stress curl are also in agreement with the variability reported here wavelet transform analysis revealed interesting changes in the periodicity of the latitude of separation of the brazil current front from the continental shelf break with periods ranging from semiannual to biannual longer records together with comprehensive numerical experiments will ultimately be needed to determine the origin of these changes

brazil malvinas frontal system as seen from 9 years of advanced very high resolution radiometer data 1 surface thermal fronts in the southwestern atlantic swa ocean are examined using 9 years 1987 1995 of advanced very high resolution radiometer data fronts are detected considering a gradient based edge detector sea surface temperature gradients are calculated from 4 km resolution 5 day composite images covering the western argentine basin south of 30 s variability in the position and intensity of the fronts from seasonal to interannual timescales is characterized in six regions including different parts of the brazil current front bcf and the subantarctic front saf shelf break brazil sb b brazil malvinas collision bm c brazil current overshoot bc o shelf break malvinas sb m malvinas return flow mrf and falkland escarpment fe fronts in the sb b sb m mrf and fe regions are controlled by the bathymetry in the bm c region the bcf and saf appear to merge as a single front this front does not present large seasonal north south excursions as previously described though it pivots seasonally around a fixed point located approximately at 39 5 s 53 5 w changing its orientation from n s in winter to nw se in summer consequently on average the front intersects the 1000 m isobath at 38 30 s in summer and north of 37 s in winter in the bc o region the bcf has a u shape centered at 53 w the intensity of the fronts in each region except in the fe region presents large seasonal variability in the sb b bm c and bc o regions the frontal intensity is highest 0 35 c km during austral winter the annual components explain 83 67 and 71 of the total variance respectively in the sb m and mrf regions the saf is most intense 0 25 c km in summer and fall the annual component of the intensity fluctuations explains 29 and 38 of the total variance respectively in the fe region the annual component of frontal intensity explains only 17 of the variability in the six regions important interannual variability is found the zapiola rise centered at 45 s 43 w appears as a gradient free region closed planetary potential vorticity contours in this area suggest it is dynamically isolated

seasonal dynamics of the near surface alongshore flow off central chile 1 the seasonal cycle of the near surface circulation off central chile was analyzed using satellite altimetry and an oceanic model to evaluate the role of the wind stress curl on the circulation we performed two identical simulations except for the wind forcing the control run used long term monthly mean wind stress and the no curl run used a similar wind stress field but without curl the observed and modeled control run surface currents showed a strong seasonal cycle and a well defined equatorward flow with a jet like structure this jet develops during spring and summer consistent with the presence of a low level wind jet south of punta lavapie cape 37 s the equatorward surface current remains close to the coast after the flow passes this cape however it separates to become an offshore jet in contrast in the no curl simulation the separation at punta lavapie is not observed and the offshore jet farther north is not present demonstrating the importance of the wind stress curl on the dynamics of this flow although the offshore integrated sverdrup transport was similar to the model transport the offshore jet was not located where the wind stress curl was maximum instead the position of the jet followed approximately the zero wind stress curl which corresponds to the climatological location of the low level wind jet axis these results illustrate the importance of the offshore upwelling downwelling associated with curl driven ekman pumping which tilts isopycnals upward downward toward the east west of the wind jet forcing a northward flow through thermal wind balance

the patagonian shelf tides the patagonian shelf tides constitute one of the strongest regimes among the biggest in the world where a significant amount of global tidal energy is dissipated by the effect of bottom friction in this paper the tidal response of the patagonian shelf is described by means of information generated by a numerical model and computations of energy fluxes and dissipation rates are presented since measurements of tidal elevations and currents on the patagonian shelf are scarce and mostly limited to coastal locations the information obtained from the model offers valuable insight in a region where a detailed description was not available particularly in the context of global tidal modelling the tidal regime on the patagonian shelf is dominated by the principal lunar semidiurnal tide m2 with contributions from other semidiurnal diurnal and fourth diurnal constituents this regional study shows that dissipation is highly localized and that the integrated value of the dissipation rate over the model domain constitutes a significant fraction of the estimated global dissipation

evidence of upwelling events at the northern patagonian shelf break the patagonian shelf break marks a transition between relative warm fresh shelf waters and relative cold salty subantarctic water advected northward by the malvinas current from early spring to late autumn the outer shelf region is characterized by a band of high chlorophyll concentration that sustains higher trophic levels including significant fisheries we analyze time series of current and water mass property observations collected at two moorings deployed at the shelf edge at 41 s and 43 8 s to investigate what mechanisms lead to temperature variability at the shelf break and their role on the nutrient supply to the upper layer the in situ data are combined with satellite derived observations of sea surface temperature and chlorophyll a to analyze a sharp cooling event at the outer shelf that lasted 10 days and extended 500 km along the outer shelf the event is consistent with upwelling of cold waters through the base of the mixed layer the vertical velocity required to explain the observed cooling is 13 29 m d 1 satellite derived sea surface temperature reveals additional cooling events of similar characteristics seventy five percent of these events are concurrent with surface chlorophyll increase over a 5 day period suggesting that cooling events observed at the shelf break are associated with nutrient fluxes that promote the growth of phytoplankton

coastal oceanographic regimes of the northern argentine continental shelf 34 43 s the oceanographic regimes of the northern argentine continental shelf nacs 34 e43 s are derived from advected waters of subantarctic origin local sources of continental run off and a locally generated salinity maximum based on 3690 ctd profiles monthly mean wind fields at coastal stations and river discharge data we define the oceanographic regimes over the shelf by analyzing salinity characteristics and spatial distribution 1 a maximum in salinity 33 7e34 2 originating from the gulf of san matias 2 a relative salinity minimum 30 0e33 3 of the el rincon estuarine system 3 a salinity minimum 0e33 0 originating in the rio de la plata and 4 waters of the continental shelf 33 5 and 33 7 temperature over the shelf is controlled by seaeair heat exchange coupled with bathymetry an analysis of the simpson parameter of stability f provided an objective definition of a vertically homogenous coastal zone separated from seasonally stratified shelf waters south of 37 s bottom temperature gradients and synoptic sections in the winter and spring indicate the presence of a shallow sea front at the 40e50 m isobaths south of 37 s persistent throughout the year we define two seasonal periods autumnewinter and springesummer based on seasonality in monthly mean winds fields continental run off fresh water balance and the spatial distribution of salinity signals maximum seasonal variation in the extent and location of the oceanographic regimes occurs within the coastal zone in the autumnewinter period we observe a northward extension of the rio de la plata and gulf of san matias waters as well as a reduction of the el rincon and continental shelf waters near the coast the springesummer period is characterized by rio de la plata waters flowing to the south and east a reduction of gulf of san matias waters and an invasion of el rincon and continental shelf waters into the coastal areas in a general sense waters across the nacs undergo a seasonal oscillation in distribution and extension that implies a springesummer reversal of the characteristic shelf wide northenortheastward direction of flow within the coastal zone 2005 elsevier ltd all rights reserved

the fraser gyre a cyclonic eddy off the coast of eastern australia this paper examines the on shelf circulation of the eastern australian continental shelf for a region off southeast queensland we identify a characteristic seasonally reoccurring wind driven cyclonic flow it influences the cross shelf exchange with the east australian current eac which is the western boundary current of the south pacific ocean we refer to this cyclonic circulation as the fraser gyre it is located south of fraser island between about 25 s and 27 s the region is adjacent to the intensification zone of the eac where the current accelerates and establishes a swift albeit seasonally variable southward boundary flow through the analysis of several data sets including remotely sensed sea surface temperature and sea surface height anomaly satellite tracked surface drifters ocean and atmospheric reanalysis data as well as geostrophic currents from altimetry we find that the on shelf fraser gyre develops during the southern hemisphere autumn and winter months the gyre is associated with a longshore near coast northward flow maximum northward on shelf depth averaged velocities are estimated with about 0 15 0 26 ms 1 the flow turns eastward just to the south of fraser island and joins the persistent southward eac flow along the shelf break the annual mean net cross shelf outward and inward flow associated with the gyre is about 1 17 0 23 sv in the north and 0 23 0 13 sv 1 sv 106 m3s 1 in the south mean seasonal water renewal time scales of the continental shelf are longest during austral winter with an average of about 3 3 days due to the fraser gyre retaining water over the shelf however monthly estimates range from 2 to 8 days with the longer timescale during the austral autumn and winter the southerly wind during austral autumn and winter is identified as controlling the on shelf circulation and is the principal driver of the seasonally appearing fraser gyre the conceptual model of the fraser gyre is consistent with general physical principals of the coastal shelf circulation a southerly wind is associated with surface layer flow toward the coast a near coast positive ssha with a current in the direction of the wind down welling and export of shelf water the fraser gyre influenced cross shelf exchanges are possibly facilitating the offshore transport of fish larvae sediments nutrients river discharges and other properties across the shelf break and into the southward flowing eac during the austral autumn and winter

annual cycle in coastal sea level from tide gauges and altimetry 1 tide gauges provide a unique data set extending many decades back in time but coverage is restricted to continental boundaries and a few oceanic islands and the extent to which the tide gauge records can be used to infer low frequency large scale sea level behavior remains unclear since 1992 satellite altimetry provides near global coverage of sea level variability including coastal regions we compare variability at 345 continental and island tide gauge coastal locations and adjacent shallow and deep oceans as inferred from altimetry initial focus is on the dominant annual cycle on average annual amplitudes in tide gauges are comparable to but larger than those in the nearby shallow ocean 200 m substantial differences are found in areas adjacent to strong river outflows and narrow coastal currents the annual cycle in shallow areas is usually enhanced relative to the open ocean apart from areas with strong western boundary currents offshore differences of 1 2 months in annual phases for coastal shallow and deep ocean are typical our analysis points to the presence of considerable spatial variability in the annual cycle across deep shallow and coastal regions and to the importance of both tide gauge and altimeter measurements for proper resolution and interpretation of such variability

interannual to decadal changes in the western south atlantic s surface circulation 1 a combination of surface drifters and altimetry is used to analyze the seasonal to interannual variability of the surface velocity field in the brazil malvinas confluence of the western south atlantic ocean longer term changes are inferred from wind and sea surface temperature fields during the period october 1992 to december 2007 a southward shift of 0 6 to 0 9 decade 1 is found in the confluence latitude of the brazil and malvinas currents a comparable trend is found in the latitude of the maximum wind stress curl averaged across the south atlantic basin allowing a proxy for the confluence latitude to be calculated for the prealtimeter time period this longer time series suggests that the recent trend may be part of a longer term oscillation which has returned to values last sustained in the early 1980s this variation does not appear to be related to the multidecadal trend in the southern annular mode but instead is inversely related to long term variations in the sea surface temperature anomaly in the agulhas benguela pathway of the eastern south atlantic subtropical basin

southern patagonia s perito moreno glacier lake argentino and santa cruz river hydrological system an overview summary an overview of the hydrological data from patagonia s perito moreno glacier lake argentino and santa cruz river system reinforces our previous assertion that the el nino southern oscillation enso and the antarctic oscillation aao are teleconnected with the rupture sequence when the glacier s snout harmonically dams during certain interannual periods the rico branch of lake argentino it is clear however that the incidence of interannual climatic anomalies is not uniform in time and appears embedded in decadal or quasi bidecadal periods of relative damming inactivity the use of nonparametric tests shows that there are no significant positive trends in the river s annual discharge with the only exception of the yearly snowmelt ice melt periods september october when riverine flow appears to increase with statistical significance the question of the glacier s stability looks like a complex multivariate process although we do not rule out the occasional role of enso aao a longer hydrological data series i e 100 years would prove useful in casting some light on this intriguing process surely accounting for the glacier s response time

sea level anomaly on the patagonian continental shelf trends annual patterns and geostrophic flows we study the annual patterns and linear trend of satellite sea level anomaly sla over the southwest south atlantic continental shelf swacs between 54os and 36os results show that south of 42 s the thermal steric effect explains nearly 100 of the annual amplitude of the sla while north of 42 s it explains less than 60 this difference is due to the halosteric contribution the annual wind variability plays a minor role over the whole continental shelf the temporal linear trend in sla ranges between 1 and 5 mm yr 95 confidence level the largest linear trends are found north of 39 s at 42 s and at 50 s we propose that in the northern region the large positive linear trends are associated with local changes in the density field caused by advective effects in response to a southward displacement of the south atlantic high the causes of the relative large sla trends in two southern coastal regions are discussed as a function meridional wind stress and river discharge finally we combined the annual cycle of sla with the mean dynamic topography to estimate the absolute geostrophic velocities this approach provides the first comprehensive description of the seasonal component of swacs circulation based on satellite observations the general circulation of the swacs is northeastward with stronger weaker geostrophic currents in austral summer winter at all latitudes geostrophic velocities are larger up to 20 cm s close to the shelf break and decrease toward the coast this spatio temporal pattern is more intense north of 45 s

a numerical study of the southwestern atlantic shelf circulation stratified ocean response to local and offshore forcing 1 this article discusses the results of a suite of numerical simulations of the oceanic circulation in the southwestern atlantic shelf region that are aimed to characterize its mean circulation and seasonal variability and to determine the dynamical mechanisms controlling them our experiments indicate that south of 40s the mean circulation is dominated by a general northeastward flow in the southern portion of the shelf which is controlled by the discharges from the magellan straits tidal mixing wind forcing and the offshore influence of the malvinas current farther north the region from 40 st o 33s presents the highest seasonal variability with intrusions of cold sub antarctic waters

multiple controls on the preservation of organic matter in devonian mississippian marine black shales geochemical and petrographic evidence geochemical and petrographic analysis of an interval of black shales between the huron shale member of the new albany shale upper devonian famennian and the sunbury shale lower mississippian tournaisian suggests that multiple controls influenced the accumulation of organic matter stratigraphic trends were determined following detailed analysis of a core from the central appalachian basin d6 montgomery county ky specifically c s fe relationships mo v v ni ni co and v cr were used to assess paleo redox conditions during sediment accumulation the role of clastic input was evaluated using ti al k al and si al and c p was used as a proxy for paleoproductivity the terrestrial to marine maceral ratio t m vitrinite plus inertinite alginite plus bituminite was used to evaluate changes in om source c s fe relationships and trace element ratios suggest anoxic conditions prevailed during deposition of much of the upper part of this interval however bottom water conditions were intermittently dysoxic during accumulation of the huron shale member and possibly dysoxic to marginally oxic during accumulation of the lowermost huron shale member productivity appears to have been an important factor in the accumulation of corg and high c p ratios are consistent with a productivity anoxia feedback mechanism in addition nutrients from increased terrestrial weathering may have contributed to enhanced productivity variations in sediment influx may also have influenced corg concentrations through sediment starvation one of the more significant observations in this work is an increase in terrestrial om inertinite and vitrinite up section which may reflect vegetative changes occurring on land during this time interval most of this increase is due to inertinite much of which appears to be fusinitic in origin and hence may be fossil charcoal this latter observation has implications for the expansion of land plants into drier niches and for late devonian atmospheric oxygen levels introduction of more resistant terrestrial om to anoxic basins may have been an important factor in the preservation of high carbon 10 intervals especially in the cleveland member of the new albany shale upper devonian famennian and the sunbury shale lower mississippian tournaisian

the surface circulation of the caribbean sea and the gulf of mexico as inferred from satellite altimetry the surface circulation of the caribbean sea and gulf of mexico is studied using 13 years of satellite altimetry data variability in the caribbean sea is evident over several time scales at the annual scale sea surface height ssh varies mainly by a seasonal steric effect interannually a longer cycle affects the ssh slope across the current and hence the intensity of the caribbean current this cycle is found to be related to changes in the wind intensity the wind stress curl and el nino southern oscillation at shorter time scales eddies and meanders are observed in the caribbean current and their propagation speed is explained by baroclinic instabilities under the combined effect of vertical shear and the b effect then the loop current lc is considered focusing on the anticyclonic eddies shed by it and the intrusion of the lc into the gulf of mexico through time twelve of the 21 anticyclonic eddies observed to detach from the lc are shed from july to september suggesting a seasonality in the timing of these events also a relation is found between the intrusion of the lc into the gulf of mexico and the size of the eddies shed from it larger intrusions trigger smaller eddies a series of extreme lc intrusions into the gulf of mexico when the lc is observed as far as 928w are described the analyses herein suggest that the frequency of such events has increased in recent years with only one event occurring in 1993 versus three from 2002 to 2006 transport through the straits of florida appears to decrease during these extreme intrusions

paleoreef maps evaluation of a comprehensive database on phanerozoic reefs to get a better understanding of controls on reef development through time we created a comprehensive database on phanerozoic reefs the database currently comprises 2470 reefs and contains information about geographic position paleoposition age reef type dimensions environmental setting paleontological and petrographical features and reservoir quality of each buildup reef data were analyzed in two qualitatively different ways the first type of analysis was by visualization of paleogeographic reef distribution maps five examples late devonian early permian late triassic late jurassic middle miocene are presented to show the potential of paleoreef maps for paleogeographic and paleoclimatological reconstructions the second type of analysis was a numerical processing of coded reef characteristics to realize major trends in reef evolution and properties of reef carbonates the analysis of paleolatitudinal reef distributions through time shows pronounced asymmetries in some time slices probably related to climatic asymmetries rather than controlled by plate tectonic evolution alone the dominance of particular reef builders through time suggests that there are seven cycles of phanerozoic reef development first curves for the phanerozoic distribution of bioerosion in reefs bathymetric setting and debris potential of reefs are presented the observed pattern in the temporal and spatial distribution of reefs with reservoir quality may assist in hydrocarbon exploration statistical tests on the dependencies of reefal reservoir quality suggest that large size high debris potential low paleolatitude high amount of marine aragonite cement and a platform shelf edge setting favor reservoir quality reefal reservoirs are significantly enhanced in times of high evaporite sedimentation elevated burial of organic carbon low oceanic crust production low atmospheric co2 content and cool paleoclimate as well as when they are present in aragonite oceans

tectonic and climate control of oil shale deposition in the upper cretaceous qingshankou formation songliao basin ne china oil shales were deposited in the songliao basin ne china during the upper cretaceous period representing excellent hydrocarbon source rocks high organic matter om contents a predominance of type i kerogen and a low maturity of om in the oil shales are indicated by bulk geochemical parameters and biomarker data a major contribution of aquatic organisms and minor inputs from terrigenous land plants to om input are indicated by n alkane distribution patterns composition of steroids and organic macerals strongly reducing bottom water conditions during the deposition of the oil shale sequences are indicated by low pristane phytane ratios high c14 aryl isoprenoid contents homohopane distribution patterns and high v ni ratios enhanced salinity stratification with mesosaline and alkaline bottom waters during deposition of the oil shales are indicated by high gammacerane index values low mttc ratios high carotene contents low toc s ratios and high sr ba ratios the stratified water column with anoxic conditions in the bottom water enhanced preservation of om moderate input of detrital minerals during the deposition of the oil shale sequences is reflected by titanium concentrations in this study environmental conditions in the paleo lake leading to om accumulation in the sediments are related to sequence stratigraphy governed by climate and tectonics the first member of the qingshankou formation k2qn1 in the songliao basin containing the oil shale sequence encompasses a third order sequence that can be divided into three system tracts transgressive system tract tst highstand system tract hst and regressive system tract rst enrichment of om changed from low values during tst i to high moderate values during tst ii iii and hst i ii low om enrichment occurs during rst i and rst ii therefore the highest enrichment of om in the sediments is related to stages of mid late tst and early hst

structural complexities in a foreland thrust belt inherited from the shelf slope transition insights from the alishan area of taiwan the alishan area of taiwan spans the transition from the platform with full thickness of the eurasian continental margin in the north to the thinning crust of its slope in the south this part of the foreland thrust and fold belt includes important along strike changes in structure stratigraphy and seismic velocities in this paper we present the results of new geological mapping from which we build geological cross sections both across and along the regional structural trend fault contour stratigraphic cutoff and branch line maps provide 3 d consistency between the cross sections minimum shortening is estimated to be 15 km with displacement overall to the northwest a p wave velocity model helps constrain the structure at depth by providing insight into the possible rock units that are present there p wave velocities of 5 2 km s point toward the presence of basement rocks in the shallow subsurface throughout much of the southeastern part of the area forming a basement culmination the changes in strike of thrusts and fold axial traces the changing elevation of thrusts and stratigraphic contacts and the growing importance of middle miocene sediments that take place from north to south are interpreted to be associated with a roughly northeast striking lateral structure coincident with the northern flank of this basement culmination these transverse structures appear to be associated with the inversion of eocene and miocene age extensional faults along what was the shelf slope transition in the early oligocene uplifting the margin sediments and their higher p wave velocity basement during pliocene pleistocene thrusting

the patagonian shelf circulation drivers and variability abstract a high resolution ocean model is used to characterize the local and remote driving mechanisms of the variability of the patagonian shelf circulation local forcing includes the effects of tides buoyancy fluxes and wind while remote forcing represents the impact of the adjacent deep ocean currents there is an abrupt change of the dynamical characteristics of the shelf circulation at 40 s south of 40 s the seasonal variations of the shelf circulation are out of phase with the local wind stress and are driven by deep ocean inflows originated in the drake passage the inter annual variability of the shelf circulation is principally driven by the wind and shows a significant correlation with the time variations of the southern annular mode index the variability of the circulation and upwelling at the shelfbreak region are modulated by the variability of the malvinas current transport at low frequency periods higher than two years and by the local wind stress at higher frequencies north of 40 s the local wind forcing drives the seasonal variations of the shelf transport the inter annual variability of the flow is driven by the combined action of the rio de la plata discharge significantly correlated with the el nino southern oscillation local wind stress and the brazil malvinas confluence in the outer shelf in agreement with previous studies we show that while the position of the confluence marks the location of the largest offshelf transports it does not determine their magnitude the offshelf transport variability is controlled by the local wind at high frequency periods less than a year and by the equatorward inflow of southern waters at longer periods our simulation indicates that the variability of the subtropical shelf front is modulated by the local wind stress forcing position of the brazil malvinas confluence and the equatorward inflow of subantarctic waters

geochemical characteristics and organic matter enrichment mechanism of black shale in the upper triassic xujiahe formation in the sichuan basin implications for paleoweathering provenance and tectonic setting abstract the first third and fifth members henceforth referred to as t 3 x 1 t 3 x 3 and t 3 x 5 respectively of the upper triassic coal bearing xujiahe formation black shale are among the most significant hydrocarbon source rocks in the sichuan basin here we present geochemical data for the upper triassic black shales from core from well ld 1 to determine their paleoenvironmental conditions paleoweathering provenance transitions and tectonic setting the v v ni vs u th v cr vs u th and ni co vs u th bivariate plots and the tfe toc ts total fe total organic carbon total sulphur ternary diagram indicate that the synsedimentary redox regime of almost all the shale samples was oxidizing ba al sr al and p ti data combined with quantitative biogenic ba data indicate that moderate high primary paleoproductivity levels prevailed during deposition the sr cu ratio and c value combined with the sedimentary features are indicative of warm humid climate conditions the ti al deposition rate proxy and decompacted sedimentation rate are positively correlated with the total organic carbon toc content according to our multiproxy approach black shale development in the xujiahe formation was mainly controlled by the primary productivity level foreland basin setting high tectonic subsidence and sedimentation rate and exhibited a limited correlation with water column redox conditions through the compilation and calculation of various weathering indices for the xujiahe black shale we suggest that caution must be taken when inferring paleoclimate characteristics based on the chemical index of alteration cia because of the influence of multiple nonweathering factors provenance sensitive elemental ratios th sc vs zr sc and co th vs la sc indicate that the clastic contribution to xujiahe black shales was of a predominantly felsic character the black shales exhibit a transition from t 3 x 1 to t 3 x 3 to t 3 x 5 whereby t 3 x 1 was primarily sourced from the proterozoic to early paleozoic strata of the qinling orogeny t 3 x 3 was primarily sourced from the neoproterozoic complex in the longmen shan and t 3 x 5 was primarily sourced from the songpan ganzi flysch strata which contributed recycled material because of folding and strong southeastward thrusting

a two way nested simulation of the oceanic circulation in the southwestern atlantic this article presents the results of a high resolution 1 12 two way nested simulation of the oceanic circulation in the southwestern atlantic region a comparison between the model results and extant observations indicates that the nested model has skill in reproducing the best known aspects of the regional circulation e g the volume transport of the acc the latitudinal position of the bmc the shelf break upwelling of patagonia and the zapiola anticyclone sensitivity experiments indicate that the bottom stress parameterization significantly impacts the mean location of the brazil malvinas confluence and the transport of the zapiola anticyclone the transport of the brazil current strengthens during the austral summer and weakens during the austral winter these variations are driven by the wind stress curl over the southwestern atlantic the variations of the transport of the malvinas current are out of phase with those of the brazil current most of the seasonal variability of this current is concentrated in the offshore portion of the jet the inshore portion has a weak seasonality that modulates the magnitude of the patagonian shelf break upwelling using passive tracers we show that most of the entrainment of deep waters into the shelf occurs in the southernmost portion of the patagonian shelf and along the inshore boundary of the brazil current shelf waters are preferentially detrained near the brazil malvinas confluence consistent with previous studies our simulation also shows that south of 42 s the malvinas current is composed of two jets which merge near 42 s to form a single jet farther north

two phase stratigraphic model of foreland basin sequences application of flexural models to nonmarine foreland basin evolution indicates that two different stratigraphic styles of basin fill may develop over time basin subsidence is most rapid during times of thrust load emplacement associated sedimentation is coarse grained immediately adjacent to the thrust front and grades rapidly into fine grained deposits that cover most of the basin the distal part of the basin may also contain deposits derived from streams that flow from beyond the basin toward the thrust belt subsequent removal of the thrust load by erosion and other processes results in flexural rebound of the thrust belt and adjacent foreland basin during this postorogenic phase of adjustment a regional unconformity develops in the proximal part of the foreland basin proximal deposits along with thrust derived sediment are redeposited in the distal foreland basin and beyond this two phase model of foreland sedimentation predicts that coarsening upward sequences in the proximal and distal parts of the basin have reciprocal significance the proximal sequence represents thrust belt advance whereas the distal sequence represents thrust belt cessation

the salinity signature of the cross shelf exchanges in the southwestern atlantic ocean numerical simulations a high resolution model is used to characterize the dominant patterns of sea surface salinity sss variability generated by the freshwater discharges of the rio de la plata rdlp and the patos mirim lagoon in the southwestern atlantic region we identify three dominant modes of sss variability the first two which have been discussed in previous studies represent the seasonal and the interannual variations of the freshwater plumes over the continental shelf the third mode of sss variability which has not been discussed hitherto represents the salinity exchanges between the shelf and the deep ocean a diagnostic study using floats and passive tracers identifies the pathways taken by the freshwater plumes during the austral winter jja the plumes leave the shelf region north of the bmc during the austral summer djf the plumes are entrained more directly into the bmc a sensitivity study indicates that the high frequency component of the wind stress forcing controls the vertical structure of the plumes while the low frequency component of the wind stress forcing and the interannual variations of the rdlp discharge controls the horizontal structure of the plumes dynamical analysis reveals that the cross shelf flow has a dominant barotropic structure and therefore the sss anomalies detected by aquarius represent net mass exchanges between the shelf and the deep ocean the net cross shelf volume flux is 1 21 sv this outflow is largely compensated by an inflow from the patagonian shelf

quality assessment of a satellite altimetry data product in the nordic barents and kara seas 1 satellite altimetry provides high quality sea surface height data that have been successfully used to study the variability of sea level and surface geostrophic circulation at different spatial and temporal scales however the high latitude regions have traditionally been avoided due to the persistent sea ice cover most of the validation studies have focused on the areas below the polar circles in this paper we examine the quality and performance of a gridded satellite altimetry product in the nordic barents and kara seas the altimetric sea level in coastal areas is validated using available tide gauge records we show that at most locations in the nordic seas the altimetry and tide gauge measurements are in a good agreement in terms of the root mean square differences and the amplitudes and phases of the seasonal cycle the agreement deteriorates in the shallow areas of the barents and kara seas subject to the seasonal presence of sea ice and where the altimetry data are contaminated by the residual aliasing of unresolved high frequency signals the comparison of linear trends at the locations of tide gauges reveals discrepancies that need to be taken into account when interpreting long term changes of sea level in the region away from the coast the altimetry data are compared to drifter trajectories corrected for ekman currents the drifter trajectories are found consistent with the mesoscale variability of the altimetric sea level this study provides the first comprehensive validation of a gridded satellite altimetry data product in the high latitude seas

stable carbon and hydrogen isotopes of natural gases sourced from the xujiahe formation in the sichuan basin china abstract the compound specific hydrogen and carbon stable isotope ratios of alkanes in natural gases from the xujiahe and jurassic formations in the western sichuan basin were investigated to distinguish between coal derived and oil associated gases all gases were determined to be coal derived and sourced from the xujiahe formation thermal maturities of the source rocks are expected to vary from 0 8 1 8 vitrinite reflectance ro according to the empirical relationship between the measured 13cch4 values and ro which is within the scope of the maturities of source rocks 0 7 2 1 in particular c1 3 alkanes of primary coal derived gases which have not undergone any secondary alteration become more enriched in deuterium with increasing molecular mass and the dch4 values increase with increasing thermal maturity of source rocks in the sichuan basin d values of coal derived gases sourced from terrigenous source rocks of the xujiahe formation are more negative than those of oil associated gases sourced from marine organic matter of the sinian permian and triassic formations

coefficients for sea surface wind stress heat flux and wind profiles as a function of wind speed and temperature surface layer coefficients for wind profiles wind stress and heat flux in typical open sea conditions are briefly reviewed businger dyer flux gradient relationships and a charnock wind stress formula fit the empirical data and are dimensionally consistent these have been solved by an iterative method and the results are presented in a tabular form suitable for climatological calculations from marine wind and temperature data

spatial variation in sediment fluxes redox conditions and productivity in the permian triassic panthalassic ocean abstract two permian triassic boundary sections in central japan provide a rare window into environmental conditions within the panthalassic ocean which encompassed more than half the earth s surface at 252 ma integration of petrographic geochemical and time series data provides new insights regarding the fluxes of major and trace components to the sediment as well as environmental conditions in both the deep and intermediate water masses at each study site the ubara section was located in a high productivity peri equatorial location whereas the gujo hachiman section was located in a moderate productivity location at some distance from the paleoequator an upward transition from gray organic poor cherts to black siliceous mudstones at both sites occurred in conjunction with increased primary productivity intensified euxinia within the oxygen minimum zone omz and decimation of the radiolarian zooplankton community euxinia in the omz of the equatorial panthalassic ocean developed episodically for a 200 250 kyr interval during the late permian followed by an abrupt intensification and lateral expansion of the omz around the permian triassic boundary throughout the study interval bottom waters at both sites remained mostly suboxic a finding that counters hypotheses of development of a superanoxic permo triassic deep ocean as a consequence of stagnation of oceanic overturning circulation

altimeter derived seasonal circulation on the southwest atlantic shelf 27 43 s altimeter sea surface height ssh fields are analyzed to define and discuss the seasonal circulation over the wide continental shelf in the sw atlantic ocean 27 43 s during 2001 2012 seasonal variability is low south of the rio de la plata rdlp where winds and currents remain equatorward for most of the year winds and currents in the central and northern parts of our domain are also equatorward during autumn and winter but reverse to become poleward during spring and summer transports of shelf water to the deep ocean are strongest during summer offshore and to the southeast of the rdlp details of the flow are discussed using mean monthly seasonal cycles of winds heights and currents along with analyses of empirical orthogonal functions principle estimator patterns bring out the patterns of wind forcing and ocean response the largest part of the seasonal variability in ssh signals is due to changes in the wind forcing described above and changes in the strong boundary currents that flow along the eastern boundary of the shelf the rest of the variability contains a smaller component due to heating and expansion of the water column concentrated in the southern part of the region next to the coast our results compare well to previous studies using in situ data and to results from realistic numerical models of the regional circulation

the influence of the plata river discharge on the western south atlantic shelf 1 the influence of the plata the second largest river in south america extends along a coastal strip of 1300 km historical hydrographic and wind data and numerical simulations are combined to determine the seasonal and interannual variability of the plata plume and its relationship to the magnitude of the river discharge and the intensity and direction of the wind stress our results indicate that the seasonal variability of the river plume is controlled by the alongshore component of the wind stress during el nino the effects of the wind and precipitation anomalies tend to compensate each other preventing anomalous northeastward plume extensions associated to large outflow events numerical experiments confirm this finding and indicate that during el nino the discharge from the plata river spreads offshore

relationship between inferred redox potential of the depositional environment and geochemistry of the upper pennsylvanian missourian stark shale member of the dennis limestone wabaunsee county kansas u s a analyses of 21 samples collected from a core of the 52 8 cm thick stark shale member of the dennis limestone in wabaunsee county kansas demonstrate four cycles with two orders of magnitude variations in contents of cd mo p v and zn and order of magnitude variations in contents of organic carbon cr ni se and u the observed variability in amounts and or ratios of many metals and amounts and compositions of the organic matter appear related to the cause and degree of water column stratification and the resulting absence presence of dissolved o2 or h2s high cd mo u v zn and s contents a high degree of pyritization dop 0 75 0 88 and high high v v ni 0 84 0 89 indicate the presence of h2s in a strongly stratified water column intermediate contents of metals and s intermediate dop 0 67 0 75 and intermediate v v ni 054 0 82 indicate a less strongly stratified anoxic water column whereas low metal contents and low v v ni 0 46 0 60 indicate a weakly stratified dysoxic water column high p contents at the top of the organic matter rich intervals within the stark shale member indicate that phosphate precipitation was enhanced near the boundary between anoxic and dysoxic water compositions relatively abundant terrestrial organic matter in intervals deposited from the more strongly stratified h2s bearing water column indicates a combined halocline thermocline with the fresher near surface water the transport mode for the terrestrial organic matter the predominance of algal organic matter in intervals deposited from a less strongly stratified water column indicates the absence of the halocline and the presence of the more generally established thermocline relatively low amounts of degraded hydrogen poor organic matter characterize intervals deposited in a weakly stratified dysoxic water column the inferred variability in chemistry of the depositional environments may be related to climate variations and or minor changes in sea level during the general phase of deeper water deposition responsible for this widespread shale member

sediment generation in humid mediterranean setting grain size and source rock control on sediment geochemistry and mineralogy sila massif calabria abstract grain size control on sediment composition is investigated in modern proximal sediment from the sila massif where basic to felsic intrusive rocks are exposed in a mediterranean humid temperate upland climate samples were taken from small creeks and weathering profiles from three areas reflecting different bed rock compositions samples were separated into eleven grain size fractions from very coarse sand to clay and analyzed by i x ray fluorescence for chemical composition and ii x ray diffraction and mineral liberation analysis for mineralogical composition the chemical composition vs grain size relations were modeled by compositional linear regression mineralogical composition of selected samples is used to substantiate the interpretations based on geochemistry results reveal a high degree of chemical weathering with chemical index of alteration cia up to 92 high cia values are restricted to the fine grained fractions while sand sized sediment average at low to moderate cia values 60 although strongly weathered the three sample suites reflecting basic to felsic plutonic bed rock can be effectively discriminated across all grain size classes using trace elements such as v rb and sr linear trend modeling and mineralogical data reflect similar patterns for all sample suites implying similar processes independent of source rock composition this includes overall decrease of quartz and k feldspar over the full grain size range from very coarse sand to clay which is contrasted by overall increase of sheet silicates from coarse to fine among the latter increase of clay minerals strongly outpaces the increase of micas in silt to clay fractions a more complex behavior is shown by plagioclase which is most abundant in intermediate grain size fractions for all sample suites this is likely caused by initial hydrolysis along cleavage and twinning planes and subsequent breakage of plagioclase crystals into smaller fragments towards finer grain size intense hydrolysis has destroyed most feldspars

on the wind contribution to the variability of ocean currents over wide continental shelves a case study on the northern argentine continental shelf fil lago loreley selene consejo nacional de investigaciones cientificas y tecnicas oficina de coordinacion administrativa ciudad universitaria centro de investigaciones del mar y la atmosfera universidad de buenos aires facultad de ciencias exactas y naturales centro de investigaciones del mar y la atmosfera argentina universidad de buenos aires facultad de ciencias exactas y naturales departamento de ciencias de la atmosfera y los oceanos argentina instituto franco argentino sobre estudios del clima y sus impactos argentina