statistics of geomagnetic storms and ionospheric storms at low and mid latitudes in two solar cycles 1 the statistics of occurrence of the geomagnetic storms and ionospheric storms at kokubunji 35 7 n 139 5 e 26 8 n magnetic latitude in japan and boulder 40 0 n 254 7 e 47 4 n in america are presented using the dst and peak electron density nmax data in 1985 2005 covering two solar cycles 22 23 when 584 geomagnetic storms dst 50 nt occurred in addition to the known solar cycle and seasonal dependence of the storms the statistics reveal some new aspects 1 the geomagnetic storms show a preference for main phase mp onset at around ut midnight especially for major storms dst 100 nt over 100 excess mp onsets at ut midnight compared to a uniform distribution 2 the number of positive ionospheric storms at kokubunji about 250 is more than double that at boulder and 3 the occurrence of the positive storms at both stations shows a preference for the morning noon onset of the geomagnetic storms as expected from a physical mechanism of the positive storms 4 the occurrence of negative ionospheric storms at both stations follows the solar cycle phases most frequent at solar maximum better than the occurrence of positive storms which agrees with the mechanism of the negative storms

clinoforms and clinoform systems review and dynamic classification scheme for shorelines subaqueous deltas shelf edges and continental margins abstract clinoforms are inclined and normally basinward dipping horizons developed over a range of spatial and temporal scales in both siliciclastic and carbonatic systems the study of clinoform successions underpins sequence stratigraphy and all efforts to reconstruct the relative partitioning of reservoir seal and source rocks along shoreline to basin floor profiles here we review clinoform research and propose a more systematic description and classification of clinoforms this is a crucial step to improve predictions of facies and lithology distribution within shoreline to continental shelf and abyssal plain successions together with the genesis drivers and dynamics of their constituent sedimentary units four basic clinoform types are here distinguished in delta shorelines lacustrine and marine environments on the basis of their overall spatial and temporal scale morphology outbuilding dynamic and geodynamic and depositional setting 1 2 delta scale clinoforms which in turns are sub divided into shoreline and delta scale subaqueous clinoforms 3 shelf edge clinoforms and 4 continental margin clinoforms delta scale clinoform sets are tens of metres high and typically represent 1 103 kyr with progradation rates ranging from 1 000 100 000 m kyr for shorelines and subaerial deltas to 100 20 000 m kyr for subaqueous deltas shelf edge clinoform sets are hundreds of metres high and are nucleated and accreted in 0 1 20 myr usual progradation rates of 1 100 m kyr by successive cross shelf transits of delta scale clinoforms continental margin clinoform sets are thousands of metres high hallmark key geodynamic crustal boundaries e g continent ocean transition and slowly prograde basinwards in ca 5 100 myr with typical rates of 0 1 10 m kyr as a consequence of the very different progradation rates and of the difficulty of large scale clinothems to backstep during transgressions shorelines are the most dynamic clinoforms with regards to position continental margins the least and shelf edges are intermediate shortly after a transgression therefore the four clinoform types may prograde synchronously along shoreline to abyssal plain transects forming compound clinoform systems during the subsequent regressive cycle however due to the dissimilarity in progradation rates different clinoform types will normally merge progressively with each other giving rise to hybrid clinoforms e g shelf edge deltas and fewer depositional breaks in slope are distinguished along a single shoreline to abyssal plain transect overall all clinoform systems are the result of the dynamic evolution of compound and hybrid clinoforms along a temporal and spatial continuum regulated by the cyclical backstepping of the smaller scale system within natural progradational retrogradational cycles of larger scale clinothem outbuilding all clinothem types may show either an accretionary active or draping passive style depending on the proximity to the sediment source draping clinothems are nearly always composed of condensed fine grained sediments while actively accreting clinothems can be composed of predominantly coarse grained i e reservoir forming or predominantly fine grained i e non reservoir lithotypes a novel hierarchical classification scheme for both recent and ancient clinoforms is here proposed consisting of 12 classes the four basic clinoform types delta scale shoreline delta scale subaqueous shelf edge and continental margin are sub divided into eight accretionary active and draping passive sub types 8 division each accretionary sub type is then sub divided into a sandstone prone and mudstone prone variant 12 division which can be at least tentatively predicted on the basis of the clinoform morphology even in the absence of direct stratigraphic logs

chitinozoan graptolite and scolecodont reflectance as an alternative to vitrinite and pyrobitumen reflectance in ordovician and silurian strata anticosti island quebec canada because of the absence of vitrinite in lower paleozoic sediments the reflectance of pyrobitumen is used as an indicator of thermal maturation a new technique of preparing organic matter permits discrimination among types of zooclasts and solid bitumen including pyrobitumen and leads to more precise reflectance histograms studies of organic matter from ordovician silurian strata of anticosti island show that reflectance of zooclasts is different from that of solid bitumen and that each group of the following zooclasts chitinozoans graptolites and scolecodonts has a specific reflectance evolution path with increasing depth on a logarithmic scale the paths of the three groups of zooclasts are linear highly correlated and converging however reflectance of solid bitumen is not linear throughout the range studied solid bitumen becomes linear only where the reflectance is greater than 0 75 comparing the relations between zooclasts and solid bitumen with the vitrinite solid bitumen correlation in the literature suggests that a hypothetical vitrinite evolution line in the anticosti island basin should be subparallel with that of chitinozoans and graptolites but 0 4 0 8 lower in the 1 2 range however scolecodonts and vitrinite should have the same reflectance at 1 but scolecodont reflectance should be slightly 0 2 higher for a vitrinite reflectance of 2

late pleistocene and holocene vegetation changes and anthropogenic impacts in the cauvery delta plains southern india abstract a 5 m long core from uttarangudi in the distal plain of cauvery delta in south india provides evidences of vegetation climate and anthropogenic activities during the late pleistocene and holocene the pollen catchment area for this region is the localised sources including the adjoining tertiary upland plateau the recorded variation in pollen assemblages and sediments indicates that the environmental conditions have changed over time from aerial oxidising to lacustrine or ponded environment the lack of pollen records from 17 802 cal bp until 11 535 cal bp suggests severe drier conditions and an extremely patchy species poor tropical dry evergreen forest tdef vegetation community associated with an arid climate between 11 535 and 8487 cal bp partial climatic amelioration appears to have occurred and the trend become humid until 7034 cal bp characterised by the expansion of the tdef vegetation and strengthening of the monsoon precipitation the period from 7034 3553 cal yr bp recorded a regressive transition of the forest taxa influenced by a weakened monsoon precipitation and enhanced anthropogenic activity the subsequent increase of disturbance signals post 3553 cal yr bp is in agreement with independent archaeological evidences obtained from this region

preliminary organic petrography of palaeozoic rocks from the grand banks newfoundland abstract samples of lower palaeozoic bedrock from the grand banks of newfoundland were examined using reflected light microscopy and rock eval pyrolysis these samples contained organic material which included bitumen structureless organic material acritarchs chitinozoa scolecodonts and graptolites the reflectance of the organic material increased from acritarchs towards graptolites with bitumen showing a wide range of reflectance multiple phases of oil migration through one sample were inferred by examination of the bitumens the lowest reflecting being more recent than the highest reflecting bitumen combined reflectance and rock eval analysis indicate that these samples are mature to overmature the two oldest samples arenig llanvirn ordovician are assessed as mature and as having potential for generation of liquid hydrocarbons but must be considered as mainly gas prone

pollen and charcoal based evidence for climatic and human impact on vegetation in the northern edge of wuyi mountains china during the last 8200 years pollen and charcoal records derived from the sediment core of lantianyan lty peat bog northern wuyi mountain chains eastern subtropical china provide valuable information of landscape evolutio

pollen and non pollen palynomorph analyses of upper holocene sediments from dianshan yangtze coastal lowlands china hydrology vegetation history and human activity abstract the coastal deltaic plain of the yangtze river between taihu lake tai and shanghai in eastern china has been the scene of human settlement and agriculture since the early neolithic becoming increasingly intensive in the upper holocene when delta accretion and the establishment of a stable hydrological regime of freshwater lakes and wetlands allowed the development of extensive agriculture and complex society in late prehistoric and dynastic times during this period the area was significantly affected by changes in sea level climate and vegetation resulting in a dynamic and complex environmental history however little research has concentrated on environmental change and human impacts during the last few millennia this study focuses on this late period presenting the results of integrated sedimentary microfossil and radiocarbon analyses from a core near the eastern margin of lake dianshan to the east of taihu after the withdrawal of intertidal conditions and the conversion to freshwater lake at the core site about 2600 cal yr bp pollen and algal spore data show that increased sedimentation gradually reduced freshwater depth until a surface peat formed ca 1500 cal yr bp this also dates the start of a switch in woodlands from sub tropical and warm temperate trees to a mainly cool temperate and coniferous tree flora under climatic cooling and human impact after this time water depths at the site increased greatly partly due to climate change and flooding but also because of the establishment of deepwater paddy agriculture microcharcoal and pollen data show that a major episode of human impact using fire with deforestation and rice cultivation occurred between ca 1500 and 1200 cal yr bp these dates suggest it is one of the latest examples of flooded field paddy cultivation before more intensive agricultural techniques were adopted in the area after ca 800 cal yr bp

contrasting behavior of the f2 peak and the topside ionosphere in response to the 2 october 2013 geomagnetic storm in this study the ionospheric observations from ionosondes ground based gps receivers gravity recovery and climate experiment grace and metop a satellites and fabry perot interferometer over the asian australian sector have been used to investigate the responses of the f2 peak and the topside ionosphere to the 2 october 2013 geomagnetic storm particularly during the recovery phase the comparison between the multiple simultaneous observations revealed a contrasting behavior of the topside ionosphere and the f2 peak in east asia during the recovery phase the upward looking total electron content from low earth orbit leo satellites did not undergo such depletions as seen in the region near the f2 peak and they even showed increases furthermore the simulation results of the thermosphere ionosphere electrodynamics general circulation model are used to explore the possible mechanisms responsible for the observed features the model results and observations suggested that the contrasting behavior of the f2 peak and the topside ionosphere is mainly associated with the enhancement of the equatorward winds albeit the disturbed electric fields could play an important role in producing it

long duration penetration of the interplanetary electric field to the low latitude ionosphere during the main phase of magnetic storms 1 it is well known that the interplanetary electric field can penetrate to the low latitude ionosphere it is generally believed that the penetration of electric fields can last only for 30 min because of the shielding effect in the ring current in this paper we present the observations of the dayside ionospheric electric field enhancements at middle and low latitudes in association with reorientations of the interplanetary magnetic field imf in six cases the eastward electric field in the dayside equatorial ionosphere measured by the jicamarca incoherent scatter radar was enhanced for 2 3 hours after the imf turned southward and remained continuously southward in one case the eastward electric field in the dayside midlatitude ionosphere measured by the millstone hill incoherent scatter radar was continuously enhanced for 10 hours during southward imf since millstone hill is close to the equatorward boundary of the auroral zone during magnetic storms the penetration electric field there may be different from that at the equatorial ionosphere the most striking feature of the measurements is that the enhancements of the ionospheric electric field can last for many hours without significant decay the electric field enhancements in the middle and low latitude ionosphere are closely related to magnetic activity and occur during the main phase of magnetic storms the observations show that the interplanetary electric field can continuously penetrate to the low latitude ionosphere without shielding for many hours as long as the strengthening of the magnetic activity is going on under storm conditions

the long duration positive storm effects in the equatorial ionosphere over jicamarca the long duration positive storm lps in the equatorial regions is relatively poorly understood in this report we conducted a statistical analysis of the lps effects in the equatorial ionosphere over jicamarca 12 0 s 283 2 e in 1998 2010 there are 250 geomagnetic storms minimum dst 50 nt in 1998 2010 but the ionosonde observations at jicamarca are available only for 204 storms a total of 46 lpss are identified in terms of the criterion that the storm time relative deviation of peak density of f2 layer nmf2 exceeds 25 for more than 6 h a salient feature is that the occurrence of lpss tends to decay approximately exponentially on the following days after the main phase of geomagnetic storms the ratios of the number of equatorial lpss to that of geomagnetic storms have no obvious dependence on season and solar activity during the daytime lpss the disturbed zonal electric field is mostly westward as indicated from the geomagnetic field changes in the equatorial american region for the nighttime lpss the significant uplifting of f2 layer caused by an eastward electric field is the most important feature therefore the disturbed electric field should play an essential role in forming the equatorial lpss

deltas radiocarbon dating and measurements of sediment storage and subsidence in holocene marine deltaic sequences there is no simple relationship between radiocarbon age and depth of sampling the nile and ganges brahmaputra deltas show remarkably similar radiocarbon age depth relationships 1 most radiocarbon dates by conventional and accelerator mass spectrometric ams analyses are older some by 4000 yr than reasonably expected 2 dates are commonly inverted i e older upcore and 3 sample dates at delta surfaces commonly exceed 2000 yr b p these anomalous age depth phenomena are in part a response to reservoir effects introduction of old carbon and emphasized herein influence of sediment storage and remobilization that prevail in fluvial and delta plains in fluvial systems sediment generally is not transported in a single episode from its original source area to the sea rather material transported from upland reaches and river valley to coast is subject to a repeated series of depositional burial and erosional events induced by episodic flooding overbank sedimentation and channel migration because sediment is likely to be temporarily stored in the delta plain it is difficult to determine the time of a sediment9s final deposition and burial at a delta site a successful strategy requires use of several independent dating methods including ams analyses of in situ basal peats and fossils and where possible archaeological evaluation of associated artifacts that are in place accurate dates are needed for reliable measurement of rates of delta plain aggradation and land subsidence information to help implement effective coastal protection measures

a case study of ionospheric storm effects during long lasting southward imf bz driven geomagnetic storm multiple instrumental observations including gps total electron content tec fof2 and hmf2 from ionosondes vertical ion drift measurements from communication navigation outage forecasting system magnetometer data and far ultraviolet airglow measured by thermosphere ionosphere mesosphere energetics and dynamics global ultraviolet imager timed guvi are used to investigate the profound ionospheric disturbances at midlatitude and low latitude during the 14 17 july 2012 geomagnetic storm event which was featured by prolonged southward interplanetary geomagnetic field component for about 30 h below 10 nt in the east asian australian sector latitudinal profile of tec variations in the main phase were characterized by three bands of increments and separated by weak depressions in the equatorial ionospheric anomaly eia crest regions which were caused by the combined effects of disturbance dynamo electric fields ddef and equatorward neutral winds in the recovery phase strong inhibition of eia occurred and the summer crest of eia disappeared on 16 july due to the combined effects of intrusion of neutral composition disturbance zone as shown by the timed guvi o n2 measurements and long lasting daytime westward ddef inferred from the equatorial electrojet observations the transit time of ddef over the dip equator from westward to eastward is around 2200 lt in the american longitude the salient ionospheric disturbances in the summer hemisphere were characterized by daytime periodical intrusion of negative phase for three consecutive days in the recovery phase preceded by storm enhanced density plume in the initial phase in addition multiple short lived prompt penetration electric fields appeared during stable southward interplanetary magnetic field imf bz in the recovery phase and were responsible for enhanced the eia and equatorial ionospheric uplift around sunset

neolithic settlement distributions as a function of sea level controlled topography in the yangtze delta china combined geological and archaeological data sets indicate that sea level controlled topography best explains the timing of neolithic settlement onto the southern yangtze delta plain almost 1500 yr later than inland china information on settlement patterns of the three major neolithic cultures ma jia bang song ze liang zhu dated from ca 5500 to 2200 b c is provided by petrologic study of habitat bases of sites and of sediment cores recovered near the sites in the early holocene rising sea level induced decreased relief and an aggrading silt mantle on the low lying delta surface changes of sea level and climate from early to mid holocene initiated a fertile delta plain at ca 6000 5500 b c and settlement and cultivation including rice began within only 500 yr of delta formation rate of sea level rise decelerated by mid holocene time resulting in rising ground water level and poor drainage and a reduced delta plain area suitable for human occupation and agriculture as a consequence neolithic settlements shifted progressively eastward toward higher more restricted areas of the yangtze delta chenier plain

agriculture and environmental change at qingpu yangtze delta region china a biomarker stable isotope and palynological approach rice oryza sp agriculture sustains vast numbers of people and despite great advancements made in recent years questions about its origins and spread throughout asia remain unanswered this study uses sedimentary biomarker stable carbon isotope and palynological analyses to investigate early rice agriculture in the yangtze delta a region where rice agriculture emerged at least 7000 years ago accelerator mass spectrometer ams 14c dating reveals the age of sedimentary section to be between c 6000 and 1800 cal bp widespread clearing of forest vegetation c 2400 cal bp is the earliest major human influence detected in the qingpu record following this rice agriculture probably dominated the qingpu area evidence supporting rice agriculture after c 2400 cal bp is provided by increased poaceae and cereal type taxa which occur with high concentrations of plant wax n alkanes with a dominant c3 plant origin c27 c31 with odd even preference 13c 29 8 to 36 3 also high concentrations of a

new insights into the origin of perylene in geological samples abstract the origin of the polycyclic aromatic hydrocarbon pah perylene in sediments and petroleum has been a matter of continued debate reported to occur in phanerozoic organic matter om fossil crinoids and tropical termite mounds its mechanism of formation remains unclear while a combustion source can be excluded structural similarities to perylene quinone like components present in e g fungi plants crinoids and insects potentially suggest a product precursor relationship here we report perylene concentrations 13c 12c and d h ratios from a holocene sediment profile from the qingpu trench yangtze delta region china perylene concentrations differ from those of pyrogenic pahs and rise to prominence in a stratigraphic interval that was dominated by woody vegetation as determined by palynology including fungal spores in this zone perylene concentrations exhibit an inverse relationship to the lignin marker guaiacol d h ratios between 284 and 317 similar to the methoxy groups in lignin as well as co variation with spores from wood degrading fungi 13c 12c of perylene differs from that of land plant wax alkanes and falls in the fractionation range expected for saprophytic fungi that utilise lignin which is isotopically lighter than cellulose and whole wood during progressive lignin degradation the relative carbon isotopic ratio of the perylene decreases we therefore hypothesise a relationship of perylene to the activity of wood degrading fungi to support our hypothesis we analysed a wide range of phanerozoic sediments and oils and found perylene to generally be present in subordinate amounts before the evolutionary rise of vascular plants and to be generally absent from marine sourced oils few exceptions being attributed perhaps to a contribution of marine and or terrestrial derived fungi anoxia especially under marine conditions and or contamination of core material by fungi a series of low molecular weight aromatic quinones bearing the perylene backbone were detected in devonian and cretaceous sediments potentially representing precursor components to perylene

pyrobitumen in south china organic petrology chemical composition and geological significance abstract pyrobitumen has been discovered in the dolostone reservoir of the central sichuan basin southwest china accumulates coevally with hydrothermal minerals in pores the pyrobitumen has strong anisotropy with an evolutionary sequence from mosaic to a fibrous texture a similar sequence of anisotropy has also been observed in mesophase pitch during the process of coking coal reflectance of the pyrobitumen shows a positive correlation with anisotropic evolution and increasing depth hopane and sterane biomarkers are abundant in extracts of highly anisotropic pyrobitumen with smooth rough hyperplastic surface and honeycomb micropores methylpyrene and methylchrysene maturity indicators and the reflectance values of pyrobitumen show a positive linear correlation in cambrian samples but show random correlation in sinian samples fluid inclusion microthermometry of hydrothermal minerals together with the burial and heat flow history of the reservoir indicate an abrupt thermal event that may have impacted the generation and evolution of pyrobitumen this appears to be confirmed by the reflectance values of pyrobitumen in the source rock and reservoir the pyrobitumen in source rock was less heated by the hydrothermal fluid due to its poor porosity and have lower reflectance values however the pyrobitumen in weathering crust reservoir was more heated by the hydrothermal fluid and have higher reflectance values because the reservoir rocks have higher porosity the occurrence and characteristics of pyrobitumen indicate an in situ pyrolysis of oil which was triggered by an abrupt thermal event in the reservoir the reconstruction of burial history and heat flow as well as the hydrothermal fluid minerals of the dolomite reservoir all indicate the thermal event of the sichuan basin might correlate with the emei mantle plume in late permian

a sediment based record of lateglacial and holocene environmental changes from guangfulin yangtze delta eastern china studies of the coastal sedimentary record have allowed both the reconstruction of relative sea level changes and the determination of local rates and magnitudes of tectonic deformation particularly in tectonically active areas despite their successful use elsewhere studies of this type are much less common for the mexican pacific coast which parallels the cocos north america subduction plate boundary stratigraphic geochemical and microfossil data from sediments in laguna mitla the pacific coast of guerrero mexico document late holocene sea level changes induced by tectonic activity in the mexican subduction zone three major events are identified first file formation of the lagoon by c 4630 yr bp as indicated by a freshwater to brackish peat second a relative sea level rise or land subsidence as indicated by a shift from a freshwater marginal lagoon environment to a marine setting preceded by a marine inundation represented by a sand unit possibly a tsunami deposit by c 3400 yr bp and finally a return to lagoonal conditions indicating a drop in relative sea level or coastal uplift by e 2300 yr bp the laguna mitla stratigraphy indicates general coastal subsidence or relative sea level rise of c 1 mm yr we argue that these relative sea level land level changes have been induced by tectonic activity associated with the mexican megathrust a plausible explanation for the 3400 yr bp marine inundation is probably a tsunami produced by a large seismic event accompanied by coastal subsidence discrete fining upward fine to coarse sand units with an erosional basal contact medium to poor sorting and clay mud rip up clasts all increase in na and sr elemental concentrations indicative of a marine origin and the landward extent of the sands support a tsunamigenic source for these deposits however these apparent tsunami deposits require further study to determine their lateral extent and to assess whether they call be correlated from one site to another this study demonstrates the applicability of a multiproxy sedimentary approach in interpreting relative sea level land level changes and to derive data on related earthquake and tsunami events in tropical coastal lagoons

assessment of gps global ionosphere maps gim by comparison between code gim and topex jason tec data ionospheric perspective 1 we performed a comprehensive comparison between gps global ionosphere map gim and topex jason t j total electron content tec data for the periods of 1998 2009 in order to assess the performance of gim over the global ocean where the gps ground stations are very sparse using the gim model constructed by the center for orbit determination in europe at the university of bern the gim tec values were obtained along the t j satellite orbit at specific locations and times of measurements and then binned into various geophysical conditions for direct comparison with the t j tec on the whole the gim model was able to reproduce the spatial and temporal variations of the global ionosphere as well as the seasonal variations however the gim model was not accurate enough to represent the well known ionospheric structures such as the equatorial anomaly the weddell sea anomaly and the longitudinal wave structure furthermore a fundamental limitation of the model seems to be evident in the unexpected negative differences i e gps t j at night represent the plasmaspheric contribution to gps tec which is maximized reaching up to 100 of the corresponding t j tec values in the early morning sector in particular the relative differences decreased with increasing solar activity and this may indicate that the plasmaspheric contribution to the maintenance of the nighttime ionosphere does not increase with solar activity which is different from what we normally anticipate

environmental change and its impacts on human settlement in the yangtze delta p r china abstract archaeological excavations and environment archaeology studies over many years in the yangtze delta region have provided exceptional information about climatic variations growth and demise of human civilization and human environment interactions the archaeological excavations show that the cultural layers of the neolithic sites are interrupted by barren layers without any cultural relics so called cultural interruptions which may be the result of harsh environmental conditions arid flooding extreme cold or warmth temporal and spatial analyses of 14c dates for buried trees peat shell ridges and neolithic sites show that environmental changes are responsible for the rise and fall of human civilization the progress of human civilization was interrupted at least 5 times in the yangtze delta matching 5 periods of high sea level peat accumulation and burial of trees the collapse of the liangzhu culture about 4000 bp was followed by the less developed maqiao culture and resulted from extreme environmental and hydrological conditions such as floods

review and update of the applications of organic petrology part 1 geological applications abstract organic petrology developed as coal petrology at the beginning of the 20th century dedicated mainly to the study of coals because of their utilization in industry coal petrology was then considered a branch of coal science later with the development of specialized nomenclature classification of coal components and the standardization and improvement of analytical microscopical methods this discipline expanded in interests and name becoming organic petrology organic petrology carries a broader context being as well a tool applied in the study of dispersed organic matter in sedimentary rocks due to its importance in exploration for fossil fuel resources at present organic petrology is a discipline widely recognized for its role in fundamental and applied research with respect to both coal utilization and in geosciences throughout the 20th century several important monographs have been published on the discipline of organic petrology including stach s textbook of coal petrology 1st edition 1935 2nd 1975 3rd 1982 updated as the more general organic petrology by taylor et al 1998 more recently the text applied coal petrology the role of petrology in coal utilization was published by suarez ruiz and crelling 2008 this review is the first in a two part review series that describes and updates the role of organic petrology in geosciences a second part complementing this one and focused on the applications of organic petrology to other scientific fields will follow

longitudinal variations of topside ionospheric and plasmaspheric tec the upward looking ionospheric total electron content tec from the metop a and tsx satellites during 2008 2015 has been used to systematically study the longitudinal variations of the topside ionosphere and plasmasphere the results of this study are summarized as follows 1 there are significant longitudinal variations in the topside ionosphere and plasmasphere at low latitudes the tec maximum during the june solstice over the western and central pacific ocean corresponds to a tec minimum at the same location during the december solstice but the opposite behavior occurs over south america and the atlantic ocean 2 during the solstices the relative longitudinal variations in the geomagnetic equatorial region do not have a strong dependence on local time and solar activity 3 the tec in the winter hemisphere decreases with increasing solar activity especially at higher altitudes and at night the topside tec depletion with solar activity depends on longitude 4 the solstice like longitudinal pattern lasts much longer than the equinox like patterns with the june solstice pattern lasting the longest furthermore the equinox like longitudinal patterns occur in march when expected whereas they extend from the autumnal equinox until the end of october 5 the longitudinal variations of upward looking tec are different from the corresponding longitudinal variations of electron densities around the f2 peak and orbital altitudes this indicates that the topside ionosphere structure is strongly influenced by the physical processes in the topside region rather than being a pure reflection of the ionospheric f2 peak structure

molecular marker records of land use change abstract evidence of a changing environment in the catchment area of a small lake gormire yorkshire uk over the past 3000 years is provided by the mean carbon number of n alkanes and the ratio of lignin thermochemolysis products together with pollen analysis and bulk organic geochemistry periods of deforestation which commenced at 600 bc and ad 1200 display a significant decrease in organic carbon contents of the lake sediments which probably reflects dilution by enhanced influx of clastic material the mean carbon number of waxy c27 c31 n alkanes closely corresponds with the percentage of pollen derived from grass in the sediments a higher plant derived triterpenoid tentatively identified from its mass spectrum as 28 carboxyursen 12 enol appears exclusively in samples where tree and shrub derived pollen is dominant thermochemolysis of lignin confirms that there was a significant change in the nature of material deposited in the lake sediments from woody to grass dominated changes in both the sedimentary c n ratios and yields of lignin derived phenols suggest that deforestation events led to enhanced aquatic productivity initially through the development of reed swamp vegetation

salinity variations in the northern coorong lagoon south australia significant changes in the ecosystem following human alteration to the natural water regime abstract european settlement and drought have significantly impacted the hydrology of the coorong a shallow coastal lagoon complex in south australia which is part of a terminal wetland at the mouth of the river murray an increased salinity associated with lower water levels and progressive isolation from ocean flushes contributed to a severe decline in ecological diversity over the past decades here we have conducted a molecular and stable isotopic study of a sedimentary core from the northern coorong lagoon spanning more than 5000 years to investigate the recent palaeoenvironmental history of the ecosystem major alterations were evident in many biogeochemical parameters in sediments deposited after the 1950s coinciding with the beginning of intensified water regulations the most prominent shift occurred in 13 c profiles of c 21 c 33 n alkanes from average values of 23 5 to an average of 28 2 further changes included decreases in carbon preference index cpi and average chain length acl of the n alkane series as well as significant increases in algal e g c 20 hbi long chain alkenes and c 29 alkadiene and bacterial e g 13 c depleted short chain n alkanes and hopanoids 13 c 35 9 to 30 1 derived hydrocarbons long chain n alkanes with a strong odd even predominance as observed here are typically attributed to terrigenous plants in the coorong however terrigenous input to sedimentary om is only minor therefore changes in the before mentioned parameters were attributed to a source transition from a major contribution of macrophytes towards predominantly microalgae and bacteria d values of c 21 c 33 n alkanes showed a general trend towards more enriched values in younger sediments indicating an overall rising salinity however the most pronounced positive shift in these profiles again occurred after the 1950s altogether this study demonstrates that the recent human induced changes of the coorong hydrology compounded by a severe drought led to an increase in salinity and alterations of primary production which have been much more significant than natural variations occurring throughout the holocene over several thousands of years

lithological and palynological evidence of late quaternary depositional environments in the subaqueous yangtze delta china abstract ams 14c ages of post glacial core sediments from the subaqueous yangtze delta along with sedimentary structures and distributions of grain size pollen spores and dinoflagellate cysts show an estuarine depositional system from 13 to 8 4 cal ka bp and a deltaic system from 5 9 cal ka bp to the present the estuarine system consists of intertidal to subtidal flat estuarine and estuarine front facies characterized by sand mud couplets and a high sedimentation rate the deltaic system includes nearshore shelf and prodelta mud featured by lower sedimentation rate markedly fewer coastal wetland herbaceous pollens and more dinoflagellate cysts we explain the extremely high sedimentation rate during 9 2 8 4 cal ka bp at the study site as a result of rapid sea level rise high sediment load due to the unstable monsoonal climate and subaqueous decrease of elevation from inner to outer estuary a depositional hiatus occurred during 8 2 5 9 cal ka bp the transition from estuarine to deltaic system caused possibly by a shortage of sediment supply resulting from delta initiation in paleo incised yangtze valley and strong tidal or storm related reworking in offshore areas the subsequent development of deltaic system at the study site indicates accelerated progradation of yangtze delta post 5 9 cal ka bp

effects of disturbed electric fields in the low latitude and equatorial ionosphere during the 2015 st patrick s day storm the 2015 st patrick s day geomagnetic storm with sym h value of 233 nt is an extreme space weather event in the current 24th solar cycle in this work we investigated the main mechanisms of the profound ionospheric disturbances over equatorial and low latitudes in the asian australian sector and the american sector during this super storm event the results reveal that the disturbed electric fields which comprise penetration electric fields pefs and disturbance dynamo electric fields ddefs play a decisive role in the ionospheric storm effects in low latitude and equatorial regions pefs occur on march 17 in both the american sector and the asian australian sector the effects of ddefs are also remarkable in the two longitudinal sectors both the ddefs and pefs show the notable local time dependence which causes the sector differences in the characteristics of the disturbed electric fields this differences would further lead to the sector differences in the low latitude ionospheric response during this storm the negative storm effects caused by the long duration ddefs are intense over the asian australian sector while the repeated elevations of hmf2 and the eia intensifications caused by the multiple strong pefs are more distinctive over the american sector especially the storm time f3 layer features are caught on march 17 in the american equatorial region proving the effects of the multiple strong eastward pefs

influences of geomagnetic fields on longitudinal variations of vertical plasma drifts in the presunset equatorial topside ionosphere on the basis of the measurements from the ion drift meter on the defense meteorological satellite program f13 satellite from 2000 to 2002 the relative longitudinal variations of e x b vertical plasma drifts in the presunset equatorial topside ionosphere at 1745 lt are examined obvious influences of geomagnetic fields on longitudinal variations of e x b vertical plasma drifts which also show a seasonal dependence have been found during the june solstice the relative vertical plasma drifts is most significantly influenced by the geomagnetic field declination however the relative vertical plasma drifts during the december solstice more strongly correlates with the geomagnetic field strength although the relative vertical plasma drifts during equinox are also influenced by the geomagnetic field declination an underlying dependence on magnetic field magnitude as seen in december is also present

influence of igneous intrusions on thermal maturity and optical texture comparison between a bituminous marl and a coal seam of the same maturity abstract the impact of a 120 cm thick dike on dispersed organic matter in the triassic marry harbour mh bituminous marl in the raanes peninsula ellesmere island arctic canada was studied using reflected light microscopy and rock eval pyrolysis results were compared to a coal seam of similar maturity that was thermally altered by an igneous intrusion the mh bituminous marl is mature and within the oil window ro 0 94 whereas the coal is high volatile b bituminous rank ro 0 80 thermal alteration impacted differently the organic rich marl than the coal seam most of the heat generated by the intrusive emplacement in contact with coal is spent transforming coal to coke in the plastic layer zone similar to the process that coal undergoes in industrial coking operations in contrast the thermal alteration of sedimentary rocks occurs over longer distances as a result of the absence of a plastic layer zone the impact zone of the 120 cm thick igneous intrusion was greater in the mh bituminous marl which became thermally altered ro 2 34 at 190 cm from the contact with the dike on the contrary the coal became thermally altered ro 5 0 by a 240 cm alkali basalt intrusion twice the thickness of the mh dike and its impact zone was only 65 cm heat and hot volatile matter produced by the thermal decomposition of organic matter and minerals carbonate dehydration of clay minerals in contact with the igneous intrusion body is transferred through the sedimentary rock matrix by convection through fractures this transformation is evident by the occurrence of the pyrolytic carbon at various distances in the fractured mh marl from contact the hydrogen index hi shows a similar trend to that of the remaining source potential s2 both parameters decrease systematically toward the dike and go through a minimum at 20 cm from the dike contact as the indigenous organic matter is converted to hydrocarbons or devolatilized at the dike contact both s2 and hi have higher values these trends are similar to those of the volatile elements h and cl in the intruded coal seam the free hydrocarbons s1 showed a slightly different trend than s2 and hi it increased initially from 300 cm and reached a maximum at about 190 cm from the dike contact before decreasing continually and reaching a minimum at 20 cm from the contact at the dike contact the s1 increased slightly similar to the hi and s2 the presence of oil droplets trapped in carbonate concretions in combination with the highest value of oil expelled from the source rock based on s1 toc at distance of 190 cm from dike is an indication of the influence of contact metamorphism on oil generation locally furthermore it indicates that intrusion of igneous dikes into the bituminous mh marl resulted in an increase of organic matter maturation locally and in hydrocarbon generation

variations in the low and middle latitude topside ion concentration observed by dmsp during superstorm events 1 observations of the topside ion number density by the dmsp satellites on the dayside near 0930 lt and near dusk describe a characteristic evolution during the course of three superstorm events in november 2001 november 2003 and november 2004 density enhancements at middle latitudes and at the equator may be identified as separate features that may appear together but can evolve independently these characteristics are consistent with the action of both upward outward e b drifts and equatorward neutral winds and it is suggested that both f region drivers are required to reproduce the observed behavior on these occasions upward excursions of the e b drift at the equator may be short lived compared to the satellite orbit period of about 100 min but may also exist for longer periods under the influence of penetration fields and modified dynamo fields upward drifts at middle latitudes may be induced by meridional winds and by the high latitude convection pattern as it expands to latitudes as low as 40 degrees magnetic

dating and characterizing primary gas accumulation in precambrian dolomite reservoirs central sichuan basin china insights from pyrobitumen re os and dolomite u pb geochronology abstract primary gas accumulation with trillions of cubic meters of gas volumes was discovered recently in the precambrian dengying formation of the gaoshiti moxi block central sichuan basin china in this study we investigated the pervasive saddle dolomite cements and solid bitumens within karst vugs in the dengying dolomite reservoirs using laser ablation inductively coupled plasma mass spectrometry la icp ms in situ u pb dating we obtained a high precision absolute age of 259 4 3 0 ma for the saddle dolomite cementation consistent in timing with the eruption of emeishan flood basalts 262 251 ma combined with high homogenization temperatures th and salinities of primary fluid inclusion as well as rare earth element ree compositions we consider that the saddle dolomite precipitation was likely related to hydrothermal activity driven by the emeishan mantle plume the identification of rare surviving oil inclusions and extensive solid bitumens within the dolomite vugs is indicative of the presence of paleo oil reservoirs these bitumens are characterized by high equivalent vitrinite reflectance requ no fluorescence and deformed fibrous textures typical of highly mature pyrobitumens gas geochemistry data indicates that only minor thermochemical sulfate reduction tsr has occurred thus the pyrobitumen was interpreted to result mainly from the thermal cracking of paleo oils and its associated re os isochron age of 154 21 ma representing the timing of dry gas formation petrographical evidence suggests that the paleo oil charge must have taken place after sparry dolomite cementation but prior to pyrobitumen generation this combined with coeval aqueous inclusion th data and published thermal burial models constrains the time of paleo oil emplacement to ca 222 205 ma suggesting an oil filling event related to the indosinian orogeny this study documented the first chronological data constraining the complex evolution history of a petroleum system in one of the oldest primary gas reservoirs in the world

migration patterns of neolithic settlements on the abandoned yellow and yangtze river deltas of china archaeological records of the neolithic settlements on the eastern china coast between 35 n and 30 n an area covering the abandoned yellow river and the yangtze river delta plains reveal that neolithic people moved from the yellow river basin onto the northern coast for fishing hunting and dry land agriculture 7000 yr ago marine transgression interrupted their activities on the low lying 2 5 m in elevation coastal wetlands between 6000 and 5000 yr ago after which they reclaimed their land near the river mouths their migration routes on the southern yangtze delta plain indicate another scenario early neolithic communities moved onto the plain for wet rice cultivation despite relative sea level rise from 7000 to 4000 yr ago a large number of settlements were established on the lowlands between the eastern chenier ridges and the western taihu lake depression the chenier ridges with 1 0 m higher topography than the adjacent coastal area played a role in sheltering the neolithic people subsequently settlements waned considerably possibly due to further marine inundation combined with cold climate the present study shows that migration patterns of the neolithic settlements are closely associated with a gradually rising sea level between 7000 and 4000 yr ago

environmental significance of mid to late holocene sapropels in old man lake coorong coastal plain south australia an isotopic biomarker and palaeoecological perspective the holocene successions of numerous shallow lakes located along the coorong coastal plain in south australia attest to the impact of rising sea level and changing climate on their depositional environment old man lake is one of the smallest perennial alkaline lakes in the region its succession comprises a basal lagoonal sand rich in humic organic matter om overlain by a 3 7 m thick upward shoaling lacustrine mudstone the latter features three discrete sapropel units deposited between 3270 and 4910 cal yr bp a time of increasing aridity throughout southeastern australia a core taken from the lake s eastern margin yielded sedimentological mineralogical geochronological and micropaleontological data coring at five other sites across the lake provided sections of the humic and sapropelic facies n 20 for total organic carbon and rock eval analysis isotopic characterization of their micritic carbonate 13ccarb 18ocarb and co existing om 13corg and gc ms and gc irms analysis of their free aliphatic hydrocarbons for each sapropel event high productivity of diatoms and green algae was the principal driver of the accumulation and preservation of om in such high concentrations the precursor algal blooms were likely triggered by the influx of fresh water following winter rainfall the combination of kerogen hydrogen index and 13ccarb 13corg previously employed to track secular changes in algal productivity and organic preservation proved useful in identifying synchronous geographic differences in these processes across the lake highly branched isoprenoids hbi c25 1 c20 0 are prominent components of the aliphatic hydrocarbons in the sapropels confirming the significant contribution of diatoms to their om the c isotopic signatures of the principal c25 1 hbi isomer and the co occurring c23 c31 odd carbon numbered n alkanes further document the non uniformity of biomass preservation within and between the three sapropel units the evidence from this study suggests that seasonal algal blooms and meromixis although not necessarily an anoxic hypoliminion were required for sapropel formation in the holocene lakes of the coorong region higher resolution sampling dating and comparative analysis microfossil biomarker and isotopic of these sapropels is required to clarify their potential significance as palaeoclimate proxies

ionospheric response to 22 23 june 2015 storm as investigated using ground based ionosondes and gps receivers over india in this paper we present response of equatorial and low latitude ionosphere to 22 23 june 2015 geomagnetic storm using a chain of ground based ionosondes located at tirunelveli 8 73 n 77 70 e geomagnetic latitude 0 32 n hyderabad 17 36 n 78 47 e geomagnetic latitude 8 76 n and allahabad 25 45 n 81 85 e geomagnetic latitude 16 5 n along with a chain of gps receivers uniqueness of this storm is that in contrast to the equatorial plasma bubbles that were detected in the european sector we see suppression of plasma bubbles in the indian sector the observations suggest that westward penetration electric field during local midnight caused abrupt decrease of virtual height h f km to 200 km and suppressed plasma bubbles due to undershielding later the layer increased to 500 km simultaneously due to overshielding effect on 23 june we observed negative storm in the northern hemisphere while positive storm in the southern hemisphere in addition absence of equatorial es layers at tirunelveli and presence of f3 layer at tirunelveli hyderabad seem to be associated with equatorial electrojet eej counter electrojet cej variations however on 24 june we observed strong negative storm effects at allahabad hyderabad while positive storm effect at tirunelveli simultaneous enhancement of h f km at all three ionosonde stations at 20 30 ut on 23 june during recovery phase suggest eastward disturbance dynamo dd electric field that caused presunrise spread f at hyderabad allahabad but void of spread f at tirunelveli suggesting its midlatitude origin periodogram analysis of fof2 and h f km in the present analysis suggest the presence of shorter periods 2 h associated with dd electric field winds

hydrological changes facilitated early rice farming in the lower yangtze river valley in china a molecular isotope analysis the prosperity of neolithic rice agriculture along the yangtze river valley china under the humid east asian monsoon has been well documented however the way in which major hydrological changes influenced the expansion of rice farming remains elusive mainly because detailed climate records associated with critical periods of the development of early rice farming are still lacking here we present high resolution n alkane carbon 13 c and hydrogen d isotope data sampled every 5 cm from a 360 cm sedimentary sequence spanning an 5 k y period at the tianluoshan archaeological site in china s eastern coastal region combined with micropaleontological records our dual isotope data reveal a detailed climate change profile between 7 0 and 4 6 ka showing major hydrological changes that coincided with the early development of rice farming in the lower yangtze region two major evapotranspiration events indicated by synchronized positive 13 c and d shifts of as much as 5 13 c and 60 d are evident ca 7 0 ka and 6 4 ka and coincided with regional sea level changes our new isotope data suggest that these short drought climate conditions superimposed upon local sea level regressions opened suitable new habitats for expanding rice agriculture in the lower yangtze delta when subsequent humid climate regimes returned

the origin of pyrobitumens in upper devonian leduc formation gas reservoirs alberta canada an optical and eds study of oil to gas transformation pyrobitumens are common within deep basin devonian carbonate gas reservoirs of the western canada sedimentary basin incident light microscopy and sem eds have been used to study the origin of pyrobitumens from upper devonian isolated reefs of the leduc formation west central alberta reflectance properties romax and romin coke microtextures and relative s c ratios are used to classify the pyrobitumens in portions of reservoir units where nso enriched low aromaticity crudes may have been dominant oil to gas transformations produced mainly low reflecting isotropic to fine grained mosaic coke microtextures within the reservoir pyrobitumens type a in contrast where normal crudes were most likely dominant in the reservoir units prior to thermal cracking pyrobitumens with high bireflectance and very anisotropic coarse flow to domain cokes dominate type b oil to gas cracking within some of the reservoir units resulted in overpressuring and is represented by highly deformed pyrobitumens with fibrous coke textures and high bireflectance relative concentrations of type a and b pyrobitumens vary vertically and temporally in some of the reefal buildups the variations in the dominant pyrobitumen types are attributed to crude oil alteration which preceded crude oil to gas transformation e g tar mats in some zones whereas other zones may have been altered contemporaneously with crude oil cracking the later may have resulted from the oxidation and sulphur enrichment of the crude oil during thermochemical sulphate reduction this reaction is prevalent within devonian evaporite carbonate strata of the western canada sedimentary basin generating copious volumes of h2s the interaction between crude oil and sulphur enriched highly alkaline fluids is suggested by the presence of high s c very fine grained late stage calcined needle cokes within brecciated pyrobitumens

phytolith and diatom evidence for rice exploitation and environmental changes during the early mid holocene in the yangtze delta abstract using phytolith analysis from a well dated and high resolution sediment sequence in the apex of northern yangtze delta we investigate environmental changes the rise and decline of rice exploitation and possible impacts of environment on rice exploitation during the early mid holocene the phytolith sequence documents a relatively warm and dry interval during ca 9000 to 8200 cal yr bp followed by climatic amelioration before 7200 cal yr bp phytolith evidence indicates that rice exploitation at the apex of northern yangtze delta began at 8200 cal yr bp flourished by 7700 cal yr bp and ceased after 7400 cal yr bp the first emergence of marine diatom species approximately 7300 cal yr bp likely indicates an accelerated sea level rise the apparent correlation of the initiation of rice exploitation with climatic amelioration during the early mid holocene suggests that climatic changes may have played an important role in facilitating rice exploitation both the ideal climatic conditions and stable sea level enabled flourishing rice exploitation during 8200 to 7400 cal yr bp although the climate remained warm and wet after 7400 cal yr bp local sea level rise possibly led to the termination of earlier rice exploitation at this site of the northern yangtze delta

low latitude ionospheric thermospheric response to storm time electrodynamical coupling between high and low latitudes 1 using multi instrumental and multistation data we present low latitude ionospheric thermospheric behavior during the geomagnetic storm of 15 may 2005 the diurnal pattern of total electron content tec at a chain of equatorial to low latitude stations shows strong positive ionospheric storm on 15 may latitudinal variation of tec shows development of strong equatorial ionization anomaly eia on the same day evidence in terms of equatorial electrojet eej and magnetogram signatures is presented for the prompt penetration of interplanetary electric field ief as the cause of the positive ionospheric storm consequent to the storm time circulation resulting from the extra energy deposition via joule heating over high latitudes compositional changes occur in the global thermosphere tec enhancements on 16 may are attributed to enhancement of atomic oxygen at equatorial and low latitudes and the negative ionospheric storm on 17 may observed beyond certain low latitudes is explained in terms of enhancement of molecular species because of the storm time neutral composition changes strong esf plume structures on range time intensity rti map and l band scintillation and tec depletions in gps measurements are observed in the longitude sectors where the local time of sudden storm commencement ssc falls after the post sunset hours the ionospheric zonal electric fields are altered by the combined effects of eastward disturbance dynamo electric fields and direct prompt penetration of eastward electric fields associated with the northward turning of interplanetary magnetic field imf bz leading to subsequent development of esf after midnight

sedimentation rates in relation to sedimentary processes of the yangtze estuary china radioisotope analysis and digital elevation model dem method were combined to examine sedimentation rates and associated sedimentary processes in the yangtze river estuary the major depocenter is validated at the delta front sedimentary facies above the normal wave base nwb where accumulation exceeds erosion this alternated sedimentation does not accommodate pb 210 and cs 137 measurement although sedimentation rates of less than 0 2 5 0 cm yr 1 were recorded in the fine grained silty sediments which were interbedded with coarse grained sandy sediments however historical dem data provide more detailed information on sedimentation in the delta front facies where accumulation is dominant in the sandy shoals 1 73 8 30 cm yr 1 and delta front slope 5 22 cm yr 1 facies the dem data also show that erosion 1 61 7 32 cm yr 1 dominates in the northern estuarine distributaries and accumulation 3 01 4 97 cm yr 1 prevails in the southern ones primarily owing to the superimposed runoff and ebb tidal currents pb 210 and cs 137 measurements reveal sedimentation rate from 2 0 cm yr 1 to 6 3 6 6 cm yr 1 in the delta front slope facies which progressively decreases to 0 8 cm yr 1 in the prodelta facies and is unmeasurable in the delta shelf transition zone dem analysis detects minor erosion in the delta front slope and prodelta facies although accumulation predominates there the present sedimentological database will be useful for estuarine environmental assessment after the three gorges dam is completed in 2009

organic geochemistry of the pine point lead zinc ore field and region northwest territories canada middle devonian barrier complex within the pine point lead zinc ore field located within the immature to marginally mature zone with respect to petroleum generation certain of the host rocks of the ore field were deposited in highly reducing conditions such that organic matter of algal or microbial origin has been preserved to a remarkable degree yields of extractable soluble material relative to organic carbon are extremely high which has resulted in the local migration of immature bitumens and heavy oil within the shallow regime polymerization of nitrogen sulfur and oxygen compounds and asphaltenes biodegradation of bitumens is a relatively late process the question of a genetic relationship between lead zinc sulfide and organic matter remains open modified journal abstract

effects of prolonged southward interplanetary magnetic field on low latitude ionospheric electron density the present work describes the low latitude ionospheric variability during an unusually prolonged 33 h geomagnetically disturbed condition that prevailed during 15 16 july 2012 the low latitude electron density in summer hemisphere investigated using ground and satellite based observations responded to this by generating strong negative ionospheric storm on 16 july the maximum electron density on 16 july over indian low latitudes was reduced by more than 50 compared to that on a geomagnetically quiet day 14 july 2012 in contrast to the extreme reduction in total electron content tec in the northern hemisphere tec from a winter hemispheric station revealed substantial 23 total electron content unit 1 tecu 1016 el m 2 enhancements on the same day this contrasting hemispherical response in tec is suggested to be due to the combined effects of strong interhemispheric and solar driven day night winds further very weak equatorial electrojet eej strength on 16 july indicated that the westward electric field perturbations in the low latitude ionosphere were possibly due to the disturbance dynamo effect associated with meridional circulation from polar to equatorial latitudes interestingly despite reduction in the integrated eej strength on 15 july the low latitude electron density showed substantial enhancement highlighting the significant effect of the positive ionospheric storm on the low latitude ionosphere the roles of electrodynamical neutral dynamical and compositional disturbances are discussed in view of these observations to understand low latitude ionospheric response when geomagnetic disturbance persists for longer duration

the c20 highly branched isoprenoid biomarker a new diatom sourced proxy for summer trophic conditions abstract the exact biological source of the c20 highly branched isoprenoid hbi present in sediments from aquatic systems is unclear we therefore examined the relationship between the distribution of fossil diatoms and the concentration of the c20 hbi in a late glacial sedimentary record from the hasseldala port paleolake in southern sweden using bayesian multiple linear regression analysis we show that its concentration is linked primarily to the production of the diatom taxon gomphonema acuminatum which accounts for the largest proportion of the temporal variability in the biomarker by analogy with modern observations we argue that an increasing amount of g acuminatum biomass in our sedimentary record reflects increasing oligotrophy in the paleolake during the summer growing season especially at times defined by subdued hydrologic flow our conclusions are corroborated by the 13c composition of the c20 hbi biomarker which points to a negative photosynthetic fractionation between atmospheric co2 and the pool of dissolved inorganic carbon during diatom bloom a distinct phenomenon at times of inhibited hydrological flow accordingly we suggest that the c20 hbi biomarker can be effectively used to reconstruct the trophic state of the paleolake at hasseldala port while its stable isotope composition can provide physicochemical information about the lake conditions during the dry summer season moreover we note that the major hydrological shifts recorded in the g acuminatum c20 hbi stratigraphy do not coincide with the pollen zone boundaries we thus infer that aquatic and terrestrial environmental responses to climate change are substantially decoupled through the hydrological system which highlights the necessity for multi proxy investigations to decipher past climate events

mid holocene coastal hydrology and salinity changes in the east taihu area of the lower yangtze wetlands china abstract during the mid holocene the eastern taihu area on china s yangtze delta plain was populated by advanced late neolithic cultures supported by intensive domesticated rice cultivation this agricultural system collapsed around 4200 cal yr bp with severe population decline the end of the liangzhu culture and about half a millennium of very low scale human activity in the area before the re establishment of agricultural production microfossil analyses from six sedimentary sequences supported by ams 14c dating has allowed reconstruction of mid holocene hydrological conditions and salinity changes which would have had a major influence on agricultural viability and cultural history in the coastal wetlands these data allied to existing stratigraphic and sea level records show that chenier ridges that developed after ca 7000 cal yr bp in the east of the area sheltered it from marine inundation and although still connected to the sea through tidal creeks low salinity conditions persisted throughout the neolithic period there is no evidence that marine flooding caused the collapse of liangzhu culture marine influence was stable and evolved slowly social and cultural causes may also have been important but if environmental change triggered the collapse of neolithic agricultural society here other natural forces must be sought to explain this event

thermal alteration of gilsonite due to bushfire an example from southwest iran abstract heat affected fragments of bitumen with distinctive properties which can be interpreted as being produced by local heating were found in gilsonite deposits in the vicinity of an asphaltic pool southwest iran the coke fragments consist of multi phase isotropic to anisotropic thermally altered fragments the morphology of the coke fragments is described and an attempt is made to correlate these fragments with laboratory carbonized products of natural bitumen the presence of natural coke in bitumen deposits suggests redeposition of coke following its initial production the formation of natural bitumen coke probably resulted from heat generated by bushfire s in the area in recent times

was magnetic storm the only driver of the long duration enhancements of daytime total electron content in the asian australian sector between 7 and 12 september 2017

occurrences and origin of reservoir solid bitumen in sinian dengying formation dolomites of the sichuan basin sw china abstract reservoir solid bitumen is pervasive throughout the sinian dengying formation dolomites of the sichuan basin and neighboring areas yet its origin remains controversial optical and scanning electron microscope sem studies of the dengying formation were carried out to elucidate the nature and origin of the solid bitumen solid bitumen in dissolution pores intercrystal pores and stylolites appears to have formed in association with regional hydrocarbon charging processes reservoir solid bitumen displays a variety of morphologies each of which appears to reflect different precursor hydrocarbons massive crust like solid bitumen was probably derived from solid precursors whereas finger like solid bitumen likely evolved from liquid precursors sheet like and thin skinned globular solid bitumen appeared to have precipitated from wet gas precursors analyzed solid bitumen is characterized by high random reflectance average 3 4 and bireflectance values 4 2 6 9 exhibits strong optical anisotropy and displays different coke structures including granular mosaic domain and fibrous the coke textures which appear to reflect the nature of bitumen precursors formed by physical coalescence of mesophase spheres and parallel arrangement of laminated aromatic sheets in association with a rapid heating event the inferred thermal episode which is evidenced by the presence of hydrothermal minerals including saddle dolomite quartz authigenic illite and barite may have been associated with the late permian eruption of the emeishan traps thus widespread solid bitumen in the dengying formation reflects the effects of hydrothermal alteration rather than the impact of normal burial related thermal maturation further the close association of sold bitumen and authigenic kaolinite indicates that natural deasphalting plays a role in the formation of reservoir solid bitumen

upward decrease of organic c n ratios in the okinawa trough cores proxy for tracing the post glacial retreat of the continental shore line abstract six piston cores were collected along the nw se line in the okinawa trough close to the chinese continental shelf edge and dated by 23 ams 14 c measurements along with planktonic 18 o stratigraphy and an ash layer dated as 6 3 ka on a time scale to 19 ka the ratio of total organic carbon to total nitrogen concentration c n ratio displays gradual decreases toward the present and suggests the decrease of vascular plant fragment input to the trough from continental rivers this suggestion is confirmed by similar decreases of lignin phenol content and ratio of c 28 fatty acid to c 16 fatty acid content in core rn93 pc3 the gradual decrease of land plant fragment input is interpreted to be a consequence of the retreat of the continental coastline during the deglacial period

rising waters new geoarchaeological evidence of inundation and early agriculture from former settlement sites on the southern yangtze delta china new pollen phytolith charcoal and diatom data from 14c ams dated sediments from three clusters of former occupation sites on the southern yangtze delta liangzhu majiabang and chuodun reveal

organic petrography of graptolite fragments from turkey abstract the reflectance and bireflectance of graptolite fragments silurian ordovician from southeast turkey were examined and the morphology was described using reflected light microscopy the dispersion of maximum and minimum reflectance of graptolites sectioned parallel and perpendicular to the bedding was also determined the graptolites were anisotropic and the anisotropy was stronger for sections perpendicular to the bedding the graptolite fragments show two types of surface morphology granular and non granular the granular type had a rough surface and granular anisotropy the non granular fragments showed a smooth surface and basic anisotropy the fine internal structure of graptolite was evident under crossed polars the reflectance of graptolite increased with depth and was higher than other organic material e g bitumen found in the same sediment the present study indicates that the reflectance of graptolite in sediment can be used to determine the maturity of the dediment

the biogeochemical evolution of the coorong during the mid to late holocene an elemental isotopic and biomarker perspective since the mid 1990s the coorong a 130 km long coastal wetland of international importance in southeastern south australia has undergone serious decline due largely to prolonged drought and reduced inflows of surface and ground water from its hinterland tenuously connected to the ocean at its northern extremity it is effectively separated into two lagoons by a narrow channel at its mid point the southern part is now permanently hypersaline here we report the results of an attempt to track the biogeochemical status of the estuary over the last 5000 years employing a consortium of elemental isotopic and biomarker parameters the sediment samples analysed came from two cores each 6 7 m in length retrieved from sites located halfway along the present day northern and southern lagoons the sediments at the southern locality are richer in total organic carbon and total nitrogen than those in the northern core reflecting higher net deposition of organic matter om and nutrients in the southern lagoon comparison of the d 13 corg and d 15 n profiles of the two cores reveals that the lower reaches of the coorong have always been a restricted o2 depleted water body that is both more saline and prone to more intensive denitrification of no 3 aq than the northern lagoon prominent among the aliphatic hydrocarbons preserved in the sediments of the southern lagoon are the c20 highly branched isoprenoid hbi 2 6 10 trimethyl 7 3 methylbutyl dodecane a putative marker of epiphytic diatoms and c15 c35 n alkanes with a marked odd even predominance in the c21 range these and other biomarkers are consistent with om derived from a mixed population of algae cyanobacteria and other eubacteria 13 c nmr spectra confirm that this om is largely algal derived but with a significant contribution from the seagrass ruppia megacarpa and possibly other aquatic macrophytes particularly in pre european sediments the c isotopic signature of the hbi alkane is consistently heavier than those of the c23 c 25 c 27 and c29 n alkanes presumably from planktonic chlorophytes aquatic metaphytes which in turn are heavier than the coexisting even carbon numbered homologues of likely bacterial origin with decreasing age these biomarker alkanes display an overall increased depletion in 13 c and enrichment in d trends that have accelerated over recent decades as the south lagoon has become progressively more hypersaline and ecologically impoverished however coeval negative excursions in the dd profiles of the epiphyte marker and n alkanes along with coincident diatom inferred reductions in palaeosalinity together highlight a series of hitherto unrecognised freshening events attributable to enhanced inflow of surface runoff and shallow groundwater

a unique middle pleistocene beech fagus rich deciduous broad leaved forest in the yangtze delta plain east china its climatic and stratigraphic implication abstract pollen analysis of middle pleistocene sediments from the yangtze delta plain provides a paleoecological reconstruction and has implications for stratigraphic correlation in east china the pollen assemblage is characterized by high values of fagus 16 8 on average which is unusual because fagus is generally present only sporadically in other lowland quaternary pollen records from the region in addition to fagus the assemblage has a rich diversity of broad leaved deciduous trees including quercus ulmus carpinus ostrya juglans betula and liquidambar as well as conifers including pinus picea abies larix and tsuga thus the pollen flora suggests a broad leaved deciduous forest mixed with abundant conifers which developed under cooler and more humid conditions than present the stable pollen sequence throughout the studied section suggests a stable environment beech forests also characterize the middle pleistocene of taiwan and japan and thus may be a stratigraphic indicator of the middle pleistocene in east asia the yangtze delta plain may have been an important refugium for the last survival of fagus in the lowlands

alteration of solid bitumen by hydrothermal heating and thermochemical sulfate reduction in the ediacaran and cambrian dolomite reservoirs in the central sichuan basin sw china abstract solid bitumen in reservoir rocks is an allochthonous organic matter formed from bitumen or liquid hydrocarbons by various alteration processes in this study two types of altered solid bitumen have been identified in both the ediacaran dengying and cambrian longwangmiao formations in the central sichuan basin using petrographic microthermometric chemical and isotopic data the hydrothermally altered bitumen type 1 is associated with the pore filling saddle dolomite and quartz in which homogenization temperatures of some fluid inclusions are more than 10 c higher than the maximum burial temperature of the dengying formation it has various anisotropic textures with significantly high bireflectance values rbmax rbmin between 3 89 and 9 21 moreover the hydrothermal alteration led to 13c enrichment in the type 1 bitumen compared to the normally matured bitumen derived from the same source on the other hand the thermochemical sulfate reduction tsr altered bitumen type 2 has s c atomic ratios of up to approximately 0 06 the 34s values of type 2 bitumen are close to those of the carbonate associated sulfate and similar to the tsr derived h2s in the same reservoirs a strong negative correlation exists between s c atomic ratios and 13c values in the type 2 bitumen in the dengying formation which is interpreted as a result of an increasing incorporation of the 13c depleted ethanethiol into the bitumen during tsr this interpretation is consistent with the fact that the remaining ethane became isotopically heavier as tsr proceeded in addition the reactive sulfate for tsr was primarily derived from the hydrothermal sulfate such as barite this is evidenced by the replacement of hydrothermal barite by the 34s enriched pyrite and the small differences in 34s value between the barite and the type 2 bitumen or the tsr derived h2s in the same strata we suggest that tsr in the ediacaran and cambrian hydrocarbon reservoirs was probably initiated by hydrothermal activity

the transition to overshielding after sharp and gradual interplanetary magnetic field northward turning overshielding is referred to a shielding status during which the dawnward shielding electric field dominates over the duskward penetration electric field in the inner magnetosphere typically appearing when the interplanetary magnetic field imf suddenly turns northward after a prolonged southward orientation it is expected that the transition to overshielding after imf northward turning can be affected by the shape of northward turning sharp or gradual moreover the initial shielding status undershielding or goodshielding prior to the transition may also have influence on the transition here we analyze two groups of cases in which the transitions appear after sharp duration less than 5 min and gradual duration more than 30 min northward turning each group includes two cases in which the transition initiated from undershielding and goodshielding these cases show that 1 the beginning of the transition to overshielding coincides with sharp imf northward turning but appears in the midst of gradual imf northward turning 2 the transition from goodshielding to overshielding is always associated with convection electric field drop and or polar cap shrinkage regardless of the shape of imf northward turning and 3 the typical solar wind condition in which the imf suddenly turns northward after a prolonged southward orientation is neither a necessary condition nor a sufficient condition for overshielding furthermore we will discuss the effect of substorm processes on overshielding