seismo ionospheric coupling appearing as equatorial electron density enhancements observed via demeter electron density measurements we report the processes and results of statistical analysis on the ionospheric electron density data measured by the detection of electro magnetic emissions transmitted from earthquake regions demeter satellite over a period of 6 years 2005 2010 in order to investigate the correlation between seismic activity and equatorial plasma density variations to simplify the analysis three equatorial regions with frequent earthquakes were selected and then one dimensional time series analysis between the daily seismic activity indices and the equatorial ionization anomaly eia intensity indices which represent relative equatorial electron density increase were performed for each region the statistically significant values of the lagged cross correlation function particularly in the region with minimal effects of longitudinal asymmetry indicate that some of the very large earthquakes with m 5 0 in the low latitude region can accompany observable precursory and concurrent eia enhancements even though the seismic activity is not the most significant driver of the equatorial ionospheric evolution the physical mechanisms of the seismo ionospheric coupling is consistent with our observation and the possibility of earthquake prediction using the eia intensity variation is discussed

holocene storage of siliciclastic sediment around islands on the middle shelf of the great barrier reef platform north east australia thick sequences of sediment surround the whitsunday islands on the middle shelf of the great barrier reef gbr platform much of this sediment is siliciclastic material deposited since the sea level highstand at around 6 5 ka this raises a mass balance dilemma because modern terrigenous discharge to the gbr platform is restricted to the inner shelf shallow seismic profiles and sediment samples were collected over 450 km2 around the whitsunday islands to quantify the mass of siliciclastic sediment for a dynamic model of the shelf the sea floor and pre holocene surfaces were mapped using 4584 stations along the seismic profiles and a graphical computer program the total volume of sediment between these two surfaces is 3 67 0 45 109 m3 this volume is composed of buried reefs 0 13 0 01 109 m3 medium 0 70 0 30 109 m3 and fine grained shoals 2 84 0 35 109 m3 the volume estimates combined with measurements of carbonate concentration density and porosity indicate that 1850 380 mt of holocene siliciclastic sediment surround the whitsunday islands in medium 510 225 mt and fine grained shoals 1340 155 mt the total mass of siliciclastic material is 1 7 2 6 times that stored in cleveland bay a similar sized repository on the inner shelf a simple numerical model has been constructed to explain this large quantity of holocene siliciclastic sediment the model results in the appropriate siliciclastic mass next to the whitsunday islands by integrating regional shelf processes over time unlike the present day rivers discharged sediment to the middle shelf during the early holocene this material was subsequently focused by northward transport into the vicinity of the islands a geomorphologically complex region that serves as a sediment trap although direct riverine inputs to the middle shelf have stopped during the present sea level highstand previously deposited siliciclastic sediment is continually being winnowed from the middle shelf and redeposited next to the whitsunday islands the transport and distribution of siliciclastic sediment on the gbr platform is thus influenced significantly by storage around islands on the middle shelf

controls on focused flow and dispersed flow deepwater carbonates miocene agua amarga basin spain abstract common models for carbonate slope or basin margin sedimentation emphasize the contrasts between linear sediment sources and point sediment sources geologic mapping and high resolution stratigraphic study of a set of miocene outcrops exceptional for their three dimensional exposure and preservation of paleotopography demonstrates that paleotopographic focus or lack thereof may be a dominant control on geometries and sediment character of sediment gravity flow deposits in line sourced systems in the agua amarga basin se spain basin topography is initially modified by subaerial exposure and erosion of volcanic basement to form paleovalley systems after late miocene marine inundation topography is partially modified by infilling of high energy shallow water heterozoan deposits units 1 and 2 that subdued topography in one area to produce a ramp like surface but did not significantly infill a large paleovalley located in another area further relative rise in sea level resulted in an extensive reefal platform that formed along a paleo high adjacent to both features la rellana platform subsequent sediment gravity flow deposits shed from this reefal platform followed two pathways down the ramp like surface dispersed flow or into the large flooded paleovalley focused flow deposits within each system display contrasting lithofacies architectures these deepwater deposits units 3 7 in this study consist of carbonate breccia facies coarse facies graded skeletal packstone facies coarse facies and planktonic foraminifera rich facies fine facies that are interpreted as sediment gravity flow deposits and pelagic sediments relative sea level fluctuations resulted in deepwater facies variations in the large paleovalley as a result of significant backstepping and progradation of the rellana reefal platform on a gently sloping surface fining of basinal deposits and shelfward migration of the locus of deposition for sediment gravity flows is associated with sea level rise coarsening of basinal deposits and basinward migration of the locus of deposition for sediment gravity flows is associated with stillstand and relative fall in sea level both relationships demonstrate a direct link between the locus of reefal platform growth and style of basin sedimentation early parts of relative rises in sea level late parts of highstands and falling stages led to transport of abundant coarse sediment into the basin focused flow deposits were line sourced and funneled into the axis of a large margin parallel paleovalley and confined to a channel volume ratio of coarse facies to fine facies is estimated at 0 7 deposits in proximal paleovalley locations display compensation geometries around positive relief on debrites channelization erosional truncation lapout against paleovalley walls and some drape as a result of lateral confinement and proximity to the sediment source deposits in distal paleovalley locations display increasingly tabular geometries as a result of decreasing lateral confinement and concentration of coarse grained sediment gravity flows down depositional dip dispersed flow deposits were line sourced into the basin along a gently inclined ramp like surface that lacked paleotopographic focus volume ratio of coarse facies to fine facies is estimated at 0 1 the less complex sheet like depositional geometries and locations of these deposits result from the absence of lateral confinement and subtle changes in substrate slope focused flow sediment gravity flow deposits that are confined by topographic elements such as channels are most likely to form sizeable accumulations of coarse facies with characteristics most appropriate for conventional oil and gas exploration there are many paleotopographic configurations that can lead to focusing of flows so this deepwater carbonate system may be more common than previously recognized

anatomy of the buried burdekin river channel across the great barrier reef shelf how does a major river operate on a tropical mixed siliciclastic carbonate margin during sea level lowstand abstract a large palaeochannel on the northeastern australian continental shelf has been imaged by a series of shallow seismic reflection profiles the buried channel forms an important pleistocene route of the burdekin river and extends almost continuously for 160 km from the present coast to the outermost reef the channel floor profile steps across the shelf with alternating segments of gentle gradient flats and steeper gradient ramps channel sinuosity as interpreted from seismic records varies among segments between 1 and 1 72 with no consistent relationship between sinuosity and gradient the lower and upper parts of the channel fill have different geometry and reflection character suggesting channel excavation and initial filling occurred during a different regime than final filling in one section of the shelf about the 50 m isobath the channel is difficult to define and appears to have wandered significantly either because it has been modified by shoreface erosion ca 10 5 ka or because the river encountered a change in topography in front of karstified reefs as the channel passes between the numerous outer shelf reefs in water depths of 70 80 m it becomes progressively smaller conspicuously underfilled and absent entirely over the outermost 10 km of the shelf no discrete lowstand river mouth could be recognised on the present shelf edge the elevations of flat segments on the channel floor profile show considerable similarity to published elevations of stillstands or brief rises in sea level attained during the long term drawdown associated with the last glacial cycle 125 20 ka and are interpreted to have formed during this stepwise drop in sea level channels were cut and partially filled during the fall and lowstand and then backfilled during the holocene transgression the ancestral channel of the burdekin river therefore preserves a rare insight into the stratigraphic record of falling sea level during the last glacial

a statistical investigation of preearthquake ionospheric anomaly 1 empirical evidence of the preearthquake ionospheric anomalies peias is reported by statistically investigating the relationship between variations of the plasma frequency at the ionospheric f2 peak fof2 and 184 earthquakes with magnitude m 5 0 during 1994 1999 in the taiwan area the peia defined as the abnormal decrease more than about 25 in the ionospheric fof2 during the afternoon period 1200 1800 lt significantly occurs within 5 days before the earthquakes moreover the odds of earthquakes with peia increase with the earthquake magnitude but decrease with the distance from the epicenter to the ionosonde station these results indicate that the peia is energy related

ionospheric electron enhancement preceding the 2011 tohoku oki earthquake 1 the 2011 march 11 tohoku oki earthquake mw9 0 caused vast damages to the country large events beneath dense observation networks could bring breakthroughs to seismology and geodynamics and here i report one such finding the japanese dense network of global positioning system gps detected clear precursory positive anomaly of ionospheric total electron content tec around the focal region it started 40 minutes before the earthquake and reached nearly ten percent of the background tec it lasted until atmospheric waves arrived at the ionosphere similar preseismic tec anomalies with amplitudes dependent on magnitudes were seen in the 2010 chile earthquake mw8 8 and possibly in the 2004 sumatra andaman mw9 2 and the 1994 hokkaido toho oki mw8 3 earthquakes but not in smaller earthquakes

sediment flux across the great barrier reef shelf to the queensland trough over the last 300 ky the continental margin off northeast australia comprising the great barrier reef gbr platform and queensland trough is the largest tropical mixed siliciclastic carbonate depositional system in existence we describe a suite of 35 piston cores and two ocean drilling program odp sites from a 130 240 km rectangular area of the queensland trough the slope and basin setting east of the central gbr platform oxygen isotope records physical property magnetic susceptibility and greyscale logs analyses of bulk carbonate content and radiocarbon ages at these locations are used to construct a high resolution stratigraphy this information is used to quantify mass accumulation rates mars for siliciclastic and carbonate sediments accumulating in the queensland trough over the last 31 000 years for the slope highest mars of siliciclastic sediment occur during transgression 1 0 million tonnes per year mt yr 21 and lowest mars of siliciclastic 0 1 mt yr 21 and carbonate 0 2 mt yr 21 sediment occur during sea level lowstand carbonate mars are similar to siliciclastic mars for transgression and highstand 1 1 1 4 mt yr 21 in contrast for the basin mars of siliciclastic 0 0 1 mt yr 21 and carbonate sediment 0 2 0 4 mt yr 21 are continuously low and within a factor of two for lowstand transgression and highstand generic models for carbonate margins predict that maximum and minimum carbonate mars on the slope will occur during highstand and lowstand respectively conversely most models for siliciclastic margins suggest maximum and minimum siliciclastic mars will occur during lowstand and transgression respectively although carbonate mars in the queensland trough are similar to those predicted for carbonate depositional systems siliciclastic mars are the opposite given uniform siliciclastic mars in the basin through time we conclude that terrigenous material is stored on the shelf during sea level lowstand and released to the slope during transgression as wave driven currents transport shelf sediment offshore q 2000 elsevier science b v all rights reserved

mixing of siliciclastic and carbonate sediments in shallow shelf environments the inhibiting effect that siliciclastic material has on carbonate secreting organisms has lead to the generalization that sediments composed of mixtures of carbonate and siliciclastic material should rarely form however many modern and ancient shelf deposits contain a spectrum of sediments that are of mixed composition the processes responsible for this mixing can be grouped into four categories 1 punctuated mixing where sporadic storms and other extreme periodic events transfer sediments from one depositional environment to another 2 facies mixing where sediments are mixed along the diffuse boundaries between contrasting facies 3 in situ mixing where the carbonate fraction consists of the autochthonous or parautochthonous death assemblages of calcareous organisms that accumulated on or within siliciclastic substrates and 4 source mixing where admixtures are formed by the uplift and erosion of nearby carbonate source terranes the allochemical constituents of mixed sediments are both coralgal and foram mollusc in composition the foram mollusc assemblage is the most common because of the effects of increased turbidity unstable substrates and the clogging of filter feeding mechanisms associated with a siliciclastic influx

quaternary reef response to sea level and environmental change in the western atlantic the tropical subtropical western atlantic realm harbours abundant fringing reefs two major barrier reefs belize florida several atolls and large reef fringed carbonate platforms bahamas data from belize and south florida indicate that major barrier reefs were established during the high sea levels of the long and warm marine isotope stage 11 reefs formed during pleistocene sea level highstands whereas erosion non deposition and the formation of subaerial exposure surfaces prevailed during lowstands of sea level florida bahamas exposed reefs and platforms with siliciclastic hinterlands were characterized by deposition of clays and sands on fluvial plains belize elevated terraces and outcrops of reefs of the last interglacial of marine isotope stage 5e are evidence of higher than present sea level and temperature that sustained large reef fringed carbonate platforms and ramps in the florida bahamas region and central america belize mexico including ooid deposition in warm and shallow waters during the highstands of marine isotope stages 5c and 5a at sea levels several metres lower than today fringing reefs developed in parts of the caribbean for example in south florida outlier reefs data from the island of barbados support the contention that the postglacial sea level rise from about 120 m was rapid and punctuated by two meltwater pulses ia and ib which bracket the beginning and end of the younger dryas respectively after reflooding of shelves in the early holocene reefs developed preferentially on highs of the underlying karstified pleistocene limestone surface and on former river channel bars many reefs in the western atlantic region kept pace with holocene sea level rise whereas some were drowned reasons for reef drowning are debated and include sea level rise elevation of antecedent topography and deterioration of environmental conditions such as high nutrient input apart from sea level and antecedent topography factors such as exposure to waves and currents storms and sedimentation have controlled reef development the historical decline of acroporid corals in the caribbean realm has been attributed to cooling following the holocene thermal optimum however historical die offs of reef building corals and other reef organisms suggest that some if not all recent declines were unprecedented during the holocene rising temperatures decreasing carbonate saturation increased frequency of major storms high nutrient concentrations and sedimentation overfishing and disease certainly played a role in decline but systematic studies relating these environmental factors to holocene reef building are only in the early stages

lithology based sequence stratigraphic framework of a mixed carbonate siliciclastic succession lower cretaceous atlantic coastal plain this study presents a lithology based sequence stratigraphic framework and depositional model for lower cretaceous mixed siliciclastic carbonate sediments of the mid atlantic coastal plain eastern united states lithologic data from cores and cuttings were integrated with wireline logs and two dimensional seismic data to document lithofacies variability and stacking patterns across the albemarle basin of eastern north carolina ten facies associations are defined which are variably present within siliciclastic and carbonate dominated depositional profiles interpreted to extend from onshore lowland coastal plain to deep shelf depositional environments three depositional sequences 0 1 2 were identified each with component upward shoaling parasequences seismic reflectors typically coincided with key sequence stratigraphic surfaces which guided correlations between wells parasequences are grouped into parasequence sets with progressive progradational or retrogradational highstand and transgressive systems tracts respectively stacking patterns transgressive parasequences are thinner uniform in thickness and tend to be more dominated by molluskan carbonate facies highstand parasequences have more variable thickness are siliciclastic dominated and tend to be progradational on seismic data late highstand deposits of sequence 1 are dominated by restricted carbonate facies that likely reflect increased aridity lowstand deposits were not recognized from onshore well and seismic data the sequence stratigraphic framework developed documents the complex spatial and temporal facies relationships within a wave dominated mixed carbonate siliciclastic passive margin succession the strata studied document the complex interplay of lithofacies within a transition zone between near shore carbonate dominated strata to the south southeast georgia embayment and siliciclastic dominated marginal marine successions to the north baltimore canyon trough it also provides a useful stratigraphic calibration set for coeval offshore sediments that have been identified as potential areas for hydrocarbon exploration

holocene depositional history of the burdekin river delta of northeastern australia a model for a low accommodation highstand delta abstract the burdekin river of northeastern australia has constructed a substantial delta during the holocene delta plain area 1260 km2 the vertical succession through this delta comprises 1 a basal coarse grained transgressive lag overlying a continental omission surface overlain by 2 a mud interval deposited as the coastal region was inundated by the postglacially rising sea in turn overlain by 3 a generally sharp based sand unit deposited principally in channel and mouth bar environments with lesser volumes of floodplain and coastal facies the holocene burdekin delta was constructed as a series of at least thirteen discrete delta lobes formed as the river avulsed each lobe consists of a composite sand body typically 5 8 m thick the oldest lobes formed during the latter stages of the postglacial sea level rise 10 5 5 kyr bp are larger than those formed during the highstand 5 5 3 kyr bp which are in turn larger than those formed during the most recent slight sea level lowering and stillstand 3 0 kyr bp radiocarbon ages and other stratigraphic data indicate that inter avulsion period has decreased through time coincident with the decrease in delta lobe area the primary control on holocene delta architecture appears to have been a change from a pluvial climate known to characterize the region 12 4 kyr bp to the present drier enso dominated climate in addition to decreasing the sediment supply via lower rates of chemical weathering this change may have contributed to the shorter avulsion period by facilitating extreme variability of discharge more frequent avulsion may also have been facilitated by the lengthening of the delta plain channels as the system prograded seaward

rock burst process of limestone and its acoustic emission characteristics under true triaxial unloading conditions abstract the rock failure process is associated with acoustic emission ae hence violent rock failure processes such as rock burst under different stress paths in laboratory can be studied using the ae monitoring technique in this paper single face dynamic unloading tests under true triaxial condition were carried out for paleozonic marine sedimentation limestone samples produced by blocks cored from 1140 m depth in jiahe coal mine of china frequency spectra analysis was conducted for the full wave ae data and figures showing the relationship of frequency amplitude of ae signals in rock burst stages were obtained the dynamical damage process and characteristics of limestone under the test condition are summarized it is found from the fast fourier transformation fft analysis of the ae signals that there exist two main frequency ranges i e lower 60 100 khz and higher 170 190 khz for the samples when the limestone samples are under relatively lower stress the ae signals are characterized by high frequency and low amplitude as the stress increases the ae signals tend to shift more towards a signature of high amplitude near the bursting failure of the rock samples it is observed that there are much higher amplitude and lower frequency events the ae accumulated energy release rapidly increases from the unloading state of the rock samples to its failure the dynamic unloading test facility provides a useful tool to gain an insight into the characteristics of rock bursts

statistical analysis of an ionospheric parameter as a base for earthquake prediction 1 this paper is related to the use of ionospheric density variations to tentatively predict earthquakes the results of this statistical analysis are presented as a function of various parameters the ion density was recorded by the low altitude satellite demeter during more than 6 years and a search for anomalies was automatically conducted with the complete data set in a second time a software checked if each anomaly could correspond to an earthquake the search was conducted at less than 1500 km from the anomaly positions and until 15 days after the anomaly time the earthquakes have been classified depending on their magnitude depth and position below the sea or inland this attempt to predict earthquakes of course generates a lot of false alarms and wrong detections nevertheless it is shown that the number of good detections increases with the magnitude of the earthquakes in average the number of perturbations is higher the day of the earthquake and then smoothly decreases for the days before earthquakes below the sea are better detected there are seismic areas close to the south atlantic magnetic anomaly and at high latitudes where the number of natural perturbations is too important to expect a high number of good detections finally when there are several perturbations corresponding to a single earthquake it is possible to combine their positions to have a better estimation of the location of the future epicenter however uncertainties about the time and the magnitude are large

mixed carbonates and siliciclastics in the quaternary of southern belize pleistocene turning points in reef development controlled by sea level change the belize barrier and atoll reefs represent one of the largest reef structures in the atlantic ocean the southern shelf of belize is a classic location of a modern mixed carbonate siliciclastic system whereas knowledge of the holocene deposits in the area is extensive data on the pleistocene system are fragmentary open questions include i the nature of the reef foundations carbonate versus siliciclastics ii the ages of the deposits including the initiation of the barrier reef and iii the response of the mixed system to sealevel fluctuations the results of a study of borings on the southern belize shelf are presented here six up to 105 m long borings were made to better understand the history of this important mixed system uranium series dating in the pleistocene was not possible because of diagenetic alteration however lithostratigraphy strontium isotopes and calcareous nannofossil biostratigraphy were used to constrain stratigraphic ages results support the contention that the quaternary development in belize was quite similar to that of other major barrier reefs such as the florida reef tract and further afield the great barrier and the new caledonian barrier reefs all of these barrier reefs are mixed carbonate siliciclastic systems and significant reef growth only began after the onset of high amplitude eccentricity controlled sea level changes and as late as during the exceptionally long and warm marine isotope stage 11 some 400 ka in belize early pleistocene sections at bases of borings include mollusc rich wackestones rare coral packstones and marls which were deposited under low to moderate energy conditions in a ramp setting before ca 900 ka during the high sea levels of marine isotope stage 25 and possibly earlier marine isotope stage 31 or 37 the belize shelf was subaerially exposed for most of the mid pleistocene and was dominated by siliciclastic sedimentation possibly during marine isotope stages 24 to 12 when highstands were comparatively low continuous reefs at the shelf margin were developing during highstands in the late pleistocene beginning with the long and high highstand of marine isotope stage 11 some 400 ka the southern shelf was flooded entirely and carbonates started to dominate once more reefs developed on top of siliciclastic deposits on the shelf a continuous barrier reef came into existence and largely developed on top of carbonates at the shelf margin during late pleistocene lowstands siliciclastics presumably no longer reached the shelf margin because of the topographic high of the barrier reef platform the quaternary belize example may serve as a model for reconstructing ancient mixed systems in icehouse worlds however any extrapolations are limited by the fact that fast growing scleractinian reef builders had not yet evolved in the palaeozoic

siliciclastic sediment across the north queensland margin australia a holocene perspective on reciprocal versus coeval deposition in tropical mixed siliciclastic carbonate systems abstract according to conventional models of reciprocal sedimentation for tropical mixed siliciclastic carbonate systems shedding of carbonate material dominates slope and basin sedimentation during transgression and highstand while siliciclastic deposition dominates during lowstand this understanding permeates the stratigraphic literature and is the accepted depositional model on the great barrier reef gbr margin the results of this study however document coeval carbonate and siliciclastic highstand deposition on the gbr slope and basin seafloor sediment from queensland trough slopes and basin floor east of the gbr contains 20 to 50 terrigenous siliciclastic material one hundred and twenty six sediment samples were obtained from core tops and sediments grabs previously retrieved from shelf slope and basin environments of the north queensland margin these samples were analyzed for their carbonate content mineralogy and major element composition the amount of terrigenous siliciclastic material in sediment from the north queensland margin can be approximated by three independent methods 1 the noncarbonate residual 2 the sum of quartz clays and feldspars and 3 the sum of sio2 al2o3 fe2o3 and tio2 all three tracers show a distinct distribution of siliciclastic sediment across the margin shelf siliciclastic content is highest on the inner shelf decreasing eastward toward the gbr with the exception of relatively high siliciclastic content in several interreef passages queensland trough siliciclastic content is highest on the slope and basin between 15 and 17 s latitude decreasing to the south and east although the relative abundances of quartz and clay minerals vary across the margin the chemistry suggests a similar origin for the siliciclastic material moreover the zone of high siliciclastic abundance in queensland trough reflects enhanced siliciclastic accumulation siliciclastic material escapes the outer shelf to queensland trough through interreef passages between 15 and 17 s latitude it is then focused to the south by ocean currents siliciclastic sediment is likely sourced from a combination of rivers transporting holocene sediment to the gbr shelf and late pleistocene sediment eroded from the outer shelf and reworked to queensland trough siliciclastic material crosses the shelf although the mechanisms e g river plumes nepheloid layers tidal currents cyclones mushroom jets remain poorly constrained however shelf width is clearly an important factor in allowing cross shelf transport to occur mass balance calculations indicate that up to 13 of the late holocene annual riverine sediment output may be delivered to queensland trough modern and ancient mixed system depositional models must be reevaluated to allow for the possibility of coeval siliciclastic and carbonate deposition

outgoing long wave radiation variability from ir satellite data prior to major earthquakes abstract our analysis of the continuous outgoing long wave earth radiation olr indicates anomalous variations prior to a number of medium to large earthquakes the most recent analysis of olr is from the m9 0 sumatra andaman islands mega trust event we compared the reference fields for december 2001 to 2004 and found olr anomalous values 80 w m 2 2 within the epicentral area on dec 21 2004 5 days before the event we used the noaa ir daily one degree and monthly two and half degree gridded data to differentiate between the global and seasonal variability and the transient local anomalies the cause of such anomalies is not fully understood one possible explanation is the existence of thermal outgoing radiation as a result of near ground air ionization and latent heat change due to change of air humidity and temperature this phenomenon is hypothesized to be part of a relationship between tectonic stresses electrochemical and thermodynamic processes in the atmosphere and increasing mid ir flux all part of a family of electromagnetic em phenomena related to earthquake activity the time scale of the observed variations is a few weeks before the onset of the seismic event in comparison with several years of data the observed time series preceding the earthquake had unusually high olr the olr anomaly corresponds to a large area of ground coverage and coincides with the main epicentral zone the significance of these observations is explored using data from most recent east asian earthquake swarm of december 2004 and three other earthquakes

multisatellite observations of an intensified equatorial ionization anomaly in relation to the northern sumatra earthquake of march 2005 here we report multisatellite observations of ionospheric disturbances in relation to the occurrence of the m8 7 northern sumatra earthquake of 28 march 2005 the demeter detection of electro magnetic emissions transmitted from earthquake regions and champ challenging minisatellite payload satellite data were investigated to find possible precursory and postevent phenomena it was found that eia equatorial ionization anomaly strength expressed in the apex height derived from the champ plasma density profile was intensified along the orbits whose longitudes were close to the epicenter within about a week before and after occurrence of the earthquake increases in electron and o density along the orbits close to the epicenter were also observed in the demeter measurements the normalized equatorial plasma density derived from the demeter measurements showed intensification about a week before and after the earthquake reaching maximum the day after the shock and afterward disappearing in addition similar behavior of the eia enhancements related to the m8 0 pisco earthquake of 15 august 2007 was observed surveys of space weather and geomagnetic activities excluded the possibility that these fluctuations were caused by changes in space weather or by a geomagnetic storm statistical analyses of the longitudinal variation revealed that the eia was enhanced in the west of the epicenter and reduced in the east of the epicenter and this fits the increased conductivity model based on these observations we proposed a revised view of seismo ionospheric coupling in the region of the geomagnetic equator to explain the eia features observed in this study

ionospheric density variations recorded before the 2010 mw 8 8 earthquake in chile 1 we present a study of plasma density variations observed by the demeter spacecraft in the vicinity of a very powerful earthquake in chile this earthquake of moment magnitude 8 8 occurred on 27 february 2010 with an epicenter located at 35 85 s 72 72 w data recorded 10 20 days before the main shock along orbits close to the future epicenter show increasing plasma densities in a second step a statistical analysis with demeter data has been performed using the first 3 months of the years 2007 2010 to monitor density variations in the vicinity of the epicenter at the same local time and seasonal conditions this study shows that a large increase of the plasma density is very uncommon at this location and at this time and that the increases observed during the days before the main shock could be considered as possible short term precursors of this powerful earthquake

mesoscale circulation features of the great barrier reef region inferred from noaa satellite imagery abstract the commissioning of a noaa satellite receiving station at townsville in north queensland in 1988 greatly expanded the a vhrr coverage of the northeast australian region to include the entire great barrier reef system and marginal seas selected imagery from this and a southern station installed previously at aspendale victoria provide a valuable new perspective on oceanographic phenomena occurring in this ecologically significant region this perspective could not be attained using conventional ship board and in situ oceanographic sampling techniques a rich spectrum of mesoscale oceanographic features is revealed in the analyzed imagery and various features such as western boundary current meanders frontal shear waves eddies and jets are described the temporal and spatial variability of these features appears strongly linked to that of the larger scale coral sea current circulation several of the features identified are unique to the region others resemble features observed in other western boundary current systems but are significantly modified by the complex regional topography and by the presence of the great barrier reef gbr evidence has been found for a number of processes which have significant implications for the origin and maintenance of gbr ecosystems including shelf edge exchange processes stratified slope water intrusions onto the shelf and boundary layer mixing around reefs such processes provide a mechanism for injection of cool nutrient rich waters into the reef matrix the imagery provides a clear picture of a well organized but spatially complex frontal system existing in the southern coral sea which is associated with enhanced commercial and recreational fishing activity in the region the avhrr imagery has thus proven to be a valuable tool for spatial mapping of oceanographic features throughout the gbr region for hypothesis formation in dynamical and modeling studies and for ship board reconnaissance operations

tidally incised valleys on tropical carbonate shelves an example from the northern great barrier reef australia the formation of incised valleys on continental shelves is generally attributed to fluvial erosion under low sea level conditions however there are exceptions a multibeam sonar survey at the northern end of australia s great barrier reef adjacent to the southern edge of the gulf of papua mapped a shelf valley system up to 220 m deep that extends for more than 90 km across the continental shelf this is the deepest shelf valley yet found in the great barrier reef and is well below the maximum depth of fluvial incision that could have occurred under a 120 m eustatic sea level low stand as what occurred on this margin during the last ice age these valleys appear to have formed by a combination of reef growth and tidal current scour probably in relation to a sea level at around 30 50 m below its present position tidally incised depressions in the valley floor exhibit closed bathymetric contours at both ends valley floor sediments are mainly calcareous muddy gravelly sand on the middle shelf giving way to well sorted gravely sand containing a large relict fraction on the outer shelf the valley extends between broad platform reefs and framework coral growth which accumulated through the late quaternary coincides with tidal current scour to produce steep sided locally vertical valley walls the deepest segments of the valley were probably the sites of lakes during the last ice age when torres strait formed an emergent land bridge between australia and papua new guinea numerical modeling predicts that the strongest tidal currents occur over the deepest outer shelf segment of the valley when sea level is about 40 50 m below its present position these results are consistent with a pleistocene age and relict origin of the valley based on these observations we propose a new conceptual model for the formation of tidally incised shelf valleys tidal erosion on meso to macro tidal rimmed carbonate shelves is enhanced during sea level rise and fall when a tidal hydraulic pressure gradient is established between the shelf lagoon and the adjacent ocean basin tidal flows attain a maximum and channel incision is greatest when a large hydraulic pressure gradient coincides with small channel cross sections our tidal incision model may explain the observation of other workers that sediment is exported from the great barrier reef shelf to the adjacent ocean basins during intermediate rather than last glacial maximum low stand sea level positions the model may apply to other rimmed shelves both modern and ancient

sedimentology and basin evolution of the siluro devonian helderberg group central appalachians abstract the late silurian early devonian helderberg group central appalachians is a sequence of mixed siliciclastic carbonate sediments that was deposited during relative tectonic quiescence on a ramp that was built out from low relief tectonic highlands bordering the eastern side of the appalachian basin the helderberg group is a third order vail cycle that lasted about 8 10 m y three transgressive regressive sequences are also recognized each sequence was deposited over 2 3 m y subsidence rates during deposition were about 1 2 cm 1 000 yr lithofacies patterns resulted from eustatic sea level changes differential basin subsidence and varying sedimentation rates skeletal grainstone rudstone formed fringing skeletal banks that developed during regression and prograded away from the eastern side of the basin at rates of 35 50 m 1 000 yr quartz sandstone tongues in the helderberg group probably were reworked from underlying silurian sandstone and were introduced to the basin by rivers that nearly coincided with ancestral silurian drainage systems siliciclastic influx was never great enough to shut carbonate production off completely thick middle devonian siliciclastic sediments buried the helderberg group and updip subaerial exposures accompanying the onset of the acadian orogeny

longitudinal variation of the e region electric fields caused by atmospheric tides 1 polarization electric fields created by the e and f region dynamos cause the uplift of f region plasma the subsequent redistribution of that plasma along the magnetic field lines creates the equatorial ionospheric anomaly eia observations of the post sunset eia made by the image and timed satellites are compared here with champ orsted and sac c observations of the noontime equatorial electrojet eej during magnetically quiet periods around equinox the eia and eej show a remarkably similar four peaked wave like longitudinal variation its structure is consistent with the longitudinal variation in the strength of diurnal tides that drive the e region dynamo this indicates a strong vertical coupling between the ionosphere and troposphere because the four peaked tidal structure is driven by tropospheric weather furthermore the dayside ionospheric conditions are found to perform the global scale longitudinal structure of the post sunset ionosphere at low latitudes

stratigraphic control of the geochemistry of holocene inner shelf facies great barrier reef received 15 august 1994 revision accepted 28 june 1995 abstract cleveland bay and halifax bay are adjacent embayments situated on the inner shelf region o 20 m of the central great barrier reef shelf off townsville northeast australia these bays contain holocene sediments up to 5 m in thickness deposited during the last stages of the post glacial sea level rise x ray diffraction and x ray fluorescence techniques were used to examine the mineralogy and geochemistry of the main holocene facies sampled in 40 vibrocores the sediments of southern halifax bay and cleveland bay consist mainly of quartz ca 50 alkali feldspars ca 20 clay minerals ca 20 consisting of mixed layer clays smectite kaolinite and illite and carbonate ca 10 including aragonite and calcite the holocene facies sequence comprises in order of increasing age modern bay shoreline and mangrove sediments the oxides of the major components sioz a o fe203 mgo cao k o na o p o in halifax bay show the predicted linear correlations with geochemically related minor elements pb rb sr y zr ga zn ni co mn cr ti sc v ba and can be used to discriminate holocene facies however in cleveland bay these elements are poorly correlated within each facies and provide very poor facies discrimination these findings probably result from the presence of sandy shoreline sediments up to 2 m in thickness in the holocene sequence of cleveland bay with the consequent development of a weak oxic zone and migration of elements between adjacent facies a similar oxic zone is poorly developed in halifax bay because the shoreline facies there is either thin or absent that the chemical signatures of holocene inner shelf facies are spatially variable and are strongly influenced by the stratigraphy has wide implications for geochemical studies of marine sediments

wet season fine sediment dynamics on the inner shelf of the great barrier reef fine sediment dynamics were recorded in february 2007 in coastal waters of the great barrier reef during a moderate flood of the tully river an estuarine circulation prevailed on the inner continental shelf with a surface seaward velocity peaking at 0 1 m s 1 and a near bottom landward flow peaking at 0 05 m s 1 much of the riverine mud originating from eroded soils was exported onto a 10 km wide coastal strip during the rising stage of the river flood in the first flush in coastal waters suspended sediment concentration peaked at 0 2 kg m 3 near the surface and 0 4 kg m 3 at 10 m depth during calm weather and 0 5 kg m 3 near the surface and 2 kg m 3 at 10 m depth during strong winds when bottom sediment was resuspended diurnal irradiance at 4 m depth was almost zero for 10 days the sedimentation rate averaged 254 33 g m 2 d 1 over the 28 day study period and concentrations of dissolved and particulate nutrients originating from the river were high the observed low irradiance would have prevented coral photosynthesis while the sedimentation rate would have been lethal to some juvenile corals the mud may ultimately be minnowed out over long periods however flushing of the mud occurs at time scales much longer than the flood event and the mud is likely to affect coral physiology for significant periods after the flood has subsided the data show the need to better control erosion on farmed land for the conservation of coral reefs on the inner shelf of the great barrier reef

seismoionospheric gps total electron content anomalies observed before the 12 may 2008 mw7 9 wenchuan earthquake 1 the global ionospheric map gim is used to observe variations in the total electron content tec of the global positioning system gps associated with 35 m 6 0 earthquakes that occurred in china during the 10 year period of 1 may 1998 to 30 april 2008 the statistical result indicates that the gps tec above the epicenter often pronouncedly decreases on day 3 5 before 17 m 6 3 earthquakes the gps tec of the gim and electron density profiles probed by six microsatellites of formosat3 cosmic f3 c are further employed to simultaneously observe seismoionospheric anomalies during an mw7 9 earthquake near wenchuan china on 12 may 2008 it is found that gps tec above the forthcoming epicenter anomalously decreases in the afternoon period of day 6 4 and in the late evening period of day 3 before the earthquake but enhances in the afternoon of day 3 before the earthquake the spatial distributions of the anomalous and extreme reductions and enhancements indicate that the earthquake preparation area is about 1650 km and 2850 km from the epicenter in the latitudinal and longitudinal directions respectively the f3 c results further show that the ionospheric f2 peak electron density nmf2 and height hmf2 significantly decreases approximately 40 and descends about 50 80 km respectively when the gps tec anomalously reduces

cyclone pumping sediment partitioning and the development of the great barrier reef shelf system a review abstract the modern great barrier reef gbr is part of the world s largest and best known mixed terrigenous carbonate continental margin the gbr shelf contains three shore parallel sedimentary belts an inner shelf zone of terrigenous sedimentation at depths of 0 22 m a middle shelf zone of sediment starvation at depths of 22 40 m and an outer shelf reef tract with its inner edge at ca 40 m depth these zones are controlled by the dynamics of northward fair weather along shelf drift driven by southeasterly trade winds and by the regular passage of tropical cyclones cyclones cause wind driven north directed middle shelf flows in excess of 130 cm s which erode the seabed concentrate the sparse mobile sediment into sand ribbons and advect suspended load onto the outer part of the nearshore terrigenous sediment prism and into inter reef depocentres within the outer shelf reef tract cyclones largely control the input of new sediment into the gbr system via river flooding seabed erosion or reef breakage they also help to control the partitioning and dispersion of the three main shore parallel belts of sediment and hence stratigraphic accumulation acting as a sediment pump especially during interglacial highstands cyclones have exerted great control on the development of the modern gbr province and its sediments by maintaining a broad shelf parallel zone of episodically mobilised sediment and scoured seabed upon which coral reefs have been unable to form cyclones may also have partly controlled the timing of initiation of the first gbr at 0 6 mybp contrary to current models gbr storm beds are most likely to be preserved intact close to the shoreline and become coarser grained away from the shoreline for the central gbr highstand shedding only applies to carbonate sediment at the scale of local reefs system wide oceanographic controls cause high rates of carbonate sedimentation on the slope during both sea level rise and highstand concomitantly terrigenous sediment accumulates fastest on the slope during sea level rise and slowest during sea level lowstand and highstand

post glacial seismic stratigraphy central great barrier reef australia a regional programme of continuous seismic boomer profiling in the central great barrier reef province has identified a widespread shallow seismic discontinuity reflector a which is interpreted as the pre holocene surface nine seismic facies units are distinguished primarily on the basis of the seismic records but also with the aid of additional criteria such as location and surface sediment types two units underlie reflector a and are pre holocene these units are interpreted as a permo carboniferous bedrock and b pleistocene tertiary sediments consisting of both shelf wide terrigenous units and carbonate mounds and platforms under present reefs seven units are post glacial and overlie reflector a these units are interpreted as c fluvial estuarine channel fill d relict delta front deposits e relict transgressive veneer f coastal coarse and g fine deposits h modern reef and i reef talus in general post glacial sediment cover is very thin and in many places on the mid shelf the pre holocene units crop out substantial post glacial accumulations are limited to protected coastal embayments and to offshore reef masses

ionospheric density and velocity anomalies before m 6 5 earthquakes observed by demeter satellite abstract the seismo ionospheric density anomalies have been widely studied for last decades based on ground gps and satellite in situ observations in this paper we analyze both ion density and ion velocity observed by the french satellite demeter before 49 earthquakes with m 6 5 in 2010 the results show that both ion density and ion velocity increase anomalously before the earthquakes the differences before and after earthquakes are more significant with larger magnitude and shallower depth the density variations have a positive correlation with the perpendicular velocity which is related to the perpendicular electric field by e v b0 b0 is the background geomagnetic field the slopes of ni ni in units of vs v in units of m s ranges from 0 13 to 0 7 this suggests that the ion density variation is associated with the presence of ion velocity or electric field in the ionosphere the observed peak perpendicular velocity can reach 300 1300 m s before the earthquakes corresponding to a perpendicular electric field e 7 5 32 5 mv m

late holocene sediment in nara inlet central great barrier reef platform australia sediment accumulation on the middle shelf of a tropical mixed clastic carbonate system nara inlet in the whitsunday islands is a natural depocenter for clastic and carbonate sediment on the middle shelf of the central great barrier reef gbr platform three sediment cores were collected from the inlet to understand sediment accumulation in this tropical mixed clastic carbonate system over time surface and subsurface sediment is comprised of two main components terrigenous clay and shallow marine carbonate similar to other regions on the middle shelf of the gbr platform the carbonate component 25 80 by weight and dominated by sr poor foraminifera tests and mollusc shells generally increases towards the surface radiocarbon ages derived from tests of benthic foraminifera indicate that the top 3 m of sediment accumulated within the last 3000 years but that the rate has slowed toward present day the change in clastic and carbonate abundance therefore indicates a system where both clastic and carbonate accumulation has decreased over time but where clastic accumulation has decreased faster reduced clastic accumulation may reflect progressive impedance of terrigenous input by a laterally growing fringing reef at the mouth of nara inlet likewise reduced carbonate accumulation may reflect preferential reef growth and carbonate deposition outside of the inlet even though clastic accumulation has decreased significantly over time the late holocene mass composition and distribution of clastic material in nara inlet implies a terrigenous source previously unrecognized in models for the evolution of the gbr platform large amounts of terrigenous sediment probably were stored around topographic highs on the middle shelf during lowstand and early transgression this clastic material was then removed over time mixed with autochthonous carbonate and deposited in embayments on the middle shelf the accumulation of sediment on the middle shelf of a tropical mixed clastic carbonate margin is not straightforward

the modern mixed carbonate siliciclastic abrolhos shelf implications for a mixed depositional model abstract high resolution seismic facies analysis and stratigraphy of a mixed carbonate siliciclastic shelf yields insights into sedimentation controlled by interactions among carbonate production siliciclastic sediment supply and changes in relative sea level high resolution seismic core and surface samples collected along the northern area of the abrolhos shelf brazil including the inner middle and outer shelf constrain the genesis of the shelf two sets of seismic sequences were identified a pleistocene sequence and pleistocene holocene sequence a subaerial unconformity from subaerial exposure during the last glacial maximum separates the two sequences the upper seismic sequence the focus of this study comprises retrograding aggrading transgressive and aggrading prograding regressive seismic geometries carbonate sedimentation predominated within the last postglacial transgressive phase the subsequent regressive phase was dominated by nearshore siliciclastic sedimentation at shallow depths up to 12 m below 12 m depth a transition occurs to mixed siliciclastic carbonate facies and ultimately carbonate sedimentation farther offshore seismic data indicate that holocene nearshore coral reef growth was influenced by the positive antecedent relief of a pleistocene reef platform and terrigenous sedimentation although siliciclastic carbonate mixed sedimentation has been reported in other successions during periods of regression siliciclastic sedimentation in northern abrolhos shelf is limited to nearshore settings rather than bypassing the shelf

late quaternary siliciclastic carbonate sedimentation model for the capricorn channel southern great barrier reef province australia abstract a model is presented for hemipelagic siliciclastic and carbonate sedimentation during the last glacial interglacial cycle in the capricorn channel southern great barrier reef gbr stable isotope ratios grainsize carbonate content and mineralogy were analysed for seven cores in a depth transect from 166 to 2892 m below sea level mbsl results show variations in the flux of terrigenous neritic and pelagic sediments to the continental slope over the last sea level cycle during the glacial lowstand terrigenous sediment influenced all the cores down to 2000 mbsl the percentages of quartz and feldspar in the cores decreased with water depth while the percentage of clay increased x ray diffraction analysis of the glacial lowstand clay mineralogy suggests that the siliciclastic sediment was primarily sourced from the fitzroy river which debouched directly into the northwest sector of the capricorn channel at this time the cores also show a decrease in pelagic calcite and an increase in aragonite and high magnesium calcite hmc during the glacial the influx of hmc and aragonite is most likely from reworking of coral reefs exposed on the continental shelf during the glacial and also from hmc ooids precipitated at the head of the capricorn channel at this time mass accumulation rates mars are high 13 5 g cm 3 kyr 1 during the glacial and peak at 20 g cm 3 kyr 1 in the early transgression 16 14 ka bp mars then decline with further sea level rise as the fitzroy river mouth retreats from the edge of the continental shelf after 13 5 ka bp mars remain low 4 cm 3 kyr 1 throughout the holocene highstand data for the holocene highstand indicate there is a reduction in siliciclastic influx to the capricorn channel with little quartz and feldspar below 350 mbsl however fine grained fluvial sediments presumably from the fitzroy river were still accumulating on the mid slope down to 2000 mbsl the proportion of pelagic calcite in the core tops increases with water depth while hmc decreases and is present only in trace amounts in cores below 1500 mbsl the difference in the percentage of hmc in the deeper cores between the glacial and holocene may reflect differences in supply or deepening of the hmc lysocline during the glacial sediment accumulation rates also vary between cores in the capricorn channel and do not show the expected exponential decrease with depth this may be due to intermediate or deep water currents reworking the sediments it is also possible that present bathymetry data are too sparse to detect the potential role that submarine channels may play in the distribution and accumulation of sediments comparison of the capricorn channel mars with those for other mixed carbonate siliciclastic provinces from the northeast margin of australia indicates that peak mars in the early transgression in the capricorn channel precede those from the central gbr and south of fraser island the difference in the timing of the carbonate and siliciclastic mar peaks along the northeast margin is primarily related to differences in the physiography and climate of the provinces the only common trend in the mars from the northeast margin of australia is the near synchronicity of the carbonate and siliciclastic mar peaks in individual sediment cores which supports a coeval sedimentation model

a novel method to measure calcium carbonate with portable x ray fluorescence instrumentation and its application to gulf of mexico surficial sediments abstract a novel rapid low cost non destructive and reliable technique was developed to simultaneously measure calcium carbonate caco3 and trace element concentrations in sediments with a portable x ray fluorescence pxrf analyzer and applied to 27 samples of surficial sediments collected from the yucatan continental shelf 1200 m water depth of the gulf of mexico this technique is based on calculation of authigenic calcium caauth from the total ca measured with the pxrf results obtained with the pxrf showed a very high and highly significant correlation r 0 99 p

observations and simulations of seismoionospheric gps total electron content anomalies before the 12 january 2010 m7 haiti earthquake 1 in this paper the total electron content tec of the global ionosphere map gim is used to detect seismoionospheric anomalies associated with the 12 january 2010 m7 haiti earthquake and an ionospheric model is applied to simulate the detected anomalies the gim temporal variation shows that the tec over the epicenter significantly enhances on 11 january 2010 1 day before the earthquake the latitude time tec ltt plots reveal three anomalies 1 the northern crest of equatorial ionization anomaly eia moves poleward 2 the tecs at the epicenter and its conjugate increase and 3 the tecs at two dense bands in the midlatitude ionosphere of 35 n and 60 s further enhance the spatial analysis demonstrates that the tec enhancement anomaly appears specifically and persistently in a small region of the northern epicenter area the simulation well reproduces the three gim tec anomalies which indicate that the dynamoelectric field of the ionospheric plasma fountain might have been perturbed by seismoelectric signals generated around the epicenter during the earthquake preparation period

postglacial sediment deposition along a mixed carbonate siliciclastic margin new constraints from the drowned shelf edge reefs of the great barrier reef australia a seismic stratigraphy analysis was conducted at two sites hydrographers and noggin passages separated by about 540 km on the shelf edge of the central great barrier reef gbr australia we used recently available seismic and bathymetry data and a new synthesis of downhole logs and lithological petrophysical and radiometric data from cores recovered by the integrated ocean drilling program expedition 325 great barrier reef environmental changes we compared the stratigraphy of both sites identifying a full depositional sequence with deposits from at least 28 ka bp to 7 ka bp bounded by two marine flooding surfaces within this sequence each systems tract is represented by unique depositional features characteristic of the shelf edge systems despite the broad environmental and geomorphic similarities between the two sites differences in postglacial reef development were remarkable these contrasts can be explained as a result of 1 local antecedent substrate variations and 2 the interplay of shelf physiography with late quaternary sea level fluctuations which favoured changes in biological production and sediment flux as the palaeo shoreline evolved from linear to complex during intermediate sea levels during these intermediate sea levels the northern estuarine coast and its steep substrate at shelf edge locations contrasted strongly with the protected palaeo lagoons and the extensive gentle marginal terraces found at the southern central gbr this setting enhanced the regional differences in sediment transport and reef development through the last transgression the conceptual model presented here provides a broader depositional framework and improves the understanding of the main processes controlling the spatial and temporal depositional patterns on the shelf edge of mixed siliciclastic carbonate margins

supply limited sediment transport in a high discharge event of the tropical burdekin river north queensland australia interactions between catchment variables and sediment transport processes in rivers are complex and sediment transport behaviour during high flow events is not well documented this paper presents an investigation into sediment transport processes in a short duration high discharge event in the burdekin river a large sand and gravel bed river in the monsoon and cyclone influenced semi arid tropics of north queensland the burdekin s discharge is highly variable and strongly seasonal with a recorded maximum of 40 400 m s sediment was sampled systematically across an 800 m wide 12 m deep and straight reach using helley smith bedload and us p 61 suspended sediment samplers over 16 days of a 29 day discharge event in february and march 2000 peak 11 155 m s about 3 7 10 tonnes of suspended sediment and 3 10 tonnes of bedload are estimated to have been transported past the sample site during the flow event the sediment load was predominantly supply limited wash load included clay silt and very fine sand the concentration of suspended bed material including very coarse sand varied with bedload transport rate discharge and height above the bed bedload transport rate and changes in channel shape were greatest several days after peak discharge comparison between these data and sparse published data from other events on this river shows that the control on sediment load varies between supply limited and hydraulically limited transport and that antecedent weather is an important control on suspended sediment concentration neither the empirical relationships widely used to estimate suspended sediment concentrations and bedload e g ackers white 1973 nor observations of sediment transport characteristics in ephemeral streams e g reid frostick 1987 are directly applicable to this river

development of a late visean mississippian mixed carbonate siliciclastic platform in the guadalmellato valley southwestern spain abstract the penas rubias syncline southwestern spain exposes a well preserved shallow water platform succession containing a spectrum of facies corresponding to inner platform intertidal to supratidal environments across to deeper water middle to outer platform environments nineteen microfacies are recognized which are grouped into seven facies association corresponding to siliciclastic deltaic bars mixed carbonate siliciclastic shoals carbonate mud mound boundstones background platform carbonates background platform siliciclastics mixed tempestites and deep water siliciclastic shales and sandstones the age of the succession was determined mainly by foraminiferans and calcareous algae which permit the succession to be assigned to the late brigantian latest visean this upper brigantian platform is the only record of sedimentation of this age in the region and thus is key for interpreting the sedimentary and tectonic evolution of the carboniferous rocks in sierra morena biotic and sedimentological features were analyzed in order to assess the controls on the sedimentation several factors have influenced sedimentological changes turbidity subsidence siliciclastic discharges storms and bioturbation the siliciclastic discharges exerted a considerable control on the basal deposits mostly in their percentage of quartz sand grains and as microconglomerates however they did not develop as large deltaic deposits and their influence can be considered as virtually negligible in regards to the remaining part of the succession turbidity as a result of higher percentage of silt and mud in suspension seems to be the main factor controlling the change between the older intertidal deposits in the inner platform to the younger subtidal deposits of the middle and outer platform as a result of the increase of the mud and silt in suspension facies changed first to marlstones and nodular argillaceous limestones and second to predominantly calcimicrobial boundstones and shales in the uppermost part of the carbonate succession as well as showing a marked change from photic controlled benthic faunal and microfloral assemblages to assemblages more tolerant or better adapted to muddier dysphotic substrates bioturbation is also interpreted as one of the main controls influencing the different type of boundstones in the middle platform permitting the vertical growth of dome shaped mud mounds or as sheet like deposits storm influences seem to have exerted some control on the positive relief of the dome shaped boundstones which are usually capped by tempestites the differential subsidence observed in the northwestern sector of the platform allowed the accumulation of many stacked dome shaped mounds a feature not recognized in southeastern parts the general stratigraphical sequence seems to be controlled by eustasy and synsedimentary tectonics the overall succession exhibits a pronounced deepening upwards transgressive sequence from siliciclastic delta bars mixed shoals carbonates and shales of the middle platform with the growth of calcimicrobial boundstones and dark green shales passing up into black shales at the top of the sequence in the outer platform and possibly submarine slope settings although this transgressive sequence is in harmony with the 3rd order glacioeustatic cycle defined for the late brigantian in the western palaeotethys all these brigantian rocks accumulated in a synsedimentary extensional regime which is related to the initiation of a sinistral strike slip regime previously recognized as affecting only serpukhovian and younger rocks in sierra morena these synsedimentary faults allow us to recognize significant lateral variations in thickness over short distances

the cyclone winifred storm bed central great barrier reef shelf australia abstract shelf sediments were collected immediately before 8 20 january 1986 immediatly after 9 10 february 1986 and one year after 27 february 1987 cyclone winifred crossed the central great barrier reef shelf on 1 february 1986 the storm produced a normally graded mixed terrigenous carbonate storm bed more than 11 cm thick covering an area at least 1 200 km2 and extending more than 30 km offshore to water depths greater than 40 m the storm layer encompasses two lithologically distinct shelf parallel facies belts the nearshore 0 25 m depth storm bed is 311 cm thick thins offshore and grades upward from medium sand to silty clay offshore 25 43 m depth the storm bed thickens to more than 11 cm and consists of normally graded well sorted relict quartz and skeletal gravelly sands capped by a thin mud veneer the cross shelf distributions of grain size mineralogy carbonate content and carbon isotope ratios were very similar before and after winifred suggesting the storm bed did not result from offshore directed storm currents but rather in situ resuspension and settling of the shelf sand with shoreward transport of mud in contrast to storm sedimentation models which predict thinning and fining offshore winifred created a layer that becomes thicker and coarser grained in deeper water in response to cross shelf substrate changes after one year the winifred storm layer was well preserved nearshore 30 m water depth below fairweather wave base preservation may not be a matter of insulating the layer from physical reworking below fairweather wave base but of burying it where rates of sediment accumulation outpace bioturbation the effects of storms similar in size to winifred may be well concealed in ancient shelf sequences subject to rapid biological remixing of storm layers

continuous 150 k y monsoon record from lake eyre australia insolation forcing implications and unexpected holocene failure our reconstructed history of lake eyre provides the first continuous continental proxy record of australian monsoon intensity over the past 150 k y this continental record s broad correspondence to the marine isotope record demonstrates that this very large catchment with its hydrology dependent on a planetary scale climate element responds to milankovitch scale climate forcing abrupt transitions from dry phases to wet phases ca 125 and 12 ka coincide with northern hemisphere winter insolation minima rather than southern hemisphere summer insolation maxima indicating that northern hemi sphere insolation exerts a dominant control over the intensity of the australian monsoon stratigraphic and dating uncertainties of other wet phases preclude conclusive correlation to specific insolation signals but within the uncertainties are consistent with northern hemisphere forcing regardless of the hemispheric forcing the low intensity of the early holocene australian monsoon by comparison with the last interglacial and particularly the last high level lacustrine event at 65 60 ka when all forcing elements were modest is an enigma that can be explained by a change in boundary conditions within australia

late quaternary sedimentation on the great barrier reef continental shelf and slope east of townsville australia cores collected in a shelf to basin transect from northeastern australia document the stratigraphic development of late quaternary deposits low sea level to 120 m slope sedimentation is dominated by prograding fluvial deposits with wave dominated deltas forming on the shelf edge and upper slope the onset of sea level transgression into the excavated shelf river channels on the outer shelf resulted in estuarine sedimentation along an indented coastline 15 000 11 000 yrs b p reducing terrigenous sediment supplies to the slope on the outer shelf halimeda muddy sandy gravels were deposited over a pleistocene limestone erosional surface from about 10 500 yrs b p transgression submerged the limestone outcrops and estuaries of the middle shelf where coral reef complexes formed the outer and middle parts of the shelf thus became dominated by carbonate sedimentation while the inner shelf received fluvial input mixed with locally derived carbonates the sequence is bounded by an unconformity clearly marked by erosional down cutting the results of the study are combined with those of previous workers to develop transgressive and continued high sea level system tract models the latter continued high sea level model is used to extrapolate present high sea level sedimentation patterns into the future providing a model for comparison with ancient sequences which may also have formed in such a depositional environment

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

new evidence for episodic post glacial sea level rise central great barrier reef australia abstract we present an extensive database of 364 radiocarbon dates from coastal and marine sediments of the central great barrier reef gbr shelf of which 110 are previously unpublished the elevation data have been reduced to a common datum australian height datum ahd and the various sources of error have been assessed using modern lithological and biological relationships with sea level the elements of the radiocarbon database have been converted into sea level indicators the upper bound of the assembled dataset corresponds to a best estimate sea level curve and the full dataset provides a narrow envelope for sea level rise on the gbr shelf for the last 11 12 kyr not including hydro isostatic crustal flexing the envelope is consistent with episodic rise in post glacial sea levels the rising post glacial sea level probably included stillstands or minor falls at ca 45 m ahd at ca 10 5 kyr b p 5 m 7 8 kyr b p 2 m ca 6 kyr b p and 1 7 m 5 5 kyr b p there is evidence for a significant fall in sea level between stillstands at 11 m 8 5 kyr b p and 17 m 8 2 kyr b p stillstand durations apparently ranged between the vertical spread in the derived sea level data is very wide the use of shell material for dating seems unreliable and prone to large and unpredictable errors data from bulk mangrove muds appear reliable for determination of ancient sea level but may at times result in sea level being placed up to 4 m below the true level in situ biogenic carbonates such as preserved oyster beds and coral micro atolls are the most reliable indicators of sea level position while deposits of mangrove mud give a useful first order approximation of ancient sea levels caution should be used in drawing sea level curves from few data points we conclude that the post 11 12 kyr b p relative rise in sea level was episodic on the central gbr continental margin more data are required to define clearly sea level change up to ca 20 m at 9 kyr b p

late pleistocene history of turbidite sedimentation in a submarine canyon off the northern great barrier reef australia cores from slopes east of the great barrier reef gbr challenge traditional models for sedimentation on tropical mixed siliciclastic carbonate margins however satisfactory explanations of sediment accumulation on this archetypal margin that include both hemipelagic and turbidite sedimentation remain elusive as submarine canyons and their role in delivering coarse grained turbidite deposits are poorly understood towards addressing this problem we investigated the shelf and canyon system bordering the northern ribbon reefs and reconstructed the history of turbidite deposition since the late pleistocene high resolution bathymetric and seismic data show a large paleo channel system that crosses the shelf before connecting with the canyons via the inter reef passages between the ribbon reefs high resolution bathymetry of the canyon axis reveals a complex and active system of channels sand waves and local submarine landslides multi proxy examination of three cores from down the axis of the canyon system reveals 18 turbidites and debrites interlayered with hemipelagic muds that are derived from a mix of shallow and deep sources twenty radiocarbon ages indicate that siliciclastic dominated and mixed turbidites only occur prior to 31 ka during marine isotope stage mis 3 while carbonate dominated turbidites are well established by 11 ka in mis1 until as recently as 1 2 ka the apparent lack of siliciclastic dominated turbidites and presence of only a few carbonate dominated turbidites during the mis2 lowstand are not consistent with generic models of margin sedimentation but might also reflect a gap in the turbidite record these data suggest that turbidite sedimentation in the ribbon reef canyons probably reflects the complex relationship between the prolonged period 25 ka of mis3 millennial sea level changes and local factors such as the shelf inter reef passage depth canyon morphology and different sediment sources on this basis we predict that the spatial and temporal patterns of turbidite sedimentation could vary considerably along the length of the gbr margin

filling the gap a 60 ky record of mixed carbonate siliciclastic turbidite deposition from the great barrier reef abstract late pleistocene to holocene margin sedimentation on the great barrier reef a mixed carbonate siliciclastic margin has been explained by a transgressive shedding model this model has challenged widely accepted sequence stratigraphic models in terms of the timing and type of sediment i e carbonate vs siliciclastic deposited during sea level oscillations however this model documents only hemipelagic sedimentation and the contribution of coarse grained turbidite deposition and the role of submarine canyons in this process remain elusive on this archetypal margin here we present a new model of turbidite deposition for the last 60 ky in the north eastern australia margin using high resolution bathymetry 58 new and existing radiometric ages and the composition of 81 turbidites from 15 piston cores we found that the spatial and temporal variation of turbidites is controlled by the relationship between sea level change and the variable physiography along the margin siliciclastic and mixed carbonate siliciclastic turbidites were linked to canyons indenting the shelf break and the well developed shelf edge reef barriers that stored sediment behind them turbidite deposition was sustained while the sea level position allowed the connection and sediment bypassing through the inter reef passages and canyons carbonate turbidites dominated in regions with more open conditions at the outer shelf and where slope confined canyons dominated or where canyons are generally less abundant the turn on and maintenance of carbonate production during sea level fluctuations also influenced the timing of carbonate turbidite deposition we show that a fundamental understanding of the variable physiography inherent to mixed carbonate siliciclastic margins is essential to accurately interpret deep water coarse grained deposition within a sequence stratigraphic context

equatorial plasma fountain and its effects over three locations evidence for an additional layer the f 3 layer the equatorial plasma fountain and equatorial anomaly in the ionospheres over jicamarca 77 w trivandrum 77 e and fortaleza 38 w are presented using the sheffield university plasmasphere ionosphere model under magnetically quiet equinoctial conditions at high solar activity the daytime plasma fountain and its effects in the regions outside the fountain lead to the formation of an additional layer the f3 layer at latitudes within about plus or minus 10 of the magnetic equator in each ionosphere the maximum plasma concentration of the f3 layer which occurs at about 550 km altitude becomes greater than that of the f2 layer for a short period of time before noon when the vertical e b drift is large within the f3 layer the plasma temperature decreases by as much as 100 k the ionograms recorded at fortaleza on january 15 1995 provide observational evidence for the development and decay of an f3 layer before noon the neutral wind which causes large north south asymmetries in the plasma fountain in each ionosphere during both daytime and nighttime becomes least effective during the prereversal strengthening of the upward drift during this time the plasma fountain is symmetrical with respect to the magnetic equator and rises to over 1200 km altitude at the equator with accompanying plasma density depletions in the bottomside of the underlying f region the north south asymmetries of the equatorial plasma fountain and equatorial anomaly are more strongly dependent upon the displacement of the geomagnetic and geographic equators jicamarca and trivandrum than on the magnetic declination angle fortaleza

atmospheric anomalies observed during earthquake occurrences 1 appearance of anomalies in the atmosphere before earthquakes eqs has been verified through observation of anomalous transmission of vhf electromagnetic em waves beyond line of sight anomalous increase of the received intensity for a few minutes several hours on a day was identified by the previous 15 day running median and its inter quartile range the cross correlation between the eq occurrences and the anomalies shows that the appearance of anomalies was significantly enhanced within 5 days before m 4 8 eqs the one day average number of the anomaly appearance within 5 days was found 2 4 times larger than that of other days through the polarization measurement of the received em waves the anomalies were found to occur in the atmosphere index terms 6904 radio science atmospheric propagation 6964 radio science radio wave propagation 7223 seismology seismic hazard assessment and prediction citation fujiwara h m kamogawa m ikeda j y liu h sakata y i chen h ofuruton s muramatsu y j chuo and y h ohtsuki 2004 atmospheric anomalies observed during earthquake occurrences geophys res lett 31 l17110

ionosphere plasma bubbles and density variations induced by pre earthquake rock currents and associated surface charges 1 recent ionospheric observations indicate that the total electron content tec may anomalously decrease or increase up to 5 20 before the occurrence of big earthquakes the ionospheric density variations can be caused by earth surface charges currents produced from electric currents associated with the stressed rock we formulate a coupling model for the stressed rock earth surface charges atmosphere ionosphere system the stressed rock acts as the dynamo to provide the currents for the coupling system the electric fields and currents in the atmosphere and the lower boundary of ionosphere are obtained by solving the current continuity equation j 0 where j is the current density a three dimensional ionosphere simulation code is then used to study the ionospheric dynamics based on the obtained electric fields and currents the simulation results show that a current density jrock 0 2 10 a m2 in an earthquake fault zone is required to cause daytime tec variations of 2 25 the simulation results also show that a current density jrock 0 01 1 a m2 can lead to nighttime tec variations of 1 30 as well as the formation of a nighttime plasma bubble equatorial spread f extending over the whole magnetic flux tube containing the earthquake epicenter we suggest that observations of daytime and nighttime tec variations and a nighttime plasma bubble within the affected region can be used as precursors for earthquake prediction

cyclic sedimentation in the mixed siliciclastic carbonate abo hueco transitional zone lower permian southwestern new mexico abstract in southwestern new mexico lower permian wolfcampian rocks grade southward from nonmarine siliciclastics abo and earp formations to marine carbonates hueco and horquilla formations a transitional zone between siliciclastic and carbonate facies trends east northeast across southwestern new mexico and consists of 64 to 186 m of cyclically interbedded siliciclastic and carbonate rocks which were deposited in tidal flat and shallow marine environments shallow marine facies include fossiliferous limestone and olive gray shale tidal flat facies consist of 1 ripple laminated sandstone which was deposited on intertidal sandflats near mean low tide 2 mixed sandstone shale which was deposited on an intertidal flat shoreward of the ripple laminated sandstone facies and 3 nodula shale which is characterized by pedogenic calcareous nodules and was deposited in a supratidal setting the intertidal facies are truncated by or grade laterally into rare channel sandstones which represent tidal creek or estuarine facies in addition to siliciclastic tidal flat deposits a few beds of laminated carbonate also were deposited in the intertidal zone vertical sequence analysis aids in delineating three types of depositional cycles asymmetrical cycles display the vertical sequence basal fossiliferous limestone olive gray shale ripple laminated sandstone mixed sandstone shale nodular shale and record shoreline progradation the asymmetrical cycle is always overlain by fossiliferous limestone which indicates a major transgression that inhibited siliciclastic sedimentation a common symmetrical cycle consists of fossiliferous limestone olive gray shale ripple laminated sandstone olive gray shale fossiliferous limestone and indicates systematic seaward and landward migration of facies zones associated with small scale sea level changes a less common symmetrical cycle involves laminated carbonate fossiliferous limestone aminated carbonate cyclic sedimentation in abo hueco transitional strata is most likely the result of glacial eustatic sea level fluctuations

late pleistocene evolution of the mixed siliciclastic and carbonate southwestern new caledonia continental shelf lagoon abstract the main island of new caledonia nc is surrounded by the second largest barrier reef in the world after the australian great barrier reef the upper pleistocene evolution of this barrier reef lagoon complex offers the opportunity to examine the response of a modern mixed tropical siliciclastic carbonate system to relative sea level changes and to better constrain the relative role of lagoon backfilling and paleo drainage system in sediment transfer across the shelf this paper mainly focuses on the results of chronostratigraphic and sedimentological interpretations of new seismic bathymetric and coring data collected in the sw nc lagoon several significant points are highlighted from this study and allow the construction of a refined model which includes the evolution of both the sw nc mixed shelf and lagoon new results show that the nc lagoon has not recorded a reciprocal sedimentation during glacial interglacial sea level cycles but a unique mixed regime strong contrasts are observed and these depend above all on the two lagoon domains the outer coral plateau and the inner lagoon depression corresponding to a semi closed proximal basin which is separated from the plateau by a basement ridge in the depression clastic sediments remain dominant from early flooding to highstand stages while carbonate sedimentation continued through time across the coral plateau this spatial contrast between terrigenous and carbonate deposits was maintained throughout various sea level cycles thus even if spatial segregation is also observed for other examples of mixed shelf environments the sw nc shelf appears quite unique in comparison to the other mixed systems when considering conceptual models of reciprocal sedimentation moreover the presence of a semi enclosed lagoon depression allows the preservation of larger volume of terrigenous deposits this semi filled geometry of the lagoon is assumed to be the result of several factors a significant subsidence that offers accommodation for aggrading deposits evacuation through channels of sediments mobilized during storm events the tidal currents and fairweather wave dynamics lastly the inherited morphologic and structures may explain the geomorphic evolution of the escarpment margin type of the sw nc rimmed shelf and its differentiation with the opposite se nc ramp type shelf

complex sediment deposition history on a wide continental shelf implications for the calculation of accumulation rates on the great barrier reef article history understanding the key processes controlling the delivery deposition and fate of sediments on continental shelves is critical to appreciate the evolution of coasts and estuaries and to interpret geological sequences this study presents radiocarbon and optically stimulated luminescence osl ages of sediment cores collected from key locations offshore from the burdekin river australia the largest single source of sediment delivered to the great barrier reef gbr lagoon the ages show variable sediment accumulation rates at the different locations that coincide with the holocene avulsion history of the burdekin river our data show that most fine sediment 63 m delivered from the burdekin river is retained within 50 km of the mouth a finding that contrasts previous studies which postulated that fine sediments are advected northwards via longshore drift processes the pairing of radiocarbon and osl ages provides insights on resuspension regimes operating on the inner shelf of the gbr it was thought that turbidity on inshore gbr coral reefs and seagrass meadows has increased as a result of increased erosion in the adjacent catchment from agricultural development our data show that the age of the sediments in cleveland bay derived from the radiocarbon ages from shell and organic material can be several thousand years older than when the sediment was last deposited osl ages however the increased turbidity could conceivably be caused from new biologically produced sediment i e particulate organic matter as a result of increased nutrient export to the gbr we suggest that the composition of sediment in resuspension events before and after the wet season be analysed to examine whether newly delivered organic rich sediment can affect coral reefs and seagrass meadows

variability of surface ocean radiocarbon and stable isotopes in the southwestern pacific we present high precision radiocarbon 14c results and stable isotope 18o and 13c records for a coral from heron island 23 s 152 e and new stable isotope 18o and 13c records for annual coral bands from abraham reef 22 s 153 e in the southern great barrier reef studied earlier druffel and griffin 1993 these tracers provide unique information on the regional water mass history and together these data allow us to constrain the variability of circulation in the upper pacific over the past four centuries first we observe decreases in 18o of coral from abraham reef and heron island indicating an increase in sea surface temperature and or a decrease in surface salinity since 1850 second the small suess effect value 14c decrease from 1880 to 1955 due mostly to fossil fuel co2 observed previously at abraham reef druffel and griffin 1993 is confirmed in the measurements reported here from the heron island coral this value is low compared to those observed in other areas of the ocean druffel 1997 druffel and linick 1978 nozaki et al 1978 between 1880 and 1955 third we report alterations in the correlation between el nino events and the occurrence of low 14c which is indicative of long term change s in circulation in the sw pacific the 14c shifts reported here are not large but even small temporal changes in prebomb 14c suggest that important changes in the large scale state of the ocean have occurred such as a temporal change in circulation

new constraints on the origin of the australian great barrier reef results from an international project of deep coring two new boreholes provide the first direct evidence of the age of the australian great barrier reef an inner shelf sequence total depth 86 m basal age 210 40 ka comprises a dominantly siliciclastic unit thickness 52 86 m overlain by four carbonate units total thickness 0 34 m a shelf edge and slope sequence total depth 210 m reveals three major sections 1 a lower section of resedimented flows deposited on a lower slope 2 a mid section including intervals of corals rhodoliths and calcarenites with low angle graded laminae and 3 an upper section of four shelf margin coral reef units separated by karst surfaces bearing paleosols sr isotope and magnetostratigraphic data indicate that the central great barrier reef is relatively young post bruhnes matuyama boundary time and our best estimate for the onset of reef growth on the outer barrier system is ca 600 280 ka this date suggests that reef initiation may have been related to the onset of full eccentricity dominated glacio eustatic sea level oscillation as inferred from large amplitude saw tooth 100 k y 18o cycles after marine isotope stage 17 rather than to some regional environmental parameter a major question raised by our study is whether reef margins globally display a similar growth history the possibility of a global reef initiation event has important implications for basin to shelf partitioning of caco3 atmospheric carbon dioxide levels and global temperature change during quaternary time

mixed siliciclastic carbonate systems and their impact for the development of deep water turbidites in continental margins a case study from the late jurassic to early cretaceous shelburne subbasin in offshore nova scotia progradation of deltaic systems that reach the shelf edge is considered a primary mechanism to deliver sand to continental margins sediment bypass processes can dominate the outer shelf to upper slope transition causing poor preservation of reservoir quality sandstones turbidites can carry the bulk of the coarse fraction downdip where a thicker sand pile can be deposited once the channel to lobe transition is reached predicting this lateral and vertical variability along the slope is challenging this configuration can be further complicated when mixed siliciclastic carbonate systems are present the roseway missisauga case study from nova scotia is used here to explore potential implications associated with the development of deep water turbidites that are time equivalent to outer shelf mixed siliciclastic carbonate units two scenarios are possible 1 the carbonate factory is dominant and the development of carbonate reefs and pinnacles on the outer shelf prevents the passage of siliciclastic systems beyond the shelf break in this case the siliciclastic component is sequestered within the inner outer shelf 2 favorable conditions for carbonate production gradually deteriorate by the activation of fluviodeltaic systems that prograde outboard reaching the slope region in this last scenario low relief and lateral discontinuous carbonate shoals are ubiquitous in the outer shelf representing the last outboard remnants of the carbonate factory shelf edge deltas circumvent or breach these carbonate shoals establishing sedimentary pathways on the shelf break region that connect with deep water turbidites observations suggest that this last scenario is the most likely in this part of the scotian margin during the late jurassic to early cretaceous

mechanism and risk assessment of overall instability induced rockbursts in deep island longwall panels abstract an increasing number of mines in china are being subjected to overall instability induced oii rockbursts in extracting deep remnant island longwall panels causing severe damage at far larger scale and intensity compared with common local rockbursts using the island longwall panel lw1305 at zhaolou coal mine as a case example this paper investigates the mechanism of the newly defined oii rockburst by means of stress and microseismic monitoring and then proposes a straightforward risk assessment method for oii rockbursts based on the actual bearing index in an attempt to provide guidelines for making engineering judgement the proposed risk assessment method was successfully applied to lw1305 and the assessment result is supported by the occurrence of an oii rockburst in lw1305 and further verified by numerical modeling and microseismic monitoring

lithosphere atmosphere ionosphere coupling laic model an unified concept for earthquake precursors validation abstract the paper presents a conception of complex multidisciplinary approach to the problem of clarification the nature of short term earthquake precursors observed in atmosphere atmospheric electricity and in ionosphere and magnetosphere our approach is based on the most fundamental principles of tectonics giving understanding that earthquake is an ultimate result of relative movement of tectonic plates and blocks of different sizes different kind of gases methane helium hydrogen and carbon dioxide leaking from the crust can serve as carrier gases for radon including underwater seismically active faults radon action on atmospheric gases is similar to the cosmic rays effects in upper layers of atmosphere it is the air ionization and formation by ions the nucleus of water condensation condensation of water vapor is accompanied by the latent heat exhalation is the main cause for observing atmospheric thermal anomalies formation of large ion clusters changes the conductivity of boundary layer of atmosphere and parameters of the global electric circuit over the active tectonic faults variations of atmospheric electricity are the main source of ionospheric anomalies over seismically active areas lithosphere atmosphere ionosphere coupling laic model can explain most of these events as a synergy between different ground surface atmosphere and ionosphere processes and anomalous variations which are usually named as short term earthquake precursors a newly developed approach of interdisciplinary space terrestrial framework istf can provide also a verification of these precursory processes in seismically active regions the main outcome of this paper is the unified concept for systematic validation of different types of earthquake precursors united by physical basis in one common theory

mixed carbonate siliciclastic sedimentation along the great barrier reef upper slope a challenge to the reciprocal sedimentation model abstract results of studies involving numerous cores and odp holes along the great barrier reef gbr margin and adjacent queensland trough and queensland plateau have challenged the use of a reciprocal sedimentation model to describe the sedimentary response of slope and basin settings to glacioeustatic sea level fluctuations upper slope sedimentation results from the relationships between sea level fluctuations antecedent topography and regional climate that play an important role in the type and amount of sediment deposited on the upper slope during glacial deglacial and interglacial times during the last glacial maximum lgm 20 ka ago upper slope sediments generally lacked siliciclastic material and are characterized by very low accumulation rates whereas early deglacial time termination i ti deposits are dominated by a siliciclastic and neritic carbonate pulse siliciclastic sedimentation was significantly reduced in the holocene while carbonate sedimentation remains elevated a new borehole iodp expedition 325 hole m0058a hole 58a recovered 82 of a 40 4 m hole on the upper slope east of noggin passage on the central gbr margin near cairns australia hole 58a provides a detailed sedimentary record during termination ii tii marine isotope stage 6 5e mis 6 5e deglacial transition and through most of interglacial mis 5 this hole along with two others odp leg 133 holes 820a and 819a from the upper slope east of grafton passage show carbonate siliciclastic cyclicity as the result of glacioeustatic change with the gbr shelf sedimentation at hole 58a is consistent with that of previous studies along the gbr margin focusing on the lgm to present and extends the upper slope sedimentary record back to tii and interglacial mis 5 a siliciclastic pulse similar to the one during ti occurred during the penultimate deglaciation tii however the maximum neritic aragonite export to the upper slope occurred not during peak mis 5e highstand when sea level was a few meters above modern position but subsequently during a time mis 5d to 5a when lowered sea level fluctuated between 30 and 50 m below present sea level siliciclastic sediments were reworked and exported to the upper slope when the lowstand fluvial plain was re flooded whereas neritic carbonate export to the slope reached a maximum when sea level fell and much of the mid to outer shelf re entered the photic zone subsequent to a drowning interval thus this analysis refines the mixed sedimentation models of upper slope sedimentation along the central gbr margin during the penultimate deglacial transgression and subsequent interglacial early and late highstand this study provides further evidence that mixed carbonate siliciclastic margins do not always behave in a predictable manner and that mixed margins both modern and ancient would benefit from detailed study of sediment transport in the context of sea level rise and fall

tropical view of quaternary sequence stratigraphy siliciclastic accumulation on slopes east of the great barrier reef since the last glacial maximum generic models of continental margin evolution predict that siliciclastic fluxes to slopes should be maximal and minimal during major sea level lowstands and transgressions respectively here we document the opposite for the northeast australian margin the largest extant mixed siliciclastic carbonate depositional system cores from slopes of this margin consistently contain siliciclastic rich intervals 0 3 1 m thick in the upper few meters radiocarbon dates of planktonic foraminifera show that this interval was deposited between 12 and 7 ka and represents greatly increased siliciclastic fluxes during late transgression this massive terrigenous discharge to slopes occurred along at least 450 km of the margin irrespective of modern variations in bathymetry or climate although we cannot dismiss a significantly different early holocene climate with greatly enhanced sediment discharge available data instead suggest that rivers aggraded on the shelf during lowstand because of an extensive subaerially exposed reef system this phenomenon may occur on other margins rimmed by reefs requiring a major revision of concepts used to interpret mixed siliciclastic carbonate systems

reduction of electron temperature in low latitude ionosphere at 600 km before and after large earthquakes 1 we examine ionospheric electron temperatures te observed by hinotori satellite during three earthquakes m6 6 occurred in november 1981 m7 4 and m6 6 in january 1982 over philippine respectively it is found that t e around the epicenters significantly decreases in the afternoon periods within 5 days before and after the three earthquakes the region of ionosphere disturbance extends to 80 120 degrees in longitude a tendency exists that duration of the disturbance becomes longer as the increase of earthquake magnitude f 2 peak frequency f o f 2 and virtual height h f from a chain of 4 ionosonde stations located in the longitude zone of 120 e 130 e are used together with electron density n e that is observed simultaneously onboard hinotori satellite to find possible cause mechanisms of the abnormal reduction of electron temperatures behavior of hinotori t e n e and ionosonde f o f 2 h f implies the existence of westward electric field over epicentre our finding suggests that simple two plasma instruments might be able to play a fundamental role to study ionosphere disturbance associated with earthquake if the constellation of small mini satellites is organized and the orbits are properly chosen

electrodynamic response of the ionosphere to high speed solar wind streams 1 a combination of dawn and dusk observations from the dmsp f13 satellite and output from the thermosphere ionosphere electrodynamics general circulation model tie gcm are used to study the electrodynamic response of the ionosphere to quasi 9 day recurrent geomagnetic activity driven by solar wind high speed streams during 2005 superposed epoch analysis of the zonal and vertical plasma drifts reveal that significant electrodynamic perturbations occur in response to the high speed streams during 2005 the peak response occurs around 0 5 days after the high speed stream interface and the drift perturbations slowly relax back to quiet levels over 4 6 days the observed and modeled zonal drift perturbations are in good agreement near dusk however the amplitude of the zonal drift perturbations at dawn slightly differ at low and midlatitudes the modeled drift perturbations are westward at all local times with the largest westward drifts occurring near midnight at dawn the dmsp observations at low and midlatitudes reveal 20 m s 1 eastward drift perturbations while the tie gcm simulates weaker eastward drifts at midlatitudes and westward drifts in the equatorial region at dusk the low and midlatitude perturbation drifts are 10 20 m s 1 westward in both the dmsp observations and tie gcm simulations owing to equatorial expansion and strengthening of the high latitude two cell convection pattern the high latitude zonal drift perturbations are eastward in the morning and westward in the afternoon and evening less agreement is present between the simulated and observed vertical drift perturbations near dawn at all latitudes upward drift perturbations are revealed by both the tie gcm simulation 5 m s 1 and dmsp observations 10 15 m s 1 however at dusk the dmsp observes an upward drift perturbation on the order of 25 35 m s 1 while the tie gcm simulates vertical drift perturbations less than 10 m s 1 the disagreement may be related to errors in the dmsp observations or deficiencies in the model based on the results presented we conclude that the disturbance dynamo mechanism is an important mechanism for driving the electrodynamic response at dawn and dusk to recurrent geomagnetic activity driven by solar wind high speed streams

massive siliciclastic discharge to slopes of the great barrier reef platform during sea level transgression constraints from sediment cores between 15 s and 16 s latitude and possible explanations abstract the northeast australian continental margin including the great barrier reef gbr platform provides an outstanding modern analogue for understanding sedimentation in tropical mixed siliciclastic carbonate depositional systems previous studies of cores from this margin have suggested that in contrast to widely accepted models maximum siliciclastic fluxes to slopes over the last 30 ky occurred when sea level transgressed the shelf ca 11 7 ka rather than when sea level was at a lowstand before 18 ka however climate and bathymetry can affect regional sediment deposition significantly and the cores examined to date have come from the southern queensland trough where the margin has a wet tropical climate and a broad shelf 50 km with gradual slopes in this study we examine the abundance and accumulation of siliciclastic material in four cores from lower slopes of the northern queensland trough where rivers drain a drier region and debouche onto a narrow shelf with steep incised slopes similar to previously examined cores all cores contain a dark greyish brown horizon within the upper few meters this horizon represents a low in carbonate content and corresponding high in siliciclastic material primarily clay and oxygen isotope stratigraphy shows that it was deposited during late transgression nominally between 11 and 7 ka moreover mass accumulation rate calculations demonstrate that this horizon reflects a significant rise in siliciclastic fluxes when combined with the previous work to the south it appears that slopes all along a large portion of the northeast australian continental margin received greatly enhanced inputs of siliciclastic material during late transgression independent of proximal climate and bathymetry two general explanations are offered for this observation 1 climate change induced highly variable riverine discharge over the past 30 ky with a prominent maximum coincident with late transgression or 2 the shelf stores large quantities of siliciclastic sediment during lowstand and releases this material to the slope during late transgression in either case siliciclastic accumulation on the northeast australia continental margin behaves completely opposite to predictions from conventional models

microfacies and diagenesis of older pleistocene pre last glacial maximum reef deposits great barrier reef australia iodp expedition 325 a quantitative approach during integrated ocean drilling program expedition 325 34 holes were drilled along five transects in front of the great barrier reef of australia penetrating some 700 m of late pleistocene reef deposits post glacial largely 20 to 10 kyr bp in water depths of 42 to 127 m in seven holes drilled in water depths of 42 to 92 m on three transects older pleistocene older than last glacial maximum 20 kyr bp reef deposits were recovered from lower core sections in this study facies diagenetic features mineralogy and stable isotope geochemistry of 100 samples from six of the latter holes were investigated and quantified lithologies are dominated by grain supported textures and were to a large part deposited in high energy reef or reef slope environments quantitative analyses allow 11 microfacies to be defined including mixed skeletal packstone and grainstone mudstone wackestone coral packstone coral grainstone coralline algal grainstone coral algal packstone coralline algal packstone halimeda grainstone microbialite and caliche microbialites that are common in cavities of younger post glacial deposits are rare in pre last glacial maximum core sections possibly due to a lack of open framework suitable for colonization by microbes in pre last glacial maximum deposits of holes m0032a and m0033a 20 kyr bp marine diagenetic features are dominant samples consist largely of aragonite and high magnesium calcite holes m0042a and m0057a which contain the oldest rocks 169 kyr bp are characterized by meteoric diagenesis and samples mostly consist of low magnesium calcite holes m0042a m0055a and m0056a 30 kyr bp and a horizon in the upper part of hole m0057a contain both marine and meteoric diagenetic features however only one change from marine to meteoric pore water is recorded in contrast with the changes in diagenetic environment that might be inferred from the sea level history values of stable isotopes of oxygen and carbon are consistent with these findings samples from holes m0032a and m0033a reflect largely positive values 18o 1 to 1 and 13c 1 to 4 whereas those from holes m0042a and m0057a are negative 18o 4 to 2 and 13c 8 to 2 holes m0055a and m0056a provide intermediate values with slightly positive 13c and negative 18o values the type and intensity of meteroric diagenesis appears to have been controlled both by age and depth i e the time available for diagenetic alteration and reflects the relation between reef deposition and sea level change

longitudinal structure of the equatorial anomaly in the nighttime ionosphere observed by image fuv 1 the far ultraviolet imager fuv on board the image satellite provides an instantaneous global view of the oi 135 6 nm nightglow with 2 min time resolution because the oi 135 6 nm emission from the nighttime ionosphere is determined by the line of sight integrated plasma density the nightglow images are useful for studying the nighttime low latitude ionosphere globally with the image fuv 135 6 nm observations from march to june 2002 we have examined the global characteristics of the nighttime equatorial anomaly ea by constructing a constant local time map lt map in which pixels within an assigned local time range are extracted from the image fuv nightglow images obtained over an observation period of 3 days or more and are put together to compose a global distribution map of emission intensities at that local time these lt maps show that the development of the ea has a significant longitudinal structure in which peaks and dips of the crest emission intensity and the crest latitude have about 90 longitudinal separation in the longitude range from 0 to 250 although there is not enough data over the american sector this result suggests that the ea longitudinal structure has a prominent zonal component of the wave number 4 the observed longitudinal structure of the nighttime ea could not be fully explained by factors such as the empirical electric field and neutral wind models the geomagnetic declination angle or the displacement of the geomagnetic equator from the geographic equator to explain the observed longitudinal structure of the ea in particular the wave number 4 feature we may need to consider other forcing for example nonmigrating tide originated from the lower atmosphere

assessment and mitigation of coal bump risk during extraction of an island longwall panel abstract this study presents an integrated approach for field tests and numerical investigations to assess the risk of coal bumps this approach produces a stress relief technology using boreholes to mitigate risk during the extraction of an island longwall panel the field tests were conducted in an island longwall panel in the tangshan coal mine in the city of tangshan china in these tests roadway roof displacement and electromagnetic radiation emr of roadways in the panel were investigated to determine the zones of intensive roof deformation a numerical model flac 3d fast lagrangian analysis of continua in 3 dimensions was established to understand the results of the field tests and to map the zones in the panel with a high risk for coal bumps the results of the field tests and the numerical modeling show that the roof deformation starts to occur at more than 30 m ahead of the longwall face and the deformation starts to accelerate after a distance of 10 m in front of the longwall face large and rapid roof deformation is considered to be an important precursor of coal bump occurrence during the extraction of an island longwall panel based on these results a stress relief technology using boreholes was investigated through numerical methods the modeled results suggest that the abutment stress could be released by drilling boreholes in the zones prone to coal bumps the effectiveness of the stress release increased with the borehole length and decreased with the borehole spacing

radiocarbon calibration curve spanning 0 to 50 000 years bp based on paired 230 th 234 u 238 u and 14 c dates on pristine corals abstract radiocarbon dating is the most widely used dating technique in the world recent advances in accelerator mass spectrometry ams and sample preparation techniques have reduced the sample size requirements by a factor of 1000 and decreased the measurement time from weeks to minutes today it is estimated that more than 90 percent of all measurements made on accelerator mass spectrometers are for radiocarbon age dates the production of 14 c in the atmosphere varies through time due to changes in the earth s geomagnetic field intensity and in its concentration which is regulated by the carbon cycle as a result of these two variables a radiocarbon age is not equivalent to a calendar age four decades of joint research by the dendrochronology and radiocarbon communities have produced a radiocarbon calibration data set of remarkable precision and accuracy extending from the present to approximately 12 000 calendar years before present this paper presents high precision paired 230 th 234 u 238 u and 14 c age determinations on pristine coral samples that enable us to extend the radiocarbon calibration curve from 12 000 to 50 000 years before present we developed a statistical model to properly estimate sample age conversion from radiocarbon years to calendar years taking full account of combined errors in input ages and calibration uncertainties our radiocarbon calibration program is publicly accessible at http www radiocarbon ldeo columbia edu along with full documentation of the samples data and our statistical calibration model

late quaternary shedding of shallow marine carbonate along a tropical mixed siliciclastic carbonate shelf great barrier reef australia the north east australian margin is the largest modern example of a tropical mixed siliciclastic carbonate depositional system with an outer shelf hosting the great barrier reef gbr and an inner shelf dominated by fluvially sourced siliciclastic sediment wedges the long term interplay between these sediment components and sea level is recorded in the queensland trough a 1 2 km deep n s elongate basin situated between the gbr platform and the queensland plateau in this paper 154 samples from 45 surface grabs and six well dated piston cores were analysed for total carbonate content carbonate mineralogy and sr concentration to establish spatial and temporal patterns of carbonate accumulation in the queensland trough over the last 300 kyr surface carbonate contents are lowest on the inner shelf 5 and in the trough axis 60 because of siliciclastic dilution carbonate on the shelf is mostly sr rich aragonite and high mg calcite hmc whereas that in the basin is mostly low mg calcite once normalized to remove the effects of siliciclastic dilution surface sr rich aragonite and hmc abundances decrease linearly to background levels 100 km seaward of the shelf edge core samples show that over time normalized aragonite and sr abundances are greatest during periods of shelf flooding and lowest when sea level drops below the shelf edge this is consistent with changes in the production of coral and calcareous algae and the shedding of their debris from the shelf interestingly normalized hmc concentrations on the slope peak during periods of major transgression perhaps because of maximum off shelf transport from inter reef areas or intermediate water dissolution after accounting for siliciclastic dilution there are strong similarities in both spatial and temporal patterns of carbonate minerals between slopes and basins of the north east australian margin and those of pure carbonate margins such as the bahamas a limited set of basic processes including the formation and breakdown of carbonate on the shelf the transport of carbonate off the shelf and eustatic sea level probably controls carbonate accumulation in slope and basin settings of tropical environments irrespective of proximal siliciclastic sediment sources

physical mechanisms of the ionospheric storms at equatorial and higher latitudes during the recovery phase of geomagnetic storms 1 the paper studies the physical mechanisms of the ionospheric storms at equatorial and higher latitudes which are generally opposite both during the main phase mp and recovery phase rp of geomagnetic storms the mechanisms are based on the natural tendency of physical systems to occupy minimum energy state which is most stable the paper first illustrates the recent developments in the understanding of the mechanisms during daytime mps when generally negative ionospheric storms in nmax and tec develop at equatorial latitudes and positive storms occur at higher latitudes including why the storms are severe only in some cases the paper then investigates the relative importance of the physical mechanisms of the positive ionospheric storms observed at equatorial latitudes within 15 during daytime rps when negative storms occur at higher latitudes using champ ne and gps tec data and sheffield university plasmasphere ionosphere model the results indicate that the mechanical effect of the storm time equatorward neutral winds that causes plasma convergence at equatorial f region could be a major source for the positive storms with the downwelling effect of the winds and zero or westward electric field if present acting as minor sources

shelf edge delta and reef development on a mixed siliciclastic carbonate margin central great barrier reef the great barrier reef gbr is the world s largest extant mixed silicilastic carbonate margin previous research on the great barrier reef has suggested that the extensive barrier reef system may act as an impermeable barrier and limit the development of delta systems during lowstands but sufficient geophysical data to support this hypothesis are lacking we use dense sparker seismic and sub bottom profiler data to better understand the structure of a large lobe shaped feature 10 km 10 km on the shelf edge of the central gbr and the interactions between siliciclastic and carbonate sedimentary systems interpreted sparker seismic contains prograding clinoforms and suggest that the lobe shaped feature was a river dominated shelf edge delta a delta on the shelf edge implies that the presence of an exposed barrier reef was not a major impediment to deposition and that other adjacent lobe shaped features are also deltaic deposits the shelf edge deltas were deposited onto a broad upper slope terrace that allowed continued progradation and limited incision when sea level fell below the shelf edge delta foresets are commonly colonized by coral reefs but the spatial and temporal relationship between reefs and some deltaic units remains unclear the presence of multiple shelf edge deltas that link to previously mapped burdekin river paleo channels indicates a complex history of sedimentation with the burdekin river delta migrating up to 100 km along the gbr margin during the late quaternary regional bathymetric data suggest that large modern or recent shelf edge deltas are rare on the gbr and that there was a broad range of sedimentary processes operating along the margin of the gbr during periods of low sea level

late quaternary stream sedimentation in the humid tropics a review with new data from ne queensland australia there is now a wide agreement that temperature depression in the humid tropics during the last glacial maximum lgm was at least 5 c most estimates of precipitation reduction at the lgm range from 25 30 to 50 65 based on proxy data but the recent ccm1 model envisages only around 12 dates obtained from river sediments indicate major changes to fluvial activity in the late quaternary isotope zone 3 sediments 58 28 ka bp are widespread and possibly indicate cooler conditions post 28 ka bp and certainly post 21 ka bp river regimes altered radically towards fan building braiding or major reduction in all activity this paper reports on fan formation in ne queensland between 26 and 14 ka bp and reviews evidence for comparable changes in humid tropical areas of s america w africa and se asia including records of holocene sedimentation within a global rhythm of major changes to river regimes in the humid tropics during the late quaternary it is now possible to detect regional variations in stream response to climatic change at the lgm reductions in stream power may have led to fan formation in ne queensland while vegetation changes may have contributed to increased sediment loads and braiding in some forest marginal areas but in w africa greater aridity may have been responsible for enfeebled streams leaving few records channel cutting then deposition of coarse sediment in braided rivers marked the transition to the early holocene in w africa and fans became entrenched in ne queensland this regime persisted until forest recovery was complete by 9 5 8 5 ka bp when widespread overbank deposition occurred and a change towards meandering channels took place widely across the humid tropical zone followed by several cut and fill episodes in the middle and late holocene

latitudinal distribution of anomalous ion density as a precursor of a large earthquake 1 data obtained by the u s satellite de 2 are used to investigate possible precursor features in the ionosphere associated with a large earthquake latitude 33 13 longitude 73 07 m 7 5 which occurred during a moderate geomagnetic disturbance atomic oxygen ion and molecular ion distributions show characteristic latitudinal features similar to the well known equatorial ionization anomaly eia feature but centered around the earthquake epicenter we name this the precursor ionization anomaly pia the density minima of both the atomic oxygen and molecular ions are in two latitude zones depending on the distance from the epicenter one of the pia minima aligns with the geomagnetic latitude crossing the epicenter another minimum is found along the geographic latitude of the epicenter these minima are located in an area spanning about 40 in latitude and about 140 in longitude it is noted that the molecular ion minimum is more clearly defined even when the atomic ion density minimum is not indicated clearly the ion density reduction seems to be caused by a superposition of natural quiet time ionospheric eastward electric field and an electric field associated with the earthquake although we studied one single event our careful examination of results suggests that the location and day of occurrence of the pia can be predicted for some large earthquakes even during moderate geomagnetic disturbance if the satellite orbit is properly chosen

links between climate and sea levels for the past three million years the oscillations between glacial and interglacial climate conditions over the past three million years have been characterized by a transfer of immense amounts of water between two of its largest reservoirs on earth the ice sheets and the oceans since the latest of these oscillations the last glacial maximum between about 30 000 and 19 000 years ago approximately 50 million cubic kilometres of ice has melted from the land based ice sheets raising global sea level by approximately 130 metres such rapid changes in sea level are part of a complex pattern of interactions between the atmosphere oceans ice sheets and solid earth all of which have different response timescales the trigger for the sea level fluctuations most probably lies with changes in insolation caused by astronomical forcing but internal feedback cycles complicate the simple model of causes and effects

suspected seismo ionospheric coupling observed by satellite measurements and gps tec related to the m7 9 wenchuan earthquake of 12 may 2008 anomalous changes in the ionospheric conditions related to the wenchuan earthquake of 12 may 2008 are investigated using electron density ne from detection of electro magnetic emissions transmitted from earthquake regions demeter and champ satellites electric field from demeter and gps total electron content tec maps the normalized ne from the demeter satellite reveal that the previously reported tec increments before the earthquake can be considered as fragments of the gradual equatorial ionization anomaly eia enhancements near the epicenter longitude that began approximately 1 month before the earthquake and reached its maximum with an exceptionally large strength index 8 days prior to the main shock this feature is indirectly confirmed through the champ ne and gps tec data following the eia intensity peak disturbances in the ne and o density were observed in the nightside based on the concurrent electric field and ne changes it is suggested that eia intensification could be triggered by the e field disturbances over the epicenter