sediment provenance and paleoenvironmental change in the ulleung basin of the east japan sea during the last 21 kyr despite the well reconstructed paleoceanography of the late quaternary deposits in the east japan sea es provenances of terrigenous sediments and a comprehensive interpretation of their variations since the last glacial maximum remain unclear especially in regard to the mainland china and taiwan derived matter grain size conservative trace elements rare earth elements rees nd isotope and clay mineralogy of core sediments from the ulleung basin of the es were investigated for better understanding of detrital sediment provenance and transport process and then their forcing mechanisms over the last 21 kyr geochemical mineralogical multi indices in this study showed notable three phase changes in sediment provenance which can be closely related to sea level fluctuation development of the tsushima warm current as well as intermittent influence from the east asian summer monsoon climate evolution during unit 1 21 1 8 4 kyr bp when the tsushima warm current was absent in the es the paleo changjiang and the paleo huanghe mouth might be situated close to the study area and thus mainland china could have played major role in the southwestern ulleung basin sedimentation in particular the formation of rhythmic dark colored alternation in unit 1 is possibly attributable to the pulse of paleo huanghe discharge associated with centurial to millennial scale variability in the east asian summer monsoon in unit 2 8 4 7 2 kyr bp these river mouths gradually retreated to their present positions with global sea level rise leading to decreasing terrigenous sediment supply from mainland china to the study area since 7 2 kyr bp unit 3 sedimentation in the ulleung basin should still be mainly derived from mainland china meanwhile increasing chlorite kaolinite ratio but decreasing epsilon nd value revealed that terrigenous matter from taiwan might have been limitedly transported northward to the study area by the fully evolved tsushima warm current a prominent decline in chlorite kaolinite ratio together with contrast change on epsilon nd value centered at around 2 9 kyr bp 3 3 2 4 kyr bp may have been caused by the tsushima warm current suppression possibly related to the pulleniatina minimum event popularly found in the study area and nearby seas c 2014 elsevier ltd all rights reserved

dry cave deposits and their palaeoenvironmental significance during the last 115 ka sodmein cave red sea mountains egypt the sodmein cliff foot cave is the present day remnant of an ancient cavity probably of karstic origin physical breakdown of the limestone bedrock rather than solution has governed its subsequent evolution long before 115 ka bp an estimated 8000 m 3 of debris came off the weathered roof and mixed with contemporaneous cliff rockfall over 4 m of sediments have since accumulated wet conditions outside the cave during isotopic stage 5e are documented by sedimentary properties of the j complex and by its detailed botanical and faunal content these wet conditions were of regional significance shortly after 115 ka bp further subsidence of the roof of the ancient cave led to the present day cave form the cave interior has remained dry up to the present but the deposits indicate an increase of animal passage and plant growth around 25 ka bp and during the holocene interglacial the latter period was rather arid in absolute terms receiving less precipitation under a less regular pluvial regime compared with the interglacial during isotopic stage 5e r 2002 elsevier science ltd all rights reserved

rapid flooding of the sunda shelf a late glacial sea level record the increase in sea level from the last glacial maximum has been derived from a siliciclastic system on the tectonically stable sunda shelf in southeast asia the time from 21 to 14 thousand calendar years before the present has been poorly covered in other records the record generally confirms sea level reconstructions from coral reefs the rise of sea level during meltwater pulse 1a was as much as 16 meters within 300 years 14 6 to 14 3 thousand years ago

deep sea records of the continental weathering and erosion response to east asian monsoon intensification since 14 ka in the south china sea we analyzed sediment from ocean drilling program odp site 1144 in the northern south china sea to examine the weathering response of se asia to the strengthening of the east asian monsoon eam since 14 ka our high resolution record highlights the decoupling between continental chemical weathering physical erosion and summer monsoon intensity mass accumulation rates ti ca k rb hematite goethite and sr 87 sr 86 show sharp excursions from 11 to 8 ka peaking at 10 ka clay minerals show a shorter lived response with a higher kaolinite illite chlorite ratio at 10 7 9 5 ka however not all proxies show a clear response to environmental changes magnetic susceptibility rises sharply between 12 and 11 ka grain size becomes finer from 14 to 10 ka and then coarsens until similar to 7 ka but is probably controlled by bottom current flow and sealevel sr and nd isotopes show that material is dominantly eroded from taiwan with a lesser flux from luzon while clay mineralogy suggests that the primary sources during the early holocene were reworked via the shelf in the taiwan strait rather than directly from taiwan erosion was enhanced during monsoon strengthening and caused reworking of chemically weathered pleistocene sediment largely from the now flooded taiwan strait which was transgressed by similar to 8 ka cutting off supply to the deep water slope none of the proxies shows an erosional response lasting until similar to 6 ka when speleothem oxygen isotope records indicate the start of monsoon weakening although more weathered sediments were deposited from 11 to 8 ka when the monsoon was strong these are reworked and represent more weathering during the last glacial maximum lgm when the summer monsoon was weaker but the shelves were exposed c 2012 elsevier b v all rights reserved

understanding sedimentation in the song hong yinggehai basin south china sea the cenozoic song hong yinggehai basin in the south china sea contains a large volume of sediment that has been used in previous studies together with regional geomorphology to argue for the existence of a large palaeodrainage system that connected eastern tibet with the south china sea to test this and to understand the significance of sediment volumes deposited in the song hong yinggehai basin this study compared erosion histories of source regions with sediment volumes deposited during the two main stages in basin evolution spanning active rifting and subsidence 30 15 5 ma and postrift sedimentation 15 5 ma to present the study of basin provenance by detrital zircon u pb dating revealed hainan was an important and continuous source of sediment and a bedrock thermochronological study quantified its overall contribution to basin sedimentation comparison between the accumulated mass of basin sediment and volumes of eroded bedrock calculated from apatite thermochronometry across the modern red river drainage in northern vietnam as well as hainan island accounted for the bulk of sediment deposited since 30 ma consequently if an expanded paleodrainage ever existed it must have predated the oligocene

sr and nd isotopes in river sediments from the ganga basin sediment provenance and spatial variability in physical erosion 1 sr and nd concentrations and isotope compositions in sediment of the ganga river from gangotri to rajmahal and its tributaries have been measured to determine provenance and the spatial variability in physical erosion among the ganga subbasins sr and nd in silicates range from 37 to 138 and from 10 to 36 g g with 87sr 86sr and nd of 0 7474 0 8428 and 25 5 to 15 5 respectively the results suggest that 65 of ganga mainstream sediments are derived from the higher himalayan crystallines highlighting intense physical erosion in this region the 87sr 86sr values of sediments in the gangetic plain show nearly identical trends during two seasons with a sharp and significant decrease at barauni downstream of gandak confluence this brings out the major impact of the sediment contribution from the gandak to the ganga mainstream model calculation suggests that about half of the ganga sediment at rajmahal is sourced from the gandak the erosion rates in the himalayan subbasins of the ganga range between 0 5 and 6 mm a where a is years with the gandak having the highest erosion rate high relief and intense precipitation over the headwater basins of the gandak appear to drive the rapid and focused erosion of this basin the results of this study and those in literature suggest that the eastern syntaxis brahmaputra the western syntaxis indus and the gandak have much higher physical erosion rates than the other himalayan basins focused erosion in the hot spots of these river basins contributes significantly to the global riverine sediment budget and influence regional tectonics

increased contribution of terrigenous supply from taiwan to the northern south china sea since 3 ma seismic profiles provide evidence that there has been strong transport by deep water bottom currents and drift deposition on the northern slope of the south china sea earlier geochemical studies suggest that the drift sediments originated primarily from taiwan however the transport process history and origin of the deep water bottom deposition in the northern south china sea on both glacial interglacial and tectonic time scales remain unclear here we show new high resolution records of clay minerals grain size and mass accumulation rate mar of terrigenous materials from ocean drilling program odp site 1144 together with trace element concentrations in siliciclastic sediments from odp site 1146 combined with other published data we find that the primary source for sediments at odp sites 1144 1148 since 3 ma is from taiwan and not from pearl river as previously thought before 3 ma however sediment source to odp sites 1146 and 1148 was mainly from the pearl river increased contribution of terrigenous supply from taiwan to the northern south china sea since similar to 3 ma may be related to the formation of the taiwan orogen and strengthening of deep water bottom current transport in the northern south china sea variations in clay mineralogy and sedimentology at odp site 1144 located on a sediment drift shows strong glacial interglacial cyclicity this suggests that bottom current deposition is highly dependent on sea level fluctuations which control the terrigenous supply to the deep sea c 2010 elsevier b v all rights reserved

geochemical records of taiwan sourced sediments in the south china sea linked to holocene climate changes we present a multi proxy geochemical analysis of core kng5 retrieved from the northern south china sea slope spanning the last 13 0 ka bp to assess the response of weathering and erosion processes in the southwestern taiwan river basin to climate change a provenance analysis indicates that the core sediments were primarily derived from the southwestern taiwan river and can be used to reconstruct the erosion and or weathering history of this river basin the chemical index of alteration the plagioclase index of alteration rb sr al ti principle component 1 and k al combined with terrigenous mass accumulation rates and the proportion of clay exhibit sharp excursions from 12 0 to 5 5 ka peaking at 10 0 ka which suggests strong chemical weathering and physical erosion during the early mid holocene the period of the maximum summer monsoon abrupt falling weathering trends during 5 2 and 3 5 ka bp correlate with a weaker monsoon after 3 5 ka bp a stable lower weathering trend to the present day was evident indicating the deposition of less weathered sediments in the slope when the monsoon rainfall was weakening a good correlation between our proxy records of chemical weathering and variations of the monsoon intensity in south china emphasizes that variation in monsoon intensity is most likely the primary drive of the intensity of weathering and erosion in southwestern taiwan river sediments over the last 13 0 ka bp finally we concluded that geochemical parameters can be used as reliable proxies for climate variation on a millennial centennial time scale in such areas as taiwan where weathering limited regimes exist c 2015 elsevier b v all rights reserved

an integrated approach for identifying aquifers in transcurrent fault systems the najd shear system of the arabian nubian shield groundwater potentials were assessed for major transcurrent fault systems in basement complex terrains using the najd transcurrent shear system of the arabian nubian shield as a test case spatial analysis within a geographical information system environment of relevant data sets field remote sensing geophysical and digital elevation revealed a spatial correlation between existing well locations and distribution of najd transcurrent shear system structural elements i e faults shear zones melange dykes within highly fractured domains suggesting a causal relationship specifically at 1 intersection of najd brittle shear zones and fault systems 2 intersections of two or more fault systems 3 intersections of najd related dykes with the main streams within catchment areas and 4 within tectonic melange for each of the former aquifer types aquifer specific field and satellite based characteristics were identified and used in conjunction with complementary data e g watershed morphology precipitation soil moisture to target aquifers of similar settings postulated well locations were then successfully tested and refined using very low frequency technologies results could potentially highlight the important role of major transcurrent fault systems in providing settings conducive for hosting and transmitting groundwater and could potentially serve as a replicable model for regional assessment of groundwater potentials in similar tectonic and hydrologic settings

palaeohydrology and its impact on groundwater in arid environments gebel duwi and its vicinities eastern desert egypt abstract from ancient times access to water in arid and hyper arid regions has been crucial for life increased knowledge about groundwater conditions is therefore extremely important for the future development of desert areas gebel duwi a limestone ridge sited in the today hyper arid eastern desert of egypt was chosen for testing current hypotheses concerning the interdependence of palaeohydrologic features and geologic settings for groundwater investigations two sub basins are identified in affecting gebel duwi wadi nakheil and wadi sodmein both have extraordinary high stream order indicating the reality of a very old drainage system several additional palaeohydrologic features such as wadi terraces alluvial fans and playa deposits are also recorded in these sub basins these features as well as finds from an important archaeological site sodmein cave provide information about palaeoenvironmental changes and wetter climatic periods in the younger geologic past mainly in the late pleistocene and holocene which have affected the occurrence of present day groundwater this study combines new results of geological and geomorphological field studies examinations of digital elevation models as well as of rock and water analyses in an integrated approach resulting maps comprise landforms lithology elevation drainage lines slope structural lineaments and flow directions the hydrogeologic condition indicates suitable locations for groundwater recharge and accumulation the research presented is interdisciplinary in approach and is recommended for future studies with regard to groundwater exploration sustainable groundwater use and the protection of archaeological sites in arid lands

u pb dating of discordant 0 1 ma old secondary u minerals abstract a modified tera wasserburg u pb concordia plot which takes care of initial disequilibrium of radioactive daughter nuclides has been applied to date discordant torbernite samples from hohenstein northeast bavaria to 137 11ka lower intercept and 66 27ma upper intercept the secondary u pb age is supported by the 230 th 234 u disequilibrium age of 132 4 ka

clay minerals sr nd isotopes and provenance of sediments in the northwestern south china sea abstract the clay mineralogy and sr nd isotopic composition of sediments collected in the northwestern south china sea scs were investigated to understand sediment provenance and changes in the scs since the late pleistocene our results show that the clay mineral assemblages of the surface sediments are characterized by high amounts of illite and smectite and low amounts of kaolinite and chlorite the 87sr 86sr ratios of the surface sediments vary from 0 709617 to 0 734416 and end values range from 11 6 to 8 3 the clay minerals and sr nd isotope records suggest that sediments in the northwestern scs are derived from multiple sources the sediments deposited in the eastern shelf offshore of hainan originate predominantly from hainan island and south china whereas sediments in the western shelf offshore of hainan are derived mainly from indochina and hainan island however sediment source and transport mechanisms in the northwestern slope of the scs are more complicated our results suggest that input from the west may be the major sediment source but regions in the east taiwan and luzon also contribute part of the terrigenous materials downcore variations of sr nd isotopic composition in core sediments show clear glacial interglacial fluctuations higher 87sr 86sr ratios occur during glacial period indicating that the input of terrigenous materials from old continental rocks becomes one of the important sediment sources during these periods the exposure of continental shelf and southward migration of the coastline during the glacial sea level lowstand led to an increase of terrigenous supply to the northwestern slope of the scs the paleo red river and indochina are also potentially important contributors

one million year old groundwater in the sahara revealed by krypton 81 and chlorine 36 measurements of 81 kr kr in deep groundwater from the nubian aquifer egypt were performed by a new laser based atom counting method 81 kr ages range from 2 10 5 to 1 x 10 6 yr correlate with 36 cl cl ratios and are consistent with lateral flow of groundwater from a recharge area near the uweinat uplift in sw egypt low 2 h values of the 81 kr dated groundwater reveal a recurrent atlantic moisture source during pleistocene pluvial periods these results indicate that the 81 kr method for dating old groundwater is robust and such measurements can now be applied to a wide range of hydrolugic problems

clay mineral distribution patterns in late neogene fluvial sediments of the subathu sub basin central sector of himalayan foreland basin implications for provenance and climate abstract the late neogene 6 0 5 ma fluvial succession of the subathu sub basin a part of the himalayan foreland basin comprises a 2 4 km thick pile of conglomerate grey and buff sandstone and mudstone representing middle and upper siwalik subgroup this basin is filled mainly by major trunk and piedmont drainage which are nearly perpendicular to each other the clay mineral assemblages of this sedimentary succession have illite 7 82 smectite 0 90 chlorite 2 23 and kaolinite 1 13 the grey sandstones have moderate to abundant smectite 23 90 whereas the buff sandstones have abundant illite 66 79 and low to absent smectite 0 14 the mudstones that dominates the succession 50 have clay mineral assemblages similar to grey and buff sandstones or intermediate proportion the temporal distribution of clay minerals in mudstones shows occasional intense zigzag pattern with either smectite 3 81 or illite 15 82 abundance the smectite rich grey sandstones and mudstones are deposited by trunk drainage and the illite rich buff sandstones and mudstones are deposited by piedmont drainage the intense zigzag distribution pattern of clay minerals in mudstone indicates interfingering of floods from trunk and piedmont drainages the interfingering was severe ranging between 4 8 and 3 36 ma and between 2 60 and 1 77 ma related to tectonic activity the association of smectite 36 bearing mudstones and piedmont source derived buff sandstone and conglomerate towards the upper part of the section above 1 77 ma suggests either floodwater of trunk drainage over spill on the fringe of piedmont alluvial fan or derivation from smectite bearing middle siwalik rocks exposed due to the activity of an intra foreland thrust ift in the piedmont zone the occurrence of smectite and its variable proportion with time suggests its probable derivation not only from the sparsely exposed basic rock in the catchment area but also from siliceous and metamorphic rocks under favourable climatic conditions between 6 and 0 5 ma

deep south china sea circulation 1 the analysis of an updated monthly climatology of observed temperature and salinity from the u s navy generalized digital environment model reveals a basin scale cyclonic circulation over the deep south china sea scs the cyclonic circulation lies from about 2400 m to the bottom the boundary current transport of the cyclonic circulation is around 3 0 sv our results suggest that the cyclonic circulation is mainly forced by the luzon overflow with bottom topography playing an important role the structures of potential temperature salinity and potential density in the deep scs are consistent with the existence of the cyclonic circulation specifically low salinity water is found in the interior region west of luzon island and surrounded by saline pacific water in boundary current regions to the north west and southwest our results show the potential density distribution and the corresponding cyclonic circulation in deep scs are primarily controlled by salinity variations in the deep basin

constraints on pleistocene pluvial climates through stable isotope analysis of fossil spring tufas and associated gastropods kharga oasis egypt abstract stable isotope analyses of fossil spring carbonates tufas and freshwater gastropods melanoides tuberculata from the currently hyperarid western desert of egypt indicate that this region received enough precipitation to support a small perennial lake during the height of the oxygen isotope stage 6 5e pluvial event and a substantial volume of spring discharge during prior pluvial phases tufa and gastropod oxygen isotope ratios are generally low relative to modern precipitation in the region confirming that the majority of pleistocene pluvial precipitation came from an atlantic source as determined by previous workers mean tufa 13c 2 pdb suggests a significant proportion of c4 vegetation in the recharge area of the tufa depositing springs while the paucity of tufas with 13c greater than 0 suggests that equilibrium between spring water and atmospheric co2 represented an endpoint for the evolution of spring water carbon though spring carbonate deposition requires a substantial increase in humidity in central egypt relative to modern conditions high variation in tufa 18o up to 4 within individual stratigraphic units as well as positive covariance between tufa carbon and oxygen isotope ratios reflect significant effects of evaporation on spring water during tufa formation similarity in 18o and 13c values of tufas from different stratigraphic units indicates that climatic conditions did not vary significantly among pluvial phases recorded by spring carbonate deposition the lack of substantial carbonate formation at tufa localities during the holocene pluvial phase however suggests that tufa deposition represents substantially wetter conditions than have existed during holocene time

the sedimentary and tectonic evolution of the yinggehai song hong basin and the southern hainan margin south china sea implications for tibetan uplift and monsoon intensification 1 the yinggehai song hong basin is one of the world s largest pull apart basins lying along the trace of the red river fault zone in the south china sea south of hainan island this basin crosscuts the rifted margin of the northern south china sea in this paper we present for the first time a regional compilation of multichannel seismic reflection data from both the strike slip and rifted margins the basins started to open after similar to 45 ma especially after similar to 34 ma the yinggehai basin was folded and inverted in the middle miocene after 21 ma in the north and 14 ma in the south before rapidly subsiding again after similar to 5 ma because of continued tectonism this subsidence has caused shale diapirism especially driven by associated sedimentation in the late pliocene 2 6 2 0 ma extension along the adjacent south hainan margin shows preferential lower crustal extension suggestive of lower crustal flow increasing toward the continent ocean transition during breakup sediment supply is reconstructed to peak in the middle miocene then falls between 14 and 10 3 ma to reach a low in the late miocene however rates rose again in the pliocene pleistocene the red river sediment budget is incompatible with climate models that propose stronger monsoon rains starting at 8 ma or with large scale river capture away from the red river after similar to 10 ma both lines of evidence point to major uplift in the red river drainage being middle miocene or older the recent preindustrial red river carried much more sediment than the average pleistocene accumulation rate indicating modest sediment buffering onshore at least in recent geologic time

holocene environmental changes in the gebel umm hammad eastern desert egypt abstract gebel umm hammad in the red sea mountains east of quseir egypt today enjoys small but irregular amounts of winter rain enabling the widening of joint controlled openings in the thebes limestone cavities are especially affected by flaking while rock fragmentation is more active on the outside the sedimentological and botanical study of fan deposits at the outlet of a karstic shaft in the tree shelter showed the local holocene environmental evolution three periods of different degree of aridity can be considered i before 8120 45 bp utc 5389 bedload aggradation points to rare but occasionally heavy rains lasting for several hours attaining intensities of more than 76 mm h and covering some 20 km2 wadi flash floods occasionally attained bankfull stage ii since 8120 45 bp utc 5389 such heavy rains have not occurred in the egyptian red sea mountains instead a more moderate but maybe wetter precipitation regime was established the karstic shafts were active and there was water and life in the desert two humid pulses can be distinguished within this period the first occurs at 8000 bp the second between 6630 45 grn 22560 and 6770 60 bp grn 22562 iii after the last wet culmination there was a gradual shift to drier conditions shortly after 5000 bp modern climatic conditions are believed to have been attained today the occasional rain storms are less heavy than before 8000 bp bankfull stage river floods do not occur instead secondary channels are eroded in the wadi beds the general arid character during the whole period and the inherent local and temporal variations in precipitation patterns might explain apparent aberrations between the palaeoenvironmental evolution of the tree shelter site and other remote study areas in egypt and sudan

nd sr isotopes and elemental geochemistry of surface sediments from the south china sea implications for provenance tracing abstract the mineralogy major and trace elements and neodymium and strontium isotopes of surface sediments in the south china sea scs are documented with the aim of investigating their applicability in provenance tracing the results indicate that mineralogical compositions alone do not clearly identify the sources for the bulk sediments in the scs the nd isotopic compositions of the scs sediments show a clear zonal distribution the most negative end values were obtained for sediments from offshore south china 13 0 to 10 7 while those from offshore indochina are slightly more positive 10 7 to 9 4 the nd isotopic compositions of the sediments from offshore borneo are even higher with end ranging from 8 8 to 7 0 and the sediments offshore from the southern philippine arc have the most positive end values from 3 7 to 5 3 this zonal distribution in end is in good agreement with the nd isotopic compositions of the sediments supplied by river systems that drain into the corresponding regions indicating that nd isotopic compositions are an adequate proxy for provenance tracing of scs sediments sr isotopic compositions in contrast can only be used to identify the sediments from offshore south china and offshore from the southern philippine arc as the 87sr 86sr ratios of sediments from other regions overlapped similar zonal distributions are also apparent in a la th sc discrimination diagram sediments from the west margin of the scs such as those from beibuwan bay offshore from hainan island offshore from indochina and from the sunda shelf plot in the same field while those offshore from the northeastern scs offshore from borneo and offshore from the southern philippine arc plot in distinct fields thus the la th sc discrimination diagram coupled with nd isotopes can be used to trace the provenance of scs sediments using this method we re assessed the provenance changes of sediments at ocean drilling program odp site 1148 since the late oligocene the results indicate that sediments deposited after 23 8 ma above 455 mcd meters composite depth were supplied mainly from the eastern south china block with a negligible contribution from the interior of the south china block sediments deposited before 26 ma beneath 477 mcd were supplied mainly from the north palawan continental terrane which may retain the geochemical characteristics of the materials covered on the late mesozoic granitoids along the coastal south china for that the north palawan continental terrane is presently located within the southern philippine arc but was located close to odp site 1148 in the late oligocene the weathering products of volcanic material associated with the extension of the scs ocean crust also contributed to these sediments the rapid change in sediment source at 26 23 8 ma probably resulted from a sudden cessation of sediment supply from the north palawan continental terrane we suggest that the north palawan continental terrane drifted southwards along with the extension of the scs ocean crust during that time and when the basin was large enough the supply of sediment from the south to odp site 1148 at the north slope may have ceased

sea level induced variations in clay mineral composition in the southwestern south china sea over the past 17 000 yr variations in clay mineral composition of sediment cores from the margin and continental slope of the sunda shelf southern south china sea se asia covering the past 17 000 yr reflect changing influences of sediment sources together with clay mineral partitioning processes in shallow waters we identify the deglacial sea level rise as the principal factor driving these changes during the late glacial high values of kaolinite are interpreted to reflect a higher contribution of clays from soils that have formed on the exposed sunda shelf and in the southern archipelagos of indonesia at this time core sites were located in close proximity to the mouths of the sunda shelf palaeo drainage systems on the emerged shelf sundaland the progressive landward displacement of the coastline and breakdown of these vast drainage systems during deglaciation led to a decrease in influence of the kaolinite rich southern sources when the coastline had retreated closely to its present day position in mid holocene times the former dominance of southern sources was replaced by a stronger influence of illite rich sources e g borneo the overriding control of sea level changes on the clay mineral distribution patterns precludes a definite climatic interpretation of clay mineral data in terms of climatic monsoonal changes in such highly dynamic sedimentary environment

source to sink transport processes of fluvial sediments in the south china sea the south china sea offers an excellent case for studying source to sink transport processes of fluvial sediments among the global marginal seas this study synthesizes existing clay mineralogical and geochemical data from similar to 1500 samples from the seafloor and surrounding rivers deepwater mooring observation results and high resolution glacial cyclic clay mineralogy records from six high quality sediment cores source to sink sediment transport from the river mouth to the continental shelf and then to the abyssal basin is investigated at two time scales modern process and late quaternary glacial cycles the results firstly show the high diversity of clay mineralogical and geochemical compositions in riverbed surface sediments surrounding the south china sea e g dominant illite and chlorite in taiwan overwhelming majority of smectite in luzon dominant kaolinite in south china and similar amounts of the four clay mineral species in red and mekong river systems the formation of these fluvial sediments through chemical weathering in surrounding drainage systems is controlled principally by the east asian monsoon climate with warm temperature and high precipitation and subordinately by tectonic activity and specific lithological character the basin wide distribution of clay mineral assemblages combined with neodymium and strontium isotopic compositions reflects strong provenance control and differential settling effects the differential settling of kaolinite in slightly saline and proximal regions relative to smectite in more saline and distal regions is well demonstrated in the south china sea through combining clay mineralogical distributions on the seafloor with observed oceanic current systems the modern transport pathways can be well established e g in the northern south china sea illite and chlorite from taiwan are mainly carried by contour currents with the strong influence of mesoscale eddies high resolution sediment dynamic analysis for the late quaternary reveals different sediment transport patterns in the northern western and southern south china sea when the land sea configuration dramatically changed during glacial conditions in the north the terrigenous dispersal is mainly controlled by provenance supply and oceanic current transport in the west the clay mineral assemblage reflects variations of the prevailing surface current influenced by monsoon winds in the south the clay mineral input indicates intensive chemical weathering during interglacial periods and strengthened physical erosion during glacial periods the transport of terrigenous sediments since the last glaciation is quantitatively reconstructed through studying two deepwater sediment cores located in the northern south china sea the relative contributions from three provenances south china luzon and taiwan highlight their distinct variability over the last 28 ka implying that the southward shift of the inter tropical convergence zone itcz at 16 ka bp caused an increased sediment contribution from south china the intensified influence of the kuroshio current intrusion controls more efficient westward transport of luzon sediments and the stronger deepwater current transports taiwan sourced sediments further westward from the last glaciation to the holocene c 2015 elsevier b v all rights reserved

integration of geological investigations with multi gis data layers for water resources assessment in arid regions el ambagi basin eastern desert egypt water resources assessment in arid lands is of a particular interest not only in scientific terms but also under the concept of sustainable development the study area el ambagi basin represents a remote arid area with a scarcity of data the measured effective porosity and permeability revealed high potentialities of the nubian sandstone and oligocene sediments the hydrogeologic setting indicates favorable conditions for groundwater accumulation where there is an opportunity of recharge and thus the sustainability of the groundwater the research approach is based on geological investigations as well as several data layers in the gis environment including landforms lithology slope soil morphometric parameters structural lineaments and geophysical data several specific sites were suggested as targets for future groundwater explorations the studied basin contains four sub basins which have an intensive drainage network the morphometric parameters revealed that they have potential for surface runoff occurrence and also for groundwater recharge two of the investigated sub basins show high hazard degrees and should be protected to avoid flash floods the estimated runoff volume from a single rainfall event 27 mm can reach 3316 42 103 m3 hence management of rainwater harvesting and protection measures against flash floods are necessary a future water resources management strategy based on results of the multidisciplinary study is proposed

development of the east asian summer monsoon evidence from the sediment record in the south china sea since 8 5 ma 128 samples from ocean drilling program odp site 1143 in the southern south china sea were analyzed for grain size clay minerals biogenic opal content and quartz in order to reconstruct changes in east asian monsoon climate since 8 5 ma an abrupt change of terrigenous mass accumulation rate mar clay mineral assemblage median grain size and biogenic opal mar about 5 2 ma suggests that between 8 5 5 2 ma the source of terrigenous sediment was mainly in the region of surface uplift and basaltic volcanism in southern vietnam a simple model of east asian summer monsoon evolution was based on the clay feldspar ratio kaolinite chlorite ratio and biogenic opal mar the summer monsoon has two periods of maximum strength at 8 5 7 6 ma and 7 1 6 2 ma subsequently there was a relatively stable period at 6 2 3 5 ma continued intensification about 3 5 2 5 ma and gradually weakening after 2 5 ma since i ma the monsoon has intensified with remarkable high frequency and amplitude variability simultaneous increase in sedimentation rates at odp sites 1143 1146 and 1148 as well as in mar of terrigenous materials quartz feldspar and clay minerals at odp site 1143 at 3 5 2 5 ma may be the erosional response to both global climatic deterioration and the strengthening of the east asian summer monsoon after about 3 4 ma c 2006 elsevier b v all rights reserved

timing and characteristics of late pleistocene and holocene wetter periods in the eastern desert and sinai of egypt based on 14c dating and stable isotope analysis of spring tufa deposits abstract there is very little dated evidence on wet periods in the eastern desert and sinai peninsula of egypt during the late pleistocene and holocene to obtain such information we have studied the petrography isotope geochemistry and ams radiocarbon ages of mostly relict tufas deposited by springs draining perched ground water bodies in metamorphic and volcanic rocks the tufas unconformably overly precambrian basic igneous rocks basalt diabase and gabbro as the ages of tufa carbonate are frequently older than the true ages of the deposits because of the incorporation of old 14c dead carbon we have dated both the carbonate matrix and insoluble organic material of the tufas these ages show that the tufas were largely formed during two broad time periods the most recent from 12 058 to 6678 cal yr bp african humid period and the other from 31 200 22 500 cal yr bp with preferential growth during the coldest times of this period namely during heinrich events 2 and 3 h2 and h3 and the last glacial maximum lgm the time span between 19 000 9000 cal yr bp including the yd and h1 appears to have been relatively more arid than the earlier lgm or h2 periods or the later holocene the late pleistocene tufas are depleted in 18o relative to the holocene tufas and were deposited at a lower temperature 14 0 20 8 c vs 18 4 23 4 c we believe that the holocene tufas in the sinai were formed by rainfall from the mediterranean and those in the southern part of the eastern desert by african monsoon rainfall derived from the red sea gulf of aden and indian ocean in contrast the moisture that fed the late pleistocene tufas which are depleted in 18o relative to holocene deposits and progressively depleted from north to south was probably brought by the westerlies from the atlantic mediterranean sea when the westerly circulation was pushed southwards during the coldest periods of the late pleistocene periods of tufa deposition correlate with major documented paleoclimatic events in north africa during the late pleistocene and holocene such as the nile floods high sea level and the formation of sapropels in the mediterranean

uranium isotopic study of artesian and pluvial contributions to the nubian aquifer western desert egypt the groundwater systems of the nubian aquifer beneath six major oases baris kharga dakhla farafra bahariya and siwa in the western desert of egypt have been studied to establish their sources and mixing volumes using uranium isotopes one hundred six groundwater samples from different depths of the nubian aquifer have been analyzed for uranium content and 234u 238u activity ratio ar the aquifer under the western desert is known to have more than one source of water at bahariya and farafra oases the nubian artesian water migrating from the south has been augmented by local recharge during pluvial times at siwa oasis in the northwestern desert a shallower aquifer component migrating from the north or west is also present at dakhla kharga and baris oases in the southwestern desert the main source is the nubian artesian water migrating from southeast uweinat upland and northwest sudan these water masses have distinctive uranium isotopic signatures the nubian aquifer water is characterized by very low u concentrations 1 5 the shallow northwest aquifer water also has a high ar but a much higher u concentration the locally recharged pluvial waters have high u concentrations 0 1 ppb but low ars near unity a diagnostic derivative parameter is excess 234u content the deep nubian aquifer water is characterized by a relatively low excess 234u 0 02 ppb equivalent while the shallow siwa water has a very high excess 234u ar 1 u conc the bahariya and farafara waters are also high in this component probably because of pluvial water percolation through phosphate rich strata at all oases u isotopic mixing diagrams show that the deep aquifer sources predominate however the pluvial contributions are significant ranging from about 5 at remote baris oasis to about 26 at the more northerly farafra oasis the observed lowering of potentiometric surfaces in the western desert is caused not only by pumping at a rate greater than inflow from the aquifer systems but also by the withdrawal of pluvial water which in modern times is not being replaced at all

multi emission luminescence dating of heated chert from the middle stone age sequence at sodmein cave red sea mountains egypt sodmein cave in egypt is one of the rare archaeological sites in north eastern africa conserving human occupation remains of a period most relevant for the out of africa ii hypothesis this underlines the need for establishing a chronological framework for the more than 4 m of stratified sediments ranging from the middle stone age msa to the neolithic the lowest layer j hosts huge fireplaces from which we report luminescence ages of heated chert fragments unearthed from different depths the multi emission dating approach using both the blue and red tl of each specimen as well as the osl emission of one sample allowed identifying the most reliable ages samples yield ages between 121 15 ka maximum age and 87 9 ka these data evidence human presence at the site during mis 5 for integrating sodmein cave into the actual discussion of the dispersal patterns of modern humans and to identify potential connections with other sites in the nile valley and in the middle east a sound and reliable chronology is indispensable

influence of the kuroshio current intrusion on depositional environment in the northern south china sea evidence from surface sediment records the influence of the kuroshio current kc intrusion on the depositional environment of the northern south china sea scs is discussed based on multi proxies of surface sediments including planktonic foraminifera clay minerals and geochemical elements the results reveal that four typical planktonic foraminifera globigerinoides ruber g sacculifer neogloboquadrina dutertrei and pulleniatina obliquiloculata can be used to trace the kc flow route in the northern scs globigerinoides ruber is mainly distributed in shallower water than the south china sea branch of the kuroshio scsbk flow route while p obliquiloculata is mostly distributed in deeper water than the scsbk flow route there are high percentages of g sacculifer and n dutertrei at the scsbk flow route along the 1000 m isobath where bottom sediments consist of clayey silt and silty clay the scsbk also affects sediment distribution of various sources taiwan sourced sediments characterized by high illite and chlorite contents are transported southwestward into the deep sea environment by the scsbk and or deep water current the pearl river sediments characterized by high kaolinite and titanium ti contents are mostly transported southwestward to be distributed in the sea environment between the pearl river mouth and southeast of hainan island but hardly entered the abyssal basin the luzon island sediments characterized by high smectite content are generally deposited at the northwest of luzon island under the effect of an eddy west of luzon island these sediments were hardly transported northwestward onto the northern shelf of the scs throughout the scsbk flow route the sedimentary environment at the northwest of luzon island is relatively oxidized and higher in salinity than the northern scs which is probably connected with the kc intrusion through the luzon strait

relations among hydrocarbon reservoirs epigenetic sulfidization and rock magnetization examples from the south texas coastal plain this paper focuses on the association between concentrations of iron disulfide fes2 minerals in the shallow subsurface and underlying hydrocarbon accumulations such fes2 concentrations are the result of migration of either h2s or organic constituents from the underlying hydrocarbons the h2s from reservoirs is produced inorganically from sulfate in the reservoir rocks at high temperature 90 c and migrates to shallower beds to react inorganically with iron to form fes2 organic constituents from reservoirs in contrast provide nourishment for sulfate reducing bacteria in shallow relatively cool 90 c beds sandstone in the ray point uranium district in live oak county texas contains abundant fes2 which formed both from deep seated h2s and from h2s produced in the shallow subsurface by bacteria that utilized organic materials from depth deep petroleum reservoirs were physically connected to near surface 100 m beds containing epigenetic fes2 by the oakville fault epigenetic iron sulfide format

aridity and humidity two aspects of the late miocene climate of north africa and the mediterranean abstract the physiography of north africa is not greatly changed from that of the messinian with the drawdown of the mediterranean in the late messinian the then existing river systems were incised into the landscape and emptied into lake cyrenaica which occupied the substantially drained eastern mediterranean basin the record of incision provides a record of the magnitude of the messinian river systems an analysis of these river systems demonstrates that messinian rainfall a consequence of the zeit wet phase was greatest in east and south central north africa in keeping with the derivation of the water mainly from the indian ocean in central north africa the eosahabi river flowed from messinian lake chad eroding the east tibesti valley and cutting a channel which is especially well preserved near the coast of the gulf of sirt the penetrated sediments of lake cyrenaica and the marginal basins of the messinian transgression are known as the upper evaporites and are generally fine clastics gypsarenites and gypsum anhydrite they were rapidly deposited underlying them is the halite of the lower evaporites this sequence of upper and lower evaporites is much like the lower halite of the tortonian south gharib formation and the overlying clastics and anhydrite of the messinian zeit formation in the gulf of suez red sea area this type of sequence is termed an evaporitic couplet and as has been demonstrated for the gulf of suez red sea is a consequence of a transition from a dry to a more humid climate in a restricted or semirestricted basin this transition occurred at about 7 5 ma in the gulf of suez red sea and at about 5 8 ma in the mediterranean the zeit wet phase manifest in the above events developed in association with the initiation and development of the asian monsoon and the drying of the mediterranean it can be understood in terms of the development of an evolving monsoon desert system the asian monsoon was initiated 8 7 ma in association with the uplift of tibet at this time the north african desert zone was displaced northwards to be over the mediterranean and central and eastern north africa became seasonally humid a concept is advanced in which the early stage of the development of the asian monsoon is seen as having two phases alternating at the precessional ca 21 ka cycle one phase transferred moisture from the indian ocean mainly to southern asia the other phase transferred moisture mainly to north africa with the drawdown of the mediterranean at about 5 8 ma the zeit wet phase intensified a further northward movement of the humid and desert zones occurred at the time of drawdown with the messinian and early pliocene transgressions the wet phase ameliorated but a substantial river system still crossed central north africa at about 4 6 ma north africa became drier probably in response to the developing dominance of the features of the monsoon that transferred moisture mainly to southern asia features of the monsoon that are well recognised today

combination of remote sensing gis and palaeohydrologic remarks for promoting the exploitation of water resources in the sahara cases from the red sea coast egypt the current work presents an integrated approach to maximize groundwater exploitation under sahara conditions the approach includes investigation of palaeohydrology remote sensing data field verification and geophysical datasets gravity aeromagnetic and geoloelectrical data results reveal the existence of palaeohydrologic remarks such as palaeodriange terraces tufas gorges and alluvial fans the hydrogeological investigation reflects that the quaternary groundwater existed under free water table conditions with water depths range between 5 06 and 50 m from the ground while the miocene aquifer has water depths vary between 22 m of shallow wells and 108 m of deep wells the study illustrates the presence of the tectonic fallen zones tfz where the precambrian rocks show throw down blocks associated with a set of faults and covered by thick sedimentary succession the tfz with their faults nw se and ne sw are attributed to the regional red sea rift where these faults can provide groundwater recharge opportunities the groundwater occurrences in the tfz indicate saturation thickness ranges between 75 and 175 m for miocene aquifer and between 50 and 180 m for nubian sandstone aquifer a total of 22 basins were analyzed where their morphometric parameters indicate the possibility of groundwater accumulations the obtained stable isotopes compositions of hydrogen d and oxygen 18o reveal that aquifers were recharged throughout the previous wetter climate with reasonable contributions during intervening arid periods due to the continued and urgent need for water in the sahara the obtained results can be utilized to develop applied recommendations for future groundwater exploration

clay mineralogy of the riverine sediments of hainan island south china sea implications for weathering and provenance abstract clay mineralogy of 54 fluvial samples collected from 20 major rivers on hainan island are investigated in order to determine compositional changes of clay minerals and to assess the weathering processes the clay mineral assemblages consist dominantly of kaolinite 31 66 with a lesser abundance of chlorite 22 44 and illite 4 33 and a trace amount of smectite 0 15 fluvial sediments from the east and northwest of hainan island are characterized by a higher kaolinite content and illite chemical index and poorer illite crystallinity than those from southwest hainan only minor smectite mean of 7 occurs in the sediments from west hainan smectite is total lacking in east hainan compared with the adjacent basins hainan island is characterized by moderate to intensive chemical weathering with strong hydrolysis our results suggest that rainfall is the principal factor controlling the intensity of chemical weathering on hainan island with more intense chemical weathering occurring in eastern and northwestern hainan another practical implication of this study is that it provides a missing end member hainan island in the provenance discrimination study focused on the northern south china sea scs hainan fine grained sediments likely play an important role in providing clay minerals to the northern scs carried by the south china sea warm current scswc during the summer

holocene environment and subsistence patterns near the tree shelter red sea mountains egypt abstract the tree shelter site dates to the early to mid holocene 8000 to 4900 14c yr bp present conditions around the site are hyperarid but charcoal remains indicate less severe aridity at the time of its occupation the environment around the site then supported a rich wadi vegetation which allowed hunting during the epipaleolithic and herding during the neolithic occupation although more favorable than today the environmental conditions also displayed a desert character and seem to have limited the range of domestic herbivores introduced in the area

deepwater overflow through luzon strait 1 this study examines water property distributions in the deep south china sea and adjoining pacific ocean using all available hydrographic data our analysis reveals that below about 1500 m there is a persistent baroclinic pressure gradient driving flow from the pacific into the south china sea through luzon strait applying hydraulic theory with assumptions of zero potential vorticity and flat bottom to the luzon strait yields a transport estimate of 2 5 sv 1 sv 106 m3 s 1 some implications of this result include 1 a residence time of less than 30 years in the deep south china sea 2 a mean diapycnal diffusivity as large as 10 3 m2 s 1 and 3 an abyssal upwelling rate of about 3 10 6 m s 1 these quantities are consistent with residence times based on oxygen consumption rates the fact that all of the inflowing water must warm up before leaving the basin implies that this marginal sea contributes to the water mass transformations that drive the meridional overturning circulation in the north pacific density distributions within the south china sea basin suggest a cyclonic deep boundary current system as might be expected for an overflow driven abyssal circulation

late quaternary paleoceanography of the south china sea glacial interglacial contrasts in an enclosed basin the sea surface paleotemperature of the south china sea scs is estimated quantitatively based on the quantitative analysis of planktonic foraminiferal faunas recovered from piston cores v36 06 3 v36 06 5 and so49 kl8 on the northern continental slope the results lead to a reconstruction of the history of paleocirculation patterns during the last 200 000 years the postglacial and interglacial transbasinal circulation pattern was replaced by a semienclosed basin flow pattern during glacial episodes lowered sea level transformed the scs into a semienclosed basin with the only passageway to the open ocean in its northeastern corner the east asian monsoon which governs circulation patterns in the scs both today and during the late quaternary created both clockwise summer and counterclockwise winter surface gyres during glacials the inflow of tropical surface water masses from both the pacific and indian oceans decreased or was completely cut off from this marginal sea causing a greater decrease in glacial sea surface temperature than in the open ocean of the same latitude inferred increased influence of pacific temperate waters and decreased influence of tropical subtropical waters are confirmed by changes in the planktonic foraminiferal assemblages glacial interglacial fluctuation in sea surface temperature sst 6 8 9 3 c for winter and 2 3 c for summer as well as the seasonality 4 6 c for postglacial and interglacials and 9 10 c for glacials are much greater than the adjacent open western pacific reflecting the amplification of the climatic signal in the marginal sea

evolution and variability of the east asian summer monsoon during the pliocene evidence from clay mineral records of the south china sea the late pliocene is thought to be characterized by the simultaneous intensification of both the east asian winter monsoon eawm and east asian summer monsoon easm however the evolution of the easm during the pliocene remains still controversial and only little is known about the dynamics of the easm during the pliocene on orbital time scales here we use clay mineral assemblages in sediments from ocean drilling program odp site 1143 in the southern south china sea scs to obtain proxy records of past changes in the easm climate during the pliocene provenance analysis suggests that illite chlorite and kaolinite originated mainly from the mekong river drainage area smectite was derived mainly from the indonesian islands the kaolinite illite ratio and the chemical index of alteration cia of siliciclastic sediments allowed us to reconstruct the history of chemical weathering and physical erosion of the mekong river drainage area and thus the evolution of the easm during the pliocene our clay minerals proxy data suggests a stronger easm during the early pliocene than during the late pliocene we propose that the long term evolution of the easm has been driven by global cooling rather than the uplift of the tibetan plateau spectral analysis of kaolinite illite ratio displays a set of strong periodicities at 100 ka 30 ka 28 ka 25 ka and 22 ka with no clear obliquityrelated signal our study suggests that the pliocene easm intensity on orbital time scales is not only controlled by the northern hemisphere summer insolation but also strongly influenced by equatorial pacific enso like ocean atmosphere dynamics c 2010 elsevier b v all rights reserved

uranium lead isochron age and preliminary sulfur isotope systematics of the felder uranium deposit south texas uranium lead isotope systematics of roll front ores in miocene sandstone at the felder and mclean uranium deposits south texas coastal plain give a well defined 207 pb 204 pb 235 u 204 pb isochron age of 5 07 or 0 15 m y the relatively slight degree of scatter of the points defining the isochron is probably due to initial pb isotope inhomogeneity and the resulting inferred persistence of closed system behavior for u and pb is probably the result of the long term presence of u and pb immobilizing h 2 s 206 pb 238 u systematics are badly scattered owing to long term migration of radioactive daughters of 238 u beta and gamma activity systematics of the ores consistently identify those with grossly anomalous pb isotope systematics however and proved highly useful in identifying ores that have gained gross amounts of uranium daughters fes 2 minerals in the altered tongue of the host sandstone are characterized by abundant postore pyrite and heavy delta 34 s values whereas fes 2 minerals in mineralized and unaltered barren rock are characterized by abundant ore stage marcasite and by light delta 34 s values the delta 34 s values of fes 2 minerals in the altered tongue are similar to those defined for sour gas from the underlying edwards limestone of cretaceous age indicating the probable source for the sulfur of an inferred resulfidization event the 5 07 m y isochron age probably reflects the end of roll front development we believe that the end was due to the resulfidization and does not preclude significant earlier periods of mineralization modern ground water in the area is also sulfide bearing thus helping preserve the deposit but with delta 34 s values distinct from those of sulfides in the resulfidized zone of the host rock

samarium neodymium elemental and isotopic systematics in sedimentary rocks abstract trace element sm nd th sc and nd isotopic data for sedimentary rocks are examined in order to evaluate 1 1 possible secular trends in the composition of the sedimentary mass and upper continental crust 2 2 the role of tectonic setting in controlling the chemical and nd isotopic composition of the sedimentary mass when plotted against either sedimentation age or average provenance age determined mainly from nd model ages sm nd in sedimentary rocks decreases abruptly from about 0 21 to 0 19 at the archean proterozoic transition consistent with a change towards a more felsic upper crustal composition the change is only somewhat less pronounced for turbidite sediments than for those of continental affinity a trend toward increasing sm nd approaching or exceeding archean values is observed for phanerozoic turbidites this latter change is interpreted as indicating undifferentiated young crust as a component in the sediment which has been lost from the older post archean record due to sedimentary and igneous intracrustal recycling processes when plotted against sedimentation age th sc ratios exhibit a trend directly comparable to that of sm nd in this case th sc increases abruptly at the archean proterozoic boundary from about 0 5 to 1 0 and then decreases to about 0 7 during the phanerozoic nd isotopic composition of modern sediments is affected by tectonic association with those deposited at active margin settings tending to have higher nd reflecting younger provenance and higher and more scattered sm nd reflecting less homogenized and differentiated provenance it is likely that these distinctions can be traced back for about 1 2 ga but with the current data base are not readily resolved in older sedimentary rocks the degree to which the preserved sedimentary mass is open to new additions from the mantle either through replacement during sedimentary recycling or sediment mass growth is highly variable but averages about 15 25 during the phanerozoic

red sea rifting controls on aquifer distribution constraints from geochemical geophysical and remote sensing data highly productive wells in the central eastern desert of egypt are tapping groundwater in subsided blocks of jurassic to cretaceous sandstone taref formation of the nubian sandstone group and oligocene to miocene sandstone nakheil formation now occurring beneath the red sea coastal plain and within the proximal basement complex aquifer development is related to red sea rifting 1 rifting was accommodated by vertical extensional displacement on preexisting nw se to n s trending faults forming a complex array of half grabens and asymmetric horsts and 2 subsided blocks escaped erosion accompanying the red sea related uplift subsided blocks were identifi ed and verifi ed using satellite data geologic maps and fi eld and geophysical investigations interpretations of very low frequency vlf measurements suggest the faults acted as conduits for ascending groundwater from the subsided aquifers stable isotopic compositions d 19 3 to 53 9 18 o 2 7 to 7 1 of groundwater samples from these aquifers are interpreted as mixtures of fossil up to 70 and modern up to 65 precipitation groundwater volumes in subsided blocks are large within the central eastern desert basement complex alone they are estimated at 3 10 9 m 3 and 10 10 9 m 3 for the

extensional fault related folding northwestern red sea egypt the duwi and hamadat areas on the northwestern margin of the red sea rift system exhibit superb outcrop examples of kilometric scale extensional fault related folds in this area the nakheil and hamadat faults of the rift border fault system consist of a series of wnw and nw trending segments that link through breached relay ramps the fault hanging walls are characterised by a series of offset synclines with non linear axial traces sub parallel to the faults the synclines are doubly plunging and in the immediate hanging wall to the normal faults the strata dip sub parallel to the fault these folds result from along strike displacement variations on the individual fault segments together with extension related fault propagation folding as the faults propagated upwards through a highly anisotropic pre rift sedimentary section in the duwi area the axial traces of the synclines are offset and bend in the regions of relay ramps in the hamadat area the synclines associated with individual fault segments are separated by transverse hanging wall anticlines that formed where segment linkage occurred numerical simulations of extension related fault propagation folding using a trishear model produce geometries that closely match those of the duwi and hamadat folds the dimensions of these hanging wall synclines and their relationships to fault displacement variations indicate that they are formed by extensional fault propagation folding rather than by frictional drag along the fault surface

investigating the history of east asian monsoon and climate during the last glacial interglacial period 0 140 000 years mineralogy and geochemistry of odp sites 1143 and 1144 south china sea abstract monsoon climate is an important component of the global climatic system a comprehensive understanding of its variability over glacial interglacial time scales as well as of its effects on the continent and in the ocean is required to decipher links between climate continental weathering and productivity a detailed multiproxy study including bulk and clay mineralogy grain size analysis phosphorus geochemistry sedex extraction organic matter characterization and nitrogen stable isotopes was carried out on samples from odp sites 1143 and 1144 leg 184 south china sea covering the past 140 000 years we tentatively reconstruct the complex sedimentation and climatic history of the region during the last glacial interglacial cycle when sea level variations linked to the growth and melting of ice caps interact with monsoon variability during interglacial periods of high sea level summer monsoon was strong and humid and warm climate characterized the adjacent continent and islands clay minerals bear signals of chemical weathering during these intervals high calcite and reactive phosphorus mass accumulation rates mars indicate high productivity especially in the southern region of the basin during glacial intervals strong winter monsoon provided enhanced detrital input from the continent as indicated by high detrital mar glacial low sea level resulted in erosion of sediments from the exposed sunda shelf to the south and clay mineral variations indicate that warm and humid conditions still prevailed in the southern tropical areas enhanced supply of nutrients from the continent both by river and eolian input maintained high primary productivity reduced circulation during these periods possibly induced active remobilization of nutrients such as phosphorus from the sediments intense and short cold periods recorded during glacial and interglacial stages correlate with loess records in china and marine climatic records in the north atlantic confirming a teleconnection between low and high latitude climate variability

climatic and tectonic controls on weathering in south china and indochina peninsula clay mineralogical and geochemical investigations from the pearl red and mekong drainage basins 1 results of clay mineralogy major element geochemistry and sr and nd isotopes in 93 argillaceous samples collected from drainage basins of the pearl red and mekong rivers reveal different degrees of chemical weathering in southeast asia despite similar climate conditions across these regions the kaolinite illite ratio illite chemistry index and illite crystallinity can be used as indicators of chemical weathering intensity these mineralogical proxies combined with the k2o na2o cao molar ratio chemical index of alteration cia and weathering trends observed from major element results indicate intensive silicate weathering in the pearl river basin moderate to intensive in the mekong river basin and moderate in the red river basin although a significant modification of epsilon nd 0 values in our riverine sediments during chemical weathering and transport is unlikely sr 87 sr 86 ratios are controlled by various states of chemical weathering of high sr minerals such as plagioclase rich in na and ca with a linear decrease trend from the pearl mekong to red river basins our results suggest that it is not the warm climate with heavy monsoon precipitation but tectonics playing the most significant role in controlling weathering and erosion processes in south china and indochina peninsula strong physical erosion caused by tectonic activities and river incision along the eastern margin of the tibetan plateau and along the red river fault system is responsible for high contents of primary minerals in the lowlands of red and mekong river basins

on the significance of sea level variations and shelf paleo morphology in governing sedimentation in the southern south china sea during the last deglaciation abstract deglacial sedimentation on the outer sunda shelf the shelf margin and slope shows a close correlation with the stages of flooding of the emerged shelf it is mainly controlled by the relationship between shelf paleo physiography and changes in sea level and sediment supply based on the sedimentological and geochemical variability at five sites along a transect across the outer shelf and the continental slope covering the last 20 000 years four intervals of significant depositional changes are identified the first reorganization in the sedimentation regime which was established during sea level lowstand is associated with the drowning of the lower course of the north sunda river between 16 5 and 14 5 ka during and following the rapid rise in sea level at 14 5 14 ka sedimentation on the slope is characterized by an accelerated decrease in the supply of terrigenous material associated with the flooding of the middle part of the paleo valley this abrupt change in sedimentation is followed by a period of gradual decrease of terrigenous supply to the slope when the surrounding plains of the river valley were flooded 14 8 5 ka the final change occurred between ca 8 5 and 6 ka when the coastline reached its modern position and modern sedimentary patterns are established this change probably marks the end of reworking by transgression given the synchroneity of sedimentological changes along the transect across the sunda shelf and into the deep sea with the environmental shifts on the central shelf sedimentation on the margin and slope appears to be mainly controlled by the interrelationship of sea level shelf paleo physiography and sediment supply moreover the records display lateral changes through time associated with stages of the deglacial transgression which mask any potential sedimentological variability due to changes in precipitation vegetation or atmospheric circulation this fact cautions the interpretation of near shore sedimentary records as unequivocal recorders of local climate change e g se asian monsoon and highlights the need to include variations in shelf physiography and sea level in future paleoceanographic studies

large scale drainage capture and surface uplift in eastern tibet sw china before 24 ma inferred from sediments of the hanoi basin vietnam current models of drainage evolution suggest that the non dendritic patterns seen in rivers in se asia reflect progressive capture of headwaters away from the red river during and as a result of surface uplift of eastern asia mass balancing of eroded and deposited rock volumes demonstrates that the red river catchment must have been much larger in the past in addition the nd isotope composition of sediments from the hanoi basin vietnam interpreted as paleo red river sediments shows rapid change during the oligocene before similar to 24 ma we interpret this change to reflect large scale drainage capture away from the red river possibly involving loss of the middle yangtze river reorganization was triggered by regional tilting of the region towards the east this study constrains initial surface uplift in eastern tibet and southwestern china to be no later than 24 ma well before major surface uplift and gorge incision after 13 ma

late quaternary paleoceanography of the south china sea surface circulation and carbonate cycles paleoceanographic information from 34 sediment cores is summarized to investigate the glacial interglacial variations in sea surface circulation and late quaternary carbonate cycles in the south china sea judging from the distribution pattern of deposition rates the enormous terrigenous supply by rivers is responsible for the high rate of hemipelagic sedimentation which was even higher during glacial periods paleotemperature maps based on transfer function temperature estimates have revealed a e w gradient of sst for glacial summer and a s n gradient for glacial winter and this agrees well with the clockwise surface circulation in summer and counterclockwise in winter during glacials as shown by a preliminary computer modelling the high resolution paleotemperature curves of core v36 3 from the northern slope show an abrupt cooling event which may belong to the younger dryas carbonate percentage in sediments and preservation of foraminifers and pteropods are used to study the carbonate cycles in the marginal sea it turns out that two mechanisms are functioning there being a basin with large drainage areas vast amount of river borne terrigenous input dilutes carbonate and its intensification during glacial decreases the glacial cac03 being a basin connected with the pacific the fluctuations of lysocline ccd and acd in the scs are related to those in the pacific ocean and dissolution is strengthened at interglacial thus above the present ccd the dilution factor predominates and the atlantic cycles are produced below the present ccd the dissolution factor prevails resulting in the pacific pattern of carbonate cycles

genetic and grade and tonnage models for sandstone hosted roll type uranium deposits texas coastal plain usa abstract the coincidence of a number of geologic and climatic factors combined to create conditions favorable for the development of mineable concentrations of uranium hosted by eocene through pliocene sandstones in the texas coastal plain here 254 uranium occurrences including 169 deposits 73 prospects 6 showings and 4 anomalies have been identified about 80 million pounds of u 3 o 8 have been produced and about 60 million pounds of identified producible u 3 o 8 remain in place the development of economic roll type uranium deposits requires a source large scale transport of uranium in groundwater and deposition in reducing zones within a sedimentary sequence the weight of the evidence supports a source from thick sequences of volcanic ash and volcaniclastic sediment derived mostly from the trans pecos volcanic field and sierra madre occidental that lie west of the region the thickest accumulations of source material were deposited and preserved south and west of the san marcos arch in the catahoula formation by the early oligocene a formerly uniformly subtropical climate along the gulf coast transitioned to a zoned climate in which the southwestern portion of texas coastal plain was dry and the eastern portion humid the more arid climate in the southwestern area supported weathering of volcanic ash source rocks during pedogenesis and early diagenesis concentration of uranium in groundwater and movement through host sediments during the middle tertiary era abundant clastic sediments were deposited in thick sequences by bed load dominated fluvial systems in long lived channel complexes that provided transmissive conduits favoring transport of uranium rich groundwater groundwater transported uranium through permeable sandstones that were hydrologically connected with source rocks commonly across formation boundaries driven by isostatic loading and eustatic sea level changes uranium roll fronts formed as a result of the interaction of uranium rich groundwater with either 1 organic rich debris adjacent to large long lived fluvial channels and barrier bar sequences or 2 extrinsic reductants entrained in formation water or discrete gas that migrated into host units via faults and along the flanks of salt domes and shale diapirs the southwestern portion of the region the rio grande embayment contains all the necessary factors required for roll type uranium deposits however the eastern portion of the region the houston embayment is challenged by a humid environment and a lack of source rock and transmissive units which may combine to preclude the deposition of economic deposits a grade and tonnage model for the texas coastal plain shows that the texas deposits represent a lower tonnage subset of roll type deposits that occur around the world and required aggregation of production centers into deposits based on geologic interpretation for the purpose of conducting a quantitative mineral resource assessment

clay mineral distribution in surface sediments of the northeastern south china sea and surrounding fluvial drainage basins source and transport clay mineralogy of surface samples throughout the northeastern south china sea scs and surrounding fluvial drainage basins has been investigated to reveal source and transport of detrital fine grained sediments three characteristic end members in clay mineral compositions were observed from three major provenances respectively major kaolinite and moderate illite and chlorite from the pearl river predominant illite and chlorite from taiwan and principal smectite from the luzon arc system the transport of four clay mineral species in the northeastern scs is influenced by various mechanisms smectite derived from the luzon arc system is transported mainly by surface current with significant influence of the kuroshio intrusion illite and chlorite from taiwan are mainly carried by deep water current while kaolinite from the pearl river is affected obviously by the westward guangdong coastal current and longshore current a westerly tongue shaped distribution of high contents of illite and chlorite mainly from taiwan on the eastern shelf may result from the westward guangdong coastal current during the winter the results suggest that clay mineral assemblages in the northeastern scs are mainly controlled by provenance supply and current transport and their downcore records do not bear contemporaneous paleoclimatic features the implication of clay minerals for proxies of the late quaternary east asian monsoon evolution is realized through both the provenance supply and current transport processes c 2010 elsevier b v all rights reserved

increasing australian indonesian monsoon rainfall linked to early holocene sea level rise the australian indonesian summer monsoon affects rainfall variability across the indo pacific region reconstructions of monsoon strength from stalagmites show that precipitation increased from 11 000 to 7 000 years ago as rising global sea level caused the flooding of the indonesian continental shelf the australian indonesian summer monsoon affects rainfall variability and hence terrestrial productivity in the densely populated tropical indo pacific region it has been proposed that the main control of summer monsoon precipitation on millennial timescales is local insolation1 2 3 but unravelling the mechanisms that have influenced monsoon variability and teleconnections has proven difficult owing to the lack of high resolution records of past monsoon behaviour here we present a precisely dated reconstruction of monsoon rainfall over the past 12 000 years based on oxygen isotope measurements from two stalagmites collected in southeast indonesia we show that the summer monsoon precipitation increased during the younger dryas cooling event when atlantic meridional overturning circulation was relatively weak4 monsoon precipitation intensified even more rapidly from 11 000 to 7 000 years ago when the indonesian continental shelf was flooded by global sea level rise5 6 7 we suggest that the intensification during the younger dryas cooling was caused by enhanced winter monsoon outflow from asia and a related southward migration of the intertropical convergence zone8 however the early holocene intensification of monsoon precipitation was driven by sea level rise which increased the supply of moisture to the indonesian archipelago

analysis and quantification of groundwater recession characteristics in regolith bedrock aquifers a case study in the mid and upper choshuei river basin in central taiwan investigating the groundwater recession characteristics and its relation with geological conditions is of critical importance to the estimation of groundwater recharge in regolith bedrock aquifers which commonly occur in the mountainous areas of taiwan this paper examines the role of geological and hydrogeological factors in controlling rainfall induced recharge processes groundwater and rainfall data were compiled from 29 monitoring wells and rainfall stations situated in the mid and upper choshuei river basin in central taiwan in light of analyzing the outcome of the groundwater level response to rainfall the relation between the effective rainfall and groundwater level fluctuation tends to be positive and rainfall events with high intensity firmly control the groundwater recharge process in taiwan mountainous areas permeable geological units likely dominate the groundwater level variations besides recession rates in the vertical direction varying with geological conditions were obviously found in each well site to improve the efficiency of the water table fluctuation wtf method on extrapolating recession rates two rating systems for evaluating hydraulic properties of regolith and fractured bedrock respectively were proposed and applied to develop the effective techniques linked to the quantification of recession characteristics varying with depths for each well by regression analysis the dependence of the hydraulic property rating system on the recession rate was performed and the derived regression equation for each well can be used to estimate the recession rate with depths finally the recharge estimation with the above techniques in taiwan mountainous areas was established and the present method of estimating recharge was compared with the existing method the difference between the two methods was obviously found thus recharge estimation in mountainous areas should take account of complex geological conditions

holocene evolution of the song hong red river delta system northern vietnam abstract the song hong red river delta located on the western coast of the gulf of bac bo tonkin in the south china sea formed as a result of the song hong sediment discharge throughout the holocene the river s sedimentary basin upstream from the delta plain is not large the delta plain comprises emerged tidal mangrove flats formed during the sea level highstand at 2 3 m 6 4 cal kyr bp and a beach ridge strandplain with straight to lobate beach ridges on the landward and seaward sides of the delta plain respectively the delta affords us the opportunity to examine river mouth morphodynamics comprehensively in relation to sediment discharge and sea level changes in this paper we describe the holocene evolution of the song hong delta system and the river mouth morphodynamics on the basis of seven sediment cores each 30 70 m long taken from the delta plain during 1999 2001 and 101 radiocarbon dates obtained from the core sediments sediments from the seven cores consisting of incised valley fills since the last glacial maximum can be divided in ascending order into fluvial sediments composed of gravelly sand and mottled clay tide influenced estuarine sediments containing shell and wood fragments and deltaic sediments composed of tide influenced sand and mud deposits in which the contents of sand and wood fragments increase upward by applying sequence stratigraphic concepts a transgressive surface can be identified at the gravelly sand mottled clay boundary and the maximum flooding surface can be identified at the estuarine deltaic sediments boundary the lowstand systems tract transgressive systems tract and highstand systems tract record 15 15 9 and 9 0 cal kyr bp respectively during the past 9 kyr the majority of the sediment discharged by the song hong accumulated in the incised valley and enhanced progradation at the river mouth the river mouth prograded from the bay head toward the gulf and its morphology changed from funnel shaped 9 6 cal kyr bp to straight 6 2 cal kyr bp and finally to lobate 2 0 cal kyr bp the morphological change from a funnel shaped to straight coast is interpreted to have been closely related to a hydrologic regime shift from a tide dominated bay head setting to a wave influenced open coast setting the cessation of the sea level rise at 6 cal kyr bp may have played only a small role in the change of river mouth morphology because the progradation rate decelerated from 22 to 4 m yr instead of accelerating at that time the river mouth morphodynamic change from straight to lobate was largely caused by an increase in the song hong sediment discharge from 17 27 9 2 cal kyr bp to 49 million t yr 2 0 cal kyr bp as a result of anthropogenic deforestation along the upper reaches of the song hong